Heat transfer coefficient, for tubing

Dou, S., Herb, B., Tuzla, K., and Chen, J. C., Heat Transfer Coefficients for Tubes Submerged in Circulating Fluidized Bed, Experimental Heat Transfer, 4 343-353 (1991)... 

Ub Overall heat-transfer coefficient for tube bundle, kcal/(m )(h)(°C)... 

The heat transfer coefficient for tube flow will be proportional to the mass flow raised to the power 0.8. Hence if the flowsheet mass flow is W,o and the flowsheet heat transfer coefficient is Kn,-,o< the heat transfer coefficient at any other tube-side flow, W, will be given by ... 

Heat-transfer coefficients for tubes packed with alumina spheres. Air flow, 3000 Ib/ft -h (4.07 kg/m -s). 

Dou S, Herb B, Tuzla K, Chen JC. Heat transfer coefficients for tubes submerged in circulating fluidized bed. Experimental Heat Transfer 4 343-353, 1991. 

Fig. 3.4 Distribution of the values of the overall heat transfer coefficient for tubing vials of 7 ml according to Hottot et al. (2005) total pressure P—6Pa and shelf temperature T=- 5°C.

Correlations for Convective Heat Transfer. In the design or sizing of a heat exchanger, the heat-transfer coefficients on the inner and outer walls of the tube and the friction coefficient in the tube must be calculated. Summaries of the various correlations for convective heat-transfer coefficients for internal and external flows are given in Tables 3 and 4, respectively, in terms of the Nusselt number. In addition, the friction coefficient is given for the deterrnination of the pumping requirement. 

Heat-transfer coefficients for finned tubes of various types are given in a series of papers [Tran.s. Am. Soc. Mech. Eng., 67, 601 (1945)]. 

Vertical Tubes For the following cases Reynolds number < 2100 and is calculated by using F = Wp/ KD. The Nusselt equation for the heat-transfer coefficient for condensate films may be written in the following ways (using liquid physical properties and where L is the cooled lengm and At is — t,) ... 

FIG. 11-23 Heat-transfer coefficients for water in short-tube evaporators. °C = (°F — 32)/1.8 to convert British thermal units per hour-square foot-degrees Fahrenheit to joules per square meter-second-kelvins, multiply hy 5.6783. 

High Fins To calculate heat-transfer coefficients for cross-flow to a transversely finned surface, it is best to use a correlation based on experimental data for that surface. Such data are not often available, and a more general correlation must be used, making allowance for the possible error. Probably the best general correlation for bundles of finned tubes is given by Schmidt [Knltetechnik, 15, 98-102, 370-378 (1963)] ... 

One device uses four baffles in a baffle set. Only half of either the vertical or the horizontal tube lanes in a baffle have rods. The new design apparently provides a maximum shell-side heat-transfer coefficient for a given pressure drop. 

Typical film coefficients can be used to build rough overall heat transfer coefficients. This should suffice in most cases to establish that the design is within ballpark accuracy. Later, for final design, certain critical services will be checked in detail. Typical film resistances for shell and tube heat exchangers and overall heat transfer coefficients for air cooled heat exchangers are shown in Chapter 2, Heat Exchangers. 

In water-cooled tube-and-shell condensers with shell side condensation, overall heat transfer coefficients for essentially pure steam range from 200 to 800 Btu per hour per square foot per °F. 

Overall Heat Transfer Coefficients for Plain or Bare Tubes... 

Figure 10-48. Fiow inside tubes for gases and vapors. Heat transfer coefficient for vapors and gases in turbuient fiow. (Used by permission Ning Hsing Chen, Chemical Engineering, V. 66, No. 1, 1959. McGraw-Hiii, inc. Aii rights reserved.)...

Figure 10-50A. Tube-side film heat transfer coefficient for water. (Used by permission Kern, D. Q., Process Heat Transfer, 1= Ed., 1950. McGraw-Hill, Inc. All rights reserved. Original adapted from Eagle and Ferguson, Proc. Royal Society A 127, 450, 1930.)...

Figure 10-50C. Tube-side (inside tubes) liquid film heat transfer coefficient for Dowtherm . A fluid inside pipes/tubes, turbulent flow only. Note h= average film coefficient, Btu/hr-ft -°F d = inside tube diameter, in. G = mass velocity, Ib/sec/ft v = fluid velocity, ft/sec k = thermal conductivity, Btu/hr (ft )(°F/ft) n, = viscosity, lb/(hr)(ft) Cp = specific heat, Btu/(lb)(°F). (Used by permission Engineering Manual for Dowtherm Heat Transfer Fluids, 1991. The Dow Chemical Co.)...

Figure 10-50D. Tube-side (inside pipes or tubes) liquid film heat transfer coefficient for Dowtherm A and E at various temperatures. (Used by permission Engineering Manual for Heat Transfer Fluids, 1991. The Dow Chemical Co.)...

The outer and inner tubes extend from separate stationary tube sheets. The process fluid is heated or cooled by heat transfer to/from the outer tube s outside surface. The overall heat transfer coefficient for the O.D. of the inner tube is found in the same manner as for the double-pipe exchanger. The equivalent diameter of the annulus uses the perimeter of the O.D. of the inner tube and the I.D. of the inner tube. Kem presents calculation details. 

Assume that the film heat transfer coefficient for the liquid in the tubes is proportional to the 0.8 power of the. velocity, the transfer coefficient for the condensing steam remains constant at 3.4 kW/m- K and that the resistance of the tube wall and scale can be neglected. 

On the other hand Bao et al. (2000) reported that the measured heat transfer coefficients for the air-water system are always higher than would be expected for the corresponding single-phase liquid flow, so that the addition of air can be considered to have an enhancing effect. This paper reports an experimental study of non-boiling air-water flows in a narrow horizontal tube (diameter 1.95 mm). Results are presented for pressure drop characteristics and for local heat transfer coefficients over a wide range of gas superficial velocity (0.1-50m/s), liquid superficial velocity (0.08-0.5 m/s) and wall heat flux (3-58 kW/m ). 

Will the distribution of flow on the shell side be uniform enough to give the same heat transfer coefficient for aU the tubes ... 

Estimate the heat-transfer coefficient for steam condensing on the outside, and on the inside, of a 25 mm o.d., 21 mm i.d. vertical tube 3.66 m long. The steam condensate rate... 

The equation given by Bromley (1950) can be used to estimate the heat-transfer coefficient for film boiling on tubes. Heat transfer in the film-boiling region will be controlled by conduction through the film of vapour, and Bromley s equation is similar to the Nusselt equation for condensation, where conduction is occurring through the film of condensate. 

Chen s method was developed from experimental data on forced convective boiling in vertical tubes. It can be applied, with caution, to forced convective boiling in horizontal tubes, and annular conduits (concentric pipes). Butterworth (1977) suggests that, in the absence of more reliable methods, it may be used to estimate the heat-transfer coefficient for forced convective boiling in cross-flow over tube bundles using a suitable cross-flow correlation to predict the forced-convection coefficient. Shah s method was based on data for flow in horizontal and vertical tubes and annuli. 

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