Natural Convective Heat Transfer Characteristics of the Bundle Heat Exchanger in the Latent Heat Microcapsulated Phase Change Material Slurry

As a novel latent functionally thermal fluid, microcapsulated phase change material slurry (MPCMS) has many potential applications in the fields of energy storage, air-conditioning, refrigeration and heat exchanger, etc. In order to investigate the heat storage and heat transfer performance of MPCMS, natural convection in a rectangular enclosure heated by bundle heat exchanger has been studied numerically in this paper. The effects of mass concentration (Cm) of MPCMS, the vertical spaces of bundle heat exchanger on the natural convective heat transfer are investigated. The results indicate that, MPCMS with Cm=30% shows the best natural convectionperformance, and a lower position of bundle heat exchanger can strengthen the natural convection.

Experimental Investigation of Flow and Heat Transfer Characteristics of Latent Functionally Thermal Fluid in Mini-Tube

An experimental research using the latent functionally thermal fluid of n-hexadecane microcapsules in deionized water was conducted in order to investigate the flow and heat transfer characteristics of microencapsulated phase change material (MEPCM) slurry. Experimental measurements were done for a large region of Reynolds number in the mini-tube with a constant wall heat flux. Experimental measurements were also conducted using deionized water as the working fluid under the same conditions. Some important parameters such as pressure, temperatures of wall and fluid were obtained experimentally. The relationships between pressure drop and mass flow rate, dimensionless outlet temperature of working fluid and Reynolds number, mean convective heat transfer coefficient and Nusselt number and Reynolds number were obtained. Results show that the using of MEPCM particle increases the pressure drop and then close to that of single phase water with increasing mass flow rate. The outlet and wall temperatures decrease 50% comparing with single phase water under the same conditions. The Nusselt number of slurry containing small concentration MEPCM particle is about 2.0–2.3 times greater than that of single phase water in the minitube. The experimental data might be helpful in the design of thermal-energy transportation systems in small scale using MEPCM slurry.

Preparation and Thermal Property of Phase Change Material Microcapsules by Phase Separation

Compared to conventional single-phase fluids, the latent functionally thermal fluid (LFTF), with phase change particles of μm magnitude in size dispersed in it, shows much greater apparent specific heat and heat transfer rate between the fluid and the duct wall. Therefore, for given heat transportation quantity, the mass flow rate and the pump consumption can be reduced greatly. Due to these, LFTF is a promising material in the fields of heat exchanging. In this paper, phase change material (n-tetradecane) was encapsulated by polymethyl mathacrylate (PMMA), polystyrene (PS) and blend of them by internal phase separation method to form microcapsule of 1~2μm in size. The chemical structures were demonstrated by using Fourier transform infrared spectroscopy (FTIR). The core-shell structure was observed using phase contrast microscope. Differential scanning calometry (DSC) results indicated that the phase change enthalpy of the containing 75wt% n-tetradecane as core material reaches 150.7 J/g.