# Method for computing the pressure drop across a bank of tubes

I would like to determine the pressure drop of fluid in cross flow over a bank of tubes. (see figure 1).

Previously, I've used the correlation listed in "Fundamentals of Heat and Mass Transfer" by Incopera and DeWitt. However, this correlation requires looking up coefficients on a graph (see figure 2 - f is used to mean Eu/k by Incopera).

Now, I'd like calculate a pressure drops across a large number of tube banks in a computer program I'm running, so I need a correlation that's either just one equation or based on a lookup table. I tried using tables 1 and 2 from the Thermopedia article on tube banks in crossflow. While this gives reasonable answers at some points, it also produces clearly incorrect answers at others. For example, for a square in-line bank, this correlation shows that Euler's number for b=2.0 exceeds Euler's number for b=1.5 as Re approaches 1e6, which doesn't line up with the graphs and also is obviously an incorrect answer (See figure 3, b=1.5 is in orange and b=2.0 is in green).

Is there a correlation which I could use in my program which is more accurate than the one on Thermopedia?

• So make a data table of x & y values then use vlookup() or interpolation to get the value of y for a given x based on the curve you want. Did this for many characteristics when i first got into excel. There is a program called DataThief which will take an image of a graph and give you x & y values... Commented Mar 10, 2022 at 16:48
• Thank you for recommending DataThief - I think that is the right solution! Commented Mar 10, 2022 at 18:03
• My favourite plot digitizer is the online WebPlotDigitizer. Commented Jul 27, 2022 at 20:32