Fan duct combination unit

In a cross flow type fan for moving gases having an exhaust volume output to fan rpm relationship which is substantially linear over the fan operating range and exhaust duct combination having a fan with a plurality of end disks, the improvement comprising:

• an intake duct having
• an upper surface which curves downwardly toward the fan at substantially the same curvature as the curvature of the impeller blades at the point of closest approach to a location proximate to the upper surface of the fan just anterior to the point that there is substantially increasing power requirement combined with a substantial reduction in exhaust gas velocity and a lower surface that is positioned proximate to the fan at the point of an increase in the intake gas pressure external to the fan,
• an exhaust duct offset from the intake duct having an upper surface location adjacent to and below the point of a substantial drop in exhaust gas velocity and a lower surface location where the lower surface curves under and remains substantially separated from the fan to a point where the exhaust gas flow through the fan's blades approaches linearity with the curvature of the lower surface of the duct adjacent to the fan and
• a cross flow type fan having no internal vortex reducing mechanism and forward facing blades having an inner surface curvature of about 65° to about 80° and the inner surface of the outer ends of the blades is angled at about 30° to 34° from the vertical.

In a cross flow type fan for moving gases having an exhaust gas speed to blade tip speed relationship which is substantially linear, an intake duct and exhaust duct combination having a fan with a plurality of end disks and a greater plurality of impeller blades comprising:

• an intake duct having an upper surface which curves downwardly toward the fan at substantially the same curvature as the curvature of the impeller blades to a location proximate to the upper surface of the fan just lower than the point that there is an increasing power requirement combined with a substantial reduction in exhaust gas velocity and a lower surface that is positioned proximate to the fan substantially at the point of an increase in the intake gas pressure external to the fan,
• an exhaust duct offset from the intake duct having an upper surface location adjacent and below the point of a substantial drop in exhaust gas velocity and a lower surface location at the point where the lower surface curves under the fan to a point where the exhaust gas flow through the fan's blades approaches substantial linearity with the curvature of the lower surface of the duct adjacent to the fan and
• a cross flow type fan having no internal vortex reducing mechanism, forward facing blades with an inner surface curvature of about 65° to about 80° and the inner surface of the outer ends of the blades is angled at about 30° to 34° from the vertical.