Papers by Keyword: Heat Transfer

Abstract: This paper presents a numerical investigation to evaluate thermal-hydraulic performance of double forward facing step. The combined analysis of double forward-facing step geometries and wavy-wall amplitude, which has never been done previously, is what makes this study groundbreaking. With the help of the double-step construction and the undulating upper wall, this special arrangement seeks to improve the thermal-hydraulic performance.The effect of varying wavy amplitude and the relative double step height was evaluated under different turbulent flow conditions. The turbulent flow and energy was modelled by contiuity full Navier-Stockesand energy equations. The effect of turbulent was modelled by k- Ɛ model. The finite volume method based on a simple algorithm was adoped to the discretise the flow and energy models. ANSYS Fluent was used to obtain the target results. The obtained results show that the increasing the amplitude value and the relative step height has a noticeable effect on intensification of average Nusselt number and overall performance with a moderate increase in friction losses. The findings reported that the steps height ratio (H_r= 2.6) provides the best overall performance for all the tested Reynolds numbers.The maximum performance was 1.63 (163%) at Re=10000 for Am=0.03 m.

Abstract: This study presents the modelling of heat loss and mass transfer through the walls, using Ubakus program, of a block of flats built in 1978 and thermally rehabilitated after 1990. The objective of the study is to present the thermal and mass transfer parameters before and after thermal rehabilitation. Thus, the benefits obtained after the rehabilitation consist in improving the comfort and health conditions for the residents, as well as reducing the expenses for heating/cooling the house and for renovating the degradation caused by humidity in the walls.

Abstract: Li-ion batteries generate significant heat during operation, which leads to an increase in temperature and, consequently, a reduction in the battery's efficiency and lifespan. In this study, different cooling methods are simulated for the thermal management of the battery. The cooling using air and liquids is investigated with laminar flow at varying velocities. Results indicated that the use of water/glycol is more effective than air and mineral oil.

Abstract: The precision in temperature estimation plays a pivotal role in the design and operational efficiency of CubeSats. This study leverages the capabilities of COMSOL MULTIPHYSICS to model the thermal behavior of a 1U CubeSat, with a focus on evaluating the impact of orientation and beta angle on heat transfer dynamics and the resultant temperature distribution throughout the satellite. By conducting an extensive range of simulations that explore beta angles from 0° to 90° across four distinct satellite orientations, this research uncovers critical insights into the heat transfer mechanisms within the CubeSat framework. These findings illuminate the substantial influence of orientation and beta angle on the satellite's thermal state, highlighting the necessity of incorporating these factors into any comprehensive thermal analysis of spacecraft. The outcomes of this investigation not only contribute to a deeper understanding of CubeSat thermal management but also underscore the importance of meticulous design and analysis practices to optimize satellite performance in the challenging space environment.

Abstract: This work presents a numerical study of natural convection heat transfer in a cavity filled with an ionanofluid. The governing equations are solved using the finite volume method and the SIMPLEC algorithm. This study aims to analyze the effects of key parameters influencing the flow structure and heat transfer, including the Rayleigh number (Ra), the volume fraction (𝜑), the inclination angle, and the type of base fluid.The results indicate that increasing the volume fraction (𝜑) enhances heat transfer and underscores the superiority of ionic fluids over water as a base fluid. Additionally, heat transfer reaches its maximum at a specific inclination angle.

Abstract: This study presents an analytical and numerical approach to thermosolutal mixed convection in a vertical rectangular cavity containing a Newtonian fluid of Prandtl number, Pr = 7. The vertical walls are mobile and subject to constant heat and mass fluxes, while the horizontal walls are considered impermeable and adiabatic. The mathematical model is based on the Navier-Stokes equations, as well as the conservation of energy and concentration equations. An analytical solution, based on the parallel flow approximation, has been developed for elongated cavities (A >> 1). At the same time, the governing equations were solved numerically using the finite-difference method. The results show that the analytical solution is in good agreement with the numerical one for all the considered parameters. Rayleigh number and Peclet number growth play roles in enhancing mixed convection, thus influencing the overall flow and heat transfer characteristics.

