Consideration of fouling by scaling in the sizing of flat plate solar collector networks

Abstract

In this work, the effects of fouling on the performance of flat plate solar collector networks that operate with water as the thermal fluid are studied, and design considerations are put forward to be used in the sizing of these systems from the thermal and hydraulic points of view. The quantification of the effects produced by scaling is carried out through a mathematical model that predicts the deposition on the walls of the tubes. The model considers that CaCO3 is the only compound present in the fouling layer. Results indicate that for a volumetric flow rate of 3.78 l/min and assuming a CaCO3 concentration of 250 ppm, in a period of six months, the maximum outlet temperature that can be obtained in a day falls 1.5 °C and the pressure drop increases four times. It is shown that it is advisable to design a network of solar collectors considering scaling. The case study indicates that to supply a total flow rate of 48 l/min at a temperature of 70 °C, the design considering scaling requires 220 collectors and a volumetric flow rate of 4.8 l/min per line with a total annualized operating cost of $343,300 Mx.