Heat transfer coefficient table

Table 2. Values of the Convective Heat-Transfer Coefficient ...

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. 

The convective heat-transfer coefficient and friction factor for laminar flow in noncircular ducts can be calculated from empirically or analytically determined Nusselt numbers, as given in Table 5. For turbulent flow, the circular duct data with the use of the hydrauhc diameter, defined in equation 10, may be used. 

TABLE 11-2 Overall Heat-Transfer Coefficients for Coils Immersed in Liquids... 

Typical overall heat-transfer coefficients are given in Tables 11-3 through 11-8. Values from these tables may be used for preliminaiy estimating purposes. They should not be used in place of the design methods described elsewhere in this section, although they may serve as a useful check on the results obtained by those design methods. 

TABLE 11-3 Typical Overall Heat-Transfer Coefficients in Tubular Heat Exchangers... 

In general, this equipment offers an economical heat-transfer area for first cost as well as operating cost. Capacity is hmited primarily by the air velocity which can be used without excessive dust entrainment. Table 12-32 shows hmiting air velocities suitable for various sohds particles. Usually, the equipment is satisfactory for particles larger than 100 mesh in size. [The use of indirect-heated conveyors eliminates the problem of dust entrainment, but capacity is limited by the heat-transfer coefficients obtainable on the deck (see Sec. 11)]. 

Examples for calculated heat transfer coefficients are shown in the table on Figure 1.5.1 The physical and other properties are used from the UCKRON-1 Example for methanol synthesis. These properties are ... 

As can be seen in the table above, the upper two results for heat transfer coefficients hp between particle and gas are about 10% apart. The lower three results for wall heat transfer coefficients, h in packed beds have a somewhat wider range among themselves. The two groups are not very different if errors internal to the groups are considered. Since the heat transfer area of the particles is many times larger than that at the wall, the critical temperature difference will be at the wall. The significance of this will be shown later in the discussion of thermal sensitivity and stability. 

Select an overall from Tables 5 and 6 in the Heat Transfer Coefficients section (based on finned area). Arbitrarily use /2"-flns, 9 to the inch for determining U,. 

A software package (MIXER) was developed to determine the heat transfer coefficient for any type of agitator and surface using the value in Table 7-16, fluid physical properties, agitator speed, and diameter. 

Solution One of the most critical and important quantities to calculate in Eq. (8.32) is the convective heat transfer coefficient. It depends on the temperature conditions and also on the width of the panel. Tables 8.11 and 8.12 collect the calculated heat transfer coefficients in different conditions. 

The calculation of overall heat transfer coefficient U using the equations jireviously presented can be rather tedious. Fleat transfer specialists have computer programs to calculate this value. There are some quick approximation techniques. Table 2-8 comes from the Gas Processors Suppliers Association s Engineering Data Book and gives an approximate value of U for shell and tube heat exchangers. 

A fire tube contains a flame burning inside a piece of pipe which is in turn surrounded by the process fluid. In this situation, there is radiant and convective heat transfer from the flame to the inside surface of the fire tube, conductive heat transfer through the wall thickness of the tube, and convective heat transfer from the outside surface of that tube to the oil being treated. It would be difficult in such a simation to solve for the heat transfer in terms of an overall heat transfer coefficient. Rather, what is most often done is to size the fire tube by using a heat flux rate. The heat flux rate represents the amount of heat that can be transferred from the fire tube to the process per unit area of outside surface of the fire tube. Common heat flux rates are given in Table 2-11. 

The procedure for calculating the number of tubes required for an aerial cooler is similar to that for a shell- and-tube exchanger. Table 3-6 shows approximate overall heat transfer coefficients. Ub should be used when the outside surface area of the bare tube (neglecting fins) is used in the heat... 

A few typical overall heat transfer coefficients, U, are presented in Table 5-9 [27] [29]. 

Table 10-40 provides a suggested range of overall heat transfer coefficients, Uq, for actual finned heat exchangers. 

Example 1.9 A formula for the heat transfer coefficient between forced draught air and a vertical plane surface ([1], Chapter 3, Table 6) gives ... 

Table 9.10. Heat transfer coefficients for boiling liquids...

Typical values of thermal resistances and individual and overall heat transfer coefficients are given in Tables 9.15-9.18. 

Table 9.17. Approximate overall heat transfer coefficients U for shell and tube equipment...

A high degree of turbulence is obtained even at low flowrates and the high heat transfer coefficients obtained are illustrated by the data in Table 9.23. These refer to the heating of cold water by the equal flow of hot water in an HF type exchanger (aluminium or copper), at an average temperature of 310 K. 

Table 6.8 shows that the effect of the Martinelli parameter is important for each of the three quality ranges. The present correlations show the heat transfer coefficient is... 

Table 6.8 Two-phase flow boiling in micro-channels. Heat transfer coefficient. Reprinted from Lee and Mudawar (2005b) with permission...

In this table the parameters are defined as follows Bo is the boiling number, d i is the hydraulic diameter, / is the friction factor, h is the local heat transfer coefficient, k is the thermal conductivity, Nu is the Nusselt number, Pr is the Prandtl number, q is the heat flux, v is the specific volume, X is the Martinelli parameter, Xvt is the Martinelli parameter for laminar liquid-turbulent vapor flow, Xw is the Martinelli parameter for laminar liquid-laminar vapor flow, Xq is thermodynamic equilibrium quality, z is the streamwise coordinate, fi is the viscosity, p is the density, <7 is the surface tension the subscripts are L for saturated fluid, LG for property difference between saturated vapor and saturated liquid, G for saturated vapor, sp for singlephase, and tp for two-phase. 

It is important to note that the compacityfactor is defined by the ratio of the surface area offered to heat transfer over the volume of the reactive medium. The thermal performances are estimated from the product between this compacity factor and the global heat-transfer coefficient. Consequently, owing to the large value of this factor combined with the conductivity performances of the SiC material, the heat-exchange performances are expected to be very high, which can be noticed from the last column of this table. 

Figure 12.8 Temperature profile along the reactor at steady state for different 1. Table 12.7 Overall heat transfer coefficient for all experiments (with reaction).

Table 3.3 Comparison of the calculated heat-transfer coefficients, heat-exchange areas and the estimated temperature gradients between the central reactor area and the outer wall of the reactor.

---