Testing results of tubeless flat-plate phase-change solar collectors

This paper reports on a tubeless solar collector charged with Refrigerant-113 (R-113) that was installed and tested. Steady-state performance of this system showed high efficiency values; this was due to phase-change heat transfer characteristics of a boiling process that is accompanied by low plate temperature as well as low thermal resistance to heat flow from the absorber plate to the working fluid. The only resistance to heat flow toward the working fluid is the conduction resistance through the upper plate, which is negligible.