EP2650633A2

EP2650633A2 - Plate-type heat exchanger, method of manufacturing the same, and heat pump device

Info

Publication number: EP2650633A2
Application number: EP13160236.9A
Authority: EP
Inventors: Shinichi Uchino
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 2012-04-12
Filing date: 2013-03-20
Publication date: 2013-10-16
Anticipated expiration: 2033-03-20
Also published as: JP2013221629A; EP2650633A3; CN203405106U; CN103376004B; EP2650633B1; JP5881515B2; CN103376004A

Abstract

To guide lubricating oil flowing into a plate-type heat exchanger to an oil-recovery port, while minimizing the amount of lubricating oil trapped therein.

A plate-type heat exchanger includes: a plate assembly 120 that is a plate stacked body including a stack of a plurality of heat-transfer plates 100; an inlet port and an outlet port for refrigerant 7 provided in the plate assembly 120; an inlet port and an outlet port for water 10 provided in the plate assembly 120; and an oil-recovery port 103e from which lubricating oil 8 contained in the refrigerant 7 is extracted, the oil-recovery port 103e being provided below the outlet port for the refrigerant 7 provided in the lower part of the plate assembly 120. Oil recovery holes 200 communicating with the oil-recovery port 103e are provided at the lower part inside the plate assembly 120, and a flow-smoothing embossed portion 201 is provided on each heat-transfer plate 100 so that the lubricating oil 8 smoothly flows toward the oil recovery hole 200.

Description

[Technical Field]

The present invention relates to a plate-type heat exchanger that performs heat exchange between refrigerant and fluid to be heated, a method of manufacturing the same, and a heat pump device.

[Background Art]

A type of plate-type heat exchanger that has flow paths formed by stacking a plurality of plates and brazing them together to perform heat exchange between two flow path systems are commonly known. Furthermore, heat pump systems that use a plate-type heat exchanger as a condenser of the heat pump system to perform heat exchange between refrigerant discharged from a compressor and circulation water flowing into the plate-type heat exchangers and supply hot water are known.
Lubricating oil for reducing frictional heat is used in the compressor employed in the heat pump system so that a rotation mechanism is not damaged by the heat of the compressor. The lubricating oil is discharged due to the flow of refrigerant discharged from the compressor and circulates in a refrigerant circuit together with the refrigerant. Although most of the lubricating oil returns to the compressor from a suction pipe of the compressor after circulation, a portion of the lubricating oil is trapped in refrigerant circuit components, such as a condenser, a pressure vessel that stores excess refrigerant, and an evaporator.
A plate-type heat exchanger is formed by stacking a plurality of heat-transfer plates each having corrugated embossed portions to increase a heat-transfer area. Furthermore, because the plate-type heat exchanger is the first refrigerant circuit component that the refrigerant discharged from the heat pump system reaches, the lubricating oil tends to be trapped in the plate-type heat exchanger.
Hence, Patent Literatures 1 and 2 disclose plate-type heat exchangers having a port through which lubricating oil is returned to a compressor, as examples of the technique to recover trapped lubricating oil.

[Citation List]

[Patent Literature]

[Patent Literature 1] Japanese Unexamined Patent Application Publication No. 2011-247579
[Patent Literature 2] Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2005-527777

[Summary of Invention]

[Technical Problem]

If the total amount of lubricating oil in a compressor decreases due to the lubricating oil being trapped in a plate-type heat exchanger, failure due to burning out of the compressor occurs. If the amount of lubricating oil is increased taking into consideration trapping of the lubricating oil, the lubricating oil is deposited on walls of the condenser and the evaporator, leading to deterioration in the heat exchange performance. In order to ensure the satisfactory heat exchange performance and the reliability of the compressor with the minimum amount of lubricating oil, it is important to efficiently return the lubricating oil from the plate-type heat exchanger.
The plate-type heat exchanger has, due to the structure thereof, a dead space, which is not used for heat exchange but is needed to maintain a container shape, below nozzles that serve as a refrigerant inlet port and a refrigerant outlet port.
As shown in Patent Literatures 1 and 2, because such a dead space also exists in the plate-type heat exchangers having the lubricating oil recovery port, once the lubricating oil flowing into the plate-type heat exchanger enters the dead space, the lubricating oil cannot be thoroughly recovered, resulting in a problem in that intended functions cannot be fully achieved.
The present invention has been made to solve the above-described problem, and an object thereof is to guide lubricating oil flowing into a plate-type heat exchanger to an oil-recovery port, while minimizing the amount of lubricating oil trapped therein.

