|Publication number||US3786227 A|
|Publication date||Jan 15, 1974|
|Filing date||Nov 15, 1972|
|Priority date||Nov 15, 1972|
|Also published as||CA990519A, CA990519A1, DE2355356A1, DE2355356C2|
|Publication number||US 3786227 A, US 3786227A, US-A-3786227, US3786227 A, US3786227A|
|Inventors||Clure H Mc, R Seipp|
|Original Assignee||Thermo King Corp|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (7), Referenced by (11), Classifications (11)|
|External Links: USPTO, USPTO Assignment, Espacenet|
United States Patent Seipp et a1. 7
I HEAT EXCHANGER DEF ROST APPARATUS  Inventors: Ronald W. Seipp, Rosemont; Harold E. McClure, Wayzota, both of Minn.
 Assignee: Thermo King Corporation,
22 Filed: Nov. 15, 1972 211 Appl. No.: 306,665
 US. Cl 219/201, 62/276, 219/365,
. .219/530, 219/540  Int. Cl H05b l/0.0, F25d 21/00  Field of Search"... 62/80, 82, 148, 151, 6,2/275-277; 219/341, 365, 530, 540, 200, 201
 References Cited I I I UNITED STATES PATENTS 2,529,215 11/1950 Hicke 62/276X 3,099,914 8/1963 Dewitt et a1. 62/276 3,358,467 12/1967 Hickox et a1. 62/80 X 1,073,813 9/1913 Neiman 219/365 UX 2,492,397 12/1949 Peterson 62/276 1 Jan. 15, 1974 3,138,006 6/1964 Moorman et a1. 62/276 X FOREIGN PATENTS OR APPLICATIONS 1,127,062 4/1962 Germany 219/540 Primary Examiner-A. Bartis Att0rneyF. H. Henson et a1.
 v i ABSTRACT A plate and tube heat exchanger assembly includes a plurality of coolant transporting tubes and a plurality of spaced plates to be periodically defrosted. The tubes pass through the plates and are in heat conducting relationship therewith at junction points with the plates. At least one but less than all of the plates may 1 be modified, according to the instant invention, to include an electric heating element disposed at one end thereof for imparting'heat through the plate and to the tubes and other plates at the junction points therebetween at predetermined times for periodic defrosting. The thickness of the plates having heating elements associated therewith are of a greater thickness than the remainder of the plates.
4 Claims, 3 Drawing Figures HEAT EXCHANGER DEFROST APPARATUS BACKGROUND OF THE INVENTION will be transmitted by conduction to the heat transfer v surfaces of the evaporator to melt accumulated frost and ice build-up. However, these. present attempts have been partially unsuccessful in that the heating elements may be inaccessible or may cause substantial damage if a moisture leak were to cause the heater to explode.
Therefore, it would be desirable to provide an improved apparatus for attaching heating elements to a PRIOR ART Reference may be made to the following U.S. Patent which generally shows defrost apparatus for a refrigeration heat exchanger and evaporator coil including a clamping assembly for retaining an electric heating element to the evaporator coil:
U.S. Pat. No. 2,930,207, L. H. Carl et a1, Mar. 29,
1960. However, no patents are known which disclose a heat exchanger including at least one extending heat exchanger plate having a respective means for importing heat through the plate and to the tubing at junction points therebetween.
SUMMARY OF THE INVENTION This invention relates to a plate and tube heat exchanger assembly, such as that comprising a refrigerator evaporator, which includes a plurality of parallel coolant transporting tubes and a plurality of spaced plates which are to be periodically defrosted. The plates extend transversely from the tubes, and the tubes are adapted to pass through and be in heat conducting. relationship with the plates at junction points with the plates. At least one of the plates has a respective heating element disposed at one end. In the preferred form, the heating element is a tubular electrical heating device which is retained at the end of a respective plate by means of a clamp in order that heat generated by the device may be imparted to the plate and through the tubes to other plates at the junction points therebetween at a predetermined time when it is desired to accomplish the periodic defrosting.
A respective plate having a heating element attached thereto may be modified in accordance with the inven-' tion to include a transversely extending leg. The leg extends below the tubes and is adapted to secure the plate to the assembly defrost and collection pan in order that heat may be supplied thereto in the assembled relationship to insure free draining.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a top plan view of the heat exchanger and evaporator section of a refrigeration system employing the defrost apparatus of the present invention;
FIG. 2 is a frontal elevation of the heat exchanger section assembled in relation to the refrigeration system defrost and collection pan; and
FIG. 3 is an isometric view of one of the heat ex.- change plates modified in accordance with the instant invention to include a tubular electric heating element.
