Rittal Enclosure and process cooling

8/20/2019 Rittal Enclosure and process cooling

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Enclosure and process

cooling

The Rittaltechnologylibrary20132


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Enclosure andprocess cooling


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Until his retirement, engineer Heinrich Styppa was a divisionaldirector at Rittal in Herborn with international responsibility forenclosure climate control and process cooling. He inspiredand initiated many product innovations in this field, leading forexample to the market launch of ProOzon CFC-free coolingunits and microprocessor technology, air/water heat exchang-ers, nano-technology and energy-efficient enclosure coolingunits. In many professional publications and books andnumerous presentations to associations and customers,Heinrich Styppa has described innovative ways of dissipating

heat from enclosures and production machinery.

Mr. Styppa received extensive support from Ralf Schneider, Director InternationalBusiness Development Climatisation, Rittal GmbH & Co. KG.

The Rittal technology library, volume 2

Published by Rittal GmbH & Co. KGHerborn, September 2013

All rights reserved.No duplication or distribution without ourexplicit consent.

The publisher and authors have taken theutmost care in the preparation of all text andvisual content. However, we cannot be heldliable for the correctness, completeness andup-to-dateness of the content. Under nocircumstances will the publisher and authors

accept any liability whatsoever for any director indirect damages resulting from the appli-cation of this information.

Copyright: © 2013 Rittal GmbH & Co. KGPrinted in Germany

Produced by:Rittal GmbH & Co. KGMartin Kandziora, Dagmar LiebegutPrinted by: Wilhelm BeckerGrafischer Betrieb e.K., Haiger

2 Enclosure and process cooling


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Preface

In view of escalating global environmental problems and rising energy

prices, energy effi ciency is a key issue for industrial production processeslooking ahead to the future.

The advanced technology of German machine tool manufacturers has anadded advantage – namely energy effi ciency.

The product benefits and features that distinguish them from internationalcompetitors include not only their precision, productivity, quality andsafety, but also their low energy consumption. The European Union has

already responded by including machine tools in the list of energy-usingproducts under the EUP directive.

Due to the increasingly powerful technology used in production processes,heat loss in enclosures has also increased rapidly.

With its highly effi cient climate control solutions, in which energy-effi ciencyis treated as a priority, Rittal has taken this trend on board and devel-oped climate control components and cooling systems with a continuous

increase in effi ciency of more than 40% compared with the old systems.Today – and not without good reason – Rittal is an international marketleader and above all a technology leader in the field of climate control sys-tems for enclosures, machines, server racks and data centres.

This book describes the possibilities of a future-oriented, energy-effi cientcooling system for enclosures and machinery.

Heinrich Styppa

Enclosure and process cooling 3


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The whole is more than thesum of its parts

The same is true of “Rittal – The System.” With this in mind,we have bundled our innovative enclosure, power distribution,

climate control and IT infrastructure products together into a singlesystem platform. Complemented by our extensive range of softwaretools and global service, we create unique added value for allindustrial applications: Production plant, test equipment, facil-ity management and data centres. In accordance with our simpleprinciple, “Faster – better – everywhere”, we are able to combineinnovative products and effi cient service to optimum effect.

Faster – with our “Rittal – The System.” range of modular solutions,which guarantees fast planning, assembly, conversion and commis-sioning with its system compatibility.

Better – by being quick to translate market trends into products.In this way, our innovative strength helps you to secure competitiveadvantages.

Everywhere – thanks to global networking across 150 locations.Rittal has over 60 subsidiaries, more than 250 service partnersand over 1,000 service engineers worldwide. For more than50 years, we have been on hand to offer advice, assistance andproduct solutions.



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nextlevelfor industry

With our Therm software and the innovative Therm App, calculatingthe climate control requirements of individual enclosure assembliesbecomes child's play. Meanwhile, the Rittal range of climate controlproducts has the right solution to suit every application.

Rittal – The System.

◾ Rittal – Therm◾ Rittal – Type-tested climate control systems



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Climate control from the smallestto the largest

◾ Cooling with ambient air◾ Cooling units

◾ Cooling with water◾ Heaters



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◾ Output – TÜV-tested for TopTherm cooling units◾ Environment-friendly – CFC-free refrigerants for over 20 years



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Your benefits

As a system supplier, Rittal is the world's leading provider of exceptionallyeffective yet energy-efficient and environmentally-friendly climate controlsolutions, precisely tailored to the customer's individual requirements.

Faster – Simple project planning with the Therm AppBetter – Efficient, energy-saving climate control technology, TÜV-testedEverywhere – Global spare parts service



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Order info Benefits

Catalogue◾ Product information

◾ Order information

Technical System Catalogue◾ Benefits

◾ Arguments◾ Advantages◾ System info

Print ◾ –

CD ◾ –

www.rittal.com ◾ ◾



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Info structure

Technology Background

Technical details◾ Technical drawings

◾ Performance diagrams

The technology library ◾ Background information

– ◾

– –

◾ –



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Fundamental principlesWhy do we need enclosures? ...................................................................... 18Why must heat be dissipated from an enclosure? ........................................ 20Types of heat dissipation ............................................................................... 21Physical calculation principles of heat dissipation ........................................ 23Why do enclosures need heaters? ................................................................. 28

Active heat dissipationHeat dissipation through forced air circulation .............................................. 32Heat dissipation through fan-and-filter units .................................................. 33Heat dissipation with air/air heat exchangers ................................................ 37Heat dissipation with thermoelectric cooling ................................................. 40Heat dissipation with air/water heat exchangers ........................................... 42Direct water cooling ..................................................................................... 50

Active climate control with enclosure cooling units ...................................... 53

General overview ............................................................................................ 61Design and calculation of climate control solutions using Therm software ... 62

Tips for project planning and operationUseful and important tips for project planning and operation........................ 66Maintenance .................................................................................................. 71

What is machine and process cooling?The necessity of machine and process cooling ............................................ 76

Index ............................................................................................................ 90Glossary ...................................................................................................... 91Bibliography ................................................................................................. 92

Note: IT Cooling (Climate Control) publication date March 2014

Content



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Fundamental principles

Why do we need enclosures? ............................................ 18

Why must heat be dissipated from an enclosure? ........... 20

Types of heat dissipation ................................................... 21◾ Enclosure surface cooling ......................................................................... 21◾ Air flow cooling .......................................................................................... 22

Physical calculation principles of heat dissipation ......... 23

Why do enclosures need heaters? ..................................... 28


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■ Why do we need enclosures?

The main function of an enclosure is to protect electronic components anddevices from aggressive media such as humidity, water, oil-contaminated

ambient air, corrosive vapours and also dust in the ambient air.

If these are not prevented, electroniccomponents will inevitably fail, eventu-ally leading to the shut-down of entireproduction systems. The failure of aproduction system generates coststhat can add up to huge sums.

It is therefore the job of a housing or

enclosure to provide lasting protectionof sensitive and expensive electronicand microelectronic components.

There are different protection catego-ries relating to the ambient conditions,which depend on the installation loca-tion of the enclosure.

The protection categories are defi nedon the basis of IP codes or NEMAtype ratings.

The abbreviation IP stands for IngressProtection. The protection categoryis defi ned by means of codes consist-ing of two letters, which always remain

the same, and two numerals. The relevant standard for enclosureconstruction or control system designis IEC 60 529 (VDE 0470-1).

IP classification, degrees of protection against foreign objectsand accidental contact

1st numeral Meaning

IEC 60 529 Protected against foreignobjectsProtected against accidentalcontact

0 Non-protected Non-protected

1

Protected against solid foreign

objects with a diameter of50 mm and greater

Protected against access with

back of hand

2Protected against solid foreignobjects with a diameter of12.5 mm and greater

Protected against access withfi nger

3Protected against solid foreignobjects with a diameter of2.5 mm and greater

Protected against access witha tool

4

Protected against solid foreign

objects with a diameter of1 mm and greater

Protected against access witha wire

5 Protected against dust inharmful quantitiesFully protected against ac-cidental contact

6 Dust-tight Fully protected against ac-cidental contact


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IP classification, degrees of protection against water

2nd numeral Meaning

IEC 60 529 Protection from water

0 Non-protected1 Protected against vertically falling water drops

2 Protected against vertically falling water drops when theenclosure is tilted up to 15°

3 Protected against water sprayed at an angle of up to 60º to thevertical

4 Protected against water splashed from any direction

5 Protected against water jets sprayed from any direction

6 Protected against powerful water jets7 Protected against the effects of temporary immersion

8 Protected against the effects of continuous immersion

NEMA stands for the National Elec-trical Manufacturers Association.

