Polymeric Absorbers for Flat-Plate Collectors: Can Venting Provide Adequate Overheat Protection?

Venting and evaporative cooling are modeled as possible techniques for protecting polymer absorbers in single-glazed, flat-plate solar collectors from exceeding the material temperature limit during dry stagnation. Four venting options are considered: (I) venting above the absorber plate, (II) venting below, (III) dual venting, and (IV) venting with evaporative cooling. Results indicate that in hot, sunny conditions, venting may not provide adequate cooling to lower the absorber temperature to the relative thermal index of the polymeric materials currently in use or under consideration for this application. Venting combined with evaporative cooling from a wetted pad directly beneath the absorber plate is identified as a potential method of overheat protection in hot, dry climates.