Example: Steam in a heating system flows through tubes whose outer diameter isD1=3 cm and whose walls are maintained at: temperature of 120°C. Circular aluminun fins ( k=180 W/m °C) of outer diamete D2 6 cm and constant thickness t =2 mn are attached to the tube, as shown in Fig The space between the fins is 3 mm, an thus there are 200 fins per meter lengtl of the tube. Heat is transferred to th surrounding air at T= 25°C, with a combined heat transfer coefficient of h= 60 W/m2 °C. Determine the increase in heat transfer from the tube per meter of its length as a result of adding fins.

Example: Steam in a heating system flows through tubes whose outer diameter isD1=3 cm and whose walls are maintained at: temperature of 120°C. Circular aluminun fins ( k=180 W/m °C) of outer diamete D2 6 cm and constant thickness t =2 mn are attached to the tube, as shown in Fig The space between the fins is 3 mm, an thus there are 200 fins per meter lengtl of the tube. Heat is transferred to th surrounding air at T= 25°C, with a combined heat transfer coefficient of h= 60 W/m2 °C. Determine the increase in heat transfer from the tube per meter of its length as a result of adding 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.

Chapter3: Transient Heat Conduction

Section: Chapter Questions

Problem 3.10P: 3.10 A spherical shell satellite (3-m-OD, 1.25-cm-thick stainless steel walls) re-enters the...

See similar textbooks

Similar questions

3.10 A spherical shell satellite (3-m-OD, 1.25-cm-thick stainless steel walls) re-enters the atmosphere from outer space. If its original temperature is 38°C, the effective average temperature of the atmosphere is 1093°C, and the effective heat transfer coefficient is , estimate the temperature of the shell after reentry, assuming the time of reentry is 10 min and the interior of the shell is evacuated.
An electrical transmission line of 1.2-cm diameter carries a current of 200 amps and has a resistance of 310-4 ohm per meter of length. If the air around this line is at v, determine the surface temperature on a windy day, assuming a wind blows across the line at 33 km/h.
A transformer is to be cooled via forced air convection. To increase the effectiveness of thecooling, Alloy 1095 cast aluminum fins are attached to the top of the transformer overwhich air is blown (negligible thermal contact resistance between the transformer and thefins). The fins are 2 cm thick and 7 cm long and span the entire length of the transformer,and the transformer is 7 cm wide and 10 cm long. Air leaves the cooling fan at 25°C .a) Decide how to model the fins before performing any real analysis. Youare willing to accept some error in your analysis and so you will either model thefins as having adiabatic tips or being infinitely long. You expect the average convectioncoefficient over the heat transfer surfaces for this system to be around 50 W m2– K⁄ .Which tip condition should you use for the fins in your analysis? b) Modeling the transformer as being isothermal, determine the average convectioncoefficient over the heat transfer surfaces. Account for heat transfer from the…
Natural convection heat coefficient for vertical stainless pipe, outer diameter 100 mm, length 0.25 m. The pipe surface temperature is 125 ° C, and the air temperature is 30 ° C. Convection coefficient = Answer W / m² ° C.
A 15 cm outer diameter steam pipe is lagged to 25 cm diameter with magnesia of thermal conductivity 0.05 W/mK and further lagged with 30 cm diameter laminated asbestos of thermal conductivity 0.07 W/mK. Inner temperature of steam is 200° C and outer temperature is 25° C. Calculate the mass of steam condensed per hour for 120 m length of pipe. Assume latent heat of steam is 1900 kJ/kg.
Q1) A polished metal pipe (8 cm) owtside diameter and 350 K temperature at the outer surface is exposed to ambient conditions at 285 K temperature. The emissivity of the surface is 0.3 and the convection coefficient of heat transfer is 13.5 Wim2-deg. What would be the overall coefficient of heat transfer by the combined mode of convection and radiation” Q2 find the pressure point (1) if the amospheric pressure is(70kpajihl =0 2,h2=0.4,h3=0. ‘)(p. =13600kg/m3. poil=850kg/m3)
Engine Oil at 58.95 degrees celsius Flows over a 5m long flat plate whose temperature is 20.11 degrees celsius with a velocity of 2.2m/s. Determine the rate of heat transfer (W), considering forced convection, per unit width of the entire plate. Density = 876kg/m^3 Thermal conductivity = 0.144W/m-K Pr = 2870 dynamic viscosity = 0.21kg/m-s Q = ?
Air at 24°C is blown over a hot pipe with a surface area of 2.94 m2 to dissipate 924 W of heat energy. What is the minimum convection heat transfer coefficient that will ensure that the temperature of the pipe surface is less than 45°C [round your final answer to two decimal places]?
Find the minimum amount of diameter for the insulation of a spherical water tank? Radius of the tank is 10 m, thermal conductivity is 25 W/(m^2*K) and convective coefficient is 5 W/(m*K)
A horizontal pipe having a surface temperature of 67 °C and diameter of 20 cm is buried at a depth of 1 m in the earth at a location where k = 1.8 W/m-°C. The earth surface temperature is 15 °C. Calculate the shape factor if the pipe length is 10 m.
A transformer that is L=20cm long, 6.2 cm wide, and 5 cm high is to becooled by attaching a 10 cm × 6.2 cm wide polished aluminum heatsink (emissivity =0.03) to its top surface. The heat sink has seven fins,which are 5 mm high, 2 mm thick, and 10 cm long. A fan blows air at25°C parallel to the passages between the fins. The heat sink is todissipate 20 W of heat and the base temperature of the heat sink is notto exceed 60°C. Assuming the fins and the base plate to be nearlyisothermal and the radiation heat transfer to be negligible, determinethe minimum free-stream velocity the fan needs to supply to avoidoverheating. (k=0.02681W/m˚C, Pr=0.7248, V= 1.726×10-5 m2/s, )
A 10 cm diameter pipe is covered by 2 layer of logging. the inside layer is 4 cm thick and has a coefficient of thermal conductivity of 0.08 w/m-k. the outside layer is 3 cm thick and has coefficient of thermal conductivity of 0.15 w/m-k. the steam main conveys steam a pressure of 1.7 mpa with 25 C superheat. the outside temperature of the lagging is 27 C. if the steam main is 30 m long, determine the interface temperature of the lagging and overall coefficient of heat transfer based on outside area.