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4b Group1

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4b Group1

1. 1. Group 1 4ChE B Almazar, Karina Ascalon, Kristine Malana, Rebecca Rozario, Vera Cresta Tancio, Romar
2. 2. Problems <ul><li>1.) A steam pipe 5 cm outside diameter has an outside surface temperature of 175 °C. The pipe is covered with a coating material 5 cm, thick. The thermal conductivity of the coating varies with the temperature such that, k= 0.89 + 0.0015T where T is in °C and k in W/mK. The outside surface of the coating is at 38 °C. Calculate the heat loss per meter of pipe length. </li></ul>
3. 3. Solution <ul><li>Given: D= 5cm L= 1m T1= 175°C T2= 38°C </li></ul><ul><li>k2= 0.89 + 0.0015T </li></ul><ul><li>K2 = 0.89 + 0.0015(38°C) = 0.947 W/mK </li></ul><ul><li>Do = 0.05 + 0.05(2) = 0.15 m </li></ul><ul><li>Di = 0.05 m </li></ul>q=
4. 4. Problems <ul><li>9.) A small electric furnace is 15 by 15 by 30 cm inside dimensions and has fire-brick walls (k= 1.12 W/mK) 2m thick. The front of the furnace is movable wall which permits entry into the furnace. In this section is by a 5 by 5 by 0.6 cm quartz observation windows (k= 0.07 W/mK). The inner temperature for all sides is 1100 °C, and the outer surface temperature is 121°C. Assuming all joints perfectly made and neglecting the influence of the corners on the temperature distribution, what is the heat loss from this furnace?. </li></ul>
5. 5. Solution 1 2 4 5 3 0.15 m 2m 0.30m GIVEN: q T=1100 0 C T=121 0 C 3 is .05 x .05 x .006
6. 6. Solution
7. 7. Solution <ul><li>k= 1.12 W/mK </li></ul><ul><li>R 3 </li></ul>
8. 8. Solution
9. 9. Problems <ul><li>5.2-1. Temperature Response in Cooling a Wire. A small copper wire with a diameter of 0.792 mm and initially at 366.6 K is suddenly immersed in a liquid held constant at 311 K. The convection coefficient h=85.2W/m2. K. The physical properties can be assumed constant and are k=372 W/m.K , Cp=0.389 kJ/kg.K ρ = 8890kg/m 3 </li></ul><ul><li>a. Determine the time in seconds for the average temperature of the wire to drop to 338.8K (one-half the initial temperature difference). </li></ul><ul><li>b. Do the samew but =11.36W/m2.K. </li></ul><ul><li>c. For part (b), calculate the total amount of heat removed for a wire 1.0 m long. </li></ul>
10. 10. <ul><li>Given: </li></ul><ul><li>D=0.792mm T 1 =366.5 K T 2 =311K h=85.2W/m.K </li></ul><ul><li>K=374 W/m.K Cp=0.389 kJ/kg.K ρ = 8890kg/m 3 </li></ul><ul><li>a. </li></ul><ul><li>T’ = 338.8 K </li></ul><ul><li>X 1 = D/4 = (0.792/4) x (1/1000) = 1.98x10 -4 </li></ul><ul><li>NBi= hX 1 /K = (85.2 x 1.98x10 -4 )/ 374 = 4.51x10 -5 <<0.1 </li></ul>Solution
11. 11. <ul><li>Lumped capacity method can be used </li></ul><ul><li>t = 5.56 sec </li></ul>Solution
12. 12. <ul><li>b.) </li></ul><ul><li>if h = 11.36W/m.K </li></ul><ul><li>t = 41.65 sec </li></ul>Solution t = 41.65 sec
13. 13. Solution <ul><li>L = 1.0m </li></ul><ul><li>q = (0.398x 1000) (8890) (4.927X-10 -7 ) (366.5-311) </li></ul><ul><li>(1-e -(0.0166)(41.65) ) </li></ul><ul><li>q = 47.20 J </li></ul>
14. 14. <ul><li>4.3-4. Heat Loss from Steam Pipeline. A steel pipeline, 2-in. schedule 40 pipe, contains saturated steam at 121.1 0 C. The line is covered with 25.4 mm of insulation. Assuming that the inside surface temperature of the metal wall is at 121.1 0 C and the outer surface of insulation is at 26.7 0 C , calculate the heat loss for 30.5 m of pipe. Also, calculate the kg of steam condensed per hour in the pipe due to the heat loss. The average k for steel from Appendix A.3 is 45 W/m. K and the k for the insulation is 0.182. </li></ul>Problems
15. 15. <ul><li>Given: 2” Sch 40 steel pipe L = 30.5m K s = 45W/m.K </li></ul><ul><li>Insulation thickness = 25.4mm K i = 0.182 W/m.K </li></ul><ul><li>T 1 = 121.1  C T 2 = 26.7  C </li></ul><ul><li>a.) </li></ul><ul><li>2” Sch 40: </li></ul><ul><li>D o = 2.375” (0.0254) = 0.0603m </li></ul><ul><li>D i = 2.067” ((0.0254) =0.0525m </li></ul><ul><li>X = 0.154” (0.0254) =3.9116 x 10 -3 m </li></ul>Solution
16. 16. Solution <ul><li>D i = 0.0603m </li></ul>D i = 0.0603m