An investigation on the post-CHF heat transfer in a electrically heated coil with horizontal helix axis is reported. The wall temperature varies with different circumferential locations, having a higher value at the i...An investigation on the post-CHF heat transfer in a electrically heated coil with horizontal helix axis is reported. The wall temperature varies with different circumferential locations, having a higher value at the inside surface (the suxface closest to the coil axis).Based on the experimental results, the correlation of post-CHF heat transfer coefficient of the coil is obtained. The average heat transfer coefficient is larger with the coil than with straight tubes.展开更多
在大破口失水事故最佳估算加不确定性分析中，再淹没临界后传热模型的不确定性评价研究十分关键。本文针对RELAP5再淹没临界后传热模型展开研究，选取Weisman在0.1～0.4 MPa条件下进行的圆管过渡沸腾试验数据对再淹没过渡沸腾关系式进...在大破口失水事故最佳估算加不确定性分析中，再淹没临界后传热模型的不确定性评价研究十分关键。本文针对RELAP5再淹没临界后传热模型展开研究，选取Weisman在0.1～0.4 MPa条件下进行的圆管过渡沸腾试验数据对再淹没过渡沸腾关系式进行评价，选取爱达荷国家实验室（IN EL ）低压下的圆管膜态沸腾试验数据对再淹没膜态沸腾关系式进行评价，给出其概率分布类型和范围，为进行大破口失水事故不确定性分析打下基础。展开更多
为了探究浮升力效应对超临界水传热性能的影响,本文建立了一个预测垂直上升光管内超临界水传热的3-D数值模型。利用该数值模型预测了系统压力为25 MPa,质量流速为600~800 kg·m^(-2)·s^(-1),内壁热负荷为400~500 k W·m^(...为了探究浮升力效应对超临界水传热性能的影响,本文建立了一个预测垂直上升光管内超临界水传热的3-D数值模型。利用该数值模型预测了系统压力为25 MPa,质量流速为600~800 kg·m^(-2)·s^(-1),内壁热负荷为400~500 k W·m^(-2)条件下超临界水的传热。分析了热负荷和质量流速对浮升力效应的影响,同时分析了浮升力效应对传热性能的影响规律。结果表明,当质量流速为800 kg·m^(-2)·s^(-1)时,浮升力效应导致了局部传热恶化,传热恶化发生后,传热系数迅速回升;而质量流速为600kg·m^(-2)·s^(-1)时,浮升力效应对传热性能的影响与热负荷有关。当质量流速为600 kg·m^(-2)·s^(-1),热负荷为400 k W·m^(-2)时,超临界水传热表现为传热强化;当质量流速为600 kg·m^(-2)·s^(-1),热负荷为500 k W·m^(-2)时,浮升力效应导致了局部传热恶化,传热恶化发生后,传热系数没有回升。展开更多
Green manufacturing （GM） and high efficiency machining technology are inevitable trends in the field of advanced manufacturing of the 21st century. To ensure green and high-efficiency machining, a new high efficienc...Green manufacturing （GM） and high efficiency machining technology are inevitable trends in the field of advanced manufacturing of the 21st century. To ensure green and high-efficiency machining, a new high efficiency cooling technology-cryogenic pneumatic mist jet impinging cooling （CPMJI） technology is presented. For obtaining the best cooling effect, a little quantity of coolant is carried by high speed cryogenic air （-20 C ） and reaches the machining zone in the form of mist jet to enhance heat transfer. Experimental results indicate that under the conditions of 40 m/s in the jet impinging speed and 10 mm in the jet impinging distance, the critical heat flux（CHF） nearly reaches 6× 10^7 W/m^2, more than six times of the CHF of the grinding burn with a value of （8～10）×10^6 W/m^2.展开更多
Under ultra-supercritical pressure, the heat transfer characteristics of water in vertical upward 4- head internally ribbed tubes with a diameter of 28.65mm and thickness of 8mm were experimentally studied. The experi...Under ultra-supercritical pressure, the heat transfer characteristics of water in vertical upward 4- head internally ribbed tubes with a diameter of 28.65mm and thickness of 8mm were experimentally studied. The experiments were performed at P = 25- 34MPa, G = 450- 1800kg/（m^2·s） and q = 200 600kW/m^2. The results show that the pressure has only a moderate effect on the heat transfer of uhra-supercritical water when the water temperature is below the pseudocritical point. Sharp rise of the wall temperature near the pesudocritical region occurs earlier at a higher pressure. Increasing the mass velocity improves the heat transfer with a much stronger effect below the pesudocritical point than that above the pesudocritical point. For given pressure and mass velocity, the inner wall heat flux also shows a significant effect on the inner wall temperature, with a higher inner wall heat flux leading to a higher inner wall temperature. Increasing of inner wall heat flux leads to an early occurrence of sharp rise of the wall temperature. Correlations of heat transfer coefficients are also presented for vertical upward internally ribbed tubes.展开更多
