Which of the following is NOT a type of defrost design used in industrial refrigeration?

Mechanical compression is indeed not classified as a type of defrost design used in industrial refrigeration. Generally, defrost systems are employed to remove accumulated frost or ice from evaporators to maintain efficiency and performance. The typical methods include air, water, and cool gas defrost, which specifically cater to different operational scenarios and equipment.

Air defrost typically involves using warm air to melt frost, while water defrost utilizes heated water to achieve the same effect. Cool gas defrost relies on circulating gas from the compressor to warm up the evaporator surfaces. In contrast, mechanical compression refers to the standard process of compressing the refrigerant within the refrigeration cycle and is not designed for defrosting purposes. Thus, it does not fit within the category of defrost methods commonly used in the industry.