ISRO Scientist or Engineer Mechanical 2006

The formation of frost on cooling coils in a refrigerator

An air-conditioned room has one of the walls, which is $$5m \times 3m$$ of 3.75 cm thick brick. The conditioned space is maintained at $$27^\circ C$$ when the outside temperature is $$47^\circ C$$. Variation of thermal conductivity with temperature of the wall is given by $$k = 1 + 2 \times 10^{-4}T, where T is in degree Kelvin, and k is in $$W/m^\circ K$$. The heat gained by the conditioned space through this wall is

A mild steel tank of wall thickness 12 mm contains water at $$100^\circ C$$. The atmospheric temperature is $$20^\circ C$$. The thermal conductivity of mild steel is $$50 W/mK$$, and the heat transfer co-efficients for inside and outside the tank are 2850 and $$10 W/m^2 K$$, respectively. Calculate the rate of heat loss per $$m^2$$ of tank surface and the temperature of the outside surface of the tank.

In order to burn 1 Kg of CH4 completely the minimum number of kilograms of Oxygen needed is (take atomic weight of H, C, O as 1, 12, 16 respectively)

The vector field $$\overrightarrow{F} = x\widehat{i} - y\widehat{j}$$ (where $$\widehat{i}$$ and $$\widehat{j}$$ are unit vectors) is

For flow through a horizontal pipe, the pressure gradient $$\frac {dp}{dx} in the flow direction is

The transition Reynolds number for flow over a flat plate is $$5 \times 10^5.$$ What is the distance from the leading edge at which transition will occur for flow of water with a uniform velocity of 1 m/s ? (For water, the kinematic viscosity, $$\upsilon = 0.858 \times 10^{-6} m^2/s)$$

Between section 1 and 2 of a pipe a pump, a heater, a very rough pipe and an orifice plate are placed. The Bernoulli equation can be applied between 1 and 2 if

A one dimensional flow is one which

A piece weighing 3 kg in air was found to weigh 2.5 kg when submerged in water. Its specific gravity is