Off-design of high temperature compression-absorption heat pump.

Most heat pumps are designed for optimal performance at one specific operation point. In real industrial applications though, the operating load and conditions change, thus, 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. In this work, a compression-absorption high temperature heat pump using water and ammonia was studied. The load was varied from 17% to 159% of the design point based on a measured demand in the industry, yielding average COPs of 2.02-2.08 for the different cases considered, with minimum and maximum values of 1.72 and 2.26. The absorption and desorption temperatures were also changed, showing strong impact on performance. The COP then varied between 1.67 and 2.35 Compressor efficiency was not kept constant, to fully exploit the effects. Several suggestions for improvement were identified.