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
Objective: To evaluate the effectiveness and safety of Chinese medicine(CM) in the treatment of coronavirus disease 2019(COVID-19) in China. Methods: A multi-center retrospective cohort study was carried out, with cum...Objective: To evaluate the effectiveness and safety of Chinese medicine(CM) in the treatment of coronavirus disease 2019(COVID-19) in China. Methods: A multi-center retrospective cohort study was carried out, with cumulative CM treatment period of 3 days during hospitalization as exposure. Data came from consecutive inpatients from December 19, 2019 to May 16, 2020 in 4 medical centers in Wuhan, China. After data extraction, verification and cleaning, confounding factors were adjusted by inverse probability of treatment weighting(IPTW), and the Cox proportional hazards regression model was used for statistical analysis. Results:A total of 2,272 COVID-19 patients were included. There were 1,684 patients in the CM group and 588 patients in the control group. Compared with the control group, the hazard ratio(HR) for the deterioration rate in the CM group was 0.52 [95% confidence interval(CI): 0.41 to 0.64, P<0.001]. The results were consistent across patients of varying severity at admission, and the robustness of the results were confirmed by 3 sensitivity analyses. In addition, the HR for all-cause mortality in the CM group was 0.29(95% CI: 0.19 to 0.44, P<0.001).Regarding of safety, the proportion of patients with abnormal liver function or renal function in the CM group was smaller. Conclusion: This real-world study indicates that the combination of a full-course CM therapy on the basic conventional treatment, may safely reduce the deterioration rate and all-cause mortality of COVID-19patients. This result can provide the new evidence to support the current treatment of COVID-19. Additional prospective clinical trial is needed to evaluate the efficacy and safety of specific CM interventions.(Registration No. ChiCTR2200062917)展开更多
为了深入理解火箭发动机再生冷却过程中碳氢燃料的流动传热规律,采用RNG k-ε湍流模型结合增强壁面处理方法对非对称受热(上壁面外侧加热)方形冷却通道内超临界压力甲烷的对流换热进行了数值研究。重点考察了加热壁面内侧的传热恶化以...为了深入理解火箭发动机再生冷却过程中碳氢燃料的流动传热规律,采用RNG k-ε湍流模型结合增强壁面处理方法对非对称受热(上壁面外侧加热)方形冷却通道内超临界压力甲烷的对流换热进行了数值研究。重点考察了加热壁面内侧的传热恶化以及由传热恶化和固壁热传导共同作用引起的热流异常传递现象,拟合得到了传热恶化的临界热流密度和起始内壁温关系式、加热侧内壁面和侧壁面内侧平均热流密度的预测关系式。结果表明:当外壁热流密度和质量流速比值高于0.288 k J/kg时,近壁流体流动加速诱发了加热侧内壁面的传热恶化;同时,固体区域温度畸变导致加热侧内壁面热流密度减小,热流更多地向侧壁面内侧传导。运行压力越低,该现象越显著。展开更多
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.
基金Supported by the Innovation Team Project of the State Administration of Traditional Chinese Medicine(No.ZYYCXTD-D-202201)。
文摘Objective: To evaluate the effectiveness and safety of Chinese medicine(CM) in the treatment of coronavirus disease 2019(COVID-19) in China. Methods: A multi-center retrospective cohort study was carried out, with cumulative CM treatment period of 3 days during hospitalization as exposure. Data came from consecutive inpatients from December 19, 2019 to May 16, 2020 in 4 medical centers in Wuhan, China. After data extraction, verification and cleaning, confounding factors were adjusted by inverse probability of treatment weighting(IPTW), and the Cox proportional hazards regression model was used for statistical analysis. Results:A total of 2,272 COVID-19 patients were included. There were 1,684 patients in the CM group and 588 patients in the control group. Compared with the control group, the hazard ratio(HR) for the deterioration rate in the CM group was 0.52 [95% confidence interval(CI): 0.41 to 0.64, P<0.001]. The results were consistent across patients of varying severity at admission, and the robustness of the results were confirmed by 3 sensitivity analyses. In addition, the HR for all-cause mortality in the CM group was 0.29(95% CI: 0.19 to 0.44, P<0.001).Regarding of safety, the proportion of patients with abnormal liver function or renal function in the CM group was smaller. Conclusion: This real-world study indicates that the combination of a full-course CM therapy on the basic conventional treatment, may safely reduce the deterioration rate and all-cause mortality of COVID-19patients. This result can provide the new evidence to support the current treatment of COVID-19. Additional prospective clinical trial is needed to evaluate the efficacy and safety of specific CM interventions.(Registration No. ChiCTR2200062917)
基金Project supported by the National Natural Science Foundation of China(No.51210011)the Natural Science Foundation of Zhejiang Province(No.LZ13E060001),China
文摘为了深入理解火箭发动机再生冷却过程中碳氢燃料的流动传热规律,采用RNG k-ε湍流模型结合增强壁面处理方法对非对称受热(上壁面外侧加热)方形冷却通道内超临界压力甲烷的对流换热进行了数值研究。重点考察了加热壁面内侧的传热恶化以及由传热恶化和固壁热传导共同作用引起的热流异常传递现象,拟合得到了传热恶化的临界热流密度和起始内壁温关系式、加热侧内壁面和侧壁面内侧平均热流密度的预测关系式。结果表明:当外壁热流密度和质量流速比值高于0.288 k J/kg时,近壁流体流动加速诱发了加热侧内壁面的传热恶化;同时,固体区域温度畸变导致加热侧内壁面热流密度减小,热流更多地向侧壁面内侧传导。运行压力越低,该现象越显著。
