2018-09-10, Eismann, Ralph, Haeberle, Andreas

Efficiency, cost-effectiveness and operational safety of solar plants must be based on the knowledge of pressure loss as well as flow distribution and temperature distribution of branched collector arrays. Therefore, pipe network analysis is an essential step during the dimensioning process. This article presents an explicit, fast converging numerical scheme especially suited for collector fields. The effect of pipe dimensions and pipe routing on flow, temperature and pressure-distribution and collector field efficiency is demonstrated by application of a dedicated software tool, which is provided as an open source code.

2018-04-11, Eismann, Ralph, Adams, Robert

Convergence of numerical schemes for pipe network analysis requires continuous modelling of pressure losses in the transition region between laminar and turbulent regions. Several existing correlations for the friction factor of straight pipes and helical tubes are presented. Based on these correlations a new explicit correlation for helical tubes with arbitrary surface roughness is derived. The friction factor is expressed as a continuous function of the Reynolds number covering laminar, transitional, and turbulent flow regions. Potential sources of error are also discussed, including the effects of tube deformation caused by the bending process.