Microencapsulation phase change material slurry(MEPCMS) becomes a potential working fluid for cooling high energy density miniaturized components,thanks to the latent heat absorption of particles in the heat transfer ...Microencapsulation phase change material slurry(MEPCMS) becomes a potential working fluid for cooling high energy density miniaturized components,thanks to the latent heat absorption of particles in the heat transfer process.In this work,the Discrete Phase Model(DPM) based on the Euler-Lagrangian method is used to numerically investigate the convective heat transfer characteristics of MEPCMS flowing through a rectangular minichannel with constant heat flux.The results show that particles of MEPCMS are mainly subjected to drag force during the flow.Even so,they can migrate from the high-temperature region to the low-temperature region driven by the thermophoretic force,affecting the particle distribution and phase change process.Moreover,the Nux of the MEPCMS fluctuates due to particle phase change with varying specific heat capacities.Specifically,the value increases first,then decreases,and eventually increases again until it approaches the fully developed value of the pure base fluid as the particles gradually melt.Furthermore,the heat transfer performance of the MEPCMS is influenced by the combination of fluid inlet temperature fluid inlet velocity(v),and mass concentration(c_(m)) of MEPCM particles.The result shows that the maximum reduction of the maximum bottom wall temperature difference(ΔT_(w)) is 23.98% at T_(in)=293.15 K,v=0.15 m·s^(-1),c_(m)=10%.展开更多
Due to its core phase change characteristics,microencapsulated phase change material(MPCM)can make many base fluids have better heat transfer characteristics.In this paper,the flow boiling heat transfer characteristic...Due to its core phase change characteristics,microencapsulated phase change material(MPCM)can make many base fluids have better heat transfer characteristics.In this paper,the flow boiling heat transfer characteristics of fluorinated liquid-based microencapsulated phase change material suspension(MPCMS)through vertical transparent quartz channel were studied.The effects of MPCM core phase change temperature and suspension flow velocity on boiling heat transfer coefficient and critical heat flux were discussed,respectively.The results show that the appropriate concentration of MPCMS can enhance both the boiling heat transfer coefficient and the critical heat flux.The strengthening effect becomes weak with the increase of suspension flow velocity.The maximum strengthening rates of critical heat flux appear at 0.05 m/s,which are 25%(MPCMS(70℃)),16%(MPCMS(58℃))and 10%(MPCMS(28℃)).The phase change temperature of the MPCM core has important effects on the boiling heat transfer coefficient and the critical heat flux.The results showed that the MPCM with core phase change temperature higher than the boiling temperature of base fluid has the best enhancement effect.Different bubble behavior in vertical tube with different heat flux can be observed by high-speed photography system.The particle core phase change in MPCMS inhibits the aggregation of bubbles and forms many small bubbles to enhance heat transfer.The work lays a foundation for further exploring the industrial application of MPCMS.展开更多
This short communication reports our recent work on the synthesis and characterisation ofmicrocapsules of phase change materials using silica as the shell material through a one-step method. The method uses no surfact...This short communication reports our recent work on the synthesis and characterisation ofmicrocapsules of phase change materials using silica as the shell material through a one-step method. The method uses no surfactants or dispersants for stabilising the capsules. The results show that the one-step method allows the tuning of the size and polydispersity of the capsules, and the use of different core materials. Analyses of the capsules show that they contain about 65% phase change materials. The results also suggest no need for a stabilising agent due to self-stabilisation by the amine groups. Further work is underway to investigate the mechanical and thermal properties of the microcapsules and the scale-up of the method.展开更多
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. ...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.展开更多
基金the financial support of the National Natural Science Foundation of China (No.U20A20299)the Natural Science Foundation of Guangdong Province (No.2019A1515012119)。
文摘Microencapsulation phase change material slurry(MEPCMS) becomes a potential working fluid for cooling high energy density miniaturized components,thanks to the latent heat absorption of particles in the heat transfer process.In this work,the Discrete Phase Model(DPM) based on the Euler-Lagrangian method is used to numerically investigate the convective heat transfer characteristics of MEPCMS flowing through a rectangular minichannel with constant heat flux.The results show that particles of MEPCMS are mainly subjected to drag force during the flow.Even so,they can migrate from the high-temperature region to the low-temperature region driven by the thermophoretic force,affecting the particle distribution and phase change process.Moreover,the Nux of the MEPCMS fluctuates due to particle phase change with varying specific heat capacities.Specifically,the value increases first,then decreases,and eventually increases again until it approaches the fully developed value of the pure base fluid as the particles gradually melt.Furthermore,the heat transfer performance of the MEPCMS is influenced by the combination of fluid inlet temperature fluid inlet velocity(v),and mass concentration(c_(m)) of MEPCM particles.The result shows that the maximum reduction of the maximum bottom wall temperature difference(ΔT_(w)) is 23.98% at T_(in)=293.15 K,v=0.15 m·s^(-1),c_(m)=10%.
基金This work was supported by the Scientific Instrument Developing Project of the Chinese Academy of Sciences(Grant No.YJKYYQ20200016)the National Natural Science Foundation of China(Grant No.52106117).
文摘Due to its core phase change characteristics,microencapsulated phase change material(MPCM)can make many base fluids have better heat transfer characteristics.In this paper,the flow boiling heat transfer characteristics of fluorinated liquid-based microencapsulated phase change material suspension(MPCMS)through vertical transparent quartz channel were studied.The effects of MPCM core phase change temperature and suspension flow velocity on boiling heat transfer coefficient and critical heat flux were discussed,respectively.The results show that the appropriate concentration of MPCMS can enhance both the boiling heat transfer coefficient and the critical heat flux.The strengthening effect becomes weak with the increase of suspension flow velocity.The maximum strengthening rates of critical heat flux appear at 0.05 m/s,which are 25%(MPCMS(70℃)),16%(MPCMS(58℃))and 10%(MPCMS(28℃)).The phase change temperature of the MPCM core has important effects on the boiling heat transfer coefficient and the critical heat flux.The results showed that the MPCM with core phase change temperature higher than the boiling temperature of base fluid has the best enhancement effect.Different bubble behavior in vertical tube with different heat flux can be observed by high-speed photography system.The particle core phase change in MPCMS inhibits the aggregation of bubbles and forms many small bubbles to enhance heat transfer.The work lays a foundation for further exploring the industrial application of MPCMS.
基金supported by UK EPSRC under grants EP/F023014/1 and EP/F000464/1a collaborative research fund from the Institute of Process Engineering of Chinese Academy of Sciences
文摘This short communication reports our recent work on the synthesis and characterisation ofmicrocapsules of phase change materials using silica as the shell material through a one-step method. The method uses no surfactants or dispersants for stabilising the capsules. The results show that the one-step method allows the tuning of the size and polydispersity of the capsules, and the use of different core materials. Analyses of the capsules show that they contain about 65% phase change materials. The results also suggest no need for a stabilising agent due to self-stabilisation by the amine groups. Further work is underway to investigate the mechanical and thermal properties of the microcapsules and the scale-up of the method.
基金partly supported by Deutscher Akademischer Austausch Dienst(German DAAD scholarship),Chinese Scholarship Councilthe National Natural Science Foundation of China(Grant Nos.50436020 and 50176004).
文摘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.
