Q. For turbulent flow over a flat plate, the average value of Nusselt number is prescribed by the relation

Nu = 0.664 (Re)^0.5 (Pr)^0.33

Which of the following is then a false statement?

The average heat transfer coefficient increases as

View solution

Q. A nuclear reactor with its core constructed of parallel vertical plates 2.25 m high and 1.5 m wide has been designed on free convection heating of liquid bismuth. Metallurgical considerations limit the maximum surface temperature of the plate to 975 degree Celsius and the lowest allowable temperature of bismuth is 325 degree Celsius. Estimate the maximum possible heat dissipation from both sides of each plate. The appropriate correlation for the convection coefficient is
Nu = 0.13 (Gr Pr)^1/3

View solution

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

View solution

Q. Free correction modulus is given by

View solution

Q. The free convection coefficient is given by

h = C₁ d t m/l^(1 – 3m)

The value of exponent for laminar flow is

View solution

Q. For inclined plates we multiply Grashoff number with

View solution

Q. The free convection coefficient is given by

h = C₁ d t m/l^(1 – 3m)

The value of exponent for turbulent flow is

View solution

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

View solution

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

View solution

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

View solution

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

View solution

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

View solution

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

View solution

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

View solution

Q. The correlation for liquid metal is given by

View solution

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

View solution

Q. Mc Adam relation is given by

View solution

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

View solution

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

View solution

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

View solution