Which of the following is NOT a type of hydraulic pump?

A heat exchanger is not a type of hydraulic pump because its primary function is to transfer heat between fluids and not to generate hydraulic pressure or flow. Hydraulic pumps are designed to convert mechanical energy into hydraulic energy, thereby facilitating the movement of fluid within a hydraulic system. In contrast, the other options—gear pump, piston pump, and screw pump—are all specific types of hydraulic pumps that perform the function of moving fluid and creating pressure in hydraulic circuits. Gear pumps use interlocking gears to move fluid, piston pumps utilize pistons to create pressure, and screw pumps work by using screws to transport fluid. Each of these types effectively fulfills the requirements of hydraulic systems, while a heat exchanger serves an entirely different purpose related to thermal management.