JP3044074B2 - Multi-pass evaporator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat exchanger, and more particularly to a heat exchanger used as an evaporator.

[0002]

2. Description of the Prior Art As is well known, commonly used air conditioning systems that operate on a vapor compression cycle use an evaporator as a means of cooling the air to be conditioned. Refrigerant is passed through the evaporator and expanded therein. Upon expansion, the refrigerant absorbs its heat of evaporation, thereby cooling the medium in contact therewith, typically the heat exchanger tubes. Air to be temperature controlled is flowed around these tubes. The tubes are typically provided with fins to improve heat transfer on the air side. The air is cooled, at least locally, below its dew point, so that water from the air condenses on the fins and tubes. This condensate must be removed. Otherwise, the water can freeze and block the air passages.

[0003] Various proposals have been made for the removal of condensate and in its simplest form involve the use of gravity with the aid of the speed of the air flow traveling through the evaporator as far as possible. . These systems work generally well, but often become unnecessarily bulky,
Low reliability.

Further, when relatively high airflows are present, such as in automotive air conditioning systems that operate the fans at high speeds to achieve maximum cooling in a short time, moisture is entrained in the airflows. It is desirable to remove moisture from the evaporator as quickly as possible in order to prevent it from entering the vehicle compartment.

One evaporator structure that is ideally suited for use in situations that address the above problems is disclosed in US Pat. No. 4,829,780.

[0006]

SUMMARY OF THE INVENTION The evaporator of this patent is:
While providing a good, low cost and lightweight means of collecting condensate in an evaporator, there is a need to design such structures more optimally to improve their usefulness.

An object of the present invention is to achieve such a task. It is an object of the present invention to provide an improved heat exchanger that is optimally adapted for use as an evaporator. It is another object of the present invention to provide an evaporator of the type disclosed in the above-mentioned U.S. Pat.

[0008]

SUMMARY OF THE INVENTION In accordance with one aspect of the present invention, there are provided elongated parallel upper and lower headers each extending between the headers in a longitudinal and side-by-side relationship therewith. An evaporator is provided that includes a plurality of heat exchange modules or units composed of a plurality of tubes. The tubes have a smaller dimension in the direction transverse to the header than the header, and the modules are juxtaposed or stacked together and assembled such that their corresponding tubes are aligned. Fins extend between adjacent tubes in each module, and upper and lower manifolds are provided. The upper manifold is in flow relation with the upper header at one end, and the lower manifold is in flow relation with the lower header at an end corresponding to the one end. This arrangement allows the manifold to be arranged on the same side of the evaporator and improves the performance of the heat exchanger as an evaporator.

According to another aspect of the invention, such an evaporator comprises at least two, preferably three, heat exchange units of the type described above. The upper and lower manifolds are in flow communication with the upper and lower headers, respectively, and at least one baffle is located on at least one, and preferably both, of the manifolds and directs fluid flowing through the evaporator to at least two passes through the unit.
It is positioned to circulate sequentially in three passes, preferably three passes.

[0010] The use of an evaporator constructed in accordance with this aspect of the present invention results in a more uniform exit air side temperature, which results in a more uniform core surface temperature over a single pass system without loss of performance. Indicates that it has been implemented. As a result of the improved temperature uniformity, the criticality of the arrangement of the thermostat temperature sensing tubes and the like inside the core is reduced and the tendency for condensate to freeze near the lower header is avoided.

In accordance with another aspect of the present invention, the heat exchange unit is assembled generally as described above to form a core. Baffles are positioned on at least some of the headers to permit fluid flowing through the evaporator to flow sequentially through each module or heat exchange unit portion in at least two passes.

In accordance with yet another embodiment of the present invention, a relatively narrow core having a thickness of less than about 2 inches (5.1 cm) is used. According to this aspect of the invention, the unit inch
Wavy fins with a density of at least 18 fins per (2.54 cm) are used.