[Solution to Problem]

A plate-type heat exchanger includes a plate assembly that is a plate stacked body including a stack of a plurality of heat-transfer plates; a first-fluid inlet port and a first-fluid outlet port provided in the plate assembly; a second-fluid inlet port and a second-fluid outlet port provided in the plate assembly; and an oil-recovery port from which oil contained in the first fluid is extracted, the oil-recovery port being provided below the first-fluid outlet port provided in a lower part of the plate assembly. Oil recovery holes communicating with the oil-recovery port are provided at a lower part inside the plate assembly. An embossed portion is formed on each heat-transfer plate so that the oil smoothly flows toward the oil recovery hole.
A method of manufacturing the plate-type heat exchanger of the present invention is a method of manufacturing the plate-type heat exchanger of the present invention including, at least, a step of forming oil recovery holes in the lower part of the heat-transfer plates; a step of forming L-shaped embossed portions along lower peripheral portions of the heat-transfer plates; and a step of brazing contact portions after the embossed portions are embossed to an intermediate point of a flow clearance between the heat-transfer plates, and the embossed portions are brought into contact with the embossed portions of the adjacent heat-transfer plates.
A heat pump device of the present invention is a heat pump device having a refrigeration cycle in which a compressor, a condenser, an expansion valve, and an evaporator are connected in a circle by pipes. The plate-type heat exchanger of the present invention is used as the condenser or the evaporator. The oil recovery holes provided in the plate-type heat exchanger are connected to a suction port of the compressor by a pipe.

[Advantageous Effects of Invention]

In the plate-type heat exchanger of the present invention, because the oil recovery holes communicating with the oil-recovery port are provided at the lower part inside the plate assembly, and because the embossed portion is formed on each heat-transfer plate so that the oil smoothly flows toward the oil recovery hole, the amount of oil trapped in the dead space in the plate-type heat exchanger can be minimized. Accordingly, it is possible to guide the lubricating oil flowing into the plate-type heat exchanger to the oil-recovery port, while minimizing the amount of the lubricating oil trapped therein.
The method of manufacturing the plate-type heat exchanger of the present invention includes, at least, a step of forming oil recovery holes in the lower part of the heat-transfer plates; a step of forming L-shaped embossed portions along lower peripheral portions of the heat-transfer plates; and a step of brazing contact portions after the embossed portions are embossed to an intermediate point of a flow clearance between the heat-transfer plates, and the embossed portions are brought into contact with the embossed portions of the adjacent heat-transfer plates. Thus, a plate-type heat exchanger having the above-described advantages can be obtained.
Because the heat pump device of the present invention uses the plate-type heat exchanger of the present invention as the condenser or the evaporator of the refrigeration cycle, and because the oil recovery holes provided in the plate-type heat exchanger are connected to the suction port of the compressor with a pipe, it is possible to suppress a decrease in the amount of the lubricating oil in the compressor, and hence, to realize a highly reliable heat pump device that does not frequently suffer from failure of compressor.

[Brief Description of Drawings]

[FIG. 1] FIG. 1 is a diagram showing the configuration of a heat pump device 2 according to Embodiment 1 of the present invention.
[FIG. 2] FIG. 2 is an external view of a plate-type heat exchanger 1 according to Embodiment 1.
[FIG. 3] FIG. 3 is an exploded perspective view of the plate-type heat exchanger 1.
[FIG. 4] FIG. 4 is an external view showing the configuration of an oil-recovery portion of a heat-transfer plate 100.
[FIG. 5] FIG. 5 includes a front view of a plate-type heat exchanger of the related art and a cross-sectional view of an oil-recovery port 103e thereof.
[FIG. 6] FIG. 6 includes a front view of the plate-type heat exchanger 1 according to Embodiment 1 and a cross-sectional view of an oil-recovery port 103e thereof.
[FIG. 7] FIG. 7 is a side view of the plate-type heat exchanger 1.
[FIG. 8] FIG. 8 is a front view of the plate-type heat exchanger 1 (as viewed in a direction indicated by arrow A in FIG. 7).
[FIG. 9] FIG. 9 is a back view of the plate-type heat exchanger 1 (as viewed in a direction indicated by arrow B in FIG. 7).
[FIG. 10] FIG. 10 is a cross-sectional view (cross-sectional view taken along line Z-Z in FIG. 8) of the plate-type heat exchanger 1.
[FIG. 11] FIG. 11 includes conceptual diagrams of the heat-transfer plate 100.
[FIG. 12] FIG. 12 includes conceptual diagrams of side plates 105.
[FIG. 13] FIG. 13 is an enlarged view of portion D in FIG. 10.

