Evaporator in a refrigerant circuit B

Abstract

An evaporator in a refrigerant circuit, having a bottom-side inlet chamber which is connected in flow terms to an evaporator outlet side via evaporator tubes, a separator being integrated into the evaporator inlet chamber, in which separator a refrigerant which is expanded in an expansion member is divided as a two-phase liquid/vapour mixture into a vapour phase and into a liquid phase which is separate therefrom, the vapour phase being conducted via a bypass line to the evaporator outlet side, and the liquid phase being conducted counter to the direction of gravity into the evaporator tubes, to be precise at least one evaporator tube being a flat tube with a plurality of micro-channels, through which the refrigerant is guided, wherein, as a first flat tube, the evaporator flat tube is a constituent part of a first evaporator tube set which guides the refrigerant from the bottom-side inlet chamber counter to the direction of gravity into an upper-side deflecting chamber, and wherein the refrigerant is guided back from the upper-side deflecting chamber via at least one second flat tube.

Claims

1. An evaporator in a refrigerant circuit, comprising: an inlet chamber fluidly connected to an evaporator outlet chamber via evaporator tubes, and a separator integrated into the evaporator inlet chamber, the separator having an expansion member in which a refrigerant is expanded as a two-phase liquid/vapour mixture and then divided into a vapour phase and into a liquid phase which is separate therefrom, wherein the vapour phase and the liquid phase both exit the separator and collect in the same inlet chamber, wherein the vapour phase is conducted via a bypass line to the evaporator outlet chamber, wherein the liquid phase is conducted counter to the direction of gravity into the evaporator tubes, wherein at least one evaporator tube is a flat tube with a plurality of micro-channels, through which the refrigerant is guided, wherein, as a first flat tube, the evaporator flat tube is a constituent part of a first evaporator tube set which guides the refrigerant from the inlet chamber counter to the direction of gravity into a deflecting chamber, wherein the refrigerant is guided back from the deflecting chamber via at least one second flat tube which is a constituent part of a second evaporator tube set into a compressor chamber which is connected in flow terms to a suction side of a compressor, and wherein all the micro-channels of the first flat tube provide a flat tube flow cross section which is greater than the flat tube flow cross section which is provided by all the micro-channels of the second flat tube wherein a flow cross section which is provided by the micro-channels of the flat tube is reduced on account of the phase separation which takes place in the separator, wherein the inlet chamber is delimited by a chamber bottom, side walls which are raised from the chamber bottom in an evaporator height direction, and a chamber top wall, wherein the first evaporator flat tube protrudes through the chamber top wall into the inlet chamber in the evaporator height direction in such a way that orifice openings of the micro-channels are spaced apart from the chamber bottom by a spacing, wherein the liquid phase collects in the inlet chamber with a filling level, wherein the liquid phase micro-channel is dipped with at least one of a liquid phase micro-channel orifice opening into the liquid phase which is collected in the inlet chamber, and wherein the vapour phase micro-channel is positioned with a vapour phase micro-channel orifice opening above the liquid phase level by a height offset.

2. The evaporator according to claim 1, wherein the micro-channels of the first flat tube are divided into at least one vapour phase micro-channel and into at least one liquid phase micro-channel, wherein the vapour phase micro-channel forms the bypass line, and exclusively the liquid phase flows into the liquid phase micro-channel.

3. The evaporator according to claim 1, wherein the orifice opening of the vapour phase micro-channel is spaced from the chamber bottom to a greater extent than the spacing of the orifice opening of the liquid phase micro-channel.

4. The evaporator according to claim 1, wherein the evaporator flat tube has a right-angled flat profile cross section, with narrow sides and flat sides which lie perpendicular to one another in each case, wherein the micro-channels are arranged between the flat tube narrow sides in an aligned manner at least in one row behind one another in a parallel arrangement.

5. The evaporator according to claim 1, wherein the first flat tube and the second flat tube are arranged behind one another in an evaporator depth direction, wherein the flat sides of the flat tubes lie in height planes which are defined between the evaporator depth direction and an evaporator height direction, and/or wherein the first flat tubes in the first evaporator tube set and the second flat tubes in the second evaporator tube set are provided in identical numbers.

6. The evaporator according to claim 1, wherein the flat tube narrow sides are spaced apart from one another over a flat tube width, and the flat tube flat sides are spaced apart from one another over a flat tube thickness.

