Parametric analysis and model development of a combined absorption–compression high temperature heat pump with a natural working fluid

The urgent need to adopt clean heat in industrial processes cannot be overstated in light of the pressing issue of climate change and the mandatory compliance with environmental regulations. The combined absorption – compression heat pump based on the Osenbrück cycle is a noteworthy high-temperature heating technology that holds great promise for industrial high temperature applications. In this work, a model of a combined absorption compression heat pump is developed. The system utilizes an ammonia/water mixture as natural working fluid. The model is used to simulate different working conditions, and the performance of the system are studied according to the ratio between the weak and strong solution mass flow rates, f . The maximum sink heat load and the temperature lift are found at f = 0.4. For this operating condition, the COP is minimum. A trade-off between heat and temperature requirements and efficiency of the system occurs. The performance of the heat pump are evaluated for variable sink and source inlet temperatures and mass flow rates, as well as variable overall heat transfer conductance UA of absorber and desorber. To obtain the maximum sink heat load, high values of UA and sink mass flow rates should be implemented. Reducing the sink mass flow rate while keeping the UA high maximizes the temperature lift, decreasing at the same time the sink heat load. When ṁ sink = 0.3 kg/s, UA = 7 kW/K and T sink,in = 60 °C, the sink outlet temperature reaches 110.7 °C, which is the maximum temperature achieved in the simulations.