Schematic diagram of the test rig.

Schematic diagram of the test rig. 1 – valve; 2 – water supply tube; 3 – tank-accumulator; 4 – stop valve; 5, 8 – drain valves; 6 – downflow tube; 7 –
solar collector; 9 – upflow pipe; 10 – scaled glass tube; 11 – dosing unit; 12 – stopwatch; 13 – control panel; 14 – pyrometer; 15 – anemometer;
C1 – C24 – temperature measurement points