Abstract: A method of determining an aperture area of a nozzle hole in a droplet jet device including a flow channel through which a liquid flows and the nozzle hole configured to spray the liquid, the method including determining the aperture area [m2] of the nozzle hole so that a jet flow of the liquid sprayed from the nozzle hole is fragmented into droplets, the liquid having a value of ?0.45/? determined from a density [kg/m3] of the liquid and a surface tension [N/m] of the liquid in a range no lower than 300 and no higher than 900, and a kinematic viscosity coefficient [m2/s] of the liquid in a range no lower than 1.0E-6 and no higher than 2.0E-5.

Abstract: A droplet jet device configured to form a liquid into droplets to jet the droplets, the droplet jet device including a main body having a flow channel through which the liquid circulates, and a jet nozzle having at least one nozzle hole and spraying the liquid from the nozzle hole, wherein defining the number of the nozzle holes as N, a diameter of the nozzle hole as r [m], and a contour length of a cross-sectional surface of the flow channel as L [m], the following formula is fulfilled. 0.188 < 1 N 2 · L 2 r 3 < 1.