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Chapter:

Conduction-with-Heat-Generation

1. The lumped parameter solution for transient conduction can be conveniently stated as


Hint Answer

2. Let re is some conduction resistance, n temperature becomes a function of
(i) Biot number
(ii)Fourier number
(iii) Dimensionless parameter


Hint Answer

3. The following data pertains to junction of a rmocouple wire used to measure temperature of gas stream.
Density = 8500 kg/m3, specific heat = 325 J/kg K, rmal conductivity = 40 W/m K and heat transfer coefficient between junction and gas = 215 W/m2 K.
If rmocouple junction can be approximated as 1 mm diameter sphere, determine how long it will take for rmocouple to read 99% of initial temperature difference


Hint Answer

4. With respect to above problem, determine temperature inside plate 12.5 mm from mid plane after 3 minutes


Hint Answer

5. Glass spheres of 2 mm radius and at 500 degree Celsius are to be cooled by exposing m to an air stream at 25 degree Celsius. Find maximum value of convective coefficient that is permissible. Assume following property values
Density = 2250 kg/m3
Specific heat = 850 J/kg K
Conductivity = 1.5 W/m K


Hint Answer

6. A low value of time constant can be achieved for a rmocouple by
(i) Increasing wire diameter
(ii) Increasing value heat transfer coefficient
(iii) Use light metals of low density and low specific heat


Hint Answer

7. A 2 cm thick steel slab heated to 525 degree Celsius is held in air stream having a mean temperature of 25 degree Celsius. Estimate time interval when slab temperature would not depart from mean value of 25 degree Celsius by more than 0.5 degree Celsius at any point in slab. The steel plate has following rmal physical properties
Density = 7950 kg/m3
C P = 455 J/kg K
K = 46 W/m K


Hint Answer

8. What percentage of water an average human body can have?


Hint Answer

9. A solid which extend itself infinitely in all directions of space is termed as finite solid.


Hint Answer

10. A 12 cm diameter cylindrical bar, initially at a uniform temperature of 40 degree Celsius, is placed in a medium at 650 degree Celsius with convective coefficient of 22 W/m2 K. Determine time required for center to reach 255 degree Celsius. For material of bar:
Thermal conductivity = 20 W/m K
Density = 580 kg/m3
Specific heat = 1050 J/kg K


Hint Answer

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Topics

This Chapter Conduction-with-Heat-Generation consists of the following topics

Transient (Unsteady State Heat Conduction)

The lumped parameter solution for transient conduction can be conveniently stated as

;

Let re is some conduction resistance, n temperature becomes a function of
(i) Biot number
(ii)Fourier number
(iii) Dimensionless parameter

;

The following data pertains to junction of a rmocouple wire used to measure temperature of gas stream.
Density = 8500 kg/m3, specific heat = 325 J/kg K, rmal conductivity = 40 W/m K and heat transfer coefficient between junction and gas = 215 W/m2 K.
If rmocouple junction can be approximated as 1 mm diameter sphere, determine how long it will take for rmocouple to read 99% of initial temperature difference

;

With respect to above problem, determine temperature inside plate 12.5 mm from mid plane after 3 minutes

;

Glass spheres of 2 mm radius and at 500 degree Celsius are to be cooled by exposing m to an air stream at 25 degree Celsius. Find maximum value of convective coefficient that is permissible. Assume following property values
Density = 2250 kg/m3
Specific heat = 850 J/kg K
Conductivity = 1.5 W/m K

;

A low value of time constant can be achieved for a rmocouple by
(i) Increasing wire diameter
(ii) Increasing value heat transfer coefficient
(iii) Use light metals of low density and low specific heat

;

A 2 cm thick steel slab heated to 525 degree Celsius is held in air stream having a mean temperature of 25 degree Celsius. Estimate time interval when slab temperature would not depart from mean value of 25 degree Celsius by more than 0.5 degree Celsius at any point in slab. The steel plate has following rmal physical properties
Density = 7950 kg/m3
C P = 455 J/kg K
K = 46 W/m K

;

What percentage of water an average human body can have?

;

A solid which extend itself infinitely in all directions of space is termed as finite solid.

;

A 12 cm diameter cylindrical bar, initially at a uniform temperature of 40 degree Celsius, is placed in a medium at 650 degree Celsius with convective coefficient of 22 W/m2 K. Determine time required for center to reach 255 degree Celsius. For material of bar:
Thermal conductivity = 20 W/m K
Density = 580 kg/m3
Specific heat = 1050 J/kg K

;