Symposium on Heat Transmission: Heat-Transfer Coefficients in Vertical-Tube Forced-Circulation Evaporators

1936 ◽  
Vol 28 (5) ◽  
pp. 534-537 ◽  
Author(s):  
Nathan Fragen
Keyword(s):  
Heat Transfer ◽  
Vertical Tube ◽  
Heat Transmission ◽  
Transfer Coefficients ◽  
Forced Circulation ◽  
Heat Transfer Coefficients

scholarly journals Measurement of Heat Transfer Coefficients in an Agitated Vessel with Tube Baffles

10.14311/1171 ◽  
2010 ◽  
Vol 50 (2) ◽  
Author(s):  
M. Dostál ◽  
K. Petera ◽  
F. Rieger
Keyword(s):  
Heat Transfer ◽  
Cold Water ◽  
Vertical Tube ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Steady State Method ◽  
Classic Approach ◽  
Large Heat ◽  
Common Operation ◽  
The Heat Transfer Coefficient

Cooling or heating an agitated liquid is a very common operation in many industrial processes. A classic approach is to transfer the necessary heat through the vessel jacket. Another option, frequently used in the chemical and biochemical industries is to use the heat transfer area of vertical tube baffles. In large equipment, e.g. fermentor, the jacket surface is often not sufficient for large heat transfer requirements and tube baffles can help in such cases. It is then important to know the values of the heat transfer coefficients between the baffles and the agitated liquid. This paper presents the results of heat transfer measurements using the transient method when the agitated liquid is periodically heated and cooled by hot and cold water running through tube baffles. Solving the unsteady enthalpy balance, it is possible to determine the heat transfer coefficient. Our results are summarized by the Nusselt number correlations, which describe the dependency on the Reynolds number, and they are compared with other measurements obtained by a steady-state method.

Heat Transfer in Rotating Serpentine Passages With Smooth Walls

1991 ◽  
Vol 113 (3) ◽  
pp. 321-330 ◽  
Author(s):  
J. H. Wagner ◽  
B. V. Johnson ◽  
F. C. Kopper
Keyword(s):  
Heat Transfer ◽  
Turbine Blade ◽  
Large Scale ◽  
Flow Direction ◽  
Vertical Tube ◽  
Operating Conditions ◽  
Transfer Model ◽  
Transfer Coefficients ◽  
Flow Equations ◽  
Heat Transfer Coefficients

Experiments were conducted to determine the effects of buoyancy and Coriolis forces on heat transfer in turbine blade internal coolant passages. The experiments were conducted with a large-scale, multipass, smooth-wall heat transfer model with both radially inward and outward flow. An analysis of the governing flow equations showed that four parameters influence the heat transfer in rotating passages: coolant-to-wall temperature ratio, Rossby number, Reynolds number, and radius-to-passage hydraulic diameter ratio. These four parameters were varied over ranges that are typical of advanced gas turbine engine operating conditions. It was found that both Coriolis and buoyancy effects must be considered in turbine blade cooling designs and that the effect of rotation on the heat transfer coefficients was markedly different depending on the flow direction. Local heat transfer coefficients were found to decrease by as much as 60 percent and increase by 250 percent from no-rotation levels. Comparisons with a pioneering stationary vertical tube buoyancy experiment showed reasonably good agreement. Correlation of the data is achieved employing dimensionless parameters derived from the governing flow equations.

Analysis of Stagnant Non Condensable Gases Effects on Condensation Heat Transfer in a Vertical Tube

2011 ◽  
Vol 148-149 ◽  
pp. 491-495
Author(s):  
Jun Xia Zhang ◽  
Zeng Sheng Li ◽  
Bin Yao Gong ◽  
Hong Xing Zhao ◽  
Yu Huai Zhao
Keyword(s):  
Heat Transfer ◽  
Mass Fraction ◽  
Volume Fraction ◽  
Vertical Tube ◽  
Condensation Heat Transfer ◽  
Condenser Tube ◽  
Condensation Rate ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Velocity Pressure

