View Full Version : Evaporator and Condenser

07-01-2017, 01:39 PM
Hi guys, I have some questions regarding condensers and evaporators :

1 – Regarding condensers, I talked with someone about this. My friend told me we can divide condenser into 3 sections :
top "de-super-heater"
middle : "condenser"
bottom "sub-cooler"
For R22, Suppose that ambient temperature is 45C and humidity is 30% and our condenser has 150 m2 heat transfer area. I think when temp. of ambient is 45C even we increase heat transfer area of condenser form 150 m2 to even 500 m2 ! we can not sub-cool R22 and for sub-cooling we must use sub-cooler heat-exchanger (By expansion R22 form liquid line into heat-exchanger).
With these ambient situation [I told above] can we sub-cool R22 by increasing heat transfer area of condenser ?
If no why in different books mention bottom of condenser as sub-cooler ?

2 – Regarding evaporators, In different books I see that writer names end of evaporator as super-heater. But as you know at low temperature cold-rooms we must use accumulator to prevent liquid coming back to suction of compressor even we use proper expansion valve and proper heat transfer area at evaporator, By this all of companies use accumulator in below zero systems.
Twice I have a question, While in below zero systems we can not evaporate all of liquid of refrigerant why in different books and sources they show that end of evaporator as super-heater ?

Sincerely yours.

08-01-2017, 03:15 PM
Assume that at ambient 45C condensing temperature is 50C. R22 will condense at 50C. If bottom of condenser is full of liquid refrigerant, ambient air will cool it from 50C to 47C. 50-47=3C is subcooling. If bottom of condenser is not full of liquid refrigerant, refrigerant condensation will continue in this bottom part and no subcooling.
Accumulator separate liquid and vapour refrigerant. Sometimes vapour can carry liquid when significant change of refrigeration load or when compressor start up.

09-01-2017, 09:35 AM
Condensers using ambient air can only hope to condense Vapour to liquid at ambient temperatures. 45 C Ambient...45 C liquid temperature in an ideal situation. Using a larger Condenser will not help because the longer tubing creates resistance and more work for the Compressor. More work = inefficiency.

Lower the liquid temperature by using some Condensed 45C liquid into a TX or Capillary to a heat exchanger? That will simply reduce the volume of liquid available to the TX valve. Gives the Compressor some additional cooling via the Suction gas and reduces discharge temperatures.

Double edged Sword.