An empirical and theoretical investigation was achieved on a cylindrical storage collector. It was suggested in this work for a cylinder to be cut at an inclined cutting plane. The tests were achieved for both summer and winter climate conditions with and without hot water removal. The hourly system performance parameters were investigated systematically for different experiments. These included the average storage temperature, velocity distribution, and temperature distribution.

In the cylindrical collector, the ultimate magnitude of the average storage temperature was 25 °C, while the maximum temperature at the tip of the cylindrical collector was 58 °C for a typical spring day. Meanwhile, the rectangular collector can warm up the stored water to a temperature of 23 °C, when the inlet water temperature was 12 °C. The performance of the new solar collector was, in general, similar to the performance of the conventional thermosyphon flat plate solar water heaters.

The Fluent program was used to confirm the experimental results. The free convection in the cylindrical collector was investigated based on the method of control volume. From the Fluent data and analysis of the collector, the temperature and velocity distributions throughout the day were obtained. The Fluent program data was well compatible with the experimental results.