As a representative heat recovery device,the fixed-plate enthalpy exchanger possesses the advantages of high recovery effectiveness,low pressure drop,and small space occupied.Still,indoor contaminants may transfer to ...As a representative heat recovery device,the fixed-plate enthalpy exchanger possesses the advantages of high recovery effectiveness,low pressure drop,and small space occupied.Still,indoor contaminants may transfer to fresh air through the enthalpy exchanger simultaneously,causing cross-contamination risk.However,the cross-contamination risk of the fixed-plate enthalpy exchanger has been under-researched in previous studies.As a result,this study experimentally investigates the energy performance,formaldehyde and ammonia transfer rates of paper-based and membrane-based enthalpy exchangers.The results illustrate that the enthalpy recovery effectiveness of the plate exchangers ranges from 60%–85%.The formaldehyde transfer rate through the exchangers varies from 5%–23%,and the ammonia transfer rate is 0–15%.The high effectiveness and low contaminant transfer rates are conducive to the promising application of the fixed-plate enthalpy exchangers.In addition,the energy reclaimed increases with the increase of the absolute indoor-outdoor enthalpy difference.The formaldehyde and ammonia transfer rates and cross-contamination risk slightly decrease with increasing temperature but significantly increase with increasing humidity.Moreover,the experimental results demonstrate that the contaminant transfer rates through the membranebased exchanger are lower than those of the paper-based exchanger.This study provides a reference for the fixed-plate enthalpy exchanger design in practical applications.展开更多
In order to quickly and accurately compute the wall temperature distribution along the combustor axial line, a method to compute the temperature field of combustion chamber with active regeneratively cooling was prese...In order to quickly and accurately compute the wall temperature distribution along the combustor axial line, a method to compute the temperature field of combustion chamber with active regeneratively cooling was presented. On the condition of nonstationary wall temperature, the one-dimensional cooling model based on reference enthalpy was established, and the distribution of the wall heat flux and the wall temperature along the combustor axial line were obtained at different mach numbers by using the heat transfer empirical equation. For the existing two types of cooling system structure, the cooling effectiveness of which was investigated through the presented method. And the satisfactory results obtained show the validity of the method.展开更多
The experimental values of the enthalpy of formation of two isomeric 3,4-and 3,5-dinitro-1-(trinitromethyl)-1H-pyrazoles have been obtained(261.5±5.0and 246.4±6.7kJ/mol for crystalline 3,4-and 3,5-dinitro-1-...The experimental values of the enthalpy of formation of two isomeric 3,4-and 3,5-dinitro-1-(trinitromethyl)-1H-pyrazoles have been obtained(261.5±5.0and 246.4±6.7kJ/mol for crystalline 3,4-and 3,5-dinitro-1-(trinitromethyl)-1H-pyrazoles,respectively).The ballistic effectiveness of these potential oxidizers in composite solid propellants was studied.It is shown that these two oxidizers may be successfully applied in metal-free compositions or with a small content of metal.For the bottom stage 3,4-dinitro-1-(trinitromethyl)-1H-pyrazole is a bit better than 3,5-dinitro-1-(trinitromethyl)-1H-pyrazole,for the upper stage the both oxidizers show the equal ballistic parameters.These oxidizers allow to create metal-free solid composite propellants with the binder percentage not lower than 19%(volume fraction),with I3spequal to 256.5-257.0sat density equal to 1.72-1.74g/cm^3.展开更多
基金supported by the National Key Research and Development Program of China(Grant Nos.2023YFC3807001 and 2023YFC3807101)the National Natural Science Foundation of China(Grant Nos.52394223 and 52278114)Tsinghua University-Architectural Design and Research Institute Joint Research Center for Synergy and Wisdom Creation of Architecture。
文摘As a representative heat recovery device,the fixed-plate enthalpy exchanger possesses the advantages of high recovery effectiveness,low pressure drop,and small space occupied.Still,indoor contaminants may transfer to fresh air through the enthalpy exchanger simultaneously,causing cross-contamination risk.However,the cross-contamination risk of the fixed-plate enthalpy exchanger has been under-researched in previous studies.As a result,this study experimentally investigates the energy performance,formaldehyde and ammonia transfer rates of paper-based and membrane-based enthalpy exchangers.The results illustrate that the enthalpy recovery effectiveness of the plate exchangers ranges from 60%–85%.The formaldehyde transfer rate through the exchangers varies from 5%–23%,and the ammonia transfer rate is 0–15%.The high effectiveness and low contaminant transfer rates are conducive to the promising application of the fixed-plate enthalpy exchangers.In addition,the energy reclaimed increases with the increase of the absolute indoor-outdoor enthalpy difference.The formaldehyde and ammonia transfer rates and cross-contamination risk slightly decrease with increasing temperature but significantly increase with increasing humidity.Moreover,the experimental results demonstrate that the contaminant transfer rates through the membranebased exchanger are lower than those of the paper-based exchanger.This study provides a reference for the fixed-plate enthalpy exchanger design in practical applications.
文摘In order to quickly and accurately compute the wall temperature distribution along the combustor axial line, a method to compute the temperature field of combustion chamber with active regeneratively cooling was presented. On the condition of nonstationary wall temperature, the one-dimensional cooling model based on reference enthalpy was established, and the distribution of the wall heat flux and the wall temperature along the combustor axial line were obtained at different mach numbers by using the heat transfer empirical equation. For the existing two types of cooling system structure, the cooling effectiveness of which was investigated through the presented method. And the satisfactory results obtained show the validity of the method.
基金Ministry of Education and Science of the Russian Federation(14.613.21.0043)
文摘The experimental values of the enthalpy of formation of two isomeric 3,4-and 3,5-dinitro-1-(trinitromethyl)-1H-pyrazoles have been obtained(261.5±5.0and 246.4±6.7kJ/mol for crystalline 3,4-and 3,5-dinitro-1-(trinitromethyl)-1H-pyrazoles,respectively).The ballistic effectiveness of these potential oxidizers in composite solid propellants was studied.It is shown that these two oxidizers may be successfully applied in metal-free compositions or with a small content of metal.For the bottom stage 3,4-dinitro-1-(trinitromethyl)-1H-pyrazole is a bit better than 3,5-dinitro-1-(trinitromethyl)-1H-pyrazole,for the upper stage the both oxidizers show the equal ballistic parameters.These oxidizers allow to create metal-free solid composite propellants with the binder percentage not lower than 19%(volume fraction),with I3spequal to 256.5-257.0sat density equal to 1.72-1.74g/cm^3.
