Hydration heat effect of cement pastes and mechanism of hydroxypropyl methyl cellulose ether （HPMC） and expanded perlite in cement pastes were studied by means of hydration exothermic rate, hydration heat amount, FT...Hydration heat effect of cement pastes and mechanism of hydroxypropyl methyl cellulose ether （HPMC） and expanded perlite in cement pastes were studied by means of hydration exothermic rate, hydration heat amount, FTIR and TG-DTG. The results show that HPMC can significantly delay the hydration induction period and acceleration period of cement pastes. As mixing amount increased, hydration induction period of cement pastes enlarged and accelerated period gradually went back. At the same time, the amount of hydration heat gradually decreased. Expanded perlite had worse delay effects and less change of hydration heat amount of cement pastes than HPMC. HPMC changed the structure of C-S-H during cement hydration. The more amount of HPMC, the more obvious effect. However, EXP had little influence on the structure of C-S-H. At the same age, the content of Ca （OH）2 in cement pastes gradually decreased as the mixing amount increase of HPMC and expanded perlite, and had better delay effect than that single-doped with HPMC or expanded perlite when HPMC and expanded nerlite were both dooed in cement pastes.展开更多
Adhesives are used to bond various substrates such as metals, polymers, ceramics, rubber, wood and wood-based products. The use of adhesive as bonding agent rather than mechanical fasteners like nails results in the p...Adhesives are used to bond various substrates such as metals, polymers, ceramics, rubber, wood and wood-based products. The use of adhesive as bonding agent rather than mechanical fasteners like nails results in the potential for reduced cost and weight of assemblies. However, adhesives are unprotected to a wide range of conditions, such as thermo-mechanical cycling in the environment, creep and fatigue imposed by structural joint configurations, and residual stress due to mismatch of thermal expansion between adhesives and objects. Thus, there will be a need for development of new chemistries and processes for easy repair and reprocessing of bonded structures are becoming of current great interest for the industries. In some cases, to improve the protection of various items/objects during handling and transportation, currently used protective products such as padded wraps, envelopes, packages and containers need to be modified. One technology which can solve the problem is the adhesives modified with thermally expandable particles (TEPs) which can be dismounted by heating the joint in a few seconds. The expandable composition is providing the necessary protective insulation and cushioning required in packages and containers. This paper reviews the application of unexpanded microspheres in the adhesive segment.展开更多
With increasing awareness of energy conservation and environmental protection, the Organic Rankine Cycle (ORC) system has gained significant attention. This technology enables the recovery of industrial waste heat, wa...With increasing awareness of energy conservation and environmental protection, the Organic Rankine Cycle (ORC) system has gained significant attention. This technology enables the recovery of industrial waste heat, waste incineration heat, and renewable energy sources such as geothermal heat, biomass energy, and solar energy at lower temperatures. However, the low-grade heat source utilized in ORC systems faces a challenge to achieving high power generation efficiency and output power. Therefore, enhancing the power generation capacity of ORC systems is a key research focus in this field. An entranced heat exchanger ORC system with the screw expander driven by the low-temperature heat source is established to investigate the relevant performance. Hot water temperature from 77°C to 132°C is adopted for performance analysis, while the environmental temperature is approximately 25°C. Refrigerant R245fa is selected as the working fluid, and the screw expander is employed for power generation. It is worth noting that the entranced heat exchanger ORC system has significant potential for low-temperature heat recovery. Experimental results indicate that the maximum power output is 12.83 kW, which is obtained at around 105°C hot water inlet temperature. Correspondingly, the average power output remains 11.75 kW, revealing the system’s high stability for power generation. The implementation of a plate heat exchanger for enhanced heat transfer has enabled a 50% reduction in system size compared to traditional shell-tube type ORC systems. Besides, economic calculations demonstrate substantial benefits associated with the ORC system. The calculations indicate an internal benefit of 560,000 RMB/year, accompanied by notable external benefits such as an energy saving and emission reduction potential of up to 784 t CO2 per year. Moreover, the payback period is 2.23 years. It shows a remarkable improvement in terms of performance and excellent economic benefits. As a result, the novel ORC presents a promising alternative for low-grade heat utilization as compared to conventional small-scale ORC systems.展开更多
