English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

This paper mainly makes introduction about microencapsulated phase change material slurry (MPCMS).Microencapsulated phase change material slurry (MPCS ) can serve as both the heat transfer fluids and energy storage media, consequently, they are potentially applicable to the thermal systems. The preparations, thermal properties and several correlations of heat transfer in laminar flow of MEPCMS are also listed. In addition, it is found that the main influence factors for heat transfer effective is the bulk Stefan number. Introduction In the last 40 years, lots of efforts have been made to enhance the energy storage capacity of structural material for solar and building applications by integrating the PCM directly into the other materials, e.g. wallboard, concrete blocks, under floor heating system, etc.[1] However, the thermal performances of such applications are not significant due to the low thermal conductivity of PCM [2]. Several methods for generating PCM particles have been investigated for various thermal-energy applications. In recent years, a new approach was proposed, in which the phase change material was microencapsulated and suspended in a single-phase heat transfer fluid to form microencapsulated phase change material (MPCM) slurry [3]. These suspensions benefit from a number of special features including (a) relatively low variations in operating temperatures of systems using such fluids due to energy absorption at approximately constant temperature, (b) lower pumping power requirements due to the increased heat capacity [4], (c) high heat transfer rates to the phase change material due to large surface area to volume ratio, (d) the enhanced thermal conductivity of slurry leading to increased heat transfer to the suspension [5], and (e) the reduction/elimination of incongruent melting and phase separation[6]This paper presents a review of the research progress on MPCS as the heat-transfer fluids in laminar convection heat transfer..The review has been arranged into some sections including: the features of MPCM, the main parameters for heat transfer and the equation. Microencapsulated phase change material slurry (MPCS) Microencapsulation is a kind of tiny particles (about 0.1–100 μm diameter) in which the core material is enveloped by a thin layer of shell. There are several methods which can be used to produce microencapsulated particles, such as spray-drying and coacervation. Figure 1 is a photomicrograph of the MCPCM particles made by different methods. It can be seen from the surface morphology that the shape of MPCM is uniformly spherical and the surface is very smooth without edges and dents, which implies that fluidity is good if the MPCM is dispersed into the carrier fluids, such as water. When the MPCM is dispersed into the carrier fluid, e.g. water, a kind of suspension named as microencapsulated phase change slurry (MPCS) is formed. During the fabrication process, an appropriate amount of surfactants are normally used for helping MPCM well disperse into the carrier fluid and increase the lifetime of MPCS [7]. In comparison of conventional phase change International Conference on Information Sciences, Machinery, Materials and Energy (ICISMME 2015) © 2015. The authors Published by Atlantis Press 1798 material slurries (PCS), better heat transfer performance can be achieved due to the relatively large surface area to volume of MPCM. Therefore, MPCS can be used as both thermal energy storage and heat transfer media. Fig. 1. Typical SEM pictures of MPCM made by different methods [3]. (a) By spray-drying and (b) by coacervation. Thermal and physical properties of MPCS The thermal and physical properties of MPCS are very different from those the MEPCM materials and carrier fluids. Due to the relatively large surface area to volume of MPCM, better heat transfer performance can be achieved. Thus, MPCS can serve as both the energy storage and heat transfer media, in addition, the agglomeration of MPCM can be avoided due to the encapsulation. It is obvious that, however, the heat transfer and fluid flow characteristics are very important for the MPCS system design. Due to the relatively large surface area to volume of MPCM, better heat transfer performance can be achieved. The thermal conductivity of the microcapsule was calculated based on the composite sphere approach[8], as follows: 1 kpdp = 1 kcdc + dp-dc kwdpdc (1) where kp is the thermal conductivity of the MPCM particle and kw the thermal conductivity of the water. The thermal conductivity of the static MPCS with low volume fraction can be evaluated by Maxwell’s equation formulate as kkss = kkff × 2kkff+kkpp+2∅(kkpp−kkff) 2kkff+kkpp−∅(kkpp−kkff) (2) where ks and kf are the thermal conductivities of the bulk slurry and carrier fluid, and f is the volume fraction of MPCM. The thermal conductivity of the MPCM particle kp can be estimated by a correlation describing composite sphere feature [9]. Due to the interaction between the particle and fluid the effective thermal conductivity is generally higher than that predicted by Maxwell’s equation. Then, a general correlation summarized can be applied depending on the particle Peclet number kkee kkss = 1 + BB∅ (3) where ke is the effective thermal conductivity of the MPCS, PPPPpp = PP ∙ dd/ααffis the particle Peclet number, PP is the shear rate, αff is the thermal diffusivity, and the values for B and m depend on the particle Peclet number The viscosity of MPCS is important in determining the pressure drop. Yamagishi et al. [10] indicated that the MPCS showed the Newtonian fluid feature and the apparent viscosity was about 1.5–10 times of the water as the mass fraction of MPCM increased from about 5 to 30%. Vand et al.[11] uses the following equation to estimate the viscosity of the slurry. μμss μμff = (1 − ∅ − A∅2)−2.5 (4) where A is a parameter depending on the shape and rigidity of the particles.

Review of Laminar Convection Heat-Transfer with Microencapsulated Phase Change Material Slurry