Roughness coefficient of a highly calcinated penstock

Abstract

When highly calcinated water is transferred through the penstock of a hydropower plant it leaves a residue on the pipe surface. Accumulated residue over time causes a change in the roughness of the pipe surface thus leads to friction losses in the system. The effect is a change in head and discharge relation for the turbines. A multimethodology is proposed for determining the apparent surface roughness value (ε) by means of friction factor f and measuring arithmetic mean deviation of the roughness profile (Ra), root mean square roughness (Rq) and peak and valley roughness (Rz). It is found that a surface roughness value (ε) of 0.3mm can be used for calcinated surfaces which is much higher than steel surfaces but smaller than a concrete surface.