GB2023796A - Hollow-plate heat exchange element - Google Patents

Abstract

A hollow-plate element providing a fluid pass 10 for a heat exchanger (e.g. a refrigerant evaporator in an air conditioning system) comprises a pair of plate members 11, 14 joined together at their edge portions 18 and forming between plate mid-portions a refrigerant flow path extending between an inlet manifold 24 and an outlet manifold 26 formed at the plate ends by outwardly extending chambered configurations 28 of the plates. At said plate midportions rows of separate ribs 42 are formed, each row extending across the flow path, and each rib being angled obliquely to the flow path. Each row has at the ends thereof a relatively short rib e.g. 42f, 42g joined with the edge portion of the plate. The ribs in each row in one plate overlap and are staggered with respect to corresponding ribs in the other plate to provide a tortuous flow path through the element. <IMAGE>

Description

SPECIFICATION Staggered rib evaporator tube Prior fluid tube passes for a heat exchanger, such as an evaporator, have been formed by plate members with their edge surfaces joined to form a flow passage therebetween. The plate midportions between the inlet and outlet were configured with ribs formed in rows across the tube pass. Previously, the rib in each row were aligned so as to form linear flow paths between the inlet and the outlet.

The specific structure claimed in this application describes a tube pass which prevents linear flow of fluid such as refrigerant between the inlet and outlet without significantly increasing the resistance to flow. Therefore, the heat exchange effectiveness of similarly di mensioned tube passes has been increased.

This permits the use of a thinner, lighter and less costly evaporator. With the present emphasis on weight reduction and compactness in the new smaller sized automobiles, the features of the subject tube pass are particularly important.

According to the present invention there is provided an elongate evaporator tube pass formed by a pair of plate members with edge portions 1 8 joined together and mid-portions spaced apart to form a refrigerant enclosure for flow therebetween, opposite ends of the plates having outward offsets from the plane of the mid-portions to define inlet and outlet manifold enclosures and to form offset surfaces on adjacent tube passes for engagement together when in stacked relation to form airflow passages between adjacent mid-portions of the tube passes, a plurality of rows of separated ribs 42 formed in the mid-portion of each plate member and with the ribs angled obliquely to the length and width thereof, each row having at least one full length rib and a partial length rib adjacent and continuous with respective opposite edge portions of the plate, the ribs of each row in one plate overlapping and being staggered with respect to the ribs in the same row of the other plate and to ribs in the adjacent row of said one plate to prevent a linear flow path across the rows of ribs.

This tube pass provides a very efficient heat transfer design by the use of a staggered rib configuration. The staggered rib configuration provides a particularly tortuous flow path for fluid but with many avenues of flow. The fluid distribution across the width of the tube pass and within the tube is also excellent.

Further advantages and features of the subject tube pass will be more easily understood by a reading of the following particular description, reference being had to the accompanying drawings which illustrate one embodiment of the invention.

IN THE DRAWINGS: Figure 1 is a planar view of an evaporator according to the invention with a tube pass which is progressively broken away from left to right to show exterior portions of the top plate, and interior portions of the bottom plate; Figure 2 is an elevational view of a plurality of stacked tube passes forming a portion of the evaporator and looking in the direction of arrows 2-2 in Fig. 1; Figure 3 is an enlarged fragmentary sectioned view taken along section line 3-3 in Fig. 1 and looking in the direction of the arrows; Figure 4 is a sectioned view of the evaporator taken along section line 4-4 in Fig. 2 and looking in the direction of the arrows; and Figure 5 is a perspective view of two tube pass plates spaced to reveal the interior configurations.

In the drawings, tube passes 10 are illustrated each of which consists of plate members 12 and 14. In Fig. 2, two tube passes are illustrated and part of a third. The tube passes 10 are stacked as shown in Fig. 2 to define a space 1 6 therebetween for the flow of air therebetween. The space 1 6 normally contains a corrugated metal centre structure 1 7 with fins 1 7' struck out therefrom for increasing the heat exchange efficiency. For clarity, only a portion of the centre structure 17 is illustrated.

