Homework Answers
Consider the base plate of a 1200-W household iron that has a thickness of L =...
Consider the base plate of a 1200-W household iron that has a thickness of L = 0.5-cm, base area of A= 300-cm', and thermal conductivity of k = 15-W/m-C". The inner surface of the base plate is subjected to a uniform heat flux generated by the resistance heaters inside, and the outer surface losses heat to the surroundings at T = 20°C by convection. Taking the convection heat transfer coefficient to be h = 80-W/m--°C obtain an expression for the...
Consider the base plate of a 800-W household iron hav- ing a thickness of L =...
Consider the base plate of a 800-W household iron hav- ing a thickness of L = 0.6 cm, base area of A = 160 cm², and thermal conductivity of k = 20 W/m - °C. The inner surface of the base plate is subjected to uniform heat flux generated by the resistance heaters inside. When steady operating conditions are reached the outer surface temperature of the plate is mea- sured to be 85°C. Disregarding any heat loss through the upper...
QUESTION FOUR Consider the base plate of an 900-W household iron with a thickness of L-0.6...
QUESTION FOUR Consider the base plate of an 900-W household iron with a thickness of L-0.6 cm, base area of A-160 cm2, and the thermal conductivity of k-60 W/m.K. The inner surface of the base plate is subjected to uniform heat flux generated by the resistance heaters inside. When stea dy operating itions are reached, the outer surface temperature of the plate is measured to be 112 C. Disregarding any heat loss through the upper part of the iron, (a)...
13.15 The base plate of an ironi (provided by resistance over a base plate cros plate...
13.15 The base plate of an ironi (provided by resistance over a base plate cros plate of an iron is 0.6 cm thick. The plate is subjected to 100 W of power ded by resistance heaters inside the iron, as shown in Figure P13-15). base plate cross-sectional area of 250 cm, resulting in a uniform flux rated on the inside surface. The thermal conductivity of the metal base generated on th is k = 20 W/m- C. The outside ambient...
Consider a 1000-W iron whose base plate is made of 0.5-cm-thick aluminum alloy 2024-T6 (0-2770 kg/m...
Consider a 1000-W iron whose base plate is made of 0.5-cm-thick aluminum alloy 2024-T6 (0-2770 kg/m and Cp=875 J/kg:"C). The base plate has a surface area of 0.03 m2 Initially, the iron is in thermal equilibrium with the ambient air at 22°C. Assuming 90 percent of the heat generated in the resistance wires is transferred to the plate, determine the minimum time needed for the plate temperature to reach 220°C The minimum time needed for the plate temperature to reach...
An aluminum plate with a thickness of L=5 mm is mounted in a horizontal position, and...
An aluminum plate with a thickness of L=5 mm is mounted in a horizontal position, and its bottom surface is well insulated. A special, thin coating (with emissivity and solar absorptivity of 0.25) is applied to the top surface. The density ρ and specific heat c of aluminum are known to be 2700 kg/m3 and 900 J/kg · K, respectively. Consider conditions for which the plate is initially at a temperature of ??????=25 °C and its top surface is suddenly...
A 50 mm thick steel plate (AISI347) has a uniform heat flux applied to its bottom...
A 50 mm thick steel plate (AISI347) has a uniform heat flux
applied to its bottom surface by a heater. The heater is in contact
with the steel plate, and the interface between the heater and
steel has a contact resistance of 2.0 x 10-4
m2*K/W. The top surface of the plate is exposed to
surrounding air (T = 20oC, h = 10 W/m2*K) and
exchanges radiation with surroundings at Tsur =
10oC. The emissivity of the plate is 0.85....
To defrost ice accumulated on the outer surface of an automobile windshield, warm air is blown...
To defrost ice accumulated on the outer surface of an automobile windshield, warm air is blown over the inner surface of the windshield. Consider an automobile windshield with thickness of 5 mm and thermal conductivity of 1.4 W/m K. The outside ambient temperature is -10 C and the convection coefficient is 200 W/m2-K, while the ambient temperature inside the automobile is 25 C. Determine the value of the convection heat transfer coefficient for the warm air blowing over the inner...
1. Consider an opaque, horizontal square plate (Im by 1m) with an electrical heater on its backside. The front side is exposed to ambient quiescent air that is at 20° C, solar irradiation (from...
1. Consider an opaque, horizontal square plate (Im by 1m) with an electrical heater on its backside. The front side is exposed to ambient quiescent air that is at 20° C, solar irradiation (from sun at 5800° K) of 600 W/m2, and an effective sky temperature of -40° C. The plate surface temperature is kept at Ts 60 C (at steady state condition). Calculate natural convection heat transfer coefficient from the plate. (10 points) What is the electrical power (W/m2)...
