Evaluation Of The Thermal And Hydraulic Performance Of A Double Pipe Heat Exchanger By Use Of Various Porous Structures (original) (raw)
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Heat Transfer Improvement in Heat Exchanger using Porous Medium: a Review
1. ABSTRACT The present study is to investigate the heat transfer enhancement in a cylindrical heat exchanger using porous media. The heat exchanger is modeled by a cylindrical cavity (Shell) with inlet and outlet thermally insulated ports and five tubes which contain hot water and cold water flows in the shell. The effect of porosity on heat transfer enhancement is studied at the different mass flow rate. The study about the effect of porosity on heat transfer enhancement is done by both experimentally and CFD based and the results are compared with the simple heat exchanger. By decreasing the porosity, the heat transfer rate increases and the mean outlet temperature of the fluid increases for different mass flow rate.
Analysis of fluid flow and heat transfer in a double pipe heat exchanger with porous structures
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A numerical study of flow and heat transfer characteristics is made in a double pipe heat exchanger with porous structures inserted in the annular gap in two configurations: on the inner cylinder (A) and on both the cylinders in a staggered fashion (B). The flow field in the porous regions is modelled by the Darcy-Brinkman-Forchheimer model and the finite volume method is used to solve the governing equations. The effects of several parameters such as Darcy number, porous structures thickness and spacing and thermal conductivity ratio are considered in order to look for the most appropriate properties of the porous structures that allow optimal heat transfer enhancement. It is found that the highest heat transfer rates are obtained when the porous structures are attached in configuration B especially at small spacing and high thicknesses.
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In this paper, the rate of heat transfer by forced convection in a counterflow heat exchanger, at turbulent flow conditions were investigated experimentally, using porous media and TiO2 Nanofluid to observe the behaviour of heat transfer with flow rate and volume concentration of nanoparticles t enhance heat transfer through it. 3mm Steel balls (ε=39.12%) as a porous media completely filled to the inner pipe (core pipe). The cold and hot water are used as working fluids through the inner and outer pipes. Then using, the TiO2 nanofluid instead of cold water flowing through the porous pipe to enhance heat characteristics. The effects of operating parameters include flow rate (4 LPM, 6 LPM, and 8 LPM), Reynolds number between (3000 – 7000), and nanoparticle volume fraction (0.001, 0.002 and 0.003) on Convective heat transfer coefficient and Nusselt number. Effective thermal conductivity is increased when the nanoparticle volume fraction is increased. The heat transfer coefficient increases with decreasing nanofluid temperature, but the heating fluid's temperature has no significant effect on the nanofluid's heat transfer coefficient. The results show that porous media and TiO2 based nanofluid's improve heat transfer at flow rate of 4 LPM by 35.4% and improve NTU and effectiveness at flow rate of 4LPM by 12.4%, and 24%, respectively, when compared to pure water without porous media. This improvement in thermophysical properties yielded high heat transfer of heat exchangers used in process industries.
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Using Porous Media to Enhancement of Heat Transfer in Heat Exchangers
— According to increasing human needs for energy and to avoid energy waste, researchers are struggling to increase the efficiency of energy production and energy conversion. One of these methods is increasing heat transfer and reducing heat dissipation in heat exchangers. Using porous materials in the fluid flow is one of the passive methods to increase heat transfer in heat exchangers. The existence of porous media in the flow path, improve the matrix of thermal conductivity and effective flow thermal capacity and also matrix of porous-solid increase radiation heat transfer, especially in two phase flow (gas-water) systems. In this paper, recent studies on the effect of using porous media on enhancement the amount of heat transfer in heat exchangers has been investigated via using porous media with difference porosity percentage, material and geometric structure in the flow path in numerical simulations and laboratory studies.
