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 performances of the system are studied according to the ratio between the weak and strong solution mass flow rates f . The maximum of the sink heat load and the temperature lift are found at f = 0.4. For this working condition, COP is minimum. A trade-off between heat and temperature requirements and efficiency of the system occurs. The performances 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. • Developed a MATLAB model of a combined absorption–compression heat pump. • Used NH₃/H₂O mixture as a natural working fluid for high-temperature applications. • Identified optimum circulation ratio f = 0.4 for maximum thermal load and temperature lift. • Found trade-off: high heat and temperature output at expense of COP efficiency. • Demonstrated the strong impact of overall heat transfer conductance and mass flow rates on system performance.