QUESTION 5 A 12-m-long and 11-mm-inner-diameter pipe made of commercial steel is used to heat a...
QUESTION 5 A 12-m-long and 11-mm-inner-diameter pipe made of commercial steel is used to heat a liquid in an industrial process. The liquid enters the pipe with T; = 20°C, V=0.8 m/s. A uniform heat flux is maintained by an electric resistance heater wrapped around the outer surface of the pipe, so that the fluid exits at 60°C. Assuming fully developed flow and taking the average fluid properties to be p = 992.1 kg/m2, k = 0.631 W/m-°C, Cp =...
Consider the base plate of a 1200-W household iron that has a thickness of L = 0.5-cm, base area of A= 300-cm', and thermal conductivity of k = 15-W/m-C". The inner surface of the base plate is subjected to a uniform heat flux generated by the resistance heaters inside, and the outer surface losses heat to the surroundings at T = 20°C by convection. Taking the convection heat transfer coefficient to be h = 80-W/m--°C obtain an expression for the...
Consider the base plate of a 800-W household iron hav- ing a thickness of L = 0.6 cm, base area of A = 160 cm², and thermal conductivity of k = 20 W/m - °C. The inner surface of the base plate is subjected to uniform heat flux generated by the resistance heaters inside. When steady operating conditions are reached the outer surface temperature of the plate is mea- sured to be 85°C. Disregarding any heat loss through the upper...
QUESTION FOUR Consider the base plate of an 900-W household iron with a thickness of L-0.6 cm, base area of A-160 cm2, and the thermal conductivity of k-60 W/m.K. The inner surface of the base plate is subjected to uniform heat flux generated by the resistance heaters inside. When stea dy operating itions are reached, the outer surface temperature of the plate is measured to be 112 C. Disregarding any heat loss through the upper part of the iron, (a)...
13.15 The base plate of an ironi (provided by resistance over a base plate cros plate of an iron is 0.6 cm thick. The plate is subjected to 100 W of power ded by resistance heaters inside the iron, as shown in Figure P13-15). base plate cross-sectional area of 250 cm, resulting in a uniform flux rated on the inside surface. The thermal conductivity of the metal base generated on th is k = 20 W/m- C. The outside ambient...
Consider a 1000-W iron whose base plate is made of 0.5-cm-thick aluminum alloy 2024-T6 (0-2770 kg/m and Cp=875 J/kg:"C). The base plate has a surface area of 0.03 m2 Initially, the iron is in thermal equilibrium with the ambient air at 22°C. Assuming 90 percent of the heat generated in the resistance wires is transferred to the plate, determine the minimum time needed for the plate temperature to reach 220°C The minimum time needed for the plate temperature to reach...
A 50 mm thick steel plate (AISI347) has a uniform heat flux
applied to its bottom surface by a heater. The heater is in contact
with the steel plate, and the interface between the heater and
steel has a contact resistance of 2.0 x 10-4
m2*K/W. The top surface of the plate is exposed to
surrounding air (T = 20oC, h = 10 W/m2*K) and
exchanges radiation with surroundings at Tsur =
10oC. The emissivity of the plate is 0.85....
To defrost ice accumulated on the outer surface of an automobile windshield, warm air is blown over the inner surface of the windshield. Consider an automobile windshield with thickness of 5 mm and thermal conductivity of 1.4 W/m K. The outside ambient temperature is -10 C and the convection coefficient is 200 W/m2-K, while the ambient temperature inside the automobile is 25 C. Determine the value of the convection heat transfer coefficient for the warm air blowing over the inner...
1. Consider an opaque, horizontal square plate (Im by 1m) with an electrical heater on its backside. The front side is exposed to ambient quiescent air that is at 20° C, solar irradiation (from sun at 5800° K) of 600 W/m2, and an effective sky temperature of -40° C. The plate surface temperature is kept at Ts 60 C (at steady state condition). Calculate natural convection heat transfer coefficient from the plate. (10 points) What is the electrical power (W/m2)...
QUESTION 5 A 12-m-long and 11-mm-inner-diameter pipe made of commercial steel is used to heat a liquid in an industrial process. The liquid enters the pipe with T; = 20°C, V=0.8 m/s. A uniform heat flux is maintained by an electric resistance heater wrapped around the outer surface of the pipe, so that the fluid exits at 60°C. Assuming fully developed flow and taking the average fluid properties to be p = 992.1 kg/m2, k = 0.631 W/m-°C, Cp =...
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