Update: Add an article on the latest formulas for gas pipeline pressure drop calculation

The equation derived in this article assumes an incompressible fluid, which is the reason for the introduction of errors. In fact, when the pressure difference accounts for 10% of the inlet pressure, it should be considered as a compressible fluid. The calculation results using the isothermal equation are as follows:

This post was last edited by wiseboy on 2021-10-9 09:08. In differential elements, changes in pressure and compression are infinitesimal. Do you understand mathematics? Have you heard of calculus? Have you been to school? You learned math from a physical education teacher, right?

This post was last edited by wiseboy on 2021-10-9 09:14. The traditional isothermal formula has two major drawbacks: 1. It cannot be used when the pressure drop is large. For example: the inlet pressure p1 is 500 kPa, and the outlet pressure p2 is 200 kPa, resulting in a pressure drop of 60%. In this case, the traditional isothermal formula yields extremely large errors and cannot be used. 2. Use the average density, which requires trial and error (iteration) to determine and is very time-consuming. The new formula lacks these drawbacks, so it’s time to retire the traditional isothermal formula that has been in use for a century.

With that tone of yours when discussing issues, I can only laugh. Time will prove everything.

You had better comment on things you know a little about. Goodbye.

After carefully studying the original author’s article, it is evident that the paper makes clever use of the relationship ρu=Const. during gas pipeline transportation to achieve variable separation, thereby avoiding the trial-and-error iterative calculations required when using traditional formulas to determine the average density of the gas, which makes it more convenient to use. It is applicable to common situations where the work done due to expansion during gas pipeline transportation and the resulting change in internal energy are not significant (in other words, the temperature change caused by pressure drop is not substantial) ； For longer pipelines of several thousand meters and similar scenarios, segmented calculation may be required.

This post was last edited by wiseboy on 2021-10-12 at 16:49. Only one figure is made public now; this figure is an illustration from another journal article. As for segmentation, if the temperature remains constant, the new formula exhibits \"independence from segmentation\"; that is, the new formula yields the same results whether segmentation is done into 1000 segments or just 1 segment. This is precisely the feature of the new formula. We have proved, and verified through numerical computation, the following theorem: the traditional isothermal formula is infinitely piecewise, and the cumulative pressure drop converges to the result of this formula (the 1st piece). In other words, the traditional isothermal formula exhibits significant effects after segmentation, which proves that it is inherently prone to large errors. Specifically in the example below, the traditional isothermal formula is divided into 220 segments (based on isothermality! ), the difference between the sum of the voltage drops across these 220 segments and the voltage drop calculated for 1 segment using the new formula

Generally, in cases such as longer pipelines spanning several thousand meters, the pressure difference can be significant. Moreover, when transporting non-ambient temperature gases, even with optimal insulation, there is often a substantial temperature difference between the inlet and outlet. From the perspective of considering these factors, it is therefore recommended that calculation may need to be done in segments, not due to any issues with the applicability of the formula itself.