How is the difference in thermal expansion managed between the glass and the heat exchanger on the Wave panel?
The material of the heat exchanger is a grade of ferritic stainless steel whose coefficient of thermal expansion is very close to that of glass. Over the length of a Wave panel (1677 mm), the differential expansion between the glass and the stainless steel is 0.314 mm for a temperature variation of -20°C to 75°C.
After conducting thermal cycling tests, we have determined that this small difference is insignificant for the DualSun Wave panel. The results of the cycling proved the compatibility of the two materials.
Clarification: On the DualSun Wave panel, we use a ferritic stainless steel of the K44 grade of Aperam. It quickly became clear this was the best choice due to its robust mechanical properties and its low differential expansion relative to glass.