Water at a a flow rate of m = 0.215 kg/s is cooled from, 70 degrees Celsius to 30 degrees celsius by passing it through a thin-walled tube of a diameter D = 50 mm and maintaining a coolant at a (T infinitive = 15 degrees celsius) in a cross flow over the tube
(A). what is the required tube length if the coolant is air and its velocity is V = 20 m/s?
(B.) What is the tube length if the coolant is water and V = 2 m/s?