AAR - Selection of EC for EE Ammonia refrigeration

5/26/2020

AAR - Webinar - Date : 26.05.2020 1

Bhaskar Paddala

Area Sales Manger

BAC (Baltimore AirCoil Company)

Contact : +91 7506696586

Email : [email protected]

Selection of Evaporative Condenser for

Energy Efficient Refrigeration

Agenda

Introduction – Refrigeration Cycle

Types of Refrigeration Condensers

Condenser Selection & Effect on plant efficiency

Modern Evaporative Condenser - Technology

Water Quality & Condenser Maintenance

Q&A

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Basic Refrigeration Cycle Refrigeration System Components

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Methods of Condensing

Air cooled

Dependent on

ambient

(dry bulb)

temperature

Evaporative cooled

(Water + Air)

Evaporative cooling,

dependent on wet bulb

temperature

Water cooled

Water cooled systems

performance, dependent

on cooling water outlet

temperature

5

Shell & Tube

Condensers

Shell & Tube

Condensers

Atmospheric CondensersAtmospheric Condensers ConceptConcept

Plate type CondensersPlate type Condensers

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Types of Condensers

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• Performance NOT consistence as it is linked with the natural

air flow which varies throughout the day and from season to

season.

• Occupies large space, huge wastage of water due to drift

losses. Space can be commercialize by cold storage owners.

• To be located in area where free air flow is available.

• Refrigerant charge will be considerably high. Almost double to

evaporative condensers.

• Civil construction cost is hidden for the customer.

• Expansion of these type of condensers are difficult.

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Atmospheric Condensers

Pre

ssu

re

Heat Content

Subcooled

Liquid

Mixture of liquid and vapor

Superheated

Vapor

Effect of condensing pressure

Suction

Pressure

Discharge

Pressure

Greater RE less flash

gas

Lower Condensing can

reduce work done by

compressor


• Maximum Discharge

Pressure safety:

Compressor will react to high discharge

pressures:

Stop loading ~ 210 psig

Force unload ~ Based on Compressor

Amperage

Shut down ~ 230 psig

Note : Different plants will have difference

settings.

Compressor safeties

Maximum design CT

15.8 kg/cm2 g

14.06 kg/cm2 g

12.3 kg/cm2 g

10.54 kg/cm2 g

8.78 kg/cm2 g

17.57 kg/cm2 g

14.76 kg/cm2 g

16.17 kg/cm2 g


• Condensing Pressure :

System Design – SDT & WBT.

40 °C 14.8 kg/cm2 g ( 211 psig )

39°C 14.4 kg/cm2g ( 205 psig )

38 °C 13.9 kg/cm2g ( 198.5 psig )

37 °C 13.5 kg/cm2g ( 192.6 psig )

36 °C 13 kg/cm2 g ( 186.8 psig )

35 °C 12.7 kg/cm2 g ( 181 psig )

Case study - Required condenser Capacity

SI Units : • 2 Stage – Screw compressors – 3 No’s.

• SST – Minus 40° C

• SDT – 40° C

• Condenser Heat rejection Load :

• Compressor cooling load = 471 kW.

• Motor Bkw = 291 kW

• Total heat rejection =471+291= 762 kW + ** Safety Factor.

• For 3 Compressors = 762 X 3 Nos = 2286 kW.

• ** Based on manufacturer’s suggestion / plant designer suggestion.

Design considerations while selection

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Condenser Selection S&T :• Condensing temperature required (TC) : 40 ° C

• Cooling water inlet temperature (tci ) : 32 ° C

• Cooling water outlet temperature (tco ) : 36 ° C

• Heat rejection in kcal /Hour = kW X 860 = 2286 X 860 = 1965960 kcal/hr

• Calculate the condenser water flow rate using :

Heat rejection in kcal/hr

Flow rate(m3/Hr) =

3024 X Water temperature rise in ( ° C)


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Condenser Selection S&T :• Condensing temperature required (TC) : 40 ° C

• Cooling water inlet temperature (tci ) : 32 ° C

• Cooling water outlet temperature (tco ) : 36 ° C

• Heat rejection in kcal /Hour = kW X 860 = 2286 X 860 = 1965960 kcal/hr

Find out the heat transfer area as :

Heat rejection in kcal/hr

Area =

LMTD X U

U – Value varies from metal to metal. Customer to insist for heat transfer area

as per calculation with positive margin.


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Design parameters – SI Units : • Heat rejection either SI units

• Condensing temperature in ° C

• Wet bulb temperature in ° C of site location.

What is so great about Wet Bulb Temperature?• It is suggested to use a 0.4% day – not the hottest day ever recorded – just a

temperature that 99.6% of the time is safe.

