Q. A thin walled duct of 0.5 m diameter has been laid in an atmosphere of quiescent air at 15 degree Celsius and conveys a particular gas at 205 degree Celsius. Base your calculations on one meter length of the duct, estimate the convective coefficient of heat transfer

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Q. Free correction modulus is given by

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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 laminar flow is

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Q. For inclined plates we multiply Grashoff number with

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

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

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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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