High levels of protection are requirednowadays for modern enclosures,

therefore the enclosures must berelatively impermeable. This meansthat infl uences from the environment

cannot penetrate the enclosure, butalso that the heat loss caused by theelectronic components cannot bedissipated to the outside.

NEMA classification

Type ratings

1 Enclosures constructed for indoor use protected against falling dirt

4Enclosures constructed for indoor or outdoor use protected againstwindblown dust and rain, splashing water and sprayed water; alsoprotected against external formation of ice on the enclosure

4X Enclosures constructed for indoor or outdoor use protected againstwindblown dust and rain, splashing water, sprayed water and corrosion;also protected against external formation of ice on the enclosure

12Enclosures constructed for indoor use protected against falling dirt,circulating dust and dripping, non-corrosive liquids


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■ Why does heat have to be dissipated froman enclosure?

In addition to negative external infl uences such as oil-contaminated and humidambient air and dust, heat is the number one enemy of today's high-perfor-mance electronic and microelectronic components in enclosures.

Relative to each individual component,the heat loss of electronic compo-nents has diminished signifi cantlyin recent years. At the same time,however, the packing density insideenclosures has increased dramatically,

resulting in a 50 – 60% increase inheat loss in the enclosures.

With the advent of microelectron-ics and new electronic components,the requirements for professionalenclosure construction have changedand thus also the requirements forheat dissipation from enclosures andelectronic housings.

Modern enclosure climate controlsystems must take these new circum-stances into account, offering the best

technical solution whilst guaranteeingoptimum energy effi ciency.

As already mentioned, heat is themain reason for failure of electroniccomponents inside the enclosure.

The service life of these compo-nents is halved and the failure rate isdoubled in the event of a temperatureincrease of 10 K relative to the maxi-mum permitted operating temperature(see Arrhenius equation).

5 K 10 K 20 K-10 K -5 K 0 K 15 K 25 K 30 K0 %

40 %

20 %

60 %

80 %

100 %

120 % 9.00

8.00

7.00

6.00

5.00

4.00

3.00

2.00

1.00

0.00

Arrhenius equation

Temperature change in Kelvin

S e r v i c e l i f e

F a i l u r e r a t e

1

Nominal load1


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■ Types of heat dissipation

Trouble-free operation and functioning of production lines is very heavilydependent on how the heat generated by electrical and electronic components

is dissipated from the enclosure to the outside.

We distinguish three different types/ methods of heat transfer:

◾ Thermal conduction◾ Convection ◾ Thermal radiation

In the case of enclosures andelectronic housings, we are mainlyconcerned with thermal conductionand convection. With thermal radia-tion, heat is passed from one body toanother in the form of radiation energy,without a medium material, and playsa minor role here.

Whether we are dealing with heatconduction or convection dependson whether the enclosure is open (air-permeable) or closed (air-tight). Withan open enclosure, the heat (heat loss)can be dissipated from the enclosureby means of air circulation, i.e. thermalconduction, from inside to outside. Ifthe enclosure has to remain closed,the heat can only be dissipated via theenclosure walls, i.e. through convec-tion.

Cooling via enclosure walls, i.e. from inside to outsidewith a positive temperature difference Ti > Tu

Method:– Cooling via enclosure surface

Protection category:– Up to IP 68

Max. cooling output:

– 350 watts Advantages:– No additional costs– High protection category

Disadvantages:– Hotspots may occur in the

enclosure


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Cooling by means of air circulation, i.e. thermal conduc-tion, from inside to outside with a positive temperaturedifference Ti > Tu

Method:– Cooling by convection


Max. cooling output:– 500 watts

Advantages:

– No additional costsDisadvantages:– No high protection category– Hotspots may occur in the

enclosure

What type of heat transfer is pos-sible depends not only on whetheran enclosure is open or closed, but

above all on the maximum ambienttemperature at the enclosure locationand the maximum temperature insidethe enclosure.Whether natural convection is suf-fi cient to dissipate the heat loss (v)from the closed enclosure via the wallsto the outside depends on the ambi-ent temperature (Tu) and the maximumpermitted internal temperature (Ti)

inside the enclosure. The maximumtemperature increase relative to theenvironment inside the enclosure canbe determined from the followingequation:

(Ti – Tu) =v

k · A

where k is the heat transfer coeffi cient

(for sheet steel k = 5.5 W/m2

K) and A (m2) is the enclosure surface area,determined according to DIN 57 660part 500.

Example calculation:Calculated heat loss in the enclosurev = 400 watts

Enclosure surface area(W x H x D 600 x 2000 x 600 mm)

A = 5.16 m²; Tu = 22°C

(Ti – Tu) =400

> 22 – 14 = 8°K 5.5 · 5.16

Result: The enclosure internal temperature (Ti)with heat loss of 400 W and surfacearea of 5.16 m² at an ambient tem-perature of +22°C will rise to approx.+30°C.

Conclusion:Based on the above parameters, thisheat loss can be dissipated to the out-

side via the surface of the enclosure. This involves passive heat dissipationfrom the enclosure, since no fans orother climate control components areused.


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■ Physical calculation principles of heatdissipation

To determine the necessary climate control solution for an enclosure, it isnecessary to calculate the heat loss v in the enclosure. The followingparameters must also be calculated:

Parameter

V Heat loss installed in the enclosure [W]

S Thermal radiation via enclosure surface [W] S = k · A · ΔT

K Required useful cooling output [W]

ΔT Temperature difference between inside and outside temperature [K] ΔT = (Ti – Tu)

e Required cooling output [W]e = v – s

V Required volumetric fl ow of a fan-and-fi lter unit [m3 /h]

Approximate calculation: V =3.1 · v

ΔT

1

5

2

6

Tu Maximum ambient tem-perature

Ti Maximum enclosureinternal temperature

A Effective enclosure

surface area (VDE)k Heat transfer coeffi cient

v Heat loss

s Thermal radiation viaenclosure surface

IP XX Protection category

Installation method, see

page 24

1

2

3

4

5

6

3 4


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The maximum enclosure internaltemperature (Ti) must be determineddepending on the electrical andelectronic components used in theenclosure.

According to IEC 60 204-1 “Safety ofMachinery”, the electrical equipmentof machines must be able to functioncorrectly at the envisaged ambient airtemperature. The minimum require-ment is correct operation at ambienttemperatures of between +5°C and+40°C. As far as the recommended

enclosure internal temperature isconcerned, an average value of +35°Chas become the norm. This internaltemperature also forms the basis forall calculations for necessary climate

control solutions in enclosures.In addition to the physical values de-scribed above, the enclosure surfacearea must also be determined accord-ing to the installation type.

The corresponding requirements foreach installation type are laid down inDIN VDE 0660 part 500/IEC 890.

Enclosure installation type according to IEC 60 890

Single enclosure, free-standing on all sides A = 1.8 · H · (W + D) + 1.4 · W · D

Single enclosure for wall mounting A = 1.4 · W · (H + D) + 1.8 · H · D

First or last enclosure in a suite, free-standing A = 1.4 · D · (W + H) + 1.8 · W · H

First or last enclosure in a suite, for wall mounting A = 1.4 · H · (W + D) + 1.4 · W · D

Enclosure within a suite, free-standing A = 1.8 · W · H + 1.4 · W · D + H · D

Enclosure within a suite, for wall mounting A = 1.4 · W · (H + D) + H · D

Enclosure within a suite, for wall mounting, covered roof surfaces

A = 1.4 · W · H + 0.7 · W · D + H · D

A = Effective enclosure surface area [m2]W = Enclosure width [m]H = Enclosure height [m]D = Enclosure depth [m]

The radiating power from the en-closure to the environment or theirradiating power from the environment

into the enclosure depends on theenclosure installation method.