In Fig. 1, the plates 12 and 14 are shown in their normal overlying relationship. The leftward portion of the drawing showing the top, exterior surface of the upper plate 1 2 while the rightward portion shows the interior surface of plate 1 4. As best seen in Fig. 5, the plates 1 2 and 14 are adapted to engage one another in stacked relation when positioned for assembly.

The individual plates 1 2 and 1 4 are identical and for stacking to form a tube pass, one of the plates is simply inverted and rotated 180 . Each plate has a flat peripheral edge portion 1 8 and the portions 1 8 of the two plates are formed so as to engage one another prior to being brazed together. The midportions 20, 22 of plates 1 2 and 14 are offset upwardly and downwardly respectively, from the edge portions 18. Thus, when the edges 1 8 engage, the general planes of midportions 20, 22 are spaced from one another.

A fluid, such as refrigerant in the evaporatur usage, is introduced into the tube pass at one end and is discharged at the other end.

Inlet and outlet manifolds 24, 26 of tube pass 10 are formed by outwardly offset and generally circular end portions 28 in the plates 1 2 and 1 4. An opening 30 is provided in the top surface of the offset portion 28 at one end of a plate and an opening 32 is provided, at the other end offset portion, with an outwardly raised flange portion 34. Thus, the plates are designed so that, upon assembly, the flange portion 34 surrounding opening 32 fittingly engages the opening 30. This provides a registering relationship between the plates of two different tube passes, as is evident from Fig. 2 Subsequently, the tube passes are brazed together to form an evaporator, a portion of which is shown in Fig. 2.

At one end of a plate near opening 30 and slightly outward from the flat edge portion 18, an upwardly turned edge portion 36 is formed. Similarly along the extended side edges 38, the edge portion outward from portion 1 8 is turned normally upward from the flat edge surface 1 8. This helps stiffen the plate.

To provide even distribution of fluid across a tube pass, four flow channels 40 are formed, as best shown in Figs. 1 and 4. The flow channels 40 permit fluid to pass from the inlet manifolds 24 into the intermediate flow portion formed between the intermediate surface portions 20, 22 of plates 1 2 and 1 4.

Likewise, similar channels 41 at the rightward end of the tube pass in Fig. 1 permit fluid to flow into the outlet manifold 26.

Fluid flow through the intermediate portions of the tube pass between raised surfaces 20, 22 is directed by a specific non-planar configuration of the intermediate surfaces 20, 22.

The surface areas 20, 22 are generally offset from the plane of the edge 1 8 in the same direction as the manifolds 28 but they are not strictly planar and include a particular ribbed formation including a plurality of relatively short-length and spaced ribs 42 which project downwardly from the surface areas 20 and 22 in the opposite direction from the offset end portions 28. The ribs 42 are relatively short-length depressions in the intermediate portion with a length in the illustrated embodiment of approximately one-third of the tube pass width. The ribs are aligned in rows in the tube path and labeled A, B and C in Fig. 1.

The fully illustrated evaporator has about 1 8 rows in each tube pass. The ribs depressions or channels 42, hereinafter referred to as ribs, in each row are inclined with respect to the direct flow line between the manifolds 24, 26 as seen in Fig. 1. Also evident from both Figs. 1 and 5 is the opposite orientation of the ribs 42 in the two plates of a single tube pass. This opposed angular orientation of the ribs 42 occurs as a result of the inversion of one plate during assembly. As mentioned earlier, one plate is inverted and rotated 180 with respect to the second plate before assembling. Thus, the orientation of the ribs 42 is reversed. As a result of this inversion, the ribs of one plate criss-cross corresonding ribs of the other plate.When the multiple contact points between crossed ribs are brazed, many flow paths are formed through and around the ribs. It should be noted that wherever the intermediate surfaces 20 and 22 engage one another in a tube pass, the plates are brazed tobether. These contact points are labeled X in Fig. 3.

