Abstract:A multi-temperature vehicle incorporating phase change material (PCM) was designed to help multi-temperature joint distribution and widen temperature control range, which integrated on-board refrigeration system, the phase change cold storage tank (PCCST), heat-insulated compartment (divided into freezing and cooling unit), air guiding device, thermal insulation board and so on. The PCCST (using 360kg PCM, which had a melting temperature of -30.0℃ and a latent heat of 175.3kJ/kg) was set independently in front of the vehicle and charged by a refrigeration system by using cheap electricity at night when it was stationary. During transportation, the freezing unit derived and regulated the cold air from PCCST through the air supply system of the heatinsulated carriage, and the cooling unit imported and regulated the cold air through the air guiding duct on one side above the heat-insulated carriage. The results of simulation and experiment were compared and analyzed as follows when the space ratio of freezing unit to cooling unit in the heatinsulate carriage was 1∶1, and the temperature was set to be -15.0℃ and 3.0℃, respectively. It was showed that the temperature root mean squared error between simulation and test was between 0.7℃ and 1.1℃, and the overall deviation was reasonable, which could better reflect the distribution of temperature field in the multitemperature cold storage vehicle. In addition, the results showed that the multi-temperature cold storage vehicle could maintain the temperature of the products at -15.0℃ and 3.0℃ for more than 10h during the transportation. In fact, the average air temperature of the multitemperature carriage was distributed between -14.2~-12.9℃ and 3.4~4.2℃ whose fluctuation ranges were 1.3℃ and 0.8℃, respectively. The coefficient of absolute nonuniformity of temperature was less than 0.6 when the freezing unit was -15.0℃ and less than 1.2 when the cooling unit was 3.0℃. The above parametric study showed that the average temperature fluctuation value of novel multi-temperature cold storage vehicle was 73.7% and the coefficient of absolute nonuniformity was 50% lower than that of the traditional cold storage vehicle. The further simulation of changing the space ratio of freezing unit to cooling unit in the carriage also showed that the temperature field in the carriage was uniform and could meet the actual transportation needs.
