scholarly journals Forced Convection Heat Transfer for Stratospheric Airship Involved Flight State

2020 ◽  
Vol 10 (4) ◽  
pp. 1294 ◽  
Author(s):  
Houju Pei ◽  
Benben Kong ◽  
Yanlong Jiang ◽  
Hong Shi
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Forced Convection ◽  
Angle Of Attack ◽  
Convection Heat Transfer ◽  
Thermal Control ◽  
Diameter Ratio ◽  
Convection Heat ◽  
Stratospheric Airship ◽  
Forced Convection Heat Transfer

Forced convection heat transfer is a significant factor for the thermal control of a stratospheric airship. However, most of researches were conducted without considering the influence of flight state causing serious errors. In order to accurately predict the forced convection heat transfer of the stratospheric airship at an angle of attack, firstly, an empirical correlation of Nusselt number (Nu) as function of Reynolds number (Re) andlength to diameter ratio (e) is developedunder horizontal state based on a validated computational fluid dynamic (CFD) method. Then, a correction factor K, considering its angle of attack (α), is proposed to modify this correlation. The results show that: (1) Nusselt number increases with the increase of Reynolds number, decreases as the length to diameter ratio changes from 2 ~ 6, and increases as the angle of attack changes from 0° ~ 20°. (2) At higher Reynolds number, the calculated results are 30 percent higher than those of previous studies with α = 20°. (3) Compared with α and e, the effect of Re on correction factor K can be ignored, and K is a strong equation of α and e. The efficiency of heat transfer is increased by 6 percent with α = 20°. The findings of this paper provide a technical reference for the thermal control of a stratospheric airship.

Experimental Study of Forced Convection From Isothermal Circular and Square Cylinders and Toroids

1997 ◽  
Vol 119 (1) ◽  
pp. 70-79 ◽  
Author(s):  
G. Refai Ahmed ◽  
M. M. Yovanovich
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Forced Convection ◽  
Convection Heat Transfer ◽  
Reynolds Numbers ◽  
Empirical Models ◽  
Experimental Program ◽  
Convection Heat ◽  
Forced Convection Heat Transfer ◽  
Wide Range

Experimental studies of forced convection heat transfer from different body shapes were conducted to determine the effects of Reynolds number and different characteristic body lengths on the area-averaged Nusselt number. Although the bodies differed significantly in their shapes, they had approximately the same total surface area, A = 11,304 mm2 ± 5%. This ensured that for a given free stream velocity and total heat transfer rate all bodies had similar trends for the relationship of Nusselt and Reynolds numbers. The experimental program range was conducted in the Reynolds number range 104≤ReA≤105 and Prandtl number 0.71. Finally, the empirical models for forced convection heat transfer were developed. These empirical models were valid for a wide range of Reynolds numbers 0≤ReA≤105. The present experimental correlations were compared with available correlation equations and experimental data. These comparisons show very good agreement.

An Experimental Study on Forced Convection Heat Transfer From Flush-Mounted Discrete Heat Sources

1999 ◽  
Vol 121 (2) ◽  
pp. 326-332 ◽  
Author(s):  
C. P. Tso ◽  
G. P. Xu ◽  
K. W. Tou
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Source ◽  
Forced Convection ◽  
Rectangular Channel ◽  
Convection Heat Transfer ◽  
Channel Height ◽  
Air Cooling ◽  
Convection Heat ◽  
Forced Convection Heat Transfer

Experiments have been performed using water to determine the single-phase forced convection heat transfer from in-line four simulated electronic chips, which are flush-mounted to one wall of a vertical rectangular channel. The effects of the most influential geometric parameters on heat transfer including chip number, and channel height are tested. The channel height is varied over values of 0.5, 0.7, and 1.0 times the heat source length. The heat flux is set at the three values of 5 W/cm2, 10 W/cm2, and 20 W/cm2, and the Reynolds number based on the heat source length ranges from 6 × 102 to 8 × 104. Transition Reynolds numbers are deduced from the heat transfer data. The experimental results indicate that the heat transfer coefficient is affected strongly by the number of chips and the Reynolds number and weakly by the channel height. Finally, the present results from liquid-cooling are compared with other results from air-cooling, and Prandtl number scaling between air and water is investigated.

