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
本文对大温度滑移非共沸工质CO_(2)/R152a在内径2 mm的水平小通道内流动沸腾换热特性进行了实验研究。实验工况范围为质量流速200~400 kg·m^(-2)·s^(-1)、热流密度12~36 k W/m^(2)、饱和温度5~15℃。结果表明管内流动沸腾两...本文对大温度滑移非共沸工质CO_(2)/R152a在内径2 mm的水平小通道内流动沸腾换热特性进行了实验研究。实验工况范围为质量流速200~400 kg·m^(-2)·s^(-1)、热流密度12~36 k W/m^(2)、饱和温度5~15℃。结果表明管内流动沸腾两相流型包括泡状流、塞状流、弹状流、分层波状流、环状流以及雾状流。对流换热系数随干度增加呈先缓慢增加后迅速下降的趋势,沸腾过程中存在临界干度。随着热流密度、质量流速以及饱和温度的增加,大温度滑移非共沸工质对流换热系数均呈现增加趋势。大温度滑移非共沸工质CO_(2)/R152a对流换热系数随温度滑移的减小而增大。考虑大温度滑移非共沸工质传热传质过程中的显热换热阻力和传质阻力影响,提出了新的换热系数预测模型,平均绝对偏差为22.05%。展开更多
Considerable progress has been made over the last decades in the management of acute respiratory distress syndrome(ARDS).Mechanical ventilation(MV)remains the cornerstone of supportive therapy for ARDS.Lung-protective...Considerable progress has been made over the last decades in the management of acute respiratory distress syndrome(ARDS).Mechanical ventilation(MV)remains the cornerstone of supportive therapy for ARDS.Lung-protective MV minimizes the risk of ventilator-induced lung injury(VILI)and improves survival.Several parame-ters contribute to the risk of VILI and require careful setting including tidal volume(V_(T)),plateau pressure(P_(plat)),driving pressure(ΔP),positive end-expiratory pressure(PEEP),and respiratory rate.Measurement of energy and mechanical power allows quantification of the relative contributions of various parameters(V_(T),P_(plat),ΔP,PEEP,respiratory rate,and airflow)for the individualization of MV settings.The use of neuromuscular blocking agents mainly in cases of severe ARDS can improve oxygenation and reduce asynchrony,although they are not known to confer a survival benefit.Rescue respiratory therapies such as prone positioning,inhaled nitric oxide,and extracorporeal support techniques may be adopted in specific situations.Furthermore,respiratory weaning protocols should also be considered.Based on a review of recent clinical trials,we present 10 golden rules for individualized MV in ARDS management.展开更多
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.
文摘本文对大温度滑移非共沸工质CO_(2)/R152a在内径2 mm的水平小通道内流动沸腾换热特性进行了实验研究。实验工况范围为质量流速200~400 kg·m^(-2)·s^(-1)、热流密度12~36 k W/m^(2)、饱和温度5~15℃。结果表明管内流动沸腾两相流型包括泡状流、塞状流、弹状流、分层波状流、环状流以及雾状流。对流换热系数随干度增加呈先缓慢增加后迅速下降的趋势,沸腾过程中存在临界干度。随着热流密度、质量流速以及饱和温度的增加,大温度滑移非共沸工质对流换热系数均呈现增加趋势。大温度滑移非共沸工质CO_(2)/R152a对流换热系数随温度滑移的减小而增大。考虑大温度滑移非共沸工质传热传质过程中的显热换热阻力和传质阻力影响,提出了新的换热系数预测模型,平均绝对偏差为22.05%。
基金This work was funded by the Brazilian Council for Scien-tific and Technological Development(COVID-19-CNPq)Rio de Janeiro State Research Foundation(COVID-19-FAPERJ)+2 种基金Fund-ing Authority for Studies and Projects(FINEP)Brazilian Ministry of Science,TechnologyInformation COVID-19 Network(RedeVírus MCTI).
文摘Considerable progress has been made over the last decades in the management of acute respiratory distress syndrome(ARDS).Mechanical ventilation(MV)remains the cornerstone of supportive therapy for ARDS.Lung-protective MV minimizes the risk of ventilator-induced lung injury(VILI)and improves survival.Several parame-ters contribute to the risk of VILI and require careful setting including tidal volume(V_(T)),plateau pressure(P_(plat)),driving pressure(ΔP),positive end-expiratory pressure(PEEP),and respiratory rate.Measurement of energy and mechanical power allows quantification of the relative contributions of various parameters(V_(T),P_(plat),ΔP,PEEP,respiratory rate,and airflow)for the individualization of MV settings.The use of neuromuscular blocking agents mainly in cases of severe ARDS can improve oxygenation and reduce asynchrony,although they are not known to confer a survival benefit.Rescue respiratory therapies such as prone positioning,inhaled nitric oxide,and extracorporeal support techniques may be adopted in specific situations.Furthermore,respiratory weaning protocols should also be considered.Based on a review of recent clinical trials,we present 10 golden rules for individualized MV in ARDS management.
