Heat exchange – With coated – roughened or polished surface
Reexamination Certificate
2001-07-10
2002-12-03
Bennett, Henry (Department: 3743)
Heat exchange
With coated, roughened or polished surface
C165S177000, C029S890053
Reexamination Certificate
active
06488079
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to heat exchanger tubing. The present invention also generally relates to corrugated tubing having textured internal and external surfaces. The corrugated tubing may have linear or helical corrugations.
2. Description of Related Art
A heat exchanger tube may be used in a process that transfers heat between a first fluid inside the heat exchanger tube and a second fluid outside of the heat exchanger tube. The efficiency of heat transfer between the first fluid and the second fluid may be a complicated function that depends on the characteristics of the fluids, on the characteristics of the heat exchanger tube, and on the characteristics of fluid movement relative to the heat exchanger tube. The term “fluid” refers to a liquid, a gas, or a combination of a liquid and a gas. A heat exchanger tube may also be used to transfer heat between a fluid and a solid. The solid may be located inside or outside of the tube.
Each end of a tube may be pointed. A pointed tube may have reduced diameter cylindrical portions at each end of the tube that transition to a larger diameter main body section of the tube. Pointed tube ends may facilitate attachment of the tube to support structures. The support structures may be tube sheets of a heat exchanger. Tube sheets may support several tubes within a shell of a tube-and-shell heat exchanger. Fluid that is directed past outside surfaces of tubes of a tube-and-shell heat exchanger may flow in a direction that is substantially coaxial to a longitudinal axis of the shell of the heat exchanger. Tubes having pointed ends may be easier to position and seal to support structures than are tubes that do not have pointed ends. U.S. Pat. No. 5,311,661, which issued to Zifferer and which is incorporated by reference as if fully set forth herein, describes an apparatus that may be used to form heat exchanger tubes having pointed ends.
It is desirable to maximize the heat transfer rate across a wall of a tube of a heat exchanger. Increasing the surface area of a tube may increase the heat transfer rate across the tube. Also, directing fluid flow past and through a tube in desired fluid flow patterns may increase the heat transfer rate across the tube.
One method of increasing the surface area of a tube is to attach fins to an outer surface of the tube. Fins may be attached to a tube after the tube is formed, or fins may be formed in the outer surface of the tube. Fins may be formed on the outer surface of a tube by a finning tool of a finning machine. A finning tool typically includes three or four disks mounted on an arbor. The disks form a spiraled flight of fins on an outer surface of a tube during use. The fins formed by a finning tool may have heights that are greater than about 30 mils (0.030 inches). Generally, the fins formed by a finning tool are oriented substantially perpendicular to the longitudinal axis of the tube. A small amount of skew from a true perpendicular orientation allows the finning tool to provide a driving force to the tube that moves the tube through the finning machine.
Fins may be oriented substantially perpendicular to a longitudinal axis of the tube, or the fins may be oriented substantially parallel to the longitudinal axis of the tube. Fins on an outer surface of a tube that are substantially perpendicular to a longitudinal axis of the tube may be used in heat transfer applications where fluid flow is directed substantially perpendicular to the longitudinal axis of the tube. Heat exchanger tubes of condensers and evaporators may be finned tubes wherein the fins are oriented substantially perpendicular to longitudinal axes of the tubes. Fins that are oriented substantially parallel to a longitudinal axis of a tube may be used in heat transfer applications where fluid flow is directed substantially coaxial to the longitudinal axis of the tube. Tubes having fins that are oriented substantially parallel to longitudinal axes of the tubes may be used in tube and shell heat exchangers.
Fins on an outer surface of a tube may promote the development of areas that have little or no fluid movement when fluid flows by the tube. Such areas may develop on a side of a fin that is opposite to a direction of fluid flow past the tube if the fins of the tube are not oriented to allow fluid to flow adjacent to the tube. Such stagnant areas may decrease the heat transfer efficiency of a tube. Such stagnant areas may promote charring or thermal degradation of a heat transfer fluid.
Another method of increasing the surface area of a heat exchanger tube is to texture the inner surface of the tube. A knurling tool may be used to form a groove and rib pattern on an inner surface of a tube. The knurling tool may be placed within the tube. Force may be applied to an outer surface of the tube to press the inner surface of the tube against the knurling tool. Pressing the inner surface of the tube against the knurling tool forms a knurl pattern on the inner surface of the tube.
A finning tool and a knurling tool may be used in combination to form a tube that has a finned outer surface and a knurled inner surface. U.S. Pat. No. 4,886,830, which issued to Zohler and which is incorporated by reference as if fully set forth herein, describes a method of forming a tube that has a finned outer surface and a knurled inner surface.
An alternate method of texturing a tube is to form a desired pattern of ribs and grooves on surfaces of a flat metal plate. The plate may then be rolled into a cylindrical shape. A weld may be formed to join the ends of the plate together and form a tube. U.S. Pat. No. 5,388,329, which issued to Randlett et al., describes a method of manufacturing an extended surface heat exchanger tube using a rolled and welded metal plate.
Another method that may be used to increase the surface area of a tube is to corrugate or convolute the tube. The corrugations may be linear corrugations or helical corrugations. Linear corrugations may be formed in a tube by passing the tube through a corrugating die. The corrugating die may have angularly spaced die teeth that are positioned and shaped to progressively indent the wall of the tube at equally spaced points around the tube. U.S. Pat. No. 5,311,661 describes a system for forming linearly corrugated heat exchanger tubing.
Helical corrugations or convolutions may be formed in a tube by passing the tube through a corrugating die. A die and machinery used to produce a helically corrugated tube may be substantially the same as shown in U.S. Pat. Nos. 4,377,083, which issued to Dale et al.; 4,514,997, which issued to Zifferer; 5,409,057, which issued to Zifferer; and 5,551,504, which issued to Zifferer. Each of these patents is incorporated by reference as if fully set forth herein. Another method of forming helical corrugations in a heat exchanger tube is to heat and twist the tube as described in U.S. Pat. No. 4,437,329, which issued to Geppelt et al.
A heat transfer rate across a tube may be increased by directing fluid flow in a desired flow patterns through and by the tube. A desired flow pattern may increase internal mixing of a heat exchange fluid. A desired flow pattern may promote non-laminar fluid flow of one or both of the heat exchange fluids that flow by and through the tube. In a straight, smooth-walled cylindrical tube, fluid may flow past or through the tube in a laminar flow pattern. Laminar fluid flow may develop a boundary layer at a wall of the heat exchanger tube. The boundary layer may inhibit heat transfer throughout the fluid. Non-laminar fluid flow may minimize the formation of a boundary layer and promote internal mixing of the fluid so that heat transfer takes place throughout the fluid.
One method that may be used to obtain a desired fluid flow pattern is to change the geometrical configuration of the surfaces of a heat exchanger tube. The geometrical configuration of the surfaces of a heat exchanger tube may be changed by texturing the surfaces of the tube. Texturing the surfaces of the
Bennett Henry
Meyertons Erik B.
Packless Metal Hose Inc.
LandOfFree
Corrugated heat exchanger element having grooved inner and... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Corrugated heat exchanger element having grooved inner and..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Corrugated heat exchanger element having grooved inner and... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2987314