Large numbers of studies are reported on solar collectors using a single fluid to cool it, be it with water or with air only. The present paper reports a series of experiments that investigate into the performance of solar collectors that are cooled by an airwater mixture, a two-phase heat transfer fluid. This special way of cooling of solar collectors is designed in conjunction with a humidification-dehumidification cycle that produces hot water and saturate air at the same time to run an

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... ient solar distillation unit. Parameters analyzed in the study include the effects of the air-to-water ratio and the inner diameters of the absorber tubes of the solar collector. A mechanism to control air-water ratio was also developed in the process. The results indicate that the two-phase flows can efficiently cool solar collectors producing better cooling of absorber plates of solar collectors, under suitable operating conditions.