Flow and Heat Transfer Characteristics of an Impinging Jet in Crossflow at Low Nozzle-to-Plate Spacings

2005 ◽  
Author(s):  
Brian C. Y. Cheong ◽  
Peter T. Ireland ◽  
John P. C. W. Ling ◽  
Shirley Ashforth-Frost
Keyword(s):  
Heat Transfer ◽  
Target Surface ◽  
Impinging Jet ◽  
Surface Heat ◽  
Transfer Coefficients ◽  
Surface Heat Transfer ◽  
Heat Transfer Coefficients ◽  
Jet In Crossflow ◽  
Cold Wire ◽  
Near Wall

The research reported in this paper has measured in detail the near wall hydrodynamic and thermal characteristics of a confined single impinging jet in crossflow. To the authors’ knowledge, the work is unique in that the flow and thermal fields have been linked to the local surface heat transfer coefficients, which were measured at high resolution. The near wall velocity, turbulence, temperature and temperature fluctuation distributions of the jet were measured using hotwire anemometry and cold-wire thermometry. The target surface heat transfer coefficients were determined using the transient liquid crystal method. The multiple colour play coating enabled both the heat transfer coefficient and the adiabatic wall temperature distributions to be measured. The turbulent jet discharged with uniform exit velocity and temperature profiles at a Reynolds numbers of 20 000 and 40 000. The jet was subject to a crossflow at jet-to-crossflow velocity ratios of 1, 2, 3, 4 and 5. Two nozzle-to-plate spacings of 1.5d and 3d were examined. The results show that impinging jets in crossflow at z/d = 1.5 are significantly more intact at the target surface than jets with z/d = 3. As a result, the surface heat transfer rates beneath a jet in crossflow at the closer spacing are consistently higher. The results would provide excellent test cases for CFD works of similar flow configurations. The results are compared to related data in the literature. In addition, the driving gas temperature measured with the liquid crystals is compared to the near wall thermal field measured with the cold-wire.

Effect of Uneven Wall Temperature on Local Heat Transfer in a Rotating Square Channel With Smooth Walls and Radial Outward Flow

1992 ◽  
Vol 114 (4) ◽  
pp. 850-858 ◽  
Author(s):  
J.-C. Han ◽  
Y. M. Zhang
Keyword(s):  
Heat Transfer ◽  
Wall Temperature ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Surface Heat ◽  
Transfer Coefficients ◽  
Surface Heat Transfer ◽  
Square Channel ◽  
Heat Transfer Coefficients ◽  
Rotation Numbers

The influence of uneven wall temperature on the local heat transfer coefficient in a rotating square channel with smooth walls and radial outward flow was investigated for Reynolds numbers from 2500 to 25,000 and rotation numbers from 0 to 0.352. The square channel, composed of six isolated copper sections, has a length-to-hydraulic diameter ratio of 12. The mean rotating radius to the channel hydraulic diameter ratio is kept at a constant value of 30. Three cases of thermal boundary conditions were studied: (A) four walls uniform temperature, (B) four walls uniform heat flux, and (C) leading and trailing walls hot and two side walls cold. The results show that the heat transfer coefficients on the leading surface are much lower than that of the trailing surface due to rotation. For case A of four walls uniform temperature, the leading surface heat transfer coefficient decreases and then increases with increasing rotation numbers, and the trailing surface heat transfer coefficient increases monotonically with rotation numbers. The decreased (or increased) heat transfer coefficients on the leading (or trailing) surface are due to the cross-stream and centrifugal buoyancy-induced flows from rotations. However, the trailing surface heat transfer coefficients, as well as those for the side walls, for case B are higher than for case A and the leading surface heat transfer coefficients for cases B and C are significantly higher than for case A. The results suggest that the local uneven wall temperature creates the local buoyancy forces, which change the effect of the rotation. Therefore, the local heat transfer coefficients on the leading, trailing, and side surfaces are altered by the uneven wall temperature.

Influence of Inlet Mass Flow Rate on Heat Transfer of Supercritical Liquefied Natural Gas in Horizontal Tubes

2014 ◽  
Vol 960-961 ◽  
pp. 433-437 ◽  
Author(s):  
Hai Yu Meng ◽  
Shu Zhong Wang ◽  
Lu Zhou ◽  
Zhi Qiang Wu ◽  
Jun Zhao ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Surface Heat ◽  
Bulk Temperature ◽  
Transfer Coefficients ◽  
Surface Heat Transfer ◽  
Heat Transfer Coefficients ◽  
Horizontal Tubes

The submerged combustion vaporizer (SCV) is a new kind of vaporizer for liquefied natural gas (LNG). In this paper, a numerical study has been carried out to investigate the heat transfer characteristics of supercritical LNG in horizontal tubes. The thermo-physical properties of supercritical LNG were used for this study, and the influence of inlet LNG mass flow rate on heat transfer was investigated. Numerical results showed that the LNG flow in horizontal tubes included two stages. In the first stage, the surface heat transfer coefficients increased significantly with the increase of the fluid bulk temperature and reached a maximum value when the fluid bulk temperature equaled the pseudo-critical point . After the maximum, the surface heat transfer coefficients fell rapidly with the increase of the fluid bulk temperature. With increasing the inlet LNG mass flow rate, the surface heat transfer coefficients increased due to the increased fluid velocity in horizontal tubes.

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