Optimally Staggered Finned Circular and Elliptic Tubes in Turbulent Forced Convection

2006 ◽  
Vol 129 (5) ◽  
pp. 674-678 ◽  
Author(s):  
R. L. S. Mainardes ◽  
R. S. Matos ◽  
J. V. C. Vargas ◽  
J. C. Ordonez
Keyword(s):  
Heat Transfer ◽  
Forced Convection ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
External Flow ◽  
Geometric Optimization ◽  
Total Heat Transfer ◽  
Finned Tubes ◽  
Optimization Study ◽  
Dimensionless Heat

This work presents an experimental geometric optimization study to maximize the total heat transfer rate between a bundle of finned tubes in a given volume and a given external flow both for circular and elliptic arrangements, for general staggered configurations. The results are reported for air as the external fluid, in the range 2650⩽Re2b⩽10,600, where 2b is the smaller ellipse axis. Experimental optimization results for finned circular and elliptic tubes arrangements are presented. A relative heat transfer gain of up to 80% (Re2b=10,600) is observed in the elliptic arrangement optimized with respect to tube-to-tube spacings, as compared to the optimal circular one. A relative heat transfer gain of 80% is observed in the three-way optimized elliptic arrangement in comparison with the two-way optimized circular one; i.e., with respect to tube-to-tube and fin-to-fin spacings. An empirical correlation for the three-way optimized configuration was obtained to evaluate the resulting maximized dimensionless heat transfer rate.

An Analytical Study of Heat Transfer in Finite Tissue With Two Blood Vessels and Uniform Dirichlet Boundary Conditions

2005 ◽  
Vol 127 (2) ◽  
pp. 179-188 ◽  
Author(s):  
Devashish Shrivastava ◽  
Benjamin McKay ◽  
Robert B. Roemer
Keyword(s):  
Heat Transfer ◽  
Boundary Conditions ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Source Term ◽  
Dirichlet Boundary ◽  
Total Heat ◽  
Dirichlet Boundary Conditions ◽  
Total Heat Transfer ◽  
Transfer Rates

Counter-current (vessel–vessel) heat transfer has been postulated as one of the most important heat transfer mechanisms in living systems. Surprisingly, however, the accurate quantification of the vessel–vessel, and vessel–tissue, heat transfer rates has never been performed in the most general and important case of a finite, unheated/heated tissue domain with noninsulated boundary conditions. To quantify these heat transfer rates, an exact analytical expression for the temperature field is derived by solving the 2-D Poisson equation with uniform Dirichlet boundary conditions. The new results obtained using this solution are as follows: first, the vessel–vessel heat transfer rate can be a large fraction of the total heat transfer rate of each vessel, thus quantitatively demonstrating the need to accurately model the vessel–vessel heat transfer for vessels imbedded in tissues. Second, the vessel–vessel heat transfer rate is shown to be independent of the source term; while the heat transfer rates from the vessels to the tissue show a significant dependence on the source term. Third, while many previous studies have assumed that (1) the total heat transfer rate from vessels to tissue is zero, and/or (2) the heat transfer rates from paired vessels (of different sizes and at different temperatures) to tissue are equal to each other the current analysis shows that neither of these conditions is met. The analytical solution approach used to solve this two vessels problem is general and can be extended for the case of “N” arbitrarily located vessels.

Experimental Investigation on Thermal Performance of Heat Sink With Two Pairs of Embedded Heat Pipes

2007 ◽  
Author(s):  
Hsiang-Sheng Huang ◽  
Jung-Chang Wang ◽  
Sih-Li Chen
Keyword(s):  
Heat Transfer ◽  
Thermal Resistance ◽  
Heat Transfer Rate ◽  
Thermal Performance ◽  
Heat Sink ◽  
Transfer Rate ◽  
Heat Pipes ◽  
Total Heat ◽  
Heating Power ◽  
Total Heat Transfer

