Mathematical and experimental investigation of the use of solar conditioned air for solar assisted heat pump

The interest in solar assisted heat pump (GDIP) systems has been increasing in recent years, due to the more environmentally friendly, sustainable and performance heating solutions they provide by integrating solar energy into the system. The fact that the intensity of solar radiation is variable during the day and throughout the year makes it necessary for GDIP systems to be able to use different heat sources besides the solar. Air is the first heat source choice for heat pump applications, as it is a free and easy to use heat source that can be accessed anywhere. Therefore, an economical and performance efficient GDIP system should not ignore the use of air heat source. For the effective use of GDIP systems, they must be able to continue to benefit from the air and the solar despite the changes in ambient conditions, and this can only be possible with the simultaneous use of both heat sources. In this study, unlike the basic GDIP system classes in the literature, the case of using air and solar as heat sources simultaneously, by conditioning the air with solar energy, was investigated. The effect of the change in temperature and relative humidity of the evaporator inlet air on the air source heat pumps (HKIP) performance was determined by a developed mathematical model which is validated by the manufacturer's experimental data. Outdoor air temperature is the main factor affecting the performance of HKIP, in addition, the latent heat provided by the condensation of moisture in the cooling air causes the relative humidity also affects the performance. An increase in outdoor air temperature from 7°C to 14°C increases the COP value by 30%, while an increase in relative humidity from 0.6 to 1.0 increases the COP value by approximately 5%. The relative humidity of the inlet air of the evaporator can be achieved by pulverizing the water as droplets into the air stream, and this water can be heated by solar energy. For this reason, the time-dependent changes in the properties of air and water droplets in the air-water mixture flow were determined by the developed numerical model which is validated by the experimental test results. Input parameters are chosen as inlet air temperature and relative humidity, inlet droplet temperature and diameter, and air-water mass mixing ratio, and the output properties are determined as the outlet air temperature and relative humidity, mass droplet ratio and droplet temperature to define the application case in simplest way. The results show that the water droplet temperature has almost no effect on the output properties and evaporation always causes the air temperature drop. Correlations that yield results of models have been developed, in order to share full results of study, and give opportunity to researchers to take advantage of the models without having to re-build them.