Fan and shroud assembly

1. A fan and shroud assembly comprising:

a fan having a hub rotatable on a shaft and a plurality of blades extending outward from the hub, the blades having ends remote from the hub connected to each other; and

a shroud surrounding the fan for controlling air blast resulting from rotation of the fan,

wherein the shroud comprises: a guide ring part spaced at a predetermined distance from the periphery of the fan; and swirl preventing means of a round-corrugation type formed on the guide ring part for preventing swirling airflow along the periphery of the fan, wherein the swirl preventing means comprises round furrows, each having a predetermined radius of curvature at a portion which is depressed in a radial direction and round projections, each having a predetermined radius of curvature at a portion which projects toward a central direction of the shroud, the round furrows and the round projections being repeatedly arranged, wherein the round furrows and the round projections are inter-connected with each other continuously such that when inter-connecting the circular arcs of the round furrows with the circular arcs of the round projections along a circumferential direction, there is not a straight line section, and the round furrows each have a diameter D different from a diameter d of each round projection.

2. The fan and shroud assembly according to claim 1 , wherein the diameter of each of the round furrows is in the range of 5.0 mm˜30.0 mm.

3. The fan and shroud assembly according to claim 1 , wherein the swirl preventing means is formed along the periphery of the guide ring part, and the number of the round furrows is in the range of 20˜60.

4. The fan and shroud assembly according to claim 1 , wherein the fan further comprises a band connecting the ends of the blades.