7. The evaporator according to claim 1, wherein each micro-channel of the flat tube has a micro-channel flow cross section, and the micro-channel flow cross sections of all the micro-channels of the flat tube are identical.

8. The evaporator according to claim 6, wherein the number of micro-channels in the first flat tube is greater than the number of micro-channels in the second flat tube, and/or the flat tube width of the first flat tube is greater than the flat tube width of the second flat tube, and/or the flat tube thickness of the first flat tube is smaller than the flat tube thickness of the second flat tube.

9. The evaporator according to claim 6, wherein the number of micro-channels in the first flat tube is 29, and/or the number of micro-channels in the second flat tube is 19, and/or the flat tube width of the first flat tube is 27 mm and/or the flat tube width of the second flat tube is 18 mm, and/or the flat tube thickness of the first flat tube is 1.28 mm and/or the flat tube thickness of the second flat tube is 1.35 mm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the following text, one exemplary embodiment of the invention is described using the appended figures, in which:

(2) FIG. 1 shows a block circuit diagram of a refrigerant circuit of a vehicle air conditioning system;

(3) FIG. 2 shows a roughly diagrammatic perspective part view of the evaporator which is connected into the refrigerant circuit;

(4) FIG. 3 shows details of a side sectional view of the evaporator;

(5) FIG. 4 shows details of another side sectional view of the evaporator;

(6) FIG. 5 shows a detailed view of the evaporator;

(7) FIG. 6 shows another detailed view of the evaporator; and

(8) FIG. 7 shows another detailed view of the evaporator.

DETAILED DESCRIPTION

(9) FIG. 1 shows a closed refrigerant circuit for, for example, a vehicle air conditioning system. An evaporator 1, a compressor 3, a condenser 5 and an expansion member 7 are connected into the refrigerant circuit. A separator 9 is connected between the expansion member 7 and the evaporator 1, in which separator 9 a phase separation takes place. During air conditioning operation, a vaporous refrigerant which comes from the evaporator 1 is compressed in the compressor 3 and is conducted into the condenser 5. The condenser 5 can be arranged by way of example in the front end of the vehicle and can be flowed through by the air stream. As a result, the refrigerant condenses into its liquid phase with the dissipation of thermal energy. The liquid refrigerant is expanded in the expansion member 7 which is connected downstream in flow terms to form a two-phase liquid/vapour mixture 10 (FIG. 7) which is fed to the separator 9. In the separator 9, the liquid phase 11 of the refrigerant is separated from its vapour phase 13. The liquid phase 11 is fed via a low-pressure line 15 (FIG. 1 or 2) to the evaporator 1, whereas the vapour phase 13 is guided via a bypass line 17 to the outlet side 22 (FIG. 3) of the evaporator 1. During air conditioning operation, the evaporator 1 is flowed through by an air flow L which is guided into the vehicle interior compartment and provides thermal energy while being cooled, by means of which thermal energy the refrigerant liquid phase 11 evaporates into the vapour phase 13 in the evaporator 1. The vapour phase 13 which is produced in the evaporator 1 is conducted via the evaporator outlet 22 to the suction side of the compressor 3.

(10) FIG. 2 indicates the evaporator 1 structurally in a perspective illustration to the extent that it is required for understanding the invention. Accordingly, the evaporator 1 has a bottom-side distributor housing 19 which is divided in FIG. 3 into an inlet chamber 21 and into an outlet chamber 23 which are separated from one another in a fluid-tight manner via a dividing wall 25. The separator 9 which will be described later is integrated into the evaporator inlet chamber 21, into which separator 9 the refrigerant which is expanded to a low pressure in the expansion member 7 is introduced as a two-phase liquid/vapour mixture 10 (FIG. 7) and is separated into the vapour phase 13 and into the liquid phase 11 which is separate therefrom.

(11) In FIG. 2, the evaporator 1 has a first evaporator tube set 29, in which the refrigerant which is collected in the bottom-side inlet chamber 21 is conducted in an evaporator height direction z (that is to say, counter to the direction of gravity) as far as into an upper-side deflecting chamber 31 which is indicated in FIG. 3. In the deflecting chamber 31, the refrigerant flow path K is deflected, as shown by way of an arrow in FIG. 3. The refrigerant is returned from the upper-side deflecting chamber 31 via a second evaporator tube set 33 (FIG. 2) into the bottom-side outlet chamber 23 (FIG. 3). The outlet chamber 23 is flow-connected via the evaporator outlet side 22 to the suction side of the compressor 3.