[Description of Embodiments]

First, the schematic configuration of a heat pump device 2 having a plate-type heat exchanger 1 of the present invention will be described with reference to FIG. 1.
FIG. 1 is a diagram showing the configuration of the heat pump device 2 according to Embodiment 1 of the present invention. Furthermore, flows of refrigerant 7, lubricating oil 8, heating water 10, and clean water 11 are indicated by different arrows in FIG. 1.
The heat pump device (heat pump unit) 2 illustrated in FIG. 1 includes a compressor 3, a condenser 4 (first heat exchanger), an electric expansion valve 5, and an evaporator 6 (second heat exchanger), which are sequentially connected by a pipe 15, forming a refrigeration cycle in which the refrigerant 7 circulates. Furthermore, although FIG. 1 illustrates an example in which the plate-type heat exchanger 1 is used as the condenser 4 (first heat exchanger), the present invention is not limited thereto. The separated lubricating oil 8 flowing out of the plate-type heat exchanger 1, serving as the condenser 4 (first heat exchanger), returns to the compressor 3 through an oil pipe 16. The oil pipe 16 connects between an oil-recovery port, described below, provided in the plate-type heat exchanger 1 and a suction port of the compressor 3.
The compressor 3 is, for example, an inverter scroll compressor and compresses the refrigerant 7 (first fluid) to increase the enthalpy and pressure of the refrigerant 7. The condenser 4 performs heat exchange between the compressed refrigerant 7 (first fluid) and fluid to be heated (second fluid). The electric expansion valve 5 adiabatically expands the refrigerant 7 flowing out of the condenser 4. The evaporator 6 performs heat exchange between the refrigerant 7 flowing out of the electric expansion valve 5 and an external heat source.
Although not illustrated, the heat pump device 2 may further include other peripheral components, such as a receiver for storing excess refrigerant 7.
In FIG. 1, the plate-type heat exchanger 1 is used as, for example, the condenser 4. With this configuration, water, which is the second fluid flowing into the plate-type heat exchanger 1, can be heated by rejecting heat from the external heat source (heat received by the evaporator 6) from the plate-type heat exchanger 1. There are other media usable as the external heat source (i.e., media to exchange heat with the evaporator 6), such as air and ground heat, and the plate-type heat exchanger 1 may be used in any hot-water-supply heat pump unit that uses an external heat source. Furthermore, the plate-type heat exchanger 1 may be used not only as the condenser 4 (first heat exchanger), but also as the evaporator 6 (second heat exchanger).
Furthermore, the plate-type heat exchanger 1 is connected to the highpressure side of the compressor 3. Thus, the lubricating oil 8 flowing in the plate-type heat exchanger 1 with refrigerant 7 and trapped at the bottom of the plate-type heat exchanger 1 is discharged from the plate-type heat exchanger 1 due to a suction force of the compressor 3 and is recovered in the compressor 3 through the oil pipe 16.
The lubricating oil 8 is present in the compressor 3, helps driving components (bearings, sliding components, etc.) of the compressor 3 radiate heat, and maintains lubricity to prevent failure of the compressor 3. While the lubricating oil 8 is discharged from the compressor 3, together with the refrigerant 7 discharged from the compressor 3, and circulates in the refrigeration cycle, a portion of the lubricating oil 8 may be trapped in the condenser 4, the evaporator 6, or another peripheral component. As a result, the lubricating oil 8 decreases, resulting in failure of the compressor 3 due to burning out of the driving components of the compressor 3.
A water circuit 9 is connected to the plate-type heat exchanger 1, serving as the condenser 4. The heating water 10 (or sometimes "water 10") circulates in the water circuit 9. Note that FIG. 1 illustrates an indirect heating system for heating the water 10 by the plate-type heat exchanger 1. More specifically, the water 10 flows into the plate-type heat exchanger 1, serving as the condenser 4, is heated by the refrigerant 7, and flows out of the plate-type heat exchanger 1 as hot water. The heating water 10 flowing out of the plate-type heat exchanger 1 in this manner flows into a heating appliance 13, such as a radiator or a floor heating device, connected by a pipe constituting the water circuit 9 and is used to control the indoor temperature. Furthermore, by arranging a water-water heat exchange tank 12 that performs heat exchange between the heating water 10 and the clean water 11 at an intermediate point in the water circuit 9, the clean water 11 heated in the water circuit 9 can be utilized as water for household use, which is consumed by a device 14 requiring clean water, such as a bath or a shower.
Note that the water circuit 9 having one or both of a hot-water-supply device and a heating appliance may be connected to this plate-type heat exchanger 1.
Using FIGS. 2 to 13, the configuration of the plate-type heat exchanger 1 according to Embodiment 1 will be described below.
FIG. 2 is an external view of the plate-type heat exchanger 1 according to Embodiment 1, and FIG. 3 is an exploded perspective view of the plate-type heat exchanger 1.
The plate-type heat exchanger 1 according to Embodiment 1 is a heat exchanger of a type in which a plurality of heat-transfer plates 100 (100a and 100b) are stacked, side plates 105 and reinforcing plates (pressure-resistant plates) 104 are provided on both sides of the heat-transfer plates 100 on the extreme outer sides, and the plates 100, 105, and 104 are brazed together. Hereinbelow, a stacked body composed of the plates 100, 105, and 104 is referred to as a plate assembly 120.
