EP3792582B1

EP3792582B1 - A method for homogenizing a refrigerant fluid flow within a plate heat exchanger provided with a refrigerant inlet collector with a calibrated orifice

Info

Publication number: EP3792582B1
Application number: EP20194341.2A
Authority: EP
Inventors: Andrea FUCA'
Original assignee: Denso Thermal Systems SpA
Current assignee: Denso Thermal Systems SpA
Priority date: 2019-09-13
Filing date: 2020-09-03
Publication date: 2023-04-19
Anticipated expiration: 2040-09-03
Also published as: IT201900016244A1; ES2947181T3; EP3792582A1

Description

This invention relates in general to plate heat exchangers, of the type comprising two support end plates on which coolant inlet and outlet connectors and water inlet and outlet connectors are arranged, and a stack of thermal exchange plates interposed between the support end plates, between which a plurality of first channels for the passage of a coolant fluid and a plurality of second channels for the passage of water are defined, which alternate with the first channels,
wherein a coolant inlet manifold is formed through the stack of plates which fluidically connects the coolant inlet connector to the first channels, a coolant outlet manifold which fluidically connects the coolant outlet connector to the first channels, a water inlet manifold that fluidically connects the water inlet connector to the second channels, a water outlet manifold that fluidically connects the water outlet connector to the second channels.
In particular, this invention relates to plate exchangers for motor vehicles, such as for example the exchangers used as chillers in air conditioning systems for the indirect cooling of the battery and/or for the indirect cooling in the cabin.
Due to the installation constraints of the expansion device (typically a thermostatic expansion valve) upstream of the chiller, the liquid phase and the gas phase entering the coolant side may flow non-homogeneously and may be separated due to the configuration of the coolant pipes and specific conditions in combination with relatively low coolant flow rates. In the worst case, the coolant may reach the inlet of the exchanger with an annular flow pattern (total separation between the phases).
An uneven distribution leads to a dramatic decrease in the performance of the exchanger due to the irregular presence of liquid coolant between the parallel channels of the exchanger. Solutions are known which have the object of inhibiting the backflow of the liquid phase inside the manifold, by placing calibrated orifices inside the manifold.
An object of this invention is to make available a solution capable of at least partially overcoming the aforementioned drawbacks of the prior art, linked to a non-homogeneous and separate distribution in two phases of the coolant arriving at the inlet of the exchanger. A method for homogenizing a flow of coolant fluid inside a plate heat exchanger according to the preamble of claim 1 is known from US 2016/025420 A1 .
Therefore, the subject matter of the invention is a method for homogenizing a flow of coolant fluid inside a plate exchanger, having the features of claim 1. Upstream of the coolant inlet manifold, between the coolant inlet connector and the coolant inlet manifold, there is a calibrated orifice, which receives a liquid/gas mixture and atomizes it in the inlet manifold.
The calibrated orifice, when the separation between the liquid phase and the gas phase occurs, has the effect of concentrating the entire coolant flow in an area with a reduced section so as to generate a homogeneously mixed spray jet at the outlet of the orifice, wherein the liquid phase is dispersed in the gas phase in the form of droplets. In this way the quality of the coolant flow inside the manifold, as well as the quantity of the liquid fraction in each channel, is more homogeneous. This technical solution introduces a significant pressure loss of the coolant, which is however compensated by the operation of the expansion valve. Preferred embodiments of the invention are defined in the dependent claims, which are to be understood as an integral part of this description.
Further features and advantages of the device according to the invention will become clearer from the following detailed description of an embodiment of the invention, made in reference to the accompanying drawings, provided purely for illustrative and non-limiting purposes, wherein:

Fig. 1 and 2 are respectively a perspective view and a sectional view of a plate exchanger usable in a method according to the invention;
Fig. 3 is a sectional view, taken at the coolant inlet connector, of an exchanger according to the prior art;
Fig. 4 is a sectional view, taken at the coolant inlet connector, of the exchanger in Fig. 1 and 2;
Fig. 5 is a sectional view of part of one of the plates forming the coolant inlet manifold of the heat exchanger;
Fig. 6 is a sectional view which represents a variant of the coolant inlet connector in Fig. 4;
Fig. 7 and 8 are respectively a sectional perspective view and a sectional view of another embodiment of the invention;
Fig. 9 is a plan view of a thermal exchange plate in the embodiment of Fig. 7 and 8;
Fig. 10 and 11 are respectively a sectional view and a plan view of a further embodiment of the invention; and
Fig. 12 and 13 are respectively a sectional view and a plan view of another embodiment of the invention.

