Introduction to Ammonia Refrigeration...

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Douglas Reindl, Ph.D., P.E.

ASHRAE Fellow

Director, IRC

Professor, University of Wisconsin-Madison

An Introduction to Ammonia Refrigeration Systems

ASHRAE is a Registered Provider with The American Institute of Architects

Continuing Education Systems. Credit earned on completion of this program will be reported to CES Records for AIA members. Certificates of

Completion for non-AIA members are available on request.

This program is registered with the AIA/CES for continuing professional education. As such, it does not include content that may be deemed or

construed to be an approval or endorsement by the AIA of any material of construction or any method or manner of handling, using, distributing, or dealing in any material or product. Questions related to specific materials,

methods, and services will be addressed at the conclusion of this presentation.

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will be delivered to you as submitted to GBCI.

However, any course found to be in violation of

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Course ID: 0090010881

COURSE TITLE

By Providers Name

Approved for:

x General CE hours

x LEED-specific hours

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Course description

Industrial refrigeration systems have used anhydrous ammonia for more than a sesquicentennial. Although ammonia has a long history of use in the industrial sector, the interest in ammonia as a potential refrigerant for non-industrial applications has grown recently.

This presentation will provide an overview of the ammonia refrigeration systems that have been the mainstay in the industrial sector and emphasize unique characteristics that differentiate ammonia systems from traditional halocarbon refrigeration systems. An emphasis will be placed on safety.

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Learning objectives

1. Identify key safety considerations when using ammonia as a refrigerant

2. Recognize materials used in halocarbon refrigeration systems that are not appropriate for use with ammonia due to material incompatibilities

3. Differentiate direct-expansion, gravity flooded, and liquid overfeed evaporator arrangements

4. Describe the difference between single stage and two stage compression systems

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During this presentation, we will discuss

Ammonia and its uses

Ammonia as a refrigerant

Ammonia refrigeration, the technology

Single stage: DX, flooded, overfeed

Two-stage

How is ammonia different compared to other refrigerants?

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Where is ammonia used?

87%

11%

2%**

Annual ammonia use in U.S.

Agriculture Other Refrigerant

Annual US consumption in 2012 was 14.4 million metric tons*.

Source: US Geological Survey (2013).

** Source: ASHRAE Position Document on ammonia (RA 2013)

NH3

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Anhydrous ammonia as a refrigerant

Where is ammonia used as a refrigerant?

Industrial systems: large cold storage and process systems

Some HVAC systems (requires a central plant)

Where no ODP and low/no GWP is desirable/needed

Distinct characteristics

Usually a custom engineered system vs. packaged systems for halocarbons

https://en.wikipedia.org/wiki/File:Ammonia-3D-balls-A.png

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Anhydrous ammonia characteristics

Refrigerant grade

99.95% Purity

75 PPM H2O (max)

Vapor tends to be lighter than air

Liquid specific gravity ~ 0.65

Alkaline pH of 11.6

Pungent odor makes it self-alarming

Highly soluble in water

Very corrosive to human tissue upon exposure!

Toxic at elevated concentrations

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Flammability characteristics

ASHRAE 34 flammability classification: 2L

DOT classified as non-flammable

Autoignition temperature: 1204F

Lower flammability limit (vol.%)1 15-16

Upper flammability limit (vol. %)1 25-28

Combustion products: oxides of nitrogen

Fire hazard: slight

1 IIAR Ammonia Data Book, (2009).

http://images.google.com/imgres?imgurl=http://z.about.com/d/chemistry/1/0/Y/a/ammonia.jpg&imgrefurl=http://chemistry.about.com/od/factsstructures/ig/Chemical-Structures---A/Ammonia.htm&h=599&w=712&sz=81&hl=en&start=16&um=1&usg=__LXUIXkYvy_vwzdVFzRSzGznDXXM=&tbnid=bCyVQYPq4D6buM:&tbnh=118&tbnw=140&prev=/images?q=ammonia&um=1&hl=en&safe=off&rls=com.microsoft:en-us:IE-SearchBox&rlz=1I7GZEZ

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Materials compatibility for ammonia

Not permitted

Copper and copper alloys such as brass are prohibited (but allowed for bearing materials)

Zinc (in continuous contact with ammonia)

Non-metallic materials that degrade upon exposure

Permitted

Carbon steel

Stainless steel

Aluminum

Other nonmetallic materials such as PTFE are permitted (if they will not break down)

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Why is ammonia widely used in food processing

and storage facilities?

Because it is a good refrigerant!