This article provides an experimental method to study the thermal performance of a heat sink with two pairs (outer and inner pair) of embedded heat pipes. The proposed method can determine the heat transfer rate of the heat pipes under various heating power of the heat source. A comprehensive thermal resistance network of the heat sink is also developed. The network estimates the thermal resistances of the heat sink by applying the thermal performance test result. The results show that the outer and inner pairs of heat pipes carries 21% and 27% of the total heat transfer rate respectively, while 52% of the heating power is dissipated from the base plate to the fins. The dominated thermal resistance of the heat sink is the base to heat pipes resistance which is strongly affected by the thermal performance of the heat pipes. The total thermal resistance of the heat sink shows the lowest value, 0.23°C/W, while the total heat transfer rate of the heat sink is 140W and the heat transfer rate of the outer and inner pairs of heat pipes is 30W and 38 W, respectively.

Thermal Assessment of Forced Convection Through Metal Foam Heat Exchangers

2011 ◽  
Vol 133 (11) ◽  
Author(s):  
A. Tamayol ◽  
K. Hooman
Keyword(s):  
Heat Transfer ◽  
Thermal Resistance ◽  
Forced Convection ◽  
Heat Transfer Rate ◽  
Heat Exchangers ◽  
Transfer Rate ◽  
Metal Foam ◽  
Convection Heat Transfer ◽  
Geometrical Parameters ◽  
Convection Heat

Using a thermal resistance approach, forced convection heat transfer through metal foam heat exchangers is studied theoretically. The complex microstructure of metal foams is modeled as a matrix of interconnected solid ligaments forming simple cubic arrays of cylinders. The geometrical parameters are evaluated from existing correlations in the literature with the exception of ligament diameter which is calculated from a compact relationship offered in the present study. The proposed, simple but accurate, thermal resistance model considers: the conduction inside the solid ligaments, the interfacial convection heat transfer, and convection heat transfer to (or from) the solid bounding walls. The present model makes it possible to conduct a parametric study. Based on the generated results, it is observed that the heat transfer rate from the heated plate has a direct relationship with the foam pore per inch (PPI) and solidity. Furthermore, it is noted that increasing the height of the metal foam layer augments the overall heat transfer rate; however, the increment is not linear. Results obtained from the proposed model were successfully compared with experimental data found in the literature for rectangular and tubular metal foam heat exchangers.

Analytical Solutions of Heat Transfer and Film Thickness in Thin-Film Evaporation

2013 ◽  
Vol 135 (3) ◽  
Author(s):  
Chunji Yan ◽  
H. B. Ma
Keyword(s):  
Thin Film ◽  
Heat Transfer ◽  
Heat Flux ◽  
Film Thickness ◽  
Thermal Resistance ◽  
Heat Transfer Rate ◽  
Analytical Solutions ◽  
Transfer Rate ◽  
Total Heat ◽  
Total Heat Transfer

A mathematical model predicting heat transfer and film thickness in thin-film region is developed herein. Utilizing dimensionless analysis, analytical solutions have been obtained for heat flux distribution, total heat transfer rate per unit length, location of the maximum heat flux and ratio of conduction thermal resistance to convection thermal resistance in the evaporating film region. These analytical solutions show that the maximum dimensionless heat flux is constant which is independent of the superheat. Maximum total heat transfer rate is determined for a given film region. The ratio of conduction thermal resistance to convection thermal resistance is a function of dimensionless film thickness. This work will lead to a better understanding of heat transfer and fluid flow occurring in the evaporating film region.

scholarly journals Experimental Study for Counter to Cross Flow Air Cooled Heat Exchanger in Concentric Tube using Rectangular Copper Fins Spacing with Internal Spiral Grooving

2021 ◽  
pp. 203-208
Author(s):  
Rakesh Kumar Tiwari ◽  
Ajay Singh ◽  
Parag Mishra
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Natural Convection ◽  
Heat Exchanger ◽  
Forced Convection ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Cross Flow ◽  
Variable Number ◽  
Air Cooled Heat Exchanger