A refrigerant inlet port 1 03a and a refrigerant outlet port 1 03b for the refrigerant 7, serving as the first fluid, and a water inlet port 103c and a water outlet port 103d for, for example, the water 10, serving as the second fluid, are provided at four corners, in the longitudinal direction, of a reinforcing plate 104a positioned at an end of the plate assembly 120. The configuration of the plate assembly 120 is shown in FIGS. 7 to 13.
As illustrated in FIG. 3, the heat-transfer plates 100a and the heat-transfer plates 100b are arranged next to one another. The heat-transfer plates 100a and 100b have corrugated heat-transfer surfaces. The heat-transfer plates 100a and the heat-transfer plates 100b are arranged at predetermined intervals so as to form flow clearances therebetween.
As indicated by arrows in FIG. 3, the refrigerant 7 flows from the refrigerant inlet port 103a, flows through each clearance between the adjacent heat-transfer plate 100b and heat-transfer plate 100a from holes communicating with the refrigerant inlet port 103a, and flows downward between the heat-transfer surfaces thereof. On the other hand, the water 10 flows from the water inlet port 103c, flows through each clearance between adjacent heat-transfer plates 100a and 100b from holes communicating with the water inlet port 103c, and flows upward between the heat-transfer surfaces thereof. By alternately providing the downward flow of the refrigerant 7 and the upward flow of the water 10 between the heat-transfer plates 100a and 100b, heat is efficiently transferred from the hot heat-transfer plates 100a at a high temperature to the heat-transfer plates 100b at a low temperature, and due to this heat transfer, the water 10 is heated to a high temperature. Note that, although it has been described that the refrigerant 7 and the water 10 flow in opposite directions, by providing the inlet port and the outlet port for the water 10 on the opposite side to those in FIG. 2, the refrigerant 7 and the water 10 may be configured to flow in parallel.
In addition, as illustrated in FIG. 2, in this plate-type heat exchanger 1, an oil-recovery port 103e, from which the lubricating oil 8 contained in the refrigerant 7 is extracted, is provided near the refrigerant outlet port 103b, below the refrigerant outlet port 103b.
Next, FIGS. 7 to 9 will be described before the description of FIG. 4.
FIG. 7 is a side view of the plate-type heat exchanger 1, FIG. 8 is a front view of the plate-type heat exchanger 1 (as viewed in the direction indicated by arrow A in FIG. 7), and FIG. 9 is a back view of the plate-type heat exchanger 1 (as viewed in the direction indicated by arrow B in FIG. 7).
As illustrated in FIG. 7, in the plate-type heat exchanger 1, the reinforcing plate 104a, to which nozzles 103 including the refrigerant inlet port 103a, the refrigerant outlet port 103b, the water inlet port 103c, and the water outlet port 103d (hereinbelow, these refrigerant inlet/outlet ports and water inlet/outlet ports are collectively referred to as the "nozzles 103") are attached; the side plate 105a; the heat-transfer plate 100a; the heat-transfer plate 100b ... the heat-transfer plate 100a; the heat-transfer plate 100b; the side plate 1 05b; and the reinforcing plate 1 04b are stacked in sequence and brazed together. Herein, the reinforcing plate 104b is not illustrated in FIG. 7 because it is covered by the side plate 105b.
The front view in FIG. 8 (as viewed in the direction indicated by arrow A in FIG. 7) illustrates four nozzles 103 (103a to 103d) and the oil-recovery port 103e attached to the reinforcing plate 104a.
The back view in FIG. 9 (as viewed in the direction indicated by arrow B in FIG. 7) illustrates a surface of the reinforcing plate 104b provided on the opposite side from the reinforcing plate 104a.
As illustrated in FIG. 2, when used, the plate-type heat exchanger 1 is installed such that the nozzles 103a and 103d are positioned on the upper side, and the nozzles 103b, 103d, and the oil-recovery port 103e are positioned on the lower side.
Referring back to FIG. 4, an additional description will be given. FIG. 4 is an external view showing the configuration of the oil-recovery portion of the heat-transfer plate 100.
As illustrated in FIG. 4, in this plate-type heat exchanger 1 according to Embodiment 1, an oil recovery hole 200 communicating with the oil-recovery port 103e is provided in the lower part of each heat-transfer plate 100. The oil recovery hole 200 is formed in the shape of a raindrop (i.e., an ellipse with a small arch portion at one end, the small arch portion having a smaller radius than the other end), and a bottom end 200a of the small arch portion is located near a lower peripheral portion of the oil-recovery port 103e.
Furthermore, an L-shaped embossed portion 201 is formed along a lower peripheral portion of each heat-transfer plate 100. This embossed portion 201 extends toward the bottom end 200a of the small arch portion of the oil recovery hole 200, and a substantially horizontal portion 201a thereof is inclined such that the lubricating oil 8 separated from the refrigerant 7 smoothly flows along the L-shaped embossed portion 201. Hereinbelow, this embossed portion 201 is referred to as a flow-smoothing embossed portion 201. That is, the flow-smoothing embossed portion 201 is formed such that the lubricating oil 8 smoothly flows toward the bottom end 200a of the small arch portion of the oil recovery hole 200. Furthermore, the bottom end 200a of the small arch portion of the oil recovery hole 200 is formed near the substantially horizontal portion 201a of the L-shaped flow-smoothing embossed portion 201.
