16. A 12 cm diameter long bar initially at a uniform temperature of 40°C is placed in a medium at 650°C with a convective co efficient of 22 W/m*K calculate the time required for the bar to reach255°C. Take k = 20W/mK, p = 580 kg/m' and e = 1050 J/kg K. Given : Unsteady state D- 12 cm = 0.12 m R=0.06 m T.- 40 + 273 = 313 K T.- 650 + 273 = 923 K T- 255 + 273 -528s K h- 22 W/m°K k= 20 W/mK p= 580 Kg'm' c = 1050 J/kg K Find: Time required to reach 255°C ()

16. A 12 cm diameter long bar initially at a uniform temperature of 40°C is placed in a medium at 650°C with a convective co efficient of 22 W/m*K calculate the time required for the bar to reach255°C. Take k = 20W/mK, p = 580 kg/m' and e = 1050 J/kg K. Given : Unsteady state D- 12 cm = 0.12 m R=0.06 m T.- 40 + 273 = 313 K T.- 650 + 273 = 923 K T- 255 + 273 -528s K h- 22 W/m°K k= 20 W/mK p= 580 Kg'm' c = 1050 J/kg K Find: Time required to reach 255°C ()

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.

Chapter8: Natural Convection

Section: Chapter Questions

Problem 8.53P

See similar textbooks

Similar questions

Q4. Two long rods of the same diameter, one of brass(k= 85 W/mK) and the other of copper (k=375 W/mK) have one of their ends inserted in a furnace and the other ends exposed to the same atmosphere. At a distance of 105mm away from the furnace, the temperature of the brass rod is 120' C. Find the distance from the furnace in which the copper rod have the same temperature.
Ex1. A piece of chromium steel of length 7.4cm (density=8780kg/m³ ; k = 50w/mK and specific heat cp = 440j/kgK) with mass 1.27kg is rolled into a solid cylinder and heated to a temperature of 600°C and quenched in oil at 36°c. Show that the lumped capacitance system analysis is applicable and find the temperature of the cylinder after 4min. What is the total heat transfer during this period? You may take the convective heat transfer coefficient between the oil and cylinder at 280w/m2k.
A slab of iron with temperature, Tz=48 deg C is used to heat a flat glass plate that has an initial temperature of Tgi=18 deg C. Assuming no heat is lost to the environment, and the masses are m-0.49 kg for the slab and m;= 310 g for the plate, what is the amount of heat transferred when the two have reached equal temperature? Assume cF0.11 kcal/kg-deg C for iron and cg=0.20 kcal/kg- deg C for glass. Select the correct response: 32 kcal 53 kcal 860 cal 320 kcal
A solid hemisphere of radius 5 cm to be cooled in air (at 20 o C, h=10 W/m 2 .K) from 200 oC to center of 150 oC, assume following sphere properties ρ=8500kg/m3, k=20W/m.K , C=400 J/kg.Ka. List assumptions and justify selected method of solution b. How long does it take to cool the hemisphere? c. What is the temperature of the surface at end of cooling?
Needle ball bearings, D=5-mm, H=26-mm, are heated up to 1200 K in a heat treatment furnace where the micro-structure is transformed from pearlite to austenite. As soon as taken out of the furnace, they are quenched in water having T=286 K and h=174 W/m2K to transform the micro- structure from austenite to martensite. Find the time required for cooling the bearings to T=326 K. Assume the bearings are perfectly cylindrical and made of AISI 347 Steel. H
Conduction 1. A thermodynamic analysis of a proposed Brayton cycle gas turbine yields P= 5 MW of net power production. The compressor, at an average temperature of T. = 400°C, is driven by the turbine at an average temperature of T₁ = 1000°C by way of an L = 1m-long, d= 70mm - diameter shaft of thermal conductivity k = 40 W/m K. Compressor min T Combustion chamber Shaft L Turbine Th out (a) Compare the steady-state conduction rate through the shaft connecting the hot turbine to the warm compressor to the net power predicted by the thermodynamics- based analysis. (b) A research team proposes to scale down the gas turbine of part (a), keeping all dimensions in the same proportions. The team assumes that the same hot and cold temperatures exist as in part (a) and that the net power output of the gas turbine is proportional to the overall volume of the device. Plot the ratio of the conduction through the shaft to the net power output of the turbine over the range 0.005 m s Ls 1 m. Is a…
A long rectangular steel bar (10cm x 5 cm) is kept in an environment such that two 10cm faces are maintained at 30 ⁰C, one 5cm face is at 30 ⁰C and other is at 130 ⁰C. The steady state temperature along the center line of the bar is ?
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 1. 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
2000kg cast iron housing at 450 degree Celsius is quenched in 5000kg of water at 15 degree C. What is the amount of heat transferred to water, use specific heat of water to be 4.18 kJ/kg.K and specific heat of iron to be 0.42 kJ/kg.K
Calculate the nodal temperatures of four elements in the below Fig. 2. How much heat input is required to maintain T1 = 200°C?. Consider the following A = 1 m², L = 1 m, k = 10 W/m/°C :-200W T, 13 T. T, T. 200 °C 1 3 4 Q, = 500W Ø, = 0 O, = 0 Fig. 2 2.
3.4 Estimate the rate of heat loss due to radiation from a covered pot of water at 95 ° C. How does this compare with the 60 W that is lost due only to convection and conduction losses? What amount of energy input would be needed to maintain the water at its boiling point for 30 minutes? The polished stainless steel pot is cylindrical, 20 cm in diameter and 14 cm high, with a tight-fitting flat cover. The air temperature in the kitchen is about 25 ° C. State any assumptions you make in deriving your estimates
Read the question carefully and give me right solution according to the question. Note: Don't copy other expert solution. I have other website solution. A metallic ball of radius ro = 5 mm, is initially in equilibrium at 400 C in a furnace. It is suddenly dropped to water at 20 C hw 10814 W/m2 K, . The properties of the sphere are density= 3000 kg/m3, k = 20 W/m_ K, c = 1000 J/kg K, and α= 6.66E-6 m2/s. Calculate the time required for the center of the sphere to cool to 50 C.