Fig. 1 and 2 show a plate heat exchanger, indicated collectively with 1.
The heat exchanger 1 conventionally comprises two support end plates, indicated with 2 and 3, on which inlet and outlet connectors, respectively 4 and 6, for a coolant fluid, as well as inlet and outlet connectors, respectively 5 and 7, for water are arranged. The connectors 4-6 and 5-7 allow the plate heat exchanger 1 to be connected to a hydraulic circuit for the coolant fluid (not shown) and to a hydraulic circuit for water (not shown) respectively.
A stack 10 of thermal exchange plates is interposed between the support end plates 2 and 3 (these plates are represented only in a simplified manner in Fig. 1 and 2). Therefore, conventionally defined between the aforesaid thermal exchange plates is a plurality of first channels (not shown) for the passage of the coolant fluid and a plurality of second channels (not shown) for the passage of water, which alternate with the first channels relative to the stacking direction of the plates. Each of the first channels receives the coolant fluid from the coolant inlet connector 4 through a respective coolant inlet manifold 14 aligned and connected with the coolant inlet connector 4 and formed through the stack of plates 10, and transfers the coolant fluid to the coolant outlet 6 through a respective coolant outlet manifold (not shown) aligned and connected with the coolant outlet connector 6 and formed through the stack of plates 10. Each of the second channels receives water from the water inlet connector 5 through a respective water inlet manifold (not shown) aligned and connected with the water inlet connector 5 and formed through the stack of plates 10, and transfers the water to the water outlet connector 7 through a respective water outlet manifold (not shown) aligned and connected with the water outlet connector 7 and formed through the stack of plates 10.
The support end plates 2, 3 with the connectors 4-7 and the thermal exchange plates are joined together by a brazing process so as to form a single body.
With reference to the applications indicated above, the heat exchanger typically has up to 25 plates, the coolant inlet manifold typically has a diameter between 11 and 17 mm, and the tubing that connects the expansion device to the heat exchanger typically has an inner diameter between 8 and 12 mm.
Reference is now also made to Fig. 4. Upstream of the coolant inlet manifold 14, between the coolant inlet connector 4 and the coolant inlet manifold 14, there is a calibrated orifice 20 configured to receive a liquid/gas mixture at the inlet and to atomize it in the inlet manifold 14. For comparison purposes, Fig. 3 shows the same section as Fig. 4, taken however in a heat exchanger with a coolant inlet manifold without a calibrated orifice at the inlet.
According to the invention, the calibrated orifice 20 has a diameter such that the ratio d/D between the diameter d of the calibrated orifice 20 and the average diameter D of the coolant inlet manifold 14 is between 0.05 and 0.5. As is known, the manifolds of a plate heat exchanger are formed of a plurality of consecutive segments, each of which corresponds to an opening with folded edges formed on a respective thermal exchange plate. By way of reference, Fig. 5 shows one of the thermal exchange plates, indicated with 10A, which form the stack 10 of the heat exchanger. Fig. 5 shows in particular the opening 10a, surrounded by a folded edge 10b, which constitutes one of the consecutive segments that form the inlet manifold 14. The manifold segment formed by the opening 10a is not exactly cylindrical, but rather is slightly conical. The inner diameter of the opening 10a therefore varies from a maximum diameter D1 at a base surface 10c of the plate to a minimum diameter D2 at the free end of the folded edge 10b. In this case, the average inner diameter D of the inlet manifold 14 is therefore given by the average value of the inner diameter of the opening 10a: (D1 + D2)/2. For the sake of thoroughness, Fig. 5 also shows the passages 10d which allow the fluidic connection between the opening 10a (and therefore the inlet manifold 14) and the channels for the coolant fluid formed in the plate 10A, one of which is partially shown in Fig. 5 and indicated with 10e. In the case of coolant inlet manifolds with geometries other than the conical one shown in Fig. 5, the person skilled in the art is easily able to determine how the average inner diameter of the coolant inlet manifold 14 is calculated.
Returning to the example of Fig. 4, it may also be noted that the coolant inlet connector 4 is formed as a block, hereinafter also referred to as the coolant inlet block, which is fixed to the support end plate 3. The calibrated orifice 20 is formed integrally directly inside the coolant inlet block 4. In the example of Fig. 4 it is also noted that a fluid passage 4a having a diameter P greater than the diameter d of the calibrated orifice 20 is formed in the coolant inlet connector or block 4. The fluid passage 4a is intended to interface directly with the tubing of the hydraulic circuit of the coolant fluid when the heat exchanger 1 is connected to said circuit, and is also present in the known configuration shown in Fig. 3.
The lateral surface of the calibrated orifice 20 is connected to the lateral surface of the fluid passage 4a through a connecting surface 4b, which in the example illustrated in Fig. 4 is flat and orthogonal to the longitudinal axis of the calibrated orifice 20 and the fluid passage 4a.
Fig. 6 shows a variant of the embodiment described above, in which the connecting surface 4b is conical, having an angle, for example 120°, with respect to the longitudinal axis of the calibrated orifice 20 and of the fluid passage 4a.
Fig. 7 to 9 show another embodiment of the invention in which the calibrated hole, again indicated with 20, is formed integrally directly with the thermal exchange plate of the stack 10 which is closest to the support end plate 3 on which the coolant inlet connector 4 is arranged. In Fig. 9 this thermal exchange plate, indicated with 10A', is shown in plan. Contrary to the embodiment shown in Fig. 4 and 6, the embodiment of Fig. 7-9 requires a dedicated plate mold for making the plate equipped with the calibrated orifice 20.
Fig. 10 to 13 show a further embodiment, in which the calibrated orifice, again indicated with 20, is made on a separate insert 24 fixed inside the coolant inlet connector or block 4, in a seat formed in the fluid passage 4a. In Fig. 10 and 11, the insert 24 is made of metallic material, for example aluminum, and may be joined to the coolant inlet connector or block 4 with methods known to those skilled in the art, for example by interlocking, or by the same process of brazing which is used to join together the components of the heat exchanger 1. In Fig. 12 and 13 the insert 24 is made of plastics material and may be joined to the coolant inlet connector or block 4 by means of processes known per se, for example interlocking or gluing.

