Different Approaches to Generalizing Experimental Data on Convective Heat Transfer of a Single Oval-Shaped Tube in Cross Flow

Abstract This paper presents an experimental investigation of the forced convective heat transfer of FC-72 in vertical tubes at various velocities, inlet temperatures, and tube sizes. Exponentially escalating heat inputs were supplied to the small tubes with inner diameters of 1, 1.8, and 2.8 mm and effective heated lengths between 30.1 and 50.2 mm. The exponential periods of heat input range from 6.4 to 15.5 s. The experimental data suggest that the convective heat transfer coefficients increase with an increase in flow velocity and µ/µw (refers to the viscosity evaluated at the bulk liquid temperature over the liquid viscosity estimated at the tube inner surface temperature). When tube diameter and the ratio of effective heated length to inner diameter decrease, the convective heat transfer coefficients increase as well. The experimental data were nondimensionalized to explore the effect of Reynolds number (Re) on forced convection heat transfer coefficient. It was found that the Nusselt numbers (Nu) are influenced by the Re for d = 2.8 mm in the same pattern as the conventional correlations. However, the dependences of Nu on Re for d = 1 and 1.8 mm show different trends. It means that the conventional heat transfer correlations are inadequate to predict the forced convective heat transfer in minichannels. The experimental data for tubes with diameters of 1, 1.8, and 2.8 mm were well correlated separately. And, the data agree with the proposed correlations within ±15%.

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Comparison of the results of modeling convective heat transfer in turbulent flows with experimental data

Journal of Engineering Physics and Thermophysics ◽

10.1007/s10891-010-0420-5 ◽

2010 ◽

Vol 83 (5) ◽

pp. 967-976 ◽

Cited By ~ 1

Author(s):

A. I. Fomichev

Keyword(s):

Heat Transfer ◽

Experimental Data ◽

Convective Heat Transfer ◽

Turbulent Flows ◽

Convective Heat ◽

Comparison Of The Results

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Conjugate Heat Transfer CFD Predictions of Impingement Jet Array Flat Wall Cooling Aerodynamics With Single Sided Flow Exit

Volume 3B: Heat Transfer ◽

10.1115/gt2013-95343 ◽

2013 ◽

Cited By ~ 3

Author(s):

Abubakar M. El-Jummah ◽

Gordon E. Andrews ◽

John E. J. Staggs

Keyword(s):

Heat Transfer ◽

Convective Heat Transfer ◽

Convective Heat ◽

Conjugate Heat Transfer ◽

Cross Flow ◽

Diameter Ratio ◽

Significant Feature ◽

Axial Distance ◽

Impingement Jet ◽

The Cross

Conjugate heat transfer CFD studies were undertaken on impingement square jet arrays with self induced crossflow in the impingement gap with a single sided exit. The aim was to understand the aerodynamic interactions that result in the deterioration of heat transfer with axial distance, whereas the addition of duct flow heat transfer would be expected to lead to an increase in heat transfer with axial distance. A square array of impingement holes was investigated for a common geometry investigated experimentally, pitch to diameter ratio X/D of 5 and impingement gap to diameter ratio Z/D of 3.3 for 11 rows of holes in the crossflow direction. A metal duct wall was used as the impingement surface with an applied heat flux of 100kW/m2, which for a gas turbine combustor cooling application operating at steady state with a temperature difference of ∼450K corresponds to a convective heat transfer coefficient of ∼200 W/m2K. A key feature of the predicted aerodynamics was recirculation in the plane of the impingement jets normal to the cross-flow, which produced heating of the impingement jet wall. This reverse flow jet was deflected by the cross flow which had its peak velocity in the plane between the high velocity impingement jets. The cross-flow interaction with the impingement jets reduced the interaction between the jets on the surface, with lower surface turbulence as a result and this reduced the surface convective heat transfer. A significant feature of the predictions was the interaction of the cross-flow aerodynamics with the impingement jet wall and associated heat transfer to that wall. The results showed that the deterioration in heat transfer with axial distance was well predicted, together with predictions of the impingement wall surface temperature gradients.

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