CA1094544A

CA1094544A - Heat exchanger

Info

Publication number: CA1094544A
Application number: CA314,346A
Authority: CA
Inventors: William Melnyk
Original assignee: McCord Corp
Current assignee: McCord Corp
Priority date: 1978-02-03
Filing date: 1978-10-26
Publication date: 1981-01-27
Also published as: FR2416441A1; DE2903805C2; GB2013866A; FR2416441B1; GB2013866B; DE2903805A1

Abstract

ABSTRACT OF THE DISCLOSURE
A tubular heat exchanger including inner and outer tubes sealed at their ends to form an annular fluid passageway and a turbulator assembly of increased strength including multiple turbulator sleeves arranged in telescoped relationship located within the passageway; all of the turblator sleeves being of uniform width.

Description

~o~s~

FIELD OF THE INVENTION
This invention relates to heat exchangers having a tubular structure and is particularly directed to a tubular heat exchanger of the type used in autGmotiv vehicles as an oil cooler. This type of heat exchanger is typically submerged in the tank of a vehicle radiator.
BACKGROUND OF THE INVENTION
Tubular heat exchangers are commonly employed in auto-motive vehicles for cooling the transmission oil to dissipate heat generated in the transmission. Typically, such oil coolers are located inside the lower radiator tank of the liquid-to-air radiator used to cool the engine coolant. Since the available space for the oil cooler in the radiator tank is limited, every effort is made to maximize the heat transfer efficiency of the oil cooler Hence, heat exchangers having a tubular construction are employed.
A tubular heat exchanger is constructed of outer and inner tube members of approximately equal length. The two tubes are arranged concentrically with respect to one another and have their ends sealed together to form an annular passageway between the two tubes for conducting the oil to be cooled.
Suitable inlet and outlet fittings are attached to opposed ends of the heat exchanger for connecting lines which carry oil to -and from the heat exchanger. The coolant in the raditor tan~
flows around the outer tube and through the inner tube to collect heat from these surfaces.
A turbulator is located within the annular passageway between the inlet and outlet fittings to produce turbulent flow in the oil. The turbulator is usually in the form of a cylindrical sleeve made of two mating sections or halves which includes turbulence producing projections extending normal to its surface to form a tOrtuQus path for the oil. The turbulator is also used as a conductor to conduct heat from the oil to the inner and outer tubes. For this reason, the turbulator must be in in-timate contact with the walls of the passageway formed by the inner and outer tubes to insure maximum heat transfer. In order to accomplish this objective, the inner and outer tubes are assem-bled with the turbulator located between them. The inner and outer dimensions of each of these parts are such that they can be easily assembled by slipping the parts together. A ball having a diameter slightly greater than the inner diameter of the inner tube is forced through the inner tube causing the inner tube to expand. ~y expanding the inner tube the turbulator is tightly compressed between the inner and outer tubes and, hence, is brought into intimate contact with the interior walls of the passageway.
A requirement of this assembly procedure is that the turbulator sleeve must have sufficient strength in compression in a direction transverse to its longitudinal axis to withstand the forces which it experiences as the inner tube is expanded.
In a typical tubular heat exchanger assembly, the entire width of the annular passageway is filled with a single tuxbulator sleeve. Therefore, the overall width or thickness of the turbu-lator sleeve must be slightly less than the width of the passage-way prior to expanding the inner tube. The overall width or thickness of the turbulator sleeve is determined primarily by the height of the turbulence producing projection since the turbulator is made out of relatively thin sheet metal. The peaks of the projections engage the walls of the passageway and it is the projections which must withstand the compressive forces experienced when the inner tube is expanded. As the height of the projections increases, the strength decreases if the thickness of the sheet metal remains constantO There-fore, in known tubular heat exchangers there is an upper limit to the width of the passageway without risking collapse of the :10~544 turbulator projections.
SUMMARY OF THE INVENTION
The subject invention provides an improved heat ex-changer assembly including an outer tube and an inner tube sealed together at their ends to define an annular closed passageway for conducting a fluid to be cooled. Inlet and out-let fittings are disposed at opposed ends of the heat exchanger for carrying fluid to and from the passageway. A turbulator assembly is located within the annular passageway between the inlet and outlet fitting and includes first and second tur-bulator sleeves with the second turbulator sleeve having a smaller diameter than the first turbulator sleeve and located within the first turbulator sleeve in telescoped relation there-with. The first and second turbulator sleeves include longi-tudinal rows of undulations with each row of undulations beingout of phase with immediately adjacent rows of undulations for forming a tortuous flow path for the fluid through the tur-bulators. A tubular separator is disposed between the first and second turbulator sleeves and engage the undulations thereof to prevent nesting of the turbulator sleeves. The undulations of the first and second turbula~or sleeves are in intimate heat exchange contact with the separator and an adjacent tube.
The separator and the turbulator sleeves are coextensive and tenminate short of the extremities of the annular fluid passage-way and short of the inlet and outlet fittings, respectively,to allow mixing of fluid passing through the turbulator sleeves.
The turbula~or sleeYes are of substantially uniform width.
BRIEF D~SCRIPTION OF THE DR~WINGS
Other advantages of the present in~ention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in ~onnection with the accompanying drawings wherein:

