Investigation of the effect of rollbond evaporator design on the performance of direct expansion heat pump experimentally

• Effect of rollbond evaporator design to performance of the DX-SAHP is investigated.
• Experiments performed on three identical DX-SAHP systems except evaporator design.
• Evaporators’ material is aluminum and R134a is the working fluid.
• Empirical correlation derived for system COP in terms of radiation and temperature.
• The correlation provides the average deviation of 9% with the experimental data.

In this study, the rollbond evaporator design which gives maximum coefficient of performance for the direct expansion solar assisted heat pump (DX-SAHP) water heater is investigated experimentally on the three separate heat pump systems due to the lack of studies on the effect of collector-evaporator design to the system performance. Three DX-SAHP systems are identical except collector-evaporator design. Aluminum is preferred for the evaporator material and R134a as the working fluid.Maximum COP value was obtained as 3.30 for System-1 while COP values for System-2 and System-3 were 3.14 and 2.42 respectively at the same conditions. An empirical correlation which gives the COP value of the System-1, which provides highest COP, with respect to the solar radiation and outdoor temperature of the system has been found using the experimental results obtained during the study. The correlation was found to be in good agreement with the average deviation of 9% with the experimental data.