CN1710367A - Microchannel parallel flow heat exchanger for transcritical CO2 cycle and method of manufacture - Google Patents

Abstract

A method for preparing microchannel and parallel flow exchanger for transcritical CO2 circulation includes extrusion - moulding collector tube in multi-tube structure and heat exchanging flat tube separately to let one side of multi-tube collector tube be planar structure, making parallel slots for heat exchanging flat tubes on planar side of multi-tube collector tube, using weld flux to cover the part of the flat tube to be welded and applying vacuum one - body brass soldering for finishing .

Description

Microchannel parallel flow heat exchanger for transcritical CO2 cycle and method of manufacture

technical field

The invention relates to a microchannel parallel flow heat exchanger used in transcritical vapor compression refrigeration and heat pump devices using _CO2 as a working medium, in particular to a gas cooler or evaporator used in refrigeration and heat pump devices.

Background technique

In the heat exchangers used in _CO2 transcritical cycle refrigeration and heat pump devices, one of the heat exchangers works on the high-pressure side of the system, and supercritical _CO2 releases heat in the heat exchanger tubes to cool, and the pressure can reach above 10MPa. The ambient air heats up through the fins outside the tube. This heat exchanger is called a gas cooler; the other heat exchanger works on the low-pressure side of the system, and subcritical _CO2 absorbs heat and evaporates in the heat exchanger tube, with a pressure of 4MPa Left and right, it exchanges heat with air at room temperature or lower ambient temperature, and this heat exchanger is called an evaporator. Because of the high _CO2 pressure in these two heat exchangers, if the heat exchanger is designed according to the conventional size, the wall thickness of the heat exchange tube will increase a lot, making the whole heat exchanger heavy and bulky.

Since the microchannel structure can well solve the problem of pressure resistance, the wall thickness of the _CO2 pipe in the heat exchanger does not need to be too thick; and because the viscosity of supercritical _CO2 is small, the flow pressure loss in the microchannel structure is small; CO ₂ The heat transfer coefficient is high, and the same heat exchange amount only requires a small heat exchange area, so the heat exchanger using the microchannel structure has a better application prospect in the CO ₂ transcritical cycle.

A micro-channel parallel flow heat exchanger is disclosed in the prior art. This micro-channel parallel flow heat exchanger has been used in automobile air conditioners. The working fluid used is mostly R134a, and its working pressure is below 3MPa. The heat exchange channel adopts a rectangular shape that does not need to withstand high pressure; the cross-sectional size of the heat exchange channel is within 2×3mm, and its collector adopts a single round tube structure.

Man-Hoe Kim et al. introduced foreign designed transcritical CO ₂ cycle gas cooling in the document "Fundamental process and system design issues in CO ₂ vaporcompression systems", Progress in Energy and Combustion Science.2004, 30: 144-149 The evaporator (see Figure 1) is made of aluminum, using 8-shaped double-tube headers (see Figure 2) and micro-channel heat exchange flat tubes; the evaporator introduced in this article is made of aluminum, using 4 tubes Heat exchange flat tubes of headers (see Figure 3) and microchannels. Using this multi-tube header structure can provide sufficient welding width with the flat tube; at the same time, compared with the single header, the diameter of each channel of the multi-tube header is reduced, and compared with the single Channels with large diameter tubing that can withstand higher pressures. However, the 8-shaped double-tube header or four-tube header has fluctuations in the shape of the arc surface, and the solder is not easy to adhere to the surface to be welded, and the welding of the header and the flat tube bundle is difficult. Difficult; the temperature will also be locally uneven during the welding process, and the welding quality is not easy to control. As the number of parallel tube bundles increases, the yield of the heat exchanger decreases significantly.

Contents of the invention

The purpose of the present invention is to provide a microchannel parallel flow heat exchanger for transcritical _CO2 circulation and a manufacturing method, to ensure the welding quality between the header and the flat tube bundle, and to improve the yield of the microchannel heat exchanger.

Technical scheme of the present invention is as follows:

A microchannel parallel flow heat exchanger for transcritical _CO2 circulation, including a multi-tube header and a heat exchange flat tube bundle welded between the two headers, the heat exchange flat tube adopts a microchannel structure, and the collector The tube adopts a multi-tube structure with at least two flow channels, and the feature is that: the welded surface of the collector tube of the multi-tube structure and the heat exchange flat tube bundle adopts an extruded overall planar structure.

The present invention also provides a method for manufacturing the microchannel parallel flow heat exchanger, which is characterized in that the method is carried out as follows:

1) extruding the multi-tube structure header and the heat exchange flat tube respectively, so that one side of the header is a planar structure;

2) opening parallel heat exchange flat tube grooves on the plane side of the collecting pipe;

3) Wrap solder on the parts to be welded of each heat exchange flat tube, respectively insert them into the grooves of the heat exchange flat tubes, fix the positions of the heat exchange flat tube bundles, and vacuum braze the whole.