[0013]

A plurality of heat exchange modules or units comprising upper and lower headers and a plurality of tubes provided in a longitudinally juxtaposed relationship between the headers are arranged such that their corresponding tubes are aligned. Stacking, evaporators in which the fins are provided between adjacent tubes in each module and the two manifolds are arranged in flow relation with the header on the same side improves the performance of the heat exchanger. Such an evaporator consists of at least two, preferably three, heat exchange units of the type described above, wherein at least one baffle is arranged on at least one, preferably both, the manifold and / or the header and the fluid flowing through the evaporator At least twice through the unit,
Preferably, it is distributed sequentially in three passes.
The use of an evaporator configured in this way results in a uniform outlet air side temperature, which achieves a more uniform core surface temperature over a single pass system without loss of performance. As a result of the improved temperature uniformity, the criticality of the arrangement of thermostat temperature sensing tubes and the like inside the core is reduced and the tendency for condensed water to freeze near the lower header is avoided.

[0014]

BRIEF DESCRIPTION OF THE DRAWINGS An embodiment of a heat exchanger according to the present invention is illustrated in the drawings and is here shown in particular as an evaporator. However, in some cases where compactness as a heat exchanger is desired, it may be used in applications other than evaporators. The present invention covers such other uses.

As shown in FIG. 1, the evaporator includes an upper header, generally indicated at 10, and a lower header, generally indicated at 12. As shown in FIG. 2, the upper header 10 is comprised of at least three, elongate header tubes 14 in side-by-side relationship. These header tubes 14 are sealed at their right ends 16 with plugs (plugs) 18 (FIG. 1). The tube 14 is in flow communication with the interior of the upper manifold 20 at the opposite end 19. Inside the manifold 20, there is a plug or baffle 22 and so that one of the header tubes 14 is in flow communication with one end 24 of the manifold 20 and two of the header tubes 14 are in flow communication with its opposite end 26. Be placed. In the illustrated embodiment, end 24 of manifold 20 may be an outlet for the evaporator.

The lower head 12 has an equal number of header tubes 30
Consists of Tube 30 is, as clearly shown in FIG.
They are in side-by-side abutment and are brazed together at 31 to be sealed together.

The right end 32 of the header tube 30 is sealed with a plug (not shown) similar to the plug (plug) indicated by 18. The left end 34 of the tube 30 is in flow communication with the lower manifold 36. Thus, it will be appreciated that the upper and lower manifolds 20 and 36 are on the same side of the evaporator. A fitting 38, similar to a conventional reducing joint, may be used to establish flow between the tubes 14 and 30 and the respective manifolds 20 and 36.

[0018] US Patent No. 4,829,780 mentioned above.
As disclosed in detail in the above paragraph, the header tube 30 and optionally also the header tube 14 have a non-rectangular cross section, preferably a circular cross section. Header tube 1 constituting headers 10 and 12
The circular cross sections for 4 and 30 and manifolds 20 and 36 maximize the burst pressure that the evaporator can withstand, while minimizing the use of materials for making these parts.

As shown in FIG. 1, headers 10 and 12
Are spaced but parallel and a plurality of parallel rows of flat tubes 40 are provided between the headers. The number of rows of tubes 40 is equal to the number of tubes 12 or 30, here 3
Column. The flat tube 40 is in flow relation with the corresponding one of the header tubes 14 and 30, so that the headers 10 and 12
Establish distribution in between. Thus, in the illustrative example,
The introduced refrigerant flows into the lower manifold 36 as shown by the dashed arrow in FIG. In accordance with the present invention, a baffle or plug similar to baffle or plug 22 is also provided in lower manifold 36 as shown schematically at 22 'in FIG. This position corresponds to the position shown as 39 in FIG.
It flows upward through tube bundle 40, downwards through the second tube bundle, and upwards through the last third tube bundle, and finally exits the structure through end 24 of manifold 20. Thus, an illustrative example is a three-pass evaporator. The intended air flow through the evaporator is in the direction of arrow 41 as shown in FIG. As a result, the refrigerant flows from the back to the front through the evaporator core, while the air flows from the front to the back through the core, which can be generally referred to as a generally counter-current type flow.

The transverse dimension of tube 40 relative to the length of header tubes 14 and 30 is slightly smaller than the width of header tubes 14 and 30 to allow for fabrication. Tube 40 is inserted into a slot (not shown) in header tubes 14 and 30.

In the illustrated embodiment, as already mentioned,
There are three rows of tube banks 40 and spaces 42 exist between the rows. It is relatively narrow, often on the order of 1/4 inch (6.35 mm) or less.

