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This study aims to solve the freezing problem of the 5 mm water layer remaining in the upper water chamber after elf-weight drainage of the tube and fin heat exchanger in the low-temperature wind tunnel under low-temperature operating conditions. Under the conditions that the hot air temperature inside and outside the tube are 10-70 °C and the inlet air speed s 2.78-10.56 m/s, two types of tube (elliptical tube and aluminum flat tube) and fin heat exchangers are tested and studied or drying the water layer remaining in the upper water chamber after self-weight drainage. The influence of the hot air inside and hot air outside the tube drying methods on the drying rate of the two heat exchangers are compared and analyzed. The results show that: the drying rate of aluminum flat tube heat exchanger is faster, so as the hot air outside the tube drying method; the heat exchanger drying time decrease with the increase of the inlet air speed and the drying time saves 50.75% at he inlet air speed of 10.56 m/s compared to 2.78 m/s. The empirical relationship equation for the drying rate was fitted by he experimental data, and the average error between the fitted results and the experimental measurements was less than 6.1%, which has a good prediction capability for the hot air drying rate of the tube-fin heat exchanger in the low-temperature wind tunnel. [ABSTRACT FROM AUTHOR]

Coal-fired power plants remain a significant source of CO 2 emission, NH 3 /coal co-firing in existing coal-fired boilers can rapidly and effectively reduce CO 2 emissions. However, the unique physicochemical properties of NH 3 result in unstable combustion and high NO x emissions. Superfine pulverized coal combustion and moderate or intense low-oxygen dilution (MILD) combustion are two advanced technologies with stable combustion and low NO x emissions. This study systematically investigated the coupling of these two technologies in NH 3 /coal co-combustion. Results show that the synergistic effect of superfine pulverized coal and MILD combustion ensures stable NH 3 /coal flame propagation, with a shorter lift-off distance and a higher peak temperature (70 K–100 K increase) under higher NH 3 blending ratio (NBR) conditions. As the NBR increases from 0 to 40 cal%, the maximum Da s-O2 for the superfine particles (18 μm) decreases from 0.55 to 0.49, while for normal particles (125 μm), it decreases from 3.9 to 3.4. The combustion state of superfine particles more easily approaches the MILD combustion state. The value of R char-H2O /R char-CO2 increases from 0.64 to 1.93, indicating the C Char -H 2 O reaction dominates the char gasification behavior. Compared to that for normal particles, the NO emission concentrations for superfine particles combustion at 0, 10 cal% and 20 cal% NBR were reduced by 48 %, 64 % and 47 %, respectively. These findings provide new insights and theoretical guidance for stable combustion and low NO x emissions of NH 3 /coal co-firing. [Display omitted] • Coupling MILD with superfine particle combustion in NH 3 /coal co-firing is proposed. • The combustion state of the superfine particle is closer to the MILD regime. • C Char -H 2 O reaction dominates the char gasification behaviors at high NBRs. • The NO emission of superfine particles are lower than those for normal particles. [ABSTRACT FROM AUTHOR]

Background: Glucocorticoids are often used to treat acute respiratory distress syndrome (ARDS) and novel coronavirus disease 2019 (COVID-19). However, the efficacy and safety of glucocorticoids in the treatment of ARDS caused by COVID-19 are still controversial; therefore, we conducted this meta-analysis of the literature on this topic., Methods: Four databases (PubMed, EMBASE, Cochrane Library, and Web of Science) were searched from the establishment of the databases to August 16, 2023. Randomized controlled trials (RCTs) and cohort studies that compared glucocorticoid versus standard treatment for ARDS caused by COVID-19 were included. The Newcastle-Ottawa Scale (NOS) checklist and the Cochrane Handbook for Systematic Reviews of Interventions were used to evaluate the risk of bias. Review Manager 5.4 software and STATA 17.0 were used for meta-analy-sis, and the relative risk (RR), mean difference, and 95% confidence intervals (CIs) were then determined. Results: A total of 17 studies involving 8592 patients were evaluated, including 14 retrospective studies and 3 RCTs. Sixteen studies reported data on all-cause mortality. The results of the meta-analysis showed that glucocorticoids did not reduce all-cause (RR, 0.96; 95% CI 0.82-1.13, P = .62) or 28-day (RR, 1.01; 95% CI 0.78-1.32, P = .93) mortality. Subgroup analysis showed that only methylprednisolone reduced all-cause mortality. No matter whether glucocorticoid use was early or delayed, high-dose or low-dose, long-term or short-term, no regimen reduced all-cause mortality. Furthermore, there were no significant differences in length of intensive care unit (ICU) stay, length of hospital stay, hyperglycemia, and ventilator-associated pneumonia (VAP); how-ever, glucocorticoids increased the number of ventilator-free days., Conclusions: Although methylprednisolone may reduce all-cause mortality from ARDS caused by COVID-19, this effect was not found with other types of glucocorticoids. At the same time, glucocorticoid use was associ-ated with more ventilator-free days, without increasing the incidence of hyperglycemic events or VAP. Con-sidering that almost all of the included studies were retrospective cohort studies, more RCTs are needed to confirm these findings.

Background: This study explored the efficacy of hydrocortisone combined with vitamin C and thiamine (HVT) in the treatment of sepsis/septic shock., Methods: PubMed, EMBASE and Web of Science were searched (establishment of the database to October 31, 2022). The meta-analysis included randomized controlled trials (RCTs); comparing the efficacy of HVT regimen and placebo in the treatment of sepsis/septic shock. The Cochrane Handbook for Systematic Reviews of Interventions was used to assess the risk of bias. The Review Manager 5.4 software was used for meta-analysis, and the relative risk (RR), mean difference (MD) and 95% confidence intervals (CI) were then determined. Trial sequential analysis (TSA) was then conducted., Results: Eight RCTs with 1,572 patients were identified. Meta-analysis showed that HVT regimen did not reduce all-cause (RR=0.96, 95% CI: 0.83 - 1.11, P=0.60), hospital (RR=1.03, 95% CI: 0.83 - 1.27, P=0.80) or intensive care unit (ICU) mortalities (RR=1.05, 95% CI: 0.86 - 1.28, P=0.65). Furthermore, there was no significant difference in the change of sequential organ failure assessment score, length of ICU stay, length of hospital stay, duration of the use of vasopressors, incidence of acute kidney injury and ventilator-free days between HVT and control groups. TSA showed that more trials are needed to confirm the results., Conclusions: HVT regimen did not reduce the mortality of patients with sepsis/septic shock and was not associated with a significant improvement in outcomes. The TSA result showed that more RCTs with high quality and large sample sizes are needed to further confirm the results.