Abstract

In the freezing process, a single evaporating temperature is normally used in the food industry. This work proposes a new technique which uses two evaporating temperatures in freezing process. Based on the Carnot principle, the bigger the temperature difference of refrigeration, the greater the energy costs. The new technique uses a higher evaporating temperature in the first period of the new freezing process. It allows most of the refrigeration capacity to be obtained for less temperature difference. Then the second period employs a lower evaporating temperature which makes the object further cooled to the final temperature required. In this way, the energy saving can be obtained by proper operations and adjustments to refrigerating plants. The parameters of the novel freezing technique are investigated and optimized using a personal computer. The simulation program is written in Quick Basic. Optimum parameters of the new process are studied for three refrigerants (R22, R502 and R717) and different schemes of industrial refrigeration plants and various objects to be frozen. The industrial implementation of the new technique is discussed. The results show that the novel freezing technique is feasible for industrial application, and the potential of its energy saving is significant.