An enclosure that is free-standing onall sides can dissipate a greater heatloss to the environment via its surface

(with a positive temperature difference, Ti > Tu between internal and externaltemperature) than an enclosure sitedin a niche or integrated into a machine.


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Effective enclosure surface area [m2 ] (VDE 0660 part 507)

The method of installation of the enclosure changes the effective surface area.

Singleenclosure, free-standing on allsides

Single enclosurefor wall mount-ing

First or lastenclosure ina suite, free-standing

First or lastenclosure in asuite, for wallmounting

Enclosurewithin a suite,free-standing

Enclosurewithin a suite,for wall mount-ing

Enclosure withina suite, for wallmounting, withcovered roof

surfaces


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Exclusion criteria

Based on the ratio of the ambient temperature (Tu) to the required enclosureinternal temperature (Ti), it is possible to establish in advance which climatecontrol method should be used.

Passive climate control

Natural convection Ti > Tu

Active climate control

Air circulation Ti > Tu

Fan-and-fi lter units and outlet fi lters Ti > Tu

Air/air heat exchangers Ti > Tu

Air/water heat exchangers Ti < Tu

Recooling / cold-water systems Ti < Tu

Enclosure cooling units Ti < Tu

The following table should helpprovide an overview of which typeof climate control solution can be

used and when, taking into accountthe protection category and coolingoutput.

For a detailed explanation of activeclimate control methods,see from page 31.

Overview of cooling methods according to protection category andcooling output

Method Protection

category

Cooling

outputPage

Cooling via fans IP 20 8000 W 33

Cooling by convection IP 21 500 W 32

Thermoelectric cooler IP 54 1000 W 40

Air/air heat exchangers IP 54 1000 W 37

Compressor-based climate control units IP 54 10000 W 53

Fan-and-fi lter units Up to IP 54/IP 55 2000 W 33

Air/water heat exchangers IP 55 10000 W 42Cooling via enclosure surface Up to IP 68 250 W 21

Cooling by forced air circulation Up to IP 68 350 W 32

Water-cooled mounting plate Up to IP 68 3000 W 50


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■ Why do enclosures need heaters?

The reliability of electrical and electron-ic components in an enclosure can be

put at risk not only by excessively hightemperatures, but also by excessivelylow ones. The enclosure interior mustbe heated, particularly to preventmoisture and protect against frost. Itis also necessary to prevent a conden-sate fi lm forming on the components.

The latest generation of enclosureheaters has been developed with the

help of extensive CFD (ComputationalFluid Dynamics) analyses. The posi-tioning of the heater is of fundamentalimportance for even temperature

distribution inside the enclosure.Placement of the heater in the fl oor

area of the enclosure is recommendedin order to achieve an optimumdistribution of temperature and henceeffi ciency.

Due to PTC technology, power con-sumption is reduced at the maximumheater surface temperature. Togetherwith a thermostat, this results indemand-oriented, energy-saving

heating. The necessary thermal outputdepends on the ambient temperatureand the actual enclosure surface areaaccording to VDE 0660 part 507.

25.0000

Temperature °C

22.5000

20.0000

17.5000

15.0000

12.5000

10.0000

7.50000

5.00000

After 15 minutes After 30 minutes

Start After 5 minutes


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Example:Free-standing enclosureW x H x D = 600 · 2000 · 500 mm

Lowest ambient temperature Tu = –5°C

Lowest enclosure internal temperature Ti = +10°C

The necessary thermal output Qs iscalculated using the known equationfor irradiation = A · k · (T i – Tu)

k = heat transfer coeffi cient5.5 W/m²K

A = 4.38 m²

h = 4.38 m² · 5.5 W/m² K (+10 + 5)> 361 watts

Result: A heater with a thermal output of atleast 361 watts must be chosen.

Observe the following points wheninstalling enclosure heaters:

◾ Install in the fl oor area as close aspossible to the centre

◾ Distance from fl oor panel> 100 mm

◾ Place heaters below the compo-nents to be protected

◾ Distance from side panels> 50 mm

◾ Distance from thermoplasticmaterials > 35 mm

◾ In case of excessive air humidity, ahygrostat should be used to achieveaccurate temperature control


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Active heat dissipation

Heat dissipation through forced air circulation ................ 32

Heat dissipation through fan-and-filter units ................... 33◾ Calculation of volumetric flow of a fan relative to the installation height ....... 35

Heat dissipation with air/air heat exchangers .................. 37

Heat dissipation with thermoelectric cooling ................... 40

Heat dissipation with air/water heat exchangers ............. 42◾ Benefits of water cooling ........................................................................... 44◾ Effi ciency comparison, cooling units – chillers with heat exchangers ...... 46

◾ Dissipation of high heat losses (cooling outputs > 10 kW) ...................... 48

Direct water cooling ............................................................ 50

Active climate control with enclosure cooling units ....... 53◾ Cooling unit technology ............................................................................ 54◾ Why use electrical condensate evaporation? ............................................ 59

General overview ................................................................. 61

Design and calculation of climate control solutionsusing Therm software ......................................................... 62


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■ Heat dissipation through forced air circulationTi > Tu

(positive temperature difference between internal and external temperature)

To improve convection, i.e. heat dissipation, by the enclosure walls from theinside to the outside, circulation fans are used. These fans circulate the air insidethe enclosure and should result in better heat distribution inside the enclosureand by the enclosure walls.

Method:– Cooling by forced air circulation



Advantages:– No hotspots thanks to air circula-

tion

Disadvantages:

– Only limited cooling power

The volumetric air fl ow that such a fanmust generate is determined using thefollowing equation:

V =f · v

Ti – Tu

V = air fl ow rate

f = air constant, see tableon page 35v = installed heat loss (thermal output

of the assembly) Ti = permitted temperature at the as-

sembly Tu = aspirated air

However, the result of such a solutionis very limited.

Note:

Consider the installation type, seepage 24/25.


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■ Heat dissipation through fan-and-filter unitsTi > Tu

There is usually some uncertainty when determining the heat loss in the enclo-sure. Nowadays, almost all manufacturers of electronic and electrical compo-nents provide this information for planners in equipment lists and documentation.

In most cases, the necessary constantenclosure internal temperature of 35°Cmentioned above cannot be achievedthrough convection alone.

The simplest solution is to usefan-and-filter units.

Method:– Fan-and-fi lter units

Protection category:– Up to IP 54/IP 55


Advantages:

– Low-cost and simple coolingmethod

Disadvantages:– Maintenance required in case

of dirty air – fi lters have to bechanged


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Innovative fan-and-fi lter units (withdiagonal fan technology) with theirnovel design provide uniformly con-stant air throughput with optimised airrouting and very low mounting depth,

leaving more space in the enclosurecompared with conventional axialfan-and-fi lter units.

Ti > Tu ◾ Fan-and-fi lter unit/outlet fi lter

combination ◾ Volumetric air fl ow 20 – 900 m3 /h

◾ Operating voltages: 230 V, 115 V,50/60 Hz, 24 V (DC), 48 V (DC)◾ Protection category IP 54

(optionally IP 56)◾ All variants also available as

EMC versions

Depending on the requirements, thesefan-and-fi lter units can be arranged“blowing” into the enclosure or “suck-

ing” out of the enclosure. However, itis recommended to install fan-and-fi lter units so that they blow, to avoidcreating a vacuum in the enclosure. Ifthere is a vacuum, the supply air fl owsuncontrollably into the enclosure, i.e.it is not only aspirated through the

fi lter, but is also sucked through allcable passages and other places thatare not airtight. Infl owing, unfi lteredambient air containing dust can leadto problems.

With a blowing arrangement, air isselectively routed into the enclosureand an uncontrolled infl ow of ambientair is prevented.

