Development and performance evaluation of locally fabricated thermal conductivity apparatus

This paper presents the design and construction of a Guarded Hot Plate (GHP) apparatus for the accurate assessment of thermal conductivities of some Nigerian local building materials. The GHP apparatus is a steady-state measurement device. This apparatus is designed to measure the thermal conductivities of masonry building materials of different compositions. The design features included hot and cold plates fabricated with aluminum plates of 6 mm thickness and varying dimensions; the guard plates also made of aluminum, but of 6.35 mm thickness, forms a rigid enclosure for the specimen all encased in a mild steel housing. The operating measuring temperature range is from -20 for varying specimen thickness up to 60mm. Results are presented for concrete, laterite, and a mixture of cement with laterite, clay, and sand respectively, and it covers a range of thermal conductivities of 0.77W/mK to 1.80 W/mK. Moisture effect on concrete was recorded for the lightweight concrete as the thermal conductivity value reduced from 1.80W/m.K to 1.32W/m.K for the oven-dried concrete sample over a 1.5% (by weight) reduction in water content. The performance evaluation of the locally fabricated GHP apparatus showed a 3.03% percentage difference over ASHRAE’s published data on oven-baked concrete thermal conductivitie

Laminar Forced Convective Heat Transfer and Fluid Flow in a Finned Cylindrical Annulus

The purpose of this paper is to numerically investigate the effects of some geometric parameters and flow variables on heat transfer augmentation in annuli with equi-spaced internal longitudinal fins along the external walls. A fully developed flow and a constant thermal boundary condition of uniform heat flux at the walls of the pipe were assumed. Continuity, momentum and energy transport equations were adopted for the solutions of the problem. A Q-BASIC code was written based on the finite difference scheme generated. Numerical experiments were conducted to ascertain the effects of Reynolds number Re, radius ratio, R.R, Prandtl number Pr, fin height H, and pipe inclination, on the rate of heat transfer and fluid flow. The results obtained show that for 50 ≤ Re ≤ 500, total Nusselt number NuT increases with increase in Re while for Re > 500, there was no significant increase in NuT. Nusselt number, average velocity and bulk temperature of the fluid increase with increasingin the range 0° ≤ ≤ 75° but for the range 75°≤  ≤ 90°  the effect is negligible. For R.R > 0.6, the heat transfer was observed to be almost independent of R; therefore for economic purposes, heat exchangers similar to the configuration studied should be run at a low pumping power. A numerical study was done to validate the program by test running it for the finless annuli for similar boundary conditions; the results obtained in the present work show the same trend as that of Kakac and Yucel

Numerical Analysis of Natural Convection in a Concentric Trapezoidal Enclosure Filled with a Porous Medium

The natural convection around a heated trapezoidal block of different sizes positioned centrically in a larger trapezium has been investigated numerically. The annulus between the trapeziums is occupied by porous media. The sides of the inner trapezium are heated to a fixed temperature and the slanted walls of the outer trapezium are isolated thermally. In contrast, its upper and lower walls are heated uniformly. The pertinent dimensionless equations were solved with COMSOL Multiphysics 5.6. The parameters considered are modified Rayleigh number, Darcy number, and area ratio. The results of this study are shown as isothermal contours, stream functions, and average Nusselt number. The results show that increasing the modified Rayleigh number improves heat transfer; however, the response of the thermal profiles to area ratio increment depends on the range of Darcy number considered. This study finds application in ingot treatments and microchannel cooling, among others

Improving agricultural efficiency with solar-powered tractors and magnetohydrodynamic entropy generation in copper–silver nanofluid flow

This study examines the impact of solar-powered tractor on agricultural productivity and energy efficiency. The implementation of solar energy in tractors has the potential to reduce dependence on non-renewable energy sources, minimize carbon emissions, and promote sustainable farming practices. This research investigates the reduction of energy consumption and enhancement of productivity by evaluating magnetohydrodynamic (MHD) entropy production through the flow of nanofluids containing copper-engine oil (Cu-EO) and silver-engine oil (Ag-EO). The study also evaluates the effectiveness of thermal transport in solar-powered tractors through several properties such as solar thermal radiation, viscous dissipation, slippery velocity, and porous media. The investigation analyzed the thermodynamics of entropy generation in a non-Newtonian Williamson nanofluid, with the aim of assessing its energy equilibrium and the effects of diverse physical parameters. In order to enable numerical investigation, similarity variables were implemented to transform partial differential equations into ordinary differential equations, and the Chebyshev collocation spectral method was applied to solve the governing equations. It has been revealed that the Williamson nanofluid have a smoother flow compared to the mixture fluid. Furthermore, Williamson-nanofluid demonstrate superior thermal conductivity and heat transfer characteristics compared to the base fluid, making them appropriate for utilization in cooling systems and heat exchangers in various industries. The boundary layer exhibits the maximum temperature while employing lamina-shaped particles, whilst the lowest temperature is shown when utilizing spherical-shaped nanoparticles. The Ag-EO nanofluid an efficiency rate of approximately 2.64 % with a minimum efficiency rate of 3.22 %. The findings will help develop eco-friendly agricultural methods that promote economic development while mitigating harm to the environment

