Nimonic 80A is a nickel-chromium alloy which is strengthened by additions of titanium and aluminium. The alloy is used for high temperature, high strength applications. Wire shaped Nimonic 80A samples are resistively ...Nimonic 80A is a nickel-chromium alloy which is strengthened by additions of titanium and aluminium. The alloy is used for high temperature, high strength applications. Wire shaped Nimonic 80A samples are resistively volume heated as part of a fast capacitor discharge circuit. Time resolved measurements with sub-μs resolution of current through the specimen are performed with a Pearson probe, voltage drop across the specimen is measured with knife-edge contacts and ohmic voltage dividers and the radiance temperature of the sample with a pyrometer. These measurements allow to determine heat of fusion as well as heat capacity and electrical resistivity at initial geometry of Nimonic 80A as a function of temperature in the solid and in the liquid phase up to 2400 K.展开更多
Energy is essential for every human activity for more comfortable life but also consumes more natural resources. In order to control human comfort, temperature usually required when the differences in temperature swin...Energy is essential for every human activity for more comfortable life but also consumes more natural resources. In order to control human comfort, temperature usually required when the differences in temperature swing between indoor and outdoor temperatures. PCMs （phase change materials） are the high latent heat materials which can be used in building materials for energy conservation purpose. PCMs can store thermal energy and also can prevent heat to pass through temperature control areas. Paraffin has been used as PCMs are absorbed into the pore of fly ash as paraffin/fly-ash composite and mixed into the buildings materials. Paraffin is an organic material with high melting point （-59℃）, and nonflammable materials therefore paraffin can be used as the building materials for the function of PCMs for energy saving purposes. Composite PCMs can be prepared by vacuum impregnation process. Paraffin in liquid form will be impregnated into the pore of fly ash by vacuum capillary force to form paraffin/fly ash composite PCMs. Vacuum impregnation pressures, vacuum times, impregnation times of liquid paraffin in fly ash pores and temperatures for melting the solid paraffin into the liquid form are all affect on the thermal properties of paraffin/fly ash composite PCMs. Paraffin or PCMs impregnation are also relate to the physical property including the fractal dimensions of the pores of the fly ash particles and paraffin/fly ash composite PCMs. The fractal dimensions of the pore of fly ash and paraffin/fiy ash composites PCMs are between the values of 1.0 and 2.0. Fractal dimensions of paraffin/fly-ash composite PCMs have the same trend as the thermal properties for heat capacity and latent heat of melting. These fractal dimensions technique is a novel method to measure physical property of building material related to latent heat and heat capacity.展开更多
An experimental investigation was conducted to study the efficiency of thermal insulation of composite PCMs （phase change materials） produced by vacuum impregnation process between paraffin （PCMs） and fly ash part...An experimental investigation was conducted to study the efficiency of thermal insulation of composite PCMs （phase change materials） produced by vacuum impregnation process between paraffin （PCMs） and fly ash particles. DSC （differential scanning calorimeter） has been used to determine the thermal properties of latent heat of melting and heat capacity for composite PCMs. Vacuum impregnation pressure of 40 in.Hg, paraffin melting temperature of 90℃, vacuum time and impregnation time of paraffin of 30 min are the optimum condition of composite PCMs productions. The values of latent heat of melting and heat capacity are 74.00 J/g and 15.726 J/g.℃ for composite PCMs that produces by the optimum condition in vacuum impregnation process. Increasing the amount of composite PCMs replacing for cement in mortars causes the compressive strength, flexural strength and tensile strength reduction. Compressive strength, flexural strength and tensile strength of mortar with and without composite PCMs can be increased by the longer time of water curing for mortar specimens. Thermal conductivity （k） of mortar cement is reduced by increasing the amount of composite PCMs which replaced for cement in mortar plate compositions. Composite PCMs have the efficiency for thermal energy insulation when incorporated into the buildings. Therefore, this property of paraffin/fly ash composites PCMs can reduce the energy consumption for temperature control in the buildings.展开更多
Energy is essential for every human activity for more comfortable life, but it also consumes more natural resources. Fossil fuel is the major energy source for energy consumption, and it also emits a lot of air pollut...Energy is essential for every human activity for more comfortable life, but it also consumes more natural resources. Fossil fuel is the major energy source for energy consumption, and it also emits a lot of air pollution during usage to atmosphere and not reproductively. Electrical energy is the secondary energy sources from fossil fuel which is used to operate air conditioning system. In order to control human comfort temperature, it is usually required when the temperature differences swing between indoor and outdoor temperatures. PCMs （phase change materials） are the high latent heat materials which can be used in building materials for energy conservation purpose. PCMs