Trane TRG-TRC011-EN manual 10C 37.8C

Page 43

period three

Capacity Control

notes

 

 

 

 

 

 

 

 

 

15 psia

 

5

concentration

 

 

 

 

 

 

 

 

 

[103.4 kPa]

 

0

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

e

 

0

 

 

 

 

 

 

 

 

 

 

r

 

 

 

 

 

 

 

 

 

 

u

 

5

 

 

 

 

 

 

 

 

s

 

 

 

 

 

 

 

 

 

 

s

 

5 psia

 

5

 

 

 

 

 

 

re

 

 

 

 

 

 

 

 

p

 

 

 

 

 

5

 

 

 

 

r

 

 

 

 

 

 

 

 

 

 

o

 

 

 

 

 

[34.5 kPa]

 

 

 

 

p

 

 

 

 

 

 

 

 

 

a

 

 

 

 

 

 

 

 

 

0

 

v

 

 

 

 

 

 

 

 

 

&

 

 

 

 

 

 

 

 

 

 

%

6

 

1 psia

 

 

 

 

 

 

 

 

 

'

 

 

 

 

 

 

 

 

 

 

 

 

 

[6.9 kPa]

 

 

 

 

 

 

 

 

 

 

 

 

0.1 psia

$

 

 

 

 

 

 

 

crystallization

 

[0.69 kPa]

)

(

line

 

 

50°F

100°F

 

 

 

150°F

200°F

LiBr solution

[10°C]

[37.8°C]

 

 

 

[65.6°C]

[93.3°C]

Figure 45

 

solution temperature

 

 

 

 

By plotting the single-effect absorption refrigeration cycle on the equilibrium chart, it is apparent that crystallization is most likely to occur in the heat exchanger. At this particular condition, the 65% concentrated solution (') is cooled to 135°F [57.2°C] (() as it passes through the heat exchanger. As noted previously, the saturation temperature of 65% solution is 123°F [50.6°C] so there is no danger of crystallization.

Consider, however, if the solution was instead 66% concentrated and cooled to the same 135°F [57.2°C] temperature. The saturation temperature for 66% concentrated solution is approximately 143°F [61.7°C]. The result would be a deposit of salt crystals inside the heat exchanger. Prolonged operation at this condition could result in a buildup of salt that would eventually block the passages through the heat exchanger, interrupting the operation of the chiller.

Once a chiller is crystallized, operation can only be resumed after the solution temperature is raised above its saturation temperature, above 143°F [61.7°C] in this example. At this higher temperature, the salt crystals would return to the solution, allowing the chiller to operate again.

With the advent of microelectronic controls, modern absorption water chillers are designed to monitor and control solution concentrations and temperatures, allowing the chiller to operate over a broad range of conditions without danger of crystallization. In addition, safety controls are available to avoid crystallization and even to de-crystallize the chiller if necessary. Therefore, crystallization is not the serious problem that it once was with absorption chillers.

38

TRG-TRC011-EN

Page 42 Page 44
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Page 42 Page 44
Contents Air Conditioning Clinic Absorption Water Chillers Absorption Water Chillers Preface Contents TRG-TRC004-EN Introduction TRG-TRC011-EN Period one Absorption Refrigeration CyclePeriod one Reject heat Heat energy Absorption System Fluids High affinity for water refrigerant Components of the Absorption Cycle Conditions Steam or Hot waterrefrigerant vapor Generator Condenser Refrigerant then flows into the evaporator pan Absorber spray pump Solution Heat Exchanger Dilute Generator pump Equilibrium Chart Heat Solution temperature Period two Absorption Chiller TypesSingle-Effect Chiller Absorber Evaporator spray pump Spray pump Generator pump Double-Effect Chiller Vapor Low Temperature condenser Cooling Generator Water Evaporator Absorber Low-temperature generator pump Generator pump Absorption Chiller Types Direct-Fired Chiller Evaporator High-temperature high-temperature Generatorgenerator pump Chiller/Heater Absorption Chiller Types Changeover Absorption Chiller Types Period three Capacity Control Period three Energy valve Generator Crystallization 10C 37.8C Capacity Control Capacity Control Capacity Control Heat exchanger bypass Evaporator pan Purge System Isolation valve Period four Maintenance ConsiderationsPeriod four Maintenance Considerations Test run with alternate fuel, if dual-fuel burner Maintenance Considerations Maintenance Considerations Corrosion inhibitor and performance additive recommendations Period five Application ConsiderationsCooling-Water Temperature Limitations Combination Chiller Plants 58F Special Considerations for Direct-Fired Chillers Application Considerations Equipment Rating Standards Period six ReviewPeriod six Review Review Review Questions for Period QuizQuiz TRG-TRC011-EN Answers Glossary Glossary Glossary Trane Company
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