Q2 : A hot surface at 100°C is to be cooled by attaching 0.25 3 cm long, 0.25 cm diameter aluminum pin fins (k =237 em W/m.°C) to it, with a center-to-center distance of 0.6 cm. The temperature of the surrounding medium is 30 °C, and the heat transfer coefficient on the surfaces is 35 W/m2.°C. Determine the rate of heat transfer from the surface for a 1x1 m2 seetion of the plate. Also determine the overall effectiveness of the fins.

Q2 : A hot surface at 100°C is to be cooled by attaching 0.25 3 cm long, 0.25 cm diameter aluminum pin fins (k =237 em W/m.°C) to it, with a center-to-center distance of 0.6 cm. The temperature of the surrounding medium is 30 °C, and the heat transfer coefficient on the surfaces is 35 W/m2.°C. Determine the rate of heat transfer from the surface for a 1x1 m2 seetion of the plate. Also determine the overall effectiveness of the fins.

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.

Chapter2: Steady Heat Conduction

Section: Chapter Questions

Problem 2.48P: The handle of a ladle used for pouring molten lead is 30 cm long. Originally the handle was made of...

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2.38 The addition of aluminum fins has been suggested to increase the rate of heat dissipation from one side of an electronic device 1 m wide and 1 m tall. The fins are to be rectangular in cross section, 2.5 cm long and 0.25 cm thick, as shown in the figure. There are to be 100 fins per meter. The convection heat transfer coefficient, both for the wall and the fins, is estimated to be K. With this information determine the percent increase in the rate of heat transfer of the finned wall compared to the bare wall.
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.
3.16 A large, 2.54-cm.-thick copper plate is placed between two air streams. The heat transfer coefficient on one side is and on the other side is . If the temperature of both streams is suddenly changed from 38°C to 93°C, determine how long it takes for the copper plate to reach a temperature of 82°C.
/ Hot square plate (1 m ×1 m) is to be cooled by attaching aluminum circular pin fins (D=0.25 cm, L= 3 cm) distributed with distance 0.6 cm as illustrated in Figs.(1-a) & (1-b). If the fin base temperature is 100°C, cooling air temperature is 30°C and h= 35 W/m. °C. Determine the total rate of heat transfer from the finned plate and the effectiveness of the fins? Assume k= 237 W/m.°C and nr=tanh mL/ mL.
A hot surface at 100°C is to be cooled by attaching 3-cm-long, 0.25-cm-diameter aluminum pin fins (k = 237 W/m · °C) to it, with a center-to-center distance of 0.6 cm. The temperature of the surrounding medium is 30°C, and the heat transfer coefficient on the surfaces is 35 W/m2·°C. Determine the rate of heat transfer (in W) from the surface for a 1-m × 1-m section of the plate. (Hints: Round down your calculated number of fins. Refer to Table 3-3.)
The length of one side of a cube-shaped freezer cabinet is 11.8 m. your closetits base is perfectly insulated against heat transfer and the inner surface temperature is –5 °C, the outer surface temperatureand it is 59°C. To ensure that the thermal load of the cabinet is not less than 0.59 kWThe thickness of the styrofoam foam insulation (k=0.03 W/mK) to be applied to the upper and side surfacesWhat should be less?
A plane wall (0.8 m x 0.6 m) at 10 oC is to be heated by attaching 7-cm-long, 3-mm-diameter pin fins (k=200 W/mK, ρ=5000 kg/m3) to it. nfin=200 fins are to be used in total. Temperature of the surrounding fluid is 100 oC, and the heat transfer coefficient on the surfaces is 35 W/m2K. Total (material + manufacturing) cost of the fins is 850 TL/kg. Fill the table below by neglecting heat transfer from the fin tips. nfin=? a) Fin efficiency b) Fin effectiveness c) Overall fin effectiveness d) Total cost of fins
Water at 5°C is being used to cool apples from an initial temperature of 25° to 10°C. Thewater flow over the surface of the apple creates a convective heat-transfer coefficientof 15 W/(m2-K). Assume the apple can be described as a sphere with a 10 cm diameterand the geometric center is to be reduced to 10°C. The apple properties include thermalconductivity of 0.45 W/(m-K), specific heat of 3.950 kJ/(kg-K), and density of 940 kg/m3.a. Determine the time that the apples must be exposed to the water.b. If the apple is submerged only for 2 hours, what will be its center temperature?
A plane wall (0.8 m x 0.6 m) at 10 oC is to be heated by attaching 7-cm-long, 3-mm-diameter pin fins (k=200 W/mK, ρ=5000 kg/m3 ) to it. nfin=2000 fins are to be used in total. Temperature of the surrounding fluid is 100 oC, and the heat transfer coefficient on the surfaces is 35 W/m2K. Total (material + manufacturing) cost of the fins is 850 TL/kg. neglecting heat transfer from the fin tips a. nfin=? b.Fin effectiveness= c.Overall fin effectiveness= d.Total cost of fins (TL)=
A total of 10 rectangular aluminum fins (k = 203 W/m:K) are placed on the outside flat surface of an electronic device. Each fin is 100 mm wide, 20 mm high, and 4 mm thick. The fins are located parallel to each other at a center-to-center distance of 8 mm. The temperature at the outside surface of the electronic device is 72°C. The air is at 20°C, and the heat transfer coefficient is 80 W/m?K. Determine (a) the rate of heat loss from the electronic device to the surrounding air and (b) the fin effectiveness.
Solution please, should correct determine the rate of heat loss of this cylindrical fin, where there is no heat loss from the ends of the cylinder. There is only convective heat loss from the curved surface of the cylinder. L = 0.5 m R = 0.02 m k = 400 W/mK h = 10 W/m^2K Ta = 298 K T0 = 773 K
As seen in the attached figure, a 5-mm-diameter spherical ball (k = 15 W/m·K, Cp=480 J/kg·K) at 50°C is exposed to a medium at 15°C, with a combined convection and radiation heat transfer coefficient of 20 W/m2·K (to be used for option a and b) a) If the ball is covered by a 1-mm-thick plastic insulation (k = 0.13 W/m·K), determine whether the plastic insulation on the ball will help or hurt heat transfer from the ball. b) Assume that the ball is initially at uniform temperature of 50 °C. Determine how long it will take for the center of the ball to drop to 20 °C.