Liquid-to-liquid Heat Exchanger

Abstract

A liquid-to-liquid heat exchanger adapted especially for use with an automotive vehicle radiator assembly for transferring heat from automatic power transmission fluid to the engine liquid coolant comprising a pair of cylindrical tubes adapted to be positioned in coaxial disposition within the engine radiator heater and a helical turbulator positioned within an annular space defined by the cylindrical tubes, said turbulator comprising a rolled strip with a channel cross-section, said strip being wound about the axis of the heat exchanger to form a continuous helical flow channel, thus increasing the turbulence in the field flow path for the transmission oil.

Parent Case Text

REFERENCE TO RELATED DISCLOSURE

This is a continuation-in-part of application Ser. No. 131,306, filed Apr. 5, 1971, now abandoned.

Description

GENERAL DESCRIPTION OF THE INVENTION

The heat exchanger construction of my invention is adapted to be used for cooling oil used with an automatic transmission in an automotive vehicle driveline. Such transmissions usually include a hydrokinetic torque converter which multiplies engine torque before it is distributed to transmission gearing. The inherent slip in the torque converter causes a horsepower loss which results in heating of the transmission oil. It is necessary in arrangements of this type to circulate the oil continuously through the converter and through an oil cooler in order to maintain a stabilized temperature during operation of the driveline under power.

The transmission oil cooler usually is situated in the lower radiator tank for the liquid-to-air heat exchanger or radiator used for the cooling of the engine coolant for the internal combustion engine. The coolant is circulated through a cooling jacket within the engine block of the internal combustion engine. It is circulated also through the vehicle radiator located in the moving ambient air stream.

I am aware of several transmission oil cooler constructions in arrangements of this type, including the construction shown in U.S. Pat. Nos. 3,116,541 and 3,265,127. Each of these prior art constructions includes a so-called turbulator located between an inner and outer heat exchanger shell of generally tubular construction. The turbulator causes turbulence in the fluid flow path for the transmission oil that is circulated through the transmission cooler in order to assist in heat transfer from one liquid medium to the other.

It is a principal feature of my invention to improve upon the heat transfer characteristics of heat exchangers of the type presently used in the automotive industry by increasing the effective length of the fluid flow path as the fluid passes through the oil cooler. This length of the path increases the time during which the heated transmission oil is exposed to the cooled surfaces of the heat exchanger construction that are in contact with the liquid coolant in the engine radiator. It is possible to reduce the effective size and to change the shape and dimensions of the transmission oil cooler to meet design and space limitations without adversely affecting the ability of the heat exchanger to maintain a stabilized temperature for the transmission oil at the desired operating temperature level. The improved performance of my heat exchanger is achieved by using a simplified construction that lends itself to simplified manufacturing techniques. My improved heat exchanger construction includes inner and outer shells and a centrally disposed turbulator that is comprised of a continuous rolled ribbon. A channel is rolled by means of a suitable rolling die which forms the ribbon along its length. The dies may be designed so that curling of the rolled ribbon stock takes place as the channel cross-section is formed. The rolled ribbon may be coiled into a cylinder and assembled between the inner and outer cooler shells, the ends of which may be sealed by welding. Suitable fluid fittings then may be secured to the outermost shell to accommodate transfer of transmission oil through the helical fluid flow path defined by the turbulator and the cooperating cooler shells.

The length of the fluid flow path through the turbulator can be varied simply by varying the width of the ribbon.

BRIEF DESCRIPTION OF THE FIGURES OF THE DRAWING

FIG. 1 shows a side elevation view partly in cross-section of my improved heat exchanger assembly;

FIG. 2 is a cross-sectional view taken along the plane of section line 22 of FIG. 1;

FIG. 3 is a side elevation view of the turbulator element used in the assembly of FIG. 1;

FIG. 4 is a cross-sectional view of the turbulator shown in FIG. 3;

FIG. 5 is a partial view of an unwrapped section of the ribbon stock used and formed in a turbulator of FIGS. 3 and 4.

FIG. 6 is a detail view showing a modified turbulator as it would appear in a wrapped condition following assembly.

FIG. 7 is a cross-sectional view taken along the plane of line 7--7 of FIG. 6.

