A thin, flat & square plate measuring 2 m × 2 m is freely hanging in ambient air at 25°C. It is exposed to the solar radiation falling on one side of the plate at the rate of 500 W/m2. The plate temperature will remain constant at 30°C, if the convective heat transfer co-efficient is ________________ W/m2 °C ?

Related Mcqs:

1. What is the critical radius of insulation (cms) for a metallic cylinder, if the convective heat transfer co-efficient with the ambient atmosphere is 5 W/m2. °K? Thermal conductivity of metal and insulation material are 40 and 0.1 W/m.°K respectively ?

   A. 2
   B. 8
   C. 10
   D. 40

2. 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____________________?

   A. 100
   B. 900
   C. 9000
   D. 10000

3. Nusselt number is related to Grashoff number (Gr) in turbulent & laminar flow respectively, in respect of free convection over a vertical flat plate as_________________?

   A. Gr0.25, Gr
   B. Gr0.25, Gr0.33
   C. Gr, Gr0.25
   D. Gr0.33, Gr0.25

4. 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

5. The laminar boundary layer thickness in zero pressure gradient flow over a flat plate along the x-direction varies as x0.5 while the thickness of turbulent boundary layer varies as (where, x = distance from the leading edge) ?

   A. x1.5
   B. x0.8
   C. x-1.5
   D. x-0.8

6. The efficiency of a Carnot heat engine operating between absolute temperatures T1 and T2 (when, T1 > T2) is given by (T1 – T2)/T1. The co-efficient of performance (CO.P.) of a Carnot heat pump operating between T1 and T2 is given by_________________?

   A. T1/(T1-T2)
   B. T2/(T1-T2)
   C. T1/T2
   D. T2/T1

7. 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

8. In a furnace with heating element temperature at 1700°C, the dominant mechanism of heat transfer will be__________________?

   A. Conduction
   B. Radiation
   C. Natural convection
   D. Forced convection

9. In condensers used in thermal power plants, steam is normally used in shell side and cooling water on the tube side, because of the reason that ?

   A. Compared to the mass flow rate of cooling water, the rate of condensation of steam is
   invariably smaller
   B. Maintaining vacuum on tube side is more difficult than that on the shell side
   C. Water velocity can be increased conveniently to increase the overall heat transfer co-efficient
   because of its lower specific volume compared to steam
   D. Condenser can act as a storage unit for condensed steam

10. Maximum amount of thermal radiation is emitted at all wavelengths at any specified temperature by a/an ______________ body?

    A. Grey
    B. Black
    C. Opaque
    D. White