Experimental Study of Solar Collector Performance with Serpentine Mini-Channel

الهدف من هذه الدراسة تنفيذ التجريبية للتحقيق في الأداء الحراري للوح مجمع طاقة شمسية يعمل ع اساس قناة مصغرة. لتطبيق المبادلات الحرارية قناة صغيرة، فمن الضروري أن يكون أدوات تصميم مثالية لتنبأ انخفاض الضغط ونقل الحرارة. جميع التجارب العملية اجريت في مدينة بغداد خلال (تموز) عند زاوية ميلان (°30) درجة باتجاه الجنوب تحت ظروف الطقس المشمس. تم استخدام مائع عمل هو بروبلين كلايكول في جريان طباقي خلال تحقق التجارب العملية عند درجة حرارة دخول ثابتة (20) Cº-15)) ولمعدلات تدفق مختلفة (4.6 لتر/ساعة،5.77لتر/ساعة ،7.96لتر/ساعة ،11.2لتر/ساعة و18.35لتر/ساعة). تم تقييم اداء المجمع الشمسي من حيث معامل انتقال الحرارة، انخفاض الضغط، عامل الاحتكاك، طاقة الضخ، وفرق درجات حرارة الدخول والخروج. في هذه الدراسة تم اختبار الجهاز جود طلاء انتقائي وجود غطاء زجاجي بينت النتائج العملية ان زيادة معدل التدفق تؤدي الى زيادة معامل انتقال الحرارة بينما معامل الاحتكاك يقل. ايظا زيادة معدل التدفق تؤدي الى نقصان الفرق درجات الحرارة لمائع العمل بين الدخول والخروج.In this paper, experimental has been executed to investigate thermal performance of modified design of mini-channel plate solar collector. For the application of mini-channel heat exchangers, it is necessary to have perfect design tools for prophesy pressure drop and heat transfer. Experimental setup were carried out in Baghdad city from (July) with a tilt angle of (30º) to the south under sunny weather condition. The working fluid is propylene glycol in the laminar regime is used for experimental investigation at constant fluid inlet temperature (15 ºC - 20 ºC) and at different flow rates (4.6L/h, 5.77L/h, 7.96L/h, 11.2L/h, and 18.35L/h). The mini- channel solar collector performance is evaluated in terms of heat transfer coefficient, pressure drop, friction factor pumping power, and working fluid temperature difference between the outlet and the inlet .In this paper study the test rig with selective coating and with cover glass The experimental results show that an increase in mass flow rate the heat transfer coefficient is also increased while the friction factor is decreased. Also, increase in mass flow rate lead to the temperature difference between the outlet and the inlet working fluid decreases

Heat Transfer Analysis of Modified Solar Collector Plate with Mini-Channel

الهدف من هذه الدراسة تنفيذ التحليلات العملية والعددية للتحقيق في الأداء الحراري للوح مجمع طاقة شمسية يعمل على اساس قناة مصغرة. لتطبيق المبادلات الحرارية قناة صغيرة، فمن الضروري أن يكون أدوات تصميم مثالية لتنبأ انخفاض الضغط ونقل الحرارة. النموذج الرقمي يجمع بين الإشعاع الشمسي مع نقل الحرارة الحمل إلى لوحة امتصاص على أساس قناة صغيرة وكان عدد رينولد يتراوح بين 70 و 300 في معدل تدفق السوائل تراوحت من (4.6 لتر/ساعة الى 18.35 لتر/ساعة) يستخدم للتحقيق التجريبي في درجة حرارة مدخل السائل ( 20 درجة مئوية). كان السائل العامل البروبيلين جلايكول. يتم تقييم أداء قناة تجميع الطاقة الشمسية البسيطة من حيث معامل انتقال الحرارة، عدد نسلت، عامل الاحتكاك وضخ الطاقة. وتكشف النتيجة أنه عندما يكون هناك زيادة في معدل تدفق الكتلة من السائل المتدفق، فإن معامل انتقال الحرارة الحراري يزداد أيضا في حين ينخفض ​​معامل الاحتكاك.In this paper, experimental and numerical analyses have been executed to investigate the thermal performance of modified design of mini-channel plate solar collector. For the application of mini-channel heat exchangers, it is necessary to have perfect design tools for predicting the pressure drop and heat transfer. A numerical model combining solar radiation with convective heat transfer to the absorber plate based on mini-channel has been developed. Reynolds number ranged from 70 to 300 at the fluid flow rate ranged from 4.6 L/h to 18.35 L/h is used for experimental investigation at fluid inlet temperature (20°C); the working fluid is propylene glycol. The mini channel solar collector performance is evaluated in terms of heat transfer coefficient, Nusselt number, friction factor, and pumping power. The result revealed that when there is an increase in the mass flow rate of flowing fluid, the convective heat transfer coefficient is increased, while the friction factor is decreased

