Experimental Investigation of Pressure Drop in Valve Ports and Conduits of Hermetic Compressors

Method of measurement of pressure drop in ports of hermetic compressor under discharge pressure is presented. ?,22 gas at 298 psig and 215QF condition pumped by hermetic compressor is directed into flow bench type pressure chamber where variety of orifices is installed and pressure drop is measured directly. Compressor and flow bench are installed in series on standard calorimeter which measures capacity and refrigerant mass flow of tested compressor. Local resistance coefficient of test orifice is obtained. Variety of port configurations are tested for details of inlet and outlet edge influence on pressure drop. Port Inlet bellmouth radius sharp edge counterbore and bore finish chamfer Kidney Shaped Inlet Tube Inlet plain flared Gas Flow through Port and Valve effects of sculpturing of the outlet The method and the results proved valuable in understanding of gas flow and porting of compressors. INTRODUCTION With increase in cost of electric energy came the need to produce more efficient compressors at minimum cost. There is only a limited number of areas where improvements can be made: 1) Electrical more efficient and expensive motors 2) Mechanical Thermodynamics Choice of Refrigeration Friction Losses in Bearings Gas Flow Losses Streamlining of gas flow passages has the pontential of being the most economic way of producing an improvement. 26 A direct method of measuring the effects of streamlining was needed. Relatively large changes producing a minimum of 1.0% change in compressor .performance can usually be detected in standard calorimeter testing in one or two tests. Changes of 0.5 to 1.0% may require multiple testing and use of test data reduction to standard condition by means of lab computer. Since normal calorimeter accuracy is in the range of + 1%, changes below 0.5% are hard to detect. After the major improvements have been made, one has to refine detecting technique for the smaller improvements. Pulsating gas flow in compressor and addition of oil (around 0.3%) makes the use of data obtained for steady state flow of air and meter adequate only for estimation. The best approach was to test directly the actual port configuration under actual flow conditions of hermetic compressor. A flow bench allowing placement of t·est port in discharge line from the compressor was devised and constructed. TEST APPARATUS Orifice Plate Discharge Line From Compressor , Capillar}'..-Slope ~-