An air-cooled evaporator will be placed in a room and the evaporator temperature will be -40oC. What should be the air temperature to and from the cold room to the evaporator? The screenshot is attached. Thank you.
Dear Mr. Cenker Aktemur
greeting
You can not guess the air temperature in the cold room depending on the evaporator temperature only, because the cooling load of the room it is most important to determine the design temperature of the evaporator and its capacity, so gradually you can draw the thermal mapping for the cold room after limitation of
1- room cooling load
a- storage material load
b- structure load ( walls, roof, floor, door ....etc
c- limit design condition inside the cold room (your function)
d- decided the nature for the heat transfer from load to evaporator (with high or low Reynold number) and may be natural convection
also it must be select the suitable evaporator by select the suitable face area outer dimeter of pipe with fins beside you must to know the number of circuits of evaporator to define the overall heat transfer coefficient
out side condition it must be define to determine the correct value of cooling load through the wall door, floor and roof
One of the best program you can used Coolselector-2 by Danfoss
ASHRAE Refrigeration 1990 it is so useful
With my respect
Ali D. Salman So let me ask the question this way. The operating temperature of the air-cooled evaporator is -40oC. The cooling load of the room is 50 kW. The room is well insulated. What should be the temperature of the air entering and leaving the evaporator?
Mr. Cenker Aktemur
You must to assume the cold room temperature as your application ( what temperature you need to apply) , and supply air temperature ( outlet from evaporator) must be design as which type evaporator you have ( efficiency)
While the air input through evaporator as I told you, it must be make your calculation.
Generally, without having any information for the evaporator as a heat exchanger, you cannot get accurate temperature difference between refrigerant and inlet air through evaporator
you can gauss the temperature difference between the refrigerant (-40 C) and air inlet through the face of evaporator about 12C that mean the room temperature as a homogenous temperature about -28C
while the supply temperature approximately equals to Ts= -34 C
Ali D. Salman thank you very much. In this case, will the temperature of my room be -28oC or -34oC?
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