Which device uses a tapered tube to measure fluid flow from bottom to top?

The device that utilizes a tapered tube to measure fluid flow from bottom to top is fundamentally known as a variable area meter, and this includes types like the rotameter. The tapered design allows for the flow area to change as the float rises or falls within the tube, depending on the flow rate of the fluid.

As fluid enters the tapered tube at the bottom, it accelerates and causes the float to rise. The height to which the float rises is directly related to the flow rate: a higher flow rate results in a higher float position. This relationship enables easy visual measurement of flow as the position of the float can be correlated to flow rate on a calibrated scale attached to the tube.

This mechanism is key for applications where continuous and simple flow measurement is needed, making the variable area meter an effective choice in many industrial settings. Its design allows for clear, visual indication of fluid flow, which is particularly beneficial in scenarios where electronic measurements may not be practical or reliable.

In contrast, devices like flow switches or orifice plates utilize different principles for measuring flow and do not rely on the tapered tube design for fluid measurement. Therefore, the correct identification of the device as the variable area meter highlights its specific function and design within flow measurement technologies.