Computer modelling and thermodynamic assessment of an aqua-ammonia absorption cycle solar heat pump

An assessment based on steady state thermodynamic analysis of an aqua-ammonia absorption cycle solar heat pump for space heating is presented. The system consists of a solar heated generator, rectifier, condenser, evaporator, absorber liquid heat exchanger and a subcooler. During heat pump operation, the evaporator absorbs heat at low temperature from the outside atmospheric air, while the heat rejected by the absorber, condenser and rectifier is used to warm the interior air of the space to be heated. A numerical computer modelling based on the solution of simultaneous heat and mass balance equations for various components of the system has been carried out. The influences of component temperatures and heat exchanger effectiveness on the heating coefficients of performance and heat transfer rates have been investigated to obtain optimum operating conditions for the proposed heat pump system. Further, the absorption cycles are compared with an ideal reversible cycle operating over the same range of temperatures. It has been found that the performance of the absorption cycle does not continue to improve as the input temperature increases and that additional components will be required to allow the machine to take advantage of the higher temperatures available from modern collectors.