The purpose of this research is to study the effect of inclination angles, working fluid of wickless heat pipes and the surface area of heat pipe (heat pipe evaporator area) on the thermal performance of the solar collector working with wickless heat pipe, under normal weather conditions. The solar collector with wickless heat pipe solar collector has been designed and implemented taking into account the ability to change angles of inclination of the solar collector from 25o to 65o also takes into account ease of charging and discharging the wickless heat pipes as well as the possibility of changing the ratios of thermal sink area (relative area of thermal sink " heat pipe evaporators " for the total area of the solar collector) through the discharging pipe with the kidney a special order. Distilled water was selected (Freon -118) and Freon 22 and Freon 134a and Freon -502 as working fluid for wickless heat pipe. Is installed, the percentage areal endothermic at 0.1727 and conducted tests to study the thermal performance of solar collector at angles starting from 25o to 65o for the horizontal axis with step 5. Then the solar collector tilt angle set to be 45o then the tests conducted to study the thermal performance of the collector at ratios of thermal sink area 0.0806, 0.0345, 0.01154 for each selected working fluid. The results were analyzed, and discussed. From results study, results can be summarized as follows:
- The thermal performance of the solar collector provided with wickless heat pipe was found strongly influenced by an angle of inclination. It was found that the best thermal performance solar collector using four working fluids at inclination angle 25o. Also similarity was found in the thermal performance of the solar collector at the angles of inclination 25o and 45o, for fluids operating Freon-22 Freon-502 and also found a similarity in the performance of the solar collector thermal performance when using Freon-134a and Freon-502 and when the inclination angle 45o.
- Also found that the thermal performance of the solar collector that has been tested is the best when using Freon -22 fluid as wickless heat pipe working fluid at all tested inclination angles when the ratio of thermal sink is 0.1727 and after that Freon-134a and Freon -502, where they give the same thermal performance of the solar collector and after that distilled water (Freon -118).
- With changing ratio of thermal sink at inclination angle 45o found that the greater the ratio of thermal sink area improve thermal performance of solar collector in for all tested working fluids. As well as when it was found that for thermal sink area ratio 0.0806 the thermal performance of solar collector using Freon 22 and Freon -502 are similar also the thermal performance of solar collector using Freon-134a and distilled water are similar.
- From comparing the practical results of this research with theoretical models which describe the performance of the flat plate solar collector and theoretical models governing the performance of wickless heat pipe it found that the thermal performance of solar collector is strongly influenced by the performance of wickless heat pipe. It looks like the same performance curve of wickless heat pipe through a certain range of temperatures.
- A theoretical relation to describe the performance of wickless heat pipe solar collector was developed. The suggested relation is mainly depending on the governing equation of wickless heat pipe. Good agreement for the developed relation with the experimental results.