In a parallel-flow heat exchanger, hot water enters at $80^\circ\text{C}$ and exits at $50^\circ\text{C}$, while cold water enters at $20^\circ\text{C}$ and exits at $40^\circ\text{C}$. Calculate the temperature difference at the exit $\Delta T_2$ in $^\circ\text{C}$.
Answer Key:
10
Step-by-Step Solution & Explanation
In parallel flow, fluids travel in the same direction:
At entrance: $\Delta T_1 = T_{h,\text{in}} - T_{c,\text{in}} = 80 - 20 = 60^\circ\text{C}$.
At exit: $\Delta T_2 = T_{h,\text{out}} - T_{c,\text{out}} = 50 - 40 = 10.0^\circ\text{C}$.