SARS-CoV-2 vaccination modelling for safe surgery to save lives: data from an international prospective cohort study

Background: Preoperative SARS-CoV-2 vaccination could support safer elective surgery. Vaccine numbers are limited so this study aimed to inform their prioritization by modelling. Methods: The primary outcome was the number needed to vaccinate (NNV) to prevent one COVID-19-related death in 1 year. NNVs were based on postoperative SARS-CoV-2 rates and mortality in an international cohort study (surgical patients), and community SARS-CoV-2 incidence and case fatality data (general population). NNV estimates were stratified by age (18-49, 50-69, 70 or more years) and type of surgery. Best- and worst-case scenarios were used to describe uncertainty. Results: NNVs were more favourable in surgical patients than the general population. The most favourable NNVs were in patients aged 70 years or more needing cancer surgery (351; best case 196, worst case 816) or non-cancer surgery (733; best case 407, worst case 1664). Both exceeded the NNV in the general population (1840; best case 1196, worst case 3066). NNVs for surgical patients remained favourable at a range of SARS-CoV-2 incidence rates in sensitivity analysis modelling. Globally, prioritizing preoperative vaccination of patients needing elective surgery ahead of the general population could prevent an additional 58 687 (best case 115 007, worst case 20 177) COVID-19-related deaths in 1 year. Conclusion: As global roll out of SARS-CoV-2 vaccination proceeds, patients needing elective surgery should be prioritized ahead of the general population

Pancreatic surgery outcomes: multicentre prospective snapshot study in 67 countries

Background: Pancreatic surgery remains associated with high morbidity rates. Although postoperative mortality appears to have improved with specialization, the outcomes reported in the literature reflect the activity of highly specialized centres. The aim of this study was to evaluate the outcomes following pancreatic surgery worldwide.Methods: This was an international, prospective, multicentre, cross-sectional snapshot study of consecutive patients undergoing pancreatic operations worldwide in a 3-month interval in 2021. The primary outcome was postoperative mortality within 90 days of surgery. Multivariable logistic regression was used to explore relationships with Human Development Index (HDI) and other parameters.Results: A total of 4223 patients from 67 countries were analysed. A complication of any severity was detected in 68.7 percent of patients (2901 of 4223). Major complication rates (Clavien-Dindo grade at least IIIa) were 24, 18, and 27 percent, and mortality rates were 10, 5, and 5 per cent in low-to-middle-, high-, and very high-HDI countries respectively. The 90-day postoperative mortality rate was 5.4 per cent (229 of 4223) overall, but was significantly higher in the low-to-middle-HDI group (adjusted OR 2.88, 95 per cent c.i. 1.80 to 4.48). The overall failure-to-rescue rate was 21 percent; however, it was 41 per cent in low-to-middle-compared with 19 per cent in very high-HDI countries.Conclusion: Excess mortality in low-to-middle-HDI countries could be attributable to failure to rescue of patients from severe complications. The authors call for a collaborative response from international and regional associations of pancreatic surgeons to address management related to death from postoperative complications to tackle the global disparities in the outcomes of pancreatic surgery (NCT04652271; ISRCTN95140761)