Of particular importance in reducing the width of the tube pass without sacrificing heat exchange efficiency, is the particular advantageous formation in each row. With attention directed to the rightward end of the tube pass in Fig. 1 which shows a portion of lower plate 14, the row includes five full-length ribs 42ae. At either end of the row are formed partial length ribs 42fand 9. These are integrally joined with the offset edge portion 1 8 of the plate 12. The end ribs 42fand gand the next adjacent rib 42 overlap the ends of one another or are staggered, as viewed along the linear flow line between manifolds 24, 26.

Therefore, fluid flowing from manifold 24 to manifold 26 passes along at least a portion of the ribs 42 before passing around a brazed contact point X, then the flow enters another rib in an adjacent row and so on. Thus, the fluid zig-zags through the intermediate fluid flow space formed between portions 22 and 20, rather than flowing straight across. This greatly increases the turbulence and enhances heat exchange efficiency without undesirably increasing the pressure resistance to fluid flow. The efficiency and fluid distribution across the tube width is further encouraged by the formation of the partial-length ribs 42f and gwhich, in conjunction with the intermediate full length rib 42a-e, ensure flow of fluid at the edges 1 8 of the tube pass, thus forming a very even distribution of flow.

When the evaporator is used in an automobile air conditioning system, a housing having an opposite air inlet and outlet encloses the heat exchanger. Air then passes through spaces 1 6 and over centre material 1 7 and fins 17' therein. Means including resilient seal material supported by the housing (not shown) engage a surface along either end of the evaporator as described hereinafter. Projections or tabs 44 are formed integrally with plates 12, 14 adjacent the manifold configurations 28. The tabs 44 include a portion 46 coplanar with edge 1 8 and portions 48, 50 normal thereto. Also a portion 52 facing portion 46 is provided. The tabs 44 are located at either end of the inlet face of the evaporator as indicated in Fig. 1. Alignment of the tab portions 48 and 50 when the evaporator is assembled and brazed together produces a dam for blockage of airflow around the offset portions end 28 containing the manifolds 24, 26. Without this blockage of airflow, efficiency decreases and under some conditions it has been found that the air outlet temperature may increase by 2"F. The abutment of portions 52 helps secure the pieces and helps fill the gap between tube passes by providing surfaces for braze adhesion.

While only one embodiment of the subject invention has been illustrated and described in great detail, modifications to the tube pass are contemplated which would not fall outside the scope of the invention as claimed hereinafter.

Claims (4)

1. An elongate evaporator tube pass formed by a pair of plate members with edge portions 1 8 joined together and mid portions spaced apart to form a refrigerant enclosure for flow therebetween, opposite ends of the plates having outward offsets from the plane of the midportions to define inlet and outlet manifold enclosures and to form offset surfaces on adjacent tube passes for engagement together when in stacked relation to form airflow passages between adjacent midportions of the tube passes, a plurality of rows of separated ribs 42 formed in the midportion of each plate member and with the ribs angled obliquely to the length and width thereof, each row having at least one full length rib and a partial length rib adjacent and continuous with respective opposite edge portions of the plate, the ribs of each row in one plate overlapping and being staggered with respect to the ribs in the same row of the other plate and to ribs in the adjacent row of said one plate to prevent a linear flow path across the rows of ribs.

2. An elongate evaporator tube pass according to claim 1, in which the angled ribs of one tube pass plate member extend across the corresponding and adjacent angled ribs of the other plate member of the tube pass to form multiple contact points therewith and thus provide a tortuous flow path across the rows and around the contact points.

3. An elongate evaporate tube pass according to claim 1 or claim 2, in which each plate has, at its ends adjacent the manifold enclosures, projecting tabs and, upon stacking of the plates to form tube passes, facing tabs on adjacent plates are aligned to form walls to prevent leakage of air around the manifold enclosures and to direct air through the intermediate spaces between tube passes.

4. An elongate evaporator tube pass substantially as hereinbefore particularly described with reference to the accompanying drawings.