DE102005021154A1 - Moisture-removing system and process for evaporator in cooling units and heat pumps has cooling circuit with evaporator compressor condenser and evaporation unit and cooled moisture removing passage and by pass - Google Patents

Abstract

The invention relates to a defrosting system for evaporators (4) of refrigeration systems and heat pumps and to a method for operating the defrosting system. DOLLAR A According to the invention, the defrosting system for evaporators (4) of refrigeration systems and heat pumps from a refrigeration cycle and an acted upon with refrigerant condensate defrosting is constructed. The refrigeration cycle comprises a ring line (7.2) with an evaporator (4) arranged in the flow direction of the refrigerant, with at least one evaporator line (4.1), a compressor (2), a condenser (1) and an expansion element (3). The defrosting passage has a bypass line (7.1), which, starting from a distribution point (14) placed between the condenser (1) and the expansion element (3), via at least one defrosting line (4.2) additionally arranged in the evaporator (4) a mixing point (13) placed between the condenser (1) and the expansion element (3).

Description

The This invention generally relates to a defrost system for evaporators of refrigeration systems and heat pumps and a method of operating the defrost system. In particular The invention relates to a defrost system for evaporators of refrigeration systems and Heat pumps and a method of operating the defrost system, which is for commercial and domestic Cold and Heating purposes are used.

At the cooling down ambient air or the air in a cold room condenses Part of the humidity at the surface of the evaporator of the heat pump or the chiller. Is the ambient temperature of the evaporator of a heat pump below approx. 7 ° C, The condensed water begins to freeze as the temperature of the refrigerant in the evaporator and coupled to it the surface temperature of the evaporator due to operation 0 ° C below. The forming on the evaporator surface Ice layer has an insulating effect, reducing the heat transfer from the ambient air to the refrigerant is difficult. Due to the progressive growth of this ice layer becomes the heat transfer increasingly worse, which leads to the efficiency the heat pump or chiller decreases significantly.

Around the cooling or heating operation of the chiller or heat pump Therefore, at air temperatures between -7 ° C and + 7 ° C, the evaporator must be maintained defrosted regularly become. At lower temperatures, defrosting is due to the only low humidity not necessary, as only a small Amount of water from the air can condense.

Out The prior art is various defrosting systems for evaporators of heat pumps and chillers and various methods for operating these defrosting systems previously known. at a first defrost system is a circuit switching. in this connection the capacitor works while the defrosting process as an evaporator, wherein in particular in an air / water heat pump, the heating water can freeze in the evaporator. To prevent this, one must be sufficient large heating water buffer tank be provided so that even with closed heating circuits sufficient heat disposal stands. While the defrosting operation is not heating, although the compressor is in Operation is. Another disadvantage of this Abtausystems consists in the cooling down of the heating circuit, which is not insignificant on the efficiency of plant to be defrosted.

at a second prior defrost system, the hot gas for Defrosting the evaporator used. Using a controlled solenoid valve becomes the hot gas passed directly into the evaporator. Again, this takes place during the defrosting process an interruption of the cooling or heating operation. Although the compressor is in operation, supplies the system no heating or Cooling capacity.

at a third prior art Abtausystem is a separate electrical Defrost heater used to defrost the evaporator. During the Defrosting the compressor is switched off and thus the cooling or Heating operation interrupted.

adversely is that exergetically valuable electrical energy to produce of heat is used to defrost the ice layer.

In the US 6,250,090 B1 is a defrost system with condensate supercooling described in which the evaporator tubes of the evaporator are used simultaneously for the defrosting of the evaporator with condensed refrigerant.

In the DD 281 009 A1 discloses an arrangement and a method for operating plate freezers, in which the defrosting operation is realized by condensate subcooling. The arrangement comprises a refrigeration cycle and a condensate-powered defrost massage with a plate freezer, a compressor, a condenser, two collectors, a pump and several fittings. The designed as an evaporator Plattengefrierapparat is in this case connected to supply and discharge lines, each having a rotating part and a fixed part. The rotating part of the supply and discharge lines assumes a different position depending on the selected operating mode, namely defrosting or freezing operation, and is thus coupled to either the refrigeration cycle or the defrosting passage. The defrosting and the freezing operation can therefore take place only in chronological succession. A disadvantage of this invention is also that the rotating parts of the supply and discharge lines are maintenance-intensive and need another drive.

From the DD 232 341 A1 a defrost method for air dehumidifiers with an evaporator, a condenser, a fan and a compressor is previously known. In this case, the energy required for the defrosting process is made available in the form of heat from the refrigeration process while the chiller is running. For this purpose, the air is reversed in the flow direction and used to absorb the condensation heat of the cooling process for defrosting.