Claims

Method for homogenizing a flow of coolant fluid within a plate heat exchanger, said plate heat exchanger comprising two support end plates (2, 3) on which coolant inlet and outlet connectors (4, 6) and water inlet and outlet connectors (5, 7) are arranged, and a stack (10) of thermal exchange plates interposed between the support end plates (2, 3), among which thermal exchange plates there is defined a plurality of first channels for the passage of a coolant fluid and a plurality of second channels for the passage of water, the second channels alternating with the first channels,
wherein through the stack (10) of thermal exchange plates there are formed a coolant inlet manifold (14) fluidically connecting the coolant inlet connector (4) to the first channels, a coolant outlet manifold fluidically connecting the coolant outlet connector (6) to the first channels, a water inlet manifold fluidically connecting the water inlet connector (5) to the second channels, a water outlet manifold (7) fluidically connecting the water outlet connector to the second channels,

wherein the coolant fluid is supplied to the coolant inlet connector (4) in form of a liquid/gas mixture,

said method being characterized in that upstream of the coolant inlet manifold (14), between the coolant inlet connector (4) and the coolant inlet manifold (14), there is a calibrated orifice (20) that receives said liquid/gas mixture and atomizes it in the coolant inlet manifold (14),

wherein the calibrated orifice (20) has a diameter d such that ratio d/D between the diameter d of the calibrated orifice (20) and the average diameter D of the coolant inlet manifold (14) ranges between 0.05 and 0.5, and

wherein the calibrated orifice (20) concentrates the entire flow of coolant fluid in an area with a reduced section so as to generate a homogenously mixed spray jet at the outlet of the calibrated orifice, wherein in the spray jet the liquid phase is dispersed in the gaseous phase in droplet form.
Method according to claim 1, wherein the coolant inlet connector (4) is formed as a block fixed to one of the support end plates (2, 3), and wherein the calibrated orifice (20) is formed integrally directly within said block.
Method according to claim 2, wherein in said block there is formed a fluid passage (4a) having a diameter (P) greater than the calibrated orifice (20), and wherein a lateral surface of the calibrated orifice (20) is connected to a lateral surface of the fluid passage (4a) through a flat or conical connecting surface (4b).
Method according to claim 1, wherein the calibrated orifice (20) is formed integrally directly in the thermal exchange plate (10A') closest to the support end plate (3) on which the coolant inlet connector (4) is arranged.
Method according to claim 1, wherein the coolant inlet connector (4) is formed as a block fixed to one of the support end plates (2, 3), and wherein the calibrated orifice (20) is formed on an insert (24) fixed within said block.