Q. Air enters a rectangular duct measuring 30 cm by 40 cm with a velocity of 8.5 m/s and a temperature of 40 degree Celsius. The flowing air has a thermal conductivity 0.028 W/m K, kinematic viscosity 16.95 * 10¯⁶ m²/s and from empirical correlations the Nusselt number has been approximated to be 425. Find out the flow Reynolds number

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Q. Reynolds number is given by the quantity
(Where,
p is density
δ is viscosity
V is volume
l is length)

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Q. Velocity within the given fields would be similar in magnitude, direction and turbulence pattern when

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Q. The ratio of inertia force to viscous force is known as

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Q. Air flows through a 10 cm internal diameter tube at the rate of 75 kg/hr. Measurements indicate that at a particular point in the tube, the pressure and temperature of air are 1.5 bar and 325 K whilst the tube wall temperature is 375 K. Find heat transfer rate from one meter length in the region of this point
The general non-dimensional correlation for turbulent flow in the tube is

Nu = 0.023 (Re)^0.8 (Pr)^0.4

Where the fluid properties are evaluated at the bulk temperature

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Q. The oil pan of 1.6 engine approximates a flat plate 0.3 m wide by 0.45 m long and protrudes below the framework of the automobile. The engine oil is at 95 degree Celsius and the ambient air temperature is 35 degree Celsius. If the automobile runs at 36 km/hr, make calculations for the rate of heat transfer from the oil-pan surface. Assume negligible resistance to conduction through the oil pan

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Q. A heat treat steel plate measures 3 m by 1 m and is initially at 30 degree Celsius. It is cooled by blowing air parallel to 1 m edge at 9 km/hr. If the air is at 10 degree Celsius. Estimate the convection heat transfer from both sides of the plate

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Q. Calculate the rate of heat loss from a human body which may be considered as a vertical cylinder 30 cm in diameter, and 175 cm high while standing in a 30 km/hr wind at 15 degree Celsius. Human has a surface temperature of 35 degree Celsius

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Q. Investigate the effect of following condition on the average value of heat transfer coefficient in flow through a tube

Two fold increases in flow velocity by varying mass flow rate

It may be presumed that there is no change in the temperature of the liquid and the tube wall, and that the flow through the tube is turbulent in character

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Q. Mc Adam relation is given by

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Q. Which of the following is true for turbulent flow?

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Q. The correlation for liquid metal is given by

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Q. For a plate of length l, an average value of Nusselt number is given by

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Q. The local film coefficient for laminar flow past a flat plate may be obtained from the correlation

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Q. Air at atmospheric pressure and 20 degree Celsius flows with 6 m/s velocity through main trunck duct of air conditioning system. The duct is rectangular in cross-section and measures 40 cm by 80 cm. Determine heat loss per meter length of duct corresponding to unit temperature difference. The relevant thermos-physical properties of air are
v = 15 * 10¯⁶ m²/s

α = 7.7 * 10¯² m²/hr

k = 0.026 W/m degree

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Q. For laminar flow, Prandtl number must be more than

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Q. For laminar flow, Reynolds number must not be less than

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Q. A horizontal heated plate at 200 degree Celsius and facing upwards has been placed in still air at 20 degree Celsius. If the plate measures 1.25 m by 1 m, make calculations for the heat loss by natural convection. The convective film coefficient for free convection is given by the following empirical relation

h = 0.32 (α)^0.25 W/m² K

Where α is the mean film temperature in degrees kelvin

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Q. Which of the following is true for laminar flow?

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Q. The free convection coefficient is given by

h = C₁ d t m/l^(1 – 3m)

The value of exponent for turbulent flow is

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