The The object of the invention is now a Abtausystem for Defrosting of evaporators of refrigeration systems and heat pumps to suggest that too during of the cooling operation or heat pump operation and works for the Defrosting process no additional Energy supply is necessary. Furthermore, a method for operating a be developed such Abtausystems.

These Task is solved by by the defrost system for Evaporators of refrigeration systems and Heat pumps from a refrigeration cycle and one with refrigerant condensate acted upon defibrillator is constructed. The refrigeration cycle comprises a ring line with a flow direction of the refrigerant arranged evaporator with at least one evaporator line, a Compressor, a condenser as well as an expansion organ. According to the invention, the defrost massage has a Bypass on, starting from one between the condenser and the expansion organ placed over at least distribution point an additional in the evaporator arranged Abtauleitung up to a between the condenser and the expansion organ placed mixing point extends.

at In the present invention, during the cooling or heat pump operation, the "hot" condensate is present and the condenser pressure having refrigerant in the evaporator supercooled and used to defrost the evaporator. The whole flows refrigerant or only part of the refrigerant from the liquefier over the Distribution point using the bypass to the evaporator, will be there in addition provided defrosting of the evaporator supercooled and happens as a supercooled Condensate over the mixing point the expansion element, then to the evaporator lines the evaporator completely evaporated to become.

There the supercooling performance of the evaporator is insufficient to complete the evaporator performance compensate, it is only under certain climatic conditions possible, the entire evaporator surface Defrost in cooling or heat pump operation. The available standing supercooling performance but it is big enough in addition to the needed heat output to defrost also cover part of the evaporator performance. This makes it possible sections of the evaporator during of the cooling or defrost the heat pump operation, with each section of the evaporator the total defrosting capacity and the evaporator performance corresponding to this section disposal stands. The available standing defrosting capacity corresponds to the maximum possible supercooling capacity less the evaporator power to be covered.

In a preferred embodiment are more in the evaporator Defrosting lines and possibly several evaporator lines provided, the respective output side or input side, a shut-off valve exhibit. The evaporator lines and the defrosting lines are preferred alternating and mutually arranged in the evaporator, wherein in each case a defrost line and an adjacent evaporator line a section correspond to the evaporator or form a section. The can Evaporator lines and the Abtauleitungen both straight as also U-shaped in the Extend evaporator. The advantage of a straight design of the evaporator lines and the defrosting lines opposite a U-shaped Training consists in the lower energy losses. In the U-shaped training The condensate at the inlet to the evaporator also gives heat to the Condensate on exit. This heat is "lost" and can not be used for defrosting become. Due to the presence of a constant temperature in the evaporator lines is the flow direction of the condensate irrelevant.

Under Use of the shut-off valves can all sections of the evaporator simultaneously or preferably only one section in the evaporator by condensate supercooling enteist become. For partial defrosting of the evaporator is a shut-off valve the defrosting line corresponding to this section opened and the remaining shut-off valves closed. After complete defrosting of this section the evaporator will do this operation for the remaining sections of the evaporator repeated one after the other. During the Defrosting a section stand both this section as also the rest Sections of the evaporator are available simultaneously for cooling purposes. A Barrier of the thawed section associated evaporator line is not mandatory. When the shut-off valve of the evaporator line is open, the evaporator transfers the entire performance; however, the defrosting process is slowed down. For special Applications and operating conditions for this case must be the evaporator larger dimensions must be because less heat transfer surface to disposal stands and absorbed by the condensate supercooling more power would have to be than the ordinary Heat pump operation.

It has proven to be particularly advantageous in practice when the defrosting lines and the evaporator lines of the evaporator in each case upstream of a distributor and a collector is connected downstream. On the one hand, the condensate collector and condensate distributor on one side of the evaporator and the evaporator collector and Ver steam distributors are placed on a second opposite side of the evaporator orthogonal to the flow direction of the air flowing through the evaporator. On the other hand, the manifold and collector can also be arranged on a common side of the evaporator. Finally, the manifolds and collectors can also be integrated into the evaporator. The shut-off valves already mentioned are placed either on the collectors and manifolds or in a pipe section between the collectors and manifolds and the evaporator.

In A preferred embodiment of the invention is the distribution point as a 2-way valve formed with an input terminal and two output terminals. The outlet of the condenser is here with the input terminal, the first output terminal is with the deflate bypass bypass line and the second output port is with the loop of the refrigeration cycle coupled. Instead of a 2-way valve can also two 1-way valves be used in the bypass and the loop are placed.