10~4S~4 FIGURE 1 is a front elevational view, partly in cross section, of a tubular ~eat exchanger constructed in accordance with the instant invention;
FIGURE 2 is a view taken generaliy along line 2-2 - 3a -lO9~S~4 of FIGURE l; and ~IGURE 3 is an enlarged view of a portion of the tubular heat exchanger shown in FIGURE 1.
DETAILED DESCRIPTION OF T~IE INVE~TION
Referring more particularly to the drawings, a tubular heat exchanger constructed in accordance with the instant inven-tion is generally shown at 10 in FIGURE 1. The heat e~changer 10 is a double concentric tubular heat exchanger in which two tubular heat exchangers are assembled in parallel. The double concentric heat exchanger design increases the surface area available for heat transfer and, therefore, increases the thermal efficiency of the heat exchanger. It is to be understood, however, that the concept of the instant invention may be employed with single as well as double tubular heat exchangers.
The heat exchanger 10 includes an outer tubular assembly generally indicated at 12 and an inner tubular assembly indicated at 14. The outer tubular assembly 12 includes an outer tube or shell 16 and an inner tube or shell 18. The two tubes 16 -and 18 are sealed at their ends as shown at 20 and 21 to form a sealed annular passageway 22 for carrying a fluid to be cooled, e.g., oil. Internally threaded inlet and outlet fittings 24 and 26 are located at opposed ends of the tubular assembly 12 for carrying the fluid to be cooled to and from the heat exchanger assembly 10. The inlet and outlet fittings 24 and 26 are welded to suitable saddles 28 as best shown in FIGURE 2 to secure the inlet and outlet fittings 24 and 26 to the outer tubular assembly 12.
The inner tubular assembly 14 is of simpler construc-tion but is smaller in size so that it can be located concen-trically within the outer tubular assembly 12. The inner tubularassembly 14 includes an outer tube or shell 30 and an inner tube or shell 32. These two tubes 30 and 32 are sealed together 10!9~5~4 at their ends 34 and 35 to form an annular passageway 36 therebetween.
The inner and outer tubular assemblies 12 and 14 are connected in parallel by short connectors 38 ana 40 which establish fluid communication k~tween the two tubular assemblies.
Hence, a portion of the fluid flowing into the passageway 22 in the outer tubular assembly 12 will flow through the connector 38 into the passagewa~ 36 in the inner tubular assembly 14. At the outlet end of the heat exchanger fluid flows from the passage-way 36 in the inner tubular assembly 14 through connector 40and the outlet fitting 26.
Turbulator assemblies are provided in each of the fluid passageways 22, 36 in the two tubular assemblies 12 and 14. Since the width of the passageway 22 in the outer tubular assembly 12 is larger than the width of the passageway 36 in the inner tubular assembly 14, a double or stacked turbulator assembly is employed in the outer tubular assembly 12. This turbulator assembly is shown in FIGURE 3 wherein the turbulator assembly includes a first turbulator sleeve 42 and a second tur-bulator sleeve 4~. The second turbulator sleeve 44 has an outerdiameter which is smaller than the inner diameter of the first turbulator sleeve 42 so that it can be located in telescoped relationship to the first turbulator sleeve. The turbulator sleeves are fabricated from thin sheet metal having good thermal conductivity. The sheet material is stamped and separated in a transverse direction to form turbulence producing projections.
More specifically, the sheet metal is slit and punched to form adjacent longitudinal rows of alternating projections having the general shape of a truncated triangular wave form. Adjacent rows of projections are out of phase so that the flat peaks of one projection extends in the opposite direction to the flat peaks of adjacent projections. After forming the projections 5 _ 105~544 in the sheet metal, the sheet metal is rolled into a cylinder or sleeve having the proper length and diameter. Fluid flowing through the passageway 22 must make repeated direction changes so it encounters the sloped sides of the projections and is momentarily forced to flow laterally.
As shown in FIGURE 3, the flat peaks, e.g. peak 46, of the outer turbulator sleeve 42 engage the inner surface of the outer tube 16 while the flat peaks, e.g. peak 48, of the inner turbulator sleeve 44 engage the surface of the inner tube 18.
In order to prevent nesting of the projections a sepa-rator member 50 is employed between the stacked turbulator sleeves 42 and 44. In the embodiment shown, the separator member 50 comprises a cylindrical sleeve made of thin sheet metal. The sleeve 50 is formed of the two halves separated longitudinally.
The two part sleeves 50 permits unrestricted expansion of the outer turbulator sleeve 42 during expansion of the inner tube 18. The adjacent flat peaks of the inner and outer turbulator sleeves, e.g. peaks 52 and 54, engage cpposite sides of the separator member 50.
The stacked turbulator arrangement provides a turbulator assembly which is stronger in compression than a unitary turbu-lator sleeve of similar configuration. Hence, when the inner tube 18 is being expanded, sufficient outward force can be applied to insure close intimate contact between the respective elements of the assembly. It is to be understood that should the distance between the outer and inner tubes 16 and 18 be increased addi-tional turbulator sleeves may be used. The key being that the height of the individual projections is reduced by providing multiple turbulator sleeves which are in telescoped relationship with respect to one another.

