Refrigeration and air conditioning systems have to be designed for variable cooling capacity. The variable capacity requirement may be due to a variable load or simply to the fact that the system was designed for the expected peak load, while the working load is considerably lower than the peak load. This will require some form of capacity control such as hot-gas bypass, suction-line throttling, suction-valve unloading, variable-speed drive, intermittent running, etc. All of these methods for capacity control have their drawbacks.
The major drawback is the lowering of the thermodynaniic and volumetric efficiencies and the often catastrophic increase of the discharge temperature, f-or methods where the cqmpressors are running continuouslY at reduced mass flow: for control, and start and stop problems in the cases where the compressors are runnmg intermittently, also occur.
The present paper considers only systems that achieve capacity control by continuous reduction of the mass flow rate through the compressor (hot-gas bypass is therefore excluded). The discussion is limited to the effect of heat transfer through the metal parts fro:q1 the discharge gas to the suction gas. (The effects of the heat generated by the motor in the case of hermetic compressors has not been considered).
Citation: ASHRAE Transactions, Volume 77, Part 1, Philadelphia, PA
Product Details
- Published:
- 1971
- Number of Pages:
- 6
- File Size:
- 1 file , 500 KB
- Product Code(s):
- D-PH-2181