Transient heat transfer has been experimentally investigated for subcooled water jet impingement quenching of a hot rotating stainless steel cylinder. Temperatures beneath the impinged surface were measured during que...Transient heat transfer has been experimentally investigated for subcooled water jet impingement quenching of a hot rotating stainless steel cylinder. Temperatures beneath the impinged surface were measured during quenching and used to estimate surface temperature and surface heat flux by using a developed numerical inverse solution of heat conduction. Heat flux reached its maximum value just after the WF （wetting front） （visible leading edge of boiling region） started moving from stagnation towards the circumferential region. WF moved in a non-uniform manner in angular direction on the hot rotating surface. With the increase of surface velocity, heat flux decreased. Higher surface velocity moved away the produced vapor bubbles and reduced the solid-liquid contact time which made it one-dimensional heat conduction from multi-dimensional, that reduced heat flux. The generated boiling curve from the estimated heat flux showed a reasonable agreement with existing studies. The surface maximum heat flux （maximum value in each cycle） distribution trend with radial position is entirely comparable with the static surface critical heat flux in literature. An explosive to a sheet like flow patterns were observed with the decrease of surface temperature. The flow patterns were followed by the intensity of sound during quenching.展开更多
Numerical studies under supercritical pressure are carried out to study the heat transfer characteristics in a single-root coolant channel of the active regenerative cooling system of the scramjet engine, using actual...Numerical studies under supercritical pressure are carried out to study the heat transfer characteristics in a single-root coolant channel of the active regenerative cooling system of the scramjet engine, using actual physical properties of pentane. The relationships between wall temperature and inlet temperature, mass flow rate, wall heat flux, inlet pressure, as well as center stream temperature are obtained. The results suggest that the heat transfer deterioration occurs when the fuel temperature approaches the pseudo-critical temperature, and the wall temperature increases rapidly and heat transfer coefficient decreases sharply. The decrease of wall heat flux, as well as the increase of mass flow rate and inlet pressure makes the starting point of the heat transfer deterioration and the peak point of the wall temperature move backward. The wall temperature increment induced by heat transfer deterioration decreases, which could reduce the severity of the heat transfer deterioration. The relational expression of the heat transfer deterioration critical heat flux derives from the relationship of the mass flow rate and the inlet pressure.展开更多
文摘An investigation on the post-CHF heat transfer in a electrically heated coil with horizontal helix axis is reported. The wall temperature varies with different circumferential locations, having a higher value at the inside surface (the suxface closest to the coil axis).Based on the experimental results, the correlation of post-CHF heat transfer coefficient of the coil is obtained. The average heat transfer coefficient is larger with the coil than with straight tubes.
文摘在大破口失水事故最佳估算加不确定性分析中，再淹没临界后传热模型的不确定性评价研究十分关键。本文针对RELAP5再淹没临界后传热模型展开研究，选取Weisman在0.1～0.4 MPa条件下进行的圆管过渡沸腾试验数据对再淹没过渡沸腾关系式进行评价，选取爱达荷国家实验室（IN EL ）低压下的圆管膜态沸腾试验数据对再淹没膜态沸腾关系式进行评价，给出其概率分布类型和范围，为进行大破口失水事故不确定性分析打下基础。
文摘为了探究浮升力效应对超临界水传热性能的影响,本文建立了一个预测垂直上升光管内超临界水传热的3-D数值模型。利用该数值模型预测了系统压力为25 MPa,质量流速为600~800 kg·m^(-2)·s^(-1),内壁热负荷为400~500 k W·m^(-2)条件下超临界水的传热。分析了热负荷和质量流速对浮升力效应的影响,同时分析了浮升力效应对传热性能的影响规律。结果表明,当质量流速为800 kg·m^(-2)·s^(-1)时,浮升力效应导致了局部传热恶化,传热恶化发生后,传热系数迅速回升;而质量流速为600kg·m^(-2)·s^(-1)时,浮升力效应对传热性能的影响与热负荷有关。当质量流速为600 kg·m^(-2)·s^(-1),热负荷为400 k W·m^(-2)时,超临界水传热表现为传热强化;当质量流速为600 kg·m^(-2)·s^(-1),热负荷为500 k W·m^(-2)时,浮升力效应导致了局部传热恶化,传热恶化发生后,传热系数没有回升。
文摘Green manufacturing （GM） and high efficiency machining technology are inevitable trends in the field of advanced manufacturing of the 21st century. To ensure green and high-efficiency machining, a new high efficiency cooling technology-cryogenic pneumatic mist jet impinging cooling （CPMJI） technology is presented. For obtaining the best cooling effect, a little quantity of coolant is carried by high speed cryogenic air （-20 C ） and reaches the machining zone in the form of mist jet to enhance heat transfer. Experimental results indicate that under the conditions of 40 m/s in the jet impinging speed and 10 mm in the jet impinging distance, the critical heat flux（CHF） nearly reaches 6× 10^7 W/m^2, more than six times of the CHF of the grinding burn with a value of （8～10）×10^6 W/m^2.