Abstract: Throughout this study, the Lewis number influence on double-diffusive natural convection inside a rectangular cavity horizontally disposed, filled with Copper nanoparticles dispersed in water, heated and salted by constant thermal and solutal fluxes on the side walls while the horizontal ones are assumed thermally adiabatic and solutally impermeable, is studied analytically (parallel flow approximation) and numerically (finite difference method) for a large range of the aspect ratio, 1 ≤ A ≤ 16, the Lewis number, 10-3 ≤ Le ≤ 103, and the nanoparticles volume fractions, φ = 0 and 0.05. The results revealed that the numerical and analytical outcomes showed a good agreement. Both the aspect ratio and the Lewis number have a range responsible for variations in heat and mass transfer rates, A ≤ 12 and 10-2 ≤ Le ≤ 10 for Nusselt number and Le ≥ 10-2 for Sherwood number. The results obtained by examining the interest of using nanofluids in the considered configuration were against all expectations, that they led to a degradation of the rates of heat and mass transfers with the increase in the nanoparticle volume fraction.

Abstract: Lattice boltzmann method (LBM) has emerged as a powerful numerical technique for simulating fluid flows due to its inherent simplicity and efficiency. In this paper we studied a convective heat transfer occurring naturally within a cubic enclosure differentially heated filled with air (Pr=0.71) to compare the obtained results with those obtained from the literature. For this a fortran code program utilized for simulating natural convective phenomena in two and three dimensions (2d and 3d LBM) considerate a single relaxation time LBM (SRT-LBM). The results are presented in terms of isotherms, velocity and average nusselt number. The verification of the lattice boltzmann method code shows a good agreement with the literature.

Abstract: Heat exchangers are widely recognized as eco-friendly devices that transfer heat between two or more fluids without mixing. Double Pipe Heat Exchangers (DPHE) are used in many industrial applications such as power generation, chemical processing, HVAC, and renewable energy systems. Traditional DPHEs are simple and reliable, however, they often face limitations in heat transfer. Improving the thermal performance of DPHE can significantly enhance the operational efficiency of thermal energy systems. This study presents a novel fin arrangement to the traditional DPHE using different diamond-shaped fins to improve its thermal performance. The thermal and hydraulic properties of DPHE with different diamond-shaped fin configurations are investigated using CFD analysis. The optimization process is carried out using the Response Surface Method (RSM) for optimal diamond-shaped fin design. The results indicate that novel diamond-shaped fins improve thermal performance, particularly at high mass flow rates. The thermal enhancement factor (TEF), overall heat transfer coefficient, and pressure drop are used to evaluate the thermal performance of DPHE. The diamond-shaped fins exhibit a 55% increase in overall heat transfer coefficient compared to conventional DPHE. The TEF for diamond-shaped fin configurations is higher than 1 with a maximum value of 1.63 for DPHE-HF45 depicting a 63% increase in thermal enhancement. The optimization results show that the optimal fin design achieves a desirability of 81.3%, with a pressure drop of 870.726 Pa and an overall heat transfer coefficient of 2199.85 W/m²K at a mass flow rate of 2.711 lit/min.

Abstract: The objective of this work is to study the heat transfer on rectangular perforatedor non-perforatedfins of different geometries and different materials and to see the influence of these holes on the cooling of the structures. Different simulations using the Nastran/Patran software were carried out. In order to validate the numerical results, an experimental part was carried out. To collect the data of the sensed temperatures, circuits were used based on the Arduino programmable board or the Pic 16F8777A microcontroller programmed by the MicroC and Proteus software. In order to visualize, analyse and control the data, Labview software was used and a personalized interface was created. The results obtained show that by increasing the number and the diameter of holes, the temperature decreases. It is shown that the surface area of ​​the holes is more important than the shape of the holes. There are certain hole distributions that give better results compared to others.