As shown in FIG. 3, the tube banks 40 are aligned with each other, ie, lie on a common straight line. Thus, it will be appreciated that the evaporator is comprised of a plurality of substantially equivalent modules or units, each assembled from an upper header tube 14, a lower header tube 30, and a plurality of flat tubes 40. The modules are interconnected by manifolds 20 and 36 and braze 31. Wavy fins 44
Extends between adjacent flat tubes in each module. As shown in FIG. 3, the corrugated fins 44 are common to each individual module, but can extend between the entire module if desired.

As is well known, the top of the wavy fin is
It is brazed or otherwise joined to the flat outer surface 46 of the zero.
If desired, the fins 44 can be provided with slat openings as indicated generally at 48. FIG. 4 illustrates the fin density with the symbol “FPT” representing the number of fins per inch. FIG. 4 illustrates 11 fins per inch.

If the core thickness (measured as shown in FIG. 3) is relatively small, ie, does not exceed about 2 inches (5.1 cm) , the performance of the evaporator will be the conventional fin density, ie, 14 fins / inch. It was unexpectedly found to improve as the fin density was increased from (2.54 cm) to at least a fin density in the range of 18 to 24 fins / inch (2.54 cm) .

Typically, such a high fin density is
The narrower spacing between the fins has been avoided in previous evaporators because it was expected that the smaller the spacing between the fins, the more likely it would be to be blocked by condensed water and thus impede or obstruct air flow, thereby reducing performance. The present invention can also improve performance in this regard.

Referring to FIG. 5, this is the manifold 2
A similar evaporator with an upper manifold 60 corresponding to zero and a lower manifold 62 corresponding to manifold 36 is shown schematically. Although three rows of tubes 40 are illustrated, the headers 10 and 12 associated therewith are not visible behind the manifold. Since no baffles are used, a single pass evaporator is provided. Air entering the evaporator in the direction of arrow 64 at a temperature of 25 ° C. exits the evaporator at a temperature that varies over a considerable width depending on the position of the air from above to below relative to the evaporator core. . Air exiting near the top of the core is at a temperature of about 10 ° C, while air near the lower end of the evaporator exits at about 0 ° C.

The latter condition is undesirable because condensed water tends to flow down the tube 40 in the space 42 and collect at the junction between the lower headers. It will be appreciated that the possibility of freezing of the condensate and subsequent freezing of the core is very high, since a temperature at the level of the freezing temperature of the water is present at the location of the condensate.

In contrast, as illustrated in FIG. 6, in an evaporator made in accordance with the present invention, when baffles 22 and 22 'are positioned to provide more than two passes as illustrated by arrows 66 in FIG. Air exiting at the same temperature in the direction of exits at a temperature of about 5.5 ° C. at the top of the evaporator and at a temperature of about 4.5 ° C. at the bottom of the evaporator. Thus, the air temperature is much more uniform in the evaporator according to the invention than in the past, and for all applications and purposes the evaporator according to the invention has a heat transfer performance equivalent to that of the evaporator as illustrated in FIG. Having.

This more uniform air temperature minimizes the possibility of freezing of condensed water and prevents icing of the core. In addition, as is well known to those skilled in the art, thermostat temperature sensing devices or tubes are often located in association with the evaporator core for a variety of reasons. Due to the uniformity of the air temperature, the positioning of such temperature detectors in the core is less critical than in prior art devices that could not achieve the uniformity of the air temperature.

In addition, using the lower manifold as the refrigerant inlet and the upper manifold as the refrigerant outlet as shown in FIG. 6 and both being located on the same side of the core as shown in FIG. It also provides increased performance over manifolds and / or other possible arrangements of inlets and outlets.

Yet another embodiment of the present invention is illustrated in FIGS. In this embodiment, as before, there are a plurality of modules, each comprising an upper header tube 100 and a lower header tube 102, and a plurality of flat tubes 104 extending in a substantially parallel relationship between the upper and lower headers. Be composed. Flat tube 104 has a transverse width smaller than the diameter of header tubes 00 and 102 and corrugated fins 106 intervene between the tubes.

