Development of solar-driven absorption cycle heat pump grain drying system

A commercially available lithium bromide-water absorption cycle air conditioner was operated as a solar-driven heat pump. Solar energy from flat plate collectors was used as the driving force. Four operational conditions were tested: (1) a closed cycle mode, (2) a regular heating/cooling mode, (3) a latent-to-sensible heat transfer mode with moisture loading added manually, and (4) a latent-to-sensible heat transfer mode with moisture loading added by drying grain.; Operational characteristics were tested on both clear and partly cloudy days. Generator inlet water temperature, condenser inlet water temperature, air temperature entering the evaporator, and moisture load at the evaporator were found to be the most important operational parameters affecting the performance of the system. In regression analyses with third-order polynomials the performance of the system as measured by coefficients of performance for cooling and heating (COPc and COPh) were described, for each operational mode, by these four parameters with R-square values above 0.82. COPc and COPh both increased as generator inlet water temperature decreased. COPc increased but COPh decreased as condenser inlet water temperature increased. Both COPc and COPh increased as air temperature entering the evaporator and moisture load at the evaporator increased.; Results from the solar-driven absorption cycle heat pump grain drying operational mode indicated that 40 percent of the electrical energy required for grain drying can be saved compared to a compressor driven heat pump system and 60 percent compared to an electrical resistance heating system. The latent-to-sensible heat transfer operational mode was more efficient than the regular heat/cooling mode.