Why is there a negative sign in Fournier’s law of heat conduction? If one adds electrical...
Why is there a negative sign in Fournier’s law of heat conduction?
If one adds electrical insulation to a circular wire, which of the following would happen?
a) Conduction resistance will drop
b) Convection resistance will drop
c) hinder transfer of heat in the wire to surroundings.
d) Help the transfer of heat in the wire surroundings.
Homework Answers
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Why is there a negative sign in Fournier’s law of heat
conduction?
If one adds electrical...
2-157 A long electrical resistance wire of radius r.-0.25 cm has a thermal conductivity kwire-15 W/m-K. Heat is gene...
2-157 A long electrical resistance wire of radius r.-0.25 cm has a thermal conductivity kwire-15 W/m-K. Heat is generated uniformly in the wire as a result of resistance heating at a constant rate of 0.5 W/cm3. The wire is covered with polyethylene insulation with a thickness of 0.25 cm and thermal conductivity of ks 0.4 W/m K. The outer surface of the insulation is subjected to free convection in air at 20°C and a convection heat transfer coefficient of 2...
5. Problem 3.54 (Textbook) (20 points) KNOWN: Diameter of electrical wire. Thickness and thermal conductivity of...
5. Problem 3.54 (Textbook) (20 points) KNOWN: Diameter of electrical wire. Thickness and thermal conductivity of rubberized sheath. Contact resistance between sheath and wire. Convection coefficient and ambient air temperature. Maximum allowable sheath temperature. FIND: Maximum allowable power dissipation per unit length of wire. Critical radius of insulation. SCHEMATIC: Air Wire Egen. D-2 mm Two Tini Tino To Ric = 3x10-4 m2-KW Insulation, t = 2 mm T= 20°C Ric Rcond conv k = 0.13 W/m-K Tmax = 50°C h...
This is for the subject of Heat Transfer. Any clues on how to solve this would...
This is for the subject of Heat Transfer. Any clues on how to
solve this would be greatly appreciated thanks
2 [ABET]) An electric cable of radius ri andTaur thermal conductivity ke is enclosed by an insulating sleeve whose outer surface is of radius r2 and experiences convection heat transfer and radiation exchange with the adjoining air and large surroundings, respectively. When electric current passes through the cable, thermal energy is generated within the cable at a volumetric rate q....
The heat that is conducted through a body must frequently be removed by other heat transfer...
The heat that is conducted through a body must frequently be removed by other heat transfer processes. For example, the heat generated in an electronic device must be dissipated to the surroundings through convection by means of fins. Consider the one-dimensional aluminum fin (thickness t 3.0 mm, width 20 cm, length L) shown in Figure 1, that is exposed to a surrounding fluid at a temperature T. The conductivity of the aluminum fin (k) and coefficient of heat convection of...
(a) (iWhen is heat transfer through a fluid by conduction or by convection? For what case...
(a) (iWhen is heat transfer through a fluid by conduction or by convection? For what case is the rate of heat transfer higher? How does the convection heat transfer coefficient differ from the thermal conductivity of a fluid? (ii) Explain the physical significance of Nusselt number (ii) By definition, discuss hydraulic diameter. Obtain an expression for hydraulic diameter of a circular tube of diameter, D (b) The local atmospheric pressure in Gboko, Benue State Nigeria (elevation 1610 m), is 834...
Can someone please help with these questions, thanks... Chapter 14 1. Define heat. 2. (T/F) Heat...
Can someone please help with these questions, thanks...
Chapter 14 1. Define heat. 2. (T/F) Heat is fundamentally different from 3. Define mechanical equivalent of heat 4. What is the difference between temperature and heat? 5. Why doe 6. Does the temperature of a substance change during a phase chang 7. Sketch Fig. 14.7 8. Can energy, explain. s a phase change require energy transfer? e? substance? evaporation and condensation happen below the boiling point of a What limitations does...
1) 2) 3) PROJECT #1 (2.5 Marks): The heat that is conducted through a body must...
1)
2)
3)
PROJECT #1 (2.5 Marks): The heat that is conducted through a body must frequently be removed by other heat transter processes. For example, the heat generated in an electronic device must be dissipated to the surroundings through convection by means of fins. Consider the one-dimensional aluminum fin (thickness t 3.0 mm, width Z 20 cm, length L) shown in Figure 1, that is exposed to a surrounding fluid at a temperature 1. The conductivity of the aluminum...
A3. (a) According to Fourier's Law of thermal conduction, the heat flux through a solid is...
A3. (a) According to Fourier's Law of thermal conduction, the heat flux through a solid is given by the solid's thermal conductivity k multiplied by the negative of the local temperature gradient. If the temperature in the solid is given by the function T(x, y, z)= 30e **(y2 + z), determine an expression for the heat flux through an internal surface with normal n=2i+j+2k [7 marks) (b) If f(t)=3sin ox and g(t)= 2 cos(@t++), determine the amplitude of the function...