FIG. 8 shows a side elevation view partly in cross-section showing the modified turbulator of FIGS. 6 and 7 therein.

PARTICULAR DESCRIPTION OF THE INVENTION

Numeral 10 in FIGS. 1 and 2 designates a cylindrical outer shell for the heat exchanger of my invention. It surrounds the cylindrical shell 12. The ends of shell 12 are formed with an enlarged diameter section, as indicated at 16 and 18. The sections 16 and 18 engage the inner surface of the shell 10 and it may be secured to the shell 10 by welding.

The shells 10 and 12 form an annular space 20 extending from one end of the assembly to the other. A fluid inlet fitting 22 surrounds an inlet opening 24 formed in the shell 10.

Fitting 22 is threaded at 26 to permit a connection with a fluid transmission line extending to the automatic transmission.

A fitting 28, which is similar to the fitting 22, is formed in the shell 10 at the opposite end of the assembly shown in FIG. 1. It serves as an outlet flow passage for the transmission oil circulated through the assembly.

Positioned within the annular space defined by the shells 10 and 12 is the turbulator shown in FIGS. 3 and 4. This comprises a coiled, rolled ribbon of the type shown in FIG. 5. The ribbon is rolled to form a channel, the rolling dies having peripheries formed with the cross-sectional shape indicated in FIG. 4. After the rolling operation is completed, it is coiled in end-to-end relationship, as indicated in FIG. 4, so that its inside diameter is slightly larger than the outside diameter of the shell 12. The height of the channel, which is indicated by reference character 30, is slightly less than the radial thickness of the annular space between the shells 10 and 12.

Fluid entering the fluid fitting 22 is received within the fluid channels of the turbulator. The fluid circulates in a helical path through the turbulator and then is received at the fitting 28 and returned through a suitable fluid conduit to the transmission. The assembly shown in FIG. 1 is placed in the lower header of the automotive radiator so that the engine coolant circulates around the outer surface of the shell 10 and over the inner surface of the shell 12.

The helical flow path produced by the turbulator increases the time of exposure of the heated oil to the coolant in the radiator header, thereby improving the heat transfer capability of the cooler.

The helical flow path for the heated oil can be defined also by a turbulator of the type shown in FIG. 6. This includes a helical wire 32 which would be wrapped about the shell 12 within the annular space defined by the shell 12 and the shell 10. It engages both shells and defines a helical flow path. The wire 32 forms a seal which prevents cross flow. Situated between the spaced windings of the wire 32 is a ribbon or strip 34. The strip 34 is formed with indentations which comprise a series of alternately spaced undulations shown at 36 and at 38. The undulations 36 are out of phase with respect to the undulations 38 so that apertures are formed between them. These apertures permit turbulant fluid flow through the heat exchanger as the fluid flow traverses the helical circuit.

Claims

Having thus described a perferred form of my invention, what I claim and desire to secure by U.S. Letters Patent is:

1. A liquid-to-liquid heat exchanger adapted especially for use with an automatic power transmission mechanism for cooling oil circulated through the transmission mechanism and adapted to be mounted in liquid coolant within an air cooled radiator for a liquid-cooled automotive engine comprising a pair of heat exchanger shells of generally tubular construction, one shell being situated within the other in coaxial disposition, said coolant circulating over the outer surface of the outermost shell and over the inner surface of the innermost shell, said shells defining therebetween an annular space, a turbulator construction situated in said annular space, a fluid fitting connected to the outermost shell for receiving transmission oil and a fluid flow outlet fitting connected to said outermost shell for receiving transmission oil circulated through said cooler, the flow paths defined in part by said fittings communicating with said annular space at axially spaced locations, said turbulator construction registering with said shells and forming therebetween a helical flow path for the fluid flow that passes from one of said fittings to the other, said turbulator construction comprising two parts, the first part being a helical wire surrounding the innermost skill and engaging the adjacent shell surfaces to prevent crossflow from one point in the helical flow path to another in an axial direction, the geometric axis of the helical flow path formed by said turbulator construction the second turbulator construction being a turbulator ribbon having a plurality of undulations located between the helical wire and forming in said ribbon liquid flow openings, said ribbon being wrapped around the innermost shell in helical disposition whereby the flow path is generally helical and is characterized by localized turbulance.