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

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

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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 correlation for liquid metal is given by

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

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Q. Mc Adam relation is given by

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

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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. 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. 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. For laminar flow, Reynolds number should be

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Q. For turbulent flow, Reynolds number must be

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Q. What is the value of convective coefficient of air and superheated steam in case of forced convection?

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Q. Heat is being transferred by convection from water at 48 degree Celsius to glass plate whose surface is exposed to water at 40 degree Celsius. The thermal conductivity of water is 0.6 W/m K and the thermal conductivity of glass is 1.2 W/m K. The spectral gradient of temperature in the water at the water glass interface is 10¯⁴ K/m. The heat transfer coefficient in W/m² K is

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