QUESTION 1 A domestic retriger ator with Inner dimensions of 0,7 m by 0.7 m at the base and height 1 m was designed to maintain a set temperature of 6 "C. The bodies consist of two 10-mm-thick layers of Aluminium (k - 225 Wimk) separated by a 30 mm polyurethane insulation (k-0.028 Wimk). If the average convection heNat transfer coefficlent at the inner and outer surfaces are 11.6 Wm?k and 14.5 W/m2k respectively, calculate: the resistance(R) for the Aluminium near the inner thermal layer in K/W to 8 decimal places. QUESTION 2 A domestic retrigerator with Inner dimeensions of 0.7 m by 0.7 m at the base and height 1 m was designed to maintain a set temperature of 6 'C. The bodies consist of two 10-mm-thick layers of Aluminium (k - 225 Wimk) separated by a 30 mm polyurethane insulation (k-0.028 Wimk). If the average convection heat transter coeficient at the Inner and outer surfaces are 11.6 Wim2K and 14.5 W/m2K respectively, calculate: the resistance(R) for the Aluminium near the outer thermal layor in K/W to 8 decimal places.

QUESTION 1 A domestic retriger ator with Inner dimensions of 0,7 m by 0.7 m at the base and height 1 m was designed to maintain a set temperature of 6 "C. The bodies consist of two 10-mm-thick layers of Aluminium (k - 225 Wimk) separated by a 30 mm polyurethane insulation (k-0.028 Wimk). If the average convection heNat transfer coefficlent at the inner and outer surfaces are 11.6 Wm?k and 14.5 W/m2k respectively, calculate: the resistance(R) for the Aluminium near the inner thermal layer in K/W to 8 decimal places. QUESTION 2 A domestic retrigerator with Inner dimeensions of 0.7 m by 0.7 m at the base and height 1 m was designed to maintain a set temperature of 6 'C. The bodies consist of two 10-mm-thick layers of Aluminium (k - 225 Wimk) separated by a 30 mm polyurethane insulation (k-0.028 Wimk). If the average convection heat transter coeficient at the Inner and outer surfaces are 11.6 Wim2K and 14.5 W/m2K respectively, calculate: the resistance(R) for the Aluminium near the outer thermal layor in K/W to 8 decimal places.

Principles of Heat Transfer (Activate Learning with these NEW titles from Engineering!)

8th Edition

ISBN:9781305387102

Author:Kreith, Frank; Manglik, Raj M.

Publisher:Kreith, Frank; Manglik, Raj M.

Chapter2: Steady Heat Conduction

Section: Chapter Questions

Problem 2.30P: 2.30 An electrical heater capable of generating 10,000 W is to be designed. The heating element is...