With this configuration, the lubricating oil 8 smoothly flows from the substantially horizontal portion 201a of the flow-smoothing embossed portion 201 to the bottom end 200a of the small arch portion of the oil recovery hole 200 and then flows out of the oil-recovery port 103e.
FIGS. 5 and 6 are shown to compare the advantages of the oil-recovery portion of the plate-type heat exchanger of the related art and the advantages of the oil-recovery portion of the plate-type heat exchanger 1 according to Embodiment 1. FIG. 5 includes a front view of the plate-type heat exchanger of the related art and a cross-sectional view of an oil-recovery port 103e thereof, and FIG. 6 includes a front view of the plate-type heat exchanger 1 according to Embodiment 1 and a cross-sectional view of an oil-recovery port 103e thereof.
As can be seen from FIGS. 5 and 6, the refrigerant 7 containing the lubricating oil 8 flows down through each flow clearance between the adjacent heat-transfer plate 100a and the heat-transfer plate 100b having the corrugated heat-transfer surfaces. At this time, because the lubricating oil 8 has a higher density than the refrigerant 7, the refrigerant 7 goes up and the lubricating oil 8 goes down after separation due to the difference in density. In the plate-type heat exchanger of the related art illustrated in FIG. 5, because there is a dead space 202 below the oil recovery holes 200 (a space encircled by a dashed line in FIG. 5), a portion of the lubricating oil 8 fallen into the oil recovery holes 200 provided in the lower part of the heat-transfer plates 100, the portion that is not recovered, stays in the dead space 202.
On the other hand, in the case of Embodiment 1, as illustrated in FIG. 6, a block wall 203 (a portion having a closed top, encircled by a dashed line in FIG. 6) is provided immediately below the oil recovery holes 200. This block wall 203 is formed by bringing the flow-smoothing embossed portions 201 of the adjacent heat-transfer plates 100 into contact with one another and brazing the contact portions together. Thus, the top of the dead space 202 is closed by the block wall 203. In other words, the block wall 203 separates the dead space 202 from the other part. Hence, the lubricating oil 8 flows out of the oil-recovery port 103e without entering the dead space 202.
Accordingly, with Embodiment 1, because the block wall 203 is provided immediately below the flow-path holes (oil recovery holes) 200 communicating with the oil-recovery port 103e, the dead space 202 can be separated from the other part by the block wall 203. Thus, it is possible to prevent the lubricating oil 8 from being trapped in the dead space 202. In other words, it is possible to minimize the amount of the lubricating oil 8 trapped in the dad space 202.
Furthermore, due to the flow-smoothing embossed portions 201 and the block wall 203, the lubricating oil 8 flowing into the plate-type heat exchanger 1 is guided to the oil-recovery port 103e with the flow. Thus, efficient oil recovery becomes possible.
Note that, in FIGS. 5 and 6, the water 10 flows up through the flow paths next to the flow paths for the refrigerant 7, in which the lower ends of the corrugated heat-transfer surfaces are closed.
Next, using FIGS. 4, 6, and 10 to 13, a method of manufacturing the plate-type heat exchanger 1 according to Embodiment 1 will be described.
FIG. 10 is a cross-sectional view of the plate-type heat exchanger 1 corresponding to a cross-sectional view taken along line Z-Z in FIG. 8. Herein, the phrase "corresponding to" is used for the following reason. FIG. 10 illustrates only four, in total, heat-transfer plates 100a and 100b, for the ease of description. Because FIG. 8 is not the same as FIG. 10 for the above reason, the phrase "corresponds to" is used.
FIG. 11 includes conceptual diagrams of the heat-transfer plate 100, in which FIGS. 11(a) and 11(b) illustrate the heat-transfer plate 100a and heat-transfer plate 100b, respectively, when the heat-transfer plates 100 of the plate-type heat exchanger 1 in FIG. 10 are viewed from a direction indicated by arrow C. As illustrated in FIG. 10, the heat-transfer plate 100b is disposed below the side plate 105a, and the heat-transfer plate 100a is disposed below the heat-transfer plate 100b. In a stacked state, flow-path holes 106a to 106d (second holes) provided in the heat-transfer plate 100b overlap flow-path holes 106a to 106d (third holes) provided in the heat-transfer plate 100a, forming flow paths.
The main structure of the plate-type heat exchanger 1 according to Embodiment 1 is such that the heat-transfer plates 100a having a corrugated heat-transfer portion 107a and the heat-transfer plates 100b having a corrugated heat-transfer portion 107b, as illustrated in FIG. 11, are stacked, forming flow paths in which the first fluid and the second fluid exchange heat. A lateral plate assembly 120 illustrated in FIG. 10 is configured such that the side plate 105a is disposed above the heat-transfer stacked body 108 composed of the heat-transfer plates 100, the side plate 105b is disposed below the heat-transfer stacked body 108, the reinforcing plate 104a is disposed above the side plate 105a, and the reinforcing plate 104b is disposed at the bottom, forming a shape in which the stacked body 108 composed of the heat-transfer plates 100 is sandwiched.

