scholarly journals Heat transfer degradation during condensation of non-azeotropic mixtures

2017 ◽  
Vol 923 ◽  
pp. 012017 ◽  
Author(s):  
M Azzolin ◽  
A Berto ◽  
S Bortolin ◽  
D Del Col
Keyword(s):  
Heat Transfer ◽  
Azeotropic Mixtures ◽  
Heat Transfer Degradation

Investigation of MHD RANS Modeling Base on DNS Database Under the Advanced Blanket Design Conditions Utilized Molten Salt

2014 ◽  
Author(s):  
Naoki Osawa ◽  
Yoshinobu Yamamoto ◽  
Tomoaki Kunugi
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Turbulence Model ◽  
Turbulent Channel Flow ◽  
Turbulent Heat Transfer ◽  
Navier Stokes ◽  
Turbulent Heat ◽  
Mhd Turbulence ◽  
Rans Modeling ◽  
Heat Transfer Degradation

In this study, validations of Reynolds Averaged Navier-Stokes Simulation (RANS) based on Kenjeres & Hanjalic MHD turbulence model (Int. J. Heat & Fluid Flow, 21, 2000) coupled with the low-Reynolds number k-epsilon model have been conducted with the usage of Direct Numerical Simulation (DNS) database. DNS database of turbulent channel flow imposed wall-normal magnetic field on, are established in condition of bulk Reynolds number 40000, Hartmann number 24, and Prandtl number 5. As the results, the Nagano & Shimada model (Trans. JSME series B. 59, 1993) coupled with Kenjeres & Hanjalic MHD turbulence model has the better availability compared with Myong & Kasagi model (Int. Fluid Eng, 109, 1990) in estimation of the heat transfer degradation in MHD turbulent heat transfer.

scholarly journals Heat transfer to non-azeotropic mixtures of refrigerants flowing in a horizontal evaporator tube.

1990 ◽  
Vol 56 (524) ◽  
pp. 1084-1089 ◽  
Author(s):  
Suguru YOSHIDA ◽  
Takashi MATSUNAGA ◽  
Hideo MORI ◽  
Katsumi OHISHI
Keyword(s):  
Heat Transfer ◽  
Azeotropic Mixtures

scholarly journals Heat transfer at nucleate boiling of non-azeotropic mixtures

2017 ◽  
Vol 891 ◽  
pp. 012034
Author(s):  
N N Mezentseva ◽  
V A Mukhin ◽  
I V Mezentsev
Keyword(s):  
Heat Transfer ◽  
Nucleate Boiling ◽  
Azeotropic Mixtures

Combination of Impingement and Trip Strips for Combustor Liner Backside Cooling

Volume 3 ◽  
2004 ◽  
Author(s):  
Ryan Hebert ◽  
Srinath V. Ekkad ◽  
Vivek Khanna
Keyword(s):  
Heat Transfer ◽  
Cross Flow ◽  
Jet Impingement ◽  
Reynolds Numbers ◽  
Combination Technique ◽  
Impingement Jet ◽  
Impingement Heat Transfer ◽  
Flow Effects ◽  
Heat Transfer Degradation ◽  
Cooling Air

Effective cooling of modern low NOx combustor liners is achieved through combinations of impingement and other heat transfer enhancement methods. In the present study, a combination of impingement and trip strips is studied to determine the optimum location of trip strips with respect to impingement jet arrays. Heat transfer with pure impingement has degradation downstream due to increased cross-flow effects. To counter the cross-flow induced heat transfer degradation, a combination technique wherein impingement is combined with ribs placed in between impingement rows or downstream of the impingement array is studied. Three configurations with increased rib placements and reduced impingement holes are studied and compared with pure impingement cases for the same jet Reynolds number. Three jet Reynolds numbers are studied for Rej = 10000, 20000, and 30000. Detailed heat transfer distributions are obtained using the transient liquid crystal technique. Results show that the presence of ribs increases jet impingement heat transfer on the surface with lower mass flows. The effectiveness of the combination ribs and impingement can provide higher heat transfer with reduced cooling air requirements.

Effect of Gravitational Orientation on Flow Boiling of Water in 1054 × 197 µm Parallel Minichannels

2004 ◽  
Author(s):  
Satish G. Kandlikar ◽  
Prabhu Balasubramanian
Keyword(s):  
Heat Transfer ◽  
High Speed ◽  
Flow Boiling ◽  
High Heat ◽  
Operating Conditions ◽  
Microgravity Environment ◽  
High Heat Flux ◽  
Two Phase ◽  
Mass Fluxes ◽  
Heat Transfer Degradation

Microchannels and minichannels are being considered for high heat flux applications under microgravity environment in space missions. An experimental study is undertaken to determine the effect of gravitational orientation on flow boiling characteristics of water in a set of six parallel minichannels, each 1054 μm wide by 197 μm deep and 63.5 mm long with a hydraulic diameter of 333 μm. Three orientations — horizontal, vertical downflow and vertical upflow — are investigated under identical operating conditions of heat and mass fluxes. High-speed images are obtained to reveal the detailed two-phase flow structure and liquid-vapor interactions. The experimental data and high speed flow visualization indicate that compared to the horizontal case, the flow becomes less chaotic for vertical upflow, while the reversed flow becomes more pronounced in vertical downflow case. The resulting in increase in the back-flow is responsible for channel-to-channel flow maldistribution and heat transfer degradation. From the heat transfer data it is concluded that the performance of the tested channels under microgravity environment will be similar to the horizontal flow case.

External condensation heat transfer coefficients of R22 alternative refrigerants on enhanced tubes at three saturation temperatures

2008 ◽  
Vol 222 (6) ◽  
pp. 987-994 ◽  
Author(s):  
K-J Park ◽  
D Jung
Keyword(s):  
Heat Transfer ◽  
Saturation Temperature ◽  
Prediction Equation ◽  
Condensation Heat Transfer ◽  
Alternative Refrigerants ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Azeotropic Mixtures ◽  
Plain Tube ◽  
Fin Tube

In this study, external condensation heat transfer coefficients (HTCs) of R22, R410A, R407C, and R134a are measured on a 1024 fins per meter (26 fins per inch) low fin tube and Turbo-C tube at saturation temperatures of 30, 39, and 50 °C with wall subcooling of 3–8 °C. Test results show that condensation HTCs of all refrigerants decrease as the saturation temperature increases from 30 to 50 °C. This trend is due to the degradation of thermophysical properties of the liquid phase with an increase in saturation temperature. For the low fin tube data, Beatty and Katz's prediction equation showed a reasonably good agreement for all fluids with less than 20 per cent deviation. The performance of Turbo-C tube is better than that of the low fin tube for R22, R410A, and R134a due to the efficient removal of the condensate. For Turbo-C tube, HTCs of R407C were much lower than those of the other three fluids due to a unique condensation phenomenon associated with non-azeotropic mixtures at vapour—liquid interface. The average heat transfer enhancement ratios for the low fin tube and Turbo-C tube against the plain tube are 4.0–5.5 and 3.0–8.1, respectively, for all refrigerants tested.

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