Field evaluation of microencapsulated phase change material slurry in ground source heat pump systems

Abstract

Microencapsulated phase change material (MPCM) slurries were field-tested in ground source heat pump (GSHP) systems in the Southern United States to validate their thermal performance and durability as heat transfer fluids (HTF). MPCM particles consisted of methyl stearate (melting temperature: 39.5 ˚C) as phase change material (PCM), microencapsulated with polyurea shell. Experimental results showed that MPCM slurries transport more thermal energy than water at a constant pumping power due to the higher heat capacity associated with the PCM. Demonstration experiments showed that using MPCM slurries improved the heat load-to-pumping power ratio by up to 34 % when using a coaxial heat exchanger. The coefficient of performance of the GSHP system was enhanced by up to 4.9 % when using MPCM slurries. It can be concluded that MPCM slurries are viable HTF because of their higher heat capacity. In terms of durability, no

Numerical Investigation of the Effect of Nanoparticle Diameter and Sphericity on the Thermal Performance of Geothermal Heat Exchanger Using Nanofluid as Heat Transfer Fluid

“…This section investigates the effect of nanoparticle diameter on the overall performance of GHEs in different cases. The heat transfer rate can be calculated by [43]:…”

“…The total pressure drop, which is proportional to the energy consumption of the pump, was obtained by [43]:…”

“…The average total pressure drop by time in the steady state was selected for further studies. The performance efficiency coefficient (PEC) was used to evaluate the energy efficiency of nanofluid, in comparison to water and can be obtained by [43]:…”

“…Where m is the mass flow rate of the fluid, pf C is the specific heat of the fluid, inlet T is the inlet temperatures of the fluid, and outlet T is the outlet temperatures of the fluid. The total pressure drop, which is proportional to the energy consumption of the pump, was obtained by [43]…”

“…The effect of different nanoparticle sphericity on the energy efficiency of nanofluid in the GHEs was compared using the following energy efficiency ratio [43]:…”