Abstract: A hydrofoil impeller includes a central hub connected to a shaft, and being in the form of a flat plate and being perpendicular to the central axis. The central hub has first bolt holes arranged to form a pattern, the number of groups of first bolt holes corresponding to a number of blades attached to the central hub. At least three blades extend radially outwardly from the central hub, and have a group of second bolt holes arranged in a corresponding pattern to the first bolt holes so that the group of second bolt holes can be aligned with the group of first bolt holes and bolts can be placed through the first and second bolt holes to form bolted joints. The pattern in which the first holes and second holes are arranged in each of the respective groups of holes has a form of a closed curved shape.

Abstract: A hydrofoil impeller includes a central hub connected to a shaft, and being in the form of a flat plate and being perpendicular to the central axis. The central hub has first bolt holes arranged to form a pattern, the number of groups of first bolt holes corresponding to a number of blades attached to the central hub. At least three blades extend radially outwardly from the central hub, and have a group of second bolt holes arranged in a corresponding pattern to the first bolt holes so that the group of second bolt holes can be aligned with the group of first bolt holes and bolts can be placed through the first and second bolt holes to form bolted joints. The pattern in which the first holes and second holes are arranged in each of the respective groups of holes has a form of a closed curved shape.

Abstract: A hydrofoil impeller wherein the tip edge is straight and has a right angle with a radius extending from the central axis to the tip edge. In the central hub and in each of the blades the number of holes in each group of first and second holes is at least five. The pattern in which the holes are arranged in each of the respective groups of holes is elliptical having a center and a major axis which is substantially parallel to the radius and placed at a distance therefrom. The leading edge is, in the direction of rotation, behind an imaginary radial line intersecting the central axis of the shaft and the center of the ellipse, the leading edge being at an angle of 50°±2° in relation to the radial line. The area of the blade is divided into four planar portions by three straight bends.

Abstract: A hydrofoil impeller wherein the tip edge is straight and has a right angle with a radius extending from the central axis to the tip edge. In the central hub and in each of the blades the number of holes in each group of first and second holes is at least five. The pattern in which the holes are arranged in each of the respective groups of holes is elliptical having a center and a major axis which is substantially parallel to the radius and placed at a distance therefrom. The leading edge is, in the direction to rotation, behind an imaginary radial line intersecting the central axis of the shaft and the center of the ellipse, said leading edge being at an angle of 58°±2° in relation to the radial line. The area of the blade is divided into four planar portions by three straight bends.

Abstract: The invention relates to cooling equipment for cooling liquid, comprising a cooling tower that is mainly cylindrical in the vertical direction, in which case the cooling air feed equipment and the exhaust air discharge equipment are arranged, with respect to the cooling tower, so that both the cooling air flowing direction from the inlet aperture to the cooling space and the exhaust air flowing direction from the discharge equipment is horizontal and parallel to the tangent of the outer surface of the cooling tower. The invention also relates to a method for cooling liquid.