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  Refrigeration installation and method for operating a refrigeration installationUSPTO Application #: 20070220910Title: Refrigeration installation and method for operating a refrigeration installation Abstract: A refrigerating system comprises at least one refrigerating consumer provided with at least one evaporator, at least one supply line and at least one withdrawal line which enable the coolant or the coolant mixture to be supplied to and/or withdrawn from the refrigerating consumer(s). Expansion elements are associated with the evaporator(s). The expansion elements are embodied as modified expansion valves and/or as modified linear expansion machines or the by-pass lines are associated therewith, and a modified linear compressor or a traditional compressor, which comprises a by-pass line is associated with each refrigerating consumer. The modified expansion valve(S) and/or the modified linear expansion machine(s) and/or the modified linear compressor(s) have a working position which enables a through-flow without a considerable drop in pressure. (end of abstract)
Agent: Bachman & Lapointe, P.C. - New Haven, CT, US Inventor: Uwe Schierhorn USPTO Applicaton #: 20070220910 - Class: 062196100 (USPTO) Related Patent Categories: Refrigeration, Automatic Control, Refrigeration Producer, Bypass, E.g., Compressor Unloading The Patent Description & Claims data below is from USPTO Patent Application 20070220910. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND (1) Field of the Invention [0001] The invention relates to a refrigeration installation having at least one refrigeration consumer, which includes at least one evaporator, having at least one feed line and at least one discharge line, via which the refrigerant or refrigerant mixture is fed to the refrigeration consumer(s) and discharged from the refrigeration consumer(s), respectively, the evaporator(s) being assigned expansion members. [0002] Furthermore, according to a first alternative, the invention relates to a method for operating a refrigeration installation in which the refrigeration compressor(s) is/are assigned modified expansion valves and modified linear compressors. [0003] According to a second alternative, the invention relates to a method for operating a refrigeration installation, in which the conventional expansion valve(s) and the conventional compressor(s) of the refrigeration consumer(s) is/are assigned bypass lines. [0004] In the text which follows, the term "modified expansion valves" is to be understood as meaning all expansion valves which, in addition to the primary function of "expansion of a liquid", have the secondary function of "realization of a fluid connection". The term "modified compressor" in the text which follows encompasses all compressors which, in addition to the primary function of "compression of a gas", also allow the secondary function of "realization of a fluid connection". [0005] The terms "conventional expansion valves" and "conventional compressors" in the text which follows are to be understood as meaning all known designs of expansion valves and compressors which do not have the above-mentioned secondary function. [0006] Refrigeration installations of the generic type are used for example in supermarkets or hypermarkets, where they generally supply a multiplicity of refrigeration consumers, such as cold stores, refrigerator cabinets and/or freezer cabinets. For this purpose, a one-component or multicomponent refrigerant or refrigerant mixture circulates inside them. A refrigeration installation of this type--as is known from DE-C 39 28 430--has a liquefier, in which the pressurized refrigerant (mixture) is condensed by indirect heat exchange, preferably against outside air. [0007] The liquid refrigerant (mixture) from the liquefier is fed to a collection vessel that is optionally to be provided. Within a refrigeration installation, there must always be enough refrigerant to ensure that the evaporators of all the refrigeration consumers can be filled even during the maximum demand for refrigeration. However, since when the demand for refrigeration is lower some evaporators are only partially filled or are even completely empty, the excess refrigerant (mixture), during these times, has to be collected in the collection vessel provided for this purpose. [0008] The refrigerant (mixture) is fed from the collection vessel to the refrigeration consumers via at least one liquid line. An expansion device, preferably an expansion valve, in which the refrigerant (mixture) flowing into the refrigeration consumer or the evaporator(s) of the refrigeration consumer is expanded, is connected upstream of each refrigeration consumer. The refrigerant (mixture) which has been expanded in this way is evaporated in the evaporators of the refrigerant consumers and thereby cools the corresponding refrigeration cabinets or cold stores. [0009] The evaporated refrigerant (mixture) is then fed via a suction line to a compressor unit. These compressor units may be of single-stage or multistage design. The individual compressor stages generally have a plurality of compressors connected in parallel, which compress the refrigerant (mixture) and pass it back, via a riser, to the liquefier which has already been mentioned. Whereas the compressor unit is normally positioned, for example, in a machine room arranged in the basement of a supermarket, the liquefier is located on the roof of the supermarket. [0010] The compressors used are generally oil-lubricated reciprocating piston compressors which are driven in rotation. One drawback in this case is that corresponding measures have to be taken to allow the oil released from the reciprocating piston compressor to be separated from the refrigerant (mixture). Furthermore, it is generally necessary to ensure that the oil which has been separated off is fed back to the reciprocating piston compressor(s). To enable the oil to be separated off, the mixture of refrigerant and oil first of all has to be passed to specific points within the cycle, and consequently minimum velocities have to be reached in rising suction and pressure lines, since the oil would not otherwise be entrained. These minimum velocities mean small pipe diameters, resulting in additional, undesired pressure losses and therefore energy losses. To avoid these pressure and energy losses in risers, it is necessary to split lines, but this in turn results in increased installation outlay. Therefore, process aspects are undesirably closely linked to economic aspects. [0011] As an alternative to the procedure described above, the system of a cold vapor refrigeration installation, in which a distinction is drawn between subcritical (with reliquefaction) and supercritical (with gas recooling) operation, so that a "gas cooler" is used instead of the "liquefier" component, it is also possible for a gaseous refrigerant (mixture) to circulate in a refrigeration installation, which under the given boundary conditions (pressure, temperature, etc.) is not in liquid form at any time. This is then what is known as cold gas refrigeration installation, also referred to as a Joule, Stirling or Gifford-McMahon installation. [0012] The text which follows will simply use the term "liquefier". If