If an evaporator's defrost design method fails, what is the next best method for defrosting?

In situations where an evaporator's defrost design method fails, it is crucial to choose a method that ensures safety and effectiveness in removing ice or frost build-up without damaging the equipment. The option of using "None of these" implies that the methods listed are not suitable or safe to use for defrosting.

Using hot water, while it may seem like an intuitive solution, can introduce risks such as thermal shock to the evaporator components or the potential for water damage. A chipping hammer could also lead to physical damage to the evaporator's surface, and an open flame poses a serious safety hazard that could damage the unit or create a fire risk.

Consequently, the best practice would be to employ manufacturer-recommended methods for defrosting commensurate with the specific cooling system's design. If the primary method fails, it would be prudent to consult operational protocols or maintenance guidelines, rather than resorting to the options provided. Thus, recognizing that "None of these" is the best choice emphasizes the importance of sticking with safe and appropriate practices for equipment maintenance and avoiding methods that could lead to damage or dangerous situations.