Abstract
In order to evaluate and improve the performance of a ground-coupled heat pump (GCHP) heating system with radiant floors as terminals, an exergy analysis based on test results is performed in this study. The system is divided into four subsystems, and the exergy loss and exergy efficiency of each subsystem are calculated using the expressions derived based on exergy balance equations. The average values of the measured parameters are used for the exergy analysis. The analysis results show that the two largest exergy losses occur in the heat pump and terminals, with losses of 55.3% and 22.06%, respectively, and the lowest exergy efficiency occurs in the ground heat exchange system. Therefore, GCHP system designers should pay close attention to the selection of heat pumps and terminals, especially in the design of ground heat exchange systems. Compared with the scenario system in which fan coil units (FCUs) are substituted for the radiant floors, the adoption of radiant floors can result in a decrease of 12% in heating load, an increase of 3.24% in exergy efficiency of terminals and an increase of 1.18% in total exergy efficiency of the system. The results may point out the direction and ways of optimizing GCHP systems.
Highlights
Recent years have witnessed the considerable rise of the building energy proportion in the total energy consumption in China
The results show that in the whole system the location of maximum exergy loss ratio is the compressor, while the location of minimum exergy efficiency and thermodynamic perfect degree is the ground heat exchangers (GHE)
If fan coil units (FCUs) were substituted for the radiant floors in this ground-coupled heat pump (GCHP) heating system in terms of the test results, the total exergy efficiency of system would drop to 13.7%
Summary
Hepbasli and Akdemir [10] presented an energy and exergy analysis of a GCHP system with a fan coil unit (FCU) as terminal. Exergetic efficiencies and exergy destruction rate of the system components were determined and the potential for improvements was presented. The heat produced by solar collectors is stored in underground storage tanks, and the heat pump utilizes the water in underground tanks as heat source in heating season They investigated the energy and exergy flows, and quantified exergy losses in the overall system. For the sake of rational selection of terminals, this study deals with the influence of the two types of terminals on the energy and exergetic performance of a GCHP heating system. The exergy flows and exergy efficiencies in a GCHP heating system with radiant floors and in a scenario system with FCU as terminal are analyzed respectively. The analysis results are used to give suggestions for the improvement of the system performance
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