For a heat exchanger, $\triangle T_{\text{max}}$ is the maximum temperature difference and $\triangle T_{\text{min}}$ is the minimum temperature difference between the two fluids. LMTD is the log mean temperature difference. $C_{\text{min}}$ and $C_{\text{max}}$ are the minimum and the maximum heat capacity rates. The maximum possible heat transfer $(Q_{\text{max}})$ between the two fluids is
- $C_{\text{min}} \text{ LMTD}$
- $C_{\text{min}} \triangle T_{\text{max}}$
- $C_{\text{max}} \triangle T_{\text{max}}$
- $C_{\text{max}} \triangle T_{\text{min}}$