Students' participation in collaborative research should be recognised

Letter to the editor

The surgical safety checklist and patient outcomes after surgery: a prospective observational cohort study, systematic review and meta-analysis

© 2017 British Journal of Anaesthesia Background: The surgical safety checklist is widely used to improve the quality of perioperative care. However, clinicians continue to debate the clinical effectiveness of this tool. Methods: Prospective analysis of data from the International Surgical Outcomes Study (ISOS), an international observational study of elective in-patient surgery, accompanied by a systematic review and meta-analysis of published literature. The exposure was surgical safety checklist use. The primary outcome was in-hospital mortality and the secondary outcome was postoperative complications. In the ISOS cohort, a multivariable multi-level generalized linear model was used to test associations. To further contextualise these findings, we included the results from the ISOS cohort in a meta-analysis. Results are reported as odds ratios (OR) with 95% confidence intervals. Results: We included 44 814 patients from 497 hospitals in 27 countries in the ISOS analysis. There were 40 245 (89.8%) patients exposed to the checklist, whilst 7508 (16.8%) sustained ≥1 postoperative complications and 207 (0.5%) died before hospital discharge. Checklist exposure was associated with reduced mortality [odds ratio (OR) 0.49 (0.32–0.77); P\u3c0.01], but no difference in complication rates [OR 1.02 (0.88–1.19); P=0.75]. In a systematic review, we screened 3732 records and identified 11 eligible studies of 453 292 patients including the ISOS cohort. Checklist exposure was associated with both reduced postoperative mortality [OR 0.75 (0.62–0.92); P\u3c0.01; I2=87%] and reduced complication rates [OR 0.73 (0.61–0.88); P\u3c0.01; I2=89%). Conclusions: Patients exposed to a surgical safety checklist experience better postoperative outcomes, but this could simply reflect wider quality of care in hospitals where checklist use is routine

Prospective observational cohort study on grading the severity of postoperative complications in global surgery research

Background The Clavien–Dindo classification is perhaps the most widely used approach for reporting postoperative complications in clinical trials. This system classifies complication severity by the treatment provided. However, it is unclear whether the Clavien–Dindo system can be used internationally in studies across differing healthcare systems in high- (HICs) and low- and middle-income countries (LMICs). Methods This was a secondary analysis of the International Surgical Outcomes Study (ISOS), a prospective observational cohort study of elective surgery in adults. Data collection occurred over a 7-day period. Severity of complications was graded using Clavien–Dindo and the simpler ISOS grading (mild, moderate or severe, based on guided investigator judgement). Severity grading was compared using the intraclass correlation coefficient (ICC). Data are presented as frequencies and ICC values (with 95 per cent c.i.). The analysis was stratified by income status of the country, comparing HICs with LMICs. Results A total of 44 814 patients were recruited from 474 hospitals in 27 countries (19 HICs and 8 LMICs). Some 7508 patients (16·8 per cent) experienced at least one postoperative complication, equivalent to 11 664 complications in total. Using the ISOS classification, 5504 of 11 664 complications (47·2 per cent) were graded as mild, 4244 (36·4 per cent) as moderate and 1916 (16·4 per cent) as severe. Using Clavien–Dindo, 6781 of 11 664 complications (58·1 per cent) were graded as I or II, 1740 (14·9 per cent) as III, 2408 (20·6 per cent) as IV and 735 (6·3 per cent) as V. Agreement between classification systems was poor overall (ICC 0·41, 95 per cent c.i. 0·20 to 0·55), and in LMICs (ICC 0·23, 0·05 to 0·38) and HICs (ICC 0·46, 0·25 to 0·59). Conclusion Caution is recommended when using a treatment approach to grade complications in global surgery studies, as this may introduce bias unintentionally

Critical care admission following elective surgery was not associated with survival benefit: prospective analysis of data from 27 countries

This was an investigator initiated study funded by Nestle Health Sciences through an unrestricted research grant, and by a National Institute for Health Research (UK) Professorship held by RP. The study was sponsored by Queen Mary University of London