Abstract
To investigate the impacts of using nano-enhanced phase change materials on the thermal performance of a borehole heat exchanger in the summer season, a three-dimensional numerical model of a borehole heat exchanger is created in the present work. Seven nanoparticles including Cu, CuO, Al2O3, TiO2, SiO2, multi-wall carbon nanotube, and graphene are added to the Paraffin. Considering the highest melting rate and lowest outlet temperature, the selected nano-enhanced phase change material is evaluated in terms of volume fraction (0.05, 0.10, 0.15, 0.20) and then the shape (sphere, brick, cylinder, platelet, blade) of its nanoparticles. Based on the results, the Paraffin containing Cu and SiO2 nanoparticles are found to be the best and worst ones in thermal performance improvement, respectively. Moreover, it is indicated that the increase in the volume fraction of Cu nanoparticles could enhance markedly the melting rate, being 0.20 the most favorable value which increased up to 55% the thermal conductivity of the nano-enhanced phase change material compared to the pure phase change material. Furthermore, the blade shape is by far the most appropriate shape of the Cu nanoparticles by considering about 85% melting of the nano-enhanced phase change material.
Highlights
Due to extreme environmental pollution and energy shortage around the world, the exploitation of renewable energies has become more vital
Since the vertical ground heat exchanger (GHE), named borehole heat exchanger (BHE), needs less land for installation and has wide applicability and better performance than the horizontal GHE, it has been comprehensively investigated in recent years [1]
The results indicated that the differences between the inlet and outlet temperatures of the working fluid are 0.24 ◦ C when using soil backfill and 0.08 ◦ C for the phase change material (PCM) backfill at the end of the cooling operation
Summary
Due to extreme environmental pollution and energy shortage around the world, the exploitation of renewable energies has become more vital. Geothermal energy is one of the renewable energies that can be used, by means of coupling to ground source heat pump (GSHP) systems. GSHP system provides heating and cooling of buildings through the ground heat exchanger (GHE) which usually appears in horizontal and vertical configurations. Since the vertical GHE, named borehole heat exchanger (BHE), needs less land for installation and has wide applicability and better performance than the horizontal GHE, it has been comprehensively investigated in recent years [1]. To improve the thermal performance of the BHEs, various approaches have been taken such as geometry improvements [2,3], the use of new materials for pipe, backfill or grout, and working fluid [1,4]. Quaggiotto et al [5] studied two types of BHEs including coaxial BHE and double
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