Another advantage Qf using a multiple or stacked tur-bulator assembly is that width size of the punched sheet metal ~109~5~4 prior to rolling the turbulator sleeves can be standardized.
In a double tu~ular heat exchanger of the type shown, the passage-way 36 in the inner tubular assembly will, in most cases, be smaller than the passageway 22 in the outer tubular assembly.
If a single turbulator were used in both passageways, two different si~ed turbulator sleeve sheet material would be required. By employing a multiple turbulator sleeve assembly the width of the passageway in the outer tubular member 12 can be designed as a multiple of the width of the passageway in the inner tubular assembly 14 (taking into account the thickness of the separators).
Hence, a single size turbulator sleeve can be fabricated for both passageways. Ac~ordingly, a single turbulator sleeve 56 is used in the inner tubular assembly which has the same width or thickness as the turbulator sleeves 42 and 44 in the outer tubular assemblies. Obviously, while the width of the turbulator sleeves can be standardized the diameters must vary.
In operation, oil from the transmission is conveyed through a suitable line (not shown) through inlet fitting 24 and into the two tubular assemblies 12 and 14. The oil flows through the annular passageways 22 and 36 toward the outlet fitting 26. The oil is forced through a tortuous path by the turbulator sleeves in the passageways which produces turbulent flow and enhances heat transfer. Engine coolant in the radiator header within which the heat exchanger 10 is submerged flows around the outer tubular assembly 12, through the annular space between the outer and inner tubular assemblies 12 and 14, and through the inner tubular assembly 14. In so doing, the coolant collects heat from these surfaces and reduces the temperature of the oil. When the oil has reached the outlet fitting 26 it flows through a suitable line (not shown~ to the transmission.
The invention has been described in an illustrative manner, and it is to be understood that the terminology which 109~54~

has been used is intended to be in the nature of words of de-scription rather than of limitation.
Obviously, many modifications and variations of the present invention are possible in light of the above teachings.
It is, therefore, to be understood that the invention may be practiced otherwise than as specifically described herein and yet remain within the scope of the appended claims.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A heat exchanger assembly comprising; an outer tube and an inner tube sealed together at their ends to define an annular closed passageway for conducting a fluid to be cooled, inlet and outlet fittings at opposed ends of the heat exchanger for carrying fluid to and from the passageway, a turbulator assembly located within the annular passageway between the inlet and outlet fitting including first and second turbulator sleeves with said second turbulator sleeve having a smaller diameter than said first turbulator sleeve and located within said first turbulator sleeve in telescoped relation therewith, said first and second turbulator sleeves including longitudinal rows of undulations with each row of undulations being out of phase with immediately adjacent rows of undulations for forming a tortuous flow path for the fluid through said turbulators, a tubular separator between said first and second turbulator sleeves and engaging said undulations thereof to prevent nesting of said turbulator sleeves, said undulations of said first and second turbulator sleeves being in intimate heat exchange contact with said separator and an adjacent tube, said separator and said turbulator sleeves being coextensive and terminating short of the extremities of said annular fluid passageway and short of said inlet and outlet fittings, respectively, to allow mixing of fluid passing through said turbulator sleeves, said turbulator sleeves being of substantially uniform width.