Coefficient of Performance Optimization of Single-Effect Lithium-Bromide Absorption Cycle Heat Pumps

In this paper, we investigate the coefficient of performance (COP) of a LiBr absorption cycle heat pump under different operating conditions. The investigation is carried out using a dynamical model fitted against data recorded from an actual heat pump used for district heating in S⊘nderborg, Denmark. Since the model is too complex to study analytically, we vary different input variables within the permissible operating range of the heat pump and evaluate COP at the resulting steady-state operating points. It is found that the best set-point for each individual input is located at an extreme value of the investigated permissible range, and that the COP optimization is likely to be a convex problem. Further, we exploit this observation to propose a simple offline set-point optimization algorithm, which can be used as an automated assistance for the plant operator to optimize steady-state operation of the heat pump, while avoiding crystallization issues.