Q:A hot surface at 100°C is to be cooled by attach- ing 3-cm-long, 0.25-cm-diameter aluminum pin fins (k 237 W/m · °C) to it, with a center-to-center distançe 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. %3D Determine the rate of heat transfer from the surface for a 1-m X 1-m section of the plate. Also determine the overall effectiveners of the fins. Ans. Q=17.4 kW , E fin = 7.1 3 cm 0.6 cm 0.25 cm

Q:A hot surface at 100°C is to be cooled by attach- ing 3-cm-long, 0.25-cm-diameter aluminum pin fins (k 237 W/m · °C) to it, with a center-to-center distançe 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. %3D Determine the rate of heat transfer from the surface for a 1-m X 1-m section of the plate. Also determine the overall effectiveners of the fins. Ans. Q=17.4 kW , E fin = 7.1 3 cm 0.6 cm 0.25 cm

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.

Chapter1: Basic Modes Of Heat Transfer

Section: Chapter Questions

Problem 1.19P: 1.19 A cryogenic fluid is stored in a 0.3-m-diameter spherical container is still air. If the...

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1.19 A cryogenic fluid is stored in a 0.3-m-diameter spherical container is still air. If the convection heat transfer coefficient between the outer surface of the container and the air is 6.8 , the temperature of the air is 27°C, and the temperature of the surface of the sphere is –183°C, determine the rate of heat transfer by convection.
The heat transfer coefficient between a surface and a liquid is 57 W/(m2K). How many watts per square meter will be transferred in this system if the temperature difference is 10C?
1.67 In beauty salons and in homes, a ubiquitous device is the hairdryer. The front end of a typical hairdryer is idealized as a thin-walled cylindrical duct with a 6-cm diameter with a fan at the inlet that blows air over an electric heating coil as schematically shown in the figure. The design of this appliance requires two power settings, with which the air blown over the electric heating coil is heated from the ambient temperature of to an outlet temperature of and with exit air velocities of 1.0 m/s and 1.5 m/s. Estimate the electric power required for the heating coil to meet these conditions, assuming that heat loss from the outside of the dryer duct is neglected.
Heat is transferred at a rate of 0.1 kW through glass wool insulation (density=100kg/m3) with a 5-cm thickness and 2-m2 area. If the hot surface is at 70C, determine the temperature of the cooler surface.
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.
1.60 Two electric resistance heaters with a 20 cm length and a 2 cm diameter are inserted into a well-insulated 40-L tank of water that is initially at 300 K. If each heater dissipates 500 W, what is the time required for bringing the water temperature in the tank to 340 K? State your assumption for your analysis.
H.W. Q:A hot surface at 100°C is to be cooled by attach- ing 3-cm-long, 0.25-cm-diameter aluminum pin fins (k 237 W/m - °C) to it, with a center-to-center distançe 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 1-m x 1-m section of the plate. Also determine the overall effectiveners of the fins. Ans. Q=17.4 kW , E fin = 7.1 3 сm 0.6 cm 0.25 cm
Q2: A hot surface at 150°C is to be cooled by attaching 4- cm-long, 0.3-cm-diameter aluminum pin fins (k = 200 W/m • °C) to it, with a center- to-center distance of 1 cm. The temperature of the surrounding medium is 25°C, and the heat transfer coefficient on the surfaces is 40 W/m2.°C. Determine the rate of heat transfer from the surface for a 2m * 2m section of the plate. Also determine the overall effectiveness of * .the fins
A wall of length "L" m and height "H" m is made from a thick bricklayer of 38 cm with thermal conductivity of 0.57 W/mK is subjected to heat transfer due to the outside temperature as 35 oC and inside temperature 28 oC. If the energy loss is 10465 kJ in 11 hours. Determine the Heat transfer rate, Surface Area and Length and Height of the wall, if L = 3.5 H. Solution: i) Heat Transfer Rate (in Joule/Sec) = ii) Surface Area of the Wall (in m2) = iii) Height of the Wall (H in m) = iv) Length of the Wall (L in m) =
A wall of length "L" m and height "H" m is made from a thick bricklayer of 20 cm with thermal conductivity of 0.59 W/mK is subjected to heat transfer due to the outside temperature as 38 oC and inside temperature 24 oC. If the energy loss is 12867 kJ in 9 hours. Determine the Heat transfer rate, Surface Area and Length and Height of the wall, if L = 2 H. Solution: Heat Transfer Rate (in Joule/Sec) = Surface Area of the Wall (in m2) = Height of the Wall (H in m) = Length of the Wall (L in m) =
Consider a large plane wall of thickness L=0.4 m, thermal conductivity k =1.8 W/m.K, and surface area A=30 m2. The left side of the wall is maintained at a constant temperature of T1= 900C while the right side loses heat by convection to the surrounding air at T∞= 250C with a heat transfer coefficient of h = 24 W/m2.K. Assuming constant thermal conductivity and no heat generation in the wall, (a) express the differential equation and the boundary conditions for steady one-dimensional heat conduction through the wall. (b) Obtain a relation for the variation of temperature in the wall by solving the differential equation and (c) evaluate the rate of heat transfer through the wall. Heat transfer course
Q1) Consider the base plate of a 800-W household iron having a thickness of L=0.6 cm, base area of A=160 cm2, and thermal conductivity of k3120 W/m-°C. The inner surface of the base plate is subjected to uniform heat flux generated by the resistance heaters inside. When steady operating conditions are reached, the outer surface temperature of the plate is measured to be 85°C. Disregarding any heat loss through the upper part of the iron and taking the nodal spacing to be 0.2 cm, (a) obtain the finite difference formulation for the nodes and (b) determine the inner surface temperature of the plate by solving those equations. Insulation Resistance heater, 800 W 85°C Base plate Ar= 0.2 cm 160 cm? 11111111111I D00000000000000000000000