Optimal Sizing of the Discharge Port Area of a Reciprocating Compressor Utilizing Computer Simulation Technique

Computer simulation of the thermodynamic cycle of the cylinder process of compressors providef' valuable information for compressor engineers. For example, the valve losses and the gas pulsation losses can be estimated from the simulation results. In general, the results of the computer simulation suggest that increasing the discharge port area always reduces the related valve loss and thus helps improve the efficiency of the compressor. However, in reciprocating compressors, a larger discharge port area tends to increase the clearance volume which may adversely affect the efficiency. Therefore, changing the discharge port area may sometimes give an unexpected result. In this work, a design procedure is proposed to determine the optimum discharge port area which balances these two conflicting effects by utilizing computer simulation program. A possible experimental method is also suggested to obtain empirical parameters necessary to use the proposed design procedure. INTRODUCTION A compressor simulation progran1 is a very useful tool for compressor designers. For example, thetmodynamic efficiency, refrigerant mass delivery per cycle, valve flow losses and gas pulsation losses of a prototype compressor can be predicted from the simulation result [1, 2]. However, some types of losses such as electric motor losses or friction losses can not be identified from the simulation result. The basic assumption of this study is that such losses are able to be identified and classified into two types; one which is proportional to the P-V work and the other which is approximately constant. In this work, the first type is called variable loss and the second is called constant loss. Accepting the above assumption, the total energy consumption of a compressor per one cycle may be considered as the combination of the P-V work, constant loss and variable loss as follows: