The present invention relates to a refrigerator or freezer having a refrigeration circuit condenser for domestic use. The condenser is of the flat hairpin coil type disposed within a heat dissipator, for example comprising wires, bars, metal plates or a finned sheet metal structure, to increase the dispersing surface. Such a condenser is disclosed in GB-A-1 006 039.
In conventional domestic refrigerators (and also in those other domestic appliances incorporating compressor-type refrigeration circuits) the condenser is applied to the rear face of the refrigerator cabinet via spacers (to reduce heat transfer towards that face) and is cooled by convective air movement produced by itself. In other words, its cooling is achieved by environmental air in movement, i.e. by a thermosiphon effect.
This arrangement is certainly economical to produce, but presents considerable drawbacks in its use.
Firstly, the operative conditions of the refrigeration circuit are not optimum because they vary depending on how the refrigerator is used (door opening and closure frequency), the environmental conditions, the location of the refrigerator and its load. To this can be added a decrease in the condenser efficiency with time due to the inevitable deposits of dust, grease etc. which are practically irremovable because of the complexity of the shape of a flat condenser.
The main object of the present invention is to provide an improved refrigerator or freezer which, as practical rests have demonstrated, enables the operative conditions of the refrigeration circuit which incorporates it to be tangibly improved, so reducing its energy consumption for equal conditions.
An accessory object of the present invention is to provide an improved refrigerator or freezer which can be easily cleaned.
These and further objects which will be apparent to an expert of the art from the ensuing detailed description are attained by a refrigerator or freezer in accordance with the teachings of the present invention, these teachings being expressed by the accompanying claims 1 to 7.
The invention will be more apparent from the detailed description of preferred embodiments thereof given hereinafter by way of non-limiting example with reference to the accompanying drawings, in which:
With reference to the drawings, the condenser of the invention comprises a sealed finned box casing 1 enclosing a flat tubular hairpin coil contained, disposed or mounted in a heat dissipator in the form of a finned structure 3 composed of one or more metal sheets. A fluid 4 having a high specific heat fills the interior of the finned box casing 1.
The flat tubular hairpin coil 2 (through which the refrigerant fluid flows) plus the finned structure 3 which contains it or in which it is mounted is substantially identical constructionally to the traditional flat air condensers used in domestic refrigeration appliances, such as refrigerators, freezers or ice producers. The novelty lies in the fact of having positioned it in a sealed box casing filled with a liquid of high specific heat.
The finned sealed box casing is of square or rectangular shape. The relative fins can assume the most varied forms, for example those reproduced schematically in Figures 4A, B, C. The fins are advantageously all parallel and extend vertically (when the condenser is in use), so making it simple to adequately clean the condenser of the invention (this cleaning being necessary to preserve its efficiency); in this manner the condenser of the invention differs from air condensers in which because of the complexity of the shape of the finned sheet metal containing the hairpin coil, adequate cleaning cannot be achieved in practice.
The box casing presents a closable or sealable aperture or port 5 for introducing the fluid, and a sealed entry passage 2A and exit passage 2B for the tubular hairpin coil 2.
The box casing 1 also presents conventional angle brackets 6 for fixing the condenser to the cabinet of the refrigeration appliance.
The box casing can be made of sheet metal (for example steel) or even of plastic material, advantageously so if a good conductor of heat. Its outer faces are preferably black, achieved for example by painting or by pigmentation (in the case of plastic material).
The box casing can be produced by pressing in two or more pieces to be bonded or welded together after mounting the hairpin coil with the relative finned sheet metal structure in one of them. The finned sheet metal structure can be bonded or welded along two opposite longitudinal edges 3A to the minor lateral walls 1A of the casing 1 (as shown for example in Figure 3).
The fluid of high specific heat can be of the most diverse types. This fluid can be mains water, its saline solutions, eutectic mixtures, silicone gels, or mixtures or aqueous solutions of cellulose derivatives such as oxymethylcellulose. A particularly useful and advantageous composition X of such a cellulose derivative is the following:
A comparative test used three refrigerators (in the same environment at a temperature of 25°C) which were identical except that one comprised a conventional air condenser, the second comprised a condenser of the invention with mains water as the filing fluid and the third comprised a condenser of the invention with the aforesaid composition X as the filling fluid. This comparative test provided the following results:
The latter quantity shows that with the liquid condenser according to the invention a substantial energy saving was achieved to the extent of 7.6% and 10.2% respectively, with greater functional equilibrium of the relative refrigeration circuit, to be attributed to the thermal stabilizing effect of the condenser filling fluid and the greater heat transfer surface of the condenser itself.