Steam cooling issue after the reaction is complete

Thread Content

Well, a small private company where one of my classmates works has a reaction vessel; the steam generated as a by-product can affect the quality of the product. Their management wants to use a pipe to carry this steam away and cool it to a temperature that isn’t too hot. They want to determine how long such a pipe needs to be, and they asked me how to do this, since I have no practical experience in this field – I’m a chemical engineering graduate who works in a different industry. Specifically, a vacuum pump is first used to reduce the pressure in the reactor from atmospheric to 20 kPa; the reactor continuously produces water vapor, at a rate of about 7 kg per hour. The temperature of the reactor is 190 degrees. The reaction vessel is connected to the vacuum pump using stainless steel pipes with an inner diameter of 8 mm and a wall thickness of 1 mm. It is required that the temperature of the material in contact with the vacuum pump not exceed 40 degrees, while the air flowing outside the stainless steel tube is at 25 degrees. How long a steel pipe is needed to cool steam at 190 degrees down to water at 40 degrees? I’m looking at the principles of chemical engineering; currently, the formula Q=KA△Tm is used for calculations. These calculations are carried out in stages – the steam is cooled to the boiling point of water at 20 kPa, which is 60 degrees Celsius, after which the steam turns into water at that temperature, and then the water is cooled further to 40 degrees Celsius. The aforementioned formula is applied in each of these stages. I’m not sure if this method is correct. Using water for cooling, I got a result of 14 meters. Now, when using flowing air for cooling, I don’t know how to determine the value of K. . Please help to solve it. . There might be many problems with the above approach, or the methods used might be incorrect; I would appreciate some guidance from those experienced in chemical engineering. . . .