ME6502 Heat and Mass Transfer, Third year, Department of Mechanical Engineering, first and second Units Questions.

ME6502 Heat and Mass Transfer

Third year, Department of Mechanical Engineering

First and second Units Questions.

Answer ALL Questions

PART A – (5 x 2 = 10 Marks)

1.what are the modes of heat transfer?

2.state fouriers law of conduction?

3.define thermal conductivity?

4.write down the three dimensional heat conduction equation in cartesiaon co-ordinate system?

5.write down the three dimensional heat conduction equation in cylindrical co-ordinate system?

6.list down the three types of boundary conditions?

7.state newtons law of colling or convection?

8.define overall heat transfer co-efficient?

9.write down the equation for heat transfer through a composite plane wall?

10.write down the equation for heat transfer through a composite pipes or cylinder?

PART – B( 5×16=80 Marks)

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    1.Derive general heat conduction equation in Cartesian co-ordinate?

    2.Derive heat transfer through a composite plane wall with inside and outside convection?

3.An external wall of a house is made up of 10cm common brick k=0.7w/mk followed by a 4cm layer of gypsum                         plaster k=0.48w/mk. what thickness of loosly packed insulation k=0.065w/mk should be added to reduce the heat loss through the wall by 80%.

4.The inner dimensions of a freezer cabinates are 60*60cm. the cabinates wall consists of two 2mm thick steel wall k=40w/mk separated by a 4cm layer of  fiber glass insulation k=0.049w/mk.the inside temperature is to be maintained at 15^0cthe outside on a hot summer day is 45º C.calculate the maximum amount of heat transfer, assuming  a heat transfer coewfficent of 10 w/mk.both  on side and outside  of the  cabinate also calculate the outer surface of the cabinate.

5.A steel tube K= 43.26W /MK OF 5.08 cm inner diameter and 7.62cm outer diameter is covered with 2.5cm layer of insulation K= 0.208W/ mk the inside surface of the tube receivers  heat from a hotgas at the temperature of 316ºC With Heat Transfer coefficient of 28W/m² k.while the out of surface exposed to the ambient air at 30⁰C with heat transfer co efficient of 17w/m²k. calculate heat loss for 3m length of the tube.