A METHOD OF BARZING A PLATE HEAT EXCHANGER USING SCREEN PRINTED BRAZING MATERIAL; A PLATE HEAT EXCHANGER MANUFACTURING BY SUCH METHOD

• US 20160250703A1
• Filed: 10/24/2014
• Published: 09/01/2016
• Est. Priority Date: 10/29/2013
• Status: Active Grant

• Current Assignee: SWEP International AB (Dover Corporation)
• Original Assignee: SWEP International AB (Dover Corporation)
• Inventors: BORNEGARD, Niclas
• Granted Patent: US 10,035,207 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: B23K 1/0012 Brazing heat exchangers
• CPC Class Codes: B23K 1/008 Soldering within a furnace B23K1/012 takes precedence
• CPC Class Codes: B23K 1/19 taking account of the properties of the materials to be soldered
• CPC Class Codes: B23K 2101/14 Heat exchangers
• CPC Class Codes: F28D 9/005 the plates having openings therein for both heat-exchange media
• CPC Class Codes: F28F 21/083 from stainless steel
• CPC Class Codes: F28F 2275/045 with particular processing steps, e.g. by allowing displacement of parts during brazing or by using a reservoir for storing brazing material
• CPC Class Codes: F28F 3/046 the deformations being linear, e.g. corrugations
• CPC Class Codes: F28F 3/08 Elements constructed for building-up into stacks, e.g. capable of being taken apart for cleaning
• CPC Class Codes: F28F 3/086 having one or more openings therein forming tubular heat-exchange passages

Abstract

A method for brazing a plate heat exchanger comprising a stack of heat exchanger plates (110,115) is provided with a pressed pattern of ridges (R) and grooves (G) adapted to form contact points between the plates (110, 115) and provide for interplate flow channels for media to exchange heat is provided. The interplate flow channels are in selective fluid communications with port openings (120, 130, 140, 150) provided near corners of the heat exchanger plates (110, 115). The method comprises the following steps:

calculating or measuring the exact position of all contact points between the ridges (R) and grooves (G) of the neighboring plates (110, 115);

applying brazing material (B) close to, but not at, the contact points; stacking heat exchanger plates (110, 115) provided with brazing material to a stack ; placing the stack of heat exchanger plates (110, 115) in a furnace; heating the stack of heat exchanger plates (110, 115) to a temperature sufficient for melting the brazing material (B); and allowing the stack of heat exchanger plates (110, 115) to cool down such that the brazing material (B) solidifies and binds the plates (110, 115) together.

Claims

1. Method for brazing a plate heat exchanger comprising a stack of heat exchanger plates provided with a pressed pattern of ridges and grooves adapted to form contact points between the plates and provide for interplate flow channels for media to exchange heat, said interplate flow channels being in selective fluid communications with port openings provided near corners of the heat exchanger plates, the method including the steps of:

i. calculating or measuring the exact position of all contact points between the ridges and grooves of the neighboring plates;

ii. applying brazing material close to, but not at, the contact points;

iii stacking heat exchanger plates provided with brazing material to a stack;

iv. placing the stack of heat exchanger plates in a furnace;

v. heating the stack of heat exchanger plates to a temperature sufficient for melting the brazing material; and

vi. allowing the stack of heat exchanger plates to cool down such that the brazing material solidifies and binds the plates together, and

wherein

step ii. includes screen printing the brazing material in half moon shaped, donut-shaped or ( )-shaped patterns neighboring the contact point.

2. The method according to claim 1, including the further step of:

applying brazing material on skirts surrounding the heat exchanger plates and areas around the port openings that should be joined.

3. The method according to claim 1, wherein the brazing material is applied in at least one minute groove extending around said port opening.

4. The method according to claim 1, wherein the brazing material is applied in the form of a paste.

5. The method according to claim 1, wherein the brazing material is an iron based brazing material containing a base of stainless steel and additives of melting point depressants, e.g. silicon, boron and/or phosphorus.

6. The method according to claim 1, wherein the brazing material is a nickel based brazing material.

7. The method according to claim 1, wherein the brazing material is a copper based brazing material.

8. The method according to any of the preceding claims claim 1, wherein the brazing material is placed such that it is in contact with both the ridges of the pressed pattern of one plate and the grooves of the pressed pattern of a neighboring plate.

9. The method of claim 1, wherein the brazing material is placed on one side of the contact point only.

10. The method of claim 1, wherein a flux is provided at the contact points between the neighboring plates.

11. The method according to claim 1, wherein the brazing operation is performed under a vacuum, a reducing or a protective atmosphere.

12. The method according to claim 1, wherein the brazing material is applied only to areas in which a gap having the height h between the groove a of an upper heat exchanger plate and the ridge of a lower heat exchanger plate is larger than the grains of the brazing material.

13. The method according to claim 1, wherein the brazing material is applied to a surface corresponding to less than 5% of the entire surface of the heat exchanger plate.

14. A brazed heat exchanger comprising a number heat exchanger plates provided with a pressed pattern of ridges and grooves for providing contact points between the heat exchanger plates while keeping the plates on a distance from one another under formation of interplate flow channels for media to exchange heat, wherein port openings are provided for selective fluid communication with the interplate flow channels, wherein the heat exchanger plates are brazed to one another by the method as defined in any of the preceding claims.