Experimental Assessment and Thermal Performance of an Ammonia-Water Absorption Heat Pump Available to Purchase

In this paper, an experimental assessment and thermal performance of a prototype ammonia-water absorption heat pump are carried out. The experimentations are conducted for different operating conditions such as: filling up concentration (40 and 47%), inlet brine temperature (-5, +5 and +15 °C) and inlet cooling water temperature (20 [25], 30 and 40 °C). The effects of performance parameters like refrigerant vapor concentration leaving rectifier, mass fraction spread and specific solution circulation ratio are also investigated. The results are divided into two categories. The first one is an external analysis of the absorption system considering thermal loads and system performance. However, the second one represents the internal analysis of the heat pump taking into account the temperature glide and degree of subcooling. Little effect is found for the filling up concentration on the thermal loads for different heat pump components as well as the heating capacity and the coefficient of performance. The refrigerant vapor concentration of the refrigerant vapor should not be less than 0.999 to avoid the effect of temperature glides on the system performance. Temperatures of the cooling water, brine and generator all have large effects on the system performance as any sorption system. Inaccurate expansion valve control leads to lower heating COP. Controlling the mass fraction spread or the specific circulation ratio affects considerably thermal loads of different absorption system components. The control of these two parameters can be accomplished by controlling the solution pump and flow rates in the solution loops.