A composite flat wall of a furnace is made of two materials 'A' and 'B'. The thermal conductivity of 'A' is twice of that of material 'B', while the thickness of layer of 'A' is half that of B. If the temperature at the two sides of the wall are 400 and 1200°K, then the temperature drop (in °K) across the layer of material 'A' is

Heat Transfer
A composite flat wall of a furnace is made of two materials 'A' and 'B'. The thermal conductivity of 'A' is twice of that of material 'B', while the thickness of layer of 'A' is half that of B. If the temperature at the two sides of the wall are 400 and 1200°K, then the temperature drop (in °K) across the layer of material 'A' is

125

150

133

160

125

150

133

160

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Heat Transfer
The Sieder-Tate correlation for heat transfer in turbulent flow in pipe gives Nu α Re0.8, where, Nu is the Nusselt number and Re is the Reynolds number for the flow. Assuming that this relation is valid, the heat transfer co-efficient varies with the pipe diameter (D) as

(D)-1.8

(D)0.2

(D)-0.2

(D)1.8

(D)-1.8

(D)0.2

(D)-0.2

(D)1.8

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Heat Transfer
For shell and tube heat exchanger, with increasing heat transfer area, the purchased cost per unit heat transfer area

Remains constant

Passes through a maxima

Decreases

Increases

Remains constant

Passes through a maxima

Decreases

Increases

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Heat Transfer
Arithmetic mean area can be used in heat transfer problem to calculate the heat flow by conduction through a cylinder which is

Thick walled

Both B and C

Having the value of Ao/Ai > 2

Thin walled having the value of Ao Ai/< 2

Thick walled

Both B and C

Having the value of Ao/Ai > 2

Thin walled having the value of Ao Ai/< 2

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Heat Transfer
In a laboratory test run, the rate of drying was found to be 0.5 x 10-3 kg/m².s, when the moisture content reduced from 0.4 to 0.1 on dry basis. The critical moisture content of the material is 0.08 on a dry basis. A tray dryer is used to dry 100 kg (dry basis) of the same material under identical conditions. The surface area of the material is 0.04 m²/kg of dry solid. The time required (in seconds) to reduce the moisture content of the solids from 0.3 to 0.2 (dry basis) is

6000

4000

5000

2000

6000

4000

5000

2000

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Heat Transfer
For turbulent flow in a tube, the heat transfer co-efficient is obtained from the Dittus-Boelter correlation. If the tube diameter is halved and the flow rate is doubled, then the heat transfer co-efficient will change by a factor of

6.1

1.74

37

1

6.1

1.74

37

1

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Heat Transfer

Heat Transfer The Sieder-Tate correlation for heat transfer in turbulent flow in pipe gives Nu α Re0.8, where, Nu is the Nusselt number and Re is the Reynolds number for the flow. Assuming that this relation is valid, the heat transfer co-efficient varies with the pipe diameter (D) as

Heat Transfer For shell and tube heat exchanger, with increasing heat transfer area, the purchased cost per unit heat transfer area

Heat Transfer Arithmetic mean area can be used in heat transfer problem to calculate the heat flow by conduction through a cylinder which is

Heat Transfer For turbulent flow in a tube, the heat transfer co-efficient is obtained from the Dittus-Boelter correlation. If the tube diameter is halved and the flow rate is doubled, then the heat transfer co-efficient will change by a factor of

Heat Transfer
The Sieder-Tate correlation for heat transfer in turbulent flow in pipe gives Nu α Re0.8, where, Nu is the Nusselt number and Re is the Reynolds number for the flow. Assuming that this relation is valid, the heat transfer co-efficient varies with the pipe diameter (D) as

Heat Transfer
For shell and tube heat exchanger, with increasing heat transfer area, the purchased cost per unit heat transfer area

Heat Transfer
Arithmetic mean area can be used in heat transfer problem to calculate the heat flow by conduction through a cylinder which is

Heat Transfer
For turbulent flow in a tube, the heat transfer co-efficient is obtained from the Dittus-Boelter correlation. If the tube diameter is halved and the flow rate is doubled, then the heat transfer co-efficient will change by a factor of