Which of the following statements is not true?

1. All flowmeters are affected by Reynolds number.
2. Reynolds number can indicate that the flow regime can be different under different operating conditions in a given application.
3. Reynolds number is dependent on pipe diameter and the flow, density and viscosity of the fluid.
4. Reynolds number provides an indication of whether the flow in a pipe is in the laminar, transitional or turbulent flow regime.

Reynolds number is dependent on pipe diameter and the flow, density and viscosity of the fluid, so Answer C is true. Reynolds number provides an indication of whether the flow in a pipe is in the laminar, transitional or turbulent flow regime, so Answer D is true. Calculations show that if flow varies over a 10:1 range, Reynolds numbers will similarly vary over a 10:1 range, which can cause the flow regime to change. Answer B is true.

Using the process of elimination, Answer A is false. However, it would be reasonable to make the observation that positive displacement flowmeters and other flowmeter technologies are not affected by Reynolds number.

Additional complicating factors

Many flowmeters exhibit poor accuracy or do not operate in certain flow regimes. For example, laminar flow elements operate linearly in the laminar flow regime. Vortex shedding flowmeters turn off in the laminar flow regime. The squared output relationship exhibited by differential pressure flowmeters changes in the transitional and laminar flow regimes.