‘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
C-Hot gas source to refractory lined surface
D:-Cold sink to a hot gas source
Correct ೧೦೫೮: ೦00೦೧,
Question40::Which ofthe following sources are effective for hamessing the energy from Ocean ?

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

(i) Humiaity
tiv) Wind
sti) and i)
8:10 30ರ (1)
oti) and ti
Dei) and (iv)

Correct Answer:- Option-é
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
ಆ ಯ steam is 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 of
heat transfer ? Thermal conductivity k = 0.86 W/mK and convection heat transfer coefficient of outer fluid h, = 20 Wim" K.

۸-086 0
B:-B.6 mm

೧೩.6೦೫

5:0086 ला

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 0.4 (414.6
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
8:-55.5
0.52
0-025
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 €= 0.70. Take the surface area of the body nat in contact with the chair to be 1.5 m°

കേ

B:-100 W

c-140 மு

0۷

09۲۷۶١۲ ۸۳۰۸۷9۴۰ ‏۸۸ا05‎
‎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 m”. 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

മെ

D-43.5°C

Correct Answer:- Option-é

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? K~*

23615