Consider a cross flow engine oil heater that uses ethylene glycol flowing at a temperature of 1108C to heat the oil initially at 108C. The ethylene glycol enters a tube bank consisting of copper tubes (k 5 250 W/m·K) with staggered arrangement in a 0.5 m 3 0.5 m plenum. The outside diameter
Consider a cross flow engine oil heater that uses ethylene glycol flowing at a temperature of 1108C to heat the oil
initially at 108C. The ethylene glycol enters a tube bank consisting of copper tubes (k 5 250 W/m·K) with staggered arrangement in a 0.5 m 3 0.5 m plenum. The outside diameter
of the 0.5-m-long copper tubes is 25 mm and has a wall thickness of 2 mm. The longitudinal and transverse pitch of the rod
bundles is 0.035 m each. The engine oil to be heated flows
inside the tubes with a mass flow rate of 4.05 kg/s. Take the
heat transfer coefficient of the oil to be 2500 W/m2
·K. If the
minimum desired exit temperature of oil is 708C and the measured exit temperature of ethylene glycol is 908C, determine
(a) mass flow rate of ethylene glycol and (b) number of tube
rows. In your calculation use the following properties for the
ethylene glycol.
r 5 1062 kg/m3 m 5 2.499 3 1023 kg/m·s
k 5 0.262 W/m·K cp 5 2742 J/kg·K
Pr 5 26.12 Prs@408
C 5 96.97
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