Thermal performance of a simplified parallel power and refrigeration combined cycle with refrigeration as the main task

Abstract

• Simplified parallel power/refrigeration combined Kalina cycle was studied. • Obtaining larger refrigeration energy is the main purpose of the new combined cycle. • There is no desorption process of basic solution in the simplified cycle. • Simplified cycle was evaluated by efficiencies based on energy quality and quantity. • Simplified cycle can maintain high performance with much larger refrigeration capacity. A simplified parallel power and refrigeration combined cycle based on the Kalina cycle (SPPRA-KC) using ammonia-water as working fluid is proposed and studied, in which refrigeration is taken as the main task and the refrigerant plays a leading role in improving the concentration of work solution. The turbine exhaust vapor is utilized to heat the work solution fed to the refrigeration sub-cycle, resulting in more refrigeration energy produced. Parameter analysis was conducted under temperatures of heat source/cooling water of 400 °C/30 °C from the perspective of energy quantity and quality. To obtain larger refrigeration capacity and power recovery efficiency, the dew point temperature of work solution and bubble point temperature difference in the boiler shall be as higher as possible and properly increased, respectively, which will cause more irreversible losses in the cycle, resulting in lower effective exergy efficiency. When optimizing the cycles with work concentration of 0.5 based on the effective exergy efficiency, the power recovery efficiency of the SPPRA-KC is 34.8% much higher than that of the related original cycle (PPRA-KC) due to much larger refrigeration capacity, and the effective exergy efficiency of the SPPRA-KC is 1.67% and 12.4% relatively higher than those of the PPRA-KC and the Kalina cycle, respectively. Besides, the main exergy destruction of the SPPRA-KC occurs in the boiler, absorbers, exhaust heat source and turbine.