Ethylene glycol is heated from 25°c to 40°c at a rate of 2.5 kg/s in a horizontal copper tube (k = 386 w/m·k) with an inner diameter of 2.0 cm and an outer diameter of 2.5 cm. a saturated vapor (tg = 110°c) condenses on the outside-tube surface with the heat transfer coefficient (in kw/m2 ·k) given by 9.2/(tg − tw) 0.25 , where tw is the average outside-tube wall temperature. what tube length must be used? take the properties of ethylene glycol to be rho = 1109 kg/m3 , cp = 2428 j/kg·k, k = 0.253 w/m·k, μ = 0.01545 kg/m·s, and pr = 148.5.