【Test Your Knowledge】Basic Chemical Engineering Knowledge (160) Please hide your replies

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This post was last edited by zhangyong6404 on 2009-8-16 08:28. In accordance with the forum’s rules, the maximum score for this activity is 15 Wealth points; giving scores based on charm is prohibited. At the same time, friendship requests and repeated ratings are declined. To encourage active participation from members, the top 5 correct answers receive a full score; for the remaining answers, 10–15 wealth points are awarded for every correct answer, while 8–12 wealth points are given for each incorrect answer. 2 mistakes result in a loss of 6–10 wealth points; the remaining mistakes earn bonus points of 2–6 wealth points as an incentive for participation. 1. It is known that when the temperature is T, the radiation capacity of refractory bricks is greater than that of aluminum sheets; therefore, the blackness of aluminum is ( ) the blackness of refractory bricks. A is greater than B, equal to C; it’s uncertain. D is less than 2. In a certain type of shell-and-tube heat exchanger, saturated steam is used to heat the air inside the tubes (with turbulent flow of the air within the tubes), raising the air temperature from 20°C to 80°C. Now, it is necessary to double the air flow rate. If the inlet and outlet temperatures of the air are to remain unchanged, then the heat transfer temperature difference at this point should be ( ) times that of the original situation. A 1.149 B 1.74 C 2 D Indeterminate 3. For a liquid with a constant flow rate flowing turbulently in a straight pipe with dimensions of 25×2.5 mm, its convective heat transfer coefficient ai = 1000 W/m2·℃ ； If both the flow rate and physical properties remain unchanged, and a straight pipe of 1F19×2mm is used instead, then its a will become ( ). A 1259 B 1496 C 1585 D 1678 4. In the correlation equation for convective heat transfer, the Prandtl number is a parameter that represents ( ). A Convective heat transfer B Flow state C Influence of material properties D Influence of natural convection 5. In the heat transfer process between steam and air, to enhance heat transfer, which of the following approaches is feasible from an engineering perspective? A Increase the vapor flow rate B Increase the air flow rate C Use superheated vapor to raise the vapor temperature D Install fins on the tube wall on the vapor side to increase the condensation area. 6. In radiation heat transfer between two gray bodies, the temperature difference between them is 50°C; for some reason, the temperature of each of these bodies increases by 100°C. Then, compared to the original radiation heat transfer amount, the radiation heat transfer amount at this point should be ( ). A Decrease B Increase C Remain unchanged 7. In a single-effect evaporator, a certain aqueous solution is continuously concentrated from 14% to 30%. The feed liquid enters at its boiling point; the temperature of the heating steam is 96.2°C, the effective heat transfer temperature difference is 11.2°C, and the temperature of the secondary vapor is 75.4°C. Then the boiling point elevation of the solution is ( )°C. A 11.2 B 20.8 C 85 D 9.6 8. To evaporate a solution whose viscosity varies significantly with concentration and temperature, which ( ) process should be used? A Co-current feeding B Counter-current feeding C Parallel feeding D Two-effect three-body co-current feeding All members already have access to hidden replies; please cooperate actively. Starting from this issue, no scoring will be given in principle without hiding it. Thank you all! Also, be careful when posting; edits are invalid! To hide the method, click here: Hide Method. Answers for Issue 160: 1D, 2A, 3D, 4C, 5B, 6B, 7D, 8B