Dairy Unit Operations

In an HTST milk pasteurizer, raw milk enters at $4^\circ\text{C}$ and is heated to $68^\circ\text{C}$ solely in the regeneration section by returning pasteurized milk that enters at $72^\circ\text{C}$. Total heating required from raw to pasteurization temperature is from $4^\circ\text{C}$ to $72^\circ\text{C}$ ($68^\circ\text{C}$ rise). The regeneration efficiency (in %) is: (using $\eta_{reg} = \frac{68 - 4}{72 - 4} \times 100$)