US 3388562 A
Description (OCR text may contain errors)
H. P. HARLE 3,333,562
REFRIGERATION SYSTEM INCLUDING COATED CONDENSER June 18, 1968 Filed Sept. 22, 1966 INVENTOR.
HAROLD P. HARLE W H \S ATTORNEY United States Patent 3,388,562 REFRIGERATION SYSTEM INCLUDING COATED CONDENSER Harold P. Harle, Louisville, Ky., Assignor to General Electric Company, a corporation of New York Filed Sept. 22, 1966, Ser. No. 581,320 3 Claims. (Cl. 62-507) ABSTRACT OF THE DISCLOSURE A refrigerator including a machinery compartment having a condenser therein. The condenser is coated with material which resists adhesion thereto of foreign substances.
The present invention relates to refrigeration systems including a condenser provided with a coating effective substantially to prevent the adherence to the condenser surfaces of foreign substances carried by an air stream and is more particularly concerned with a household refrigerator including a forced air cooled condenser having thereon a surface coating which prevents the accumulation of dust and other foreign substances on the surface of the condenser.
A relatively large number of household refrigerators include a machinery compartment containing the condensing component of the refrigeration system including a compressor and a relatively compact condenser, and a fan for the forced circulation of ambient or indoor air over the condensing unit for cooling purposes. The condenser usually comprises a serpentine refrigerant tubing provided with a plurality of closely spaced wire or platetype fins or mounted on or bonded to a sheet of metal. It is well known that during operation of a forced air cooled condenser of this type, foreign substances present in the stream of household air circulated over the condenser collect on the surfaces and eventually build up to an insulating layer which materially decreases the condensing capacity of the condenser.
The collection of such foreign substances on the condenser surfaces and the eventual clogging of the air passages therein constitutes a particular problem in the household refrigerator art. The foreign substances carried by or comrningled with the household air stream passing over a household refrigerator condenser include not only particulate matter such as lint and dust but also a fluid component, usually an oil or grease, which not only accelerates the collection of the particulate component on the condenser surface but also prevents the circulating air stream from dislodging the lint and dust-like particles from the condenser surface once they have come in contact therewith. Because of this heterogenous composition of the foreign substances present in the household air stream, household refrigerator condensers require periodic cleaning much more frequently than condensers operating, for example, in outdoor ambients. In fact, many complaints of loss of cooling capacity are in fact due only to clogged or coated condensers. Therefore, various means have been used or proposed for preventing the loss of condenser efiiciency resulting in these complaints. However, none of the means heretofore used or proposed have been completely satisfactory either from an operational or cost standpoint.
An obvious solution to the problem is the provision of an air filter ahead of the condenser. However, because of the limited space available in a household refrigerator cabinet and particularly because the average user forgets that this filter must periodically be changed or cleaned, the provision of a filtering means has usually been found to result in an actual increase, rather than a decrease,
in such service calls. It has also been proposed to provide a reversible fan means on the theory that foreign substances filtered from the circulating air stream as the air flows in one direction will be removed from the condenser by the reversed flow of air. However, because the liquid or greasy particles in household air tend to bond the dust and lint particles to the condenser surfaces and to one another the mere reversal of the air stream does not serve to dislodge any substantial portion thereof. Another proposed solution to this problem has been the provision of electrically operated heating means or in other words a lint burner ahead of or in contact with the condenser. However, the addition of such means materially increases the cost of the refrigerator.
The present invention has as its primary object the provision of a condenser having a surface coating of a material which will substantially prevent the initial adhesion of foreign substances present in household air to the condenser surfaces and thereby prevent the continuing accumulation of such foreign substances on the condenser structure.
Further objects and advantages of the invention will become apparent from the following description thereof and the features of novelty which characterize the invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.
In accordance with the present invention, a condenser is provided with a surface coating which resists the adhesion thereto of foreign substances carried by a household air stream and thereby effectively prevents the continued accumulation of such foreign substances on the condenser structure. More specifically, a condenser of the household refrigerator type comprising a plurality of spaced transverse tubular refrigerant conduits and a plurality of spaced longitudinally extending fins is provided with a substantially continuous surface coating of a polymer selected from the group consisting of polytetrafluoroethylene, polyhexafluoropropylene and copolymers of tetrafluoroethylene and hexafiuoropropylene.
For a better understanding of the invention reference may be had to the accompanying drawing in which:
FIGURE 1 is a vertical sectional view of a portion of a household refrigerator including the improved condenser of the present invention; and
FIGURE 2 is an enlarged sectional view of the condenser taken generally along line 22 of FIGURE 1.
With reference to the drawing, there is shown a household refrigerator including a storage compartment 1 designed to be maintained at refrigerating temperatures by means of an evaporator (not shown) forming part of a refrigeration system and a machinery compartment 2 at the lower portion of the cabinet for containing the condensing component of the refrigeration system including a compressor 3 and a condenser 4. It is to be understood that the compressor 3, the condenser 4 and the evaporator are connected by suitable conduits to form a closed refrigerant circuit including suitable fiow restricting means between the compressor and evaporator.
In the illustrated cabinet, the machinery compartment 2 is divided into two sections by means of a longitudinally extending partition 5 running generally from the rear wall 6 of the refrigerator cabinet to the front wall 7. A fan 8 mounted in the rear portion of the partition 5 draws a stream of household air inwardly through one side of a grille 9 provided at the lower front portion of the cabinet into cooling relationship with the condenser 4 and the compressor 3 and discharges the air back into the room through the other end of the grille 9.
