The Effect of Surface Thermal Radiation on Heat Transfer in a Ventilated Cavity

2020 ◽  
Vol 143 (1) ◽  
Author(s):  
J. M. A. Navarro ◽  
J. F. Hinojosa ◽  
A. Piña-Ortiz ◽  
J. Xamán
Keyword(s):  
Heat Transfer ◽  
Thermal Radiation ◽  
Turbulence Models ◽  
Transfer Model ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Experimental Heat ◽  
Ventilated Cavity ◽  
Experimental Heat Transfer ◽  
Effect Of Surface

Abstract In this work, experimental and numerical results were obtained to analyze the effect of surface thermal radiation on heat transfer by mixed convection in a ventilated cavity. Experimental temperature profiles were obtained at six different depths and heights consisting of 14 thermocouples each. Five turbulence models were evaluated against experimental data. The radiative heat transfer model was solved with the discrete ordinate method. The effect of thermal radiation on experimental heat transfer coefficients is significant; it increases between 87% (Re = 30,372 and Ra = 3.04 × 1011) and 110% (Re = 6021 and Ra = 2.27 × 1011), when the emissivity of the walls increases from 0.03 to 0.98.

Experimental Heat Transfer Coefficients from Ice-Roughened Surfaces for Aircraft Deicing Design

1999 ◽  
Vol 36 (6) ◽  
pp. 948-956 ◽  
Author(s):  
Nihad Dukhan ◽  
K. C. Masiulaniec ◽  
Kenneth J. De Witt ◽  
G. James Van Fossen
Keyword(s):  
Heat Transfer ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Experimental Heat ◽  
Experimental Heat Transfer

Experimental Study of Condensation Inside a Horizontal Single Square Minichannel

2009 ◽  
Author(s):  
Marko Matkovic ◽  
Stefano Bortolin ◽  
Alberto Cavallini ◽  
Davide Del Col
Keyword(s):  
Heat Transfer ◽  
Mass Velocity ◽  
Saturation Temperature ◽  
External Heat ◽  
Copper Tube ◽  
Transfer Coefficients ◽  
External Heat Transfer ◽  
Heat Transfer Coefficients ◽  
Experimental Heat ◽  
Experimental Heat Transfer

This work is aimed at presenting experimental heat transfer coefficients measured during condensation inside a single square cross section minichannel, having a 1.18 mm side length. The experimental heat transfer coefficients are compared to the ones previously obtained in a circular minitube. This subject is particularly interesting since most of the mini and microchannels used in practical applications have non circular cross sections. The test section used in the present work is obtained from a thick wall copper tube which is machined to draw a complex passage for the water; its geometry has been studied with the aim of increasing the external heat transfer area and thus decreasing the external heat transfer resistance. This experimental technique allows to measure directly the temperature in the tube wall and in the water channel. The heat flux is determined from the temperature profile of the coolant in the measuring sector. The wall temperature is measured by means of thermocouples embedded in the copper tube, while the saturation temperature is obtained from the saturation pressure measured at the inlet and outlet of the measuring sector. On the whole, more than seventy thermocouples have been placed in the 23 cm long measuring section. Tests have been performed with R134a at 40°C saturation temperature, at mass velocities ranging between 200 and 800 kg m−2s−1. As compared to the heat transfer coefficients measured in a circular minichannel, in the square minichannel the authors find a heat transfer enhancement at the lowest values of mass velocity; this must be due to the effect of the surface tension. No heat transfer coefficient increase has been found at the highest values of the mass velocity where condensation is shear stress dominated.

A Model for Condensation Inside Minichannels

2005 ◽  
Author(s):  
Alberto Cavallini ◽  
Davide Del Col ◽  
Luca Doretti ◽  
Marko Matkovic ◽  
Luisa Rossetto ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Transfer Model ◽  
Entrainment Rate ◽  
Transfer Coefficients ◽  
Experimental Conditions ◽  
Pressure Drops ◽  
Heat Transfer Coefficients ◽  
Experimental Heat ◽  
Channel Tube ◽  
Predicted Values

Present authors have measured heat transfer coefficients (Cavallini et al. [1, 2]) and pressure drops (Cavallini et al. [3, 4]) during condensation of R134a, R410A and R236ea inside a flat multiport mini-channel tube with a 1.4 mm hydraulic diameter. The experimental heat transfer coefficients (α) have been compared against correlations available in the literature and no correlation was able to predict α in all the experimental conditions. The present paper suggests a heat transfer model for condensation inside minichannels, based on analogy between heat and momentum transfer. The proposed procedure takes into account the effect of the entrainment rate of droplets from the liquid film. The model is applied to the annular, annularmist flow. A simplified version of the model is also presented. Comparisons between present authors’ data and predicted values show the satisfactory behaviour of both versions of the models.

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