1
GATE PI 2009
MCQ (Single Correct Answer)
+2
-0.6
The pressure drop for laminar flow of a liquid in a smooth pipe at normal temperature and pressure is
A
directly proportional to density
B
inversely proportional to density
C
independent of density
D
proportional to (density)$$\,{}^{0.75}$$
2
GATE PI 2009
MCQ (Single Correct Answer)
+2
-0.6
Heat is being transferred convectively from a cylindrical nuclear reactor fuel rod of $$50mm$$ diameter to water at $${70^ \circ }C$$, under steady state condition, the rate of heat generation within the fuel element is $$50 \times {10^6}\,\,W/{m^3}$$ and the convective heat transfer coefficient is $$1$$ $$kW/{m^2}K.$$ The outer surface temperature of the fuel element would be
A
$${700^ \circ }C$$
B
$${625^ \circ }C$$
C
$${550^ \circ }C$$
D
$${400^ \circ }C$$
3
GATE PI 2009
MCQ (Single Correct Answer)
+2
-0.6
Autogeneous gas tungsten arc welding of a steel plate is carried out with welding current of $$500A,$$ voltage of $$20V,$$ and weld speed of $$20mm/min.$$ Consider the heat transfer efficiency from the arc to the weld pool as $$90\% $$. The heat input per unit length (in $$kJ/mm$$) is
A
$$27$$
B
$$35$$
C
$$45$$
D
$$55$$
4
GATE PI 2009
MCQ (Single Correct Answer)
+5
-1.5
Resistance spot welding of two steel sheets is carried out in lap joint configuration by using a welding current of $$3$$ $$KA$$ and a weld time of $$0.2s.$$ A molten weld nugget of volume $$20m{m^3}$$ is obtained. The effective contact resistance is $$200\mu \Omega .$$ The material properties of steel are given as (i) latent heat of melting $$1400$$ $$kJ/kg,$$ (ii) density $$8000$$ $$kg/{m^3},$$ (iii) melting temp $${1520^ \circ }C$$, (iv) specific heat $$0.5$$ $$kJ/kgC.$$ The ambient temp is $$20C.$$

Heat (in Joules) used for producing weld nugget will be (assuming $$100\% $$ heat transfer efficiency

A
$$324$$
B
$$334$$
C
$$344$$
D
$$354$$
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