Natural Convective Flow and Heat Transfer in a Collector Storage with an Immersed Heat Exchanger: Numerical Study

2005 ◽  
Vol 127 (3) ◽  
pp. 324-332 ◽  
Author(s):  
Yan Su ◽  
Jane H. Davidson
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Heat Exchanger ◽  
Numerical Study ◽  
Storage System ◽  
Fluid Motion ◽  
Heat Transfer Process ◽  
Strong Mixing ◽  
Scale Analysis ◽  
Three Dimensional Model

A three-dimensional model and dimensionless scale analysis of the transient fluid dynamics and heat transfer in an inclined adiabatic water-filled enclosure with an immersed cylindrical cold sink is presented. The geometry represents an integral collector storage system with an immersed heat exchanger. The modeled enclosure has an aspect ratio of 6:1 and is inclined at 30deg to the horizontal. The heat exchanger is represented by a constant surface temperature horizontal cylinder positioned near the top of the enclosure. A scale analysis of the transient heat transfer process identifies four temporal periods: conduction, quasi-steady, fluctuating, and decay. It also provides general formulations for the transient Nusselt number, and volume-averaged water temperature in the enclosure. Insight to the transient fluid and thermal processes is provided by presentation of instantaneous flow streamlines and isotherm contours during each transient period. The flow field consists of two distinct zones. The zone above the cold sink is nearly stagnant. The larger zone below the sink is one of strong mixing and recirculation initiated by the cold plume formed in the boundary layer of the cylindrical sink. Correlations for the transient Nusselt number and the dimensionless volume-averaged tank temperature predicted from the model compare favorably to prior measured data. Fluid motion in the enclosure enhances heat transfer compared to that of a cylinder in an unbounded fluid.

Natural Convective Flow and Heat Transfer in a Collector Storage With an Immersed Heat Exchanger: Numerical Study

Solar Energy ◽  
2005 ◽  
Author(s):  
Yan Su ◽  
Jane H. Davidson
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Heat Exchanger ◽  
Numerical Study ◽  
Storage System ◽  
Three Dimensional ◽  
Heat Transfer Process ◽  
Strong Mixing ◽  
Scale Analysis ◽  
Three Dimensional Model

A three-dimensional model and dimensionless scale analysis of the transient fluid dynamics and heat transfer in an inclined adiabatic water-filled enclosure with an immersed cylindrical cold sink is presented. The geometry represents an integral collector storage system with an immersed heat exchanger. The modeled enclosure has an aspect ratio of 6:1 and is inclined at 30 degrees to the horizontal. The heat exchanger is represented by a constant surface temperature horizontal cylinder positioned near the top of the enclosure. A scale analysis of the transient heat transfer process identifies four temporal periods: conduction, quasi-steady, fluctuating and decay. It also provides general formulations for the transient Nusselt number, and volume averaged water temperature in the enclosure. Insight to the transient fluid and thermal processes is provided by presentation of instantaneous flow streamlines and isotherm contours during each transient period. The flow field consists of two distinct zones. The zone above the cold sink is nearly stagnant. The larger zone below the sink is one of strong mixing and recirculation initiated by the cold plume formed in the boundary layer of the cylindrical sink. Correlations predicted with the model for the transient Nusselt number and the dimensionless volume averaged tank temperature expressed in terms of the initial Rayleigh number compare favorably to prior measured data.

scholarly journals CFD SIMULATION OF THE HEAT TRANSFER PROCESS IN A CHEVRON PLATE HEAT EXCHANGER USING THE SST TURBULENCE MODEL

2015 ◽  
Vol 55 (4) ◽  
pp. 267 ◽  
Author(s):  
Jan Skočilas ◽  
Ievgen Palaziuk
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Transfer Process ◽  
Cfd Simulation ◽  
Numerical Study ◽  
Analytical Calculation ◽  
Heat Transfer Process ◽  
Plate Heat Exchanger ◽  
Hot Water ◽  
Plate Heat

