2.The vertical flat wall of the combustion chamber of a furnace isconstructed with a layer of firebrick 200 mm thick, a layer of insulation100 mm thick and a mild steel plate 10 mm thick on the outside. Theinner surface of the firebrick is at a temperature of 815°C and the airtemperature outside the furnace is 21 °C. To estimate the heat lossfrom the furnace, a hole is drilled through the plate and insulation sothat the temperature at the junction of the firebrick and insulation canbe determined. This is found to be 730°C.Estimate:(i) the rate of heat loss per m² of wall surface.(ii)the heat transfer coefficient from the outer surface of the steel tothe surrounding air.The thermal conductivities of the materials used are:Firebrick 1.0, insulating material 0.07, and steel 45W/mK.Answer: 425 W/m² 4.2 W/m²K

Heat Transfer Problem SolutionThis workings provides a comprehensive explanation of the heat…

Answered: 2. The vertical flat wall of the…

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.

Chapter7: Forced Convection Inside Tubes And Ducts

Section: Chapter Questions

Problem 7.53P

See similar textbooks

Similar questions

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.
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
The heat transfer coefficient for a gas flowing over a thin float plate 3-m long and 0.3-m wide varies with distance from the leading edge according to hc(x)=10x1/4Wm2K If the plate temperature is 170C and the gas temperature is 30C, calculate (a) the average heat transfer coefficient, (b) the rate of heat transfer between the plate and the gas, and (c) the local heat flux 2 m from the leading edge. Problem 1.18
An electrical transmission line of 1.2-cm diameter carries a current of 200 amps and has a resistance of 310-4 ohm per meter of length. If the air around this line is at v, determine the surface temperature on a windy day, assuming a wind blows across the line at 33 km/h.
The main body of plenum is a steel vessel of diameter 0.1meters has two semicircle domed ends. During operation is will contain mix of fuel and air at approximately 250OC. The wall of the vessel is 0.03meters thick and the plenum is 0.45meters long. Estimate the rate of heat loss from the vessel when the outside air temperature is 45OC. The thermal conductivity of steel is 45 W/m K and the surface heat transfer coefficient on the air side is 8 W/m2 . On the inside it is 65W/m2 . If it was possible to clad the plenum calculate the reduction in the rate of heat loss. Assume the lagging would be 5mm thick and has a thermal conductivity of 0.05 W/m.
A double window called thermopane is one in which two layers of glass are used separated by a layer o dry stagnant air: In a given window, each of the glass layers is 6.35 mm thick separated by a 6.35 mm space of stagnant air. The thermal conductivity of the glass is 0.869 W/m K and that of air is 0.026 over the temperature range used. For temperature drop of 27.8 K over the system, calculate the heat loss for a window 0.914 m 1.83 m.
Thermal jackets are typically put on cryogenicstorage tanks to minimize the heat transfer gainsfrom the surroundings. Consider a cylindercontainer that is 1.5 m long made from steel (k = 750W/m.K) with an inner diameter of 0.5 m and outerdiameter of 0.7 m. If the liquefied natural gas (LNG)inside the cylinder is maintained at 90 K, ambientconditions are Tamb = 20 °C, h = 7 W/m2.K. What isthe required thermal jacket thickness to maintainthe outer temperature of that jacket of 15 °C? (Takea thermal conductivity of the insulation to be kins =0.015 W/m.K). Image credit: Okorder. Image forillustrative purposes only.
A heater coil is completely immersed in an oil bath that is insulated on all sides except for the top where the oil is in direct contact with the surrounding air that is maintained at a constant temperature, Oair. At t=0s, the coil is switched on and provides in watts of electrical power to the oil which has a thermal mass of moil and an initial temperature of Oinit-oil. The temperature of the oil is denoted by oil and the thermal resistance between the oil and air is Roil-air- a) Draw a schematic of the system clearly labeling the (assumed) directions of the heat transfer rates and the temperature at every node. b) Derive the governing differential equation for the temperature of the oil, oil- c) Where does Oinit-oil appear in the system schematic and how does it affect the governing equations? d) Derive an expression for the steady-state temperature of the oil as a function of the various system parameters.
A cylindrical storage tank with diameter of 4m and a length of 10 m will hold a fluid whose temperature must be maintained at 347k. in order to size the heater required for the tank the following worst-case scenario is considered: Ambient temperature=-20 wind speed=20m/s tank wall temperature=347k what size (kW) heater will be needed?
Chips of width L _ 15 mm on a side are mounted to a substrate that is installed in an enclosurewhose walls and air are maintained at a temperature of Tsur=T∞=25oC. The chips have an emissivity ofε=0.60 and a maximum allowable temperature of Ts=85oC.(a) If heat is rejected from the chips by radiation and natural convection, what is the maximum operatingpower of each chip? The convection coefficient may be approximated as h=11.7 W/m2K.(b) If a fan is used to maintain airflow through the enclosure and heat transfer is by only forcedconvection, with h=250 W/m2K, what is the maximum operating power?
The free convection heat transfer coefficient on a thin hot vertical plate suspended in still air can be determined from observations of the change in plate temperature with time as it cools. Assuming the plate is isothermal and radiation exchange with its surroundings is negligible, evaluate the convection coefficient at the instant of time when the plate temperature is Tplate = 277 °C and the change in plate temperature with time (dT/dt) is −0.022 K/s. The ambient air temperature is Tinf = 28°C and the plate measures 0.7 × 0.7 m with a mass of 5.56 kg and a specific heat of 2,780 J/kg · K.
Thermodynamics problem. A membrane type electrical heater of 20,000 w/m? capacity is sandwiched between an Insulation of 25 mm thickness with thermal conductivity of 0.029 W/m-K and a metal plate with k = 12.6 W/m-K of thickness 15 mm. The convection coefficient is 150 W/m2-K. The surroundings are at 5°C. Determine the surface temperature of the heater and the flow on either side.

SEE MORE QUESTIONS

Recommended textbooks for you

Principles of Heat Transfer (Activate Learning wi…

Mechanical Engineering

ISBN:

9781305387102

Author:

Kreith, Frank; Manglik, Raj M.

Publisher:

Cengage Learning