ANS:A - approach.

The terminal point temperature difference between fluids in a heat exchanger is termed as the "approach." Explanation:

• The approach temperature refers to the temperature difference between the outlet temperature of one fluid stream and the inlet temperature of the other fluid stream at the terminal point of a heat exchanger.
• It indicates how closely the outlet temperature of one fluid approaches the inlet temperature of the other fluid, representing the efficiency of heat transfer in the exchanger.
• A smaller approach temperature signifies more effective heat transfer between the fluids.
• The approach temperature is an important parameter in heat exchanger design and operation, as it directly affects the thermal performance and energy efficiency of the system.

• The log mean temperature difference (LMTD) is used to calculate the overall temperature driving force for heat transfer in a heat exchanger.
• The arithmetic mean temperature difference and geometric mean temperature difference are not commonly used terms in the context of heat exchanger analysis and design.