<p>This paper deals with a computational fluid dynamics (CFD) simulation of the heat transfer process during turbulent hot water flow between two chevron plates in a plate heat exchanger. A three-dimensional model with the simplified geometry of two cross-corrugated channels provided by chevron plates, taking into account the inlet and outlet ports, has been designed for the numerical study. The numerical model was based on the shear-stress transport (SST) <em>k-!</em> model. The basic characteristics of the heat exchanger, as values of heat transfer coefficient and pressure drop, have been investigated. A comparative analysis of analytical calculation results, based on experimental data obtained from literature, and of the results obtained by numerical simulation, has been carried out. The coefficients and the exponents in the design equations for the considered plates have been arranged by using simulation results. The influence on the main flow parameters of the corrugation inclination angle relative to the flow direction has been taken into account. An analysis of the temperature distribution across the plates has been carried out, and it has shown the presence of zones with higher heat losses and low fluid flow intensity.</p>

scholarly journals Experimental and numerical studies of a spiral plate heat exchanger

2014 ◽  
Vol 18 (4) ◽  
pp. 1355-1360 ◽  
Author(s):  
Rajavel Rangasamy
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Heat Exchanger ◽  
Numerical Study ◽  
Numerical Models ◽  
Plate Heat Exchanger ◽  
Test Fluid ◽  
Plate Heat ◽  
Plate Spacing ◽  
Spiral Plate

An experimental and numerical study of heat transfer and flow characteristics of spiral plate heat exchanger was carried out. The effects of geometrical aspects of the spiral plate heat exchanger and fluid properties on the heat transfer characteristics were also studied. Three spiral plate heat exchangers with different plate spacing (4mm, 5mm and 6 mm) were designed, fabricated and tested. Physical models have been experimented for different process fluids and flow conditions. Water is taken as test fluid. The effect of mass flow rate and Reynolds number on heat transfer coefficient has been studied. Correlation has been developed to predict Nusselt numbers. Numerical models have been simulated using CFD software package FLUENT 6.3.26. The numerical Nusselt number have been calculated and compared with that of experimental Nusselt number.

Numerical Study of Shellside Performance of Heat Transfer and Flow Resistance for Heat Exchanger with Trefoil-Hole Baffles

2012 ◽  
Vol 557-559 ◽  
pp. 2141-2146
Author(s):  
Yong Hua You ◽  
Ai Wu Fan ◽  
Chen Chen ◽  
Shun Li Fang ◽  
Shi Ping Jin ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Heat Exchanger ◽  
Heat Transfer Rate ◽  
Pressure Loss ◽  
Transfer Rate ◽  
Numerical Study ◽  
Shell Side ◽  
Tube Heat Exchanger

Trefoil-hole baffles have good thermo-hydraulic performances as the support of heat pipes, however the published research paper is relatively limited. The present paper investigates the shellside thermo-hydraulic characteristics of shell-and-tube heat exchanger with trefoil-hole baffles (THB-STHX) under turbulent flow region, and the variations of shellside Nusselt number, pressure loss and overall thermo-hydraulic performance (PEC) with Reynolds number are obtained for baffles of varied pitch with the numerical method. CFD results demonstrate that the trefoil-hole baffle could enhance the heat transfer rate of shell side effectively, and the maximal average Nusselt number is augmented by ～2.3 times that of no baffle, while average pressure loss increases by ～9.6 times. The PEC value of shell side lies in the range of 16.3 and 73.8 kPa-1, and drops with the increment of Reynolds number and the decrement of baffle pitch, which indicates that the heat exchanger with trefoil-hole baffles of larger pitch could generate better overall performance at low Reynolds number. Moreover, the contours of velocity, turbulent intensity and temperature are presented for discussions. It is found that shellside high-speed jet, intensive recirculation flow and high turbulence level could enhance the heat transfer rate effectively. Besides good performance, THB-STHXs are easily manufactured, thus promise widely applied in various industries.

scholarly journals Graphing Behaviour of Heat Transfer In Terms of Nusselt and Reynolds

2021 ◽  
Vol 6 (2) ◽  
pp. 41-52
Author(s):  
Mohd Rahimie Md Noor ◽  
Nur Syafiqah Hidayah Mohd Fauzi ◽  
Siti Nur Fadhilah Masrom ◽  
Mohd Azry Abdul Malek ◽  
Muhammad Firdaus Mustapha ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Volume Flow Rate ◽  
Convection Heat Transfer ◽  
Heat Transfer Process ◽  
Two Fluids ◽  
The Relationship

