Experimental study for Convection Heat Transfer from Helical Coils with the Same Outer Surface Area and Different Coil Geometry

2021 ◽  
pp. 1-17
Author(s):  
Amr M. Hassaan ◽  
Hesham Mohamad Mostafa
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Surface Area ◽  
Outer Surface ◽  
Convection Heat Transfer ◽  
Heat Transfer Process ◽  
Convection Heat ◽  
Helical Coils

Abstract An experimental study is done to study the convection heat transfer from the outer surface of a group of helical coils that have the same external surface area which is (0.1 m2). These coils are wrapped to form different helical coils with different geometrical dimensions. Five pipe diameters are used in this study also; the pipes are wrapped by different values of coil diameter ranges from 75- 300 mm. The effect of the coil pitch on the heat transfer process has been studied, to reach the value that gives the best performance for each coil. The heat source is steam flowing inside the coil. These coils are tested at different air speeds inside the wind tunnel, which made the Reynolds number (Re) changes from 239 - 3990. The obtained results showed that the Nusselt number enhances with the increase of D/do and P/do to reach the maximum value at the optimum values of D/do and P/do then the Nusselt number begins to decrease. Nusselt number increases with the increase of Reynolds number under all conditions. A correlation for Nusselt number as a function of Reynolds number and the other studied operating parameters reported. By comparing this work with literature, one can find an acceptable agreement in the results.

scholarly journals 3D Numerical simulation of turbulent heat transfer and Fe3O4/nanofluid annular flow in sudden enlargement

2021 ◽  
Vol 321 ◽  
pp. 04014
Author(s):  
Hussein Togun
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Heat Transport ◽  
Annular Flow ◽  
Volume Concentration ◽  
Convection Heat Transfer ◽  
Turbulent Heat Transfer ◽  
Recirculation Region ◽  
Convection Heat

In this paper, 3D Simulation of turbulent Fe3O4/Nanofluid annular flow and heat transfer in sudden expansion are presented. k-ε turbulence standard model and FVM are applied with Reynolds number different from 20000 to 50000, enlargement ratio (ER) varied 1.25, 1.67, and 2, , and volume concentration of Fe3O4/Nanofluid ranging from 0 to 2% at constant heat flux of 4000 W/m2. The main significant effect on surface Nusselt number found by increases in volume concentration of Fe3O4/Nanofluid for all cases because of nanoparticles heat transport in normal fluid as produced increases in convection heat transfer. Also the results showed that suddenly increment in Nusselt number happened after the abrupt enlargement and reach to maximum value then reduction to the exit passage flow due to recirculation flow as created. Moreover the size of recirculation region enlarged with the rise in enlargement ratio and Reynolds number. Increase of volume Fe3O4/nanofluid enhances the Nusselt number due to nanoparticles heat transport in base fluid which raises the convection heat transfer. Increase of Reynolds number was observed with increased Nusselt number and maximum thermal performance was found with enlargement ratio of (ER=2) and 2% of volume concentration of Fe3O4/nanofluid. Further increases in Reynolds number and enlargement ratio found lead to reductions in static pressure.

Heat Transfer by Mixed Convection Opposing Laminar Flow From the Inside Surface of Uniformly Heated Inclined Circular Tube

2006 ◽  
Author(s):  
H. Mohammed ◽  
T. Yusaf
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Mixed Convection ◽  
Flow Direction ◽  
Convection Heat Transfer ◽  
Heat Transfer Process ◽  
Secondary Flows ◽  
Opposed Flow ◽  
Wide Range

This paper aims to investigate the effect of the flow pattern on the mixed convection heat transfer. A 28 thermocouples wire were installed along a 900mm copper tube to measure the temperature distribution. Three insulation layers of fiber glass, asbestos and gypsum were used to minimize to heat lost to the surrounding. A forced convection at the entrance region of a fully developed opposing laminar air flow was investigated to evaluate the flow direction effect on the Nusselt number. The investigation covered a wide range of Reynolds number from 410 to 1600 and heat flux varied from 63W/m2 to 1260W/m2, with different angles of tube inclination of 30°, 45°, 60°, and 90°. It was found that the surface temperature variation along the tube for opposed flow higher than the assisted flow but lower than the horizontal orientation. The Reynolds number has a significant effect on Nusselt number in opposed flow while the effect of Reynolds number was found to be small in the case of assisted flow. The Nusselt number values were lower for opposed flow than the assisted flow. The temperature profiles results have revealed that the secondary flows created by natural convection have a significant effect on the heat transfer process. The obtained average Nusselt number values were correlated by dimensionless groups as Log Nu against Log Ra/Re.

