An improved design method for solar water heating systems

In this paper, the $\text{Φ}$,f-chart method is extended to open-loop solar hot water heating systems. This method is an improvement over the f-chart method since it does not impose any restrictions on the water set temperature, water mains temperature, or the preheat tank loss coefficient. The procedure is general for both one-tank and two-tank systems. The modified $\text{Φ}$,f-chart method is still applicable to the closed-loop systems for which it was originally developed.