PEX pipe from Achermann and Zweifel (2003).
Achermann, Matthias and Gerhard Zweifel. RADTEST - Radiant Heating and Cooling Test Cases. A Report of Task 22, Subtask C, Building Energy Analysis Tools Comparative Evaluation Tests. Luzern, Switzerland. April 2003.
record PEX_RADTEST = Buildings.Fluid.Data.Pipes.Generic(dOut = 0.025, dIn = 0.020, roughness = 0.007E-3, d = 983, k = 0.35);