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High temperature heat pumping (HTHP) is a key technology for minimising emissions from industrial process heat. One option for improving thermal efficiency in heat pump cycles is to match temperature profiles of the refrigerant with the heat source and heat sink fluids as closely as possible. For a pure chemical species evaporation occurs essentially at constant temperature, making it difficult to match the temperature profiles of the refrigerant and heat source fluid. However, the evaporation process for refrigerant mixtures occurs over a range of temperatures, and this range can, within limits, be customised for a particular process. This study describes the development of a heat pump model implemented in Python (checked against data generated in Aspen HYSYS) that was used to investigate whether binary mixtures of alkanes are capable of yielding higher COPs and higher exergy efficiency values when compared to each alkane in its pure form as a result of reduced exergy destruction. A general trend for all mixtures was that COP and second-law efficiency were maximised when the mass fraction of the smaller molecule was between 0.1 and 0.3. It was also observed that the trend was magnified when the difference in boiling points between the two constituents increased. For a heat source glide between 35 °C and 40 °C and a heat sink glide between 40 °C and 80 °C, a mixture of 17 % propane and 83 % pentane gave the highest COP of 4.5 and the highest exergy efficiency of 44.7 %. [ABSTRACT FROM AUTHOR]

The aim of this paper is to use Monte Carlo Simulation (MCS) to conduct an analysis of the flexibility and controllability of retrofitted Heat Exchanger Network (HEN) designs. Historical plant data is often uncertain and variable but is an important tool for understanding the real-time operation of a HEN. MCS uses these uncertainties to give an analysis of the retrofitted HENs, and it can be used in a more detailed analysis of the controllability and flexibility. Using Monte Carlo Simulation, inflexibility has been defined as the probability of a HEN to fail to meet temperature targets within defined tolerances. Inflexibility can be used as a tool to guide the retrofit analysis of a HEN. A retrofit HEN design should improve the flexibility of the network without compromising on the expected energy savings. The proposed method is demonstrated using a four-stream HEN problem. The inflexibility of the network was shown to be improved with bypass control and optimal allocation of retrofit area and the proposed method succeeds in augmenting the retrofit design method so that costeffective, flexible retrofit HENs can be identified. [ABSTRACT FROM AUTHOR]

Heat pumps are the key technology to decarbonise thermal processes by upgrading industrial surplus heat using renewable electricity. Existing insight-based integration methods refer to the idealised Grand Composite Curve requiring the full exploitation of heat recovery potential but leave the question of how to deal with technical or economic limitations unanswered. In this work, a novel Heat Pump Bridge Analysis (HPBA) is introduced for practically targeting technical and economic heat pump potential by applying Coefficient of Performance curves into the Modified Energy Transfer Diagram (METD). Removing cross-Pinch violations and operating heat exchangers at minimum approach temperatures by combined application of Bridge Analysis increases the heat recovery rate and reduce the temperature lift to be pumped at the same time. The insight-based METD allows the individual matching of heat surpluses and deficits of individual streams with the capabilities and performance of different market-available heat pump concepts. For an illustrative example, the presented modifications based on HPBA increase the economically viable share of the technical heat pump potential from 61% to 79%. [ABSTRACT FROM AUTHOR]