DEVELOPMENT OF EFFICIENT DEFROSTING STRATEGIES FOR REFRIGERATED TRANSPORTATION SYSTEMS: PART II - TEST PROCEDURE AND RESULTS

摘要

The instrumented test facility capable of being used in the development of efficient defrost strategies for transport refrigeration systems has been described in the accompanying Part I paper. This Part II paper outlines the test procedure and initial baseline tests performed to assess the performance of a commercial transport refrigeration system for simulated fresh and frozen loads placed within the 19.36m{sup}3 refrigerated compartment. These tests were conducted to, i) monitor refrigeration system behaviour while operating free from the effects of evaporator coil frosting, ii) investigate the effects of evaporator coil frosting on refrigeration system behaviour and performance, iii) analyse the performance of the refrigeration system during the hot-gas defrost cycle iv) establish benchmark data for the performance of a commercial transport refrigeration system under frosting conditions and during the defrost cycle. Tests were performed at compartment set-point temperatures of 0°C and -20°C. The main characteristics analysed were the refrigeration system refrigerant temperatures and pressures, discharge airflow rate from the evaporator coil, evaporator coil discharge and return air flow temperatures and compartment temperature. The most interesting feature emanating from these test results is the response of the refrigeration system to evaporator coil frosting. This study has allowed a complete characterisation of the frosting and defrosting sequence to emerge and is described in this paper including the implications on refrigeration system thermodynamic performance and compartment temperature control. The test results also reveal the sensors that most effectively identify the indication of coil frosting.