Compared with the prior art, the present invention has the following advantages and outstanding effects: the multi-tube header with a planar structure is adopted, on the one hand, the plane side of the multi-tube header is thickened, and the strength is enhanced, offsetting the The effect of weakening the strength brought by a set of heat exchange flat tube slots. On the other hand, during the welding process, the solder is first wrapped on the part of the flat tube to be welded, so that the solder is easy to adhere to the surface to be welded, the heat is relatively uniform, and the welding quality is easy to control, thereby effectively improving the overall yield of the heat exchanger.

Description of drawings

Fig. 1 is an appearance structure diagram of a microchannel parallel flow heat exchanger adopted in the prior art.

Fig. 2 is a cross-sectional view of the double-tube header of the microchannel parallel flow heat exchanger in the prior art at the welding place of the heat exchange flat tube groove.

Fig. 3 is a cross-sectional view of the four-barrel header of the microchannel parallel flow heat exchanger used in the prior art at the welding place of the heat exchange flat tube groove.

Fig. 4 is a schematic diagram of the section structure of the heat exchange flat tube.

Fig. 5 is a schematic diagram of the three-dimensional structure of the microchannel parallel flow heat exchanger provided by the present invention.

Fig. 6a is a sectional view of the multi-tube header of the microchannel parallel flow heat exchanger provided by the present invention.

Fig. 6b is a cross-sectional view of the multi-tube header of the microchannel parallel flow heat exchanger provided by the present invention at the welding place of the heat exchange flat tube groove.

Detailed ways

The structure and manufacturing method of the present invention will be further described below in conjunction with the accompanying drawings.

Fig. 5 is a schematic diagram of the three-dimensional structure of the microchannel parallel flow heat exchanger provided by the present invention. The microchannel parallel flow heat exchanger contains a multi-tube header 1, and a heat exchange flat tube bundle 2 welded between the two headers. Fins 3 are welded between the parallel flat tube bundles. Fig. 6 a is the schematic cross-sectional structure diagram of the multi-barrel header provided by the present invention, one side of which is designed as a plane and formed by extrusion; in order to be welded with flat tube bundles, mill out parallel tubes with flat tube thickness and width on the welding plane Heat exchange flat tube tank 4 (Fig. 6b).

The CO ₂ working medium first enters the multi-tube header 1 (inlet header) on one side of the heat exchanger, and then enters the parallel microchannel flat tube bundle 2 from the multi-tube header 1 to carry out the process with the air outside the flat tube bundle. heat exchange. The _CO2 working fluid after heat exchange flows out from the multi-tube header (outlet header) on the other side of the heat exchanger.

The preparation method provided by the present invention is as follows: first, the multi-tube header 1 and the heat exchange flat tube are extruded separately, and generally the multi-tube header adopts a structure of 2 to 5 tubes, so that one side of the header is a plane Structure; the cross-sectional diameter of the microchannel of the heat exchange flat tube is 0.7-1.2mm. When welding, first open parallel heat exchange flat tube grooves 4 on the plane side of the multi-tube header, and then wrap a thin layer of solder on the part to be welded of each heat exchange flat tube in the heat exchange flat tube bundle 2, and install into the heat exchange flat tube groove 4 that has been opened on the multi-tube header, after fixing the welding positions of all the heat exchange flat tube bundles 2 and the multi-tube header 1, the flat tube bundle 2 and the multi-tube header 1 are completed by overall vacuum brazing Welding between one multi-barrel header. In this way, the heating is relatively uniform, and the welding quality is easy to control, thereby effectively improving the overall yield of the heat exchanger.

Claims (3)

1. one kind is used to stride critical CO ₂The micro-channel parallel flow heat exchanger of circulation, comprise many headers (1) and be welded on two flat heat exchange pipe bundles (2) between header, flat heat exchange pipe adopts MCA, header adopts many barrel structures of at least two runners, it is characterized in that: the header of described many barrel structures and flat heat exchange pipe bundle solder side adopt the integral planar structure of extrusion modling.

2. according to the described parallel-flow heat exchanger of claim 1, it is characterized in that: described header adopts 2～5.

3. the manufacture method of a micro-channel parallel flow heat exchanger as claimed in claim 1 is characterized in that this method carries out as follows:

1) with the header and the flat heat exchange pipe extrusion modling respectively of many barrel structures, making a side of described header is planar structure;

2) leave parallel flat heat exchange pipe groove (4) in the planar side of described header;

3) superscribe scolder at the position to be welded of every flat heat exchange pipe, insert respectively in the flat heat exchange pipe groove, fix flat heat exchange pipe bundle position after, the overall vacuum soldering.

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