Evaporator for a refrigeration device

Evaporator for a refrigerator

The present invention relates to an evaporator for a refrigerator. The surface of such an evaporator achieved when this is supplied with refrigerant temperatures below 0 ° C. Humidity from the interior of the refrigerator can therefore condense on the surface of the evaporator and freeze. This produces on the surface of the evaporator, a thin, uniformly distributed layer of frost, which, unless it is defrosted in the meantime, achieved an increasing thickness in the course of operation of the refrigerator and finally coalesces into a solid, rigid layer of ice. Since the temperature of the evaporator varies over time, depending on whether it is supplied with refrigerant or not, this ice layer expands over time periodically and contracts again. Here, tensions between the ice and the underlying evaporator build on that eventually lead to a jerky slipping of ice. The resulting pops are bothersome.

Object of the present invention is to provide an evaporator for a refrigeration device in which these pops are reduced.

The object is achieved in that the surface of the evaporator at which ice could form, is provided with a hydrophobic coating.

Such a coating is effective to delay the formation of an ice-free evaporator first ice crystals, and thus to prolong the time which is required until an amount of ice has accumulated on the evaporator after a defrosting operation. The is strong enough to cause cracking noises. A further effect of the hydrophobic layer is that it prevents the formation of a homogeneous layer of frost on the surface of the evaporator. Instead, the ice begins to a small number of unavoidable germs on the surface of the evaporator. The there forming Eisperlen grow more or less evenly over its entire surface, thus achieving a considerable thickness, before they begin to coalesce. That is, it can collect a large compared to a non-hydrophobic evaporator amount of ice on the evaporator according to the invention, before a continuous layer is formed which is able to generate clicking sounds.

Another benefit of the island growth of ice is that surface areas of the evaporator remain relatively long ice-free and even then allow an effective heat exchange between the refrigerant and the vicinity of the evaporator, if there has already been collected in other areas of the evaporator surface, a considerable amount of ice. The time interval between two defrosting phases can therefore be selected to be longer than in a non-hydrophobic evaporator, which includes a gain in comfort and a reduction in the energy consumption of the refrigeration device and thus its operating costs for the user of a vehicle equipped with an evaporator inventive refrigeration device.

The hydrophobic coating may preferably contain a silicone as hydrophobisierend acting part.

The coating can be solidified as a lacquer layer or are applied as a layer of oil. The oil layer has the particular advantage that they, as it is not fixed in itself, promotes the displacement of the forming Eisperlen on the surface of the evaporator, so that even when fully evaporator icing with a layer thickness of a conventional evaporator generating pops sufficient they are reduced when inventive evaporator because of a shift in the crust with respect to the evaporator no high thermal stresses must be built that erupt in loud cracking noises, but a much lower voltage is sufficient to the ice in terms to let slip on the evaporator or possibly even a continuous sliding of the ice on the evaporator is concluded.

Preferably, the evaporator according to the invention is constructed as a finned evaporator, which is suitable for use in a forced air-cooling or freezing device.

The accompanying figure shows a schematic view of a partially frozen section of a lamellar evaporator invention 4. The finned evaporator 4 comprises a tube 1, which is flowed through during operation of refrigerant. Around the outer surface of the 1 is a tube fin 2 is wound helically. The fin 2 and the outer surface of the pipe 1, on which the blade 2 is mounted, form the effective heat exchange surface of the evaporator fins and are provided with a hydrophobic coating of a silicone oil.

Due to the hydrophobicity of the coating, a lot of energy is required to wet the surface of the fin evaporator 4, and this energy must be free when moisture freezes out on the surface. This is a major obstacle to the formation of ice crystals on the surface. A considerable proportion of the humidity of a flowing past the finned evaporator airflow therefore does not condense on the lamellar evaporator 4, even if the air flow with moisture is supersaturated, simply because the moisture meets no surface to which freezeout would energetically g ünstig. The finned evaporator 4 causes therefore, if it is used in a forced air or no-frost refrigeration device, only a small dry the air in the interior of the refrigerator, which is entirely desirable for the storage of sensitive foods such as fresh vegetables.

Thus humidity in the air evaporator 4 condensed surface areas must it be present, in which the condensation is energetically favorable. Such sites are usually condensation nuclei in the form of dust particles, surface discontinuities or the like, which are inevitably present on the surface of the lamellar evaporator, but account for only a very small part of it. At these condensation nuclei are formed - as shown in Figure 1 -. A plurality of compact Eisperlen 3. On the surface of this Eisperlen 3 preferably further moisture during the operation of lamellar evaporator condensed from the air surrounding the fins evaporator 4, so that the beads 3 in the course of time to thickness and diameter increase while lying between the bead portions of the surface of the lamellar evaporator 4 long time remain free of ice and allow efficient heat exchange between the lamellar evaporator 4 circulating refrigerant and the ambient air.