You are required to design a heating oven for sterilizing equipment. The oven is heated by side
heater imbedded at the mid-plan of a wall of 20 cm thick. The wall is completely insulated from
the air side. The material of the oven walls has k = 10 W/m K and the thickness of each wall
other than that mentioned is 10 cm. The top and the bottom sides of the oven are completely
insulated. The amount of heat lost from the walls should not exceed 5% of the input power to the
heater which is 2kW. In order to enhance the heat transfer from the wall where the heater is fitted
to the oven space, it is proposed to attach a number of either longitudinal or transverse fins to
this wall. The dimensions of each one of these fins as follows; its length is 15 cm and thickness
is 3mm. The fin material is aluminum with k = 150 W/m K.
The oven is cubical in shape with side length 75 cm. If the inside temperature of air inside the
oven should be 75°C and the ambient temperature of the air outside the oven varies from 25°C to
40 °C. All the heat generated by the heater is transferred normal to its wall. Assume an average
fin temperature to calculate the heat transfer coefficient from fins to the oven space. After then
use this value of h to calculate the heat transfer from single fin and then find the number of fins
required to transfer the heat, assuming adiabatic tip fin, bearing in mind that heat is also
transferred from bare area of the wall where the fins are attached.
Explain which type of fins you recommend (longitudinal or transverse fins). (Comment of your
results)
It is required also to select suitable insulating material used for this application and to calculate the
thickness of this material to suit the given condition of heat loss.
Assume the gas in the oven to be a lumped capacitance system, calculate in this case the time required
for the air in the oven to reach the set temperature
If the heated wall does not attached with fins, estimate the power of the heater and the time required
for the air in the oven to reach the set temperature (Comment of your results)
You are required to provide all missing properties stating the source from which this data are
obtained.