Abstract
The paper describes experiments carried out on an ammonia-vapour compression refrigerator, with the object of investigating the conditions affecting the volumetric efficiency of the compressor. The most important part of the investigation deals with the effect of the condition of the vapour at the suction valve, over a range from about 0·75 dry to 45 deg. F. superheat, on both the actual and the indicated volumetric efficiencies. The actual volumetric efficiency drops about 20 per cent between the superheated and the wet conditions, but the indicated efficiency shows little variation. The results lead to the conclusions that the decrease in volumetric efficiency is due to condensation of ammonia on the cylinder walls during the compression and delivery stroke, and that the temperature of the cylinder wall is the critical factor determining the vapour condition at which the drop in efficiency begins. Other variables investigated were the condenser and evaporator pressures, and the compressor speed.
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