the process in question is a cold vapor compression process in the two-phase range, it is actually a liquefier that is used. In the case of a supercritical procedure or gas processes, the term "liquefier" in turn stands for a gas cooler. It is essential for heat to be dissipated from the cycle process. The liquefaction can take place in an air-cooled apparatus, in an intermediate-pressure separator or alternatively by means of a further assembly connected in a cascade. A cascade connection is present whenever there is a further refrigeration machine which is operated at a higher temperature level and which alone dissipates the heat of liquefaction to the environment. The refrigeration set is in this case dependent on this refrigeration machine and in turn transfers its heat of liquefaction thereto. By way of example, it is possible for a standard cooling set to be connected upstream of a freezing set, in which case the two cooling sets may have different refrigerants or refrigerant mixtures. [0013] If what are known as normal cooling points and what are known as freezing points are present inside a hypermarket or supermarket, these are generally supplied by means of separate refrigerant cycles; this therefore means that there are at least two refrigeration installations as described in DE-C 39 28 430. [0014] The refrigeration installation or the evaporators arranged in the refrigeration consumers have to be defrosted at regular intervals, since frosting or icing of the evaporators leads to a reduction in the efficiency of the evaporators. One defrosting option is electrical defrosting, in which the evaporators are defrosted by means of electrical heaters arranged in and/or on them. However, this procedure leads to an undesirable increase in the consumption of electrical energy. [0015] What is known as compressed gas defrosting is a recommended alternative to the electrical defrosting described above. In this case, compressed-gas lines are laid between the gas space of the collection vessel connected downstream of the liquefier and each evaporator or evaporator module, and refrigerant, which is preferably at a temperature of between 35 and 45.degree. C., is fed from the collection vessel to the evaporators or evaporator modules via these compressed-gas lines. However, the installation outlay for this compressed-gas defrosting is relatively high, since either a separate compressed-gas line has to be provided for each evaporator or each evaporator module or, as is customary in the two-wire system, switching valves and a second set comprising the same refrigerant (mixture) are required. Furthermore, there is the possibility of defrosting by means of circulated air at temperatures above approx. 2.degree. C. SUMMARY OF THE INVENTION [0016] It is an object of the present invention to provide a refrigeration installation of the generic type which in terms of investment and operating costs and also reliability has advantages over the refrigeration installations of the prior art. [0017] To achieve this object, the invention proposes a refrigeration installation which is distinguished by the fact that [0018] the expansion members are designed as modified expansion valves and/or as modified linear expansion machines or are assigned bypass lines, and [0019] each refrigeration consumer is assigned a modified linear compressor or a conventional compressor, which includes a bypass line, [0020] the modified expansion valve(s) and/or the modified linear expansion machine(s) and/or the modified linear compressor(s) having a working position which allows flow to pass through without a significant pressure drop. [0021] Most linear compressors operate as oil-free cryogenic Stirling coolers at extremely low temperatures and extremely low powers, i.e. in cold-vapor compression. In cold-vapor compression, linear compressors have only been implemented for a few years and have hitherto not been deployed extensively. In the cooling sector, the applicant is only aware of one application, namely the use of a linear compressor in a domestic refrigerator. A drawback of linear compressors is that their production costs have hitherto been well above those of reciprocating-piston compressors driven in rotation, but of a similar order of magnitude to inverter compressors. Only in the 1960s were efforts made to exploit the advantages of linear compressors. The principle of friction-free mounting of the piston only dates from this time. Even so, it was only in the 1990s that improvements were made to the operational reliability, by virtue of reliable electronic reciprocating controllers. In this case, it was or is necessary in particular to ensure that for example fluctuating pressures do not lead either to the piston striking the cylinder head or to premature termination of the reciprocating operation at the top dead center, associated with an excessive damage volume and volumetric or energy drawbacks of re-expansion. [0022] Linear compressors have the advantage of allowing continuously variable power control, which is realized by reciprocating control. Furthermore, they can be operated without oil. Furthermore, the condensate which is inevitably formed during defrosting operation does not cause any damage to them. Furthermore, they are superior in energy terms to oil-lubricating reciprocating piston compressors which are driven in rotation. [0023] Although they are operated without oil, the oil-lubricated compressors which are driven in rotation are superior in energy terms. This results on the one hand from the efficient linear motor and on the other hand from the elimination of the mechanical losses, of which about 80% occur at the driving mechanism and about 20% at the piston. The piston of a linear compressor is mounted without contact and can be guided by what are known as flexible bearings, which allow axial mobility combined with radial rigidity. This ultimately means a spring combination of uncoiling and coiling springs which impart a rotary movement to the piston about its longitudinal axis in addition to its periodic translatory movement. [0024] Since they do not have any sliding-contact bearings, linear compressors can be operated without oil. This absence of oil gives rise to numerous advantages. In the case of compressed-gas defrosting with condensation, the bearings, which have hitherto been relatively vulnerable, can no longer be damaged by liquid refrigerant (mixture). The formation of acid which is known when using lubricating oils and can lead to burn-out of the winding of built-in motors, has hitherto been more or less effectively avoided by the use of refrigerant dryers. These molecular sieve dryers can now be dispensed with unless the water content is so high that there is a risk precipitation of ice during the expansion. Irrespective of this, it is recommended that dirt filters be provided immediately upstream of the expansion valves or machines. Continue reading... Full patent description for Refrigeration installation and method for operating a refrigeration installation Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Refrigeration installation and method for operating a refrigeration installation patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. 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