The document discusses different types of evaporators used in refrigeration systems. It explains that a flooded evaporator allows evaporation both inside and outside the tubes by maintaining a constant level of liquid refrigerant. This fully utilizes the refrigerant for latent heat transfer. In comparison, direct expansion evaporators only allow evaporation inside the tubes, with the refrigerant exiting in a superheated state. Flooded evaporators are typically used for applications like cold storage and require more refrigerant than direct expansion systems.

1. Sanjivani Rural Education Society’s
Sanjivani College of Engineering, Kopargaon-423 603
(An Autonomous Institute, Affiliated to Savitribai Phule Pune University, Pune)
NAAC ‘A’ Grade Accredited, ISO 9001:2015 Certified
Department of Mechanical Engineering
Subject:- Heating, Ventilation and Air
Conditioning (ME 411)
B.Tech.Mechanical
Purushottam W. Ingle
Assistant Professor

2. 1
Role of compressor
• Heart of refrigeration system
• Main role is to increase the boiling point, to increase pressure ratio.
• Increase pressure up to condenser medium, if the available cooling
medium is air then compressor has to compress more, if it is water
then compression is slightly less.
• Air cooled system consumes 10 to 15 % more energy than the water
cooled system, since air is cooling medium so its temperature is
comparatively high, so compressor has to raise the boiling point up to
that temperature. Compression ratio is high as compared to water
cooled system.
P.W. Ingle Department Of Mechanical Engineering, Sanjivani COE, Kopargaon
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24. • In flooded evaporator, there is a possibility of evaporation inside the
tube as well as outside the tubes.
• In direct expansion, in DX type outlet of evaporator state of
refrigerant is superheated. Refrigerant evaporates directly inside the
tubes.
• Flooded evaporators are associated with float type expansion valve.
• DX type evaporators are associated with thermostatic expansion valve
or capillary tubes.
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26. • First refrigerant coming out of condenser enters in float type
expansion valve.
• When level decreases, flow of refrigerant start from expansion valve,
then the constant level of refrigerant is maintained.
• Now from bottom of surge tank refrigerant is made to flow, so
refrigerant absorbs heat, fins are also provided to have effective heat
transfer.
• Due to absorption of heat some of the refrigerant gets evaporated.
• Circular dots in tube indicates vapor droplets.
• This vapor formation occurs outside tube also.
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27. • Here the entire heat transfer area is flooded with liquid refrigerant, so
its called flooded type of evaporator.
• So at inlet of evaporator state of refrigerant is liquid and at outlet is
liquid with vapor.
• Now refrigerant is collected in the accumulator, so here separation of
liquid and vapor refrigerant is taking place, so in upper portion the
vapor is accumulated and at the bottom liquid is collected.
• So only the vapor is sucked during the suction process of
compression, sometime liquid refrigerant may be sucked, some
baffles are provide to avoid liquid suction.
9/4/2023 P.W. Ingle Department Of Mechanical Engineering, Sanjivani COE, Kopargaon

28. • So here only latent heating is taking place, and refrigerant is fully
utilized. So its thermal performance is good.
• Again it requires more quantity of refrigerant, 1.5 to 1. 7 times more
refrigerant is required as compared to DX type.
• So here cheap refrigerant is required as compared to DX type
evaporator.
• So here entire heat transfer area is flooded with.
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30. • Flooded type evaporator used in cold storage, here surge drum is
provided, in which the liquid refrigerant flow inside evaporator tubes,
and liquid vapor coming out of tubes accumulated in the surge drum.
• So only vapor is escaped from surge tank to compressor.
• Liquid supply from condenser have expansion in float type expansion
valve and then low pressure low temperature liquid refrigerant is
going to evaporator coils from surge drum.
• So cooling of air is taking place, so it is air cooling fin tube flooded
type evaporator.
• Now cooled air is delivered to the cold storage.
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32. • It is a shell and tube type heat exchanger.
• Here in the shell there is a refrigerant, and through the tubes liquid
which is to be cooled is circulated.
• From bottom liquid refrigerant enters in the shell and suction of vapor
refrigerant is taking place from top side.
• Entire tubes are submerged in the refrigerant so it is called as flooded
type.
• Liquid which is to be cooled flows in as shown and required chilled
liquid got as shown by giving its heat to refrigerant.
• Some top portion is kept for accumulation of vapor refrigerants.
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38. • Here refrigerant flow through the tubes, and water flows over the
tubes.
• Number of baffles are provided for proper flow of water as shown.
• At inlet refrigerant is in complete liquid condition, at outlet refrigerant
is in completely dry condition, mean no mix condition.
• Generally used when refrigerant is costlier, 10 times more than
ammonia.
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