High heat transfer coefficients in equipment

Efficient compressor operation

Low refrigerant cost

No ozone depletion & no/low global warming impact

Sustainable

Self-alarming

Anhydrous ammonia

Lets now look at the technology

https://ixquick-proxy.com/do/spg/show_picture.pl?l=english&cat=pics&c=pf&q=ammonia&h=964&w=1100&th=140&tw=160&fn=Ammonia-elpot-transparent-3D-balls-B.png&fs=265.1 k&el=boss_pics_2&tu=http://ts1.explicit.bing.net/th?id%3DH.4799421008380232%26pid%3D15.1%26H%3D140%26W%3D160&rl=NONE&u=http://commons.wikimedia.org/wiki/File:Ammonia-elpot-transparent-3D-balls-B.png&udata=eb0cc7354d1cdeef748820907a153458&rid=LHLNSSPLTLNK&oiu=http://upload.wikimedia.org/wikipedia/commons/3/33/Ammonia-elpot-transparent-3D-balls-B.png

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Ammonia refrigeration technology

Single stage compression with evaporators configured as

direct-expansion

flooded

overfeed

Multi-stage compression systems

Cascade systems

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Simple vapor compression system

Qevap

Qcond

Wcomp Expansion

Device

Superheated vapor,

high pressure

Saturated vapor,

low pressure liquid+vapor,

low pressure

Saturated liquid,

high pressure

Condenser

1 2

3

4

high-side

low-side

Evaporator

Comp

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Single stage Direct-eXpansion (DX)

Eq

ua

lize

r lin

e

High

Pressure

Receiver

High pressure gas

King valve (automatic)

Condenser Evaporative Condenser

Compressor(s)

T T

High pressure liquid

DX Evap 1

Protected suction

Suction

Trap

Solenoid valve Thermostatic

expansion valve

Equalizing line

T T

DX Evap n

Refrigerant

Transfer

System

To HPR

Dis

ch

arg

e lin

e



Eq

ua

lize

r lin

e

High

Pressure

Receiver

High pressure gas



Compressor(s)

T T


DX Evap 1

Protected suction

Suction

Trap


expansion valve

Equalizing line

T T

DX Evap n

Refrigerant

Transfer

System

To HPR

Dis

ch

arg

e lin

e


25 psig (~11F)

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Eq

ua

lize

r lin

e

High

Pressure

Receiver

High pressure gas



Compressor(s)

T T


DX Evap 1

Protected suction

Suction

Trap


expansion valve

Equalizing line

T T

DX Evap n

Refrigerant

Transfer

System

To HPR

Dis

ch

arg

e lin

e


25 psig (~11F)

40 psig (~26F)


Eq

ua

lize

r lin

e

High

Pressure

Receiver

High pressure gas



Compressor(s)

T T


DX Evap 1

Protected suction

Suction

Trap


expansion valve

Equalizing line

T T

DX Evap n

Refrigerant

Transfer

System

To HPR

Dis

ch

arg

e lin

e


25 psig (~11F)

40 psig (~26F) 60 psig (~41F)

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Eq

ua

lize

r lin

e

High

Pressure

Receiver

High pressure gas



Compressor(s)

T T


DX Evap 1

Protected suction

Suction

Trap


expansion valve

Equalizing line

T T

DX Evap n

Refrigerant

Transfer

System

To HPR

Dis

ch

arg

e lin

e


25 psig (~11F)

40 psig (~26F) 60 psig (~41F)

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Compressor, rotary screw

Oil Separator

Compressor Motor

Motor

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Oil Separator

Oil

Compressor discharge

Motor Compressor

1st Stage Oil Separation 2nd Stage Oil Separation

Discharge

vapor

Oil Separator

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Compressors, reciprocating

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Eq

ua

lize

r lin

e

High

Pressure

Receiver

High pressure gas



Compressor(s)

T T


DX Evap 1

Protected suction

Suction

Trap

T T

DX Evap n

Refrigerant

Transfer

System

To HPR

Dis

ch

arg

e lin

e


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Condensers, evaporative

Ambient Air

Eliminators

Spray header

Makeup water

Moist, hot air out

Ambient Air

High pressure

vapor refrigerant, in

High pressure

liquid refrigerant, out

Remote sump

Condenser water

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Condensers, evaporative

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Evaporative condenser coil

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Eq

ua

lize

r lin

e

High

Pressure

Receiver

High pressure gas



Compressor(s)

T T


DX Evap 1

Protected suction

Suction

Trap

T T

DX Evap n

Refrigerant

Transfer

System

To HPR

Dis

ch

arg

e lin

e


30

Receivers, high pressure

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Eq

ua

lize

r lin

e

High

Pressure

Receiver

High pressure gas



Compressor(s)

T T


DX Evap 1

Protected suction

Suction

Trap

T T

DX Evap n

Refrigerant

Transfer

System

To HPR

Dis

ch

arg

e lin

e


32

King valve

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Eq

ua

lize

r lin

e

High

Pressure

Receiver

High pressure gas



Compressor(s)

T T


DX Evap 1

Protected suction

Suction

Trap

T T

DX Evap n

Refrigerant

Transfer

System

To HPR

Dis

ch

arg

e lin

e


34

Evaporator, air-cooling

Ceiling-hung evaporator in a dock area

Penthouse evaporator in a freezer

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Evaporator technologies

Air-cooling

Very low temperature blast freezing

Low temperature holding freezers

Higher temperature storage coolers, production areas, air-conditioning

Liquid-cooling (secondary fluids and products)

