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Abstract
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In this research, the effect of microencapsulated phase change material (MEPCM) addition to water and producing
MEPCM slurry (MPCS) for heat transfer augmentation was investigated, experimentally and numerically.
Copper tube with and without butterfly tube inserts (BTI) was used as a test section in a laboratory apparatus and
was heated at a constant heat flux. Experiments were performed to determine heat transfer coefficient of MPCS
at the Reynolds number of 1500 and 2600 and containing up to 15 wt% MEPCM. The effect of tube inserts type
was also investigated numerically. The results showed that for the plain tube, the addition of MEPCM to the base
fluid improves heat transfer rate by up to 40.3% and 38.9% for non-laminar and laminar flow regimes, respectively.
Moreover, when the BTI was used, it was observed that the heat transfer rate increased by up to 234%
for pure water and by up to 180% for the 10 wt% MEPCM slurry under laminar flow regime. This is due to the
turbulence induced in the flow and the disturbance to the thermal boundary layer. Moreover, tube inserts cannot
have a significant effect on the heat transfer under non-laminar flow regimes. The inserts only increase the
pressure drop in these conditions. However, performance evaluation criteria (PEC) analysis indicated that 5%
MEPCM slurry provides the highest ratio of heat transfer enhancement to pressure drop increment. Furthermore,
in the simulation section, the results clearly indicated that the inserts shape have no significant effect on the heat
transfer coefficient.
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