Starting from an analysis of the solutions provided by netizens to the question \"Question 54 in the morning of 2014\"

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This post was last edited by zwp997 on 2015-6-18 at 15:30. The discussion began with an analysis of the solutions provided by netizens to the question “54 questions from the morning of 2014: http://bbs.hcbbs.com/forum.php?m...&page=1#pid13778831”, and focused on the use of the Bai Nuli equation. As is clear from this topic, the White effort equation can also be applied in cases where the pressure change across the start and end surfaces is no more than 20% of the starting pressure. It should be noted that this is an approximate calculation within the limits of acceptable engineering error; it is not a true application of the equation. Let’s take a look at this post again: “Question 23 from the Professional Cases session in 2014, http://bbs.hcbbs.com/thread-1381617-1-2.html”. It is clear that the pressure change is 75%, so it is not possible to use the White equation for estimation. Therefore, both the association’s guidelines and the Tianjin University version of the tutorial provide formulas for calculating compressible fluids, which are the ones used in the calculation process shown in this post. Let’s take a look at another post: “Question 16 from the morning session of 2011 – Seeking help: http://bbs.hcbbs.com/thread-1318722-1-3.html”. It’s quite interesting; in this post, all the solutions involve using the Bai Nuli equation for calculations, and in fact the pressure before and after is 170%. For the calculation of the wind pressure of a fan, it should be the pressure difference between the inlet and outlet of the fan plus the dynamic wind pressure at the outlet. And indeed, a drag coefficient of 0.02 is introduced in the calculations. I believe it can be assumed that if the pressure drop in the pipeline from the gas tank to the fan, as well as the pressure drop from the fan to the boiler, are both ignored, then the total pressure of the fan, HT, can be calculated as HT = △P + (ρu^2/2). Note that there should be no resistance coefficients involved here; if such coefficients exist, it means that the chosen calculation framework is incorrect. Is the answer on the second floor still the best answer? Following my calculations, u=4×4/(3.14×0.4^2)=31.85 (m/s). △P=1200-500=700 (Pa). H=△P+ρu^2/2=700+0.9×31.85^2/2=1156.5 (Pa). N=HQ=1156.5×4=4.63(kW). So should the answer be A, as it’s quite close? There is still a problem with the calculation here, because the airflow rate and density given in the problem should correspond to the conditions at the fan inlet; the exit conditions should be used when calculating the total pressure. The distance from the inlet to the fan in the other half of the fans is shorter, so the resistance can be disregarded; however, the outlet section is 60 meters long. Could we calculate the pressure at the fan outlet by using the method outlined in question 23 from the professional case study from 2014? Incidentally, calculate the air volume and density together. I wonder if anyone is interested in getting the results.