INVESTIGATION OF FLOW DISTRIBUTION IN SOLAR COLLECTOR ARRAYS

ABSTRACT The flow distribution in the vertical risers of collector arrays in which the headers are connected in series is not uniform. The flowrate in the center of the array is lowest and approaches zero in larger arrays. To investigate this phenomena, a theoretical model was developed calculating the distribution of flow in piping grids used in solar collector arrays. Experimental verification of this model was performed by measuring the flow distribution in the riser pipes along the entire header length. Recommendations are included on the sizing of the headers for collector arrays ranging from single panel to the maximum number of panels which could be reasonably be supplied by a specific header size. Riser sizes of 1/4″ to 1/2″ diameter and header sizes of 1/2″ to 2″ diameter were considered. Experiments were done with water and with glycol (50/50%) at ambient temperatures. Smaller risers allow for a longer collector array with a constant header diameter.