• Total working hour= 24 X365 days = 8760 hour = 35 hour (0.4%)

• For Pune – The numbers from ASHRAE – 2017 are :


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Method of moving air through a Evaporative Condensers

How air and water mix - direction of air and direction of water

Principle of Operation Evaporative

Condenser

Induced Draft

Crossflow Counterflow

90° interaction of air and water 180° interaction of air and water

Air

Air

Air

Water Water Water

Pushes Air Pulls Air

Forced Draft

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Axial fansAxial fans

Centrifugal fansCentrifugal fans Radial fansRadial fans

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Principle of Operation Evaporative

Condenser

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• Combined flow

• Axial fan

• Induced draft

CONFIGURATION

Latest Evaporative Condenser Technology

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Combined flow technology in

Evaporative Condensers

Prime Surface

Coil

Evaporative Wet

Deck Surface

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Evaporation occurs primarily in wet deck

• Sensible heat transfer coil section

• Latent heat transfer 70 –80% of evaporation wet deck

• Minimizes scaling potential in the coil section

Combined Flow Technology

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134 TR X 3 Nos – Screw compressors running for butter deep freezer

10.2

21.6

32.7

46.5

54

0

10

20

30

40

50

60

70

4 0 ° C 3 9 ° C 3 8 ° C 3 7 ° C 3 6 ° C 3 5 ° C

Po

we

r S

av

ing

in

kW

h f

or

ea

ch d

eg

ree

red

uct

ion

in

co

nd

en

sin

g t

em

pe

ratu

re

Condensing temperature in °C

421 TR EVAPORATIVE CONDENSER AT DIFFERENT CONDENSING

TEMPERATURES, CONSTANT SST MINUS 40°C AND WBT 28°C.

Power savings ( kW ) vs Condensing

Temperature

Case Study of Dairy in Gujarat - Converted from PHE + Cooling

tower to Evaporative Condenser AAR - WEBINAR 2226-05-2020

6 Lacs

13 Lacs

19 Lacs

27 Lacs

32 Lacs

40 Deg C 39 Deg C 38 Deg C 37 Deg C 36 Deg C 35 Deg C

Cu

sto

me

r S

av

ing

s in

IN

R-L

ac f

or

ea

ch

de

gre

e

ch

an

ge

in C

on

de

nsi

ng

te

mp

era

ture

Condensing Temperatures in °C

463 TR Evaporative condensers at different SDT, constant SST

Minus 40°C and WBT 28°C.

Lower condensing temp means lower operating costs !

Customer Benefits

Considered 8 Rs/ kwh as power cost & 20 Hours a day operation of

Condenser through out the year

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Shield for your healthy

condenser sump

Combined Inlet Shields

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Reduced Refrigerant

Charge – Compared to

ATM Condenser

Combined heat transfer requires less

coil surface

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Suggested Fan/motors for each

unit to be minimum - 2

In case of failure of one motor at least some portion of plant can run.

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Water contains impurities

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Typical water analysis report

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Critical water chemistry elements

1. Total Dissolved Solids (TDS)– Ca, Mg, Na, iron,..

– measured by the Conductivity

2. Hardness (TH)– the amount of Ca & Mg ions dissolved in

water

– typical measure: Total Hardness

3. Alkalinity (TAC)– Carbonate (CO3) or Bicarbonate

(HCO3)

4. pH

5. Chlorides and Sulfates– Salts can be corrosive to metals at high

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Evaporative cooling

Evaporation –

pure waterWater drift loss

Water with added

minerals (concentrated

dissolved solids &

suspended particles)

Water bleed with

added minerals

Only water evaporates, not minerals26-05-2020

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Makeup = bleed + evaporation

Example:

Makeup water TDS = 500 mg/l

Cooling water TDS = 2500 mg/l

Cycles of concentration = 2500/500 = 5 cycles

Bleed ( B ) = E / ( N-1 )

What is cycles of concentration

Cycles of concentration(N) = TDS in recirculation spray water

TDS in the makeup water

Evaporation ( E ) = Total Heat rejection in kW/ 2322 = in l/s

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Impact of bleed on CoC

Constant evaporation

6

5

4

3

2

1

With zero bleed

Tim

e >

Solids build up

over time

6

5

4

3

2

Constant evaporation

With continuous bleed

maintaining set cycles

Tim

e >

Solids levels stay balanced

with proper bleed

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Impact of bleed on CoC

Cycles of concentration

Makeup

Water

Usage Good Balance between

water usage and scale

risk

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Water Treatment for Condenser

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• G235 Galvanized Steel : Low Cost / Higher Water Usage

• Special Hybrid Polymer Protection : Value for money / Less Water Usage

• Water Touched Stainless Steel: Medium Cost / Less Water Usage + High

protection to Chlorides

• Stainless Steel: High cost / Less Water Usage + Highest resistance

against Chlorides

• * Please follow guidelines of manufacturer suggestion.

Materials of Construction

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Climatic Data : 2017 ASHRAE HAND BOOK

FUNDAMENTALS.

Special thanks to Mr.Anil Gulanikar, Mr.Haresh

Rupchandani and Mr.Vaidyanatha Swamy for helping

with this presentation.

Courtesy :

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Q&A

[email protected]

[email protected]

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AAR - Selection of EC for EE Ammonia refrigeration

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