Q. Mark the system where heat transfer is given by forced convection

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Q. Forced convection in a liquid bath is caused by

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Q. A finned tube hot water radiator with a fan blowing air over it is kept in rooms during winter. The major portion of the heat transfer from the radiation is due to

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Q. A body cooling from 80 degree Celsius to 70 degree Celsius takes 10 minutes when left exposed to environmental conditions. If the body is to cool further from 70 degree Celsius to 60 degree Celsius under the same external conditions, it will take

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Q. On a summer day, a scooter rider feels more comfortable while on the move than while at a stop light because

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Q. What is the value of convective coefficient of oil in case of forced convection?

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Q. A sphere, a cube and a thin circular plate, all made of the same material and having the same mass are initially heated to the temperature of 250 degree Celsius. When left in air at room temperature, what will be their response to cooling?

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Q. Newton-Rikhman law is given by

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Q. The value of film coefficient is dependent upon

(i) Boundary layer configuration
(ii) Geometry and orientation of the surface
(iii) Surface conditions

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Q. The convection coefficients for boiling and condensation lie in the range

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Q. Forced air flows over a convection heat exchanger in a room heater, resulting in a convective heat transfer coefficient 1.136 k W/m² K. The surface temperature of heat exchanger may be considered constant at 65 degree Celsius, and the air is at 20 degree Celsius. Determine the heat exchanger surface area required for 8.8 k W of heating

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Q. A region of fluid motion near a plate in which temperature gradient exist is

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Q. Thermo-physical properties of the fluid are represented by

(i) Density
(ii) Viscosity
(iii) Specific heat
(iv) Thermal conductivity

Identify the correct option

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Q. A motor cycle cylinder consists of ten fins, each 150 mm outside diameter and 75 mm inside diameter. The average fin temperature is 500 degree Celsius and the surrounding air is at 20 degree Celsius temperature. Make calculations for the rate of heat dissipation from the cylinder fins by convection when motor cycle is stationary and convective coefficient is 6 W/m² K

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Q. Air at 20 degree Celsius flows over a flat surface maintained at 80 degree Celsius. The local heat flow at a point was measured as 1250 W/m² .Take thermal conductivity of air as 0.028 W/m K, calculate the temperature at a distance 0.5 mm from the surface

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Q. The convective heat transfer coefficient in laminar flow over a flat plate

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Q. For laminar 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?

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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

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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

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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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