US20110240266A1

US20110240266A1 - Helicoid turbulator for heat exchangers

Info

Publication number: US20110240266A1
Application number: US12/754,307
Authority: US
Inventors: Bryan C. Holland; Jack C. Holland
Original assignee: HEAT EXCHANGER TECHNOLOGY LLC
Current assignee: HEAT EXCHANGER TECHNOLOGY LLC
Priority date: 2010-04-05
Filing date: 2010-04-05
Publication date: 2011-10-06

Abstract

The present invention teaches an assembly for improved heat transfer consisting of a helix surrounding a self contained tube that is placed inside a heat exchanger tube parallel to fluid flow with the outside of the helix in close proximity to the inside wall of the heat exchanger tube and the invention assembly self contained tube in close proximity to the inside of the helix.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to heat exchangers for improved heat transfer along the path of fluid flow. More specifically, the present invention relates to an improved heat exchanger comprising a turbulator for transferring heat from a viscous fluid flowing in a laminar state.
2. Description of the Prior Art
Generally, heat exchangers that utilize round tubes connected in plurality and surrounded in a secondary enclosure with captivated fluids on both sides of the tubes are referred to as Shell and Tube Exchangers. Air Cooled Exchangers utilize extended surfaces on the outside of the tubes for forced air convection. Double Pipe Exchangers consist of a single heat exchanger tube enclosed with another larger tube with isolation to provide for captivated fluids on both sides of the tubes.
The velocity characteristics of fluids moving through tubes in heat exchangers and the fluid condition thereof have a velocity component known as the Reynold's Number. The Reynold's Number is determined by the fluid velocity, the fluid mass, the fluid viscosity, and other properties. Generally, fluid flow is laminar if the Reynold's Number is below 2000, is in transition of becoming turbulent when the Reynold's Number is between 2000 and 8,000, and is normally turbulent above 8000. When fluid flow inside the heat exchanger tube is laminar, the fluid moves through the tube in layers, unmixed, and that portion of the fluid that is in contact with the tube wall stagnates at a lower flow velocity providing an insulation effect retarding heat transfer from the center and surrounding volume of the flowing fluid to the heat exchanger tube interior wall. Conversely, when the flow reaches a higher Reynold's Number and becomes turbulent, that portion of the fluid in contact with the tube wall is continuously displaced which reduces the tube wall stagnation and provides higher heat transfer rates.
The basic underlying principle behind how a turbulator works is the first law of thermodynamics, which is the application of the conservation of energy principle applied to the heat and thermodynamic process. The first law of thermodynamics states that the change in internal energy of a system (ΔU) is equal to the heat added to the system (Q) plus the work done to the system (W) or ΔU=Q+W. For turbulator design, the work done to the system (W) is the allowable pressure drop, and the change in internal energy (ΔU) of the system is the amount of heat transfer. The laminar flow issue mentioned above has a long history of improvement efforts by those skilled in the art of fluid flow and heat transfer. In 1906 a twisted ribbon device placed inside a housing captivating fluid flow was awarded a patent (U.S. Pat. No. 808,752) and was perhaps the first recorded effort to improve fluid flow heat transfer by creating a swirl fluid flow and increased fluid velocities with a finite work input. There have been numerous patents granted, as noted under “References Cited”, covering a variety of modifications to twisted ribbons such as scoops along the body of the twisted ribbon, discontinuous outer edges, pleats, and others. These variations to twisted ribbons have merit for fluids with characteristics that permit the fluids to become turbulent with an increase in work, W (pressure drop), but serve little useful purpose for viscous fluids that flow in a laminar fashion as they consume the input work in the form of pressure drop with no appreciable change to the energy of the system, ΔU (heat transfer).
When laminar fluid flows unobstructed through a heat exchanger tube, the portion of the fluid the greatest distance from the inner wall of said tube experiences the least heat transfer. This is because the layers created by the laminar flow insulate the layers and the farther the layers are from the heat exchanger tube wall the less heat transfer occurs. Reducing the tube size, with constant fluid flow velocity, reduces the thickness of the insulating layers and allows a higher level of fluid flow heat transfer. Thus, at constant fluid flow velocity and temperature, a smaller diameter tube will transfer a higher heat rate to the heat exchanger tube wall than will a larger diameter tube.
Utilizing a tube at the center of the invention assembly allows the designer latitude to control and vary the pressure loss through the heat exchanger by varying the diameter of the assembly tube and the resulting dimension of the helix component. In conjunction with the ability to control the invention assembly pressure loss through the heat exchanger by varying the tube and helix cross-sectional dimensions, the designer can further enhance the invention assembly application with the insertion of twisted ribbon or other low pressure drop heat transfer media to the inside of the invention assembly integral tube to optimize the overall heat transfer rates and system allowable pressure loss.
In light of the foregoing discussion, there is a need for an improved heat exchanger system which overcomes the disadvantages as posed by the prior art and provides an improved heat exchanger system with improved heat transfer.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a heat exchanger system for improved heat transfer heat transfer by increasing the velocity of the flowing fluid and by fluid mixing to minimize laminar layers.
Another object of the present invention is to provide a heat exchanger system comprising a turbulator placed inside a heat exchanger tube parallel to fluid flow for increasing heat transfer along the flow path of the fluid.
In accordance with an embodiment of the present invention, the present invention teaches a method and system for heat exchanger system for increased heat transfer in a fluid flowing through the heat exchanger system comprising a first tube, a second tube and a helicoid structure wrapped around the second tube. The second tube along with the wrapped helicoid structure being present inside the first tube leads to increased velocity of the fluid in the heat exchanger system.
In accordance with another embodiment of the present invention, the present invention teaches a method and system for transferring heat from a viscous fluid flowing in a laminar state. The heat exchanger system comprising a first cylindrical tube, a second cylindrical tube and helix structure. The second cylindrical tube is present in the first tube and is concentric with the first tube. The helix is a helicoid structure wrapped around the second tube. The helix surrounding the second tube is placed parallel to the flow of the viscous fluid inside the heat exchanger system and the outside of the helix is in close proximity to inside wall of the first tube.
In accordance with another embodiment the present invention teaches a heat exchanger system, comprising a first tube and a turbulator, for heat transfer at one or more locations along the path of the fluid. The fluid comprises a first portion and a second portion. The first tube is a heat exchanger tube. The turbulator is present inside the first tube and is concentric with the first tube and comprises a second cylindrical tube and a helix. The helix is a helicoid structure wrapped around the second tube. The first portion of the fluid is the fluid portion confined between the turbulator and the first tube and flowing in a spiral portion due to the helix. The second portion of the fluid is the fluid passing through the second cylindrical tube.
The present invention increases the heat transfer rate of the tube surface of the heat exchanger system. Further, the present invention reduces the cost and size, both of which are highly desirable. The present invention reduces the size and cost of heat exchangers used in commercial, industrial, natural gas gathering, and petro-chemical applications by increasing the heat transfer rates, while reducing the pressure loss, of the heat exchanger tubes.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, the needs satisfied thereby, and the objects, features, and advantages thereof, reference now is made to the following description taken in connection with the accompanying drawings.

