Section 9.1 in Lienhard and Lienhard's A Heat Transfer Textbook. 2. Hint: To help
with this assignment, use Figure 9.3 and Example 9.1 in Section.
Unit 6 Quiz Answer Key 1. The five regimes of boiling are (i) natural convection, (ii) nucleate boiling, (iii) peak heat flux, (iv) transitional boiling regime, and (v) film boiling. Please review Section 9.1 in Lienhard and Lienhard’s A Heat Transfer Textbook. 2. Hint: To help with this assignment, use Figure 9.3 and Example 9.1 in Section 9.1 of Lienhard and Lienhard’s A Heat Transfer Textbook. It may also be helpful to review the text of the entire section. 3. When a surface is wetted, surface tension prevents liquid from entering the small holes on the surface. This forms vapor pockets on a surface. Please review Section 9.2 in Lienhard and Lienhard’s A Heat Transfer Textbook. 4. The bubble will be in mechanical equilibrium, if the pressure difference between the inside and the outside of the bubble is balanced by the forces of surface tension. Please review Section 9.2 in Lienhard and Lienhard’s A Heat Transfer Textbook. 5. q ~ ΔTanb. Nucleate boiling heat transfer increases with the number of active nucleation sites, with b is approximately 1/3. 6. Based on Rosenhow’s nucleate boiling correlation, q is proportional to g1/2. That is under the same condition, boiling heat transfer on the Moon will be less than boiling heat transfer on Earth. Please review Section 9.2 and Example 9.2 in Lienhard and Lienhard’s A Heat Transfer Textbook. 7. Taylor instability. Please review Section 9.3 in Lienhard and Lienhard’s A Heat Transfer Textbook. 8. 928 kW/m2. Hint: Use equation 9.11 and table 9.3 in Lienhard and Lienhard’s A Heat Transfer Textbook. Please review Example 9.5 in Lienhard and Lienhard’s A Heat Transfer Textbook. 9. 1053 kW/m2. Hint: Use Equation 9.11 and Table 9.3 in Lienhard and Lienhard’s A Heat Transfer Textbook. Also, please review Example 9.6 in Lienhard and Lienhard’s A Heat Transfer Textbook. 10. Compare your sketch with Figure 9.2 on page 462 in Lienhard and Lienhard’s A Heat Transfer Textbook.
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11. On a small heater, there is insufficient space for the vapor jets to organize. Please review pages 481 and 482 in Lienhard and Lienhard’s A Heat Transfer Textbook. 12. Compare your sketch with Figure 9.17 on page 497 in Lienhard and Lienhard’s A Heat Transfer Textbook. 13. Subcooled boiling occurs when the bulk liquid is cooler than the saturated temperature. Please review page 494 in Lienhard and Lienhard’s A Heat Transfer Textbook. 14. Compare your sketch with Figure 9.16 on page 495 in Lienhard and Lienhard’s A Heat Transfer Textbook. 15. Nusselt number, Pr number, Jacob number, and Rayleigh number for film condensation. Please review page 430 in Lienhard and Lienhard’s A Heat Transfer Textbook. 16. 0.014 mm. Please review Example 8.6 on pages 436 and 437 in Lienhard and Lienhard’s A Heat Transfer Textbook. 17. 104.4C. Calculation of the steam temperature can follow the following steps: Step 1: Guess the steam temperature Ts. Step 2: Calculate the properties of the film using the film temperature Tf =0.5(To+Ts). Step 3: Set up an energy balance equation: Q=DGHvap, where Q is the heat flow into the tube wall and Hvap is the latent heat. This assumes that the steam gives up only latent heat. Step 4: Calculate the film Reynold number to find out whether the flow is laminar or turbulent. Step 5: Find the appropriate equation for the heat transfer coefficient h. Step 6: The temperature of the steam is given by Ts – To = Q/h. This temperature will be different from the initial guess. Repeat step 1 to 5 until Ts converges.
Saylor URL: http://www.saylor.org/courses/ME204 Unit 6
