Papers by Keyword: Heat Exchanger

Abstract: Application fields and requirements for roll-cladded cooling plates are continuously rising. Especially as part of the thermal management systems in battery electric vehicles (BEV), the share of roll-cladded cooling plates is growing. A deeper understanding of the deformation regime in the roll bite is needed to completely fulfill the high quality, performance and cost requirements of the automotive industry Whereas most cause-effect relationships in the roll-cladding process have been scientifically evaluated, the influence of separating agents on the deformation regime in partial roll-cladding has not yet been investigated. To examine this relationship, an experimental set up is created and trials are conducted on a laboratory size roll-cladding mill. Two different aluminum alloy blanks are joined together under temperature by roll-cladding without the application of strip tensions and with different separating agent patterns. The results show: Firstly, there is a correlation between the materials’ relative flow stress difference and their relative deformation. Secondly, the separating agents’ areal share over the blank width significantly impacts the deformation regime in the roll bite. Thirdly, in areas with separating agent there is a correlation between the surface elongation of the bottom blank and the elongation of the contact interface between the blanks, which governs the later cooling channel tolerances. To use the results in the industrial application, the impact of so far neglected parameters such as strip tensions have to be considered in future research.

Abstract: Space heating and cooling using geothermal heat exchangers is a promising environmentally friendly green energy solution. Modeling these energy storage systems is crucial for optimizing their design and operation. In this context, the present study consists of numerically investigating the effects of various physical properties, including thermal conductivity, density, and specific heat capacity of each material, as well as flow velocity, on the process of heat transfer in vertical geothermal heat exchangers using coaxial pipes to optimize their energy performance. Numerical simulations were carried out using Gambit-Fluent software. Different materials that make up the coaxial heat exchanger structure studied were tested to highlight their effects on the progress of heat flux and temperature. Thermal and fluid mechanics aspects were also studied. At the end of this study, a comparative analysis was carried out using the U-tube geothermal heat exchanger. The results indicate that the heat exchanger using a coaxial tube demonstrates superior thermal efficiency compared to the U-tube configuration. It has been found that using a low velocity with an appropriate selection of tube, grout, and soil materials results in enhanced dynamic exchanges, thereby enhancing the thermal efficiency of the geothermal exchanger.

Abstract: The current study looks at a hybrid passive cooling system that combines a solar chimney with an earth-to-air heat exchanger (EAHE) usually called Canadian Well. Numerous experimental and numerical examinations with various applied radiation heat fluxes were carried out to evaluate its ability to cool a room. Glass temperature, wall temperature, air flow mean temperature, hourly rate of air exchange (ACH), outlet airflow velocity, and rate of air mass flow were determined experimentally and numerically, and validated against previously published experimental and analytical works. It was found that the chimney's operation is dependent on the radiation intensity. The EAHE has reduced the room's temperature by improving exchanges with the solar chimney. The comparison of experimental and numerical data for different radiation intensities reveals that the best diameter of the tube of the underground heat exchanger for the proper operation of our system is d = 0.04m. The efficiency of our system increases as the radiation increases, causing an increase in the temperature of the absorber, which influences the air temperature in the chimney.

Abstract: This work presents a computational analysis of the heat-exchange characteristics in a double-cylinder (also known as a double-pipe) geometrical arrangement. The heat-exchange is from a hotter viscoelastic fluid flowing in the core (inner) cylinder to a cooler Newtonian fluid flowing in the shell (outer) annulus. For optimal heat-exchange characteristics, the core and shell fluid flow in opposite directions, the so-called counter-flow arrangement.The mathematical modelling of the given problem reduces to a system of nonlinear coupled Partial Differential Equations (PDEs). Specifically, the rheological behaviour of the core fluid is governed by the Giesekus viscoelastic constitutive model. The governing system of coupled nonlinear PDEs is intractable to analytic treatment and hence is solved numerically using Finite Volume Methods (FVM). The FVM numerical methodology is implemented via the open-source software package OpenFOAM. The numerical methods are stabilized, specifically to address numerical instabilities arising from the High Weissenberg Number Problem (HWNP), via a combination of the Discrete Elastic Viscous Stress Splitting (DEVSS) technique and the Log-Conformation Reformulation (LCR) methodology. The DEVSS and LCR stabilization techniques are integrated into the relevant viscoelastic fluid solvers. The novelties of the study center around the simulation and analysis of the optimal heat-exchange characteristics between the heated Giesekus fluid and the coolant Newtonian fluid within a double-pipe counter-flow arrangement. Existing studies in the literature have either focused exclusively on Newtonian fluids and/or on rectangular geometries. The existing OpenFOAM solvers have also largely focused on non-isothermal viscoelastic flows. The relevant OpenFOAM solvers are modified for the present purposes by incorporating the energy equation for viscoelastic fluid flow. The flow characteristics are presented qualitatively (graphically) via the fluid pressure, temperature, velocity, and the polymer-stress components as well as the related normal stress differences. The results illustrate the required decrease in the core fluid temperature in the longitudinal direction due to the cooling effects of the shell fluid, whose temperature predictably increases in the counter-flow direction.

