The GAHP and the water tank temperature were monitored during the period of the experiment by using twenty-four K-type thermocouples, positioned at different levels and locations inside the HP-ETSC, and the increase in internal energy of the system could be calculated.
During each experiment, the amount of solar energy input (1 in w/m2) at evaporator region of GAHP is transferred to the condenser region and removed by the condenser, and the overall thermal resistance ([R.
Figures 6-8 show the temperature distribution over the wall surface of GAHP associated with the optimal filling ratio 70% from the results which are illustrated in figs.
6 the GAHP operates at a higher wall temperature with 30[degrees].
2: GAHP thermocouple positions (surface wall and core)
7: Variation of GAHP thermal resistance for the three angles at optimal filling ratio 70%.
8: Variation of temperature with the distance along the wall of GAHP at optimal fill ratio 70% during solar time at title angle 30[degrees].
It has the simple design and ability to transfer heat even with very small temperature difference, hence GAHPs are widely used in waste heat and renewable energy applications  .