Branched GAX cycle gas fired heat pump

GAX absorption heat pump cycles are characterized by the generator-absorber heat exchange (GAX) between the high-temperature end of the absorber and the low temperature end of the generator. The improved thermodynamic performance of the basic GAX cycle coupled with its mechanical simplicity has attracted substantial interest in using this cycle for gas-cooling. However, to be competitive in a cooling dominated market, the cycle has to achieve high cooling performance and also low installed cost. The branched GAX (BGAX) cycle promises higher cooling performance using similar components as the basic GAX cycle and an additional solution pump. By increasing the solution flow rate at the hot end of the absorber, the BGAX cycle makes more complete use of the temperature overlap. As a result, less external heat is supplied and higher coefficients of performance (COPs) are obtained. A breadboard prototype of the BGAX cycle has been developed and is now operating. A novel thermosyphon cooled absorber eliminates the need for the outdoor hydronic loop, and reduces cost by 10%. Other component improvements yield another 10% cost reduction. The breadboard prototype has operated for more than 200 hours. Gas cooling COP=0.87 has been consistently achieved at 30.6°C (87°F) ambient conditions. At the 35°C (95°F) ambient capacity rating condition, a cooling load of 4.5 refrigeration tons was achieved at a cycle COP=0.95