1
GATE ME 2013
MCQ (Single Correct Answer)
+1
-0.3
Consider one-dimensional steady state heat conduction, without heat generation, in a plane wall; with boundary conditions as shown in the figure below. The conductivity of the wall is given by $$k = {k_0} + bT;$$ where $${k_0}$$ and $$b$$ are positive constants, and $$T$$ is temperature. GATE ME 2013 Heat Transfer - Conduction Question 35 English

As $$x$$ increases, the state temperature gradient $$(dT/dx)$$ will

A
remain constant
B
be zero
C
increase
D
decrease
2
GATE ME 2013
MCQ (Single Correct Answer)
+1
-0.3
Consider one-dimensional steady state heat conduction along x-axis $$\left( {0 \le x \le L} \right),$$ through a planewall with the boundary surfaces $$(x=0$$ and $$x=L)$$ maintained at temperatures of $${0^ \circ }C$$ and $${100^ \circ }C$$. Heat is generated uniformly throughout the wall. Choose the CORRECT statement.
A
The direction of heat transfer will be from the surface at 100°C to the surface at $${0^ \circ }C$$.
B
The maximum temperature inside the wall must be greater than $${100^ \circ }C$$.
C
The temperature distribution is linear within the wall.
D
The temperature distribution is symmetric about the mid-plane of the wall.
3
GATE ME 2013
MCQ (Single Correct Answer)
+2
-0.6
A steel ball of diameter $$60$$ $$mm$$ is initially in thermal equilibrium at $${1030^ \circ }C$$ in a furnace. It is suddenly removed from the furnace and cooled in ambient air at $${30^ \circ }C$$ with convective heat transfer coefficient $$h = 20\,W/{m^2}K.$$ The thermo-physical properties of steel are: density $$\rho = 7800\,\,kg/{m^3},$$ , conductivity $$k = 40 W/mK$$ and specific heat $$c = 600 J/kgK.$$ The time required in seconds to cool the steel ball in air from $${1030^ \circ }C$$ to $${430^ \circ }C$$ is
A
$$519$$
B
$$931$$
C
$$1195$$
D
$$2144$$
4
GATE ME 2013
MCQ (Single Correct Answer)
+2
-0.6
Two large diffuse gray parallel plates, separated by a small distance, have surface temperatures of $$400$$ $$K$$ and $$300$$ $$K.$$ If the emissivities of the surfaces are $$0.8$$ and the Stefan-Boltzmann constant is $$5.67 \times {10^{ - 8}}$$ $$W/{m^2}{K^4},$$ the net radiation heat exchange rate in $$kW/{m^2}$$ between the two plates is
A
$$0.66$$
B
$$0.79$$
C
$$0.99$$
D
$$3.96$$
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