Heat-Transfer Plates 100a and Heat-Transfer Plates 100b

The heat-transfer plate 100a and the heat-transfer plate 100b illustrated in FIG. 11 have the same size and thickness. The heat-transfer plate 100a and the heat-transfer plate 100b have the flow-path holes 106a to 106d at the four corners thereof. The corrugated heat-transfer portions 107a and 107b for stirring fluid are provided between the flow-path holes 106a and 106b and the flow-path holes 106c and 106d in the longitudinal direction. The heat-transfer portion 1 07a of the heat-transfer plate 100a and the heat-transfer portion 107b of the heat-transfer plate 100b have shapes that are inverted by 180 degrees with respect to each other. That is, the heat-transfer portion 107b has such a shape that the heat-transfer portion 107a is rotated by 180 degrees about point P, in a direction indicated by an arrow.

Formation of Flow Path by Heat-Transfer Plates 100

When the heat-transfer plate 100a and the heat-transfer plate 100b are stacked, the corrugated portion of the heat-transfer portion 1 07a and the corrugated portion of the heat-transfer portion 107b make point contact with each other. When these point-contact portions are brazed, "posts" forming flow paths are formed. For example, the heat-transfer plates 100a form flow paths for water (pure water, tap water, or water containing antifreeze), and the heat-transfer plates 100b form flow paths for the refrigerant 7 (for example, refrigerant, such as R410A, used in air-conditioning apparatuses). By stacking one heat-transfer plate 100b and one heat-transfer plate 100a, a water flow path is formed, and by stacking another heat-transfer plate 100a, a "water-refrigerant" layer is formed. By increasing the number of heat-transfer plates stacked in the same way, the flow paths are alternately formed (i.e., water, refrigerant, water, refrigerant ... (see FIG. 3)). The heat-transfer stacked body 108, as shown in FIG. 10, is formed of the plurality of stacked heat-transfer plates.

Formation of Oil Recovery Hole 200

As illustrated in FIG. 4, the oil recovery hole 200 in the shape of an ellipse with a small arch portion at one end, the small arch portion having a smaller radius than the other end, is provided at the lower part of each heat-transfer plate 100. Furthermore, the peripheral portion of the oil recovery hole 200 is embossed to an intermediate point of the flow clearance between the heat-transfer plates 100, and the embossed portion is brought into contact with the embossed portion around the oil recovery hole 200 in the adjacent heat-transfer plate 100.

Formation of Flow-Smoothing Embossed Portion 201

The L-shaped embossed portions (flow-smoothing embossed portions) 201 are formed along the lower peripheral portions of the heat-transfer plates 100. Similarly to the embossed portions around the oil recovery holes 200, the flow-smoothing embossed portions 201 are formed by embossing the relevant portions to an intermediate point of the flow clearance between the heat-transfer plates 100. The horizontal portions of the flow-smoothing embossed portions 201 are slightly inclined such that the lubricating oil 8 smoothly flows toward the bottom ends 200a of the small arch portions of the oil recovery holes 200, as illustrated in FIG. 4. Thus, the lubricating oil 8 flowing from the upper side, as indicated by arrows in FIG. 4, flows along the flow-smoothing embossed portions 201, reaches the bottom ends 200a of the small arch portions of the oil recovery holes 200, and then smoothly flows into the oil recovery holes 200 from there.

Formation of Block Wall 203

When the heat-transfer plates 100 are stacked, the flow-smoothing embossed portions 201 formed on the heat-transfer plates 100 come into contact with the flow-smoothing embossed portions 201 of the heat-transfer plates 100 in front and rear thereof. Then, the flow-smoothing embossed portions 201 are brazed together to form the block wall 203 that separates the dead space 202 from the other part below the oil-recovery port 103e, as illustrated in FIG. 6. Thus, the amount of lubricating oil 8 trapped is minimized, and efficient oil recovery becomes possible.

