A horizontal tube (inner and outside diameters are 2.0 cm and 2.5 cm respectively). is used as device for heat transfer. The said tube has a thermal conductivity of 386 W/m – K. The fluid flowing...

find the overall heat transfer coefficient (W/m2 – oC) if there is fouling on the inside and outside surfaces of the tube. The fouling factors for inner and outside surfaces are 0.005 (m2 – K)/W and 0.008 (m2 – K)/W respectively.

Extracted text: A horizontal tube (inner and outside diameters are 2.0 cm and 2.5 cm respectively). is used as device for heat transfer. The said tube has a thermal conductivity of 386 W/m – K. The fluid flowing (forced convection rate and fully developed flow at 1 kg/s) inside the tube is a liquid ethylene glycol with inlet and outlet temperatures of 20 °C and 40 °C respectively. A saturated vapor (T is 110 °C) condenses on the surface outside of the tube. Its heat transfer coefficient (kW/m² – K) is equivalent to 9.2/(Ts - Tw)0.25 where Tw is the average outside -tube wall temperature. The temperatures of the inside and outside surfaces of the wall are 80 °C and 100 °C respectively. Determine the length (m) of the tube. Use the properties of ethylene glycol: p =1109 kg/m³, Cp = 2428 J/kg – K, k = 0.253 W/m - °C, µ = 0.01545 kg/m-s.