Optimization, climates, compressor, efficiency, Air conditioning units
Total life-cycle cost of a system are the costs incurred by the owner over the entire life of the system. The two main components of this are: 1) initial cost: cost to purchase the system, often defined by the total/maximum capacity and quality of the system, and 2) operating cost: the cost of operation over the entire life of the system, defined by the daily usage and the efficiencies of the system and its components. Most compressors are designed by trying to minimize the initial cost. Minimal data are available on the selection of a compressor based on its design variables and the corresponding cost impact. A comprehensive link between the design requirements and their initial and operating cost implications is lacking in the industry. This project tries to address this issue by analyzing the impact of design variables on the total life cycle cost of an automobile air conditioning (AC) unit when located in different climatic zones. Using an earlier, experimentally validated, analytical model, the isentropic efficiency and volumetric efficiency of a reciprocating compressor are varied to suit the environmental conditions of four climatically (temperature, average length of cooling season, humidity) diverse cities - Phoenix, AZ, Peoria, IL, Minneapolis, MN and Miami, FL. The model connects the efficiencies to sub design parameters of a compressor namely the polytropic exponent, clearance ratio, geometry, etc. among others. The lowest possible life-cycle cost and the corresponding compressor specifications are determined and reported. Using this in the design of AC units (residential/commercial, automobile) will result in the best compressor design for a given application. For colder climates (Peoria and Minneapolis) the optimum isentropic efficiency and volumetric efficiency of a compressor averaged at 51% and 69% respectively, whereas for hotter climates (Phoenix and Miami) the efficiencies averaged at 60% and 73% respectively.