Heattransfer习题课.doc

Heat transfer There is a tube and shell heat exchanger,and its outside area is A=40m2 . The tube is (25(2.5mm made up of steel. saturation steam which pressure is 2atm(a) in shell side is used to heat 2.5(104kg/h oil from 40(C to 80(C, and the individual coefficient of steam condensation is 1.2(104w/(m2K).Oil flows in tube side in turbulent flow, and its mean specific capacity is 1 The amount of oil treated increases one time, m(=2m, calculate the outlet temperature of the oil？ If the outlet temperature of oil remains 80(C，whether heat exchanger is suitable？ 2 Measures to be taken if the heat exchanger is unsuitable ？ 3 Calculate A if another heat exchanger is added in series / parallel connection？What problems should be taken into consideration? 4 Whether the outlet temperature of oil remains 80(C if steam pressure is increased to 3atm？ 5 Flowrate of the oil is fixed, and the oil viscosity is twice that of before. Other physical properties are fixed. please calculate outlet temperature of the oil . 6 After prolonged usage，there is thermal resistance of scale deposited on the outside surface of tubes, and the thickness is 1mm, k=0.2w/(mK) ,please calculate the outlet temperature of oil . 7 The atmosphere temperature is 10(C，and the individual coefficient by convection from surface to air is calculated according to the equ. : The shell of the exchanger is 400 ( 8mm，and the temperature of the shell is 30(C after preservation. The thermal conductivity of the logging material is 0.058w/(mK) Calculate the thickness of the logging material, and the steam saved per month. 1．The amount of oil treated increases one time, m(=2m ，calculate the outlet temperature of oil？ If the outlet temperature of oil remains 80(C，whether heat exchanger is suitable？ To check whether heat exchanger is suitable to maintain outlet temperature，check A 1）U Thermal resistance mainly in tube side (2) whether heat exchanger is suitable？ m(=2m ， unsuitable