Measurement testing of heat transfer coefficients in the evaporator and condenser of heat pumps

Abstract

In our earlier studies, it has been stated that the validity and limits of correlations developed for the calculation of heat transfer processes in the evaporator and condenser of heat pumps are not published in general. The values yielded for model structures and process characteristics indicate extreme ranges of standard deviation. While the description and physical and mathematical modeling of phenomena occurring in heat pump components have developed really much and the mathematical accuracy of solutions can be increased at one's own discretion, descriptions of changes in heat transfer and heat transfer coefficients in the course of refrigerant flow are quite uncertain. At the same time, these factors highly influence the accuracy of the solution. Our study presents the measurements and the new proposed heat transfer correlations, developed on the basis of such measurements, which can be used for calculating heat transfer in heat pump evaporators and condensers with higher accuracy than existing correlations in the literature.Keywords Evaporator Á Heat transfer coefficient Á Heat pump Á Condenser Á R134aList of symbolsVolumetric flow rate (m 3 h -1 ) M Molecular mass (kg kmol -1 )Greek letters a Heat transfer coefficient (Wm -2 K -1 ) k Thermal conductivity (Wm -1 K -1 ) q Density (kg m -3 )

Optimization of heat pump system

“…(10)) was selected. The Santa correlation [14], (Eq. (11)) was used for the prediction of the heat transfer coefficient in flow boiling.…”

“…The proposed heat transfer coefficient of evaporation was partly based on the GungoreWinterton correlation [15]. The Santa correlation [14], (Eq. (12)) was applied to obtain the condensation heat transfer coefficient, which is modified by the Akers correlation [16].…”

Investigation of the Thermodynamic Characteristics of the Ester Oil and R152a, R125, R134a and R123 Refrigerant Mixtures

“…The accuracy of the heat pumps models is greatly affected by the accuracy of the pressure drop correlations which are used to determine the pressure drop of the refrigerant flowing in the tubes and the heat transfer correlations [5], [6] which are used to determine the heat transfer coefficients. In the literature, there are a large number of correlations of heat transfer and pressure drop, whose accuracy, validity is uncertain.…”