In this manuscript we have presented eight variation of Air-Cooled Heat Exchanger (ACHE) design with internal spiral grooving, all of them are having variable number of rectangular copper fins with different distances between the fins. In the proposed design we get the value of heat transfer rate of a counter to cross flow ACHE is 7833.77 watt, 4068.13 watt, 2736.95 watt, 2161.49 watt, 1802.89 watt, 1546.44 watt, 1336.51 watt and 1165.74 watt in natural convection (without fan) for 0.5 cm, 1.0 cm, 1.5 cm, 2.0 cm, 2.5 cm, 3.0 cm, 3.5 cm and 4.0 cm respectively. Then again, value of rate of heat transfer in forced convection (with fan) are 8007.46 watt, 4084.81 watt, 2754.69 watt, 2205.98 watt, 1809.24 watt, 1555.39 watt, 1352.88 watt and 1172.78 watt for 0.5 cm, 1.0 cm, 1.5cm, 2.0 cm, 2.5 cm, 3.0 cm, 3.5 cm and 4.0 cm respectively.

An Investigation of Heat Transfer and Pressure Drop Enhancement of Various Perforated Circular Finned Tubes at Different Tube Tilt Angles

2021 ◽  
pp. 10295-10338
Author(s):  
Yahya Yaser Shanyour AL-Salman, Ali Sabri Abbas
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Heat Transfer Rate ◽  
Tilt Angle ◽  
Transfer Rate ◽  
Performance Criterion ◽  
Finned Tube ◽  
Finned Tubes ◽  
Global Performance

The thermal and flow performance of the circular annular finned tube heat exchanger with perforated fins were investigated numerically using ANSYS Fluent 2020 software, RNG k-e model with enhanced wall treatment, global performance criterion was introduced as evaluation factor of the heat exchanger performance, the parameters to be investigated were the number of holes, size of hole, tilt angle of the finned tube, fin height and spacing between fins. Agreement was found with literature that the tilt angle causes increase in heat transfer rate and increase in the pressure drop as well, but the change the global performance criterion as function to tilt angle depends on the fin heights, for higher fin heights the effective change of the pressure drop become greater than the increase in the heat transfer rate and the contrast occur in the cases of smaller fin heights, we have found that the perforation in tilted annular circular finned tubes causes an increase in the heat transfer rate and an enhancement in the total heat exchanger performance, increasing the number of holes will enhance the performance of the heat exchanger and the spacing increase reduces the heat exchanger performance.

scholarly journals Free and Forced Convective Heat Transfer through a Nanofluid with Two Dimensions past Stretching Vertical Plate

2020 ◽  
Vol 7 (3) ◽  
Author(s):  
B. Sailaja ◽  
G. Srinivas ◽  
B.S. Babu
Keyword(s):  
Heat Transfer ◽  
Heat Source ◽  
Convective Heat Transfer ◽  
Forced Convection ◽  
Heat Transfer Rate ◽  
Convective Heat ◽  
Transfer Rate ◽  
Vertical Plate ◽  
Two Dimensions ◽  
Forced Convective Heat Transfer

The present study focus on both free and forced convective heat transfer through a nanofluid in two dimensions past stretching vertical plate. This free and forced convective heat transfer in Cu–water Nanofluid past permeable flat vertical semi-infinite plate was due to high conductivity and its occurrence. In this paper magnetic field and also heat source were considered. In graphs the effect on various parameters such as Reynolds number (Re) , solid volume fraction (φ), magnetic field parameter (M), inclination angle of the plate (γ ), heat source parameter (Qh), on linear velocity (U), vertical velocity (V) and temperature (θ) were exhibited. The profile of every governing parameter is displayed for natural as well as forced convection by considering the Ar >> 1 and Ar << 1 respectively. This rate of heat transfer in forced convection is more than equivalent in free convection. So these problems have several applications in engineering and petroleum industries such as electroplating, chemical processing of heavy metals and solar water heaters. Inertial force reducing the heat transfer rate in natural convection but the enhancement of Nu observed in forced convection. The composition of metal particles enhances the heat transfer rate in both convections, which emphasizes the nanofluid significance. Lorentz force is enhancing the heat transfer rate slightly. Heat source obviously increase the rate of heat transfer in both convections. The present paper aims to study the convective high temperature transfer of nanofluids into which viscosity proposed by Einstein and thermal conductivity proposed by Corcione were used.

