Spiral fluted tube

Introduction

 

Spiral fluted tube is produced by rolling on outer surface of round tube. The mechanical process will create spiral grooves outside and spiral ribs inside. It is high efficiency heat transfer tube with enhanced performance.Parameters to define spiral fluted tube include inner diameter, tube thickness, pitch, flute numbers & depth & radius. It could be single flute or multiple flutes (commonly 4, 6, 8) as per client requirement.

 

Material

 

Now we can fabricate spiral fluted tube of aluminum, copper, stainless steel, carbon steel.

 

Working principle

 

When flowing inside tube, fluid is guided by spiral groove. The part close to tube wall swirls along adjacent ribs. This is conducive to reduce thickness of boundary layer. And the other part will generate periodical turbulence when flowing in axial direction. Both effects will enhance heat transfer inside tube. Enhancement outside of tube is mainly embodies in condensation process. Spiral groove can be the pass to drain condensate during phase change. Thickness of condensate film is reduced to decrease thermal resistance. Spiral fluted tube coefficient of heat transfer is 70% higher than bare tube, and it has excellent anti-fouling performance.

 

Application in thermal power plant

 

Air preheater is major equipment for power generation. Two types are used: rotary air preheater and tubular air preheater. Rotary air preheater has higher heat transfer coefficient and compact size, but air leakage and soot fouling is a big problem.

 

Air preheater made of bare tube also has disadvantages. Its size is larger because bigger heat transfer area is required due to lower coefficient. And dew point corrosion happens at cold end.

 

Spiral fluted tube is considered as excellent element for enhanced heat transfer. So it is widely used for fabrication of tubular air preheater. In practice, ubular air preheater made of spiral fluted tube has made obvious achievement in reduction of exhaust gas temperature, increase of tube wall temperature at cold end, relieving soot fouling, etc.