can store thermal energy and prevent heat to pass through temperature control areas. Paraffin has been used as PCMs which is absorbed into the pore of fly ash as paraffin/fly-ash composite and mixed into the buildings materials. Paraffin is an organic material with high melting point （-59 ~C） and nonflammable material, therefore, it can be used as the building materials for the function of PCMs for energy saving purposes. Composite PCMs can be prepared by vacuum impregnation process. Paraffin in liquid form will be impregnated into the pore of fly ash by vacuum capillary force to form paraffin/fly ash composite PCMs. Vacuum impregnation pressures, vacuum times, impregnation times of liquid paraffin in fly ash pores and temperatures for melting the solid paraffin into the liquid form are all affect on the thermal properties of paraffin/fly ash composite PCMs. Composite PCMs will be selected by the optimum thermal properties with optimum of the production conditions for replace the cement powder in the mortar plate compositions. Cement mortar plate with and without composite PCMs will be tested for the thermal insulation properties by comparison as the real day and night time for 8 h period from spot light turn on and off. Temperature detection on the surface and inside the model building under mortar plate with and without composite PCMs展开更多
Polyethylene glycol(PEG)as phase change material(PCM)and carboxyl-rich carbon(RHTC)with different carboxyl content was introduced to prepare RHTC/PEG composites.The composites have high thermal conductivity,phototherm...Polyethylene glycol(PEG)as phase change material(PCM)and carboxyl-rich carbon(RHTC)with different carboxyl content was introduced to prepare RHTC/PEG composites.The composites have high thermal conductivity,photothermal conversion ability,and improved the phase change enthalpy of the system.The microstructure and thermal properties of the samples were analyzed by various characterization methods.RHTC promoted the benign growth of PEG crystallinity(110.0%),influenced the phase change enthalpy of PEG,and improved the latent heat storage capacity of composites.The non-leakage loading of PEG in the composites can be as high as 97 wt%,and the actual phase change enthalpy is 10.7 J/g higher than that of pure PEG,10%higher than the theoretical value.Owing to the heat storage bridge formed between PEG and RHTC,the thermal conductivity of the composites was up to 0.51 W/mK,which was 99.4%higher than that of PEG.Besides,the introduction of environmentally friendly and low-cost RHTC gives the composites excellent photothermal conversion capability,and its photothermal conversion energy storage efficiency is as high as 90.1%.These results prove that the prepared composites are promising potential candidates in the field of thermal storage and thermal management systems.展开更多
基金This work was financially supported by the Austrian "Forschungsfrderungsgesellschaft mbH", Krntner Strasse 21-23, 1010 Vienna, under contract No. 810999.
文摘Nimonic 80A is a nickel-chromium alloy which is strengthened by additions of titanium and aluminium. The alloy is used for high temperature, high strength applications. Wire shaped Nimonic 80A samples are resistively volume heated as part of a fast capacitor discharge circuit. Time resolved measurements with sub-μs resolution of current through the specimen are performed with a Pearson probe, voltage drop across the specimen is measured with knife-edge contacts and ohmic voltage dividers and the radiance temperature of the sample with a pyrometer. These measurements allow to determine heat of fusion as well as heat capacity and electrical resistivity at initial geometry of Nimonic 80A as a function of temperature in the solid and in the liquid phase up to 2400 K.
文摘Energy is essential for every human activity for more comfortable life but also consumes more natural resources. In order to control human comfort, temperature usually required when the differences in temperature swing between indoor and outdoor temperatures. PCMs （phase change materials） are the high latent heat materials which can be used in building materials for energy conservation purpose. PCMs can store thermal energy and also can prevent heat to pass through temperature control areas. Paraffin has been used as PCMs are absorbed into the pore of fly ash as paraffin/fly-ash composite and mixed into the buildings materials. Paraffin is an organic material with high melting point （-59℃）, and nonflammable materials therefore paraffin can be used as the building materials for the function of PCMs for energy saving purposes. Composite PCMs can be prepared by vacuum impregnation process. Paraffin in liquid form will be impregnated into the pore of fly ash by vacuum capillary force to form paraffin/fly ash composite PCMs. Vacuum impregnation pressures, vacuum times, impregnation times of liquid paraffin in fly ash pores and temperatures for melting the solid paraffin into the liquid form are all affect on the thermal properties of paraffin/fly ash composite PCMs. Paraffin or PCMs impregnation are also relate to the physical property including the fractal dimensions of the pores of the fly ash particles and paraffin/fly ash composite PCMs. The fractal dimensions of the pore of fly ash and paraffin/fiy ash composites PCMs are between the values of 1.0 and 2.0. Fractal dimensions of paraffin/fly-ash composite PCMs have the same trend as the thermal properties for heat capacity and latent heat of melting. These fractal dimensions technique is a novel method to measure physical property of building material related to latent heat and heat capacity.
