Alberta Boilers Safety Association (ABSA) Practice Test

The correct answer indicates that in a Venturi tube, approximately 90% of the upstream pressure can be recovered downstream. This high level of pressure recovery is due to the design of the Venturi tube, which efficiently converts pressure energy into kinetic energy and then back into pressure energy as the fluid moves through varying diameters.

Initially, as fluid enters the narrower section of the tube, its velocity increases, leading to a drop in pressure as described by Bernoulli's principle. After passing through the narrow part, the fluid enters a wider section, where the velocity decreases and the pressure begins to recover. The ability of the Venturi tube to maintain a relatively high percentage of the initial pressure downstream is a significant characteristic that makes it useful in various applications, such as fluid flow measurement and control systems.

The efficiency of this pressure recovery can be influenced by factors like the length of the tube and the fluid's properties, but generally, a well-designed Venturi will approach this 90% recovery threshold under ideal conditions.