What section of the pump increases in cross sectional area as it approaches the discharge outlet?

The volute is designed to increase in cross-sectional area as it gets closer to the pump's discharge outlet. This design enables the conversion of the kinetic energy of the fluid into pressure energy, which is crucial for efficiently directing the flow of fluid out of the pump. As the fluid exits the impeller, it moves into the volute, where the larger cross-sectional area allows for a reduction in fluid velocity and an increase in pressure.

In contrast, the other options do not fulfill this function. The Bourdon tube is a device used for measuring pressure, not for fluid flow management. The circulator valve is critical in controlling the flow and pressure in a system but does not inherently increase cross-sectional area as fluids discharge. The flow meter is focused on measuring the flow rate of a fluid, rather than transforming energy and directing flow as it exits a pump. Therefore, the correct answer highlights a key component in pump design that efficiently facilitates fluid movement.