Optimal Geometric Configuration for a Natural Circulation Loop

An optimal geometrical configuration that results in a maximum loop flow rate at given volume constraints is investigated for a two-phase natural circulation loop and a single-phase natural circulation loop. A rectangular loop connected with pipes is considered, which consists of a heater, a cooler, a riser, and a downcomer. By varying the aspect ratio of the loop, the number of pipes in the heating and cooling sections, and the distribution of the volumes between the cold side and the hot side, an optimal loop configuration that results in a maximum loop flow rate is determined from an analytical solution using simplifying assumptions. It is shown that the optimal configuration is beneficial in terms of minimizing the temperature rise and the pressure rise at given heat input. To support the argument, a complementary numerical analysis for a two-phase natural circulation flow in a rectangular loop is performed. The results are in good agreement with those predicted by the analytical models.