In a vertical condenser tube installed at the cold end of a non-vacuum separate type heat pipe, non condensable (NC) gases in the system is pushed by continuous vapor flowing from the hot end into the condenser tube at the cold end, gathering above condensate at the outlet of the condenser tube. Therefore, condensation heat transfer of vapor with the stagnant NC gases occurs in the condenser tube. It is necessary to comprehend the effects of stagnant NC gases on condensation heat transfer. A VOF method was adopted to analyze how stagnant NC gases affect condensation heat transfer, a mass fraction equation of NC gases was used to solve diffusion between NC gases and vapor, a Hertz-Knudsen-Schrage model was applied to deal with condensation rate of vapor on the surface of liquid film. Parameters, including volume fraction, velocity, pressure, mass fraction of NC gases and condensation heat transfer coefficients (HTC), were obtained. Results show that a lot of NC gases deposits in the condenser tube rear, leading a lot of vapor to condense at the condenser tube front. NC gases slightly affect condensation HTC of the tube front, and severely degrade condensation HTC of the tube rear. Furthermore, an increase in mass of NC gases causes a rise in pressure and velocity, improving condensation heat transfer.

Condensation of Steam on a Rotating Vertical Cylinder

1970 ◽  
Vol 92 (1) ◽  
pp. 144-151 ◽  
Author(s):  
A. A. Nicol ◽  
M. Gacesa
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Rotational Speed ◽  
Weber Number ◽  
Vertical Cylinder ◽  
Vertical Tube ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Condensing Heat Transfer ◽  
Correlating Equation

Heat transfer coefficients have been determined for steam condensing on a 1-in-dia vertical tube, rotating on its axis. The condensing heat transfer coefficients increased with speed of rotation and for the maximum rotational speed of 2700 rpm investigated were found to be four or five times the stationary value. When the results were plotted in terms of the pertinent parameters of Nusselt number and Weber number, the Nusselt number was found to be constant for Weber numbers below 500, and above this the correlating equation was NNUA, = 6.13 NWC0.496.

scholarly journals Heat Transfer in Rotating Serpentine Passages With Smooth Walls

1990 ◽  
Author(s):  
J. H. Wagner ◽  
B. V. Johnson ◽  
F. C. Kopper
Keyword(s):  
Heat Transfer ◽  
Turbine Blade ◽  
Large Scale ◽  
Flow Direction ◽  
Vertical Tube ◽  
Operating Conditions ◽  
Transfer Model ◽  
Transfer Coefficients ◽  
Flow Equations ◽  
Heat Transfer Coefficients

Experiments were conducted to determine the effects of buoyancy and Coriolis forces on heat transfer in turbine blade internal coolant passages. The experiments were conducted with a large scale, multi–pass, smooth–wall heat transfer model with both radially inward and outward flow. An analysis of the governing flow equations showed that four parameters influence the heat transfer in rotating passages (coolant–to–wall temperature ratio, Rossby number, Reynolds number and radius–to–passage hydraulic diameter ratio). These four parameters were varied over ranges which are typical of advanced gas turbine engine operating conditions. It was found that both Coriolis and buoyancy effects must be considered in turbine blade cooling designs and that the effect of rotation on the heat transfer coefficients was markedly different depending on the flow direction. Local heat transfer coefficients were found to decrease by as much as 60 percent and increase by 250 percent from no rotation levels. Comparisons with a pioneering stationary vertical tube buoyancy experiment showed reasonably good agreement. Correlation of the data is achieved employing dimensionless parameters derived from the governing flow equations.

Effects of a Flow Disturbing Plate on Pool Boiling Heat Transfer on a Vertical Tube

2003 ◽  
Author(s):  
Myeong-Gie Kang
Keyword(s):  
Heat Transfer ◽  
Atmospheric Pressure ◽  
Boiling Heat Transfer ◽  
Pool Boiling ◽  
Vertical Tube ◽  
Tube Surface ◽  
Transfer Coefficients ◽  
Pool Boiling Heat Transfer ◽  
Heat Transfer Coefficients ◽  
Plate Width

Effects of the width and location of a flow disturbing circular plate, installed at a vertical tube surface, on nucleate pool boiling heat transfer of water at atmospheric pressure have been investigated experimentally. Through the tests, changes in the degree of intensity of liquid agitation have been analyzed. The plate changes the fluid flow around the tube as well as heat transfer coefficients on the tube surface. It is identified that the plate width changes the rate of the circulating flow whereas its location changes the growth of the active agitating flow. Moreover, the flow chugging was observed at the downside of the plate.

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