2-A: Give an example system or component in daily life in which all three modes of heat transfer areimportant and need to be accounted for.2-B: (a) What is your understanding of the Thermal boundary layer? (b) How do you define thethermal boundary layer thickness?2-C: Is the lumped capacitance method of analysis likely to be more applicable for cooling of a hotsolid made of aluminum or glass? Explain.

Answered: 2-A: Give an example system or…

2-A: Give an example system or component in daily life in which all three modes of heat transfer are important and need to be accounted for.

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 3.36P

See similar textbooks

Similar questions

1.79 Consider the cooling of (a) a personal computer with a separate CPU and (b) a laptop computer. The reliable functioning of these machines depends on their effective cooling. Identify and briefly explain all modes of heat transfer involved in the cooling process.
(a) The heating power generated by the nuclear heating rod and the inner temperature of the metallic cylinder, T2. (b) The temperature liquid X, which is located between the nuclear heating rod and the meatllic cylinder, Tliquid. (c) The temperature at the surface of the heating rod, T1. (d) If the salt solution temperature is 300 degree Celcius, what is the value of convection heat transfer coefficient, h of the salt solution ? (e) If the heating rod is not covered by metallic cylinder and corresponds to the result of part (c) and (d), how much the rate of energy transfer to the salt solution ? (f) Compare and discuss the difference of heat transfer with and without the matallic cylinder.
(a) The temperature at the surface of the heating rod, T1. (b) If the salt solution temperature is 300 degree Celcius, what is the value of convection heat transfer coefficient, h of the salt solution ? (c) If the heating rod is not covered by metallic cylinder and corresponds to the result of part (a) and (b), how much the rate of energy transfer to the salt solution ? (d) Compare and discuss the difference of heat transfer with and without the matallic cylinder.
For a specified heat input and a given volume which material will have the smallest tempera- ture rise (Use data book if necessary) (a) steel (b) aluminium (c) water (d) copper. When a hot metal piece is left to cool in air the time rate of cooling of the outer layer will be (a) slower at start and faster near the end (b) faster at start and slower near the end (c) both rates will be the same (d) this will depend on the material. (viii) A thin black plate at temperature T receives radiation from a surface at Temperature T1 and radiates to a surface at T2. If all surfaces are black at steady state (a) (T1 – T) > (T – T2) (b) (T1 – T) < (T – T2) (c) (T1 – T) = (T – T2) (d) can be any one of a, b or c. (ix) The temperature profile (in) a slab initially at a constant temperature and then allowed to cool by convection for a short time will be as shown in Fig : (a) E1.2a (b) E1.2b (c) E1.2c (d) E1.2d. Ti
ure f) A steel disc (k = 56.7 W/m.K, p = 7854 kg/m³, c = 487 J/kg. K) 30 cm in diameter and 10 cm thick, initially at uniform temperature of 265 °C is immersed in liquid at -15 °C. The convective coefficients on ends and on cylindrical side are 340 and 1420 W/m².K, respectively. What is the temperature at (a) center of disc, and (b) surface at centre of one end (c) Calculate heat transfer after 5 min have elapsed.
A closed room containing hot air is used to cool down slabs of asolid with a conductivity of 160 W/m*K, density of 2950 kg/m3), and a heat capacity of 920 J/kg*K). Each solid slab is 2 cm thick. Air circulates withing the room at 15 °C with a convection heat transfer coefficient of 200 W/m2*K. Do not assume steady heat transfer.(a) What is the final temperature of slabs upon leaving the room, if thetemperature of slabs before entering the room is 70 °C.(b) How much more time is needed for the temperature of the solid slabs to decrease by an additional 20 °C?
The wall (thickness L) of a furnace, with inside temperature 800° C, is comprised of brick material (thermal conductivity = 0.02 W m-! K-')). Given that the wall thickness is 12 cm, the atmospheric temperature is 0° C, the density and heat capacity of the brick material are 1.9 gm cm-3 and 6.0 J kg~1 K-l respectively, estimate the temperature profile within the brick wall after 2 hours. Solve the partial differential equation ()-~ ƏT ƏT subject to the initial condition T(x,0) = 800 sin ; 2L %3D and boundary conditions at the inner (z = L) and outer (r = 0) walls of T = 0 x =0 at and ƏT I = L at Find the temperature profile at T = 7200 seconds = 2 hours.
Consider steady-state conditions for one-dimensional conduction in a plane wall having a thermal conductivity k = 40 W/m-K and a thickness L = 0.3 m, with no internal heat generation. T2 L Determine the heat flux, in kW/m?, and the unknown quantity for each case. T1 (°C) T2(°C) dT/dx(K/m) 9 (kW/m?) Case 1 50 -20 i i 2 -30 -10 i 70 i 160 i 40 -80 i 5 i 30 200 i
quantity. Example 1/ The roof of an electrically heated home is 6 m long, 8 m wide, and 0.25 m thick, and is made of a flat layer of concrete whose thermal conductivity is k 0.8 W/m.°C (Figure. 1-3). The temperatures of the inner and the outer surfaces of the roof one night are measured to be 15°C and 4°C, respectively, for a period of 10 hours. Determine the rate of heat loss through the roof at night. Concrete roof - 0.25 m 8 m 6 m 4°C 15°C Figure 1-3 Schematic for Example 1
Steam is being transported in a pipe at a chemical production facility in Gebze, Kocaeli. Theouter diameter of the pipe is 8 cm, and the surrounding air temperature is 20 °C. On the surface of thepipe, the combined heat transfer coefficient is 35 W/m2*K. The surface temperature of the pipe is 150 °C.Steady-state conditions exist.(a) What is the rate of heat loss from the pipe to the surroundings?(b) The power used to generate the steam is obtained from natural gas. Perform an online search forapproximate values of the calorific value of natural gas, as well as the cost of natural gas per cubicmeter, and estimate the financial loss due to heat loss from this steam pipe within a period of oneyear. Indicate your sources clearly in your answer.
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) In thermal systems design projects various cost estimation methods can be followed depending on the nature of the project. Discuss at least four costing methods that can be applied in the thermal systems design and compare the strength and weakness of each method. (minimum 250 words). (b) Which method of costing do you think is appropriate for your thermal system design project? Discuss your justifications why you prefer the particular cost estimation method. (c) In the design process of air conditioning systems discuss the key steps you should carry out before production and installation of the system.