EVAPORATION.docx

# EVAPORATION.docx - EVAPORATION CRYSTALLIZATION...

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EVAPORATION, HUMIDIFICATION, CRYSTALLIZATION 1. Rebelen was assigned to maintain the equipment by cleaning it. She was scolded by her boss since she could not clean the inside of the heat exchanger. But Reb said she would’ve cleaned it if she could. What do you think is the reason behind this? A. The boss has a high standard in cleaning. B. The equipment might have been blocked by foreign matters. C. Their company uses a hairpin type which offers only surface cleaning. D. Their company uses a Multitubular heat exchanger which does not allow tube bundles disassembly. 2. You were asked to select a type of heat exchanger but only a double pipe. Your boss will be happier if you could save more money. What would you recommend? A. Finned type B. Multitubular C. Shell and Tube D. Plat heat exchangers 3. With your knowledge in heat exchanger that at minimum temperature cross, the effectiveness of a heat exchanger is observed to be dependent, what is your conclusion in relation to the effectiveness of double-pipe heat exchangers? A. Larger temperature cross provides higher efficiency. Shell and Tube is generally more efficient than double- pipe. B. Minimal temperature cross varies inversely with efficiency, thus double-pipe is more efficient. C. For smaller volumes, shell and tube is still affected by fouling factor and thus unsuited for smaller volumes making double-pipe more efficient. D. Both A and C 4. In a counterflow heat exchanger, the hot stream is cooled from 120 to 30oC while the cold stream temperature changes from 20 to 60oC. If the same exchanger were operated with parallel flow, what would be the exit temperatures of the two streams? A. 51.5oC: 50.4oC B. 61.4oC: 20.8oC C. 88.2oC: 54.9oC D. 73.4oC: 44.9oC 5. Oil at 50oF is heated in a horizontal 2-in. Schedule 40 steel pipe 60 ft long having a surface temperature at 120oF. The oil flow rate is 150 gal/h at inlet temperature. What will be the oil temperature as it leaves the pipe and after mixing? A. 77.9oF B. 63.8oF C. 99.4oF D. 11.4 oF 6. From the prev problem, what is the average heat- transfer coefficient? A. 1.23 Btu/h·ft2·oF B. 9.99 Btu/h·ft2·oF C. 2.94 Btu/h·ft2·oF D. 8.08 Btu/h·ft2·oF 7. In a two effect forward feed evaporator; which statement is true A. the temperature in the steam chest is higher in the first than in the second effect. B. the temperature in the steam chest is lower in the first than in the second effect. C. The pressure in the second effect must be reduced below that in the first. D. In some cases, the first effect may be at a pressure above atmospheric 8–10. Compute the heat required to vaporize 1 lb of water in an evaporator producing caustic solution containing 40% NaOH by weight, at a pressure of 3.716 psia, when feeding 20% NaOH solution to the evaporator at the boiling temperature in the evaporator. What is the boiling point elevation?

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• Spring '16
• Sir
• Shell, d., A.

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