5. A pin fin of uniform, cross-sectional area is fabricated of an aluminum alloy (k=160 W/m-K). The fin diameter isD=4mm, and the fin is exposed to convective conditions characterized by h=220W/m²-K. It is reported that the finefficiency is n = 0.65. Determine the fin length Z and the fin effectiveness ε. Account for tip convection. Answer: 23.5

Answered: 5. A pin fin of uniform,…

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

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1. Determine the heat flow for (i) rectangular fins and (ii) triangular fin of 20 mm length and 3 mm base thickness. Thermal conductivity 100 W/m2K, base temperature = 120°C surrounding fluid temperature = 35°C. Determine also the fin effectiveness. 2. A circumferential fin on a pipe of 50 mm OD is 3 mm thick and 20 mm long. Using the property values and other parameters in 1, determine the: = 45 W/m K. Convection coefficient h= (i) heat flow and effectiveness (ii) If the pitch is 10 mm, determine the increase in heat flow for 1 m length of pipe. Also determine the total efficiency. Circumferential rectangular fin Rectangular and Triangular fins 100 100 80 80 2c 60 * 60 40 40 20 0.5 1.0 1.5 2.0 2.5 3.0 0.5 1.0 1.5 2.0 2.5 3.0 0.5 h 0.5 h kAP 1.5 1.5 L RAP Le = L+ A, = t(r2 - r) A, = 2M(r2,² – r,³) L =L+ "2, = r, + L Rectangular fin A, = tL, L = L A, = 2L, (Depth Triangular fin A, = L 20 Fin efficiency, %
based on the information given here. Steam in a heating system flows through tubes whose outer diameter is 5-cm and whose walls are maintained at a temperature of 180°C. Circular aluminum alloy 2024-T6 fins [k = 186-W/m°C] of outer diameter 6-cm and constant thickness 1-mm are attached to the tube with the space between the fins 4-mm. The efficiency of these fins is 0.97 and the surface area of a single fin is 0.001916 m2. Heat is transferred to the surrounding air at 25°C, with a heat transfer coefficient of 40-W/m2°C. The total heat transfer from the finned tube per meter length in W is approximately 1910 3080 cannot be determined 2495
based on the information given here. Steam in a heating system flows through tubes whose outer diameter is 5-cm and whose walls are maintained at a temperature of 180°C. Circular aluminum alloy 2024-T6 fins [k = 186-W/m°C] of outer diameter 6-cm and constant thickness 1-mm are attached to the tube with the space between the fins 4-mm. The efficiency of these fins is 0.97 and the surface area of a single fin is 0.001916 m2. Heat is transferred to the surrounding air at 25°C, with a heat transfer coefficient of 40-W/m2°C. The surface effectiveness for the finned surface is approximately O 2.56 3.16 1.97 cannot be determined
based on the information given here. Steam in a heating system flows through tubes whose outer diameter is 5-cm and whose walls are maintained at a temperature of 180°C. Circular aluminum alloy 2024-T6 fins [k = 186-W/m°C] of outer diameter 6-cm and constant thickness 1-mm are attached to the tube with the space between the fins 4-mm. The efficiency of these fins is 0.97 and the surface area of a single fin is 0.001916 m2. Heat is transferred to the surrounding air at 25°C, with a heat transfer coefficient of 40-W/M2°C. The increase in heat transfer from the tube per meter length in W is approximately 936 2105 1521 cannot be determined
9
A sphere of 80 mm diameter (k=50 W/m.K and a=1.5x106 m²/s) is initially at a uniform, elevated temperature, and is quenched in an oil bath maintained at 50 °C. The convection coefficient for the cooling process is 1000 W/m?K. At a certain time, the surface temperature of the sphere is measured to be 200 °C. What is the corresponding center temperature of the sphere?
An electrical horizontal wire is having diameter (2 cm) and unit length. The wire is placed in room air at 10°C with heat loss (105 W) by free convection. Estimate the surface temperature for Ra=3.08 ×10. Take k = 0.02685 W/m.K Geometry Grf Prf C m Reference(s) Horizontal cylinders 0-10-5 0.4 0 Use Fig. 7-6 Use Fig. 7-6 0.53 4 0.13 0.675 0.058 1.02 0.148 0.850 0.188 0.480 1 0.125 10-5-104 104-109 10⁹-1012 10-10-10-2 10-2-10² 10²-104 104-107 107-1012 1413 1 44 4 76t 76t 76 76 76
An overhead 65-m-long, uninsulated industrial steam pipe of 80 mm diameter is routed through a building whose walls and air are at 30 °C. Pressurized steam maintains a pipe surface temperature of 200 "C, and the coefficient associated with natural convection is h = 15 W/m'K. The surface emissivity is e= steam line? 0.6. What is the rate of heat loss from the
nt Select D 0 261.40 ( 142. СС 60 Home Insert Space 300c° Insert Draw View Exercise 5 the bobul 3-75 Consider a 5-m-high 8-m-long, and 0.22-m-thick wall whose representative cross section is as given in the figure. The thermal conductivities of various materials used, in W/m-K, are k, = kp = 2, kg = 8, ke=20, kp = 15, and kg = 35. The left and right surfaces of the wall are maintained at uniform temperatures of 300°C and 100°C, respectively. Assuming heat transfer through the wall to be one-dimensional, determine (a) the rate of heat transfer through the wall; (b) the temperature at the point where the sections B, D, and E meet; and (c) the temperature drop across the section F. Disregard any contact resistances at the interfaces. RA p Re RB RC Ro RE ******** ве R=RA + ROBC+R DE + Rr ****** 300°C Ri 1000 1 сгу اللينفب اللوطن يمني نفتي المتريال 5 cm | +100 cm оста 6 cm Pencil + 100°C 0.12 M 10 C
plz answer this,ASAP,thx At high temperatures a nuclear reactor consists of a cylindrical wall composite as the fuel element thorium (k = 57 W/mK) wrapped in graphite (k = 3 W/mK) and helium gas flows through a circular cooling channel. Cylinder length 200 mm. Taking into account the helium temperature = 600°C and the convection coefficient, h= 200 W/m²K. When measured, the outside temperature is 100°C, and h = 5 W/m².K. Draw the electrical analogy, and calculate the overall heat transfer rate!

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