Fluid heat transfer data

Colburn, A.P. Trans. Am. Inst. Chem. Eng. 29 (1933) 174. A method of correlating forced convection heat transfer data and a comparison with fluid friction. 

The first of these two methods has the important advantage that measurements of the actual physical properties of the fluids are made and used to interpret the heat transfer data. It sometimes has the important practical disadvantage that such measurements on dilute suspensions are difficult to make in view of the settling tendency of the solid phase to leave nonuniform samples. This difficulty has perhaps been completely overcome in a device described by Orr and DallaValle (05). Their viscometer is shown in Fig. 13 and described in Section VI. 

Suppose a number of experiments are conducted with measurements taken of heat-transfer rates of various fluids in turbulent flow inside smooth tubes under different temperature conditions. Different-diameter tubes may be used to vary the range of the Reynolds number in addition to variations in the mass-flow rate. We wish to generalize the results of these experiments by arriving at one empirical equation which represents all the data. As described above, we may anticipate that the heat-transfer data will be dependent, on the Reynolds and Prandtl numbers. An exponential function for each of these parameters is perhaps the simplest type of relation to use, so we assume... 

The heat-transfer data which were used to arrive at Eqs. (6-21) and (6-22) include fluids of air, water, and liquid sodium. Still another correlation equation is given by Whitaker [35] as... 

Colburn, A. P. A Method of Correlating Forced Convection Heat Transfer Data and a Comparison with Fluid Friction, Trans. AIChE, vol. 29, p.174, 1933. 

Numerous measurements of heat transfer between the fluid bed and immersed surface have been carried out these have been reviewed by Kunii and Levenspiel (K24), Davidson and Harrison (D5), Botterill (B12), and Zabrodsky et al. (Zl, Z2). Wen and Leva (W3) and Wender and Cooper (W5) correlated heat-transfer data at the walls of fluidized beds. However, the data utilized for their correlation were obtained with a... 

Heat-transfer data for flow normal to cylinders of noncircular cross section are given in the literature. Banks of tubes across which the fluid flows are common in industrial exchangers. Problems of heat flow in tube banks are discussed in Chap. 15. 

Horizontal Fluid Layers. A uniform volumetric heat production q " in a horizontal layer bounded above by an isothermal surface and on the sides and bottom by adiabatic surfaces is depicted in Fig. 4.40. For a stationary fluid, the Nusselt number defined in the figure is Nu = 2, and the temperature difference used to construct the Rayleigh number is T0 - 7] = q" L l2k. As Ra increases from zero, the layer remains stable and heat flow is by conduction until a critical Rayleigh number of 1386 is reached [167]. Thereafter convection promotes a monotonic increase in Nu with Ra. For water (2.5 < Pr < 7), and for Ra < 10 2, the heat transfer data of Kulacki et al. [166-168] are accurately represented by... 

A rather large variety of tube inserts falls into the category of displaced enhancement devices. The heated surface is left essentially intact, and the fluid flow near the surface is altered by the insert, which might be metallic mesh, static mixer elements, rings, disks, or balls. Laminar heat transfer data for uniform-wall-temperature tubes and uniformly heated tubes are plotted in Figs. 11.26 and 11.27, respectively. The isothermal friction factors are plotted in Fig. 11.28. 

Answer by Author If we have the correct equations of continuity, energy, and motion for the system, then, with the proper initial and boundary conditions and the transport coefficients, the vapor fractions as well as wall and fluid temperatures should be predictable. As a first step towards this goal, we are studying boiling heat transfer and attempting to determine vapor fractions so that the heat transfer data obtained may be correlated. 

By assuming that heat transfer data in aerated Newtonian and non-Newtonian fluids follow the same dependencies Nishikawa, Kato, and Hashimoto (84) have proposed valueible correlations for the average shear rate as a function of the gas velocity. With the shear rate known, the effective viscosity of non-Newtonian media in the tower reactor can be obtained from the shear stress vs. shear rate curve. 

Transfer from the wall of a tube to a fluid in turbulent flow is the situation most commonly consideted for the development of the analogies. Sherwood, et al. critically compared vatioos analogies with both heat transfer data and mass transfer data at high Schmidt numbers (liquids) and low Schmidt nurribets ases) and concluded that the simple Chilton-Colbum analogy does ab as well as any of the conehuions in representing the results. 

No published heat-transfer data appear to be available for turbulent flow of polymer systems through other geometries. If such situations are encountered, it is recommended that Eq. (4-33) be used with four times the hydraulic radius substituted for the circular conduit diameter. Based on Newtonian fluid results, this should give at least reasonable estimates of the heat-transfer coefficient. 

A heat exchanger with iV transfer units allows a temperature change in a fluid equal to N times the average temperature difference. It should be noted that the number of transfer units based on the over-all temperature difference is always less than or at most equal to the number of transfer units based on the film difference. In correlating heat transfer data it is important to define clearly the type of transfer unit which is used. 

The dishes were 5, 7, and 10 cm in diameter (Thibodeaux et al., 1980). Using heat transfer data for a cold plate facing upward. Equation 2.34 in Table 2.3 can be applied to assess natural convection as well. In the above cases, the correlations relate chemical dissolution at the sediment-water interface, which forms a boundary layer with fluid density slightly greater than that of pure water. This particular mass transfer process is very slow since a high-density fluid accumulates on the bottom surface and forms a stable layer, which resist the generation of BL turbulence. The resulting estimated MTCs should be the lowest for the water-side bed sediment surfaces, and appropriate for waterbodies in the absence of bottom of currents. 

Convection Heat Transfer. Convective heat transfer occurs when heat is transferred from a soHd surface to a moving fluid owing to the temperature difference between the soHd and fluid. Convective heat transfer depends on several factors, such as temperature difference between soHd and fluid, fluid velocity, fluid thermal conductivity, turbulence level of the moving fluid, surface roughness of the soHd surface, etc. Owing to the complex nature of convective heat transfer, experimental tests are often needed to determine the convective heat-transfer performance of a given system. Such experimental data are often presented in the form of dimensionless correlations. 

---