(12) The evaporator 1 which is shown in the figures is realised as a cross-counterflow evaporator. Accordingly, the air flow L which is to be cooled and is guided into the vehicle interior compartment is guided in a crossflow first of all through the second evaporator tube set 33 and then through the first evaporator tube set 29.

(13) In accordance with FIG. 2, the bottom-side distributor housing 19 of the evaporator 1 is of elongate configuration in an evaporator transverse direction y. A plurality of first flat tubes 35 which are constituent parts of the first evaporator tube set 29 are arranged behind one another and at a spacing in the evaporator transverse direction y in an aligned manner in a parallel arrangement, to be precise with the formation of intermediate spaces 37, through which air flows. In FIG. 2, the second evaporator tube set 33 has second flat tubes 39. Each of the second flat tubes 39 is arranged in alignment behind a corresponding first flat tube 35 in each case in an evaporator depth direction x. The number of first flat tubes 35 in the first evaporator tube set 29 and the number of second flat tubes 39 in the second evaporator tube set 33 are identical.

(14) FIGS. 5 and 6 in each case show a first flat tube 35 and a second flat tube 39 in cross section. Accordingly, the two flat tubes 35, 39 in each case have a number of micro-channels 41. In FIGS. 5 and 6, the flat tubes 35, 39 are configured with a right-angled flat profile cross section, to be precise with narrow sides 43 and flat sides 45 which lie opposite one another in each case. The narrow sides 43 of the flat tubes 35, 39 are spaced apart from one another over a flat tube width b.sub.1, b.sub.2, whereas the flat tube flat sides 45 are spaced apart from one another over a flat tube thickness d.sub.1, d.sub.2. The micro-channels 41 extend in the respective flat tube 35, 39 between the flat tube narrow sides 43 which lie opposite one another, to be precise behind one another in an aligned manner in one row and in a parallel arrangement.

(15) As is apparent from FIG. 3, the inlet chamber 21 is delimited in a fluid-tight manner by a chamber bottom 47, side walls and dividing walls 49, 25 which are raised from it in the evaporator height direction z, and a chamber top wall 51. The first evaporator flat tubes 35 protrude downwards through the chamber top wall 51 into the inlet chamber 21, to be precise in each case with a tube projection 53 (FIG. 2). The bottom-side orifice openings 55 of the micro-channels 41 of the first flat tubes 35 are spaced apart from the chamber bottom 47 over free spacings a (FIG. 3).

(16) In the following text, the construction and the method of operation of the separator 9 will be described using FIG. 3. Accordingly, the orifice openings 55 of the micro-channels 41 of the first flat tube 35 which is shown are configured in a planar, obliquely set flat tube end side 57 which lies completely in an oblique plane. The said oblique plane defines an oblique angle with a horizontal plane. This results in a wedge-shaped separator geometry, in the case of which an inner micro-channel 41 which faces the dividing wall 25 is spaced apart from the chamber bottom 47 at a minimum spacing a.sub.min (FIG. 4), and an outer micro-channel 41 in the evaporator depth direction x is spaced apart from the chamber bottom 47 at a maximum spacing a.sub.max (FIG. 4).

(17) The above-described separator geometry is designed in such a way that, in every operating situation, the filling level f (FIG. 3) of the liquid phase 11 which is collected in the inlet chamber 21 is greater than the minimum spacing a.sub.min. Consequently, during air conditioning operation, the micro-channels 41 of the flat tube 35 are divided into at least one vapour phase micro-channel 41a which is flowed through exclusively by the vapour phase 13, and into at least one liquid phase micro-channel 41b, into which exclusively the liquid phase 11 flows. That filling level f of the liquid phase 11 which is shown in FIG. 3 results by way of example in the seven partially shown vapour phase micro-channels 41a. The latter are positioned above the liquid phase level 65 and therefore form the bypass line 17. In addition, the six partially shown liquid phase micro-channels 41b result in FIG. 3. Exclusively the liquid phase 11 flows into the liquid phase micro-channels 41b. The obliquely positioned flat tube end side 57 therefore dips partially into the liquid phase 11 which is collected in the inlet chamber 21, and partially protrudes beyond the liquid phase level 65 of the liquid phase 11.

