Comparison Of Hermetic Scroll And Reciprocating Compressors Operating Under Varying Refrigerant Charge And Load

An experimental rig has been built to test a horizontal scroll compressor and a reciprocating compressor of similar size and capacity. The compressors were tested with refrigerant.R404A operating at varying evaporator and condenser temperatures. The paper provides much needed information regarding the efficiency of the compressors operating under the same conditions with the same system parameters. This paper also reports on investigations being carried out on the effect of refrigerant charge on both types of compressor. The results show that the scroll compressor generally produces cooling capacities and COPs that are equal to or greater than the reciprocating compressor. Both compressor types exhibit the same general characteristics with respect to system charge. In particular, COP is reduced with significant underand over-charging. Superheat and subcooling are shown to be functions of system charge level for both compressors and thus may be used as a general indicator of charge level, irrespective of the compressor type. INTRODUCTION The scroll compressor has gained wide acceptance in recent years in commercial applications. The compactness and lightweight of scrolls along with apparent low sound and vibration level has made them very popular. One of the scroll compressor advantages is that the number of moving components is very low compared to reciprocating compressors. Also, it is reported that the volumetric and isentropic efficiencies are higher than similar sizes of reciprocating compressors. However, little information is available on how well it compares in performance with an equal size reciprocating compressor under similar load variation and refrigerant charge variation which can be useful when replacing reciprocating compressors with scroll compressors. The use of scroll compressor in supermarket packs which serve remote display cabinets have become widespead in the UK, (Hundy 1998). However, because of the height of the vertical scrolls they are yet to replace the small reciprocating compressors used in integral cabinets. Hence a horizontal scroll was used in order to establish its operation characteristics and evaluate whether it will be able to easily replace reciprocating compressors in integral display cabinets.