Papers by Keyword: Heat Transfer

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.

Abstract: A special localization technique is presented for solving steady heat transfer problems, in which the thermal conductivity may depend on space variables. The original problem is split into several subproblems defined on much smaller subdomains. The subproblems are solved using the Method of Fundamental Solutions, which is a truly meshless method. This leads to a Seidel-like iterative technique, which mimics the classical Schwarz overlapping method. The problems associated with large, dense and ill-conditioned matrices are avoided. The method is embedded into a multi-level context, which significantly reduces the computational complexity.

Abstract: Passive Flow Control in Pipelines is gaining increased importance in the field of fluid transport, particularly in oil and gas applications. This approach relies on the installation of passive devices designed to alter fluid flow paths by generating suppression zones. Among these devices, fins are particularly notable. Hence, the objective of this paper is to provide a numerical investigation into the behavior of laminar flow within a bifurcated backward-facing step (BFS), controlled through the installation of a flexible fin at the lower wall of the enlarged duct part, with varying mechanical stiffness and positioning. The study considers a flow through an expanded conduit, where the fluid enters with a predefined velocity profile and subsequently splits into two sub-conduits. The investigation focuses on examining the influence of fin length (0.5 ≤ L_c/H ≤ 1), position (4 ≤ x₀/H ≤ 7), and elasticity on the elasto-hydrodynamic structure of the flow, including vortex formation, flow separation, the maximum displacement of the flexible fin, and the efficiency of the sub-conduits at the outlet. This analysis is governed by the momentum equations, coupled with solid mechanics equations, using the Arbitrary Lagrangian-Eulerian (ALE) framework. The governing equations are solved using the finite element method, implemented through the simulation and the sliding mesh technique in COMSOL Multiphysics 5.7. The numerical results reveal that installing a flexible or rigid fin within the BFS system significantly impacts the non-isothermal flow behavior within the bifurcation ducts. This configuration effectively allows for flowrate regulation at the BFS outlet, also making it possible to equalize flow rates under specific conditions, particularly when using longer fin that extend halfway across the channel. Moreover, the fin placement on the bottom is important for achieving effective flow rate control and heat transfer, aligning with desired requirements for each branch outlet.

Abstract: Natural gas is selected as transition energy to achieve net zero emissions. Gas pipeline construction is developed in accordance with Sustainable Development Goals on Industry, Innovation & Infrastructure, Clean & Affordable Energy, and Climate Action. The potential risk of the heat transfer process from the pipeline to the ground surface temperature can create a potential hazard that can cause pain/injury to human skin if it exceeds the pain threshold temperature. This study aims to investigate the best method for risk mitigation of heat transfer from gas pipelines to the ground surface, through alternative solutions such as burial deepening options, insulation options, or air cooler at well site options. These options are studied as part of the risk mitigation strategy for the buried high-temperature gas pipeline construction. These risk mitigation options consider technical and economic feasibility studies at the conceptual stage presented in this study to identify the best option to mitigate the potential injury risk to humans. The result with a buried insulated pipeline is the best option for controlling heat transfer compared to the air cooler option. The constructability of burial deepening up to 8 m is not feasible, especially the 6m depth of the groundwater table observed.

Abstract: This article presents the findings of a research on improving the properties of hemp masonry to meet the standard strength of non-load baring concrete blocks and assess its properties as energy conserving construction material according to specifications declared under the Ministerial Announcement of the Ministry of Energy. Production of hemp masonry used finely chopped hemp stalk with bark mixed with Type 1 Portland cement, sand and water to form 7.5 x 7.5 x 10 centimeters blocks. The ratio by weight between hemp and binder was 1:10 and the property was improved using Al₂(SO₄)₃, plasticizers, natural rubber latex and polymer. Compression strength, dry density, water absorption, thermal conductivity coefficient, specific heat value and OTTV were tested. The research found that hemp masonry improved using Al₂(SO₄)₃ at 10% by weight of hemp with polymer was the sample with properties within standard limits of non-load baring concrete blocks. The compression strength achieved was 2.79 MPa, dry density 990 kg/m³, water absorption 351 kg/m³, thermal conductivity coefficient 0.25 w/m°C, specific heat 1.12 kJ/kg°C and the highest OTTV of 45 w/m² was calculated for the southeast wall. This was lower than the minimum standard for masonry of energy conserved office building. Therefore, the masonry produced using hemp stalk with bark has the strength comparable to non-load baring concrete block and has the quality to protect heat from outside which is good for energy conservation construction practice.

Abstract: A cooling tower is a cooling device often used in industries as a heat exchanger, where water is cooled by coming into direct contact with air. This process causes evaporation, which leads to a reduction in the water's temperature. We conducted an experimental study of the effect of the number of holes (80, 120, 185 and 250) on the cooling tower flat plate with variations of inlet temperature (65°C, 75°C and 85°C). This study aims to determine the heat transfer characteristics and how the number of holes and inlet temperature variations affect the performance of multi-story cooling towers. The cooling tower has an overall height of approximately 2.4 m, with each flat plate measuring 0.7 m x 0.5 m and a 15° slope. The results showed that the highest heat transfer rate occurred at 85°C inlet temperature with 250 holes. The largest heat transfer coefficient value occurred at 75°C inlet temperature with 250 holes. Thus, the number of holes significantly influences the heat transfer rate, convection heat transfer coefficient, and temperature difference in the optimization of the cooling tower performance.

Abstract: This study proposes a numerical investigation of turbulent flow and heat transfer properties within an air channel featuring a 7-shaped baffle affixed to the lower wall. The main objective of this computational investigation is to assess how the Reynolds number influences the enhancement of heat transfer across a range of Reynolds values from 18000 to 33000. To solve the governing equations, the QUICK numerical scheme and the SIMPLE discretization algorithm are employed. The numerical results are presented through variations in mean velocity and temperature, as well as profiles of local Nusselt number, friction coefficient, Nusselt number and friction factor. These representations facilitate a comprehensive exploration of the aerodynamic and thermal flow properties.

Abstract: Atherosclerosis occurs due to plaque thickening in arteries, reducing blood flow and oxygen supply to tissues. This study models blood flow in a bifurcated stenosed artery under a uniform magnetic field, analyzing magnetohydrodynamics (MHD) hybrid blood nanofluid flow with heat transfer. Using COMSOL Multiphysics, the laminar and Newtonian flow of a hybrid blood nanofluid with silver (Ag) and gold (Au) nanoparticles is simulated. Results, validated by existing literature, highlight key parameters such as velocity, heat flux, and wall shear stress (WSS). The study shows that Ag and Au nanoparticles improve blood flow, reducing recirculation in stenosed arteries, offering the potential for nanomedicine treatments.

Abstract: The energy issue is necessary today due to the decrease in fossil energy and its impacts on the environment. It is important to use energy effectively. In the air conditioning sector, the energy consumption of air conditioners is the top energy user in buildings. The air conditioner user needs to find the best way to operate the air conditioner. In the present research, the effect of pressure behavior at start-up conditions on the energy consumption and heat transfer process is analyzed. The result shows that the pressure behavior affects the evaporator temperature, specific heat, and thermal conductivity in liquid and vapor conditions. In the first 20-second AC operation, the energy consumption of the AC compressor increases significantly before the compressor work slowly decreases at 40-second operation and remains constant at steady conditions. The negligible heat transfer at the first 20-second AC operation increases steeply for 40 seconds. The heat transfer is steady at 60 seconds of operation and above.