PARAMETERS EFFECTS ON CONDUCTION-CONVECTION HEAT TRANSFER IN RECTANGULAR ENCLOSURE SANDWICHED BY FINITE THICKNESS WALLS

The effect of wall heat conduction on natural convection heat transfer in cavities has gained attention of many researchers in recent years due to its wide application areas in engineering such that building heating and cooling and thick enclosures , etc . In this work , we consider a two-dimensional numerical study of a rectangle cavity filled with an air with two vertical conductive walls of finite thickness . The enclosure is subjected to horizontal temperature gradient , the vertical boundaries are isothermal at different temperatures whereas the remaining walls are adiabatic .The theoretical study involved the numerical solution of the Navier-stokes and energy equations by using finite difference method . The stream-vorticity formulation was used in the mathematical model . The physical problem depends on five parameters : Rayleigh number (1000<Ra<1000000) , the Prandtl number (Pr=0.7) , the wall to fluid thermal conductivity ratio (0.1<=Kr<=10) , solid to fluid thickness ratio (0.5<=L1/L2<=1.5) , the ratio of (left or right) solid thickness to the height )(D=L1/H=0.5,0.6667,0.75) and the aspect ratio (H/L= 0.5,1,1.5) . The main focus of the study is on examining the effect of conduction in the wall on the natural convection flow .The results are presented to show the effect of these parameters on the heat transfer and fluid flow characteristics

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)