# Template:HXSizeCalc Theory

(2) $\displaystyle{ \mathbf{\mathit{Q=UA\boldsymbol{\Delta}T_{LM}}} }$
$\displaystyle{ \mathbf{\mathit{\boldsymbol{\Delta}T_{LM} = \cfrac{\Delta T_2 -\Delta T_1}{ln \left( \cfrac{\Delta T_2}{\Delta T_1} \right) }}} }$ - Log Mean Temperature Difference (LMTD)
For Counter Current Flow $\displaystyle{ \; \Delta T_2 = T_{H_{in}} - T_{C_{out}} \quad }$ and $\displaystyle{ \; \Delta T_1 = T_{H_{out}} - T_{C_{in}} }$