Stack type evaporator

• US 5,470,431 A
• Filed: 09/17/1993
• Issued: 11/28/1995
• Est. Priority Date: 08/20/1990
• Status: Expired due to Term

• Current Assignee: Keihin Thermal Technology Corporation
• Original Assignee: Showa Aluminum Corporation (Resonac Holdings Corp.)
• Inventors: Kojima, Masayoshi, Okuda, Nobuyuki
• Primary Examiner(s): Manoharan, Virginia
• Application Number:
  US08/123,856
• Time in Patent Office: 802 Days
• Field of Search: 159/28.6, 159/DIG. 23, 159/27.1, 159/DIG. 21, 165/153, 165/134.1, 165/170, 165/913, 165/133, 165/111, 165/152, 165/177, 106/197.1, 203/287.1, 203/10, 203/86, 202/237, 202/267.1
• US Class Current: 159/28.6
• CPC Class Codes: F25B 39/022 with plate-like or laminated elements
• CPC Class Codes: F25B 47/00 Arrangements for preventing or removing deposits or corrosion, not provided for in another subclass
• CPC Class Codes: F28D 1/0333 the plates having integrated connecting members
• CPC Class Codes: F28D 9/0056 with U-flow or serpentine-flow inside conduits; with centrally arranged openings on the plates
• CPC Class Codes: F28F 13/18 by applying coatings, e.g. radiation-absorbing, radiation-reflecting; by surface treatment, e.g. polishing
• CPC Class Codes: F28F 17/005 Means for draining condensates from heat exchangers, e.g. from evaporators F28B9/08 takes precedence
• CPC Class Codes: F28F 2245/02 hydrophilic
• CPC Class Codes: Y10S 159/21 Coating
• CPC Class Codes: Y10S 159/23 Cooling
• CPC Class Codes: Y10S 165/913 Condensation

Abstract

A stack type evaporator includes tubular elements 1 each having a plurality of inwardly protruding recessed ribs 7 which extend from an upper header portion 1a of the element to a lower header portion 1b, with the ribs serving as straight drainage canals 7a of specified width and area. A hydrophilic resin coating of a specific composition covers the outer surfaces of the tubular elements 1 and fins 2 each interposed between two adjacent tubular elements. The combination of straight drainage canals, the specified width and area thereof and the specific hydrophilic resin coating is effective to facilitate the drainage of condensed water so that the waterdrop is substantially prevented from flying out of the evaporator, and the hydrophilic coating itself does not emit any unpleasant smell.

Claims

1. In a stack evaporator comprising:

a plurality of tubular elements each composed of a pair of facing core plates which are adjoined one to another at their peripheries so as to define a coolant path therebetween;

a plurality of fins each interposed between the two adjacent tubular elements which are stacked side by side in a direction of their thickness;

upper and lower header portions respectively formed at an upper and lower ends of each tubular element, with the header portions being connected to the other corresponding header portions so as to unite the tubular elements to form the evaporator wherein except for the header portions of the tubular elements located at predetermined positions of evaporator, the other tubular elements adjacent to each other have their header portions in fluid communication with one another through coolant flowing openings formed through summits of said header portions, wherein the walls of header portions at the predetermined positions of the first mentioned tubular elements function as partitions, which divide the tubular elements to form groups thereof, and which partitions thereby cause the coolant entering the evaporator through a coolant inlet pipe to advance in a meandering manner making turns at every boundary between the groups, before leaving the evaporator through a coolant outlet pipe;

wherein the improvement comprises

a plurality of straight drainage canals for condensed water, the drainage canals being formed on the outer surface of the core plates forming each tubular element so as to extend vertically in parallel with one another from the upper header portion towards the lower header portion;

a hydrophilic resin coating covering the outer surfaces of the tubular elements and the fins;

the hydrophilic resin coating being applied by immersing said outer surfaces in a solution containing a polyvinyl alcohol resin as its main component, polyamide and/or polyvinyl pyrrolidone resins as its hydrophilic agent blended with the main component, a film hardener having a concentration sufficient to produce a hardened coating but not so great as to react with hydrophilic atom groups in the hydrophilic resin molecules and thereby fail to enhance the hydrophilic property, and a surfactant to stabilize said resin solution so that it will not become bubbly;

the thickness of said hydrophilic resin coating falling in a range of from about 0.2 to about 1.5 μ

m;

a width of each straight drainage canal covered with the hydrophilic resin coating being included in a range of from about 0.5 to about 3 mm, the width being defined as a distance between surfaces of the resin coating covering an open mouth of the canal;

a depth of straight drainage canals falling within a range of from about 0.5 to about 2.5 mm, the depth being defined as a distance between a portion of the resin coating covering a flat portions and another portion of the resin coating covering a bottom of each drainage canal; and

a surface area ratio falling within a range of from about 5 to about 40%, the surface area ratio being a ratio of a total area of the open mouths to an overall surface area of each core plate, and the overall surface not including expanded end regions of the core plate but inclusive of flat portions and the straight canals thereof, whereby the combination of said parallel drainage canals and said coating in said stack type evaporator results in substantially lower odor and retained water as compared to a coated scattered rib evaporator.

2. A stack type evaporator as defined in claim 1, wherein the width of each straight drainage canal is from about 1.3 mm to about 2.4 mm, and the surface area ratio is from about 15% to about 25%.

3. A stack type evaporator as defined in claim 2, wherein a depth of straight drainage canals is from about 1.5 mm to about 2.1 mm.

4. A stack type evaporator as defined in claim 1, wherein the hydrophilic resin coating further contains a microbicide.

5. A stack type evaporator as defined in claim 1, wherein the hydrophilic resin coating is composed of:

from about 30 to about 65 parts by weight of polyvinyl alcohol resin as the main component;

from about 20 to about 65 parts by weight of the hydrophilic agent;

from about 1 to about 15 parts by weight of the film hardener; and

from about 0.1 to about 2.0 parts by weight of the surfactant.

6. A stack type evaporator as defined in claim 5, wherein from about 3 to about 30 parts by weight of a microbicide is further contained in the hydrophilic resin coating.

7. A stack type evaporator as defined in claim 1, wherein the hydrophilic resin coating is composed of:

from about 40 to about 60 parts by weight of polyvinyl alcohol resin as the main component;

from about 35 to about 45 parts by weight of the hydrophilic agent;

from about 5 to about 10 parts by weight of the film hardener; and

from about 0.5 to about 1.5 parts by weight of the surfactant.

8. A stack type evaporator as defined in claim 7, wherein from about 5 to about 15 parts by weight of a microbicide is further contained in the hydrophilic resin coating.

9. A stack type evaporator as defined in claim 4, 6 or 8, wherein the microbicide is a member selected from a group consisting of:

bis-(2-pyridylthio)-zinc 1,1'"'"'-diphoxide;

methyl benzimidazole carbamate; and

2-(4-thiazolyl)-1H-benzimidazole.

10. A stack type evaporator as defined in claim 1, wherein the thickness of the hydrophilic resin coating is from about 0.5 to about 1.3 μ

m.

11. A stack type evaporator as defined in claim 1 wherein the film hardener is a member selected from a group consisting of a phenolic resin and a polyurea resin.

12. A stack type evaporator as defined in claim 1 wherein the surfactant is a nonionic surface active agent.