文摘An experimental investigation was conducted to study the efficiency of thermal insulation of composite PCMs （phase change materials） produced by vacuum impregnation process between paraffin （PCMs） and fly ash particles. DSC （differential scanning calorimeter） has been used to determine the thermal properties of latent heat of melting and heat capacity for composite PCMs. Vacuum impregnation pressure of 40 in.Hg, paraffin melting temperature of 90℃, vacuum time and impregnation time of paraffin of 30 min are the optimum condition of composite PCMs productions. The values of latent heat of melting and heat capacity are 74.00 J/g and 15.726 J/g.℃ for composite PCMs that produces by the optimum condition in vacuum impregnation process. Increasing the amount of composite PCMs replacing for cement in mortars causes the compressive strength, flexural strength and tensile strength reduction. Compressive strength, flexural strength and tensile strength of mortar with and without composite PCMs can be increased by the longer time of water curing for mortar specimens. Thermal conductivity （k） of mortar cement is reduced by increasing the amount of composite PCMs which replaced for cement in mortar plate compositions. Composite PCMs have the efficiency for thermal energy insulation when incorporated into the buildings. Therefore, this property of paraffin/fly ash composites PCMs can reduce the energy consumption for temperature control in the buildings.
文摘Energy is essential for every human activity for more comfortable life, but it also consumes more natural resources. Fossil fuel is the major energy source for energy consumption, and it also emits a lot of air pollution during usage to atmosphere and not reproductively. Electrical energy is the secondary energy sources from fossil fuel which is used to operate air conditioning system. In order to control human comfort temperature, it is usually required when the temperature differences swing between indoor and outdoor temperatures. PCMs （phase change materials） are the high latent heat materials which can be used in building materials for energy conservation purpose. PCMs can store thermal energy and prevent heat to pass through temperature control areas. Paraffin has been used as PCMs which is absorbed into the pore of fly ash as paraffin/fly-ash composite and mixed into the buildings materials. Paraffin is an organic material with high melting point （-59 ~C） and nonflammable material, therefore, it can be used as the building materials for the function of PCMs for energy saving purposes. Composite PCMs can be prepared by vacuum impregnation process. Paraffin in liquid form will be impregnated into the pore of fly ash by vacuum capillary force to form paraffin/fly ash composite PCMs. Vacuum impregnation pressures, vacuum times, impregnation times of liquid paraffin in fly ash pores and temperatures for melting the solid paraffin into the liquid form are all affect on the thermal properties of paraffin/fly ash composite PCMs. Composite PCMs will be selected by the optimum thermal properties with optimum of the production conditions for replace the cement powder in the mortar plate compositions. Cement mortar plate with and without composite PCMs will be tested for the thermal insulation properties by comparison as the real day and night time for 8 h period from spot light turn on and off. Temperature detection on the surface and inside the model building under mortar plate with and without composite PCMs
基金This work was funded and supported by the Liaoning Provincial Education Department Foundation(Nos.LJC201916 and LFW201901)The authors are very grateful to other people for their participation in this work.
文摘Polyethylene glycol(PEG)as phase change material(PCM)and carboxyl-rich carbon(RHTC)with different carboxyl content was introduced to prepare RHTC/PEG composites.The composites have high thermal conductivity,photothermal conversion ability,and improved the phase change enthalpy of the system.The microstructure and thermal properties of the samples were analyzed by various characterization methods.RHTC promoted the benign growth of PEG crystallinity(110.0%),influenced the phase change enthalpy of PEG,and improved the latent heat storage capacity of composites.The non-leakage loading of PEG in the composites can be as high as 97 wt%,and the actual phase change enthalpy is 10.7 J/g higher than that of pure PEG,10%higher than the theoretical value.Owing to the heat storage bridge formed between PEG and RHTC,the thermal conductivity of the composites was up to 0.51 W/mK,which was 99.4%higher than that of PEG.Besides,the introduction of environmentally friendly and low-cost RHTC gives the composites excellent photothermal conversion capability,and its photothermal conversion energy storage efficiency is as high as 90.1%.These results prove that the prepared composites are promising potential candidates in the field of thermal storage and thermal management systems.