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.

scholarly journals Heat Transfer Performance of Different Fluids During Natural Convection in Enclosures with Varying Aspect Ratios

2021 ◽  
Vol 287 ◽  
pp. 03010
Author(s):  
Rajashekhar Pendyala ◽  
Suhaib Umer Ilyas ◽  
Yean Sang Wong
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Natural Convection ◽  
Heat Transfer Performance ◽  
Convection Heat Transfer ◽  
Heat Transfer Process ◽  
Natural Convection Heat Transfer ◽  
Transfer Performance ◽  
Convection Heat ◽  
Aspect Ratios

The heat transfer process takes place in numerous applications through the natural convection of fluids. Investigations of the natural convection heat transfer in enclosures have gained vital importance in the last decade for the improvement in thermal performance and design of the heating/cooling systems. Aspect ratios (AR=height/length) of the enclosures are one of the crucial factors during the natural convection heat transfer process. The investigated fluids consisting of air, water, engine oil, mercury, and glycerine have numerous engineering applications. Heat transfer and fluid flow characteristics are studied in 3-dimensional rectangular enclosures with varying aspect ratios (0.125 to 150) using computational fluid dynamics (CFD) simulations. Studies are carried out using the five different fluids having Prandtl number range 0.01 to 4500 in rectangular enclosures with the hot and cold surface with varying temperature difference 20K to 100K. The Nusselt number and heat transfer coefficients are estimated at all conditions to understand the dependency of ARs on the heat transfer performance of selected fluids. Temperature and velocity profiles are compared to study the flow pattern of different fluids during natural convection. The Nusselt number correlations are developed in terms of aspect ratio and Rayleigh number to signify the natural convection heat transfer performance.

scholarly journals Investigation Of Forced Convection Heat Transfer From A Heater Mounted Ina Cavity Wall Using Various Nanofluids

2019 ◽  
Vol 128 ◽  
pp. 07002
Author(s):  
R. Kanna ◽  
Sayed Sayeed Ahmad ◽  
P. Venkata Reddy ◽  
Chithirai Pon Selvan ◽  
Tale ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Forced Convection ◽  
Volume Fraction ◽  
Convection Heat Transfer ◽  
Cavity Wall ◽  
Main Stream ◽  
Convection Heat ◽  
Forced Convection Heat Transfer

Forced convection heat transfer from heater mounted in a cavity wall is investigated to reveal the relation among nanofluid properties. The base fluid is considered as water. The present study is focused on forced convection heat transfer from square heater subject to inflow and outflow inside a squarecavity. The interesting physics will be reported in connection with volume fraction, Reynolds number and nanomaterial properties. It is found that for a particular Reynolds number when nanomaterial is introduced the local heat transfer is increased. The wall attached vortex attributes a constant Nusselt number. It is also noticed that when the heater wall is subject to combination of vortex and main stream fluid results high Nusselt number than heat transfer due to wall attached vortices. Nanofluid results high Nusselt number for the same Reynolds number.

Numerical Analysis of Natural Convection Heat Transfer From a Vertical Hollow Cylinder Suspended in Air

2018 ◽  
Vol 140 (5) ◽  
Author(s):  
Swastik Acharya ◽  
Sumit Agrawal ◽  
Sukanta K. Dash
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Natural Convection ◽  
Rayleigh Number ◽  
Hollow Cylinder ◽  
Outer Surface ◽  
Average Nusselt Number ◽  
Convection Heat Transfer ◽  
Natural Convection Heat Transfer ◽  
Convection Heat

