In this study, the performance of vacuum tube collectors includes three different absorbent tubes was investigated experimentally for four-volume flow rates of 10, 20, 30 and 40 l/h. Absorbent tubes are helical coil, spiral tube, and U-tube that are placed in a vacuum tube solar collector. Absorbent tubes are arranged in such a way that the working fluid volume is the same. All three types of absorbent tubes were tested on different days simultaneously. The purpose of this research is to investigate the effect of absorbent tube arrangement on the storage of thermal energy. The results showed that the thermal performance of vacuum tube collectors increases with the volumetric flow rate of the tubes for all cases. In addition, the helical coil collector has a better performance than other ones. (C) 2019 Elsevier Ltd. All rights reserved.