500°F Absorption Heat Pump Under Development

Abstract

Economic industrial heat pumping to temperatures above 500°F (260°C) is promised in the near future. A new absorption fluid is the key. Tested under DOE sponsorship, the new fluid has proven to be thermally stable and noncorrosive to austenitic stainless steel up to 500°F, or mild steel up to 430°F. Heat transfer properties are comparable to those of the conventional LiBr-H20 system. Paired with water as the working fluid, laboratory tests have shown that useful temperature lifts of over 162°F (90°C) ∆T can be achieved allowing 10°F heat exchangers. The fluid is nontoxic and noncombustible. Good economics for the system should stem from (1) high temperature capabilities for wider and more highly valued uses, (2) high internal temperature lifts for low heat exchanger surface areas, (3) predominantly carbon steel components, and (4) better COP in the heat amplifier mode than current absorption heat pumps. Recent laboratory results are presented including temperature applicability maps.