Tube flow turbulent heat transfer

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.)...

The mean heat-transfer coefficient will depend on the number of tubes crossed. Figure 12.31 is based on data for ten rows of tubes. For turbulent flow the correction factor Fn is close to 1.0. In laminar flow the heat-transfer coefficient may decrease with increasing rows of tubes crossed, due to the build up of the temperature boundary layer. The factors given below can be used for the various flow regimes the factors for turbulent flow are based on those given by Bell (1963). 

Horizontal In-Shell Condensers The mean condensing coefficient for the outside of a bank of horizontal tubes is calculated from Eq. (5-93) for a single tube, corrected for the number of tubes in a vertical row. For undisturbed laminar flow over all the tubes, Eq. (5-97) is, for realistic condenser sizes, overly conservative because of rippling, splashing, and turbulent flow (Process Heat Transfer, McGraw-Hill, New York, 1950). Kern proposed an exponent of -Ve on the basis of experience, while Freon-11 data of Short and Brown General Discussion on Heat Transfer, Institute of Mechanical Engineers, London, 1951) indicate independence of the number of tube rows. It seems reasonable to use no correction for inviscid liquids and Kern s correction for viscous condensates. For a cylindrical tube bundle, where N varies, it is customary to take N equal to two-thirds of the maximum or centerline value. 

R. G. Deissler, and M. F. Taylor, Analysis of Axial Turbulent Flow and Heat Transfer through Banks of Rods or Tubes, Reactor Heat Transfer Conf, New York, TID 75299, part 1, pp. 416-461, 1956. 

R. M. Manglik, and A. E. Bergles, Heat Transfer and Pressure Drop Correlations for Twisted-Tape Inserts in Isothermal Tubes Part II—Transition and Turbulent Flows, J. Heat Transfer, (115) 890-896,1993. 

Arrays of Cylinders. The heat transfer behavior of a tube in a bank differs considerably from that of a single tube immersed in a flow of infinite extent. The presence of adjacent tubes in an array and the turbulence and unsteadiness generated by upstream tubes generally tend to increase the overall heat transfer from a particular tube. After the flow has passed through several rows of tubes, however, the heat transfer from individual tubes becomes independent of their location and just a function of the Reynolds number with a parametric dependence on the array geometry. Average and local heat transfer data for tube banks have been summarized by Zukauskas [67],... 

Metzner and Friend [73] measured turbulent heat transfer rates with aqueous solutions of Carbopol, corn syrup, and slurries of Attagel in circular-tube flow. They developed a semi-theoretical correlation to predict the Stanton number for purely viscous fluids as a function of the friction factor and Prandtl number, applying Reichardt s general formulation for the analogy between heat and momentum transfer in turbulent flow ... 

Values of the asymptotic heat transfer factors jH in the thermal entrance region are reported for concentrated aqueous solutions of polyacrylamide and polyethylene oxide. The results are shown in Fig. 10.30, as a function of the Reynolds number Re . These values were measured in tubes of 0.98,1.30, and 2.25 cm (0.386,0.512, and 0.886 in) inside diameter in a recirculating-flow loop. The asymptotic turbulent heat transfer data in the thermal entrance region are seen to be a function of the Reynolds number Re and of the axial position xld. The following empirical correlation is derived from the data [35,37] ... 

S. V. Patankar, M. Ivanovic, and E. M. Sparrow, Analysis of Turbulent Flow and Heat Transfer in Internally Finned Tube and Annuli, J. Heat Transfer (101) 29-37,1979. 

EXAMPLE 4S-1. Heating of Air in Turbulent Flow Air at 206.8 kPa and an average of 477.6 K is being heated as it flows through a tube of 25.4 mm inside cfiameter at a velocity of 7.62 m/s. The heating medium is 488.7 K steam condensing on the outside of the tube. Since the heat-transfer coefficient of condensing steam is several thousand W/m K and the resistance of the metal wall is very small, it will be assumed that the surface wall temperature of the metal in contact with the air is 488.7 K. Calculate the heat-transfer coefficient for an L/D > 60 and also the heat-transfer flux q/A. 

The heat-transfer phenomena for forced convection over exterior surfaces are closely related to the nature of the flow. The heat transfer in flow over tube bundles depends largely on the flow pattern and the degree of turbulence, which in turn are functions of the velocity of the fluid and the size and arrangement of the tubes. The equations available for the calculation of heat transfer coefficients in flow over tube banks are based entirely on experimental data because the flow Is too complex to be treated analytically. Experiments have shown that, in flow over staggered tube banks, the transition from laminar to turbulent flow Is more gradual than in flow through a pipe, whereas for in-line tube bundles the transition phenomena resemble those observed in pipe flow. In either case the transition from laminar to turbulent flow begins at a Reynolds number based on the velocity in the minimum flow area of about 100, and the flow becomes fully turbulent at a Reynolds number of about 3,000. The equation below can be used to predict heat transfer for flow across ideal tube banks. 