FIG. 1 shows a heat exchanger system according to an embodiment of the present invention.

FIG. 2 shows a cross-sectional view of the heat exchanger system according to an embodiment of the present invention.

FIG. 3 shows a heat exchange tube with plurality of extended surface fins wrapped around according to an embodiment of the present invention.

FIG. 4 shows an isometric side view of the turbulator according to an embodiment of the present invention.

Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention

DETAILED DESCRIPTION OF THE DRAWINGS

Before describing in detail the particular method and system for heat exchange in accordance with an embodiment of the present invention, it should be observed that the present invention resides primarily in combinations of system components related to the device of the present invention.
Accordingly, the system components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.
In this document, relational terms such as ‘first’ and ‘second’, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. The terms ‘comprises’, ‘comprising’, or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by ‘comprises . . . a’ does not, without more constraints, preclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the element.
The present invention discusses a heat exchanger system comprising a heat exchanger tube and a turbulator. The turbulator comprising a helix portion wrapped around a self contained tube, the self contained tube concentric to the heat exchanger tube. The heat transfer occurs in two places simultaneously along the path of the fluid flow through the heat exchanger tube. First, the outer portion of the fluid flow is controlled by the helix. The fluid flows in a spiral motion confined between the inside of the heat exchanger tube and the outer surface of the turbulator. This fluid experiences a high heat transfer rate to the inside of the heat exchanger tube resulting from the high fluid velocity generated by the spiral path of the helix and the reduced thickness of the fluid flow. Secondly, the portion of the fluid flow passing through the second tube, possessing a reduced cross-sectional dimension compared to the first tube, is exposed to the high velocity of the first fluid flow mentioned above flowing around the outer surface of the invention assembly second tube.
The present invention is directed at providing an improved heat exchanger tube turbulator for use in transferring heat from a viscous fluid flowing in a laminar state. It is to be understood that the specific embodiment of the heat exchanger tube turbulator shown on the drawing is merely illustrative of the preferred embodiment and presently contemplated by the applicant for carrying out the invention and is by no means meant as a limitation to the many varied forms of heat exchangers to which the invention may be applicable. Accordingly, it is intended that any modifications which is apparent to those skilled in the art in light of the foregoing description and which falls within the spirit and scope of the appended claims be included in the invention as recited therein.
FIG. 1 shows a heat exchanger system 100 according to an embodiment of the present invention. The heat exchanger system 100 includes a first tube 102; also referred to as the heat exchanger tube, a plurality of extended surface fins 104, a helicoid structure 106, a second tube 108, a fluid 110, a first portion 112 of the fluid 110 and a second portion 114 of the fluid 110.
The first tube 102 and the second tube 108 are concentric and are placed along the same axis.
According to an embodiment of the present invention, the first tube 102 and the second tube 108 are cylindrical tubes possessing an inlet and outlet for facilitating the fluid flow through the heat exchanger system 100.
According to another embodiment of the present invention, the second tube 108 is a piece of sheet metal “roll formed” into a cylinder.
According to yet another embodiment of the present invention, the sheet metal possesses a small gap where the two edges of the “roll formed” sheet metal touch.
The helicoid structure 106 is wrapped around the second tube 108. The assembly, including the helicoid structure 106; also referred to as the helix, and second tube 108, hereinafter also referred to as the turbulator, is contained within the first tube 102. The outer edge of the helicoid structure 106 is in close proximity to the inside wall of first tube 102. The first tube 102 is a heat exchanger tube. The outer edge of the second tube 108 is in close proximity to the inner edge of the helicoid structure 106. The helicoids structure 106 is manufactured from one of a carbon, stainless steel or other non-corrosive material.
According to an embodiment of the present invention, the helicoid structure 106 is a helical structure.
The flow of the fluid 110 in the first tube 102 is divided into two lesser flows. A first portion 112 passes between the inside of the first tube 102 and the outside of the second tube 108 within the confines of the helicoid structure 106. The second portion 114 of the fluid flow passes through the second tube 108.
