How to calculate the pressure drop at the U-bend of a U-tube heat exchanger
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How is the pressure drop across the U-bend in a U-tube heat exchanger calculated? Can it be calculated using the formula from the Heat Exchanger Design Manual (Qian Songwen), page P92: ΔPr=4NpGt^2/(2gρ)? The results obtained using this formula differ significantly from those obtained using the formula on page P76, which calculates ΔPr as the pressure drop caused by frictional resistance as the fluid flows through the bend. If we calculate based on the equivalent length, could we use 50 times the inner diameter of the tube as that equivalent length? The results obtained so far differ significantly; anyone who can help answer this question would be greatly appreciated
It is available in the chapter on heat transfer calculations for heat exchangers in the petrochemical design manual