Fluid Flow and Heat Transfer Characteristics of Microencapsulated Phase Change Material Slurry in Turbulent Flow

Abstract

Microencapsulated phase change material (MPCM) slurry is consisted of a base fluid in which MPCM is dispersed. Due to apparent high heat capacity associated with phase change process, MPCM slurry can be used as a viable heat transfer fluid (HTF) for turbulent flow conditions. Heat transfer and fluid flow properties of the slurry in turbulent flow (3000 < Re < 6000) were determined experimentally. Dynamic viscosity of the MPCM slurry was measured at different temperatures close to the melting point of the material (20-30 C). Pressure drop measurements under turbulent flow conditions were recorded for 6 MPCM samples at various concentrations. The pressure drop of the MPCM slurry was comparable to that of water despite the higher viscosity of the slurry. The effect of heat flux, MPCM mass concentration, flow rate and the type of phase change material was investigated. The effective heat capacity of slurry at the location where phase change occurs was found to be considerably higher than that of water. A nondimensional Nusselt number correlation was proposed in order to facilitate design of heat transfer loops with MPCM slurries as working fluid.

Performance characteristics of microencapsulated phase change material slurry in a helically coiled tube

“…The experimental results clearly showed that the viscosity of MPCM slurry is independent of shear rate and the coefficient of variation r X of the viscosity is less than 1.2%. Therefore, it can be concluded that MPCM slurries behaves as Newtonian fluids at the tested mass fractions, ranging from 2.1% to 10.9%, which is consistent with previous experiments and observations [1,3,8,9]. Using the temperature-dependent viscosity data, the Andrade equation was used for estimating fluid viscosity as a function of fluid temperature, which is defined as follows:…”

“…They also found that the heat transfer coefficient was affected by the slurry velocity more significantly than by heat flux. Taherian et al [3] measured the heat transfer coefficient of MPCM slurry under turbulent flow conditions using a horizontal circular tube as well. The experimental results showed that the heat transfer coefficient decreased with increasing the mass fraction of MPCM in the slurry at the same fluid velocity because of the reduced momentum transfer between the fluid and the tube wall.…”

“…The durability of MPCM particles can also ensure that all the results obtained from the experiments are reliable and repeatable. The effective specific heat of the slurries as a function of time was used to evaluate the stability of MPCM particles [3,26]. The effective specific heat values of the MPCM slurries remained constant after about 550 cycles of pumping for each corresponding mass fraction.…”

“…As Table 1 shows, mass fraction has a slight effect on thermal conductivity. The specific heat of the MPCM slurry without phase change was calculated using the following equation [1,3]. where c p,MPCM and c p,w are the specific heat of MPCM and the specific heat of water, respectively.…”

“…Alvarado et al [2] also studied how to reduce subcooling (or supercooling) of microencapsulated n-tetradecane by adding tetradecanol (2 and 4 wt%) to the PCM. Taherian et al [3] used and characterized methyl stearate as a PCM and the MPCM particle size http://dx.doi.org/10.1016/j.ijheatmasstransfer.2016.05.047 0017-9310/Ó 2016 Elsevier Ltd. All rights reserved. was less than 5 lm.…”