Ideal tube bank pressure drop

APm.AP,., Pressure drop for ideal-tube-bank cross-flow and ideal window respectively AP for shell side of baffled exchanger kPa Itf ft ... 

Using Tinker s approach, BELL(12, i22) has described a semi-analytical method, based on work at the University of Delaware, which allows for the effects of major bypass and leakage streams, and which is suitable for use with calculators. In this procedure, the heat transfer coefficient and the pressure drop are obtained from correlations for flow over ideal tube banks, applying correction factors to allow for the effects of leakage, bypassing and flow... 

The complex flow pattern on the shell-side, and the great number of variables involved, make it difficult to predict the shell-side coefficient and pressure drop with complete assurance. In methods used for the design of exchangers prior to about 1960 no attempt was made to account for the leakage and bypass streams. Correlations were based on the total stream flow, and empirical methods were used to account for the performance of real exchangers compared with that for cross flow over ideal tube banks. Typical of these bulk-flow methods are those of Kern (1950) and Donohue (1955). Reliable predictions can only be achieved by comprehensive analysis of the contribution to heat transfer and pressure drop made by the individual streams shown in Figure 12.26. Tinker (1951, 1958) published the first detailed stream-analysis method for predicting shell-side heat-transfer coefficients and pressure drop, and the methods subsequently developed... 

In Bell s method the heat-transfer coefficient and pressure drop are estimated from correlations for flow over ideal tube-banks, and the effects of leakage, bypassing and flow in the window zone are allowed for by applying correction factors. 

The pressure drop in the cross-flow zones between the baffle tips is calculated from correlations for ideal tube banks, and corrected for leakage and bypassing. 

A Pi = the pressure drop calculated for an equivalent ideal tube bank,... 

Any suitable correlation for the cross-flow friction factor can be used for that given in Figure 12.36, the pressure drop across the ideal tube bank is given by ... 

AP, Pressure drop for cross-flow over ideal tube bank ML T ... 

Accurate predictions of the shell-side heat transfer coefficient and pressure drop are difficult because of the complex geometry and resulting flow patterns. A number of correlations are available, none of which is as accurate as those above for the tube side. All are based on crossflow past an ideal tube bank, either staggered (triangular pitch pattern) or inline (square pitch pattern). Corrections are made for flow distortion due to baffles, leakage, and bypassing. From 1950 to 1963, values of h , the shell-side, convective heat transfer coefficient, were most usually predicted by the correlations of Donohue (1949) and Kern (1950), which are suitable for hand calculations. Both of these correlations are of the general Nusselt number form... 

APj = ideal pressure drop across the tube bank jf = shell-side friction factor ... 

Generalized transfer and pressure-drop correlations for several commonly used ideal (no bypass or leakage flows) tube banks are shown in Figures 6.18, 6.19a, and 6.19b over the usual Reynolds number range. Figure 6.20 gives more specialized and accurate curves over a narrower but critical range. 

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