Singular pressure loss in a bend

[Benoit0]

Hello everyone,

I have difficulties estimating the singular pressure drop coefficient of a 90° bend of radius ratio 1.5, based on literature. For example, if I look at the Idel'Cik book, I find a value of 0.17. If I take a different reference: "TRW Fluid Designers Handbook", I get a coefficient of 0.6. If I take a look at a third reference: "Flow of fluids through valves, fittings, and pipe" (Crane), I get a different value (from a table not in function of radius / diameter but of the diameter...), and so on.
I cannot figure out which reference I should use and why?
Does anyone have an idea or an explanation why there are so many values?

Thanks a lot
Benoit

 

[Achy47]

Hello Benoit,

The difference in values for the singular pressure drop coefficient of a 90° bend can be attributed to several factors. First, it is important to note that there is no single universal value for this coefficient as it is highly dependent on the specific conditions and parameters of the bend, such as the flow rate, fluid properties, and bend geometry.

One factor that can contribute to the variation in values is the experimental method used to determine the coefficient. Different studies may use different setups and techniques, leading to slightly different results. Additionally, the data in different references may have been obtained from different sources, such as experimental tests, simulations, or theoretical calculations, which can also lead to discrepancies.

Another factor to consider is the type of fluid being used. Different fluids have different flow behaviors and properties, which can affect the pressure drop coefficient. For example, a more viscous fluid will experience a higher pressure drop compared to a less viscous fluid.

Finally, the accuracy and precision of the measurements can also play a role in the variation of values. It is important to carefully consider the methodology and sources used in each reference to determine which one may be most appropriate for your specific application.

In conclusion, the variation in values for the singular pressure drop coefficient of a 90° bend is a result of the complex nature of fluid flow and the different factors that can influence it. It is important to carefully evaluate and compare multiple references to determine the most suitable value for your specific situation. I hope this helps. Best of luck with your research.