Abstract

An analytical model is proposed to evaluate the performance of a Direct Expansion Solar-Assisted Heat Pump under a given environmental condition. These thermal machines commonly employ uncovered flat plate solar collectors, and given this, the convection phenomenon is taken into account as well as the effect of the diffuse and reflected solar radiation in addition to the normal beam radiation absorbed by the tilted surface of the collectors. The heat pump cycle is modelled through a first law of thermodynamics approach in order to compute the heat yielded through condensation and the minimum heat required by the volume of water in the thermal storage unit. Consequently, the thermal capacity of the heat pump, the ratio at which the system yields heat to a given load of water, is calculated and discussed. The results of the model proposed are compared with the experimental data provided by three research papers with experiments conducted in different geographic coordinates and test rigs operating during diverse atmospheric conditions. A maximum relative error of 20% was obtained and furthermore, a statistical analysis of the data was conducted having found that there is no significant statistical difference between the analytical and experimental data samples within the 95% confidence interval. Finally, based on the thermal capacity, the performance of the heat pump is evaluated and a multi-objective optimization technique is implemented to obtain the best possible combination of factors to further enhance the performance of the heat pump.

Highlights

  • In the last few decades, issues regarding efficient energy consumption have become relevant and efforts towards the research and development of new technologies or alternatives to harness renewable energies, as well as new energy saving polices have increased

  • In order to harness the additional energy provided by the sun, a particular configuration of heat pumps known as Direct Expansion Solar-Assisted Heat Pump (DXSAHP), was developed which combines solar collectors and outdoor heat exchangers into a single bare flat plate

  • An analytical model to evaluate the performance of a DXSAHP under a given environmental condition was developed

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Summary

Introduction

In the last few decades, issues regarding efficient energy consumption have become relevant and efforts towards the research and development of new technologies or alternatives to harness renewable energies, as well as new energy saving polices have increased. To address this matter, solar collection systems for domestic applications have been proposed as an alternative to reduce the dependence on conventional fuels and decrease greenhouse gas emissions. These are thermal machines that operate under a vapor compression cycle and employ solar collection devices, are considered a sustainable alternative to the already existing conventional gas burner appliances used to provide a comfort through a final product, mainly hot water or air, for water heating systems (WHS), or climate control, heating, ventilating, and air-conditioning (HVAC), respectively [1].

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