New configurations of absorption heat transformer and refrigeration combined system for low-temperature cooling driven by low-grade heat

Abstract

A significant proportion of industrial waste heat and renewable energy is low-grade with temperatures below 100 °C, which can hardly drive the conventional absorption refrigeration systems for producing cooling below 0 °C. To solve this problem, an absorption heat transformer, whose absorber is combined with the generator of the absorption refrigeration system, is introduced to increase the temperature of the low-grade heat source to drive the absorption refrigeration system. Temperature matching between the two sub-systems and between the heat source and the combined system determines the performance of the combined system. Hence, new configurations and continuous-temperature-changing processes are proposed and numerically studied. Results show that the system performance improves significantly when continuous-temperature-changing processes are introduced, and the utilization temperature span of heat source and the refrigeration capacity increase by 80 % and 108 %, respectively. Moreover, the continuous-temperature-changing absorption-generation process is investigated by dividing into 8 sections, and it is found that the process achieves optimal performance, when the absorption side only has adiabatic and absorption sections, and the generation side only has adiabatic and generation sections. Results indicate that the proposed system shows great potential to harvest low-grade heat at 80 °C, and produce refrigeration capacity below −15 °C.