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
Numerous tribological applications,wherein the use of liquid lubricants is infeasible,require adequate dry lubrication.Despite the use of polymers as an effective solution for dry sliding tribological applications,the...Numerous tribological applications,wherein the use of liquid lubricants is infeasible,require adequate dry lubrication.Despite the use of polymers as an effective solution for dry sliding tribological applications,their poor wear resistance prevents the utilization in harsh industrial environment.Different methods are typically implemented to tackle the poor wear performance of polymers,however sacrificing some of their mechanical/tribological properties.Herein,we discussed the introduction of a novel additive,namely microencapsulated phase change material(MPCM)into an advanced polymeric coating.Specifically,paraffin was encapsulated into melamine-based resin,and the capsules were dispersed in an aromatic thermosetting co-polyester(ATSP)coating.We found that the MPCM-filled composite exhibited a unique tribological behavior,manifested as“zero wear”,and a super-low coefficient of friction(COF)of 0.05.The developed composite outperformed the state-of-the-art polytetrafluoroethylene(PTFE)-filled coatings,under the experimental conditions examined herein.展开更多
The application of phase-change materials (PCM)for thermal-energy storage is hampered by their low thermal conductivity.Copper particles (CP)and copper foam (CF)were used to enhance the thermal conductivity of a micro...The application of phase-change materials (PCM)for thermal-energy storage is hampered by their low thermal conductivity.Copper particles (CP)and copper foam (CF)were used to enhance the thermal conductivity of a microencapsulated phase-change material (MicroPCM).The effects of the CP size and mass fraction and the pore number per inch (PPI)of the CF on the thermal properties of the MicroPCM were investigated.The chemical and microstructures of the MicroPCM and its CP composites were characterized by Fourier transform infrared spectroscopy and scanning electron microscopy,respectively. Their thermal conductivities,phase-change temperatures,and latent heats were measured.Adding CP into the MicroPCM decreased the latent heats with increasing loadings.The thermal conductivities of MicroPCM/CP (Swt%,50nm diameter)and MicroPCM/CF (PPI 30)were 1.12times and 3.46times that of the unmodified MicroPCM at 20℃,respectively.Thermal-energy storage performances of the MicroPCM/CF composites were studied at a power of 2.9±0.1W.The temperature of the contact surfaces of the pure MicroPCM and its composites (PPI 10,PPI 20,PPI 30)was 75.88,51.27,50.52,and 50.23℃,respectively.The composites displayed more uniform temperature distributions.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The authors also acknowledge the use of the Texas A&M Materials Characterization Core Facility(RRID:SCR_022202)We gratefully acknowledge the financial support from the Robert A.WELCH Foundation through the W.T.Doherty-WELCH Chair in Chemistry(A-0001)Mariela VAZQUEZ appreciates the support by the National Science Foundation Graduate Research Fellowship Program(Grant No.M1703014).
文摘Numerous tribological applications,wherein the use of liquid lubricants is infeasible,require adequate dry lubrication.Despite the use of polymers as an effective solution for dry sliding tribological applications,their poor wear resistance prevents the utilization in harsh industrial environment.Different methods are typically implemented to tackle the poor wear performance of polymers,however sacrificing some of their mechanical/tribological properties.Herein,we discussed the introduction of a novel additive,namely microencapsulated phase change material(MPCM)into an advanced polymeric coating.Specifically,paraffin was encapsulated into melamine-based resin,and the capsules were dispersed in an aromatic thermosetting co-polyester(ATSP)coating.We found that the MPCM-filled composite exhibited a unique tribological behavior,manifested as“zero wear”,and a super-low coefficient of friction(COF)of 0.05.The developed composite outperformed the state-of-the-art polytetrafluoroethylene(PTFE)-filled coatings,under the experimental conditions examined herein.
基金National Natural Science Foundation of China (Grant No.U1407125),the Qing Lan Project of Jiangsu Province,the 333High Level Talents Training Project of Jiangsu Province,and the Six Talent Peak High-level Talent Project of Jiangsu Province,China.
文摘The application of phase-change materials (PCM)for thermal-energy storage is hampered by their low thermal conductivity.Copper particles (CP)and copper foam (CF)were used to enhance the thermal conductivity of a microencapsulated phase-change material (MicroPCM).The effects of the CP size and mass fraction and the pore number per inch (PPI)of the CF on the thermal properties of the MicroPCM were investigated.The chemical and microstructures of the MicroPCM and its CP composites were characterized by Fourier transform infrared spectroscopy and scanning electron microscopy,respectively. Their thermal conductivities,phase-change temperatures,and latent heats were measured.Adding CP into the MicroPCM decreased the latent heats with increasing loadings.The thermal conductivities of MicroPCM/CP (Swt%,50nm diameter)and MicroPCM/CF (PPI 30)were 1.12times and 3.46times that of the unmodified MicroPCM at 20℃,respectively.Thermal-energy storage performances of the MicroPCM/CF composites were studied at a power of 2.9±0.1W.The temperature of the contact surfaces of the pure MicroPCM and its composites (PPI 10,PPI 20,PPI 30)was 75.88,51.27,50.52,and 50.23℃,respectively.The composites displayed more uniform temperature distributions.
