Register now or log in to join your professional community.
It is similar to product load. It is basically heat that need to be removed from a refrigerated product to reduce its temperature to desired level.
Load is calculated using this relation:
Q=W*C*(T2-T1)
W: Weight of Product
C: Specific Heat
T1: Entering Temperature
T2: Space Temperature
If you need more details refer to Principles of Refrigeration : Roy J. Dossat
Pages146,153 and154
If you have a high suction pressure, the compressor will develop some very high pressures internally before the rotor port open to the discharge. A variable Vi compressor can take care of this to a point. The manufacturers provide a maximum suction pressure for each compressor based on compressor Vi. This is a sustained or lengthy run condition to pull a large system down.
Pull down conditions, consider evap temp at least10c° higher and select motor, provide crank-case PR regulator or MOP valve. But do not forget to size condenser to match pull down load.
Example, if your design needs -35 c°ࣴࣴࣴࣴevap, take pull down suction temp at -25 c°at least.