EXPERIMENTAL STUDY OF HEAT TRANSFER ENHANCEMENT IN HEAT EXCHANGER USING POROUS MEDIA
In present work experimental investigation of heat transfer enhancement in double pipe counter flow heat exchanger with insert metallic pad inner tube. Experimental work included the design of a tube in tube heat exchanger with the dimensions of (length 1.11m, 0.063m outer tube diameter and 0.031m inner tube diameter) Plain and saturated with pad heat exchanger. The examination were tested to evaluate their influence on effectiveness of heat exchanger, heat transfer coefficient, number transfer unit and pressure drop at steady-state condition. Water was used as a working fluid in the double pipe heat exchanger where hot water flow in inner tube and cold water flow in outer tube. The study was conducted at the hot water mass flow rates between (0.066-0.198 kg/s) and (0.1997 kg/s) cold water mass flow rate. The inlet temperatures of hot and cold water were (43 ᵒC) and (18 ᵒC) respectively. The results are obtained for range of Reynolds number to hot water (4862.9< Re<14633.8) and constant for cold water (Re=2912.2). The experimental results show that the major effective factors on the axial temperature distribution of heat exchanger, the effectiveness, heat transfer coefficient and pressure drop are the mass flow rate and adding metallic pad, where, The inner heat transfer coefficient of heat exchanger increased with increase in Reynold number, heat transfer coefficient when add metallic pad (WP) the inner tube of heat exchanger higher of plain pipe, the enhancement factor of heat transfer coefficient in metallic pad comparison with plain case are (2.074). The effectiveness decreases with increase hot water Reynold number, and increase by 26.5% when use of metallic pad compared with plain tube (WOP). The performance ratios obtained are in the ranges of 0.1
—The present study is to investigate the heat transfer enhancement in a cylindrical heat exchanger using porous media. The heat exchanger is modelled by a cylindrical cavity (Shell) with inlet and outlet thermally insulated ports and five tubes which contain hot water and cold water flows in shell. The effect of porosity on heat transfer enhancement is studied at different mass flow rate 0.15, 0.2, 0.25 and 0.30 Kg/sec. The study about effect of porosity on heat transfer enhancement is done by both experimentally and CFD based and the results are compared with simple heat exchanger. In present study, two different types of porous materials are used and Porosity is taken as 80%. The effect of varying mass flow rate on outlet temperature, heat transfer coefficient, Reynolds number and Nusselt number has been investigated.
Experimental Investigation of Heat Transfer through Porous Material Heat Exchanger
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Latest developments in the manufacturing technology have led to development of advance lightweight materials for thermal applications. Heat transfer through porous materials has gained significance in industrial as well as academic research. In this paper thermal performance including heat transfer and pressure drop through porous material, i.e. metal foam heat exchanger, has been presented. The experimental data has been used to calculate and present graphically various performance parameters such as effectiveness, friction factor, Reynolds number and Nusselt number.The effectiveness of the heat exchangers was compared at u = 0.5–7 m/s fluid velocity, it was found that the best performance is exhibited by heat exchanger at effectiveness (ε = 30%, u = 0.2 m/s). Maximum heat transfer occurs at Reynolds number of 900. For further investigation advance methods such as artificial neural networks, fuzzy logic and genetic algorithm can be used.
Heat Transfer-Asian Research, 2013
An experimental study on single-phase laminar forced convection in a single porous tube heat exchanger is presented. Parametric studies are conducted for different inlet pressures, different mass flow rates, and different porosities to evaluate the effects of particle diameter and Reynolds number on the heat transfer and friction factor. The Nusselt number and friction factor are developed for efficient design of a porous heat exchanger based on the present configuration. Heat is transferred to the walls of the heat exchanger by natural convection mode. Gravel sand with different porosities is used as a porous medium during the tests. The flow of carbon dioxide as a working fluid in the porous medium is modeled using the Brinkman-Forchheimer-extended Darcy model. A dimensionless performance parameter is developed in order to be used in evaluating the porous tube heat exchanger based on both the heat transfer enhancement and the associated pressure drop. The study covers a wide range of inlet pressures (P i), mass flow rates (m .), porosity of gravel sand (ε), and particle diameters (d m) which ranged 34.5 ≤ P i ≤ 43 bars, 8 * 10 −5 ≤ m. ≤ 16 * 10 −5 kg/s, 34.9% ≤ ε ≤ 44.5%, 1.25 ≤ d m ≤ 5.15 mm, respectively. This study revealed that a smaller particle diameter can be used to achieve higher heat transfer enhancement, but a larger particle diameter leads to a more efficient performance based on heat transfer enhancement. The average heat transfer coefficient of carbon dioxide decreases when the porosity increases.
Renewable Energy, 2020
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