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Identify the wrong statement.
1. Reversed Carnot cycle is nothing but Carnot Refrigeration cycle.

2. The efficiencies of all reversible heat engines operating the same two reservoirs
are the same.

3. The Carnot efficiency approaches unity when the low temperature reservoir
goes more than the high temperature reservoir.

4. Work is more valuable form of energy than heat.
A) 1 and3 B) 2 03 D) 4

Heat transfer coefficient for free convection in gases, forced convection in gases and
vapours, and for boiling water lie, respectively in the ranges of

A) 5-15, 20 — 200 and 3,000 — 50,000 W/mK

8) 5-50, 200 - 5000 876 50,000 — 10° W/m?K
C) 5-35, 500 - 10,000 and 10°- 10° ۴

0) 5 - 100, 200 — 1,000 and a constant 10° Wim?K

A thin plate 2 m long and 1 m width is placed in an air stream (density = 1.0 kg/m®
and viscosity = 0.85 x 10° Pa.s) moving with a velocity of 1 m/s. What will be the
type of flow over the plate ?

A) Turbulent flow over the entire plate
B) Laminar flow over the entire plate

C) Upto 0.3 m length from the leading edge of the plate the flow is Laminar then
the remaining plate length flow is Turbulent

D) Upto 0.7 m length from the leading edge of the plate the flow is Laminar then
the remaining plate length flow is Turbulent

A pipe carrying steam runs in a large room and is exposed to surrounding air at a
temperature of 27°C. The pipe surface is subjected to 327°C. Find the loss of heat to
surroundings due to thermal radiation. Assume pipe surface emissivity = 0.5.

A) 2.50 kW/m? 8) 3.44 0/೧೭ ©) 4.82 kW/m? D) 5.68 kW/m?

The Nusselt number for fully developed laminar flow in a tube under constant heat
flux is equal to

A) The product of Reynolds and Prandtl number
B) 3.66
00 1
D) The square root of heat transfer coefficient

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