Which statement is NOT true regarding DX systems?

The statement about the liquid refrigerant being subcooled as it enters the evaporator is not true regarding Direct Expansion (DX) systems. In a DX system, the refrigerant that leaves the condenser should ideally be in a saturated state when it enters the evaporator. This means it is a mixture of liquid and vapor, not fully subcooled. Subcooling refers to the cooling of a liquid below its saturation temperature at a given pressure, which is not the condition of the refrigerant entering the evaporator in a DX system.

In contrast, the other statements accurately reflect the functioning of DX systems. Liquid refrigerant does boil in the evaporator, which is essential for absorbing heat. As it boils, it changes to vapor before exiting the evaporator, ensuring efficient heat transfer. Furthermore, upon passing through the expansion valve, a portion of the refrigerant does flash into vapor, which allows for the necessary drop in pressure and temperature that facilitates the absorption of heat in the evaporator.