Side Plate 105

FIG. 12 includes conceptual diagrams of the side plates 105. As previously illustrated in FIG. 10, the side plate 105a and the side plate 105b provided above and below the heat-transfer stacked body 108 are flat plates that have no corrugated heat-transfer portions 107, have the same thickness as the heat-transfer plates 100, and have the flow-path holes 106a to 106d at the four corners thereof. Furthermore, as illustrated in FIG. 3, the side plate 105a is disposed above (on one extreme outer side of) the heat-transfer stacked body 108, and the side plate 105b is disposed below (on the other extreme outer side of) the heat-transfer stacked body 108, forming a stacked body composed of the heat-transfer plates 100.
Furthermore, as illustrated in FIGS. 10 and 12, circular embossed portions 110a are provided around the flow-path holes 106a and 106b in the side plates 105a and 105b, and the embossed portions 110a are in contact with the flow-path holes 106a and 106b in the adjacent heat-transfer plates 100a and 100b.

Embossed Portion 110a

As illustrated in FIGS. 10 and 12, the side plate 105a has the concave embossed portions 110a provided around the flow-path holes 106a and 106b by embossing, and the side plate 105b has a convex embossed portion 110b provided around the flow-path hole 106a by embossing and a convex embossed portion 110c provided around the flow-path hole 106b by embossing. These are brazed to the flow-path holes 106a and 106b in the heat-transfer plates 100a and 100b, forming posts around the flow-path holes in the heat-transfer plates 100 and the side plates 105, thereby making it possible to increase the strength.
FIG. 13 is an enlarged view of portion D in FIG. 10.
As illustrated in FIG. 13, the concave and convex embossed portions 110 prevent the refrigerant from flowing into non-heat-transfer spaces 111 formed by the side plate 105a and the side plate 105b. The non-heat-transfer spaces 111 are spaces that are formed between the flat surfaces and the corrugated heat-transfer portions 107b and have no utility in the heat transfer. Accordingly, by preventing the refrigerant from flowing into the non-heat-transfer spaces 111, unwanted heat rejection and a decrease in flow rate of the refrigerant can be prevented.

Reinforcing Plate 104

As illustrated in FIG. 10, the reinforcing plate 104a (an outer plate) is attached above the heat-transfer stacked body 108, and the reinforcing plate 104b is attached below the heat-transfer stacked body 108. The reinforcing plate (i.e., pressure-resistant plate) 104 is about five times as thick as the heat-transfer plates 100 and the side plates 105. As illustrated in FIG. 8, in the plate-type heat exchanger 1, the reinforcing plate 104a has five flow-path holes (nozzles 103). As illustrated in FIG. 9, the reinforcing plate 104b has no flow-path holes. Because of the pressure-resistant plates 104a and 104b, the plate-type heat exchanger 1 can resist fatigue caused by pressure variations due to the fluid flowing in the heat-transfer stacked body 108 and a force generated by the difference between the pressure of the plate-type heat exchanger 1 and the atmospheric pressure.

Crimping of Nozzles

The nozzles 103a to 103d, from which the refrigerant and the water are introduced into the heat-transfer stacked body 108, and the oil-recovery port 103e, from which the lubricating oil 8 is discharged, are attached to the corresponding five flow-path holes in the pressure-resistant plate 104a. The attaching positions (attaching portions) of the nozzles 103 are determined according to the number of the flow-path holes in the reinforcing plates 104a and 104b. When four (i.e., maximum) flow-path holes are provided in one reinforcing plate, eight nozzles 103, in total, are attached to one plate-type heat exchanger 1.
As illustrated in FIG. 13, attachment of the nozzle will be described using the nozzle 103a.
The nozzle 103a has a press-insertion portion 112 at an end that fits into the corresponding flow-path hole in the reinforcing plate 104a. The press-insertion portion 112 is configured such that an end thereof protrudes from the bottom surface of the reinforcing plate 104a by, at least, 1 mm. Before a step of brazing the plate-type heat exchanger 1, the press-insertion portion 112 of the nozzle 103a is inserted into the corresponding flow-path hole in the pressure-resistant plate 104a, and the press-insertion portion 112 is crimped. The nozzles 103b to 103d and the oil-recovery port 103e are crimped in the same way. The reinforcing plate 104a, to which the nozzles 103 and the oil-recovery port 103e are temporarily fixed by crimping, is disposed on the heat-transfer stacked body 108 with the side plate 105a therebetween. Thus, the overall plate-type heat exchanger 1 is temporarily assembled, and the temporarily assembled plate-type heat exchanger 1 is sent to a brazing step.

Welding Step

In the temporarily assembled plate-type heat exchanger 1, copper strips, serving as brazing alloy, are disposed between the heat-transfer plate 100a and the heat-transfer plate 100b, the heat-transfer stacked body 108 and the side plates 106a and 106b, the side plate 106a and the reinforcing plate 104a, and the side plate 106b and the reinforcing plate 104b. Furthermore, copper, serving as brazing alloy, is disposed between the reinforcing plate 104a and the nozzles 103. The temporarily assembled plate-type heat exchanger 1 provided with brazing alloy is put into a vacuum heating furnace and brazed under vacuum in the brazing step. In this brazing step, copper melts and permeates into joint surfaces of the components. When the copper permeated into the components cools down, the components are semipermanently bonded together, and thus, the plate-type heat exchanger 1 is formed.