DESCRIPTION OF THE PREFERRED EMBODIMENT Relating to FIGS. 1 and 2 of the drawings, a well known plate and tube heat exchange assembly 1 is shown. Assembly 1 comprises a plurality of generally parallel coolant transporting tube segments 2 and a plurality of thermally conductive spaced plates or thin fin members 4 which extend transversely from the tubes. Tubes 2 may be serially connected together and disposed in the general configuration of a coil 35 with a coolant inlet end 7 and a coolant outlet end 8 by connecting U-shaped end members 6 to tubes 2 as illustrated, or in any other suitable fashion. In the preferred embodiment, heat exchanger assembly 1 is an air cooling evaporator with the connected tube configuration representing the evaporator coil 35. The evaporator assembly 1 also includes conventional transverse frame members 10 and a defrost and collection pan 12, The evaporator coil 35 is adapted to make a series of passes through apertures 25 (best shown in FIG. 3) provided in the fin members. The tube segments 2 are in heat conducting relationship with the junction points formed with the fins.
It is well known that heat exchanger assemblies of the present type require periodic defrosting to prevent the buildup of frost on the fin members 4 which could impede the flow of air therethroughand consequently reduce the cooling effectiveness of the unit. An improved defrost apparatus has been developed which may successfully transmit heat into the evaporator coil to prevent front accumulation among the fin members, as will be detailed more fully hereinafter.
In accordance with the instant invention, individual fin members at regularly spaced intervals may be replaced by a modified thick plate 15 which is fabricated from a highly heat conductive material, such as Aluminum, for example. The thickness of plates 15 may be equal to about ten times the regular thickness of fin members 4. Each plate 15 includes a heating element for defrosting the evaporator and a means for retaining the heating element to the plate. Although, as illus-' trated, the heating element is disposed at one end of the plates 15, it is within the scope of this invention to retain a heating element from both ends of the plates simultaneously. In the preferred embodiment, the heating element is a tubular electric heater 20 such as those known under the trade names of Calrod or Corox, but any other conventional tubular heater may be employed equally well.
As best illustrated in FIG. 3, the heater element is attached to the plate 15 by means of a clamp 22. The clamp 22 may comprise complementary halves 23 and 24 fastened together by any suitable means, such as by bolt 27 with the tubular electric heater 20 interposed between the halves, as shown, or, the clamp may be a single, uniform member.
The defrost apparatus just described may provide a more even thermal distribution across the heat exchanger evaporator coil 35 and defrost more effec tively than conventional methods of imbedding tubular heaters within the edgeof the coil. With the present defrost apparatus, the thick highly heat conductive plates can provide a rigid heater retention means while acting asa primary conduction path for imparting heat through the plate to the tube segments 2 at the junction points therebetween. The heat may then be evenly distributed through the evaporator coil and to the thin fin members 4 at predetermined times for periodic defrosting of the fins when any suitable switch means (not shown), connected in line between an electric power source (not shown) and a respective heater, is manually or automatically turned on to provide the heating element with a current supply.
Heat conducting plates 15 may be further modified as shown in FIG. 3, to include a foot member 30 extending transversely from the plate. As best shown in FIG. 2, foot 30 extends below the evaporator coil 35 to adapt plates 15 to rest upon and be secured to the evaporator defrost and collection pan 12 in the assembled relationship. The tubular heaters may therefore provide a direct source of heat for the collection pan 12 to permit the pan to be freely drained.
A defrost apparatus has been disclosed which not only provides for a uniform heat distribution and effi cient defrosting of the evaporator heat exchange fins but is also a source of heat for the defrost and collecplacement. Other modifications will occur to those skilled in the art.
1. A plate tube heat exchanger assembly including a plurality of parallel coolant transporting tubes and a plurality of spaced plates to be periodically defrosted and extending transversely from said tubes, said tubes passing through said plates and being in heat conducting relationship therewith at junction points with said plates, 2. select number of said parallel plates comprising less than all of said plurality of spaced plates having respective heat imparting means connected thereto, the thickness of each of said select number of plates being greater than the relative thickness of the remainder of the plates not having said heat imparting means, whereby heat is transferred through said select number of plates of increased thickness and to said tubes at the junction points therebetween at predetermined times for periodic defrosting.
2. The invention of claim 1, wherein the means for imparting heat is a tubular electric heater.
3. The invention of claim 1, wherein said heat imparting means is disposed at one end of said respective plates by a clamp.
4. The invention of claim 1, wherein said plates having respective heat imparting means include a foot member extending transversely from said plates to adapt said plates to be secured to a heat exchanger defrost and collection pan.
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|Citing Patent||Filing date||Publication date||Applicant||Title|
|US3918268 *||Jan 23, 1974||Nov 11, 1975||Halstead Ind Inc||Heat pump with frost-free outdoor coil|
|US4346285 *||Apr 23, 1980||Aug 24, 1982||Murata Manufacturing Co., Ltd.||Heating device employing thermistor with positive coefficient characteristic|
|US4369350 *||Mar 17, 1980||Jan 18, 1983||Hitachi, Ltd.||Electric defroster heater mounting arrangement for stacked finned refrigeration evaporator|
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|U.S. Classification||219/201, 219/530, 62/276, 392/480, 219/540|
|International Classification||F25D21/08, H05B3/00|
|Cooperative Classification||H05B3/00, F25D21/08|
|European Classification||H05B3/00, F25D21/08|