Heat and Mass Transfer in Food Processing

In a milk pasteurizer heat exchanger, the terminal temperature differences at the two ends are $\Delta T_1 = 40^\circ\text{C}$ and $\Delta T_2 = 10^\circ\text{C}$. Given $\ln(40/10) = \ln(4) \approx 1.3863$, the LMTD $\Delta T_{lm} = \frac{40 - 10}{1.3863} = \frac{30}{1.3863}$ in $^\circ\text{C}$ is (rounded off to one decimal place):