The third example shown in Fig. 22.7 is my favorite for sensible-heat transfer in fouling service. This consists of 1-in tubes set on 1.5-in rotated square pitch. The pitch layout is the same as that of the square pitch. It is just the tube bundle that is rotated by 45° relative to the shell-side flow. The shell-side fluid cannot flow without interference between the tubes. Hence, the tubes promote turbulence, and improve heat transfer. The large tubes, and especially the doubling of the space between the tubes, reduce the heat-transfer surface area that can fit into a shell of a given ID. But the primary objective of the 1-in tubes on a 1.5-in rotated square pitch is that it is relatively easy to hydroblast. 

An advanced computer code CONVERT, developed and validated earlier at the University of Manchester for buoyancy-influenced flow in uniformly heated vertical tubes, was used to perform simulations of the present experiments. This code uses a buoyancy influenced, variable property, developing wall shear flow formulation for turbulent flow and heat transfer in a vertical tube in conjunction with the Launder-Sharma low Reynolds number k-8 turbulence model [9], The conditions covered in the simulations ranged from forced flow with negligible influence of buoyancy to buoyancy-dominated mixed convection. In each case, simulations were made for thermal boundary conditions of both uniform wall temperature and uniform heat flux. These show that the computational formulation used does enable observed heat transfer behaviour in the mixed convection region to be reproduced. Buoyancy-induced impairment of... 

JACKSON, J.D. and LI, J., Buoyancy-influenced variable property turbulent heat transfer to air flowing in a uniformly heated vertical tube , (Proc. 2 EF International Conference on Turbulent Heat Transfer, Manchester), Vol. 1, 2.31-2.49, June (1998). 

In the forced convection heat transfer, the heat-transfer coefficient, mainly depends on the fluid velocity because the contribution from natural convection is negligibly small. The dependence of the heat-transfer coefficient, on fluid velocity, which has been observed empirically (1—3), for laminar flow inside tubes, is h for turbulent flow inside tubes, h and for flow outside tubes, h. Flow may be classified as laminar or... 

The minimum velocity requited to maintain fully developed turbulent flow, assumed to occur at Reynolds number (R ) of 8000, is inside a 16-mm inner diameter tube. The physical property contribution to the heat-transfer coefficient inside and outside the tubes are based on the following correlations (39) ... 

Flow in tubular reactors can be laminar, as with viscous fluids in small-diameter tubes, and greatly deviate from ideal plug-flow behavior, or turbulent, as with gases, and consequently closer to the ideal (Fig. 2). Turbulent flow generally is preferred to laminar flow, because mixing and heat transfer... 

Circular Tubes Numerous relationships have been proposed for predicting turbulent flow in tubes. For high-Prandtl-number fluids, relationships derived from the equations of motion and energy through the momentum-heat-transfer analogy are more complicated and no more accurate than many of the empirical relationships that have been developed. 

The value of tire heat transfer coefficient of die gas is dependent on die rate of flow of the gas, and on whether the gas is in streamline or turbulent flow. This factor depends on the flow rate of tire gas and on physical properties of the gas, namely the density and viscosity. In the application of models of chemical reactors in which gas-solid reactions are caiTied out, it is useful to define a dimensionless number criterion which can be used to determine the state of flow of the gas no matter what the physical dimensions of the reactor and its solid content. Such a criterion which is used is the Reynolds number of the gas. For example, the characteristic length in tire definition of this number when a gas is flowing along a mbe is the diameter of the tube. The value of the Reynolds number when the gas is in streamline, or linear flow, is less than about 2000, and above this number the gas is in mrbulent flow. For the flow... 

Narezhnyy, E. G., and Sudarev, A. V. (1971). Local heat transfer in air flowing in tubes with a turbulence promoter at the inlet. Heat Transfer 3, 62-66. 

Figures 10-101, lO-lOJ, and 10-1 OK indicate the process flow patterns for single tube units and for multiple corrugated tubes in a single plain shell. These units are suitable for heating or cooling process fluids containing high pulp or fiber content or suspended particulates. The heat transfer coefficients are improved when compared to plain tubes as the turbulence improves the performance. The units can be arranged in multiple shells for parallel or series flow. The manufacturers should be contacted for details.

Withers, J. G., Tube-Side Heat Transfer and Pressure Drop for Tubes Having Helical Internal Ridging and Turbulent/Tran-sitional Flow of Single-Phase Fluid Part 1 and Part 2 Single Helix Ridging, Heat Trans. Eng, V. 2, Jufy-Sept., Oct.-Dec. (1980) p. 49. 

Operated in this manner, the shell-and-tube type is a flooded evaporator (see Figure 7.3) and has oil drainage pots if using ammonia, or a mixture bleed system if the refrigerant is one of the halocarbons. The speed of the liquid within the tubes should be about 1 m/ s or more, to promote internal turbulence for good heat transfer. End cover baffles will constrain the flow to a number of passes, as with the shell-and-tube condenser. (See Section 6.4.)... 

H7. Hines, W. S., Forced convection and peak nucleate boiling heat transfer characteristics for hydrazine flowing turbulently in a round tube at pressures to 1000 psia, Rept. No. 2059, Rocketdyne, Canoga Park, California (1959). 

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