Microencapsulated Phase Change Material Suspensions Research Articles

Experimental investigation on thermal conductivity and specific heat capacity of magnetic microencapsulated phase change material suspension

We develop a novel type of functional fluid-magnetic microencapsulated phase change material (MMPCM) suspension which incorporates the advantages of microencapsulated phase change material (MPCM) suspension and magnetic fluid (MF) for controllable and efficient energy transport processes. The specific heat capacity and thermal conductivity of this type of functional fluid are experimentally investigated, respectively. The effects of the mass fraction of components in the MMPCM on the thermal properties of the fluid are discussed. In addition, the effect of an eternal magnetic field on the thermal conductivity of the fluid is discussed.

J0103-4-1 相変化マイクロカプセル懸濁液の微細円管内強制対流熱伝達特性(電子情報機器,電子デバイスの強度・信頼性評価と熱制御(4))

J0103-4-1 相変化マイクロカプセル懸濁液の微細円管内強制対流熱伝達特性(電子情報機器,電子デバイスの強度・信頼性評価と熱制御(4))

An experimental study of convective heat transfer with microencapsulated phase change material suspension: Laminar flow in a circular tube under constant heat flux

By contrast with the conventional heat transfer fluid (water), the microencapsulated phase change material (MPCM) suspension, with a small temperature difference between storing and releasing heat, is of much larger apparent specific heat and much higher thermal energy storage capacity. It has been suggested to serve as a dual-functional medium for thermal energy transport and/or storage. The heat transfer characteristics of a kind of MPCM suspension, formed by microencapsulating industrial-grade 1-bromohexadecane (C 16H 33Br) as phase change material, were experimentally studied for laminar flow in a circular tube under constant heat flux. A new expression of Ste is put forward in the paper, according to the physical definition of Stefan number. The results in the experiments show: (a) the dimensionless internal wall temperature of the MPCM suspension is lower than pure water, and the decrease can be up to 30% of that of water; (b) the heat transfer enhancement ratio can be 1.42 times of that of water at x + = 4.2 × 10 −2 for 15.8 wt% MPCM suspension, which is not as much as in some references; and (c) the pump consumption of the MPCM suspension system decrease greatly for the larger heat transfer rate compared with water, due to phase change, the decrease can be up to 67.5% of that of water at q = 750 W (15.8 wt%). The kind of MPCM suspension has good application feasibility in practice.

Convective heat transfer characteristics of microencapsulated phase change material suspensions in minichannels

A comparative experimental study was conducted in order to investigate the convective heat transfer characteristics of water-based suspensions of microencapsulated phase change material (MEPCM) flowing through rectangular copper minichannels. The hydraulic diameter of the channels was 2.71 mm. MEPCM particles with an average size of 4.97 μm were used to form suspensions with mass concentrations ranging from 0 to 20%. The comparative experiments were performed for varying mass flow rates in the laminar region and varying thermal conditions. The cooling performance of the MEPCM suspensions strongly depended on the mass flow rate and the MEPCM mass concentration. The 5% suspension always showed a better cooling performance than water resulting in lower wall temperatures and enhanced heat transfer coefficients within the whole range of mass flow rates. The suspensions with higher mass concentrations, however, were more effective only at low mass flow rates. At higher mass flow rates they showed a less effective cooling performance than water.

Flow frictional characteristics of microencapsulated phase change material suspensions flowing through rectangular minichannels

An experimental investigation was conducted on the laminar flow frictional characteristics of suspensions with microencapsulated phase change material (MEPCM) in water flowing through rectangular copper minichannels. The MEPCM was provided at an average particle size of 4.97 μm, and was mixed with distilled water to form suspen- sions with various mass concentrations ranging from 0 to 20%. The experiment was per- formed to explore the effect of MEPCM mass concentration on friction factor and pressure drop in the minichannels. The Reynolds number ranged from 200 to 2000 to provide laminar and transitional flows. It was found that the experimental data for the suspensions with 0 and 5% concentration agree well with the existing theoretical data for an incom- pressible, fully developed, laminar Newtonian flow. For the suspensions with mass con- centrations higher than 10%, there is an obvious increase in friction factor and pressure drop in comparison with laminar Newtonian flow.

Numerical Analysis of Laminar Forced Convection Heat Transfer in Microencapsulated Phase Change Material Suspensions

Numerical Analysis of Laminar Forced Convection Heat Transfer in Microencapsulated Phase Change Material Suspensions

Novel insight and numerical analysis of convective heat transfer enhancement with microencapsulated phase change material slurries: laminar flow in a circular tube with constant heat flux

This paper presents a novel insight for the forced convective heat transfer enhancement of microencapsulated phase change material slurries flowing through a circular tube with constant heat flux. The influence of various factors is analyzed in detail by using an effective specific heat capacity model, validated with the results available in the literature. It is found that the conventional Nusselt number correlations for internal flow of single phase fluids are not suitable for accurately describing the heat transfer enhancement with microencapsulated phase change material suspensions, and a modification is introduced that enables evaluation for the convective heat transfer of internal flows.

Laminar forced convection heat transfer with phase change material emulsions

Results of an experimental study of laminar forced convection heat transfer in a circular duct with a phase change material emulsion (n-octadecane in water) are presented in this paper. The bulk Stefan numbers considered in this study range up to 3.0 and the concentration of phase change material range up to 30% by volume. The results show that the heat transfer characteristics for phase change material emulsions are similar to those of microencapsulated phase change material suspensions, thus confirming that the microcapsule walls do not affect the heat transfer process significantly.

Analysis of forced convection heat transfer in microencapsulated phase change material suspensions

B = Bi, = C = C* = C = E= = e = Fo = h, = K, = k = L = rn = Nu, = Pe = 4 = R = Rd = Re = r = r* = r,. = r,, = Is1. = Ste = S = T= t = u = 47, = X = X = a = A numerical solution of laminar forced convection heat transfer of a microencapsulated phase change material suspension in a circular tuhe with constant heat flux has been presented in this article. Melting in the microcapsule was solved by a temperature transforming model instead of a quasisteady model. The effects of the microcapsules crust, the initial subcooling, and the width of the phase change temperature range on the variation of the dimensionless tuhe wall temperatures, along the axial direction, were also considered in the present model. The agreement between the present numerical results and the experimental results is very good.

The performance of liquid heat sinks with phase change material suspensions

Results of an experimental study to investigate the performance of liquid heat sinks with microencapsulated phase change material suspensions are presented. The volumetric concentrations of microcapsules in the suspension was varied from 0% to 28%. For the case of heating from below, the use of phase change material suspensions was found to be detrimental to the overall heat transfer because of a reduced convection due to the presence of microcapsules. In contrast, the performance of the liquid heat sink is improved when heating is from above.