A shell-and-tube heat exchanger has tubes with 19mm outside diameter and 1.2mm tube wall thickness. Water velocity in the tubes is 1.8m/s. Determine an increase in the tube-side pressure drop per unit...

A shell-and-tube heat exchanger has tubes with 19mm outside diameter and 1.2mm tube wall thickness. Water velocity in the tubes is 1.8m/s. Determine an increase in the tube-side pressure drop per unit length due to fouling when the value of fouling resistance reaches 5.3 x m2 K/W. Assume that the flow rate remains constant even when the tube is fouled. Use the following correlations for the Fanning friction factor for smooth (clean) and rough (fouled) tubes: (1) f = 0.0014 + 0.125Re-⁰•³² for a smooth tube, and (2)f = 0.0035 + 0.264Re-⁰•⁴² for a rough tube. The density and dynamic viscosity of water are 998 kg/m³ and 1.12 x Pa . s, respectively. The thermal conductivity of the fouling deposit is 1.73 W/m . K.