Dear David, I have a question about TYPE524. The TESS manual says, if par15, HX geometry, is 1, users must set the HX fractions from par16 to par(16+par(16)). But refer to the fortran code, it seems to be set from par17(as Heat fxchanger fluid) to par30(as HX cross sectional area) and HX fractions is set from par(31) to par(30+par(31)). Isn't my library manual is the latest? Mika