Use of diagonal fans withfan-and-filter units◾ Air throughput range:

20 – 900 m3 /h

◾ Operating voltage: 230 V, 115 V,400 V, 3~, 50/60 Hz, 24 V (DC)

1st advantage:Much greater pressure stability result-ing in a more constant air fl ow in theinstalled state, even with a contami-nated fi lter mat

2nd advantage: Air fl ow is expelled diagonally fromthe fan, promoting a more even airdistribution in the enclosure

Diagonal air flow = more even temperature distribu-tion in the enclosure


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Proven mounting system on the enclosure

Calculation of volumetricflow of a fan relative to theinstallation height

The necessary air fl ow of a fan-and-fi lter unit is determined from the heatloss v and the difference betweenthe maximum permitted internal and

external temperature (Ti – Tu). V =

f · v Ti – Tu

Factor f = cp · ρ (specifi c thermalcapacity x air density at sea level)

2

3

1

– Screwless spring terminal for tool-free electrical connection

– Bayonet catch for tool-free reversalof airfl ow direction

– Bayonet catch for tool-free chang-ing of the electrical connectiondirection (4 x 90°)

Height (m) cp (kJ/kg · K) kg/m³ f (m³/k)/Wh

0 0.9480 1.225 3.1

500 0.9348 1.167 3.31000 0.9250 1.112 3.5

1500 0.8954 1.058 3.8

2000 0.8728 1.006 4.1

2500 0.8551 0.9568 4.4

3000 0.8302 0.9091 4.8

3500 0.8065 0.8633 5.2

The specifi c thermal capacity of airand the air density depend on sev-eral factors, such as temperature, airhumidity and air pressure. The meanvalues of these factors vary dependingon the altitude above sea level.

The mean values at different altitudescan be determined from the abovetable.

1

2

3


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Using a selection diagram, you canselect a fan-and-fi lter unit quickly andeasily, provided the heat loss v andthe temperature difference (Ti – Tu) aredefi ned.

Example:Heat loss v = 600 watts

Temperature difference: Ti – Tu = 35 – 25 = 10 K

Result:Necessary air fl ow rate based on theselection diagram approx. 180 m³/h.

It is recommended to choose a fan-and-fi lter unit with an air fl ow approx.20% greater than the result of thecalculation, i.e. in this example approx.220 m3 /h. This allows for fouling of the

fi lter mat, depending on the level ofcontamination of the ambient air.

Selection diagram

V.

QV.

100

200

300

400

500

600

700

900

800

1000

1500

2000

3000

2500

∆ T 3 5 K

∆ T 4 0 K

∆ T 3 0 K

∆ T 2 0 K

∆ T 1 5 K

∆ T 1 0 K

∆ T 5 K

∆ T 2 5 K

30 50

70 90

300

500 700

10 20 40 60 80 100 200 400 600 800

= volumetric flow (m³/h)v = heat loss (W)


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■ Heat dissipation with air/air heat exchangersTi > Tu

If a protection category of IP 54 must be observed for an enclosure and thereis a positive temperature difference between the ambient air and the enclosureinternal temperature (Ti > Tu), air/air heat exchangers can be used. The greaterthe temperature difference between the internal and external temperature, themore heat loss can be dissipated outwards from the enclosure.

Method:– Air/air heat exchangers

Protection category:

– Up to IP 54Max. cooling output:– 1000 watts

Advantages:– Relatively low-maintenance

compared with fan-and-fi lter units

Disadvantages:– Effi ciency is lower than with

fan-and-fi lter units

The operating principle is simple butvery effective. The warm enclosureinternal air is aspirated by a fan in theupper area and led through a cross-fl ow heat exchanger. The cooler ambi-ent air is likewise aspirated by a fanand also led through this cross-fl ow

heat exchanger, without the two airfl ows being mixed.

The cooler air fl ow from the ambientair fl ow cools the heat exchanger anddissipates the heat loss absorbed bythe heat exchanger to the environ-ment. Inside the enclosure, the internalair is cooled in the heat exchanger andled into the lower enclosure.


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Air/air heat exchangers

Functional characteristics

External mounting

The rule is: The greater the tempera-ture difference between the externaltemperature (e.g. +22°C) and therequired enclosure internal tempera-ture (e.g. +35°C), the more heat losscan be dissipated via the air/air heatexchanger.

Product characteristics

◾ Separate internal and external circuit ◾ Output 17.5 to approx. 100 W/K ◾ High protection category guar-anteed (e.g. against dust, oil andmoisture)

◾ Internal circuit protection cat. IP 54 ◾ External circuit protection cat. IP 34 ◾ Less maintenance due to separatecontrol of internal and external fan

◾ Easy to clean thanks to removablecassette ◾ Control with digital temperaturedisplay

◾ Floating fault signal contact in caseof overtemperature

Internal mounting

Depending on the available space andrequirements, air/air heat exchangerscan be mounted on the enclosure orinstalled inside the enclosure.


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Example:– Free-standing enclosure

Width = 600 mm, height =2000 mm, depth = 500 mm

– Heat loss v = 900 watts

– Ambient temperature Tu = 25°C– Enclosure internal temperature Ti = 35°C

Step 1Calculate radiation power from theenclosure to the outside via the enclo-sure surface.

s = k · A · (T i – Tu)

Step 2Calculate enclosure surface area

A (m2) according to VDE 0660part 500 based on the formula

A = 1.8 · H · (W + D) + 1.4 · W · D

A = 1.8 · 2.0 · (0.6 + 0.5) + 1.4 ·0.6 · 0.5

A = 4.38 m²

s = 5.5 · 4.38 · 10 = 242 watts = radiation power

e = v – s = 900 W – 242 W= 658 watts = heat loss that must still be

dissipated via the air/air heatexchanger

A heat exchanger is therefore neededwith a specifi c thermal output of65.8 W/K .

The capacity of the air/air heatexchanger can be determined moreeasily using the selection diagram.

Air/air heat exchanger selection diagram

qw

∆T

A

5 010152025

30

40

50

6070

10 30 50 70

0

2

4

6

8

10

12

3000 2000 1000 0 20 40 60 80

QV.

ΔT = temperature difference (K)

v = heat loss (W)qw = specific thermal output (W/K) A = enclosure surface area according to VDE 0660 part 500 (m2)k = heat transfer coeffi cient (W/m2 K), for sheet steel k = 5.5 W/m2 K

Note:When using the selection dia-gram, heat radiation is not takeninto account; this allows the heatexchanger capacity reserve to bedetermined.


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■ Heat dissipation with thermoelectric coolingTi < Tu

Thermoelectric coolers are also known as Peltier coolers. The French physicistJean Charles Peltier discovered this “thermal effect” in 1834.

Thermoelectric cooling withPeltier cooling units

PrincipleIf a direct electric current fl owsthrough a conductor circuit made oftwo different metals, one contact point

cools down, while the other contactpoint heats up.

Peltier cooling has become moreimportant in recent years, above allbecause of the innovative thermoelec-tric cooler developed by Rittal.

A B

B

C

1 2

3

4 5

6

7

For use in small enclosures and oper-ating housings, where IP 54 protectionis required for the internal circuit,Peltier cooling is very often the correctand ideal technical solution.

With a very low weight of only 3.0 kg

and dimensions of 125 x 155 x400 mm (W x H x D), heat losses of100 watts are dissipated with minimalvibration and noise (no compressor).

Design of the Peltier element– Two different plates are connected

to one another so as to create a

series circuit.– The introduced DC current fl ows

through all plates one after theother.

– Depending on the current strengthand fl ow direction, the upper con-nection points cool down, while thelower ones heat up.

Operating principle of the thermo-electric cooler

– Air, warm, internal

– Air, warm, external

– Peltier element

– Air, cold, internal

– Air, cold, external

– Temperature T– Temperature profi le through the

components

1

2

3

4

5

6

7


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Method:– Thermoelectric cooling



Advantages:– Small dimensions– DC-capable– Additional heating function

possible

Disadvantages:

– Low effi ciency– High energy consumption

The technical advantages of theRittal thermoelectric cooler includeits modular design and low weight.Up to fi ve devices may be arrangedalongside each other and connectedin parallel, allowing synchronisedcontrol of the units in both cooling andheating operation.

