Another exemplary embodiment of the disclosure includes a fluid pumping system for high-pressure, high-power hydraulic fracturing operations. The system may include a direct drive unit (DDU) having a turbine engine mechanically connected to a gearbox for driving a driveshaft, and a fluid pump operatively connected to the DDU by the driveshaft for driving the fluid pump. Accordingly, one or more of the DDU and the fluid pump may generate and heat process fluid during operation, which may include lubrication oil or another lubrication medium, and/or a hydraulic or other working fluid. The system may include an enclosure assembly having an enclosure body extending around an enclosure space to house the DDU, and one or more or more heat exchanger assemblies connected to the enclosure body for cooling process fluid associated with one or more of the DDU and the fluid pump. The one or more heat exchanger assemblies of the system may include one or more intake fan assemblies positioned in fluid communication with an external environment surrounding the enclosure body, and one or more intake fan motors may be operatively connected to the one or more intake fan assemblies. When the one or more intake fan motors is activated, the one or more intake fan assemblies may draw air into the enclosure space from the external environment at the one or more intake fan assemblies and along an airflow path through the enclosure space. One or more radiator assemblies may be included in the one or more heat exchanger assemblies for receiving the process fluid, and may be positioned adjacent the one or more intake fan assemblies in the airflow path through the enclosure space to cool the process fluid with the air drawn in from the external environment as it flows through the radiator assembly.