18 May 2017
Most heat pumps are designed for optimal performance at one specific operation point. It is however quite usual that the operating load and conditions change. Because of this, the heat pump should not only be considered at its optimum, but also, how and to which extend the off-design conditions affect its overall performance. A holistic approach for the most suitable choice of heat pump thus should include calculations and/or simulations of the heat pump at varying load and conditions, to evaluate its off-design performance. In this work, a hybrid high temperature heat pump, using water and ammonia, was studied. The load was varied from 10 to 130% of the designed point, giving COPs between 1.81 and 2.19, and the operating conditions, such as evaporation, condenser, absorption and desorption temperature and heat exchanger contamination, were changed separately and in combinations, giving COPs between 1.34 to 2.82. Compressor efficiency was not kept constant, to fully exploit the effects. The results are mapped. The most important factor for influence was temperature.