Shell-and-tube

Plate-and-frame

Falling film

Scraped surface

Plate-and-frame liquid chiller Shell-and-tube liquid chiller


Eq

ua

lize

r lin

e

High

Pressure

Receiver

High pressure gas



Compressor(s)

T T


DX Evap 1

Protected suction

Suction

Trap

T T

DX Evap n

Refrigerant

Transfer

System

To HPR

Dis

ch

arg

e lin

e


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Transfer system

Suction trap

Transfer drums

Oil pot

Evaporative Condenser(s )

Equalize line

High Pressure Receiver


High pressure gas

Flooded evap 1

Protected suction

To HPR

Suction

trap

King valve

Flooded evap, n

Solenoid

valve

Flooded evaporator

Hand expansion

valve

Float

Transfer

Station

Dis

ch

arg

e lin

e

Gravity flooded recirculation system

Compressor(s)

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Su

rge

Dru

m

Gravity flooded evaporator

Evaporator, liquid supply

Evaporator, vapor return

Float

Hand-expansion

valve

Solenoid valve

Evaporative Condenser Evaporative

Condenser

Eq

ua

lize

lin

e

Dry suction


High pressure gas

1

2

3

King valve

Pumped recirculator

4 Overfed

evaporator(s)

4

T

4

Wet

return

3


Condenser

Dis

ch

arg

e lin

e

Pumped liquid overfeed

Compressor(s)


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Liquid overfeed system

Recirculator

Float column

Liquid refrigerant pumps

Pumped liquid

line

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Liquid overfeed system components

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Lower evaporator temperatures

Requires lower evaporator pressures

Leading to increased compressor compression ratios

Limitations of specific compression technologies

Increased refrigerant discharge superheat

Two-stage compression systems

Equalize

line

Evaporative

Condenser(s)

Low

temperature

Evaporator(s)

Intercooler

Low

temperature

recirculator

Booster

Compressor(s)

High-Stage Compressor(s)


1 2

3

5

5

6

5

4

King valve

4

4

7

Medium Temperature Recirculator/ Intercooler

T

DX Evap

Two-stage compression (two temperature level with two stages of liquid expansion)

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Equalize

line

Evaporative

Condenser(s)

Low

temperature

Evaporator(s)

Intercooler

Low

temperature

recirculator

Booster

Compressor(s)



1 2

3

5

5

6

5

4

King valve

4

4

7


T

DX Evap


10.4 psia or 8.8 Hg (~40F)

Equalize

line

Evaporative

Condenser(s)

Low

temperature

Evaporator(s)

Intercooler

Low

temperature

recirculator

Booster

Compressor(s)



1 2

3

5

5

6

5

4

King valve

4

4

7


T

DX Evap


10.4 psia or 8.8 Hg (~40F)

196 psia or 181 psig (~95F)

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Equalize

line

Evaporative

Condenser(s)

Low

temperature

Evaporator(s)

Intercooler

Low

temperature

recirculator

Booster

Compressor(s)



1 2

3

5

5

6

5

4

King valve

4

4

7


T

DX Evap


10.4 psia or 8.8 Hg (~40F)


45 psia

(~17F)

Equalize

line

Evaporative

Condenser(s)

Low

temperature

Evaporator(s)

Intercooler

Low

temperature

recirculator

Booster

Compressor(s)



1 2

3

5

5

6

5

4

King valve

4

4

7


T

DX Evap


10.4 psia or 8.8 Hg (~40F)


45 psia

(~17F)

=196

45= 4.3: 1 =

45

10.4= 4.3: 1

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Condenser

Eq

ua

lize

r lin

e

Dry suction


Hig

h p

ressu

re liq

uid

High pressure gas

1

2

3


3


Condenser

Pumped

recirculator

4

Overfed evaporator(s)

4

T 4

Wet

return

Compressor(s)

Suction

Trap

Compressor(s)

T T

DX evaporator

Flooded

Evaporator

Whats a typical system?

Transfer

Station

To HPR

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Conclusions

Ammonia has been the mainstay refrigerant in the industrial sector

Must be aware of its safety considerations

As low GWP refrigerants continue to be pursued, ammonia applications are expanding

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QUESTIONS?

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What did you learn?

1. Where does the vast majority of ammonia originate from?

2. Which of the following materials is not compatible with

ammonia: carbon steel, stainless steel, copper,

aluminum?

3. Ammonia is considered highly flammable:

True or False?

4. The suction trap is needed to prevent compressors from

ingesting liquid refrigerant:

True or False?

5. Which of the following is not an industrial ammonia

system configuration: direct-expansion, liquid underfeed,

gravity flooded, two-stage?

Introduction to Ammonia Refrigeration...

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