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3.10 A spherical shell satellite (3-m-OD, 1.25-cm-thick stainless steel walls) re-enters the atmosphere from outer space. If its original temperature is 38°C, the effective average temperature of the atmosphere is 1093°C, and the effective heat transfer coefficient is , estimate the temperature of the shell after reentry, assuming the time of reentry is 10 min and the interior of the shell is evacuated.
2.30 An electrical heater capable of generating 10,000 W is to be designed. The heating element is to be a stainless steel wire having an electrical resistivity of ohm-centimeter. The operating temperature of the stainless steel is to be no more than 1260°C. The heat transfer coefficient at the outer surface is expected to be no less than in a medium whose maximum temperature is 93°C. A transformer capable of delivering current at 9 and 12 V is available. Determine a suitable size for the wire, the current required, and discuss what effect a reduction in the heat transfer coefficient would have. (Hint: Demonstrate first that the temperature drop between the center and the surface of the wire is independent of the wire diameter, and determine its value.)
The air-conditioning system in a Chevrolet van for use in desert climates is to be sized. The system is to maintain an interior temperature of 20C when the van travels at 100 km/h through dry air at 30C at night. If the top of the van is idealized as a flat plate 6 m long and 2 m wide and the sides as flat plates 3 m tall and 6 m long, estimate the rate at which heat must be removed from the interior to maintain the specified
2.42 A circumferential fin of rectangular cross section, 3.7-cm OD and 0.3 cm thick, surrounds a 2.5-cm- diameter tube as shown below. The fin is constructed of mild steel. Air blowing over the fin produces a heat transfer coefficient of K. If the temperatures of the base of the fin and the air are and , respectively, calculate the heat transfer rate from the fin.
1.4 To measure thermal conductivity, two similar 1-cm-thick specimens are placed in the apparatus shown in the accompanying sketch. Electric current is supplied to the guard heater, and a wattmeter shows that the power dissipation is 10 W. Thermocouples attached to the warmer and to the cooler surfaces show temperatures of 322 and 300 K, respectively. Calculate the thermal conductivity of the material at the mean temperature in W/m K. Problem 1.4
2.7 A very thin silicon chip is bonded to a 6-mm thick aluminum substrate by a 0.02-mm thick epoxy glue. Both surfaces of this chip-aluminum system are cooled by air at , where the convective heat transfer coefficient of air flow is . If the heat dissipation per unit area from the chip is under steady-state conditions, draw the thermal circuit for the system and determine the operating temperature of the chip.
2.51 Determine by means of a flux plot the temperatures and heat flow per unit depth in the ribbed insulation shown in the accompanying sketch.
3.14 A thin-wall cylindrical vessel (1 m in diameter) is filled to a depth of 1.2 m with water at an initial temperature of 15°C. The water is well stirred by a mechanical agitator. Estimate the time required to heat the water to 50°C if the tank is suddenly immersed in oil at 105°C. The overall heat transfer coefficient between the oil and the water is , and the effective heat transfer surface is .
A domestic refrigerator with inner dimensions of 0,7 m by 0,7 m at the base and height 1m was designed to maintain a set temperature of 6 degrees Celsius. The bodies consist of two 10 mm thick layers of Aluminum (k=225W/mK) separated by a 30 mm polyurethane insulation (k=0,028W/mK). If the average convection heat transfer coefficient at the inner and outer surfaces are 116W/m²K and 14,5W/m²K respectively. Calculate : 1)The individual resistance (R) for each thermal layer, as well as for the refrigerator 2)The steady rate of heat transfer from the interior to maintain the specified temperature in the kitchen at 25 degrees Celsius 3)The outer surface temperature of the Aluminum 4)Sketch the sectional view of the refrigerator showing thermal circuit
Can u continue the question 5 to 7 5. Calculate the change in heat energy of the submarine’s outer haul, when it descends from the surface to a depth of 3,500m (with an average temperature of 20°C). 6. Calculate the power of the submarine’s electrical heater needed, to maintain the interior of outer hull at 30°C. The exterior of outer hull is 10°C. (Assume heat of the submarine is only lost across the outer hull) 7. Suggest aerospace applications of ballast.
A domestic refrigerator with inner dimensions of 0,7 m by 0,7 m at the base and height 1m was designed to maintain a set temperature of 6 degrees Celsius. The bodies consist of two 10 mm thick layers of Aluminum (k=225 W/mK) separated by a 30 mm polyurethane insulation (k=0,028 W/mK). If the convection heat transfer coefficient at the inner and outer surfaces are 11,6 W/m²K and 14,5 W/m²K respectively, calculate the outer surface temperature of Aluminum in degrees Celsius to 2 decimal places. 2)calculate the resistance (R) for the insulation layer in K/W to 4 decimal places. 3)calculate the steady rate of heat transfer from the interior to maintain the specified temperature in the kitchen at 25 degrees Celsius in W to 2 decimal places. 4)calculate the total resistance (R) for the refrigerator in K/W to 4 decimal places
A domestic refrigerator with inner dimensions of 0.7 m by 0.7 m at the base and height 1 m was designed to maintain a set temperature of 6 ˚C. The bodies consist of two 10-mm-thick layers of Aluminium (k = 225 W/mK) separated by a 30 mm polyurethane insulation (k=0.028 W/mK). If the average convection heat transfer coefficient at the inner and outer surfaces are 11.6 W/m2K and 14.5 W/m2K respectively, calculate: Total inner surace area in m2 to 2 decimal places.