Experimental study on the influence of operating parameters of plug flow on thermal efficiency of direct absorption solar collector with Fe3O4 nanofluid

In this paper, the influence of operating parameters of plug flow on thermal efficiency of direct absorption solar collector (DASC) using Fe3O4 nanofluid (0.05-0.2 wt%) was experimentally studied, the DASC is a device that directly converts sunlight into heat by using a working fluid with high thermal conductivity. As a result, the outlet temperature and efficiency of DASC was affected by the ratio of length of liquid plug to the inner diameter of the tube, the working time of air compressor, the mass flow rate, the inlet temperature, solar radiation and concentration of the Fe3O4 nanofluid. When the plug flow mode was implemented, the energy gained and stored exhibited a notable enhancement compared to the regular flow mode. Furthermore, the DASC exhibited the highest efficiency when the L/D were 1.7 which was 27.7 % higher than that of regular flow mode. In addition, the inlet temperature was inversely proportional to the efficiency cause the heat loss to the environment.The maximum performance of the direct absorption solar collector was obtained when 0.1 wt% Fe3O4 nanofluid was used as the working fluid with plug flow mode.