Heat exchangers are tools used to transfer thermal energy between two fluids (liquid or gas) by convection and conduction at different level of temperatures. Heat exchangers are the common equipment and employed in many different applications because of ability to withstand high temperatures and compactness. There are no intermixing or leakage occurred between two fluids during the heat transfer process as fluids are separated by walls of heat exchanger. The main objective of this project is to determine the heat exchanger effectiveness in heat transfer performance. This will be done by investigating the performance of five different angles of heat exchanger which are 150,300, 450, 600 and 750. The effectiveness of heat exchanger depends on the convection heat transfer coefficient of the fluid. Besides that, this project also aims to develop some parameters such as Nusselt number, Reynolds number and Prandtl number for evaluating the heat transfer. It is found that the Nusselt Number at angle of 150 is lower compared to angle of 750. Meanwhile, Reynolds number for angle 150 is higher than angle 750 which means that the type of flow produced by angle 150 is turbulent flow while for 750 angle is laminar flow. Hence, the overall result of this project proved that 150 is the best angle for heat exchanger in chimney because of higher velocity, higher volume flow rate, higher density of gas and higher LMTD. The relationship between Nusselt number and Reynolds number between different angles can be observed by plotting the graph using Maple Software.

Numerical Study of Flow and Heat Transfer Enhancement by Using Delta Winglets in a Triangular Wavy Fin-and-Tube Heat Exchanger

2009 ◽  
Vol 131 (9) ◽  
Author(s):  
Liting Tian ◽  
Yaling He ◽  
Pan Chu ◽  
Wenquan Tao
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Fluid Flow ◽  
Heat Exchanger ◽  
Friction Factor ◽  
Numerical Study ◽  
Attack Angle ◽  
Geometrical Parameters ◽  
Tube Heat Exchanger ◽  
Delta Winglet

In this paper, three-dimensional numerical simulations with renormalization-group (RNG) k-ε model are performed for the air-side heat transfer and fluid flow characteristics of wavy fin-and-tube heat exchanger with delta winglet vortex generators. The Reynolds number based on the tube outside diameter varies from 500 to 5000. The effects of different geometrical parameters with varying attack angle of delta winglet (β=30 deg, β=45 deg, and β=60 deg), tube row number (2–4), and wavy angle of the fin (θ=0–20 deg) are examined. The numerical results show that each delta winglet generates a downstream main vortex and a corner vortex. The longitudinal vortices are disrupted by the downstream wavy trough and only propagate a short distance along the main flow direction but the vortices greatly enhance the heat transfer in the wake region behind the tube. Nusselt number and friction factor both increase with the increase in the attack angle β, and the case of β=30 deg has the maximum value of j/f. The effects of the tube row number on Nusselt number and friction factor are very small, and the heat transfer and fluid flow become fully developed very quickly. The case of θ=5 deg has the minimum value of Nusselt number, while friction factor always increases with the increase in wavy angle. The application of delta winglet enhances the heat transfer performance of the wavy fin-and-tube heat exchanger with modest pressure drop penalty.

Numerical Study on Heat Transfer Enhancement and Friction Factor of LS-2 Parabolic Solar Collector

2013 ◽  
Vol 6 (1) ◽  
Author(s):  
Omid Karimi Sadaghiyani ◽  
Seyed Mehdi Pesteei ◽  
Iraj Mirzaee
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Friction Factor ◽  
Solar Collector ◽  
Numerical Study ◽  
Simulation Method ◽  
Finite Volume Methods ◽  
Statistical Technique ◽  
Heat Transfer Process ◽  
Outlet Temperature

In this work, the distribution of solar heat flux around receiver was calculated by Mont-Carlo statistical technique that has been written using matlab. The numerical investigations of convective heat transfer process, friction factor, and efficiency of LS-2 parabolic collector have been performed. Based on finite volume methods, the influence of Rayleigh number (Ra), diameter of plugs, and thermal conductivity of the tube were studied on Nusselt number, outlet temperature, and the efficiency of collector. Because of using several central plugs with different diameters, the amounts of flow velocity have been changed, as the mass flow rate of each case study was considered constant. The diameters of plug were as: 10, 15, and 25 mm, respectively. The diameter of LS-2 collector plug was 50.8 mm (r* = 0.765). So, in order to validate the numerical simulation method, the outlet temperature of LS-2 collector (Dp = 50.8 mm) was compared with Dudley et al. (Dudley, V., Kolb, G., Sloan, M., and Kearney, D., 1994, “SEGS LS2 Solar Collector—Test Results,” Report of Sandia National Laboratories, Report No. SANDIA94-1884) experimental results. Finally, the results show that, for r*<0.6 m, the natural convection conquers to forced convection and for r*>0.6 m the mixed convection is the dominant mechanism of heat transfer. Also, with the increase of plug diameter, friction factor decreases and the minimum amount of Nusselt number is occurred at r*=0.6 m.