The illustrated condenser 4, as is more clearly shown in FIGURE 2 of the drawing, is made by forming a continuous tube into a serpentine form to provide a structure including a plurality of spaced transverse refrigerant conduits 11 series connected by means of lU-shaped end turns 12. In order to provide a compact structure, the passes 11 are arranged in a plurality of sections or tiers, three in number as shown in FIGURE 2. The passes 11, in each of these tiers are provided with additional or secondary heat transfer surface in the form of a plurality of closely spaced parallel wires 14 extending perpendicular to the passes 11 or in other words longitudinally of the evaporator structure. Preferably wires 14 are secured to both the upper and lower surfaces of the passes in each of the tiers.
During operation of the fan 8, any foreign substances suspended in the room or household air are circulated along with the air stream into contact with the surfaces of the condenser 4. A few of these particles of the dry or lint type become lodged in the crevices or recesses between a pass 11 and a wire or wires 14 but such collected particles do not materially interfere with the efliciency of the condenser. The major loss in condenser efiiciency results from the deposition on and ready adherence to the otherwise smooth or continuous condenser surfaces, including both the surfaces of the passes 11 and the surfaces of the fins or Wires 14, of a continuation of the fluid and lint types of substances and the continuous accumulation of such foreign substances to form a relatively thick insulating layer of foreign substances on the condenser surfaces. This accumulation has been found to result from the presence of the high proportion of the oily or greasy components in household air which may be in the range of 22 percent by weight of the total foreign substance contents as compared with from to 13 percent of such oily materials in vacuum cleaner dirt or dirt suspended in the average outdoor atmosphere.
In other words, while the collection of inert particulate matter and air borne fiber fragments on a condenser surface may be caused by both mechanical entrapment and adhesion, adhesion due to the presence of the oil fluid components is the principal factor. The present invention is based in part of the discovery that the retention of the oil component is strongly dependent upon the nature of the surface contacted thereby.
In accordance with the invention, the adhesion and retention of oil bonded lint and dust by virtue of an intervening oil film which wets both these soil particles or fiber residues and the surface is substantially prevented by providing a condenser surface designed to reduce the oil adhesion and also to reduce the degree of spreading of any oil film on that surface. It has been found that the highly fiuorinated polymers and copolymers are particularly effective for this purpose. More specifically, it has been found that the polymers of fully fluorinated polyethylene and polypropylene or copolymers thereof are most effective in reducing the adhesion to the condenser surface of oil air borne particulate mixtures.
Therefore in accordance with the present invention, the condenser 4 is provided with an exterior coating of a material such as polytetrafluoroethylene, or polyhexafluoropropylene or copolymers of the tetrafiuoroethylene and hexafiuoropropylene, such a coating being indicated in FIGURE 2 of the drawing by the numeral 15.
This dust and grease resistant coating may be applied to the condenser surfaces by any of the well known methods used for coating metal surfaces with the above enumerated materials. For example, the coatings may be applied to the finished condenser structure by a spray-- ing or dipping process employing a suspension of the finely divided polymer or polymers although in the manufacture of some condenser structures as for example the metal plate fin-on-tube condenser, the individual components that is the individual plate-type fins and the tubing may be pre-coated prior to the assembly of the fins on the tubing.
While surfaces composed of the subject polymers and copolymers are well known for their non-adhesive p operties as shown for example by the extensive use of polytetrafiuoroethylene in the greaseless fry pan and related cooking utensil art their effectiveness in preventing the adhesion of air borne foreign substances to a condenser surface was far greater than would have been expected from their known uses. For example, a wire fin-on-tube condenser of the construction illustrated in the drawing having no surface coating or merely a corrosion protective paint surface coating of black enamel, when subjected to an accelerated test to determine the amount of air borne dust composed primarily of oily lint and dust accumulated thereon in test conditions to simulate five years of actual usage in a home became completely clogged with such foreign substances.
On the other hand, the same condenser structure provided with a continuous surface coating of polytetrafluoroethylene when subjected to the same test did not become clogged and in fact had thereon only a very thin film of deposited particles of a thickness such that the surfaces of the condenser was still apparent through the layer. The amount of accumulation on the treated condenser surfaces was less than percent of the amount collected on the untreated surfaces.
While there has been shown and described a particular embodiment of the present invention it will be understood that it is not limited thereto and is intended by the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.
What I claim as new and desire to secure by Letters Patent of the United States is:
1. A household refrigerator comprising a machinery compartment and a refrigeration system including an air cooled condenser disposed in said compartment and forced air circulating means for circulating a stream of air through said compartment and over said condenser,
said condenser comprising a plurality of spaced transverse tubular refrigerant conduits and a plurality of spaced longitudinally extending fins connected to said conduits,
said condenser exterior surface being coated with a polymer selected from the group consisting of polytetrafluoroethylene, polyhexafluoropropylene and copolymers of tetrafiuoroethylene and hexafluoropropylene whereby the adherence of foreign substances carried by said stream of air to said surface is substantially reduced.
2. The refrigerator of claim 1 in which said polymer is polytetrafluoroethylene.
3. The refrigerator of claim 1 in which said machinery compartment is in the lower part of said cabinet.
References Cited UNITED STATES PATENTS 3,079,770 3/1963 Brown 62-507 XR 3,341,348 9/1967 Letendre 117132 FOREIGN PATENTS 972,129 10/ 1964 Great Britain.
MEYER PERLIN, Primary Examiner.