Design And Experimental Study Of An Open-cycle Small-scale Ammonia J-T Cooling System

With the rapid development of the electronic technology, the densityof packaging, the density of integration and the capability ofmicroelectronics are in continual improvement. As a result, more heat fluxis generated, which brings higher requirements to the heat dissipation.Therefore, the cooling system for the electronic equipment is graveness.For the equipment used in the aerospace, it is necessary to control thetemperature for the safety.In the paper, an open small-scale ammonia J-T cooling system isdesigned to transfer3kW power and to control the temperature of analuminum plate operated below40℃in120s, utilizing about1.57L space.Compared to other working fluids, ammonia is chosen as the refrigerantdue to its high cooling capacity. In the cooling system, capillary tubeworks as the throttle component to drop the pressure of the working fluid.Numerical investigation has been conducted on the capillary throttlingcharacteristics, using the Hopkins-Cooper method. The effects of differentinner diameters, pressures of ammonia and flow rates on the throttlingeffects are conducted through numerical simulation.Through simulation, two1.0mm inner diameter capillary tubes arechosen in the system. After fabrication and construction of theexperimental set-up,0W~4kW heating loads are added to the system totest its cooling effect. The experimental results show that the system canprovide cooling capacity to cool3kW heat load and all the temperaturemeasurement points stay below the upper temperature limit in a givenperiod of time. It demonstrates that the designed ammonia J-T cooling system can realize the strict requirements for electronic equipment withhigh heat dissipation.