In this embodiment, tubular manifolds 108 and 110 are used and are associated with both ends of header tube 102. As illustrated by flow arrows 112 and 114, manifold 108 functions as an inlet manifold and manifold 110 functions as an outlet manifold, respectively. The air flow is in the direction of arrow 116.

According to this specific example, the baffle 120
It is arranged in the middle of both ends of the header tube 102. Although here only one baffle 120 is illustrated as being provided on each of the tubes 102, it should be understood that additional baffles could be used, in which case the baffles could also be located on the header tube 100. In this example, two evaporators
A side-to-side flow of the path is provided. The flow is
It flows into the manifold 108 and is distributed to the left side of the header tube 102. From there, fluid flows in the direction of arrow 122 to the left of header tube 100 and flows to the right of rear header tube 100 as shown by arrow 124. Fluid flows into header tube 100
Reaches the right portion of the header tube 102 as shown by arrow 126 and exits to the manifold 110 in the direction of arrow 128.

Although not shown here, it is also within the scope of the present invention that the baffles be located on both the manifold and the header tube, in which case various combinations of front to back or back to front and one side to the other side. Multipath flows can be implemented as desired.

[0035]

For example, air entering at a temperature of 25 ° C. exits at a temperature of about 5.5 ° C. at the top of the evaporator and at a temperature of about 4.5 ° C. at the bottom of the evaporator; It is much more uniform than before. This uniformity of air temperature minimizes the possibility of condensate water freezing and prevents core icing. In addition, the positioning of the thermostat temperature sensing device is less critical than conventional devices. The fact that both manifolds are located on the same side of the core also provides an increase in performance over the manifold and / or other possible arrangements of inlets and outlets. It is possible to increase the fin density,
The result is increased performance.

[Brief description of the drawings]

FIG. 1 is a front view of a specific example of an evaporator made according to the present invention.

FIG. 2 is a plan view of the evaporator.

FIG. 3 is an enlarged perspective view of a lower portion of the evaporator.

FIG. 4 is a partial front view of an evaporator tube and a fin therebetween.

FIG. 5 is an explanatory diagram illustrating a temperature distribution of a one-pass evaporator.

FIG. 6 is an explanatory diagram illustrating the temperature distribution of a multi-pass, here, three-pass evaporator.

FIG. 7 is a front view of another embodiment of the present invention.

FIG. 8 is a plan view of FIG. 7;

FIG. 9 is a side view of FIGS. 7 and 8;

[Description of sign]

 10 Upper Header 12 Lower Header 14 Header Tube 18 Plug 20 Upper Manifold 22 Baffle 30 Header Tube 36 Lower Manifold 40 Tube 44 Fin

──────────────────────────────────────────────────続 き Continuation of the front page (56) References Japanese Utility Model Application Hei 2-7491 (JP, U) US Patent 4829780 (US, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F25B 39 / 02

Claims (6)

(57) [Claims] 1. A method comprising: a plurality of heat exchange modules;
Each module comprises an elongated, parallel upper and lower header and a plurality of tubes extending longitudinally between and in a side-by-side relationship between the upper and lower headers, said tubes comprising: The header has a smaller dimension in the transverse direction of the header, and the modules are juxtaposed and assembled together such that their corresponding tubes are aligned, fins extend between adjacent tubes in each module and Upper and lower manifolds,
An evaporator wherein the upper manifold is in flow communication with the upper header at one end thereof, and the lower manifold is in flow communication with the lower header at an end corresponding to the one end. 2. The evaporator according to claim 1, wherein the lower header is constituted by a header tube and is tightly abutted by a braze formed longitudinally between adjacent tubes. 3. The evaporator of claim 2, wherein the header tube is substantially circular in cross section. 4. At least two modules are provided, and at least one baffle is present in one of the manifolds and at least two fluids flow through the evaporator.
2. The evaporator of claim 1, wherein the evaporator is arranged to flow sequentially through the modules in a pass. 5. At least three modules are provided, and at least one baffle is present in one of the manifolds and at least three fluids flow through the evaporator.
2. The evaporator of claim 1, wherein the evaporator is arranged to flow sequentially through the modules in a pass. 6. The module is assembled to form a core having a core thickness of about 2 inches or less, wherein the fins are wavy fins and at least one fin per inch of tube.
The evaporator of claim 1, wherein there are eight fins.