US20120168117A1

US20120168117A1 - Automotive HVAC Diffuser With Cooperating Wall Guide And Vane

Info

Publication number: US20120168117A1
Application number: US12/984,178
Authority: US
Inventors: Vivek A. Jairazbhoy; Mehran Shahabi
Original assignee: Automotive Components Holdings LLC
Current assignee: Visteon Global Technologies Inc; Automotive Components Holdings LLC
Priority date: 2011-01-04
Filing date: 2011-01-04
Publication date: 2012-07-05

Abstract

A case for an HVAC system has at least two molded shells joined together along a parting line to enclose a heat exchanger chamber, a blower chamber, and a diffuser section. The diffuser section includes a floor, a ceiling, an outer wall, and an inner wall around a longitudinal axis. The walls provide an airflow path through the diffuser between the blower and heat exchanger chamber, and the airflow path makes a substantially right angle turn into the heat exchanger chamber which results in a tendency to create a high flow region at the outer wall because of centrifugal effects. The outer wall is shaped to form a wall guide partially projecting into the airflow path in the diffuser, wherein the wall guide has an upstream encroaching surface and a downstream retreating surface so that a portion of the guided air is directed from the outer wall toward the inner wall. At least one of the floor or the ceiling includes a vane projecting into and deflecting the guided air in the airflow path, wherein the vane has an upstream end proximate to the wall guide and a downstream end extending toward the heat exchanger chamber for initiating a portion of the substantially right angle turn for a portion of the airflow.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

Not Applicable.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

Not Applicable.

BACKGROUND OF THE INVENTION

The present invention relates in general to a case for an automotive HVAC system, and, more specifically, to wall guide and vane features for improving air flow into an evaporator core.
In a typical automotive HVAC system, a blower delivers fresh or recirculated air to heat exchangers (e.g., an evaporator) which is then distributed to the passenger cabin via ducts. A diffuser couples the air stream from the blower to the evaporator. Due to space requirements, the diffuser turns the air stream by about 90° for delivery to the evaporator. Conventional blower/diffuser combinations produce a non-uniform flow that tends to produce high flows on the outer periphery of the diffuser due to centrifugal forces, and the high flow becomes concentrated at one end of the evaporator.
A uniform velocity distribution at the diffuser outlet and into the evaporator is very desirable to ensure efficient evaporator performance, higher total air flow, and reduced noise generation as the air passes through the evaporator core. Prior attempts to improve the uniformity of the air flow have included the addition of aerodynamic vanes in the interior or at the walls of the diffuser.
The diffuser is normally made as a molded plastic part. The height of interior vanes from a corresponding wall have been restricted due to limitations in the molding process and limitations associated with handling of the part after molding (e.g., breakage of the vanes). Therefore, vanes can affect the air flow near to the diffuser walls but are less able to affect air flow near the midline of the diffuser. Furthermore, the die draw of the molding process does not allow vanes to extend from walls that are perpendicular to one another (i.e., vanes cannot extend from both the curved outer peripheral wall and either of the transverse (i.e., floor and ceiling) walls in the same molded section).
For similar reasons, structures built directly into the side walls have a greater influence on air flow in the regions of those walls. Prior art systems have, nevertheless, achieved some improvements in flow uniformity using vanes and wall structures to diffuse the air stream. However, it would be desirable to reduce the complexity and to increase the efficiency of such structures.

SUMMARY OF THE INVENTION

The present invention overcomes limitations of the prior art by combining effects of a wall guide and a vane together to achieve uniform airflow across the evaporator core.
In one aspect of the invention, a case for an HVAC system in a transportation vehicle comprises at least two molded shells joined together along a parting line to receive a heat exchanger and a blower. The shells enclose a heat exchanger chamber, a blower chamber, and a diffuser section for guiding air from the blower chamber to the heat exchanger chamber. The diffuser section includes a floor, a ceiling, an outer wall, and an inner wall around a longitudinal axis between an inlet and an outlet. The walls provide an airflow path through the diffuser between the blower and heat exchanger chamber, and the airflow path makes a substantially right angle turn into the heat exchanger chamber which results in a tendency to create a high flow region at the outer wall because of centrifugal effects. The outer wall is shaped to form a wall guide partially projecting into the airflow path in the diffuser, wherein the wall guide has an upstream encroaching surface and a downstream retreating surface so that a portion of the guided air is directed from the outer wall toward the inner wall. At least one of the floor or the ceiling includes a vane projecting into and deflecting the guided air in the airflow path, wherein the vane has an upstream end proximate to the wall guide and a downstream end extending toward the heat exchanger chamber for initiating a portion of the substantially right angle turn for a portion of the airflow.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing blower, diffuser, and evaporator sections of an HVAC case for a first embodiment of the invention.

FIG. 2 is a schematic diagram showing a wall guide in greater detail.

FIG. 3 is a close-up perspective view of a wall guide according to one embodiment.

FIG. 4 is a close-up perspective view of a wall guide according to another embodiment.

FIG. 5 is a plan view showing a preferred relationship between a wall guide and vane in greater detail.

FIG. 6 is an interior perspective view of an alternative embodiment showing blower and diffuser sections of an HVAC case.

FIG. 7 is an interior perspective view of another alternative embodiment including cooling fins of a variable blower control.

FIG. 8 illustrates an alternative vane shape.

FIG. 9 is a schematic diagram showing blower, diffuser, and evaporator sections of an HVAC case having an alternative relationship between the vane and wall guide.

FIG. 10 is a perspective view of an embodiment wherein vanes provide airflow shaping near floor and ceiling areas and a wall guide provides airflow shaping in a parting-line area.

FIG. 11 is a top view of the lower shell portion along line 11-11 of FIG. 10 coinciding with the parting line.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring now to FIG. 1, an HVAC case 10 includes a blower section 11, an evaporator section 12, and an intervening diffuser section 13. Blower section 11 receives a motor-driven bladed wheel (not shown) for created an air flow of fresh or recirculated air that is guided through diffuser section 13 to an evaporator core (not shown) mounted in evaporator section 12. Guided air 14 follows an airflow path and is required to make an approximately right angle turn in order to enter evaporator is section 12.
Diffuser section 13 includes an outer wall 15, an inner wall 16, a floor 17, and a ceiling (not shown) that surround a generally longitudinal axis of diffuser section 13 that extends between an inlet from the blower section 11 and an outlet to evaporator section 12. Due to centrifugal affects, a region of high flow is generally associated with outer wall 15 which results in non-uniform entry of the air flow into evaporator section 12. To improve uniformity and to reduce the generally high flow along outer wall 15, the present invention employs a wall guide 20 and a vane 21 for interacting with the guided air 14 and redirecting it in a beneficial manner.
Wall guide 20 is shown in greater detail in FIG. 2. Wall guide 20 has an encroaching surface 25 on its upstream side and a retreating surface 26 on its downstream side. A transition 27 lies between surfaces 25 and 26. Wall guide 20 functions to turn some of the air away from a region 30 (that would otherwise have a high flow) into a region 31 of typically lesser flow, thereby reducing or eliminating local regions of lower or higher velocity in the flow, and thus increasing evaporator coverage.
One embodiment of a wall guide 35 is shown in greater detail in FIG. 3. Outer wall 15 is part of an injection molded case component or shell, typically formed of a thermal plastic. Wall guide 35 is formed as a depression into the molded shell and has an upstream encroaching surface 36 and a downstream retreating surface 37. Preferably, upstream surface 36 has a generally concave shape for efficient deflection of airflow and low noise generation. Surface 36 may be comprised a curved plane (i.e., wherein a longitudinal cross-section reveals the concave shape). Edges 38 and 39 may be rounded to avoid turbulence. A radius of curvature for the concave upstream surface 36 is preferably in the range of about 15 to about 100 mm.
The shape of downstream surface 37 is less critical. As shown in FIG. 3, a generally flat or slightly convex shape is acceptable. Such shapes may have manufacturing advantages. More preferably, however, a concave shape may be employed as shown in FIG. 4. Thus, a wall guide 40 has a concave upstream surface 41 and a concave downstream surface 42, with a transition 43 having a generally convex shape. The generally concave shape of downstream surface 42 preferably has a radius of curvature greater than about 100 mm. The generally convex shape of transition 43 preferably has a radius of curvature less than about 40 mm. The curvatures of the surfaces can alternatively vary continuously over the length of the wall guide, with the three sections merging smoothly into one another. The contours can be optimized to delay the point of separation of flow (e.g., using design techniques known for constructing Coanda airfoils).
Use of a wall guide together with a vane is shown in FIG. 5. A wall guide 45 formed in outer wall 15 has an upstream surface 46 and downstream surface 47. A vane 50 projects upward from floor 17 and has an upstream end 51 proximate to wall guide 45 and a downstream end 52 that extends down the airflow path and toward the evaporator chamber having a curvature that initiates a portion of the substantially right angle turn to be made for a portion of the air flow that flows to the initial portion of the evaporator chamber. Upstream end 51 extends in a direction substantially parallel to the longitudinal axis of the diffuser and preferably has its tip proximate to and directly opposed to a transition 48 of wall guide 45. Because downstream surface 47 is retreating, a cross-sectional area between vane 50 and wall guide 45 steadily increases in the airflow direction due to an increasing width from a first gap 55 to a second gap 56. Due to the increasing cross-sectional area, the guided air that passes through a region 57 has a reduction in its speed resulting from the Bernoulli Effect. By slowing down the airflow in this region, the beneficial effect of wall guide 45 is enhanced and the tendency of a concentrated flow along outer wall 15 is counteracted. Moreover, the curvature of downstream end 52 further distributes airflow toward the initial side of the evaporator chamber normally receiving a lower flow. Thus, a high degree of uniformity of airflow can be achieved.
FIG. 6 shows yet another embodiment of an HVAC case 60 including a blower section 61 and a diffuser section 62. Case 60 is comprised of a molded shell having a upper shell 63 and a lower shell 64. An outer wall of diffuser section 62 includes a wall guide 65 in upper shell 63 and a wall guide 66 in lower shell 64. A guide vane 67 extends from floor 68 and interacts with wall guides 65 and 66 as previously described. If desired, another vane can be formed extending from ceiling 69 of diffuser section 62. Any combination of wall guides and vanes could be used. The beneficial effects of the invention can still be achieved even if there is only one wall guide and one vane and they are formed in the opposite shells.
FIG. 7 shows an example with a lower shell 70 having a wall guide 71 and an upper shell 72 having a vane 73. Cooling fins 74 of a variable blower control (VBC) electronic module mounted to the outside of the case can also enter the airflow path to further direct the guided air in a desired direction.
The cross-sectional shape of the vane may be streamlined as shown in FIG. 8. Thus, a vane 80 has an extended teardrop shape with a rounded upstream end (leading edge) 81 and a tapered downstream end (trailing edge) 82. The teardrop shape can be designed using Coanda airfoil design techniques. It is effective at avoiding undesirable recirculations or turbulence of air as it separates from vane 80.
FIG. 9 illustrates an alternative relationship between a wall guide and a vane wherein a wall guide 85 and vane 86 track one another in a side-by-side relationship to define a curved air channel 87. Air flowing through channel 87 is deflected along a curving trajectory toward the entrance to evaporator section 12. The curved channel keeps the airflow attached to the vane for longer, and is more effective at bending it toward evaporator section 12.
FIG. 10 is an end, perspective view looking generally along an airflow path and illustrating another alternative relationship between a wall guide and vanes. An upper shell 90 and a lower shell 91 meet along a parting line 96. Upper shell 90 has a vane 92 extending from its ceiling, and lower shell 91 has a vane 93 extending from its floor. The shells also form a wall guide 94, 95 in an outer wall such that wall guide 94, 95 spans the region around parting line 96. Wall guide 94, 95 modifies the airflow path in the parting-line region (between the floor and ceiling, and therefore between vanes 92 and 93) where the vanes cannot operate due to limitations in height that can be created with injection molding.
Vane 93 extends to a height 97 above the floor. Parting line 96 is at a height 98 above the floor. The height of a vane may typically be limited to about 50 to about 75 millimeters. This may comprise about 60% to 70% of the distance of the floor or ceiling to the parting line. As a result, about 30% to 40% or more of the height of the airflow between floor and ceiling cannot be effectively shaped by the vanes. Thus, FIG. 10 uses a wall guide to provide at least a partially modified airflow in the parting-line region. Wall guide 94, 95 may also extend over substantially the entire floor to ceiling distance as shown in FIGS. 10 and 11.

Claims

1. A case for an HVAC system in a transportation vehicle, comprising at least two molded shells joined together along a parting line to receive a heat exchanger and a blower, wherein the shells enclose a heat exchanger chamber, a blower chamber, and a diffuser section for guiding air from the blower chamber to the heat exchanger chamber;

wherein the diffuser section includes a floor, a ceiling, an outer wall, and an inner wall around a longitudinal axis between an inlet and an outlet;

wherein the walls provide an airflow path through the diffuser between the blower and heat exchanger chamber, and wherein the airflow path makes a substantially right angle turn before entering the heat exchanger chamber which results in a tendency to create a high flow region at the outer wall because of centrifugal effects;

wherein the outer wall is shaped to form a wall guide partially projecting into the airflow path in the diffuser, wherein the wall guide has an upstream encroaching surface and a downstream retreating surface so that a portion of the guided air is directed from the outer wall toward the inner wall; and

wherein at least one of the floor or the ceiling includes a vane projecting into and deflecting the guided air in the airflow path, wherein the vane and wall guide cooperate to mutually direct the guided air from the outer wall toward the inner wall.

2. The case of claim 1 wherein the vane extends to a first height which is less than about 70 percent of a height of the parting line, and wherein the wall guide spans a region around the parting line.

3. The case of claim 1 wherein the vane has an upstream end proximate to the wall guide and a downstream end extending toward the heat exchanger chamber for initiating a portion of the substantially right angle turn for a portion of the airflow.

4. The case of claim 1 wherein at least a portion of the upstream end of the vane extends substantially parallel to the local flow so that a region of the airflow path between the vane and the downstream returning surface has an increasing cross-sectional area that causes guided air passing through the region to have a reduction in speed by the Bernoulli Effect.

5. The case of claim 1 wherein the downstream end of the vane has an extended teardrop shape.

6. The case of claim 1 wherein the upstream encroaching surface of the wall guide includes a generally concave shape with a radius of curvature in the range of about 15 to about 100 millimeters.

7. The case of claim 1 wherein the downstream retreating surface of the wall guide includes a generally concave shape with a radius of curvature greater than about 100 millimeters.

8. The case of claim 1 wherein the wall guide further includes a transition between the upstream encroaching surface and the downstream retreating surface having a generally convex shape with a radius of curvature less than about 40 millimeters.

9. The case of claim 1 wherein the cooperation of the wall guide and vane is comprised of the wall guide and vane being disposed in a side-by-side relationship to define a curved air channel, whereby the guided air is deflected along a curving trajectory toward the heat exchanger chamber.