Incorporating microencapsulated phase change materials (MPCM) into mortar enhances building thermal energy storage for energy savings but severely degrades compressive strength by replacing sand and creating pores. Th...Incorporating microencapsulated phase change materials (MPCM) into mortar enhances building thermal energy storage for energy savings but severely degrades compressive strength by replacing sand and creating pores. This study innovatively addresses this critical limitation by introducing nano-silicon (NS) as a modifier to fill pores and promote hydration in MPCM mortar. Twenty-five mixes with varying NS content from 0 to 4 weight percent and different MPCM contents were comprehensively tested for flowability, compressive strength, thermal conductivity, thermal energy storage via Differential Scanning Calorimetry, and microstructure via Scanning Electron Microscopy. Key quantitative results showed MPCM reduced mortar consistency while NS had minimal effect. Crucially, although MPCM decreased compressive strength, NS addition significantly counteracted this loss. Increasing NS content from 0 percent to 4 percent enhanced compressive strength by 12.53%, 14.21%, 25.49%, 21.70%, and 40.70%, respectively, across the tested MPCM levels. Thermal conductivity was primarily reduced by higher MPCM content leading to lower conductivity, with NS showing negligible and inconsistent influence. The phase change temperature of the modified mortar matched that of pure MPCM, although its relative latent heat slightly decreased. This work conclusively demonstrates the novel and effective use of nano-silicon, achieving up to a 40.7 percent strength recovery in MPCM mortar while preserving its essential phase change temperature and thermal conductivity reduction capability. This strategy presents a feasible pathway for developing high-performance, energy-efficient building composites.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
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 paper presents a novel concept for designing solar-absorbing metamaterial microcapsules of phase change materials(PCMs)integrated with thermo-regulating smart textiles intended for coats or garments,especially fo...This paper presents a novel concept for designing solar-absorbing metamaterial microcapsules of phase change materials(PCMs)integrated with thermo-regulating smart textiles intended for coats or garments,especially for wear in space or cold weather on earth.The metamaterial is a periodically nanostructured metal-dielectric-metal thin film and can acquire surface plasmons to trap or absorb solar energy at subwavelength scales.This kind of metamaterial microencapsulation is not only able to take advantage of latent heat that can be stored or released from the PCMs over a tunable temperature range,but also has other advantages over conventional polymer microencapsulation of PCMs,such as enhanced thermal conductivity,improved flame-retardant capabilities,and usage as an extra solar power resource.The thermal analysis for this kind of microencapsulation has been done and can be used as a guideline for designing integrated thermo-regulating smart textiles in the future.These metamaterial microcapsules may open up new routes to enhancing thermo-regulating textiles with novel properties and added value.展开更多
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
基金supported by the Fujian Provincial Department of Science and Technology Industrial University Industry.Education Cooperation Project(2022H6009)the Fujian Province Key Project of Science and Technology Innovation(2022G02025).
文摘Incorporating microencapsulated phase change materials (MPCM) into mortar enhances building thermal energy storage for energy savings but severely degrades compressive strength by replacing sand and creating pores. This study innovatively addresses this critical limitation by introducing nano-silicon (NS) as a modifier to fill pores and promote hydration in MPCM mortar. Twenty-five mixes with varying NS content from 0 to 4 weight percent and different MPCM contents were comprehensively tested for flowability, compressive strength, thermal conductivity, thermal energy storage via Differential Scanning Calorimetry, and microstructure via Scanning Electron Microscopy. Key quantitative results showed MPCM reduced mortar consistency while NS had minimal effect. Crucially, although MPCM decreased compressive strength, NS addition significantly counteracted this loss. Increasing NS content from 0 percent to 4 percent enhanced compressive strength by 12.53%, 14.21%, 25.49%, 21.70%, and 40.70%, respectively, across the tested MPCM levels. Thermal conductivity was primarily reduced by higher MPCM content leading to lower conductivity, with NS showing negligible and inconsistent influence. The phase change temperature of the modified mortar matched that of pure MPCM, although its relative latent heat slightly decreased. This work conclusively demonstrates the novel and effective use of nano-silicon, achieving up to a 40.7 percent strength recovery in MPCM mortar while preserving its essential phase change temperature and thermal conductivity reduction capability. This strategy presents a feasible pathway for developing high-performance, energy-efficient building composites.
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.
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.
文摘This paper presents a novel concept for designing solar-absorbing metamaterial microcapsules of phase change materials(PCMs)integrated with thermo-regulating smart textiles intended for coats or garments,especially for wear in space or cold weather on earth.The metamaterial is a periodically nanostructured metal-dielectric-metal thin film and can acquire surface plasmons to trap or absorb solar energy at subwavelength scales.This kind of metamaterial microencapsulation is not only able to take advantage of latent heat that can be stored or released from the PCMs over a tunable temperature range,but also has other advantages over conventional polymer microencapsulation of PCMs,such as enhanced thermal conductivity,improved flame-retardant capabilities,and usage as an extra solar power resource.The thermal analysis for this kind of microencapsulation has been done and can be used as a guideline for designing integrated thermo-regulating smart textiles in the future.These metamaterial microcapsules may open up new routes to enhancing thermo-regulating textiles with novel properties and added value.
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%.
