Q. Three fins of equal length and diameter but made of aluminum, brass and cast iron is heated to 200 degree Celsius at one end. If the fins dissipate heat to the surrounding air at 25 degree Celsius, the temperature at the free end will be least in

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Q. Two long rods A and B of the same diameter have thermal conductivities k and 4k and have one of their end inserted into a furnace at 400 K. At 9.5 m away section from the furnace, the temperature of rod B is120 degree Celsius. So find out at what end from the furnace end, the same temperature would be reached in the rod A?

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Q. The following factors need consideration for the optimum design of fins

(i) Cost

(ii) Space considerations

(iii) Weight considerations

Choose the correct option

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Q. A heating unit is made in the form of a vertical tube of 50 mm outside diameter and 1.2 m height. The tube is fitted with 20 steel fins of rectangular section with height 40 mm and thickness 2.5 mm. The temperature at the base of fin is 75 degree Celsius, the surrounding air temperature is 20 degree Celsius and the heat transfer coefficient between the fin as well as the tube surface and the surrounding air is 9.5 W/m² K. If thermal conductivity of the fin material is 55 W/m K, find the amount of heat transferred from the tube with fin

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Q. The fins would be effective for heat conduction if the ratio P k/h A C is

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Q. Consider the following statements pertaining to heat transfer through fins

(i) They must be arranged at right angles to the direction of flow of working fluid

(ii) The temperature along the fin is variable and accordingly heat transfer rate varies along the fin elements

(iii) Fins are equally effective irrespective whether they are on the hot side or cold side of the fluid

(iv) Fins are made of materials that have thermal conductivity higher than that of wall

Identify the correct statements

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Q. An increase in fin effectiveness is caused by high value of

(i) Convective coefficient

(ii) Thermal conductivity

(iii) Circumference

(iv) Area

Identify the correct statement

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Q. Choose the correct option regarding fin efficiency and fin effectiveness

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Q. The handle of a saucepan, 30 cm long and 2 cm in diameter, is subjected to 100 degree Celsius temperature during a certain cooking operation. The average unit surface conductance over the handle surface is 7.35 W/m² degree in the kitchen air at 24 degree Celsius. The cook is likely to grasp the last 10 cm of the handle and hence the temperature in this region should not exceed 38 degree Celsius. What should be the thermal conductivity of the handle material to accomplish it? The handle may be treated as a fin insulated at the tip

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Q. Let us assume a square section fin split longitudinally and used as two fins. This will result in

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Q. Mark the false statement regarding effectiveness of fin

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Q. The convective coefficient in boilers and condenser is

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Q. In thermometer heat is dissipated from which end?

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Q. The thermometric well is treated as a fin of

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Q. Thermometric well apparatus doesn’t consists of

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Q. For what purpose we use thermometric well?

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Q. In thermometric well, the error can be minimized by

(i) The value of parameter ml slows down by some quantity.

(ii) Lagging of the tube so that conduction of heat along its length is arrested

Identify the correct option

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Q. Suppose there are two reservoirs A and B. Let TA and TB be the temperatures of respective reservoirs. At any instant say TA = TB. In this case maximum temperature occurs at

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Q. The relevant boundary conditions in case of heat transfer from a bar connected to two heat sources at different temperatures are

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Q. “The tube that is used in thermometric well is considered as a hollow fin and the temperature distribution is obtained by using the relation applicable to infinitely long fin”. Choose the correct option

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