Consider a heat exchanger that has an NTU of 4. Someone proposes to double the size of the heat exchanger and thus double the NTU to 8 in order to increase the effectiveness of the heat exchanger and thus save energy. Will this proposal save energy to a larger extent

The proposal will not save energy to a large extent

Explanation:

NTU stands for Nephelometric Turbidity Unit.

For NTU values less than 1.5 (i.e. smaller NTU values), an increase in NTU values greatly increases effectiveness (and thus saves energy).

In contrast, for higher NTU values, increase in the value of NTU does not have a significant contribution to effectiveness of the system. Large increase in the NTU values only translate to a small increase in effectiveness.

The initial NTU of the heat exchanger under consideration is 4, which is a relatively large NTU value, a doubling of this NTU value to 8 will not cause any significant increase in the effectiveness of the system, hence will not have much impact on the amount of energy saved.