Simplified Analytical Models for Forced Convection Heat Transfer From Cuboids of Arbitrary Shape

2000 ◽  
Vol 123 (3) ◽  
pp. 182-188 ◽  
Author(s):  
J. R. Culham ◽  
M. M. Yovanovich ◽  
P. Teertstra ◽  
C.-S. Wang ◽  
G. Refai-Ahmed ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Flat Plate ◽  
Forced Convection ◽  
Convection Heat Transfer ◽  
Analytical Models ◽  
Convection Heat ◽  
Forced Convection Heat Transfer ◽  
Aspect Ratios ◽  
Diffusive Limit

Three analytical models are presented for determining laminar, forced convection heat transfer from isothermal cuboids. The models can be used over a range of Reynolds number, including at the diffusive limit where the Reynolds number goes to zero, and for a range of cuboid aspect ratios from a cube to a flat plate. The models provide a simple, convenient method for calculating an average Nusselt number based on cuboid dimensions, thermophysical properties and the approach velocity. Both the cuboid and the equivalent flat plate models are strongly dependent upon the flow path length which is bounded between two easily calculated limits. In comparisons with numerical simulations, the models are shown to be within ±6 percent over the range of 0⩽ReA⩽5000 and aspect ratios between 0 and 1.

Influence of Electric Field on Nanofluid Forced Convection Heat Transfer

2018 ◽  
pp. 389-455
Keyword(s):  
Heat Transfer ◽  
Finite Element Method ◽  
Reynolds Number ◽  
Electric Field ◽  
Forced Convection ◽  
Control Volume ◽  
Convection Heat Transfer ◽  
Convection Heat ◽  
Forced Convection Heat Transfer ◽  
Stream Function Formulation

In this chapter, the effect of electric field on forced convection heat transfer of nanofluid is presented. The governing equations are derived and presented in vorticity stream function formulation. Control volume-based finite element method (CVFEM) is employed to solve the final equations. Results indicate that the flow style depends on supplied voltage, and this effect is more sensible for low Reynolds number.

Enhanced Forced Convection Heat Transfer From a Cylinder Using Permeable Fins

2003 ◽  
Vol 125 (5) ◽  
pp. 804-811 ◽  
Author(s):  
Bassam A/K Abu-Hijleh
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Forced Convection ◽  
Convection Heat Transfer ◽  
Cross Flow ◽  
Horizontal Cylinder ◽  
Convection Heat ◽  
Transfer Rates ◽  
Forced Convection Heat Transfer ◽  
Nusselt Numbers

The problem of cross-flow forced convection heat transfer from a horizontal cylinder with multiple, equally spaced, high conductivity permeable fins on its outer surface was investigated numerically. The heat transfer characteristics of a cylinder with permeable versus solid fins were studied for several combinations of number of fins and fin height over the range of Reynolds number (5–200). Permeable fins provided much higher heat transfer rates compared to the more traditional solid fins for a similar cylinder configuration. The ratio between the permeable to solid Nusselt numbers increased with Reynolds number and fin height but tended to decrease with number of fins. This ratio was as high as 4.35 at Reynolds number of 150 and a single fin with a nondimensional height of 3.0. The use of 1–2 permeable fins resulted in much higher Nusselt number values than when using up to 18 solid fins. Such an arrangement has other benefits such as a considerable reduction in weight and cost.

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.

Forced Convection Heat Transfer from a Pair of Circular Cylinders Confined in Ventilated Enclosure

2020 ◽  
Vol 26 ◽  
pp. 104-111 ◽  
Author(s):  
Mustapha Helmaoui ◽  
Houssem Laidoudi ◽  
Azzedine Belbachir ◽  
Adel Ayad ◽  
Abedallah Ghaniam
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Forced Convection ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Vertical Wall ◽  
Convection Heat Transfer ◽  
Circular Cylinders ◽  
Convection Heat ◽  
Forced Convection Heat Transfer

This paper deals with a numerical simulation of laminar forced convection heat transfer from a pair of identical circular cylinders placed at the center of square cavity in the line array, the cavity is ventilated with single inlet and outlet ports, the inlet port is located at the middle of left vertical wall and the outlet port is located at the middle of right vertical wall. The work represents the effects of the distance between cylinders and Reynolds number on fluid flow and heat transfer rate. The governing equations of continuity, momentum and energy are solved by using finite-volume method. The obtained results are represented and discussed for following conditions: Reynolds number Re = 1 to 40, Prandtl number Pr = 7.01 and the gap distance S = 0.3L to 0.7L, where L is the cavity length. The main results are potted under the streamline and isotherm contours, the total drag coefficient and average Nusselt number of each cylinder is plotted versus studied parameters. It is found that the increase in the gap space distance between cylinders increases the heat transfer rate.

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.

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