Evaporator temperature vs equipment temperature

[Acrisoft]

Hi

Is there a formula to calculate or to suppouse the evaporator temperature of an equipment
by the equipment temperature.

For e.g. if a freezer temperature is 18C, which should be the temperature on its evaporator surface ?


Moises

[Tony]

Hi Acrisoft,

so long as you know your required room temperature, minus 10K and that will give you temperature that the refrigerant is evaporating in the evaporator.

e.g. Coldroom temperature required -30°C - evaporating temperature -30°C minus 10K = -40°C

[Yuri B.]

Hello. Easier to simply measure. But, the evaporator temp at which point ? If you can attach a sensor to the part of the evaporator where capillary goes into it you would know almost precisely the evaporation temperature. If you measured the temp at the outlet you would know how good the evap is filled. Why?

[750 Valve]

The greater the TD between room temp the greater the evap capacity so in theory you can run a smaller sized evap - the trade off is to run the lower suction pressures you need bigger compressor and in turn condenser.

RH comes into the equation too - the lower the TD between room temp and evaporating temp the higher the RH in the room will be as less moisture is frozen to the coil as the coil is not as cold.

6K is a safe TD between room temp and evaporating temp, so for a room at -18C I would select at -24C if the customer did not give me any other specifications or requirements, I would also do this for medium temp rooms unless they have open meat then i would work off a maximum 4K TD but you really need to refer to evap manufacturers data.

If you are looking at existing equipment that you did not design all you can really do is see what the suction pressure is and compare it to the room temp, a big TD means a small evap (compared to the compressor's capacity) and vice versa. YOu need to be mindful that all of the design happens for the maximum conditions (highest ambient) so often capacity control must be employed to keep system equilibrium.

[Shaukat]

it should be 10 k delta t