‘Question39:-Furnaces have in common the general features of heat transfer from to
A-Hot gas source to a cold sink
B:-Hot refractory surface to hot gas
‏ای‎ gas source to refractory lined surface
D:-Cold sink to a hot gas source
Correct Answer: ೦00೦೧,
Question40::Which ofthe following sources are effective for harnessing the energy from Ocean 7

(i) Ocean waves
(1) Tidal range (rise and fall)

(i) Humiaity
tiv) Wine
sti) and (0)
8:10 and (iv)
oti) and (10)
0:40 and tiv)

Correct Answer:- ೦೧000
Question4::Which one of the following is not an assumption in multiple effect evaporator's calculations 7
[AcThere is no sub cooling of the condensate from different steam chests
B:-Heat transfer surface does not undergo fouling
ണം entering steam 15 at their boiling point
D:-Pressure is same in every effect
Correct Answer:- Option-D

Question42:-A hollow sphere of intemal diameter ID = 20 cm and outer diameter OD = 30 cm contains hot fluid. What should be the critical radius of insulation for maximum rate ‏۴ہ‎
‎heat transfer ? Thermal conductivity k = 0.86 W/mK and convection heat transfer coefficient of outer fluid ‏يذ‎ = 20 W/m" K.

‎m‏ 086ھ
‎mm‏ 8.6-:8

‎8.6m

‎5:0086 em

‎Correct Answer: Option-C

‎Question43:-A metal ball of radius 0.1 m at a uniform temperature of 90°C is left in air at 30°C. The density and the specific heat of the metal are 3000 kg/m’ and ಗ
respectively. The heat transfer co-efficient is 50 W/m".K Neglecting the temperature gradients inside the ball, the time taken (in hours) for the ball to cool to 60°C is

‎കടട
‏555ھ‎
‎0.51
‎D-015
‎Correct Answer:- Option-D

‎Question44:-An athlete is sitting unclothed in a locker room whose dark walls are at a temperature of 15°C. Estimate his rate of heat loss by radiation, assuming a skin temperature of,
34°C and ‏دع‎ 0.70. Take the surface area of the body nat in contact with the chair to be 1.5 ஈட்‌

‎കേ

‎B:-100 W

‎W‏ می

‎D-80W

‎Correct Answer:- ೦೧000
Question45:-A shirtless rider under a circus tent feels the heat radiating from the sunlit portion of the tent. Calculate the temperature of the tent canvas based on the following
information : The shirtless rider's skin temperature is 34.0°C and has an emissivity of 0.970. The exposed area of skin is 0.400 ஈட்‌. He receives radiation at the rate of 20.0 W- half
what you would calculate ifthe entire region behind him was hot. The rest of the surroundings are at 34.0°C.

‎കട

‎B:-45°C

‎6>

‏56ھ

‎Correct Answer:- ೦೧000

‎Question46:-A room heater is made up of 6 thin-wall tubes of copper, each 1.0 m long and 4.0 cm in diameter. Hot water at 77°C circulates constantly through the tubes. Calculate the
‘amount of heat radiated per second in a room where the average temperature is 27°C, The emissivity of copper = 0.8 and Stefan’s constant = 5.67 x10" Wm? ‏كتير‎

‏6( 236::ھ