This Demonstration calculates and plots the heat flow,

(in watts/

), through a heat exchanger's wall of a chosen thickness,

(in mm), and thermal conductivity,

(in watts/m °C), with chosen surface heat transfer coefficients at either side of the wall,

and

(in watts/

°C), and logarithmic mean temperature difference, Δ

(in °C), between them. Since the heat transfer coefficients can vary over a very large range, the

and

parameters can be specified as being high or low using a setter bar. The calculations are done using the equation

, whose parameters can be modified by moving sliders. The red dot on the plot marks the heat flow per unit area for a Δ

chosen by moving the top slider. The top graphic depicts the heat resistances as a schematic diagram (not to scale).