The configuration provided by the present invention subjects flow of first portion 112 of fluid being confined inside the spiral of the helicoid structure 106, increasing the heat transfer rate, but allowing the second portion 114 of the fluid passing through the center of the second tube 108 to pass unobstructed, thus reducing pressure drop and significantly increasing the overall efficiency of the heat exchanger system 100.
The heat transfer occurs in two places simultaneously along the flow path of the fluid 110 through the heat exchanger tube. First, the outer portion of the fluid flow i.e. the first portion 112 of the fluid is controlled by the helix and flowing in a spiral motion confined between the inside of the heat exchanger tube and the outer surface of the turbulator experiences a high heat transfer rate to the inside of the heat exchanger tube resulting from the high fluid velocity generated by the spiral path of the helix and the reduced thickness of the fluid flow. Secondly, the second portion of the fluid 114 passing through the turbulator, possessing a reduced cross-sectional dimension compared to the heat exchanger tube, is exposed to the high velocity of the first portion of the fluid 112 flowing around the outer surface of the turbulator.
According to an embodiment of the present invention, the diameter of the second tube 108 is typically not greater than ¾ of the diameter of the first tube 102. For example, if the diameter of the first tube 102 is 1 inch, the second tube 108 would normally possess a diameter of not greater than 0.750 inches.
According to an embodiment of the present invention, the heat exchanger system 100 does not include the plurality of surface extended fins 104, particularly in case of shell and tube heat exchangers.
According to yet another embodiment of the present invention, the plurality of extended surface fins 104 run longitudinally to the first tube 102.
FIG. 2 shows a cross-sectional view of the heat exchanger system 100 according to an embodiment of the present invention. The heat exchanger system 100 includes the first tube 102, the plurality of extended surface fins 104, the helicoid structure 106 and the second tube 108. The first tube 102 and the second tube 108 are concentric and are placed along the same axis. The helicoid structure 106 is wrapped around the second tube 108. The turbulator, consisting of a helicoid structure 106 and second tube 108, is contained within the first tube 102. The turbulator is shown in cross section A-A′ within the confines of a heat exchanger tube which is surrounded by the plurality of extended surface fins 104 as used in a forced convection air cooler.
According to an embodiment of the present invention, the first tube 102 and the second tube 108 are the first cylindrical tube and the second cylindrical tubes respectively with the helix surrounding the second cylindrical tube. The helix surrounding the second cylindrical tube is placed parallel to the flow of the viscous fluid inside the first cylindrical tube. The outside of the helix is in close proximity of to the inside wall of the first cylindrical tube.
According to an embodiment of the present invention, the range of the proximity between the first tube 102 and the helicoid structure 106 is ⅛ of an inch and lower.
FIG. 3 shows a heat exchange tube 102 with the plurality of extended surface fins 104 around according to an embodiment of the present invention.
FIG. 4 shows an isometric side view of the turbulator according to an embodiment of the present invention. The turbulator includes the helicoid structure 106 and the second tube 108.
The present invention increases the heat transfer rate of the tube surface of the heat exchanger system. Further, the present invention reduces the cost and size, both of which are highly desirable. The present invention reduces the size and cost of heat exchangers used in commercial, industrial, natural gas gathering, and petro-chemical applications by increasing the heat transfer rates of the heat exchanger tubes.
While the drawings illustrate the turbulator as associated with a heat exchanger designed for transferring heat of laminar fluids, it is contemplated that the turbulator can be used for other applications where it is desired to increase heat transfer for any medium flowing through the heat exchanger tubes.
While the present invention has been described in connection with preferred embodiments, it will be understood by those skilled in the art that variations and modifications of the preferred embodiments described above may be made without departing from the scope of the invention. Other embodiments will be apparent to those skilled in the art from a consideration of the specification or from a practice of the invention disclosed herein. It is intended that the specification and the described examples are considered exemplary only, with the true scope of the invention indicated by the following claims.

