Method for the Optimal Design of Vacuum-Evaporative Heat Pumps

• Main Authors: Mikhail A. Kuznetsov, Victoria A. Tarasova, Dionis Kh. Kharlampidi
• Format: Article
• Language: English
• Published: NAS of Ukraine, A. Pidhornyi Institute of Mechanical Engineering Problems 2019-06-01
• Series: Journal of Mechanical Engineering
• Subjects: thermoeconomic model; vacuum-evaporative heat pump; exergy losses; resulting costs
• Online Access: https://journal-me.com/archive/en/2019/2019_2_3_eng.pdf

A method is developed for optimally designing vacuum-evaporative heat pumps that use water (R718) as a refrigerant. This method is based on the autonomous method of the thermoeconomic optimization of thermodynamic systems, and makes it possible, when optimizing the design and choosing economical modes of system operation, to simultaneously take into account both thermodynamic and economic parameters. When solving the optimization problem, the resulting costs (RC) of creating and operating the system during the estimated service life are taken as the objective function. The mini-mum of RCs corresponds to the optimal characteristics of the system while maintaining its performance. The development of the thermo-economic model of the vacuum-evaporative heat pump made it possible to represent the objective function in the form of detailed analytical expressions that take into account the relationship between all the optimizing parameters of the system. The numerical solution to the problem of the thermoeconomic optimization of the operating and design parameters of the vacuum-evaporative heat pump embedded in the cooling system of the second circuit of thermal and nuclear power plants (TPP and NPP) allowed finding the optimal system parame-ters ensuring the conditions for achieving the minimum RCs. At the same time, for 25 years of operation, the estimated value of the RCs of this heat pump was reduced by 35% through a more rational distribution of energy flows therein. An analytical solu-tion to the optimization problem in the form of a system of partial derivatives of the objective function of RCs for all optimizing variables is suitable for any heat pump op-erating according to the considered scheme and with a similar type of equipment. The influence of the electricity tariff variability and yearly active time of the vacuum-evaporative heat pump on the economic effect of its thermoeconomic optimization is investigated. The application of the developed methodology in practice should help reduce the financial costs for creating and operating vacuum-evaporative heat pumps that use water as a refrigerant, increase their competitiveness compared to traditional freon systems and create the conditions for their large-scale implementation.