The innovative design and air routingresult in the optimum air fl ow over thePeltier elements and hence a coeffi -cient of performance (COP) of 1.0, i.e.the unit consumes 100 W of electricalenergy to supply 100 W of cooling.

There are two variants of this unit,which accept either a 24 V DC powersupply or an AC power supply in therange 94 – 264 V.

Product characteristics◾ Modular capacity expansion ◾ Simple scalability ◾ Flexible mounting position:– horizontal– vertical– built-in– built-on

◾ Complete unit ready for connection


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■ Heat dissipation withair/water heat exchangers Ti < Tu

As well as enclosure cooling units, the use of air/water heat exchangers for thedissipation of heat from enclosures and electronic housings has undergone thegreatest development. This is partly due to the fact that the greatest coolingpower can be achieved in the smallest space with air/water heat exchangers.

Method:– Air/water heat exchanger


Max. cooling output:– 10,000 watts

Advantages:– High protection category– Reduced maintenance

Disadvantages:– High infrastructure requirements

The useful cooling output (Q) of an air/ water heat exchanger is determinedby the enclosure internal temperature,water inlet temperature and volumetricwater fl ow (l/h) in the heat exchanger.

With this solution a protection cat-egory of IP 55 is achieved, since theenclosure is completely closed. Theenclosure internal temperature can

even be cooled to below the ambi-ent temperature with air/water heatexchangers.

The enclosure internal air is cooled bythe circulation of air at the air/waterheat exchanger, whereby the heat lossfrom the enclosure is dissipated fromthe enclosure via the heat exchangerto the water and led to the outside.

This requires a water connection(supply and return) and a central ordecentralised cooling unit (recooler)

for water cooling on the air/water heatexchanger. These heat exchangersare available for mounting on walls,installation in walls or roof mounting,depending on the application.


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Product characteristics◾ Wide output range from 500 to

10,000 W ◾ Voltage:– 230 V

– 115 V– 400 V◾ Integrated control as standard

(Basic or Comfort)◾ Slimline design◾ Available with all water-carrying

parts made from CuAl or V4A(1.4571)

When calculating the air/water heat

exchanger it is important to rememberthat, depending on the ambienttemperature relative to the heat loss(v) in the enclosure, as well as thetemperature difference between theambient temperature (Tu) and the re-quired internal enclosure temperature(Ti), it may also be necessary to addthe thermal irradiation (s) via theenclosure surface.

e = v + s e = required cooling output

Example:– Calculated heat loss in the enclo-

sure v = 1500 watts– Calculated enclosure surface area

A = 4.38 m2 – Required enclosure internal tem-

perature Ti = 35°C– Ambient temperature Tu = 45°C

s = k · A · (Ti – Tu)= 5.5 · 4.38 · (45 – 35) = 241 watts

Result:Required cooling outpute = 1500 + 241 = 1741 watts

A suitable air/water heat exchangercan be selected from the performancediagram, based on the water inlet tem-perature, the volumetric water fl ow,the enclosure internal temperature andthe required cooling output.

Product characteristics◾ High protection category (e.g.against dust), IP 55 (IP 65 possible)

◾ Maximum ambient temperature (Tu)+70°C

◾ Cooling medium: Water

5

750

1000

1250

1500

1750

2000

2250

2500

2750

10 15 20 25 30 35

Ti

QK.

TW

VW = 400 l/h

VW = 200 l/h

VW = 100 l/h

.

.

.

4 5 ° C

2 5 ° C

3 5 ° C

Tw = water inlet temperature (°C)

v = useful cooling output (W) Ti = enclosure internal temperature (°C)


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Benefits of water cooling

Focus area:Enclosure cooling

In many large industrial enterprises, inthe automotive industry for example,a central supply of cooling water isusually already available. Since thiscooling water is provided by a centralring main, the air/water heat exchang-ers can also be supplied.

With a decentralised solution a chilleris used, in which case it is necessary

to ensure that as many air/water heatexchangers as possible are connectedto a cold water unit in the interests ofeconomy.

◾ Higher energy density than e.g. air;in the case of drive units a highercontinuous power is possible for thesame build volume

◾ Energy is easily transported e.g. outof the building


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◾ Compact design combined withdissipation of high thermal loads

◾ Good energy store, e.g. buffer storefor load peaks

◾ Cooling output is freely scalable:modular, open, building-blocksystems possible

A comparative calculation (see nextpage) shows that the use of severalair/water heat exchangers can be aneconomical but also energy-effi cientalternative compared with enclosurecooling units.


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Effi ciency comparison, cooling units – chillers with heatexchangers

Comparative calculation

Based on the example of a suite of enclosures with a heat loss of 25 kW

Result 1:By using a chiller and 16 air/water heatexchangers, approx. 40% less energy isconsumed.

1) Example calculation at 0.12 €/kW

Costs

Investment costs Energy consumption Total cost

16 cooling circuits,16 compressors

~18,000 € ~4,500 €1) ~22,500 €

How much energy is consumed?

TopTherm cooling unitsNumber

Power consumptionHeat loss

Per unit Total

Cooling unit for wall mounting 8 1.02 kW 8.16 kW

Cooling unit for wall mounting 8 0.58 kW 4.64 kW

Total 12.74 kW 25 kW


48/98



This example demonstrates that asolution with air/water heat exchang-ers and a central recooler (chiller)can alone reduce energy costs byaround 40%.

During the planning phase you areadvised to investigate both alternativesvery carefully from the point of view ofeconomy and energy effi ciency andobtain expert support where neces-

sary.

Result 2: Although the capital costs are greaterwhen using chillers and air/water heat ex-changers, these pay for themselves in lessthan one year through energy savings.

Costs

Investment costs Energy consumption Total cost

1 chiller,16 A/W HE,complete pipework

~19,000 € ~2,800 €1) ~21,600 €

How much energy is consumed?

TopTherm chiller with heat exchangerNumber

Power consumptionHeat loss

Per unit Total

Air/water heat exchanger 8 0.06 kW 0.48 kW

Air/water heat exchanger 8 0.16 kW 1.28 kW

Chiller 1 5.91 kW 5.91 kW

Total 7.68 kW 25 kW


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Dissipation of high heat losses(cooling outputs > 10 kW)

Air/water heat exchangers that can achieve a cooling output spectrum of over

10 kW are increasingly required in industrial applications. Based on very positiveexperience with IT cooling, Rittal has developed the high-performance IndustryLCP (Liquid Cooling Package) especially for use in industrial environments.

Air routing

The advantage of these heat exchang-ers lies not only in the fact that a highcooling output can be achieved, butalso that they can be fully and easilyintegrated into the Rittal TS 8 enclo-sure system.

The heat exchanger can be fl exiblyintegrated into the enclosure system.Depending on the required coolingoutput, air can be routed on one sideto the left, to the right or, if placedcentrally, on both sides.

Within an enclosuresuite, air routed onboth sides

Within an enclosuresuite, air routed onone side

At end of enclosuresuite, air routed onone side


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Curve

Here too, approx. 2000 l/h of coolingwater is required. In particular it isworth noting the high energy effi ciencyof such a central solution for coolingwhole suites of enclosures.

Advantage:◾ One central air/water heat ex-

changer, one fan, one control unitand maintenance/service on onlyone device

Disadvantage:◾ Failure of the heat exchanger brings

the whole system to a standstill

1400

1600

1200

1000

800

600

400

200

05 10 15 20 25 30 35

Tw

QK

.

2 5 ° C

3 5 ° C

4 5 ° C

Ti

V = 1000 l/h

V = 2000 l/h

–

1

–

2

–

3

–

4

–

5

–

6

– Internal temperature 45°C,fl ow rate 2000 l/h






1

2

3

4

5

6


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■ Direct water cooling

Another method of liquid cooling in a confi ned space involves direct cooling ofthe mounting plate with water. A prerequisite for the use of a water-cooled

mounting plate, besides a suitable climate-control and mechanical set-up, is thepresence of cooling water.