(18) In addition, the separator 9 has a distributor tube 59. The distributor tube 59 extends in the inlet chamber 21 in the evaporator transverse direction y and is configured with a reduced cross section in comparison with the inlet chamber 21. The distributor tube 59 has discharge openings 61 which are arranged behind one another on the outer circumference in each case at a spacing and are oriented upwards in the evaporator height direction z, to be precise in the direction of the chamber top wall 51. Via the distributor tube 59, the two-phase liquid/vapour mixture 10 flows into the inlet chamber 21, to be precise via the discharge openings 61. A refrigerant jet 62 (indicated by way of an arrow in FIG. 4) exits in each case from the discharge openings 61. The refrigerant jet 62 comes into contact with the chamber top wall 51 which acts as a deflector wall. A phase separation takes place in the case of the contact of the refrigerant jet 62 with the chamber top wall 51. In order to further assist the said phase separation, the discharge openings 61 are arranged offset by a transverse offset y (FIG. 4) with respect to the first flat tubes 35 as viewed in the evaporator transverse direction y. This ensures that the refrigerant jets 62 which exit come directly into contact with the chamber top wall 51 and are conducted past the orifice openings 55 of the micro-channels 41 of the first flat tubes 35.

(19) In order to further increase the phase separation, each refrigerant jet 62 is assigned a pocket-shaped phase separation space 63 which is open towards the bottom and into which the refrigerant jet 62 is sprayed. The phase separation space 63 is delimited by the mutually facing flat sides 45 of the tube projections 53 of the first flat tubes 35, by the chamber top wall 51 and by the side wall 49 and the dividing wall 25.

(20) In order not to impair the functional capability of the separator 9, the distributor tube 59 is to be positioned in the inlet chamber 21 in such a way that at least its discharge openings 61 protrude beyond the liquid phase level 65, as shown in FIG. 3 or 7. Accordingly, the distributor tube 59 is positioned at least with its discharge openings 61 in an inner corner region. The latter is defined between the liquid phase level 65 and the obliquely set flat tube end side 57.

(21) FIG. 5 shows one of the first flat tubes 35 in cross section. Accordingly, the first flat tube 35 has a total of 20 to 38, for example 29, micro-channels 41, the flat tube width b.sub.1 being 27 mm and the flat tube thickness d.sub.1 lying at 1.28 mm. In contrast to this, FIG. 6 shows one of the second flat tubes 39 in cross section. Accordingly, the number of micro-channels 41 in the second flat tube 39 lies at 10 to 28, for example 19, whereas the flat tube width b.sub.2 lies at 18 mm, and the flat tube thickness d.sub.2 is 1.35 mm.

(22) On account of the highly efficient phase separation which takes place in the separator 9, the flow cross section which is provided by the micro-channels 41 can be reduced substantially in comparison with the prior art. The micro-channel cross section q.sub.1 in the first flat tube 35 thus lies at (0.5 to 0.6 mm, preferably 0.55 to 0.57 mm)(0.6 to 0.8 mm, preferably 0.7 to 0.75 mm), all of the micro-channels 41 in the first flat tube 35 having substantially identical micro-channel cross sections q.sub.1. In the second flat tube 39, the micro-channel cross section q.sub.2 lies at (0.6 to 0.8 mm, preferably 0.7 to 0.75 mm)(0.5 to 0.65 mm, preferably 0.55 to 0.6 mm), all of the micro-channels 41 in the second flat tube 35 having substantially identical micro-channel cross sections q.sub.2.

(23) As is further apparent from FIG. 7, during air conditioning operation, the liquid phase 11 which is collected in the inlet chamber 21 flows into the liquid phase micro-channels 41b. In the further flow path towards the top, the liquid phase 11 which has flowed in can evaporate at least partially into a vapour bubble 68. In a case of this type, there is the risk that the vapour bubble 68 is returned into the inlet chamber 21 counter to the refrigerant flow direction. In order to prevent a vapour return flow of this type into the inlet chamber 21, restricting orifices 67 (FIG. 7) are configured in the region of the orifice openings 55 of the micro-channels 41 of the respective first flat tube 35. The said restricting orifices 67 act as vapour return flow preventers which prevent a return flow of the vapour bubbles 68 which are formed in the liquid phase micro-channels 41b into the inlet chamber 21. Here, the flow cross section at the restricting orifices 67 is reduced by approximately from 50% to 75% in comparison with the remaining micro-channel flow cross section.