基金Supported by the High Technology Research and Development Programme of China （No. 2002AA526012 ）and the National Natural Science Foundation of China （No. 50323001）.
文摘Under ultra-supercritical pressure, the heat transfer characteristics of water in vertical upward 4- head internally ribbed tubes with a diameter of 28.65mm and thickness of 8mm were experimentally studied. The experiments were performed at P = 25- 34MPa, G = 450- 1800kg/（m^2·s） and q = 200 600kW/m^2. The results show that the pressure has only a moderate effect on the heat transfer of uhra-supercritical water when the water temperature is below the pseudocritical point. Sharp rise of the wall temperature near the pesudocritical region occurs earlier at a higher pressure. Increasing the mass velocity improves the heat transfer with a much stronger effect below the pesudocritical point than that above the pesudocritical point. For given pressure and mass velocity, the inner wall heat flux also shows a significant effect on the inner wall temperature, with a higher inner wall heat flux leading to a higher inner wall temperature. Increasing of inner wall heat flux leads to an early occurrence of sharp rise of the wall temperature. Correlations of heat transfer coefficients are also presented for vertical upward internally ribbed tubes.
文摘Transient heat transfer has been experimentally investigated for subcooled water jet impingement quenching of a hot rotating stainless steel cylinder. Temperatures beneath the impinged surface were measured during quenching and used to estimate surface temperature and surface heat flux by using a developed numerical inverse solution of heat conduction. Heat flux reached its maximum value just after the WF （wetting front） （visible leading edge of boiling region） started moving from stagnation towards the circumferential region. WF moved in a non-uniform manner in angular direction on the hot rotating surface. With the increase of surface velocity, heat flux decreased. Higher surface velocity moved away the produced vapor bubbles and reduced the solid-liquid contact time which made it one-dimensional heat conduction from multi-dimensional, that reduced heat flux. The generated boiling curve from the estimated heat flux showed a reasonable agreement with existing studies. The surface maximum heat flux （maximum value in each cycle） distribution trend with radial position is entirely comparable with the static surface critical heat flux in literature. An explosive to a sheet like flow patterns were observed with the decrease of surface temperature. The flow patterns were followed by the intensity of sound during quenching.
基金the funding supports from National Natural Science Foundation of China (Grant No.51076035 and No.11079017), HIT.NSRIF.2008. 24
文摘Numerical studies under supercritical pressure are carried out to study the heat transfer characteristics in a single-root coolant channel of the active regenerative cooling system of the scramjet engine, using actual physical properties of pentane. The relationships between wall temperature and inlet temperature, mass flow rate, wall heat flux, inlet pressure, as well as center stream temperature are obtained. The results suggest that the heat transfer deterioration occurs when the fuel temperature approaches the pseudo-critical temperature, and the wall temperature increases rapidly and heat transfer coefficient decreases sharply. The decrease of wall heat flux, as well as the increase of mass flow rate and inlet pressure makes the starting point of the heat transfer deterioration and the peak point of the wall temperature move backward. The wall temperature increment induced by heat transfer deterioration decreases, which could reduce the severity of the heat transfer deterioration. The relational expression of the heat transfer deterioration critical heat flux derives from the relationship of the mass flow rate and the inlet pressure.