Natural convection heat transfer from a vertical hollow cylinder suspended in air has been analyzed numerically by varying the Rayleigh number (Ra) in the laminar (104 ≤ Ra ≤ 108) regime. The simulations have been carried out by changing the ratio of length to pipe diameter (L/D) in the range of 0.05 ≤ L/D≤20. Full conservation equations have been solved numerically for a vertical hollow cylinder suspended in air using algebraic multigrid solver of fluent 13.0. The flow and the temperature field around the vertical hollow cylinder have been observed through velocity vectors and temperature contours for small and large L/D. It has been found that the average Nusselt number (Nu) for vertical hollow cylinder suspended in air increases with the increase in Rayleigh number (Ra) and the Nu for both the inner and the outer surface also increases with Ra. However, with the increase in L/D, average Nu for the outer surface increases almost linearly, whereas the average Nu for the inner surface decreases and attains asymptotic value at higher L/D for low Ra. In this study, the effect of parameters like L/D and Ra on Nu is analyzed, and a correlation for average Nusselt number has been developed for the laminar regime. These correlations are accurate to the level of ±6%.

scholarly journals Numerical investigation of laminar forced convection heat transfer in rectangular channels with different block geometries using nano-fluids

2017 ◽  
Vol 21 (5) ◽  
pp. 2129-2138 ◽  
Author(s):  
Saeed Foroutani ◽  
Alireza Rahbari
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Forced Convection ◽  
Average Nusselt Number ◽  
Volume Fraction ◽  
Convection Heat Transfer ◽  
Convection Heat ◽  
Forced Convection Heat Transfer ◽  
Triangular Block

This research investigates the laminar steady-forced convection heat transfer of a Cu-water nanofluid in a 2-D horizontal channel with different block geometries attached to the bottom wall. The block geometries assumed in this research are triangular and curve blocks. The governing equations associated with the required boundary conditions are solved using finite volume method based on the SIMPLE technique and the effects of Reynolds number, nanofluid volume fraction, block geometry, and the numbers of blocks on the local and average Nusselt numbers are explored. The obtained results show that nanoparticles can effectively enhance the heat transfer in a channel. Furthermore, the local and average Nusselt number distribution is strongly dependent on the block geometry. As observed, the heat transfer augments with the increase in the Reynolds number and nanofluid volume fraction for both block geometries. It is also concluded that the average Nusselt number of the curve block is higher than that of the triangular block for different Reynolds numbers which declares the importance of the block geometry in the heat transfer enhancement.

Numerical Investigation of Forced Convection Heat Transfer from Offset Square Cylinders Placed in a Three Dimensional Confined Channel

2015 ◽  
Vol 813-814 ◽  
pp. 729-735 ◽  
Author(s):  
Paulraj Maheandera Prabu ◽  
Mahadevan Sivasubramanian ◽  
P. Rajesh Kanna ◽  
M. Uthayakumar ◽  
K.P. Padmanaban
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Nusselt Number ◽  
Forced Convection ◽  
Convection Heat Transfer ◽  
Flow Simulation ◽  
Convection Heat ◽  
Forced Convection Heat Transfer ◽  
Square Cylinders ◽  
Confined Channel

Abstract-Flow over two offset square cylinders in a confined channel is simulated for different Reynoldsnumber to reveal the forced convection heat transfer from the heated square cylinders to the ambientfluid. The bottom of the cylinder is maintained at constant temperature. The distance between thecylinder in normal direction as well as transverse direction are fixed as 2d and the blockage ratio is fixedas 0.167. Heat transfer from the cylinders to the ambient fluid as well as conducted within solid wallthrough conjugate interface boundary investigated in connection with Reynolds number are reportedfor both steady and periodic flow. Simulation is carried out for Reynolds number varies from 10 to100 for the fluid as air with Prandtl number as 0.71. The isotherm contours, local Nusselt number andaverage Nusselt number are reported for various Reynolds number. The stagnation zone results higherNusselt number than remaining walls and rear wall results lowest Nusselt number. The downstreamcylinder results higher Nusselt number than the upstream cylinder. The top and bottom surfaceNusselt number from upstream and downstream cylinder are not analogous to single cylinder placed ina channel.

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