scholarly journals Enhancement of Temperature Distribution and Heat Transfer Coefficient of Ribbed Tube by Simulation

2021 ◽  
Vol 7 (1) ◽  
pp. 21-28
Author(s):  
Rahul Kunar ◽  
Dr Sukul Lomash
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Temperature Distribution ◽  
Transfer Coefficient ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Flow Analysis ◽  
Total Heat ◽  
Total Heat Transfer ◽  
The Heat Transfer Coefficient

The heat transfer from surface may in general be enhanced by increasing the heat transfer coefficient between a surface and its surrounding or by increasing heat transfer area of the surface or by both. The main objective of the study and calculate the total heat transfer coefficient. Improve the heat transfer rate by using ANSYS CFD. During the CFD calculations of the flow in internally ribbed tubes. And calculated the temperature distribution and pressure inside the tube by using ansys. The model was created using CatiaV5 and meshed with Ansys, and the flow analysis is done with Ansys 19.2. The results showing that the heat transfer is increased. The enthalpy and temperature increase with flow is advancing when compare with normal boiler tube. In this study the total heat transfer rate of the pipe increase with the increase the rib height. Total heat transfer rate increase up to 7.7kw. The study show that the improvement in furnace heat transfer can be achieved by changing the internal rib design.

Theory of Heat Transfer From a Surface Covered With Hair

1990 ◽  
Vol 112 (3) ◽  
pp. 662-667 ◽  
Author(s):  
A. Bejan
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Air Flow ◽  
The Body ◽  
Total Heat ◽  
Uniform Density ◽  
Total Heat Transfer ◽  
Optimum Diameter ◽  
Hair Strand

This paper describes the fundamental mechanisms of heat transfer through a surface covered with perpendicular hair strands of uniform density. An air flow parallel to the skin seeps through the spaces created between the hair strands. It is shown that the total heat transfer rate from the surface is due to two contributions: (i) the heat conducted through the hair strands, which act as fins, and (ii) the heat convected from the bare portions of the skin. When the air flow is slow enough to conform to the Darcy regime, there exists an optimum hair strand diameter for which the total heat transfer rate is minimum. The optimum diameter increases as the square root of the length swept by the air flow, that is the linear size of the body of the animal covered with hair.

Coupled Free and Forced Convection Heat Transfer in a Porous Enclosure Saturated by Nanofluid with Irregular Temperature Distributions on Sidewalls

2017 ◽  
Vol 15 (6) ◽  
Author(s):  
M. Muthtamilselvan ◽  
S. Sureshkumar ◽  
Deog Hee Doh
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Volume Fraction ◽  
Amplitude Ratio ◽  
Solid Volume Fraction ◽  
Side Wall ◽  
Darcy Number ◽  
Total Heat Transfer ◽  
Phase Deviation

Abstract A two dimensional steady and laminar mixed convection flow in lid-driven porous cavity filled with Cu-water nanofluid is presented in this numerical investigation. The vertical side walls are considered with two spatially varying sinusoidal temperature distributions of different amplitude ratios and phase deviations while the horizontal walls are thermally insulated. The transport equations are solved using finite volume method on a uniformly staggered grid system. The variations of fluid flow, heat transfer, mid-plane velocity, and Nusselt number were discussed over a wide range of Richardson number $(Ri)$ , Darcy number $(Da)$ , porosity $(\epsilon)$ , amplitude ratio $(\epsilon_a)$ , phase deviation $(\phi)$ , and solid volume fraction $(\chi)$ . The results show that the total heat transfer rate increases on increasing Darcy number, amplitude ratio, and solid volume fraction with fixed $Ri$ . For $\phi=\frac{3\pi}{4}$ , the average Nusselt number gets its maximum value when the natural convection dominates. It is found that for $Ri =0.01$ and $1$ , the total heat transfer rate decreases on increasing porosity whereas for $Ri=100$ it is contradictory. It is also observed that the heat transfer is affected mainly on the right side wall where the phase deviation varies from $0$ to $\pi$ . But the effect of $\phi$ is not significant on the left side wall. The sinusoidal temperature distribution along the sidewalls gives better heat transfer rate than the uniform temperature.

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