Consider two plates, A and B, that are each initially isothermal and each of thickness
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Introduction to Heat Transfer
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- 3. A lumped system with a volume of 0.003 m³ and a surface area of 0.08 m² is made of a material with density of 3800 kg/m³, thermal conductivity of 300 W/m K, and specific heat of 200 J/kg K. If the system is exposed to a convection environment with h = 60 W/m2 K, what is the approximate time it will take for this system to reach equilibrium with the environment? Express your answer in minutes.arrow_forwardA camper has a propane-powered refrigerator. The refrigerator consumes approximately 0.50 kgof propane per day. When propane is burned completely, it releases approximately 50. MJ/kg.The interior of the refrigerator is maintained at an average temperature of 2.0 °C, and theexterior temperature is 22 °C. Assume that the refrigerator has a surface area of 2.0 m2 and thatthe insulation has an R-value of 3.2 K · m2/W.(a) At what rate does heat flow into the refrigerator?(b) At what rate must the refrigerator remove heat from its interior?(c) How much energy is released per second from the propane combustion?(d) How much heat is delivered to the room?arrow_forwardThe rod A has a cross sectional area 2376 mm2, modulus of elasticity 68 Gpa and thermal expansion coefficient 0.000022 1 / C . The rod B has a cross sectional area 874 mm2, modulus of elasticity 176 Gpa and thermal expansion coefficient 0.000019 1 / C . When the temperature T1=24 C a 0.5 mm gap exists between the ends of the rods. If the temperature T2=182 C. Answer the following questions:arrow_forward
- The inside of a hollow cylinder is maintained at a temperature ??, and the outside is at a lower temperature, ??. The wall of the cylinder has a thermal conductivity ?. Ignoring end effects, show that the rate of energy conduction from the inner surface to the outer surface in the radial direction is ??/?? = 2??? [?? − ??/ ln(?/?)]The passenger section of a jet airliner is in the shape of a cylindrical tube with a length of 35.0 m and an inner radius of 2.50 m. Its walls are lined with an insulating material 6.00cm in thickness and having a thermal conductivity of 4.00 × 10−5cal/s ⋅ cm ⋅ °C. A heater must maintain the interior temperature at 25.0°C while the outside temperature is −35.0°C. What power must be supplied to the heater?arrow_forward5 An ice chest is constructed of Styrofoam [k = 0.033 W/m · ◦C] with inside dimensions of 25 by 40 by 100 cm. The wall thickness is 5.0 cm. The outside of the chest is exposed to air at 25◦C with h = 10 W/m2 · ◦C. If the chest is completely filled with ice, calculate the time for the ice to completely melt. State your assumptions. The enthalpy of fusion for water is 330 kJ/kg.arrow_forwardIn many manufacturing plants, individuals areoften working around high-temperature surfaces.Exposed hot surfaces that can cause thermal burns on humanskin are considered hazards in the workplace. Metallic surfacesabove 70° C can instantly damage skin that touches them.Consider an AISI 1010 carbon steel strip (? = 7832 kg/ m 3 )2 mm thick and 3 cm wide that is conveyed into a chamber tobe cooled at a constant speed of 1 m/s. The steel strip entersthe cooling chamber at 597° C. Determine the rate at whichheat needs to be removed so that the steel strip exits the chamberat 47° C . Discuss how the conveyance speed can affect therequired rate of heat removal.arrow_forward
- 2.34 Show that the temperature distribution in a sphere of radius . made of a homogeneous material in which energy is released at a uniform rate per unit volume , isarrow_forwardHow does the concept of available energy apply to the analysis and design of mechanical systems in the field of mechanical engineering?arrow_forward10 hot rods (L = 5 m and d = 2 cm) are buried in the ground parallel to each other each rod is 10 cm apart and at a depth 3 m from the ground surface. The thermal conductivity of the soil is 0.6 W/m K. If the surface temperature of the rods and the ground are 600 K and 30 °C, respectively. Draw the figure and determine the rate of heat transfer from the fuel rods to the atmosphere through the soilarrow_forward
- Draw the PV and TS diagram: Process 1-2: constant pressure heat rejection Process 2-3: polytropic expansion Process 3-1: isothermal heat rejectionarrow_forwardExplain the causes of Irreversibility. Thermodynamics subject. -Mixing of dissimilar gases or liquids. -Mixing of identical fluids initially at different pressures and temperaturesarrow_forwardQuestion 2a) Give the Stefan Boltzman equation and define each term.[4]b) A electric room heater (radiator) element is 25 cm long and 4 cm in diameter. The element dissipates heat to the surroundings at 1500 W mainly by radiation, the surrounding temperature being 15°C. Determine the equilibrium temperature of the element surface.[4]c) A composite cylinder consists of 10 cm radius steel pipe of 25 mm thickness over which two layers of insulation 30 mm and 35 mm are laid. The conductivities are 25 W/mK, 0.25 W/mK and 0.65 W/mK. The inside is exposed to convection at 300°C with h 65 W/m2K.The outside is exposed to air at 30°C with h 15 W/m2K. Determinei. the heat loss/m,the interface temperatures.ii. The overall heat transfer coefficient.[4][4][2]arrow_forward
- Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning