Patent Description:
An automotive vehicle is currently equipped with a heating, ventilating and air conditioning system, usually called the HVAC system, for thermally treating the air present or sent inside a passenger compartment of the automotive vehicle. The HVAC system is associated with a refrigerant circuit inside which a refrigerant fluid circulates. The refrigerant circuit comprises successively a compressor, a condenser or gas cooler, an expansion device and a heat exchanger. The heat exchanger is housed inside the HVAC system to allow a heat exchange between the refrigerant fluid and an air flow circulating inside the HVAC system, before being delivered inside the passenger compartment.

<CIT> discloses a heat exchanger according to the preamble of claim <NUM>.

According to a mode of operation of the refrigerant circuit, the heat exchanger is used as an evaporator to cool down the air flow. In this case, the refrigerant fluid is compressed inside the compressor, then the refrigerant fluid is cooled inside the condenser or gas cooler, then the refrigerant fluid expands within the expansion device and finally the refrigerant fluid cools down the air flow passing through the heat exchanger.

The heat exchanger comprises a first header box and a second header box between which a bunch of tubes is interposed. The first header box and the second header box are both arranged parallel to a longitudinal direction. The tubes are arranged between the first header box and the second header box, each tube having a first extremity in connection with the first header box and a second extremity in connection with the second header box. The tubes are also arranged in a first row of first tubes and a second row of second tubes that are parallel to each other and perpendicular to the longitudinal direction. The first tubes of the first row are in fluid communication with a first chamber of the first header box and a first chamber of the second header box. The second tubes of the second row are in fluid communication with a second chamber of the first header box and a second chamber of the second header box. The second chambers of the second header box are coupled together by a connecting means so that the refrigerant fluid can circulate from one to the other. One of the first chambers of the first header box, the inlet chamber, is equipped with a refrigerant fluid inlet through which the refrigerant fluid is admitted in the heat exchanger and the other chamber of the first header box, the outlet chamber, is equipped with a refrigerant fluid outlet through which the refrigerant fluid exits from the heat exchanger.

The chambers are partitioned in several portions by at least a partition wall located in the first header box and the second header box. That divides each row in several passes of tubes, the tubes of a same pass having their first extremities in communication with the same portion of the first chamber and having too their second extremities in communication with the same portion of the second chamber. In each pass, the refrigerant fluid is circulating in the same direction from one header box to the other header box as it is disclosed in the document <CIT>.

With such an arrangement of tubes, the temperature of the refrigerant fluid tends to be inhomogeneous from one pass to the other. Furthermore, within the same pass of tubes, the temperature of the refrigerant fluid from one tube to another tube tends to be different. Furthermore again, the temperature of the refrigerant fluid at the first extremity of the tubes of the same pass is different from one tube to another. Finally, within a same pass, the temperature of the refrigerant fluid in the same extremities of the tubes of the considered pass tends to be different from one tube to another tube. Especially, considering the tubes of the closest pass to the refrigerant fluid inlet, the temperature of the refrigerant fluid in the extremity of the tube close to the refrigerant fluid inlet is lower than the extremity opposite to the one close to the refrigerant fluid inlet. In other words, the refrigerant fluid tends not to reach the opposite extremity of the tubes of the extremity that is close to the refrigerant fluid inlet for those considered tubes. In this area, the temperature of the refrigerant fluid being higher, the air flow is badly cooled down there which decrease the global efficiency of the heat exchanger.

Therefore, there is a need of a heat exchanger that is arranged so that the temperature of the refrigerant fluid in the tubes of a same pass is as much homogeneous as possible.

The heat exchanger of the invention is a heat exchanger comprising a core and at least one header box that extends mainly in a longitudinal direction. The core comprises at least four passes distributed in two rows. Two first inlet-passes are part of a first row of the heat exchanger and two last outlet-passes are part of a second row of the heat exchanger. Each pass has a respective length measured along the longitudinal direction.

According to the invention, the sum of the length of the two first inlet-passes is equal +/-<NUM>% to the sum of the length of the two last outlet-passes, and the length of the first inlet-pass is bigger than the length of the last outlet-pass.

The heat exchanger can be recognized thanks to any of the following technical characteristics:.

The invention relates also to a heating, ventilating and air conditioning system comprising an air duct in which an air flow circulates and the said heat exchanger, the said heat exchanger being located in the air duct so that the air flow circulates firstly through the first row and secondly through the second row.

The invention relates also to a refrigerant fluid circulation circuit comprising at least the said heat exchanger.

The invention relates also to a utilization of the said heat exchanger as an evaporator in the said refrigerant fluid circuit.

Other specificities, details and characteristics of the present invention will be highlighted thanks to the following description, given for general guidance, in relation with the following figures:.

In the Figures, a heat exchanger <NUM> according to the invention is shown in a coordinate system Oxyz in which Ox axis is a longitudinal axis, Oy axis is a lateral axis and Oz axis is a vertical axis.

In <FIG>, a heat exchanger <NUM> comprises a core <NUM> disposed between two header boxes <NUM>. The core <NUM> is the part of the heat exchanger <NUM> that is dedicated to enable a heat exchange between a refrigerant fluid <NUM> circulating in the heat exchanger <NUM> and an air flow <NUM> passing through the heat exchanger <NUM>. Both header boxes <NUM> extend mainly in a longitudinal direction A1 that is parallel to the Ox axis.

The core <NUM> comprises a plurality of tubes <NUM> that are interposed between the header boxes <NUM>. The tubes <NUM> extend in a vertical direction A2 that is parallel to the vertical axis Oz. According to different embodiments of the invention, the tube <NUM> can be made from a folded metallic sheet or the tube <NUM> can be extruded or the tube <NUM> can be made by the assembling of two plates that are delimitating together a canal for the refrigerant fluid <NUM> circulation.

The tubes <NUM> are arranged in two rows <NUM>, <NUM> comprising a first row <NUM> of tubes <NUM> and a second row <NUM> of tubes <NUM>, both rows <NUM>, <NUM> being respectively arranged parallel to a longitudinal plan P1, the longitudinal plan P1 being parallel to the Oxz plan. Each tube <NUM> having a first extremity <NUM> and a second extremity <NUM>, the tubes <NUM> have all their first extremities <NUM> in communication with a first header box <NUM> and have all their second extremities <NUM> in communication with a second header box <NUM>.

Each header box <NUM> comprises a first chamber <NUM> and a second chamber <NUM> that are watertight one to the other. The first chambers <NUM> of the header boxes <NUM> are in fluid connection with the extremities <NUM>, <NUM> of the tubes <NUM> of the first row <NUM> of tubes <NUM>. The second chambers <NUM> of the header boxes <NUM> are in fluid connection with the extremities <NUM>, <NUM> of the tubes <NUM> of the second row <NUM> of tubes <NUM>.

The first extremities <NUM> of the tubes <NUM> in the first row <NUM> are in fluid communication with the first chamber <NUM> of the first header box <NUM> and the second extremities <NUM> of the tubes <NUM> in the first row <NUM> are in fluid communication with the first chamber <NUM> of the second header box <NUM>. The second extremities <NUM> of the tubes <NUM> in the second row <NUM> are in fluid communication with the second chamber <NUM> of the first header box <NUM> and the second extremities <NUM> of the tubes <NUM> in the second row <NUM> are in fluid communication with the second chamber <NUM> of the second header box <NUM>.

The heat exchanger <NUM> is equipped with a refrigerant fluid inlet <NUM> through which the refrigerant fluid <NUM> is admitted inside the heat exchanger <NUM>. The refrigerant fluid inlet <NUM> equips the first chamber <NUM> of the first header box <NUM>. The heat exchanger <NUM> is equipped with a refrigerant fluid outlet <NUM> through which the refrigerant fluid <NUM> is evacuated from the heat exchanger <NUM>. The refrigerant fluid outlet <NUM> equips the second chamber <NUM> of the same first header box <NUM>.

The refrigerant fluid inlet <NUM> and the refrigerant fluid outlet <NUM> are located on the same edge side of the heat exchanger <NUM>. The refrigerant fluid inlet <NUM> and the refrigerant fluid outlet <NUM> are arranged on the same header box <NUM>. Other localization of the refrigerant fluid inlet <NUM> and the refrigerant fluid outlet <NUM> are possible.

The heat exchanger <NUM> comprises communication means <NUM> that are interposed between the first chamber <NUM> of the second header box <NUM> and the second chamber <NUM> of the second header box <NUM>, the communication means <NUM> enabling a fluid circulation between the tubes <NUM> of the first row <NUM> and the tubes <NUM> of the second row <NUM>.

According to different embodiments, the communication means <NUM> are located inside a volume of the core <NUM> of the heat exchanger <NUM> or the communication means <NUM> are located outside the volume of the core <NUM> of the heat exchanger <NUM>.

The core <NUM> comprises these tubes <NUM> and two contiguous tubes <NUM> of the same row <NUM>, <NUM> are separated by corrugated fins <NUM> that are enhancing the heat exchange between the refrigerant fluid <NUM> and the air flow <NUM>.

The first row <NUM> is a downwind-side row of the heat exchanger <NUM> and the second row <NUM> is an upwind-side row of the heat exchanger <NUM>.

The chambers <NUM>, <NUM> are equipped with partition walls <NUM> that are dividing the chambers <NUM>, <NUM> in several portions <NUM>. The partition walls <NUM> are arranged in respective lateral plans P2 that are parallel to the Oyz plan.

The core <NUM> comprises several passes <NUM> of tubes <NUM>, the tubes <NUM> of a same pass <NUM> have all their first extremities <NUM> in communication with the same portion <NUM> of the first chamber <NUM> of the first header box <NUM> and have all their second extremities <NUM> in communication with the same portion <NUM> of the second chamber <NUM> of the second header box <NUM>. In other words, a pass <NUM> is a section of a row <NUM>, <NUM>, either the first row <NUM> or the second row <NUM>, that comprises a plurality of tubes <NUM>, where the refrigerant fluid <NUM> circulates in all the tubes <NUM> along the same direction. Two passes <NUM> of a same row <NUM>, <NUM> are separated by a partition wall <NUM>.

Each pass <NUM> comprises a plurality of tubes <NUM> that are regularly distributed along the longitudinal direction A1 parallel to the Ox axis, a tube pitch of each pass <NUM> being identical at +/-<NUM>%.

The total number of passes <NUM> of the heat exchanger <NUM> is a pair number. According to different embodiments of the invention, the heat exchanger <NUM> comprises strictly four passes <NUM>, or the heat exchanger <NUM> comprises strictly six passes <NUM>, or the heat exchanger <NUM> comprises strictly eight passes <NUM>.

The passes <NUM> are also distributed in the two rows <NUM>, <NUM>. The passes <NUM> comprise inlet-passes <NUM> that are located in the first row <NUM> and the outlet-passes <NUM> that are located in the second row <NUM>. The inlet-passes <NUM> are arranged in an inlet plan that is parallel to the longitudinal plan P1 and the outlet-passes <NUM> are arranged in an outlet plan that is also parallel to the longitudinal plan P1. The inlet plan comprises the refrigerant fluid inlet <NUM> and the outlet plan comprises the refrigerant fluid outlet <NUM>.

At least two first inlet-passes <NUM> are part of the first row <NUM> of the heat exchanger <NUM> and at least two last outlet-passes <NUM> are part of the second row <NUM> of the heat exchanger <NUM>. The two first inlet-passes <NUM> are immediately contiguous to each other.

A first inlet-pass <NUM> is the inlet-pass <NUM> that is equipped with the refrigerant fluid inlet <NUM> of the heat exchanger <NUM>. This means that the first inlet-pass <NUM> is the inlet-pass <NUM> admitting the refrigerant fluid <NUM> inside the heat exchanger <NUM>. The two first inlet-passes <NUM> comprise the first inlet-pass <NUM> and the immediate contiguous inlet-pass <NUM> to the first inlet-pass <NUM>.

A last outlet-pass <NUM> is the outlet-pass <NUM> that is equipped with the refrigerant fluid outlet <NUM> from the heat exchanger <NUM>. The two last outlet-passes <NUM> comprise the last outlet-pass <NUM> and the immediate contiguous outlet-pass <NUM> to the last outlet-pass <NUM>. This means that the last outlet-pass <NUM> is the outlet-pass <NUM> from which the refrigerant fluid <NUM> exits from the heat exchanger <NUM>. The two first outlet-passes <NUM> are immediately contiguous to each other.

The passes <NUM> of the heat exchanger <NUM> form a refrigerant fluid path along which the refrigerant fluid <NUM> can circulate from the refrigerant fluid inlet <NUM> to the refrigerant fluid outlet <NUM>, by flowing first within the inlet-passes <NUM> and then within the outlet-passes <NUM>. Within the first row <NUM>, the refrigerant fluid <NUM> circulates from the first inlet-pass <NUM> to the last inlet-pass <NUM>. Within the second row <NUM>, the refrigerant fluid <NUM> circulates from the first outlet-pass <NUM> to the last outlet-pass <NUM>. Within the first row <NUM>, the refrigerant fluid <NUM> circulates from the first inlet-passes <NUM> and then in the other passes <NUM> of the first row <NUM>. Within the second row <NUM>, the refrigerant fluid <NUM> exits from the heat exchanger <NUM> from the last outlet-passes <NUM> after having circulated inside the other outlet-passes <NUM>.

In <FIG>, each pass <NUM> has a respective length measured L along the longitudinal direction, wherein the sum of the length L of the two first inlet-passes <NUM> is equal +/-<NUM>% to the sum of the length L of the two last outlet-passes <NUM>. The length L of the first inlet-pass <NUM> is bigger than the length L of the last outlet-pass <NUM>.

The length L of each pass <NUM> is measured from a first longitudinal side <NUM> of a pass <NUM> to a second longitudinal side <NUM> of the pass <NUM> in a parallel plan to the longitudinal plan P1.

The length L of the last inlet-pass <NUM> is equal to the length L of the first outlet-pass <NUM>.

<FIG> illustrates a refrigerant fluid circulation circuit <NUM> inside which circulates the refrigerant fluid <NUM>. Following a direction S1 of circulation of the refrigerant fluid <NUM> inside the refrigerant circulation circuit <NUM>, the refrigerant fluid circulation circuit <NUM> successively comprises a compressor <NUM> for compressing the refrigerant fluid <NUM>, a condenser or a gas cooler <NUM> for cooling the refrigerant <NUM>, an expansion device <NUM> inside which the refrigerant fluid <NUM> expands and the heat exchanger <NUM>. The heat exchanger <NUM> is accommodated inside an air duct <NUM> of a heating, ventilating and air conditioning system <NUM> inside which circulates the air flow <NUM>. The heat exchanger <NUM> allows a heat transfer between the refrigerant fluid <NUM> and the air flow <NUM> coming into contact with it and/or passing through it, as illustrated in <FIG>. According to the operating mode of the refrigerant circuit <NUM> described above, the heat exchanger <NUM> is used as an evaporator for cooling the air flow <NUM>, during the passage of the air flow <NUM> in contact with and/or from one side of the heat exchanger <NUM>.

Several modifications and improvements might be applied by the person skilled in the art to a heat exchanger <NUM> as defined above.

In any case, the invention cannot and should not be limited to the embodiments specifically described in this document, as other embodiments might exist. The invention shall spread to any equivalent mean and any technically operating combination of means.

Claim 1:
Heat exchanger (<NUM>) comprising a core (<NUM>) and at least one header box (<NUM>) that extends mainly in a longitudinal direction (A1), said core (<NUM>) comprising at least four passes (<NUM>) distributed in two rows (<NUM>, <NUM>), with two first inlet-passes (<NUM>) being part of a first row (<NUM>) of the heat exchanger (<NUM>) and two last outlet-passes (<NUM>) being part of a second row (<NUM>) of the heat exchanger (<NUM>), each pass (<NUM>) having a respective length (L) measured along the longitudinal direction (A1), characterised in that the sum of the length (L) of the two first inlet-passes (L) is equal +/-<NUM>% to the sum of the length (L) of the two last outlet-passes (L), and the length (L) of the first inlet-pass (L) is bigger than the length (L) of the last outlet-pass (<NUM>).