Magnetoconvection around an elliptic cylinder placed in a lid-driven square enclosure subjected to internal heat generation or absorption

The impacts of MHD and heat generation/absorption on lid-driven convective fluid flow occasioned by a lid-driven square enclosure housing an elliptic cylinder have been investigated numerically. The elliptic cylinder and the horizontal enclosure boundaries were insulated and the left vertical lid-driven wall was experienced at a fixed hot temperature, and the right wall was exposed to a fixed cold temperature. COMSOL Multiphysics 5.6 software was used to resolve the nondimensional equations governing flow physics. A set of parameters, such as Hartmann number ( 0≤≤50 ), Reynolds number ( 102≤≤103 ), Grashof number ( 102≤≤105 ), heat generation-absorption parameter ( −3≤≤3 ), and elliptical cylinder aspect ratio (AR) ( 1.0≤≤3.0 ) have been investigated. The current study discovered that for low Reynolds number, the adiabatic cylinder AR of 2.0 provided the optimum heat transfer enhancement for the model investigated, also the impact of cylinder size diminishes beyond Gr = 104. But for high Reynolds (Re = 1000), the size of the cylinder with AR = 3.0 offered the highest heat transfer augmentation. The clockwise flow circulation reduces because of an increase in AR, which hinders the flow circulation. In addition, heat absorption supports heat transfer augmentation while heat generation can suppress heat transfer improvement

Adaptation of the Wound Healing Questionnaire universal-reporter outcome measure for use in global surgery trials (TALON-1 study): mixed-methods study and Rasch analysis

BackgroundThe Bluebelle Wound Healing Questionnaire (WHQ) is a universal-reporter outcome measure developed in the UK for remote detection of surgical-site infection after abdominal surgery. This study aimed to explore cross-cultural equivalence, acceptability, and content validity of the WHQ for use across low- and middle-income countries, and to make recommendations for its adaptation.MethodsThis was a mixed-methods study within a trial (SWAT) embedded in an international randomized trial, conducted according to best practice guidelines, and co-produced with community and patient partners (TALON-1). Structured interviews and focus groups were used to gather data regarding cross-cultural, cross-contextual equivalence of the individual items and scale, and conduct a translatability assessment. Translation was completed into five languages in accordance with Mapi recommendations. Next, data from a prospective cohort (SWAT) were interpreted using Rasch analysis to explore scaling and measurement properties of the WHQ. Finally, qualitative and quantitative data were triangulated using a modified, exploratory, instrumental design model.ResultsIn the qualitative phase, 10 structured interviews and six focus groups took place with a total of 47 investigators across six countries. Themes related to comprehension, response mapping, retrieval, and judgement were identified with rich cross-cultural insights. In the quantitative phase, an exploratory Rasch model was fitted to data from 537 patients (369 excluding extremes). Owing to the number of extreme (floor) values, the overall level of power was low. The single WHQ scale satisfied tests of unidimensionality, indicating validity of the ordinal total WHQ score. There was significant overall model misfit of five items (5, 9, 14, 15, 16) and local dependency in 11 item pairs. The person separation index was estimated as 0.48 suggesting weak discrimination between classes, whereas Cronbach's α was high at 0.86. Triangulation of qualitative data with the Rasch analysis supported recommendations for cross-cultural adaptation of the WHQ items 1 (redness), 3 (clear fluid), 7 (deep wound opening), 10 (pain), 11 (fever), 15 (antibiotics), 16 (debridement), 18 (drainage), and 19 (reoperation). Changes to three item response categories (1, not at all; 2, a little; 3, a lot) were adopted for symptom items 1 to 10, and two categories (0, no; 1, yes) for item 11 (fever).ConclusionThis study made recommendations for cross-cultural adaptation of the WHQ for use in global surgical research and practice, using co-produced mixed-methods data from three continents. Translations are now available for implementation into remote wound assessment pathways