Parametric analysis and multi-objective optimization of a heat pump dryer based on working conditions and using different refrigerants

Considering Heat pump dryers are extensively used in the food industry, evaluating and optimizing their performance can be beneficial. Therefore, a comprehensive model is presented in this study using for waste food with considerations of energy, exergy, and exergoeconomy. Several influential parameters, such as evaporator and condenser temperatures, heat pump capacity, dry and wet-basis moisture content, along with the product mass and refrigerant types, are considered in the investigation. Five environmentally-friendly refrigerants of, R134a, R1234yf, R1234ze, R717, and R152a, are used as the working fluid of the heat pump. The parametric study shows that evaporator and condenser temperatures and heat pump capacity have significant effects on the heat pump COP, exergy efficiency, drying time, and cost of dried product. Hence, assuming these four objective functions, a multi-objective optimization model based on the TOPSIS method is presented. According to this, the optimal point of the system is found at the evaporator and condenser temperatures of 10.32 degrees C and 69.68 degrees C, respectively. Results of the refrigerant analysis demonstrate that although R717 has the best energetic performance, using R1234yf results in the shortest drying time and lowest cost of dried product.