PERFORMANCE OF POLYPROPYLENE AND STEEL TUBES IN SOLAR WATER-HEATERS WITH NATURAL CIRCULATION

Performance of solar water heaters in thermosyphonic flow with polypro pylene and steel tubes was studied experimentally. An experimental app aratus consisting of 36 south-facing parallel tubes was designed and b uilt especially for this study. Experiments were performed at Sharif U niversity of Technology in Tehran during July-August 1994 from 0900 to 1700, when the ambient temperature varied from 29 to 36 degrees C. Ov erall, 30 experiments were conducted for both types of tubes. At first , it was found that the best collector slope for both types of tubes w as 36 degrees and it is independent of tube type. Generally, it was fo und that polypropylene tubes under similar conditions can increase wat er temperature by 10 degrees C more than steel tubes. Based on the res ults shown in this study, use of polypropylene tubes in solar water he ating systems is recommended.