Which statement about double tube refrigeration condensers is true?

The statement about double tube refrigeration condensers that holds true is that water flows in the inner tube in the opposite direction of the flow of refrigerant. This design is known as a counterflow configuration, which enhances heat exchange efficiency. By having the water and refrigerant flow in opposite directions, the temperature differential between the two fluids is maximized along the length of the condenser. This results in more effective cooling of the refrigerant, as warmer refrigerant enters the condenser at the same end where cooler water is flowing in. This principle aids in achieving optimal heat transfer and overall performance of the condenser.

In contrast, the other options do not accurately reflect the characteristics of double tube condensers. They may suggest alternative configurations or attributes that don't align with the operational principles and benefits associated with this type of condenser. The design and functionality focus on maximizing thermal efficiency, which is achieved primarily through the counterflow arrangement of the fluids.