A plane wall with constant properties is initially at a uniform temperature
(a) On
(b) On
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Fundamentals of Heat and Mass Transfer
- Which formula is used to calculate the heat conduction in the AXIAL direction in a vertically located pipe segment whose inner and outer surfaces are perfectly insulated. Here r, is inner radius, r, outer radius, Tri pipe inner surface temperature, Tro pipe outer surface temperature, L is the length of the pipe, T the temperature on the lower surface, Ty the temperature on upper surface. Tu r; Tro rarrow_forwardA curved surface of a rod of length L is perfectly insulated against the flow of heat. The rod, which is so thin that heat flow in it can be assumed to be one dimensional, is initially at the temperature Ug.0=50 x/2L °C. Find the temperature at any point in the road at any subsequent time if at t=0 the temperature at each end of the rod is suddenly reduced to 0°C and maintained at that temperature thereafter.arrow_forward(Q4) A 4m x 6m wall consists of 4 glass windows of 2m x 1.5m dimensions. The wall has thickness of 0.13m and a thermal conductivity of 0.5 W/m.K, while the glass windows are 6 mm thick with a thermal conductivity of 1.228 W/m.K. The values of intemal and external surface conductance for the wall (including glass) are 7.8 W/m? K and 34.4 W/m².K, respectively. The intemal and extemal temperatures are 22° C and 42°C, respectively. Calculate the total heat transfer rate through the wall. What percentage of this heat transfer is through the windows?arrow_forward
- How long should it take to boil an egg? Model the egg as a sphere with radius of 2.3 cm that has properties similar to water with a density of = 1000 kg/m3 and thermal conductivity of k = 0.606 Watts/(mC) and specific heat of c = 4182 J/(kg C). Suppose that an egg is fully cooked when the temperature at the center reaches 70 C. Initially the egg is taken out of the fridge at 4 C and placed in the boiling water at 100 C. Since the egg shell is very thin assume that it quickly reaches a temperature of 100 C. The protein in the egg effectively immobilizes the water so the heat conduction is purely conduction (no convection). Plot the temperature of the egg over time and use the data tooltip in MATLAB to make your conclusion on the time it takes to cook the egg in minutes.arrow_forwardA cup of coffee with cooling constant k = 0.09 min- 1 is placed in aroom at temperature 20°C.(a) How fast is the coffee cooling (in degrees per minute) when its temperature is T = 80° C?(b) Use the Linear Approximation to estimate the change in temperatureover the next 6 s when T = 80°C.( c) If the coffee is served at 90°C, how long will it take to reach an optimaldrinking temperature of 65°C?arrow_forwardThe initial temperature of a 50 cm long silver wire is 50 °C. The circumference of the wire in question is completely insulated, but both ends are kept at a temperature of 0 °C (zero degrees Celsius). Obtain the heat conduction along the wire as a function of time and position and, taking a single term in the solution, determine how many degrees Celsius the temperature in the middle of the rod will be after 7 minutes. (For silver wire, α=1.70 cm2/s.)arrow_forward
- Find the two-dimensional temperature distribution T(x,y) and midplane temperature T(B/2,W/2) under steady state condition. The density, conductivity and specific heat of the material are p=(1200*32)kg/mº, k=400 W/m.K, and cp=2500 J/kg.K, respectively. A uniform heat flux 9" =1000 W/m² is applied to the upper surface. The right and left surfaces are also kept at 0°C. Bottom surface is insulated. 9" (W/m) T=0°C T=0°C W=(10*32)cm B=(30*32)cmarrow_forwardA hot water pipe is 100 mm in diameter and 80 m long. This pipe is insulated in two layers. First layer is 25 mm thick, thermal conductivity is 0.12 W/m C material, second layer is 45 mm thick It is made of material with a thermal conductivity of 0.05 W/m C. T1, T2 and T3 are the surface temperatures in the pipe. One With the acceptance of heat transfer in dimensional and continuous conditions, transfer from the pipe in case T1= 600 OC and T3= 35 C Find the amount of heat released and the temperature T2. 2.tabaka 1.tabaka 100 mm T₁ T₂ T3arrow_forward= Consider a large plane wall of thickness L=0.3 m, thermal conductivity k = 2.5 W/m.K, and surface area A = 12 m². The left side of the wall at x=0 is subjected to a net heat flux of ɖo = 700 W/m² while the temperature at that surface is measured to be T₁ = 80°C. Assuming constant thermal conductivity and no heat generation in the wall, (a) express the differential equation and the boundary equations for steady one- dimensional heat conduction through the wall, (b) obtain a relation for the variation of the temperature in the wall by solving the differential equation, and (c) evaluate the temperature of the right surface of the wall at x=L. Ti до L Xarrow_forward
- 2.1 i. ii. 2.2 2.3 A plane wall with thermal conductivity of 10.2 W/m °C, thickness of 100mm, and area of 3m². The steady surface temperatures are 170 °C and 100 °C, as shown in the figure below. Determine: rate of heat flow across the plane wall and, temperature gradient in the flow direction. ( An oven whose thickness of side wall is 82.5mm has a thermal conductivity of wall insulation of 0.044 W/m °C. The temperature on inside of the side wall is 175 °C and the energy dissipated by the electric coil within the oven is 40.5 W. Determine the area of wall surface so that temperature on the other side of wall does not exceed 75 °C. (4) A 2-kW resistance heater wire whose thermal conductivity is k = 15 W/m - °C has a diameter of D = 4 mm and a length of L = 0.5 m, and is used to boil water. If the outer surface temperature of the resistance wire is Ts = 105°C, determine the temperature at the centre of the wire. (.arrow_forwardA certain material has a thickness of 30 cm and a thermal conductivity of 0.04 W/m- °C. At a particular instant in time, the temperature distribution with x, the distance from the left face, is T = 150x ^ 2 - 30x , where x is in meters. Calculate the heat-flow rates atx x = 0 and x = 30 cm . Is the solid heating up or cooling down?arrow_forwardThree (3) bricks, specifically A, B, and C were arranged horizontally in such a way that it can be illustrated as a sandwich panel. Consider the system to be in series and in the order of Brick A, Brick B and Brick C. The outside surface temperature of Brick A is 1,500℃ and 150 ℃ for the outside surface of Brick C. The thermal conductivities for Brick A, Brick B and Brick C, are 2 ?/? °? , 0.50 ?/? °? , 60 ?/? °?. The thickness of Brick A and Brick C are 50 cm and 22 cm. The rate of heat transfer per unit area is 1,000 ?/?2 . Determine the following: The thickness of Brick B in the unit of mm. Assume that all the conditions were retain except that the thickness of Brick B was increased to 800 mm, what is the new value for the rate of heat transfer per unit area in ???/ℎ? . ??2 please explain the principles to solve thisarrow_forward
- Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning