The Dlesign Of A Refrigeration Unit For Marine Reefer Container And Its Performance Research

The key technologies of marine reefer container’s refrigeration unit have been monopolizedby foreign companies. The in-depth research on marine reefer container’s refrigeration unit wasstill at the initial stage. In this paper, the calculation of cooling load of marine reefer containerwas carried out and the design and selection of key components of its refrigeration unit wasconducted. An experimental rig for marine reefer container’s refrigeration unit was built and thenits performance was studied using the rig.Firstly, in order to obtain the total cooling load of marine reefer container, the cooling loadsfrom heat loss of container box, ventilation and air exchange, cargo breathing and cooling,evaporator fan and defrost were calculated respectively. According to the container’s totalcooling load, the design and selection of refrigeration compressor, condenser, evaporator,throttling device and fans were carried out. In the refrigeration unit developed, the refrigerantwas R404A; the refrigeration compressor was the hermetic scroll compressor ZMD18KVEproduced by Copeland; and the expansion device was a kind of thermal expansion valveTGES51/2x5/8produced by Danfoss.Secondly, an experimental rig for marine reefer container’s refrigeration unit wasestablished with a data acquisition system which can measure power, temperature and pressure.The refrigeration unit had a high efficiency subcooler loop, a hot-gas bypass capacity controlloop and a suction modulating valve. The electrical control system of the refrigeration unit wascomposed of PLC and a touch screen. The PLC program had three operation modes (frozenmode, refrigeration mode and heating mode) and two defrost modes (manual defrost and timeddefrost). Configuration interface of touch screen included initial view, refrigeration system view,startup view, alarm view, user management view and data monitoring view.Finally, using the experimental rig, the performance of the marine reefer container’srefrigeration unit was studied. It could be found from the experimental results that the innertemperature of reefer container can be lowered from30°C to-10℃in34minutes with the powerconsumption of2.93kW. Furthermore, the system performances respectively under hot gasbypass capacity control and suction modulating capacity control were studied respectively whenthe high efficiency subcooler was put into operation and when the subcooler not work. Theexperimental results showed that the high efficiency subcooler could help lower the dischargetemperature of refrigeration compressor and improve the COP of refrigeration unit.