Example 5.16. An aluminium alloy fin (k = 200 W/m.K), 3.5 mm thick and 2.5 cm long protrudes from a wall. The base is at 420°C and ambient air temperature is 30°C. The heat transfer coefficient may be taken as 11 Wim2.K. Find the heat loss and fin efficiency, if the

Example 5.16. An aluminium alloy fin (k = 200 W/m.K), 3.5 mm thick and 2.5 cm long protrudes from a wall. The base is at 420°C and ambient air temperature is 30°C. The heat transfer coefficient may be taken as 11 Wim2.K. Find the heat loss and fin efficiency, if the

Elements Of Electromagnetics

7th Edition

ISBN:9780190698614

Author:Sadiku, Matthew N. O.

Publisher:Sadiku, Matthew N. O.

ChapterMA: Math Assessment

Section: Chapter Questions

Problem 1.1MA

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An external wall of a building has a U value of 0.50 W/m^2K. The indoor temperature is21 degrees C and the outdoor temperature is -2.0 degrees C The steady-state heat loss is calculated to be 11.5W/m^2 The wall contains a layer of insulation 40 mm thick with a conductivity of0.035 W/mK. What would the insulation thickness need to be in order toreduce the steady state heat loss by 50%? answer = 0.11m please show all working
A steel bar 7 cm long is welded end to end to a copper bar 3 cm long. Each bar has a square cross section 2.00 cm on a side. The free end of the steel with a temprature at 84 °C, and the free end of the cooper bar is at 12 °C. Find the total rate of heat flow in (W)? (ksteel =50.2 W/K.m and kcopper =385 W/K.m ) (Answer in one decimal places) Material having thermal conductivity k Area A T Steel Соpper T,> T,
Q₁: Find the heat transfer rate by adding straight fins of rectangular cross section of length 50 mm and thickness of 0.5 mm when the heat transfer coefficient from the surface is 40 W/m K and for the fins is 30 W/m°K and k=900 W/m K, surface area (1x1) and distance fins 4 mm. Ans 51526.25
a. The wall of a building has a surface area of 50 m2. The outside layer of the wall is 20 cm thick concrete with thermal conductivity kcon = .8 W/m-K. The inner layer is 10 cm thick balsa wood (kbalsa = .048 W/m-K) as an insulator. Outside temperatures of 47o C are expected, while an inside temperature of 21o C is maintained by the cooling system. Find the rate of heat transfer through the wall.
A pipe carries hot molten lead from one part of a factory floor to another. The mass flow rate of lead is 0.05 kg/s. While trying to figure out the heat loss from the pipe, you found that over a 2-m length of he pipe the lead temperature drops from 580 C to 557.C. What is the rate at which thermal energy is being lost from the lead carrying pipe in this 2-m section? Use the property table to find out properties of lead as needed.
2.19 Consider a 300 mm x 300 mm window in an aircraft. For a temperature difference of 80°C from the inner to the outer surface of the window, calculate the heat loss through L = 10-mm-thick polycarbonate, soda lime glass, and aerogel windows, respectively. The thermal conductivities of the aerogel and polycarbonate are kag = 0.014 W/m-K and kpe = 0.21 W/m-K, respectively. Evaluate the thermal conductivity of the soda lime glass at 300 K. If the aircraft has 130 windows and the cost to heat the cabin air is $1/kW-h, compare the costs associ- ated with the heat loss through the windows for an 8-hour intercontinental flight.
a. given convective heat transfer coefficient of inside air = 18.23 W/m2K, find the temperature of inside air at the end of composite wall b. neglect natural convection, find heat transfer rate due to thermal radiation c. using heat transfer rate due to thermal radiation, find the innermost wall and interface temperatures
A steel bar 4 cm long is welded end to end to a copper bar 3 cm long. Each bar has a square cross section 2.00 cm on a side. The free end of the steel with a temprature at 63 °C, and the free end of the cooper bar is at 18 °C. Find the total rate of heat flow in (W)? (ksteel =50.2 W/K.m and kcopper =385 W/K.m ) (Answer in one decimal places) Material having thermal conductivity k Area A T2 Steel Copper T,> T
For steady state heat conduction in a composite wall (As = 5 m², LA=1 cm and LB =2 cm) as shown in below figure. Calculate the total thermal resistance and the rate of heat transfer from the wall also find the temperatures Ts1, Ts2 and Tc To,z=200°C h₂=10W/m².K KA=0.1 W/m-K T5,1 HL-L₂ 17 Tc Too,2 = 40°C h₂-20W/m².K k=Q04 W/m-K
10.The layout of a wall and the heat transfer parameters are shown in the figure below. Find the internal temperature of the wall, T₁. (o= 5.67 x 10-8 W/m²K4 ) (Ans: 569.5K) T1 k=1.1 W/m.K Icond L=0.12m T2=373K x=0.7 grad Iconv Tsur Air Tex = 300K h = = 290K : 18 W/m².K
A steel pipe with heat transfer coefficient of 42 W/mK contains flowing water. The outer diameter of the pipe is 90 mm and the wall thickness is 3mm. Calculate: i. The heat loss by convection and conduction per meter length of un-insulated pipe when the water temperature is 14°C, the outside air temperature is -10°C, the water side heat transfer coefficient is 30 KW/m^2K and the outside heat transfer coefficient is 20 KW/m^2K. ii. Calculate the corresponding heat loss when the pipe is lagged with insulation having an outer diameter of 200 mm, and thermal conductivity of K = 0.05 W/mK