Coiled system for condensational growth of ultrafine particles

A method of enlarging particles by water condensation comprising:

• providing a tube having an interior surface having an input adapted to receive a flow and an output, the tube having at least a first longitudinal section and a second longitudinal section between the input and the output, at least the first longitudinal section of the tube formed as a coil, the coil having a first diameter and the interior surface having a second diameter;
• wetting the interior surface with condensable fluid throughout the tube;
• maintaining the interior surface of the first longitudinal section at a first temperature T1;
• maintaining a portion of the interior surface of the second longitudinal section at a temperature T2;
• and
• introducing the flow into an interior of the tube at the input at a flow rate, the flow moving toward the output and through at least the first and second longitudinal sections, the flow rate, the first diameter and the second diameter selected in combination to create a non-turbulent flow such that the Reynolds number is below 2000 and the Dean's number is above zero.