Abstract: The heat exchanger is an example of heat transfer applications in industries that commonly found in cooling systems and powerplants. The heat exchangers utilise water, oil, and ethylene glycol (EG) as heat transfer fluids which possess a deficiency in heat transfer characteristics. Nanofluid are expected to improve the heat characteristics of the fluid used in heat exchangers. This research used MnFe₂O₄ nanoparticles with a volume fraction of 0.05% into the base fluid. The base fluid is a mixture of EG-water with a concentration of 20; 40; 60; and 80%. This study aims to understand the heat transfer characteristics of the MnFe₂O_4-EG/water nanofluid. The experiments were carried out on a double-pipe heat exchanger with variations flow rate 0.2; 0.4; and 0.6 l/min. This study is expected to show the best performance of MnFe₂O₄-EG/water nanofluid.

Abstract: The metallography was used for evaluation of localised form of corrosion of stainless steel tubes of heat exchangers. The heat exchangers were in service for relative short period from few months to 2 years. The service conditions of these heat exchangers were different (temperature, medium, etc.) and caused penetration of tube walls. The metallography cross sections were used to identified the corrosion mechanisms. For all evaluated cases the different mechanisms were found – pitting corrosion, microbiologically induced corrosion, trans-crystalline corrosion cracking, intercrystallite corrosion cracking. Together with diffraction and elementary analysis of corrosion products the metallography evaluation was used for identification of corrosion mechanisms.

Abstract: This study aimed to design a condenser for a special application of condensing the vapor of pyrolysis process of hydrocarbon-based material such as plastic and biomass into liquid form or pyrolytic oil. Numerous condensers have been available in the market. However, a condenser cannot be selected and utilized directly for pyrolysis vapor condensation purposes. Before doing selection, the condenser must be designed first to meet the heat transfer requirements. In this work, the condenser was designed based on thermal analysis and validated with numerous published experimental data and the pyrolytic characteristics from related industry. A theoretical model is formulated for describing condensation of the pyrolysis vapor in the condenser to determine heat transfer requirement and the rate of condensation obtained. The effect of operating parameters such as cooling water rate in liters per minute (LPM) and temperature on the condensation rate was examined through an iterative procedure which rely to the heat transfer rate and the allowed pressure drop in the condenser. In this study, it was obtained that the highest cooling load is obtained when the flow rate of cooling water is 1.95 LPM. It was also obtained that the condenser effectiveness decreased of about 29.3 % with the ranges of cooling flow rate from 1.3 to 2.6 LPM

Abstract: This study investigates transport process in circular tubes cross-flow Heat Exchanger (HEX) using water-CuO-nanofluids cooling media. The effects of nanoparticle volume fractions (Ø) and Reynolds number (Re) on the flow structure, coefficient of skin friction, isotherms and Nusselt number (Nu) are determined for steady laminar flow. The governing equations of continuity, momentum and energy are discretized over the flow domain and solved using SIMPLE method of the Finite Volume Method with ANSYS Fluent 16. The results show that the flow field for the conventional fluid is concentric around the inner tubes for Re up to 60 after which vortices evolve downstream behind the tubes, elongate and eclipse with the increase in Re. Vortex inception occurs at Re between 60 and 45 for 0 ≤ Ø ≤ 10%. The temperature fields are characterized by plume-like structure which envelopes the two inner cylinders between which heat transfer occurs. The average Nusselt number is correlated as Nu = 22.4 - 411,588س + 0.757Re + 1803.31/ln(Re) in which the interaction between Re and Nu has significant (p ≤ 0.05) effect. The addition of nanoparticles in the range 2 ≤ Ø ≤ 10% results in the increase in Nu from 0.55 to 5.84%. It follows that the thermal performance of the cross flow heat exchanger could be enhanced with CuO-based nanofluids.

Abstract: The research objective is to assemble a convection test system which acts as a heat exchanger (HE) and test its applicability using ethylene glycol. A Double Pipe (DP)-type HE consists of an inner pipe surrounded by an outer pipe (annulus) whereas a Coil-type HE composed of a coil surrounded by an outer pipe. Water flows through the outer pipe in both types of HE, while ethylene glycol flows through the inner piper or coil. HE in combination with other components (such as) forms a convection test system. The applicability of the system was tested to determine the heat transfer coefficient of ethylene glycol in a DP-type and Coil-type HEs. After that, the heat transfer rate was calculated and compared. The results show that the heat transfer coefficient in the DP-type HE is the lowest at 12.2 W/m2 oC and the highest at 26.8 W/m2 oC; and the corresponding heat transfer rate is the lowest at 8.3 W and the highest is 56.3 W. In comparison, for Coil-type HE, the lowest heat transfer coefficient is 38.9 W/m2 oC and the highest is 66.2 W/m2 oC which correspond to the heat transfer rate 19.9 W at the lowest and 225 W at the highest.

Abstract: For the corrosion resistance analysis of the heat exchanger plates (made of AISI 316L steel) the samples with visible damage was delivered. The major part of the surface damages was located at the place of "close proximity" (or surface contact) of individual plates. Some of delivered samples showed an unequal layers of sediments, which indicating a different flow velocities of operating fluid through the plates. At locations of the upper part of the plates with no sedimentation (high velocity flow), the most surface damage was detected in "near contact" areas as well as outside. On the other hand, the area of the lower part of the plates, where the sediment deposition was massive (lowest velocity flow), was observed the smallest surface damage. The results of the chemical composition analyses showed a lower amount of molybdenum and a higher amount of phosphorus in case of all samples. The contents of the key elements necessary for the corrosion resistance (chromium and nickel) were only just above the lower limit of the prescribed chemical composition interval. For detailed study of surface damage, selected defects were observed and documented using scanning electron microscopy. Localized damage showed intercrystalline failure of material with typical surface morphology degraded as a result of cavitation damage under hydrodynamic stress.