Method:– Water-cooled mounting plate


Max. cooling output:

– 3000 watts Advantages:– High protection category– No maintenance

Disadvantages:– Only 70% of the heat loss can be

dissipated, the remainder via otherclimate-control methods

– High infrastructure requirements

Water-cooled mounting plates areused in all areas of industry, from me-chanical engineering, to clean rooms,to medical technology.

Water-cooled mounting plates areused particularly where the heat lossof e.g. frequency converters, servo

controllers, motor chokes or powercontactors can be dissipated directlywith water. Water-cooled mountingplates also fulfi l the requirement fora high protection category (IP 68)and are suitable for use in hazardousareas.

By ensuring a constant componenttemperature, the water-cooled mount-ing plate helps extend the life of theseelements, while the even dissipationof heat directly at the source reducesenergy costs.


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Total flexibility of water-cooled mounting plate thanks to T-slotattachment system

The components are mounted directlyon the water-cooled mounting plate.

The routing of the water pipe in themounting plate is visually marked,

so the electrical components can bepositioned without diffi culty.

Complete flexibility in theenclosure ◾ Installation is carried out in thesame way as for partial mounting

plates◾ It can be fi tted on the rear panel orside panel

◾ Variable installation depth throughuse of punched sections withmounting fl anges

◾ Standardised plate sizes


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The capacity of a water-cooledmounting plate is defi ned on the basisof the thermal resistance Rth. The ther-mal resistance is calculated from thetemperature difference between the

surface of the water-cooled mountingplate and the coolant inlet tempera-ture, divided by the maximum heatloss of the components mounted onthis mounting plate.

Calculation formula –water-cooled mounting plate

Rth = Tp – Tm

Pv Rth = thermal resistance (K/kW)

Tp = surface temperature of water-cooled mounting plate (°C)

Tm = temperature of medium (°C)P V = applied heat loss (kW)

At the same time, the material usedhas an infl uence on the thermal resist-ance due to its thermal conductivityand thickness.

Example:– Heat loss v = 1500 W– Coolant temperature Tw = 25°C– Flow rate m = 300 l/h

Rth = Tp – Tw > Tp = Tw + v · Rth

v

The thermal resistance is fi rst deter-mined using the performance diagram.

At 300 l/h it is

Rth = 9.3 K/kW

Thermal resistance of water-cooled mounting plate

Thermal resistance Rth

R t h ( K / k W )

8.7

8.8

8.9

9.0

9.1

9.2

9.3

9.4

9.5

9.6

9.7

9.8

9.9

10.0

10.1

10.2

10.3

10.4

200 210 220 230 240 250 260 270 280 290 300 310 320 330 340 350 370 380 390 400360

l/h

Characteristic of a water-cooled mounting plate (499 x 399 mm) with copperpipeline

Result:

Tp =25°C + 1.5 kW · 9.3 K

= 38.95°CkW After rounding up, a temperatureof approx. 39°C is expected on thesurface of the mounting plate.

The special operating principle ofwater-cooled mounting plates requiresa technically complex infrastructure(recooler and pipelines). Their use istherefore confi ned to special projects.


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■ Active climate control with enclosure coolingunits Ti > Tu

The world's most widely used and most fl exible solution for the dissipation ofheat from enclosures and electronic cases is the enclosure cooling unit. Theenclosure internal temperature can be cooled to well below the ambienttemperature, e.g. Tu = +45°C, Ti = +35°C.

TopTherm cooling units

These work on the same principle

as a refrigerator. As in refrigerators,a refrigerant is used as the coolingmedium (type R134a for enclosurecooling units). The gaseous refriger-ant is compressed by a compressor,causing it to heat up. The refrigerantis led through refrigerant pipes toan outdoor air heat exchanger (con-denser). The heat of the refrigerant isdissipated to the ambient air (cooled).Due to this cooling, the refrigerant

liquefi es and fl ows via the fi lter dryer to

the expansion valve. Pressure reduc-tion takes place here. The refrigerantis depressurised and fl ows throughthe second indoor air heat exchangerlocated in the internal circuit. The heatloss from the enclosure is absorbed inthis heat exchanger. Due to heating,the refrigerant is gaseous once moreand is compressed by the coolingcompressor. The refrigeration cyclenow begins again.

Wall-mountedcooling units

Roof-mountedcooling units

Climate controlenclosure (doors)


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Cooling unit technology

Cooling circuit All enclosure cooling units have two com-pletely separate air circuits and complywith protection category IP 54 in theinternal circuit.

Extensive technical requirements are de-fi ned for enclosure cooling units intendedfor industrial use.

The operating limit for enclosure coolingunits is defi ned in DIN EN 14 511. In thecase of enclosure cooling units this isusually an ambient temperature of +55°C.

The design of an enclosure cooling unit,including the necessary components, isclearly and comprehensibly illustrated inthe diagram opposite.

The use of enclosure cooling units alwaysrequires extensive integration and adapta-tion to local circumstances. As the ma-chines and installations are now used all

over the world, the fl exibility requirementsof these cooling systems have increasedsignifi cantly in recent years.

– Internal temperature sensor

– Icing sensor

– External temperature sensor

– Condensation temperature sensor

B1

B2

B3

B4

The following questions and issuesmust be answered and dealt with atthe planning stage:– How high is the ambient tem-

perature Tu and humidity at theinstallation location?

– Condenser

– Air outlet approx. 85°C

– Hot fl uid Tu max. 55°C

1

2

3

–

11

–

10

–

9

External circuit

Internal circuit


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–

7

– What is the installation type accord-

ing to IEC 890?– What is the maximum permittedenclosure internal temperature Ti?

– What is the heat dissipation in theenclosure?

– What national and international

standards (DIN, UL, CSA etc.)must these enclosure coolingunits satisfy?

– What protection categoryis required?

– Filter dryer

– Expansion valve

– Cold fl uid(4 bar)

– Evaporator coil

– Enclosure airinlet approx.15°C

– Cold gas

– Compressor

– Hot gas (23 bar)

– Microcontrollerbox

– B4 Sensorsfor controlling viamicrocontroller

4

5

6

7

8

9

10

11

12

B1

–

B4

–

1

–

2–

3

–

4

–

5

–

6

–

12

–

8

–

B1

–

B3

–

B2


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The calculation of an enclosurecooling unit is described on thebasis of an example.

Heat loss in the enclosure

v = 2000 wattsEnclosure dimensions(W x H x D) = 600 x 2000 x 500 mm,free-standing

Ambient temperature Tu = 45°C

Required internal temperature Ti = 35°C

Step 1Calculate enclosure surface area ac-cording to VDE 0660 part 500:

A = 1.8 · H · (W + D) + 1.4 · W · D A =1.8 · 2.0 · (0.6 +0.5) + 1.4 · 0.6 · 0.5

A = 4.38 m²

Step 2Calculate irradiation from the environ-ment +45°C to the interior +35°C(Ti < Tu)s = k · A · (T i – Tu)

s = 5.5 · 4.38 · (45 – 35)s = 242 watts

e = v + s = 2000 + 242e = 2242 watts

This heat loss must be dissipated tothe outside via the enclosure coolingunit.

Step 3/ResultFor an ambient temperature of +45°Cand an enclosure internal temperatureof +35°C, a cooling unit with a coolingoutput of 2242 watts must be found.

Selection diagram

155 25 35 45 55 65 75

4000

3800

3400

3600

3200

3000

2800

2600

2400

2200

2000

1800

1600

12001400

800

1000

4200

4400

65

60

55

50

4045

30

35

A

c t u a l c o o l i n g o u t p u t o f c o o l i n g u n i t [ W ]

Ambient temperature °C

I n t e r n a l t e m

p e r a t u r e [ T i ] ° C


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From the two reference variablesof ambient temperature 45°C andenclosure internal temperature 35°C,one can determine the appropriatecooling unit (wall or roof-mounted)

from a cooling performance diagram.Rittal has developed the “Therm” calculation program to simplify thedesign and calculation of enclosurecooling units and other climate controlcomponents.

