3- A 4-mm-diameter and 10-cm-long aluminum fin (k = 237 W/m:° C) is attached to a surface. If the heat transfer coefficient is 12 W/m2 · ° C, determine the percent error in the rate of heat transfer from the fin when the infinitely long fin assumption is used instead of the adiabatic fin tip assumption.

3- A 4-mm-diameter and 10-cm-long aluminum fin (k = 237 W/m:° C) is attached to a surface. If the heat transfer coefficient is 12 W/m2 · ° C, determine the percent error in the rate of heat transfer from the fin when the infinitely long fin assumption is used instead of the adiabatic fin tip assumption.

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 3.16P: 3.16 A large, 2.54-cm.-thick copper plate is placed between two air streams. The heat transfer...

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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.
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.
Consider a steam pipe of length 15 ft, inner radius 2 in., outer radius 2.4 in., and thermal conductivity 7.2 Btu/hr-ft-°F. Steam is flowing through the pipe at an average temperature of 250°F, and the average convection heat transfer coefficient on the inner surface is given to be 1.25 Btu/hr-ft2-°F. If the average temperature on the outer surfaces of the pipe is 160°F, determine the rate of heat loss from the steam through the pipe. ANSWER:______Btu/hr
Consider a steam pipe of length L = 26 m, inner radius ? = 5 cm, outer radius ? = 7 cm, and thermal conductivity k = 25 W/m·K, as shown in Fig. The inner and outer surfaces of the pipearemaintainedataveragetemperaturesof? =120°Cand? =50°C,respectively.Obtain a general relation for the temperature distribution inside the pipe under steady conditions and determine the rate of heat loss from the steam through the pipe.
A 6-m-long 2-kW electrical resistance wire is made of 0.2-cm-diameter stainless steel(? = 15.1 W/mK). The resistance wire operates in an environment at 30°C with a heattransfer coefficient of 140 W/m2K at the outer surface. Determine the maximumtemperature in the wire;(a) by using the applicable relations.(b) by setting up the proper differential equation and solving it.
A 4-mm-diameter and 10-cm-long aluminum fin (k = 237 W/m·K) is attached to a surface. If the heat transfer coefficient is 12 W/m2·K, determine the percent error in the rate of heat transfer from the fin when the infinitely long fin assumption is used instead of the adiabatic fin tip assumption.
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·K) 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 ·K. Determine the rate of heat transfer from the surface for a 1-m x 1-m section of the plate. Also determine the overall effectiveness of the fins.
- Steam at 280C flows in a stainless steel pipe k = 15 W/m.K whose inner and outer diameter are 5cm and 5.5cm, respectively. The pipe covered with 3cm glass wool insulation k = 0.038 W/m.K. Heat is lost to the surroundings at 5C by natural convection and radiation, with a combined natural convection and radiation heat transfer coefficient of 22W/m2.K. Taking the heat transfer coefficient inside the pipe to be 80W/m2.K, determine the rate of heat loss from the steam per unit length of the pipe. Also determine the temperature drop across the pipe shell and the insulation
Steam at 200ºC flows in a cast iron pipe (k = 80 W/m⋅ºC) whose inner and outer diameters are D1 = 0.20 m and D2 = 0.22 m, respectively. The pipe is covered with 2-cm-thick glass wool insulation (k = 0.05 W/m⋅ºC). The heat transfer coefficient at the inner surface is 75 W/m2⋅ºC. If the temperature at the interface of the iron pipe and the insulation is 194ºC, the temperature at the outer surface of the insulation is
Steam at 320°C flows in a stainless steel pipe (k = 15 W/m-°C) whose inner and outer diameters are 5 cm and 5.5 cm, respectively. The pipe is covered with 3-cm-thick glass wool insulation (k = 0.038 W/m-°C). Heat is lost to the surroundings at 5°C by natural convection and radiation, with a combined natural convection and radiation heat transfer coefficient of 15Wm2-°C. Taking the heat transfer coefficient inside the pipe to be 80 W/m2-°C, determine the rate of heat loss from the steam per unit length of the pipe. Also determine the temperature drops across the pipe shell and the insulation.
Steam passes into tubes in a heating system whose outer diameter is 3 cm and whose wall is held at a temperature of 120°C. Tubes are connected to circular aluminium alloy fins (k = 180 W/m. ° C) with an outer diameter of 6 cm and a constant thickness of 2 mm. The distance between the two fins is 3 mm and the tube length is 200 fins per meter. With h = 60 W/m2.°C, the heat is transmitted to the ambient air at 25°C. Evaluate the increase in heat transfer from the tube per meter of its length as a result of adding fins.