CO2 is a safe natrual refrigerant which had been and will be widely used in air condi-tioning and heat pump systems. The thernodynamic analysis of the CO2 transcritical cycleis presented in this paper. The result show...CO2 is a safe natrual refrigerant which had been and will be widely used in air condi-tioning and heat pump systems. The thernodynamic analysis of the CO2 transcritical cycleis presented in this paper. The result shows that the CO2 cycles offers heat recovery benefitas a heat pump system. It is possible that the COP value of CO2 cycle can compete withthose of R22 or R134a if two stage compression system or an expander system are used.展开更多
基金Funded by the National Natural Science Foundation of China(No.50902107)National Science and Technology Supporting Program (No.2011BAJ04B02)the Fundamental Research Funds for the Central Universities (No.2011-YB-03)
文摘Hydration heat effect of cement pastes and mechanism of hydroxypropyl methyl cellulose ether （HPMC） and expanded perlite in cement pastes were studied by means of hydration exothermic rate, hydration heat amount, FTIR and TG-DTG. The results show that HPMC can significantly delay the hydration induction period and acceleration period of cement pastes. As mixing amount increased, hydration induction period of cement pastes enlarged and accelerated period gradually went back. At the same time, the amount of hydration heat gradually decreased. Expanded perlite had worse delay effects and less change of hydration heat amount of cement pastes than HPMC. HPMC changed the structure of C-S-H during cement hydration. The more amount of HPMC, the more obvious effect. However, EXP had little influence on the structure of C-S-H. At the same age, the content of Ca （OH）2 in cement pastes gradually decreased as the mixing amount increase of HPMC and expanded perlite, and had better delay effect than that single-doped with HPMC or expanded perlite when HPMC and expanded nerlite were both dooed in cement pastes.
文摘Adhesives are used to bond various substrates such as metals, polymers, ceramics, rubber, wood and wood-based products. The use of adhesive as bonding agent rather than mechanical fasteners like nails results in the potential for reduced cost and weight of assemblies. However, adhesives are unprotected to a wide range of conditions, such as thermo-mechanical cycling in the environment, creep and fatigue imposed by structural joint configurations, and residual stress due to mismatch of thermal expansion between adhesives and objects. Thus, there will be a need for development of new chemistries and processes for easy repair and reprocessing of bonded structures are becoming of current great interest for the industries. In some cases, to improve the protection of various items/objects during handling and transportation, currently used protective products such as padded wraps, envelopes, packages and containers need to be modified. One technology which can solve the problem is the adhesives modified with thermally expandable particles (TEPs) which can be dismounted by heating the joint in a few seconds. The expandable composition is providing the necessary protective insulation and cushioning required in packages and containers. This paper reviews the application of unexpanded microspheres in the adhesive segment.
文摘With increasing awareness of energy conservation and environmental protection, the Organic Rankine Cycle (ORC) system has gained significant attention. This technology enables the recovery of industrial waste heat, waste incineration heat, and renewable energy sources such as geothermal heat, biomass energy, and solar energy at lower temperatures. However, the low-grade heat source utilized in ORC systems faces a challenge to achieving high power generation efficiency and output power. Therefore, enhancing the power generation capacity of ORC systems is a key research focus in this field. An entranced heat exchanger ORC system with the screw expander driven by the low-temperature heat source is established to investigate the relevant performance. Hot water temperature from 77°C to 132°C is adopted for performance analysis, while the environmental temperature is approximately 25°C. Refrigerant R245fa is selected as the working fluid, and the screw expander is employed for power generation. It is worth noting that the entranced heat exchanger ORC system has significant potential for low-temperature heat recovery. Experimental results indicate that the maximum power output is 12.83 kW, which is obtained at around 105°C hot water inlet temperature. Correspondingly, the average power output remains 11.75 kW, revealing the system’s high stability for power generation. The implementation of a plate heat exchanger for enhanced heat transfer has enabled a 50% reduction in system size compared to traditional shell-tube type ORC systems. Besides, economic calculations demonstrate substantial benefits associated with the ORC system. The calculations indicate an internal benefit of 560,000 RMB/year, accompanied by notable external benefits such as an energy saving and emission reduction potential of up to 784 t CO2 per year. Moreover, the payback period is 2.23 years. It shows a remarkable improvement in terms of performance and excellent economic benefits. As a result, the novel ORC presents a promising alternative for low-grade heat utilization as compared to conventional small-scale ORC systems.
文摘CO2 is a safe natrual refrigerant which had been and will be widely used in air condi-tioning and heat pump systems. The thernodynamic analysis of the CO2 transcritical cycleis presented in this paper. The result shows that the CO2 cycles offers heat recovery benefitas a heat pump system. It is possible that the COP value of CO2 cycle can compete withthose of R22 or R134a if two stage compression system or an expander system are used.
