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This paper presents the mathematical modeling of a liquid-to-water heat pump with scroll compressor, brazed plate heat exchangers, additionally built-in liquid-vapor heat exchanger (LVHX) and a desuperheater for domestic hot water (DHW) production. The refrigerant is the zeotropic mixture R407C and the liquid used in the outdoor loop is a propylene-glycol water mixture. Developed mathematical model is validated on experimental data and used as a tool for the heat pump analysis. Simulation results are obtained for the effect of the degree of superheat at the evaporator outlet, the subcooling degree at the condenser outlet, the effect of using or not the LVHX and the effect of using or not the desuperheater for DHW for typical operating conditions of liquid-to-water heat pumps (EN-14,511-2, 2011) in the cooling and heating modes (low and medium temperature applications). Results show that the effect of the degree of superheat or the decision on the suitability of using or not a LVHX may be different for heat pumps that include or not a desuperheater for DHW. In particular, if DHW is a priority, the use of a LVHX is recommended because it leads to higher COP (or EER) values as well as to higher DHW heating powers. [ABSTRACT FROM AUTHOR]

The aim of this article is to present the reason and the process of creating new modified mathematical model of heat pump plate condenser. The fundamental mathematical model is modified according to analytical optimization procedure. The adaptation is carried out by applying the procedure of elimination. The modified mathematical model include 2 governing equations instead of 6. The two governing equations contain 2 unknown dependent variables and 6 known parameters. The modified mathematical model is validated using the comparative method. The compared data are obtained by numerical simulation using fundamental and modified mathematical models. Applying both models the obtained data fully coincided. By using the new modified mathematical model and implementing the optimization process may lead to the determination of the maximum energy efficiency of hot water subsystem. The subsystem comprises a condenser, a circulation pump, a connecting pipeline and the heating units. The objective function in the optimization process is the coefficient of performance, COP, as a function of the mass flow rate of the hot water or of the circulation pump power. The paper offers the implementation of modeling the circulation pump power to achieve the maximum value of the COP. [ABSTRACT FROM AUTHOR]