Assignment 1 Heat Transfer
Content
1
ASSIGNMENT 1
(SEPTEMBER 2015 – JAN 2016)
QUESTION 1
(CO1,PO1)
a)
A young engineer is asked to determine the rate of heat loss from a furnace wall per
unit area and the temperature at the interface. The wall is constructed from an inner
layer of 0.5 cm thick steel (k = 40 W/m·K) and an outer layer of 10 cm zirconium brick
(k = 2.5 W/K) as shown in figure 1. The inner surface temperature is 900 K and the
outside surface temperature is 460 K. State two (2) of your assumptions.
Figure 1 Furnace Wall
(10 marks)
b) Compare the heat loss from an insulated and an uninsulated copper pipe under the
following condition. The pipe ( k = 400 W/m·K) has an internal diameter of 10 cm and an
external diameter of 12 cm. Saturated steam flows inside the pipe at 110°C and the heat
transfer coefficient is estimated to be 10,000 W/m2·K. The pipe is located in a space at
30°C and the heat transfer coefficient on its outer surface is estimated to be 15 W/m 2·K.
The insulation available to reduce heat losses is 5 cm thick and its conductivity is
0.20 W/m·K.
Figure 2 Copper pipe
(10 marks)
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2
QUESTION 2
(CO1, PO1)
Ammonia gas at a pressure of 101.3 kN/m2 and a temperature of 350°C flows with a velocity
of 15 m/s over an isothermal flat plate of 0.75 m long. The thermophysical properties of
ammonia gas for the system are as shown in Table 1. The surface temperature of the flat
plate is to be maintained at 24°C.
a) Calculate the film temperature (in Kelvin) of the flat plate.
(3 marks)
b) Determine whether the ammonia gas flow is laminar, turbulent or transient.
(5 marks)
c) Calculate the cooling rate per unit width of the flat plate.
(12 marks)
END OF QUESTION PAPER
© Hak Cipta Universiti Teknologi MARA
CONFIDENTIAL
ASSIGNMENT 1
(SEPTEMBER 2015 – JAN 2016)
QUESTION 1
(CO1,PO1)
a)
A young engineer is asked to determine the rate of heat loss from a furnace wall per
unit area and the temperature at the interface. The wall is constructed from an inner
layer of 0.5 cm thick steel (k = 40 W/m·K) and an outer layer of 10 cm zirconium brick
(k = 2.5 W/K) as shown in figure 1. The inner surface temperature is 900 K and the
outside surface temperature is 460 K. State two (2) of your assumptions.
Figure 1 Furnace Wall
(10 marks)
b) Compare the heat loss from an insulated and an uninsulated copper pipe under the
following condition. The pipe ( k = 400 W/m·K) has an internal diameter of 10 cm and an
external diameter of 12 cm. Saturated steam flows inside the pipe at 110°C and the heat
transfer coefficient is estimated to be 10,000 W/m2·K. The pipe is located in a space at
30°C and the heat transfer coefficient on its outer surface is estimated to be 15 W/m 2·K.
The insulation available to reduce heat losses is 5 cm thick and its conductivity is
0.20 W/m·K.
Figure 2 Copper pipe
(10 marks)
© Hak Cipta Universiti Teknologi MARA
CONFIDENTIAL
2
QUESTION 2
(CO1, PO1)
Ammonia gas at a pressure of 101.3 kN/m2 and a temperature of 350°C flows with a velocity
of 15 m/s over an isothermal flat plate of 0.75 m long. The thermophysical properties of
ammonia gas for the system are as shown in Table 1. The surface temperature of the flat
plate is to be maintained at 24°C.
a) Calculate the film temperature (in Kelvin) of the flat plate.
(3 marks)
b) Determine whether the ammonia gas flow is laminar, turbulent or transient.
(5 marks)
c) Calculate the cooling rate per unit width of the flat plate.
(12 marks)
END OF QUESTION PAPER
© Hak Cipta Universiti Teknologi MARA
CONFIDENTIAL