Enclosure dehumidification A very welcome side-effect of usingenclosure cooling units is that they

also dehumidify the interior of the en-closure. As the air inside the enclosurecools down, part of the moisture in theair condenses in the enclosure on theinternal heat exchanger (evaporator).

This water/condensate is safely ledfrom the enclosure to the outside viathe condensate drain.

How much condensate actually

occurs depends on the relative airhumidity, the air temperature and thevolume of the enclosure or electronichousing. The condensate quantity isalways directly related to the volume ofthe enclosure and can be calculatedfrom the cooling in the Mollier H-Xdiagram.

Example:

Ambient temperature/humidity35°C/70%

Temperature at the evaporator Tv = +18°C

Enclosure volume> V = W x H x D= 2 · 0.6 · 0.6 = 0.72 m³

Mollier H-X diagram

–

1

–

2

Pd = water vapour partial pressure (mbar) T = air temperature (°C)x = water content (g/kg dry air)

– Dewpoint range– Relative humidity 70%

1

2

Pd

T

x

50

45

40

35

30

25

20

15

10

5

0

–5

–10

–15

–20

0

50 10 15 20 25x2 x1

30 35 40

6030 45155 10 20 25 35 40 50 55

1 0 %

2 0 %

3 0 %

4 0 %

5 0 %

6 0 %

7 0 %

8 0 %

1 0 0 %

➀

9 0 %

Calculation of condensatequantity:W = V · ρ · ( X1 – X2)

= 0.72m³ · 1.2 kg/m³ · (24 – 13 g/kg)

In this example, a condensate quantity

W = 9.5 g – 9.5 ml occurs. This example shows that, dependingon the enclosure volume, only verysmall amounts of condensate areobtained upon dehumidifi cation ofthe enclosure. In practice, however,signifi cantly larger condensate quanti-ties may occur due to leaks in theenclosure (cable passages, open fl oor

panels or operation of the cooling unitwith the enclosure door open).


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Observe the following rules:◾ Enclosure cooling units should only

be operated with the door closed◾ Always use door limit switches

when using cooling units

◾ Seal the enclosure in accordancewith the required protection cat-egory IP 54

◾ If possible, to avoid excessive cool-ing in the enclosure, do not selectan enclosure internal temperaturebelow +35°C

◾ Condensate must be led safely tothe outside in accordance with theinstallation instructions

◾ Rittal “Blue e” cooling units have ac-tive electrical condensate evapora-tion

Energy effi ciency of enclosurecooling unitsModern enclosure cooling units offerusers the maximum fl exibility in useworldwide and integration into the in-frastructure of a machine, independentof the installation location.

“Blue e” cooling units were developedin light of the increased requirementsrelating to energy effi ciency.

These innovative “Blue e” coolingunits consume up to 70% lessenergy than cooling units that areapproximately 5 years old.

This has been achieved through theuse of the latest compressor andfan technology (EC fan motors). Theswitching cycles have also beensignifi cantly reduced. The use of nano-technology for the heat exchanger inthe external circuit, including an opti-mised operating point, not only savesenergy, it also signifi cantly increasesthe service life of the components.

Note:In practice, queries often arise con-cerning the estimation of heat loss inthe enclosure, e.g. where no heat lossdata is provided by the componentmanufacturers. As a rough estimate,the installed nominal power can beused, e.g. for a nominal power of40 kW, the heat loss is approx. 5%,i.e. approx. 2000 watts.

“Blue e” cooling units from Rittal The following measures have beentaken, tailored to the individual devicetypes, to make “Blue e” cooling units

more effi cient: ◾ Larger heat exchanger surfaces ◾ Use of EC fans ◾ Use of energy-effi cient compressors ◾ Performance-optimised condensateevaporation

◾ Eco-mode control


60/98



Why use electrical condensate evaporation?

From the automotive industry comes a requirement to avoid the risk of accidentsdue to puddle formation, but without having to install costly condensate drainagepipes. Therefore, cooling units with integrated electrical condensate evaporationhave been developed.

These use an effi cient PTC heatingcartridge with automatic adjustment

of thermal output depending on theamount of condensation. Approx.120 ml of condensate can be evapo-rated per hour. This ensures completeremoval of condensate.

Note:With larger amounts of condensation,

the condensate is drained out of theenclosure via a safety overfl ow.


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Better energy effi ciency thanks toRittal nano-coatingIn the total cost of ownership analysisfor an enclosure cooling unit over anobservation period of 5 years, the

energy and maintenance costs aloneaccount for approximately 60% ofthe total costs. Based on this fi nding,Rittal has looked for ways of reducingthese costs as far as possible. Thenano surface coating of the condenserin the external circuit of the coolingunit has proved the best way of furtherreducing maintenance and energycosts.

Advantages of Rittal nano-coating◾ Reduced deposits of industrial dirt

on the heat exchanger membranes ◾ Increased operational reliability ◾ Signifi cantly reduced service

intervals ◾ Reduced adhesion of dirt, henceeasier cleaning of heat exchangers

◾ Uniformly high thermalconductivity


62/98



■ General overview

Fast selection of all enclosure cooling options accordingto environmental conditions and required cooling output

Heat loss to bedissipated

ΔT = 10 K

Tenvironment in °C Air quality

<1500 W

>1500 W 20...55 20...70 >70

dust-free dusty

oil-contam-inated

corro-sive

Fan-and-

filter units ◾ (◾) ◾ ◾ ◾Fine fi lter mat(chopped fi bremat)

◾ ◾ ◾ ◾

Filter mat(chopped fi bremat)

◾ ◾ ◾ ◾

Air/air HE ◾ ◾ ◾ ◾

Air/water heat exchanger

Standard ◾ ◾ ◾ ◾ ◾ ◾ ◾ ◾ ◾

Stainless steelvariant ◾ ◾ ◾ ◾ ◾ ◾ ◾ ◾ ◾

Cooling unit

Standard ◾ ◾ ◾ ◾

Chemicalversion ◾ ◾ ◾ ◾

Filter mat

(open-celledPU foamedplastic)

◾ ◾ ◾ ◾

Metal fi lter ◾ ◾ ◾ ◾ ◾ ◾

RiNanocoating ◾ ◾ ◾ ◾ ◾ ◾


63/98



■ Design and calculation of climate controlsolutions using Therm software

Rittal fi rst made its Therm softwarefor calculating and selecting climatecontrol components available to cus-tomers as long ago as 1992. Today,software version 6.1 takes care of theentire laborious calculation process.

A simple user interface guides the userto the appropriate, correctly dimen-sioned climate control components.

All calculations are based on the

requirements of IEC/TR 60 890 AMD1/02.95 and DIN EN 14 511-2:2011.

Confi guration of all climate controlcomponents can be carried out withthis software, which includes a con-fi gurator for recooling systems.

Another advantage of this software isthe direct link to the EPLAN Cabinetplanning software. By placing thenecessary electrical components onthe mounting plate, the heat lossesare calculated and transmitted to the

Therm software, which eventuallycalculates and specifi es the correctclimate control components.

An important point is that these calcu-lations can be made available to theend customer as and when needed inthe form of detailed documentation.

This software saves the planner agreat deal of time and effort in design-ing the climate control solution.


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Therm climate control calculation using a Smartphone

For the project planning of your

optimum climate control solution in5 easy steps:

◾ Project title (reference line for e-mail) ◾ Parameters ◾ Enclosure ◾ Selection ◾ Recommendation

The Therm app for Android and iOS(iPhone) handles the time-consumingprocess of calculating climate controlrequirements for individual enclosureassemblies.

With its fast selection feature, the app

provides a compact variant of the fullsoftware version “Therm 6.2”. Theresult can be sent quickly and easilyas an e-mail. A user-friendly interfaceguides the operator to the most suit-able, correctly dimensioned climatecontrol component using the typicalsmartphone controls.

