Example:.A steel ball [c-0.46 kJ/kg C, k-35 W/m. C] 5.0 cm in diameter andinitially at a uniform temperature of 450°C is suddenly placed in acontrolled environment in which the temperature is maintained at 100°C.The convection heat-transfer coefficient is 10 W/m². C. Calculate thetime required for the ball to attain a temperature of 150°C.Solution:We anticipate that the lumped-capacity method will apply because of the low value ofh and high value of k.We can check by using Equation (3.9):hLcB₁ =k3Lc =T 0.025=-== 0.00833A₂4mr² 33hle10-0.00833B₁ === 0.0023 < 0.1k35The lumped system capacitance method is valid and can used. Therefore, may can useequation 3.4:t=pvc In0₁hAs 092HEAT TRANSFERt = pvc Inpvc Ti-ToohAsT-TooT = 150 °C, p = 7800 kg/m³.Too-100 °C, h=10 w/m².C.T₁-450 °C, c-460 J/kg. "C.pvc InTi-Toot =hAs T-Toot=Pr³cIn Ti-Tooh4r² T-Tt= 1In Ti-Topre3h T-TV-==7800+0.025-460In3.10450-100150-100= 5818.3 s= 1.62 h6

Answered: Image /qna-images/answer/c161d202-9fb3-42a2-a865-a942ae17c6ba.jpg

. A steel ball [c-0.46 kJ/kg C, k-35 W/m. C] 5.0 cm in diameter and initially at a uniform temperature of 450-C is suddenly placed in a controlled environment in which the temperature is maintained at 100°C. The convection heat-transfer coefficient is 10 W/m². C. Calculate the time required for the ball to attain a temperature of 150°C.

. A steel ball [c-0.46 kJ/kg C, k-35 W/m. C] 5.0 cm in diameter and initially at a uniform temperature of 450-C is suddenly placed in a controlled environment in which the temperature is maintained at 100°C. The convection heat-transfer coefficient is 10 W/m². C. Calculate the time required for the ball to attain a temperature of 150°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.

Chapter3: Transient Heat Conduction

Section: Chapter Questions

Problem 3.30P

See similar textbooks

Similar questions

The handle of a ladle used for pouring molten lead is 30 cm long. Originally the handle was made of 1.9cm1.25cm mild steel bar stock. To reduce the grip temperature, it is proposed to form the handle of tubing 0.15 cm thick to the same rectangular shape. If the average heat transfer coefficient over the handle surface is 14 W/m K, estimate the reduction of the temperature at the grip in air at 21C.
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.
NUMBER 3 A food product with 80% moisture content in a 5 cm diameter can wants to be frozen. The density of the product is 1000 kg / m³, the thermal conductivity is 1.0 W / (m K), and the initial freezing temperature is -2.25 ° C. After 10 hours in the freezing medium -35 ° C, the product temperature becomes -10 ° C. Estimate the convection heat transfer coefficient of the freezing medium. Assume the can as an infinite cylinder. h = W / (m² K).
Air at 24°C is blown over a hot pipe with a surface area of 2.94 m2 to dissipate 924 W of heat energy. What is the minimum convection heat transfer coefficient that will ensure that the temperature of the pipe surface is less than 45°C [round your final answer to two decimal places]?
A food product with 73% moisture content in a 7 cm diameter can wants to be frozen. The density of the product is 970 kg / m³, the thermal conductivity is 1.2 W / (m K), and the initial freezing temperature is -2 ° C. After 11 hours in the freezing medium -30 ° C, the product temperature becomes -10 ° C. Estimate the convection heat transfer coefficient of the freezing medium. Assume the can as an infinite cylinder. h = W / (m² K).
For fluids with small Prandt number the thermal boundary layer development is much ....................than that of the velocity boundary layer (δt ≫ δ), and it is reasonable to assume ....................... velocity (u = u∞) throughout the thermal boundary layer. Please fill the blank
A food product with a moisture content of 80% in cans diameter 5 cm to frozen. Mass type of product is 1000 kg/m³, the thermal conductivity is 1.0 W/(m K), and temperature early frozen is -2 °C After 12 hour in the medium freezer -30 °C, the temperature of the products to be -10 °C. Estimate the coefficient of heat transfer convection medium freezing Assume cans as the cylinder is infinite, question a. h =....W/(m²K)
A food product with 80% water content in a 10 cm diameter can be frozen. Mass of the product type is 1000 kg / m³, thermal conductivity is 1.0 w / (m k), and the frozen early temperature is -1.75 ° C.After 15 hours in the freezing medium -25 ° C, the temperature of the product becomes -10 ° C. Estimating the coefficient of moving the heat of the medium freezing convection. Assume cans as an unlimited cylinder. H = Answerw / (m² k).
A glass door is used on a fireplace to reduce exfiltration of room air through the chimney. The door, 0.70m high and 1.00m wide, reaches a uniform temperature of 232oC. If the room air temperature is 23oC, estimate the rate of heat transfer to the room air due to convection. Air properties: k=0.0338W/m-K ν=26.4x10-6 m2/s Pr=0.690