Heat and Mass Transfer in Food Processing

In a counter-flow heat exchanger, the Logarithmic Mean Temperature Difference (LMTD) is defined as:

Options:

• (A) $\Delta T_{lm} = \frac{\Delta T_1 - \Delta T_2}{\ln(\Delta T_1 / \Delta T_2)}$
• (B) $\Delta T_{lm} = \frac{\Delta T_1 + \Delta T_2}{2}$
• (C) $\Delta T_{lm} = \sqrt{\Delta T_1 \Delta T_2}$
• (D) $\Delta T_{lm} = \Delta T_1 - \Delta T_2$