All evaluations are closely based on

the requirements of IEC/TR 60 890 AMD1/02.95 and DIN 3168 for enclo-sure cooling units.


65/98


66/98


Tips for project planning andoperation

Useful and important tips for project planningand operation ....................................................................... 66◾ Correct enclosure construction and heat dissipation ............................... 66◾ The external circuit – clear spaces ............................................................ 68

◾ Innovative air routing in the internal circuit ................................................ 69◾ Air duct system.......................................................................................... 69

Maintenance ....................................................................... 71◾ Use of filter mats ....................................................................................... 72◾ Outside air filter ......................................................................................... 73


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Useful tips for project planning

■ Useful and important tips for project planningand operation

In addition to the calculation and selection of solutions for the dissipation of heatfrom enclosures and electronic housings, the correct planning and arrangementof the equipment and resources is important. Devices and electrical componentsshould be installed in the enclosure in accordance with the instructions of therespective manufacturers and the information in the device manual.

The following points should beobserved regarding arrangementinside the enclosure:◾ The cooling air passing through the

components must fl ow from bottomto top ◾ There must be suffi cient space forair to fl ow between the parts andelectrical components

◾ Air intake openings of the climatecontrol components must not beobstructed by electrical devices,equipment or cable ducts

Correct enclosure construction and heat dissipation


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Electrical wires and cables are in-creasingly routed over the compo-nents. This inhibits the free dissipationof heat from these components to theambient air in the enclosure.

The wires have an insulating effect.Despite climate control, it becomesmore diffi cult or even impossibleto prevent components from over-heating.

Ventilation clearancesEspecially in the case of narrow components, the heat dissipation of the devicesis signifi cantly hindered if cables are laid on the ventilation grilles.

50 mm modules have4 rows with openings inthe ventilation grille

→ +10 K →50% service life andtwice the failure rate

→ +20 K →25% service life and fourtimes the failure rate

ΔT = 0 K

Project planning guide

ΔT = approx. +10 K

1 sensor cable

ΔT = approx. +20 K

2 sensor cables

Common practical errors Ventilation opening covered

Incorrect Correct


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The external circuit – clear spaces

◾ With all climate control solutions,care must be taken to ensure that

the air intake and air discharge ofthe climate control componentsthrough walls, machines or otherstructures is not hindered.

Note:In the case of roof-mounted cooling

units – regardless of the installationtype – one air outlet opening mustalways be kept free, because withthese devices air enters from the front.

The warm air is led away through theside panels, the back wall and,optionally, via the roof.

Air circulation inside the enclosure

◾ The air routing in the enclosure, tak-ing into account the air fl ow directionof electronic components with theirown blower or fan, must be consid-ered as early as the planning stage.When planning the climate controlsolution, it is important to avoid

routing the air against the air fl ow ofthe electronic components. Suchproblems are especially commonwith roof-mounted solutions. In thiscase, cooling units and air/water heatexchangers with air routing ducts of-fer the optimum technical solution.

Common practical errors Air intake opening misaligned

◾ Storage space for the necessarydocuments and circuit diagramsshould be taken into account asearly as the planning phase.


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Layout of electronic components in the enclosure

Especially where roof-mounted units are used, particular attention should bepaid to the air fl ow from blowers built into electronic components.

Correct Correct Incorrect

◾ Thanks to the air routing system,the supply air from the cooling unitor air/water heat exchanger can beselectively guided to the compo-nents without counteracting the airrouting of the installed equipment.

Air duct system ◾ Air short circuits must be avoided

through the use of air duct systems◾ Targeted supply of self-ventilatedcomponents with cold air

◾ The use of air duct systems isadvisable particularly in the case ofroof-mounted cooling units

Innovative air routing in the internal circuit


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◾ With all climate control solutions,the cold air should always be routedclose to drive units (see illustrationabove). This is where the greatestheat losses occur. This arrange-ment ensures that the cold supplyair from the climate control solutionoptimally cools the drive units with-

out losses.

◾ With the arrangement shown in theabove illustration, the enclosureis not optimally cooled. The driveunits or electronic devices in theright-hand enclosure do not receivethe necessary cooling. Therefore,despite thermal calculation, the heatlosses of the electrical components

cannot be dissipated.

◾ The internal temperature of theenclosure should always be set to+35°C. There is no technical justi-

fi cation for setting the temperatureany lower. If the temperature insidethe enclosure is lower than that,e.g. +15°C, condensation will besignifi cantly increased.

The parts and components will alsobecome sub-cooled and form con-densate after the cooling is switched

off or the enclosure door is opened.


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◾ With a chosen internal temperatureof e.g. +15°C, the cooling unithas only about 50% of the originaloutput specifi ed according to DINEN 14 511 (internal temperature =

+35°C).◾ If the installation requirements of theparts and electronic componentsare not observed, this will lead toa reduction in the service life andultimately the premature failure ofthe components.

◾ All over the world, climate controlcomponents are used mainly inindustrial environments, i.e. insurroundings affected by dirt, dustand oil. Nowadays, climate control

components are low-maintenance,but not maintenance-free. Only air/ water heat exchangers do not comeinto direct contact with the ambientair. To ensure long-lasting operationof these components and systems,they must be maintained accordingto a fi xed, systematic cycle.

■ Maintenance

◾ With fan-and-fi lter units, air/air heatexchangers and enclosure coolingunits, maintenance largely concernsthe external fi lters of the climatecontrol components.

◾ Do not allow fi lters to become so

clogged with dust and oil-contam-inated dirt that correct operation ofthe devices is no longer guaranteed.

◾ Use only fi lter mats recommendedby the manufacturer. Chopped fi bremat fi lters are not recommended forcooling units.


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Use of filter mats

In heavily dust-laden atmospheres, PUfi lters should be used and replaced ona regular basis. Cooling units with Ri-Nano coating do not need a dust fi lter.

In the textile industry, the use of lintfi lters is recommended.

If the air is oil-contaminated, use metalfi lters. These separate the oil conden-sate from the air and can be cleanedwith appropriate detergents.

Note:Chopped fi bre mat fi lters are not suit-able for cooling units.

◾ If the ambient air is contaminatedwith oil, metal fi lters should be used.

These can be cleaned and reused ifnecessary.

◾ Due to the nano-coating, Rittalcooling units do not need a sepa-rate fi lter for a dust-laden environ-ment.


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Outside air filter

Operation in a lint-laden environment (textile industry)

All these tips and instructions arebased on decades of practical experi-ence in the use of enclosure climatecontrol solutions in industrial environ-ments. By observing this information,the cooling of electrical components

can be optimised and the dissipationof heat from enclosures and electronichousings can be made more energy-effi cient.

◾ If lint is present in the ambient air,as in the textile industry for exam-ple, a lint fi lter should be used in theexternal circuit.


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Machine and process cooling

What is machine and process cooling? ........................... 76◾ Applications of recooling systems/chillers ................................................ 78◾ The modular recooler/chiller ...................................................................... 80

IT cooling

Recooling systems for IT climate control ........................ 81

Summary ............................................................................. 88


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■ What is machine and process cooling?

The operation of a high-performance machine tool with very high demands interms of processing accuracy and speed is no longer imaginable without

precision cooling.High-performance cooling requiresthe temperature at the workpieceand in the machine to be kept asconstant as possible. These coolingprocesses can only be realised withrecooling systems (chillers). According

to numerous studies, e.g. by AachenUniversity and Darmstadt University,the cooling of a machine tool aloneaccounts for around 15% of the totalenergy requirement of a modernmachine tool.

Water cooling of machine tool and enclosure


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Recooler applications

Energy-effi cient water cooling inthe production area

Focus area:Machine and process cooling

Great fl exibility, but above all the abilityto dissipate high heat loads from ma-chines and enclosures via water have

led to a sharp increase in the use ofrecooling systems in recent years. Dueto the use of recooling systems onmachines, a signifi cant trend towardsenclosure cooling with air/water heatexchangers is also apparent.


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Machine

Rittal Enclosure and process cooling

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