Abstract
Phase change material can be used as heat transfer fluid in the solar water heating system, which is the latest way to improve thermal efficiency. In this paper, graphene composite paraffin emulsion is used as heat transfer fluid in a solar water heating-phase change material (SWH-PCM) system. By comparing with the traditional solar water heating (SWH) system, the thermal performance characteristics of SWH-PCM system have been investigated experimentally. The SWH-PCM system has higher heat storage than the SWH system. The heat storage of SWH-PCM system and SWH system all increase with the increase of solar irradiance, while the thermal efficiency has the opposite trend. The flow rate has a greater influence on the thermal efficiency of SWH-PCM system than that of the SWH system. With the flow rate of 200 L/h, the thermal efficiency of SWH-PCM system is 14.21% higher than that of the SWH system. In summary, the SWH-PCM system is a promising solar water heating system with high heat storage and thermal efficiency.
Highlights
Energy shortage is one of the most challenging issues around the world
The heat transfer characteristics of the composite paraffin emulsion and water are compared under the solar irradiance of 500 W/m2 and the flow rate of 550 L/h
The reason is that brown diffusion and heat transfer of paraffin particles both lead to enhance the sliding of particles in water, which can increase the convective heat transfer coefficient
Summary
Energy shortage is one of the most challenging issues around the world. There are two solutions to energy shortage; one solution is to replace the existing fossil fuels using clean and renewable energy, such as solar energy, wind energy, tidal energy, biomass, etc. The other solution is to enhance the energy utilization efficiency. As a clean, renewable and abundant energy source, has become an effective alternative to fossil fuels. The solar energy application range is very wide and divided into two categories from the perspective of its utilization. The other one is photothermal utilization, which is to use the solar collector to provide hot water/air for daily life, directly for heating, can be used in the seawater desalination, solar drying and so on. For the solar water heating system, the research focus has always been to improve the thermal efficiency of the system and reduce the heat loss of the system
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