Vapor-compression refrigeration system coupled with a thermochemical resorption energy storage unit for a refrigerated truck

Currently, refrigerated trucks adopt vapor-compression refrigeration systems for controlling the temperature of refrigerating compartment. This inevitably increases fuel consumption and exhaust emissions of engine. Although the solid sorption refrigerator can recover exhaust waste heat to generate cooling capacity, the low exhaust temperature at idle, often below 150 °C, significantly restricts its application in refrigerated trucks. To tackle these problems, a novel refrigeration system, including a vapor-compression subsystem and thermochemical resorption energy storage unit, using MnCl2/CaCl2-NH3 as the working pair, is proposed in this paper. To date, this is the first study wherein the system performance test is conducted on a refrigerated truck. Experimental results indicate that thermochemical energy storage can effectively recover waste heat of exhaust gas to store cold energy, and the refrigerating capacity during the discharging process is 2.2 kW at an evaporator outlet temperature of −15 °C. Moreover, cold energy can be released irrespective of whether the truck is parked or driven. Measurement of the liquid level in the liquid reservoir is an effective method for determining the point at which the operation switches between energy discharging and charging processes. At an ambient temperature of 30 °C and a refrigerating temperature of −20 °C, the energy efficiency of the novel system is 1.4, which is twice that of a conventional system. Furthermore, although energy storage increases initial investment of system, the payback period is estimated to be less than one year. In conclusion, the novel system effectively reduces transportation costs and satisfies the requirements of refrigerated trucks in a stable manner.