scholarly journals Natural convection in tilted square cavities with triangular shaped top cold wall

1970 ◽  
Vol 39 (1) ◽  
pp. 30-39 ◽  
Author(s):  
Tamanna Sultana ◽  
Sumon Saha ◽  
Goutam Saha ◽  
Md Quamrul Islam
Keyword(s):  
Heat Transfer ◽  
Finite Element ◽  
Nusselt Number ◽  
Natural Convection ◽  
Numerical Study ◽  
Constant Heat Flux ◽  
Heat Transfer Process ◽  
Bottom Wall ◽  
Grashof Number ◽  
Inclination Angles

A numerical study of natural convection in a tilted square cavity with heated horizontal base and cold upper wall is presented. The present study is based in such a configuration where the top triangular wall of two different shapes is maintained at a constant low temperature. A constant heat flux source whose length is 20% of the total length of the cavity is discretely embedded at the left corner of the bottom wall. The remaining part of the bottom wall and the two sidewalls are considered to be adiabatic. The study includes computations for inclination angles of the cavity from 0° to 45°, where the Grashof number, Gr varies from 103 to 106. The Penalty finite element method has been used to see the effects of inclination angles and Grashof number on heat transfer process in the cavity. Results are presented in the form of streamline and isotherm plots as well as the variation of the average Nusselt number. Observation shows the significant effect of different triangular top surface on the heat transfer characteristics at the higher Grashof number and inclination angle. Keywords: Natural convection, Penalty finite element, Nusselt number, Isoflux heating. doi:10.3329/jme.v39i1.1831 Journal of Mechanical Engineering, vol. ME39, No. 1, June 2008 30-39  

Numerical Study of Flow and Heat Transfer of Heat Exchanger with Louver Baffles

2014 ◽  
Vol 721 ◽  
pp. 174-177 ◽  
Author(s):  
Hui Lai
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Energy Savings ◽  
Numerical Study ◽  
Dead Zone ◽  
Three Dimensional ◽  
Three Dimensional Model ◽  
Local Flow ◽  
Flow And Heat Transfer

This paper presents a heat exchanger of louver baffle, the establishment of a three-dimensional model, research by numerical simulation of flow and heat transfer performance of the heat exchanger baffles different louver angle, and analyzes its local temperature, and evaluated for its overall performance. The results show that louver baffle heat exchanger avoids the existence of traditional segmental baffle heat exchanger problem after baffle local flow dead zone; compared with conventional segmental baffle heat exchanger, louver baffle heat exchanger greatly reduces the heat exchanger shell side pressure drop; louver baffle heat exchanger in the unit pressure drop coefficients are higher than the segmental baffle heat exchanger, and with the baffle plate angle increases, with significant energy savings.

Investigation of Two-Phase Liquid-Droplet Flow With Particle Deposition in the Heat Exchanger

2019 ◽  
Vol 11 (5) ◽  
Author(s):  
Y. F. Yap ◽  
H. Y. Li ◽  
J. Lou ◽  
H. Y. Miao
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Heat Exchanger ◽  
Particle Deposition ◽  
Numerical Study ◽  
Tube Bundle ◽  
Liquid Droplet ◽  
Fluid Velocity ◽  
Tube Surface ◽  
Droplet Flow

This article presents a numerical study of particle deposition in two fluids, i.e., liquid and droplet flow in a single row tube bundle heat exchanger. The tubes in the heat exchanger are modeled as heating sources. Two level-set functions are used to capture the liquid-droplet interface and the liquid-deposit front. The effects of different parameters, including Damköhler number, thermal conductivity of the deposit, viscosity of the liquid, and the heating power of the tube on the flow and heat transfer, are investigated. The deposit profiles on the tube surface are analyzed. Comparison is made for the averaged Nusselt number for the case without and with deposition. It is found that the tube surface has a thicker deposit at the upstream facing side compared with that of the downstream facing side. Generally, the heat transfer rate reduces with the growth of the deposit. Under certain conditions, heat transfer can be increased because of the increase in fluid velocity due to blockage of the flow area by the deposit. The averaged Nusselt number oscillated temporally in response to the droplet movement across the tube. Generally, the temperature at the liquid-deposit front decreases with thicker deposit formed. The averaged Nusselt number along the liquid-deposit front increases to a critical value initially, and it starts to decrease with the growth of the deposit.

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