A) Describe radiation and conduction as modes of heat transfer; what are the key differences betw...
a) Describe radiation and conduction as modes of heat transfer; what are the key differences between them? [41 b) You are thinking of installing an observation window to a walk in fridge wall. Compare the rate of heat transfer of the original fridge wall (no window) with the new one (with window). The original wall has an area of 8m2 and is composed of three layers in series, 0.3 cm steel, 3 cm cork for insulation and a 2.5 cm...
Assume two negative charges are placed close to each other, with one charge fixed and one...
Assume two negative charges are placed close to each other, with one charge fixed and one charge free to move. The free charge will: O a accelerate away from the fixed charge. b. move closer to the fixed charge. Og C. orbit the fixed charge in a circular motion. d. remain stationary. Which of the following statements about insulating materials is correct? oa. Soaking paper in salt water decreases its insulation capability O b. The amount of current flowing in...
2-157 A long electrical resistance wire of radius r.-0.25 cm has a thermal conductivity kwire-15 W/m-K. Heat is generated uniformly in the wire as a result of resistance heating at a constant rate of 0.5 W/cm3. The wire is covered with polyethylene insulation with a thickness of 0.25 cm and thermal conductivity of ks 0.4 W/m K. The outer surface of the insulation is subjected to free convection in air at 20°C and a convection heat transfer coefficient of 2...
5. Problem 3.54 (Textbook) (20 points) KNOWN: Diameter of electrical wire. Thickness and thermal conductivity of rubberized sheath. Contact resistance between sheath and wire. Convection coefficient and ambient air temperature. Maximum allowable sheath temperature. FIND: Maximum allowable power dissipation per unit length of wire. Critical radius of insulation. SCHEMATIC: Air Wire Egen. D-2 mm Two Tini Tino To Ric = 3x10-4 m2-KW Insulation, t = 2 mm T= 20°C Ric Rcond conv k = 0.13 W/m-K Tmax = 50°C h...
This is for the subject of Heat Transfer. Any clues on how to
solve this would be greatly appreciated thanks
2 [ABET]) An electric cable of radius ri andTaur thermal conductivity ke is enclosed by an insulating sleeve whose outer surface is of radius r2 and experiences convection heat transfer and radiation exchange with the adjoining air and large surroundings, respectively. When electric current passes through the cable, thermal energy is generated within the cable at a volumetric rate q....
The heat that is conducted through a body must frequently be removed by other heat transfer processes. For example, the heat generated in an electronic device must be dissipated to the surroundings through convection by means of fins. Consider the one-dimensional aluminum fin (thickness t 3.0 mm, width 20 cm, length L) shown in Figure 1, that is exposed to a surrounding fluid at a temperature T. The conductivity of the aluminum fin (k) and coefficient of heat convection of...
(a) (iWhen is heat transfer through a fluid by conduction or by convection? For what case is the rate of heat transfer higher? How does the convection heat transfer coefficient differ from the thermal conductivity of a fluid? (ii) Explain the physical significance of Nusselt number (ii) By definition, discuss hydraulic diameter. Obtain an expression for hydraulic diameter of a circular tube of diameter, D (b) The local atmospheric pressure in Gboko, Benue State Nigeria (elevation 1610 m), is 834...
Can someone please help with these questions, thanks...
Chapter 14 1. Define heat. 2. (T/F) Heat is fundamentally different from 3. Define mechanical equivalent of heat 4. What is the difference between temperature and heat? 5. Why doe 6. Does the temperature of a substance change during a phase chang 7. Sketch Fig. 14.7 8. Can energy, explain. s a phase change require energy transfer? e? substance? evaporation and condensation happen below the boiling point of a What limitations does...
1)
2)
3)
PROJECT #1 (2.5 Marks): The heat that is conducted through a body must frequently be removed by other heat transter processes. For example, the heat generated in an electronic device must be dissipated to the surroundings through convection by means of fins. Consider the one-dimensional aluminum fin (thickness t 3.0 mm, width Z 20 cm, length L) shown in Figure 1, that is exposed to a surrounding fluid at a temperature 1. The conductivity of the aluminum...
A3. (a) According to Fourier's Law of thermal conduction, the heat flux through a solid is given by the solid's thermal conductivity k multiplied by the negative of the local temperature gradient. If the temperature in the solid is given by the function T(x, y, z)= 30e **(y2 + z), determine an expression for the heat flux through an internal surface with normal n=2i+j+2k [7 marks) (b) If f(t)=3sin ox and g(t)= 2 cos(@t++), determine the amplitude of the function...
a) Describe radiation and conduction as modes of heat transfer; what are the key differences between them? [41 b) You are thinking of installing an observation window to a walk in fridge wall. Compare the rate of heat transfer of the original fridge wall (no window) with the new one (with window). The original wall has an area of 8m2 and is composed of three layers in series, 0.3 cm steel, 3 cm cork for insulation and a 2.5 cm...
Assume two negative charges are placed close to each other, with one charge fixed and one charge free to move. The free charge will: O a accelerate away from the fixed charge. b. move closer to the fixed charge. Og C. orbit the fixed charge in a circular motion. d. remain stationary. Which of the following statements about insulating materials is correct? oa. Soaking paper in salt water decreases its insulation capability O b. The amount of current flowing in...
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