Pinch design method for heat exchanger networks with optimal heat pump selection

• A Pinch Analysis-based method is proposed for the integrated design of heat pump and heat exchanger networks. • When multiple heat pumps are integrated, conventional rules of Pinch Analysis may no longer apply. • Increased number of heat pumps increases the efficiency of the process. • The complexity of the network increases with the number of integrated heat pumps. This study presents a novel design method for heat exchanger networks with integrated heat pumps. Recent investigations have demonstrated the potential for heat pumps to utilize the heat pockets of the Grand Composite Curve to minimize total work consumption for a process. Building on the state-of-the-art, this study combines the sink and source profiles with state-of-the-art COP approximation methods to find the optimal heat pump sink and source temperatures, refrigerant, and cycles with any constraint number of heat pumps to achieve the minimum work requirement. The method is applied to a milk evaporator case study, showcasing the potential to exploit heat pockets when multiple heat pumps are involved. From a total process heat demand of 23,990 kW, the combined heat exchanger and heat pump network could achieve work requirements of 1421 kW in the case of a single heat pump and 902 kW when two heat pumps are considered. In the case of multiple heat pump integration, heat pumps are placed independently from the Pinch temperature, challenging the conventional rules of pinch analysis. While efficiency is improved by increasing the number of heat pumps, the complexity of such networks must be tackled, and further optimisation could be necessary before their implementation. The application of heat exchanger network relaxation methods becomes necessary in these cases.