Testing of a residential GAX absorption heat pump and chiller and verification of a computer cycle simulation

This research effort experimentally tested an advanced-cycle, ammonia-water absorption heat pump at 3 RT and a chiller at 3.3 RT and 5 RT. The components of the cycle were assembled with instrumentation, including flow meters, pressure transducers, and thermocouples. Each system was a Generator-Absorber Heat Exchange (GAX) cycle and all were sized for residential and light commercial use, where very little absorption equipment is currently used. The findings of the experimental portion of the research were cycle cooling load and Coefficient of Performance (COP), as well as many component heat duties and working fluid state points throughout the cycle. The COP of the heat pump was 0.43; that of the chiller at full load (5 RT) was 0.63. Appropriate weaknesses in the cycle were identified in order to improve the efficiency in the next generation machine.; A computer simulation of each cycle was performed and the simulations validated against the experimental results. Modeling with ABSIM-OSU involved some modifications to the simulation software as well as judicious changing of input parameters (component sizes and deviations from equilibrium) in order to move output results to agree with experimental findings. Modeling incorporated a heat loss from the gas fired generator and pressure drops in both the evaporator and absorber. Simulation results and experimental findings agreed closely and validated the modeling method and simulation software.; The original design cycle for the chiller (COP of 0.78) was modified based on lessons learned in the experimentation and modeling. The experimental cycle (COP of 0.63) had several components that did not perform to specification. In order to predict the cycle performance, several underperforming components were improved in the model. As a result, the design model and the experimental cycle model were reconciled. The modified design cycle predicted a COP of 0.71 and the modified experimental cycle predicted a COP of 0.70.; Existing market research shows that significant business opportunities exist for a GAX heat pump or chiller with a cooling COP of 0.70 or greater. The work performed in this study provides a validated computer simulation package capable of realistically predicting the performance of ammonia-water absorption cycles. As such, a realistic and reliable design tool is now available along with experimentally based values for essential modeling parameters.