[Reference Signs List]

1 plate-type heat exchanger, 2 heat pump device (heat pump unit), 3 compressor, 4 condenser, 5 electric expansion valve, 6 evaporator, 7 refrigerant, 8 lubricating oil, 9 water circuit, 10 heating water, 11 clean water, 12 water-water heat exchange tank, 13 heating appliance, 14 clean water use device, 15 pipe, 16 oil pipe, 100 heat-transfer plate, 103 nozzle, 1 03a refrigerant inlet port, 1 03b refrigerant outlet port, 103c water inlet port, 103d water outlet port, 103e oil-recovery port, 104 reinforcing plate (pressure-resistant plate), 105 side plate, 106 flow-path hole, 107 heat-transfer portion, 108 heat-transfer stacked body, 110 embossed portion, 111 non-heat-transfer space, 112 press-insertion portion, 120 plate assembly, 200 oil recovery hole, 200a bottom end, 201 smoothing embossed portion, 201a substantially horizontal portion, 202 dead space, and 203 block wall.

Claims

1.
A plate-type heat exchanger (1) comprising:

a plate assembly (120) that is a plate stacked body including a stack of a plurality of heat-transfer plates (100);

a first-fluid inlet port and a first-fluid outlet port provided in the plate assembly (120);

a second-fluid inlet port and a second-fluid outlet port provided in the plate assembly (120); and

an oil-recovery port from which oil contained in the first fluid is extracted, the oil-recovery port being provided below the first-fluid outlet port provided in a lower part of the plate assembly (120),

wherein oil recovery holes (200) communicating with the oil-recovery port are provided at a lower part inside the plate assembly (120), and

wherein an embossed portion (110) is formed on each heat-transfer plate (100) so that the oil smoothly flows toward the oil recovery hole (200).

2.
The plate-type heat exchanger (1) of Claim 1,
wherein the embossed portion (110) is formed in an L shape along the lower peripheral portion of each heat-transfer plate (100).

3.
The plate-type heat exchanger (1) of Claim 1,
wherein a block wall (203) that prevents the oil from entering a dead space (202) provided below the heat-transfer plates (100) is formed below the oil recovery holes (200).

4.
The plate-type heat exchanger (1) of Claim 3,
wherein the block wall (203) is formed by bringing the embossed portions (110) of the adjacent heat-transfer plates (100) into contact with one another and brazing the contact portions.

5.
The plate-type heat exchanger (1) of any one of Claims 1 to 4,
wherein the oil recovery holes (200) are formed in the shape of an ellipse with a small arch portion at one end, the small arch portion having a smaller radius than the other end, a bottom end (200a) of the small arch portion being provided near a substantially horizontal portion (201a) of the corresponding embossed portion (110).

6.
A method of manufacturing the plate-type heat exchanger (1) of any one of Claims 1 to 5, the method comprising, at least:

forming oil recovery holes (200) in the lower part of the heat-transfer plates (100);

forming L-shaped embossed portions (110) along lower peripheral portions of the heat-transfer plates (100); and

brazing contact portions after the embossed portions (110) are embossed to an intermediate point of a flow clearance between the heat-transfer plates (100), and the embossed portions (110) are brought into contact with the embossed portions (110) of the adjacent heat-transfer plates (100).

7.
The method of manufacturing the plate-type heat exchanger (1) of Claim 6, wherein, in the step of brazing the contact portions, peripheral portions of the oil recovery holes (200) are embossed to an intermediate point of the flow clearance between the heat-transfer plates (100) and are brought into contact with the embossed portions (110) around the oil recovery holes (200) in the adjacent heat-transfer plates (100), and the contact portions are brazed.

8.
The method of manufacturing the plate-type heat exchanger (1) of Claim 6 or 7,
wherein, in the step of forming the oil recovery holes (200), the oil recovery holes (200) are formed in the shape of an ellipse with a small arch portion at one end, the small arch portion having a smaller radius than the other end, a bottom end (200a) of the small arch portion being provided near a substantially horizontal portion (201a) of the corresponding embossed portion (110).

9.
A heat pump device (2) having a refrigeration cycle in which a compressor (3), a condenser (4), an expansion valve, and an evaporator (6) are connected in a circle by pipes,
wherein the plate-type heat exchanger (1) of any one of Claims 1 to 5 is used as the condenser (4) or the evaporator (6), and
wherein the oil recovery holes (200) provided in the plate-type heat exchanger (1) are connected to a suction port of the compressor (3) by a pipe.

10.
The heat pump device (2) of Claim 9,
wherein a water circuit (9) having one or both of a hot-water-supply device and a heating appliance (13) is connected to the plate-type heat exchanger (1).