One face of a furnace wall is at 1030°C and the other face is exposed to room temperature (30°C). If the thermal conductivity of furnace wall is 3 W. m-1. k-1 and the wall thickness is 0.3 m, the maximum heat loss (in W/m) is____________________?

Related Mcqs:

1. A furnace is made of a refractory brick wall of thickness 0.5 metre and thermal conductivity 0.7 W/m.°K For the same temperature drop and heat loss, this refractory wall can be replaced by a layer of diatomaceous earth of thermal conductivity 0.14 W/m.K and thickness ______________ metre?

   A. 0.01
   B. 0.1
   C. 0.25
   D. 0.5

2. The ratio of thermal & electrical conductivity is same for all the metals at the same temperature; and at around room temperature, this ratio is proportional to(where, T = absolute temperature, °K) ?

   A. T
   B. 1/T
   C. T2
   D. 1/T2

3. Maximum heat dissipation occurs from a steel wire (k = 0.5 W/m. k) of 15 mm diameter exposed to air (h = 20W/m2 .k), when the insulation thickness is ________________ mm?

   A. 15
   B. 25
   C. 10
   D. 30

4. Heat transfer to the water wall in a high pressure water wall type boiler furnace is mainly by_________________?

   A. Conduction
   B. Convection
   C. Radiation
   D. Both A. & B.

5. In case of water (Prandtl number ≈ 6) flowing over a flat plate heated over the entire length, the thermal boundary layer thickness as compared to hydrodynamic boundary layer thickness is ?

   A. Less
   B. More
   C. Equal
   D. Unpredictable

6. Thermal diffusivity of a substance is proportional to (where, k = Thermal conductivity) ____________________?

   A. 1/k
   B. k
   C. k2
   D. 1/k2

7. Temperature of hot gases flowing in a pipe is measured by a thermocouple inserted in the thermal well. The thermal well made of ______________ will facilitate the most accurate measurement of the temperature ?

   A. Copper
   B. Steel
   C. Aluminium
   D. Brass

8. Heating the Hypo-eutectoid steels to 30°C above the upper critical temperature line, soaking at that temperature and then cooling slowly to the room temperature to form a pearlite & ferrite structure is called_______________________?

   A. Tempering
   B. Hardening
   C. Annealing
   D. Normalising

9. Out of the following, maximum temperature drop for a given heat flow & for the same thickness will be in the case of________________?

   A. Steel
   B. Glass wood
   C. Copper
   D. Fireclay bricks

10. Which of the following parameters is not responsible for the heat loss from a hot steam carrying bare pipe surface located in a room without fans ?

    A. Emissivity of pipe surface
    B. Diameter & length of the pipe
    C. Temperature of hot pipe surface & that of air in the room
    D. None of these