The thermal expansion reference number is a value that points to or corresponds to a set of data set forth in ASME Section II Part D, tables TE-1, 2 and so on. Unfortunately, many materials have a composition or UNS number that does not match the criteria of what is supplied in the ASME Code. In these cases, the reference number will be brought in as zero. If this happens, you will need to enter in an appropriate value. Thermal expansion coefficients are important especially if you are analyzing a heat exchanger.