Q5: The piston cylinder device (radius =10 cm) contains a liquid with a pressure 100 kpa and temperature of 20 ° C and has a liquid convection heat coefficient =93 W m K. Connect its fixed side to a cubic piece of aluminum (side length 15 cm) with a thermal conductivity coefficient of aluminum = 239 W m K. At the bottom of the aluminum piece there is a heat source with a temperature of 150 ° C, noting that the heat source is located in a vacuum chamber. Radiation thermal resistance = 3.17 K/ W. Calculate the change in piston height during 1 sec. if you know that there is no change in the internal energy of the piston cylinder device. Note 1KWatt 1KJ/s

Q5: The piston cylinder device (radius =10 cm) contains a liquid with a pressure 100 kpa and temperature of 20 ° C and has a liquid convection heat coefficient =93 W m K. Connect its fixed side to a cubic piece of aluminum (side length 15 cm) with a thermal conductivity coefficient of aluminum = 239 W m K. At the bottom of the aluminum piece there is a heat source with a temperature of 150 ° C, noting that the heat source is located in a vacuum chamber. Radiation thermal resistance = 3.17 K/ W. Calculate the change in piston height during 1 sec. if you know that there is no change in the internal energy of the piston cylinder device. Note 1KWatt 1KJ/s

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 2.15P: 2.15 Suppose that a pipe carrying a hot fluid with an external temperature of and outer radius is...

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2.2 A small dam, which is idealized by a large slab 1.2 m thick, is to be completely poured in a short Period of time. The hydration of the concrete results in the equivalent of a distributed source of constant strength of 100 W/m3. If both dam surfaces are at 16°C, determine the maximum temperature to which the concrete will be subjected, assuming steady-state conditions. The thermal conductivity of the wet concrete can be taken as 0.84 W/m K.
1.10 A heat flux meter at the outer (cold) wall of a concrete building indicates that the heat loss through a wall of 10-cm thickness is . If a thermocouple at the inner surface of the wall indicates a temperature of 22°C while another at the outer surface shows 6°C, calculate the thermal conductivity of the concrete and compare your result with the value in Appendix 2, Table 11.
2.15 Suppose that a pipe carrying a hot fluid with an external temperature of and outer radius is to be insulated with an insulation material of thermal conductivity k and outer radius . Show that if the convection heat transfer coefficient on the outside of the insulation is and the environmental temperature is , the addition of insulation actually increases the rate of heat loss if , and the maximum heat loss occurs when . This radius, is often called the critical radius.
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
How long should it take to boil an egg? Model the egg as a sphere with radius of 2.3 cm that has properties similar to water with a density of = 1000 kg/m3 and thermal conductivity of k = 0.606 Watts/(mC) and specific heat of c = 4182 J/(kg C). Suppose that an egg is fully cooked when the temperature at the center reaches 70 C. Initially the egg is taken out of the fridge at 4 C and placed in the boiling water at 100 C. Since the egg shell is very thin assume that it quickly reaches a temperature of 100 C. The protein in the egg effectively immobilizes the water so the heat conduction is purely conduction (no convection). Plot the temperature of the egg over time and use the data tooltip in MATLAB to make your conclusion on the time it takes to cook the egg in minutes.
8.9 One end of a 9-in long × 7-in diameter copper bar is heated to 59.4°F, the far end of the bar is held at 23°C. If the sides of the bar are covered with thermal insulation, what is the rate of heat transfer? 8.11 When the far end of the copper bar in Prob. 8.9 has a 30-ft2 cooling fin attached to the end of the bar and is cooled by air convection, the temperature of the fin rises to t °F. If the temperature of the air is 23°F and the coefficient of heat transfer of the surface is 0.22 BTU/h, what is the value of t?
Example 4: A wall has the following specifications as shown in figure below: Height = 3 m. Width = 5m k (bricks)=0.72 W/m · °C k (plaster) = 0.22 W/m · °C k (foam) =0.026 W/m · °C. The indoor and the outdoor temperatures are 20°C and -10°C. convection heat transfer coefficients on the inner and the outer sides are h1 = 10 W/m2·°C and h2 = 25 W/m2· °C, respectively. Determine the rate of heat transfer through the wall.
A 10-cm diameter pipe is covered by 2 layers of lagging. The insidelayer is 4 cm thick and has a coefficient of thermal conductivity of 0.08W/m-K. The outside layer is 3cm thick and has a coefficient of thermalconductivity of 0.15 W/m-K. The steam main conveys steam apressure of 1.7 MPa with 25 C superheat. The outside temperature ofthe lagging is 27 C. If the steam main is 30 m long, determine theinterface temperature of the lagging and overall coefficient of heattransfer based on outside area.
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: the resistance(R) for the Aluminium near the outer thermal layer in K/W to 8 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: the resistance(R) for the Aluminium near the outer thermal layer in K/W to 8 decimal places. the resistance(R) for the Aluminium near the inner thermal layer in K/W to 8 decimal places.
A single-cylinder air-cooled lawn mower engine operates under steady conditions. The cylinder temperature cannot exceed 300 ⁰C. To cool the engine, annular fins are placed around the cylinder. The fins are 0.3 cm thick and are 2 cm long from base to tip. The fins are made of cast iron (k = 52 W/mK). The outside diameter of the engine cylinder at the base of the fin is 0.3 m. Assume that the engine operates in 30 ⁰C air and that the heat transfer coefficient on the sides and tip of the fin is 12 Wm^-2K^-1. Determine the number of fins needed to cool a 3 kW engine to the given temperature if the engine has an efficiency of 30 % and 50 % of the total heat given off by the engine actually is dissipated through the fins ?