Claims

1. A heat exchanger system for increased heat transfer in a fluid flowing through the heat exchanger system, the heat exchanger system comprising:

a. a first tube;

b. a second tube, the second tube being present inside the first tube, the second tube being concentric with the first tube; and

c. a helicoid structure wrapped around the second tube.

2. The heat exchanger system according to claim 1, wherein the helicoid structure possesses a variable pitch.

3. The heat exchanger system according to claim 1, wherein the first tube is a cylindrical tube possessing an inlet and an outlet to allow the fluid flow through the heat exchanger system.

4. The heat exchanger system according to claim 1, wherein the second tube is a cylindrical tube possessing an inlet and an outlet for facilitating fluid flow.

5. The heat exchanger system according to claim 1, wherein the second tube is capable of possessing varying diameter.

6. The heat exchanger system according to claim 1 or 5, wherein diameter of the second tube is ¾ of diameter of the first tube.

7. The heat exchanger system according to claim 1, wherein outer edge of the second tube is in proximity to the inner edge of the helicoid structure.

8. The heat exchanger system according to claim 7, where in range of the proximity is ⅛ of an inch and lower.

9. The heat exchanger system according to claim 1 further comprising a plurality of extended surface fins, the plurality of extended surface fins surrounding the first tube.

10. The heat exchanger system according to claim 1, wherein the helicoid structure is manufactured from one of carbon steel, stainless steel and other non-corrosive material.

11. A heat exchanger system for transferring heat from a viscous fluid flowing in a laminar state, the heat exchanger system comprising:

a. a first cylindrical tube;

b. a second cylindrical tube, the second cylindrical tube being present inside and concentric with the first cylindrical tube;

c. a helix, the helix surrounding the second cylindrical tube, the helix being a helicoid structure wrapped around the second tube; and

wherein the helix surrounding the first cylindrical tube is placed parallel to the flow of the viscous fluid inside the heat exchanger system and outside of the helix is in close proximity to inside wall of the first tube.

12. The heat exchanger system according to claim 11, wherein the helix possesses a variable pitch.

13. The heat exchanger system according to claim 11, wherein the second cylindrical tube is capable of possessing a varying diameter.

14. The heat exchanger system according to claim 11, wherein outer edge of the second cylindrical tube is in close proximity to the inner edge of the helix.

15. The heat exchanger system according to claim 11 further comprising a plurality of extended surface fins, the plurality of extended surface fins surrounding the first cylindrical tube.

16. The heat exchanger system according to claim 11, wherein the helix is manufactured from one of carbon steel, stainless steel and other non-corrosive material.

17. The heat exchanger system according to claim 11, where in range of the proximity is ⅛ of an inch and lower.

18. A heat exchanger system for heat transfer at one or more locations along the path of the fluid, the fluid comprising a first portion and a second portion, the system comprising:

a. a first tube, the first tube being a heat exchanger tube;

b. a turbulator; the turbulator being concentric with the first tube, the turbulator comprising:

i. a second cylindrical tube, the second cylindrical tube being present inside the first tube;

ii. a helix, the helix surrounding the second tube, the helix being a helicoid structure wrapped around the second tube;

wherein the first portion of the fluid being controlled by the helix and flowing in a spiral portion, the first portion being the fluid portion confined between the turbulator and the first tube; and

wherein the second portion of the fluid being the fluid passing inside the second cylindrical tube.

19. A method of increased heat transfer in a heat exchanger system, the heat exchanger system comprising a first tube and turbulator, the turbulator being present inside the first tube, the turbulator comprising a second tube surrounded by a helix, wherein the heat transfer occurs at one or more locations along the flow path of fluid, the fluid flow path comprising a first portion and a second portion, the method comprising:

a. transferring heat along path of the first portion of the fluid, the first portion being the portion present between the first tube and the turbulator; the first portion being subjected to spiral path of the helix and reduced thickness of the fluid flow; and

b. transferring heat along path of second portion of the fluid, the second portion of the fluid being the fluid passing inside the turbulator.

20. The method according to claim 19, wherein varying diameter of the turbulator facilitates controlling pressure loss through the heat exchanger system.