70 on the morning of the first day of 2014
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For gas turbines cooled by shell-and-tube coolers, the cooling gas needs to be cooled from 390°C to 100°C. Regarding the cooling schemes and the selection of cooling media, which of the following options are less suitable? A is cooled by circulating cooling water; B is cooled by fresh primary water; C is cooled by a heat transfer oil closed-loop system, with the heat transfer oil being further cooled by circulating water; D is cooled by a pure water closed-loop system with a temperature difference of 30°C, with the pure water being further cooled by circulating water. AC are definitely correct, and since it’s a multiple-choice question, I will definitely choose BD. But I don’t know why D is incorrect; please ask an expert to help
Gas turbine cooled by a shell-and-tube cooler
The temperature difference between the circulating water and the pure water is small, resulting in poor cooling efficiency
Cooling with water is not appropriate; circulating water, primary water, and pure water will all undergo vaporization. If steam is introduced into water, you know what the consequences will be, so I choose C.
Neither circulating water nor fresh water is suitable for direct cooling, as the temperature at the gas phase outlet is very high; using circulating water or fresh water for direct cooling would cause severe scaling in the heat exchanger, leading to its rapid failure. The indirect cooling method should be used. So the answer is CD.
AB is definitely not an option; C is definitely acceptable; D is uncertain. Please advise those who are more knowledgeable