According to the invention can each an evaporator line and a defrost line of the evaporator not only one section of the evaporator forming side by side, but rather, also together in a combination line designed as a coaxial line be summarized. This is located in the annular gap of the coaxial line the condenser pressure having refrigerant for defrosting and in the Inner tube containing the evaporator pressure refrigerant for cooling the Section of the evaporator. By trained as a coaxial line Combination line is an optimal heat conduction of which the condenser pressure having refrigerant scored to the evaporator surface. While the defrosting process becomes the heat flow from the cooling fins interrupted to the evaporator tube, wherein for the defrosting the same spatial Wärmeleitbedingungen as in the evaporation. The arrangement of the cooling fins of Evaporator tubes can also be optimized to that effect.

at the sections according to the invention Arrangement of evaporator lines and defrosting lines in the evaporator, for example, in the execution As a combination line, the evaporator line must be in several of the Number of necessary sections of the evaporator corresponding Number of parallel branches to be split. This is why required, otherwise a large part of the total evaporator capacity deprived of the portion to be defrosted, resulting in that the power to defrost is no longer sufficient.

at the combination line designed as a coaxial line is closed Beginning of defrosting increased heat transfer from the present as a "warm" condensate and the condenser pressure having refrigerant to the evaporating refrigerant to record. As a result, evaporates the evaporator pressure having refrigerant already relatively fast on the first centimeters. That now as a vapor refrigerant but then causes a much poorer heat transfer from the refrigerant located in the inner tube to the in the annular gap located refrigerant, which is present as condensate, which is why then increasingly a heat conduction to the evaporator surface and this is de-iced.

In order to the supercooling performance even at outside temperatures below 0 ° C sufficient to defrost the evaporator is, according to a preferred embodiment the invention covered the portion to be defrosted. For this Purpose, each section of the evaporator each have a hinged and optionally thermally insulating cover or it is a single movable, strip-like hinged cover for all sections provided the evaporator together. For the latter case extends itself arranged on a carriage strip-like cover between the guide rails a preferably electric motor driven propulsion device.

In A preferred embodiment of the invention is the hinged Cover and the shut-off valve of the defrosting line of a section of the evaporator using a central control and regulating device coupled together. The control of the hinged cover and the shut-off valve is such that the hinged cover and the shut-off valve always mutually in the open and closed state are located. This means, one opened for the purpose of defrosting a portion of the evaporator Shut-off valve of the defrost line is assigned a closed cover.

Around an air-side heat exchange between the individual sections of the evaporator to prevent are preferred between the individual sections of the evaporator parallel to the Abtauleitungen extending separating elements, For example, dividers, provided.

• a. zumindest teilweise Freigabe des Strömungspfades der Umgehungsleitung unter Verwendung des als 2-Wege-Ventil ausgebildeten Verteilpunktes,
• b. Öffnen des Absperrventils einer Abtauleitung des Verdampfers und Schließen der übrigen Absperrventile des Verdampfers,
• c. nach erfolgtem Abtauen eines Abschnitts des Verdampfers Wiederholung des Verfahrensschritts b. für alle weiteren Abtauleitungen und Verdampferleitungen des Verdampfers zeitlich nacheinander und
• d. Verschließen des Strömungspfades der Umgehungsleitung unter Verwendung des als 2-Wege-Ventil ausgebildeten Verteilpunktes.

According to the invention, the method for operating the defrosting system for evaporators of refrigeration systems and heat pumps using the device features of the defrosting system described above comprises the following method steps:

• a. at least partially releasing the flow path of the bypass line using the distribution point designed as a 2-way valve tes,
• b. Opening the shut-off valve of a defrosting line of the evaporator and closing the remaining shut-off valves of the evaporator,
• c. after defrosting of a section of the evaporator repetition of the process step b. for all other Abtauleitungen and evaporator lines of the evaporator in chronological order and
• d. Closing the flow path of the bypass line using the designed as a 2-way valve distribution point.

alternative may be a partial defrost of the evaporator without an interruption of the cooling or heat pump operation when fully released of the flow path the bypass line and when completely closing the flow path the ring line using the designed as a 2-way valve Distribution point done.

According to the invention can be also a simultaneous defrosting of all sections of the evaporator by a simultaneous opening all shut-off valves of the defrosting of the evaporator realize. This mode of operation is preferably suitable for the transition area to freezing submissions. By an increase the total evaporator surface temperature In certain climatic conditions, a freezing of the condensed Humidity prevents.

at a power-controlled heat pump must the evaporator is not larger because of the maximum power in the temperature range in which one Freezing occurs, not needed becomes. At temperatures around 0 ° C About half the rated power is needed. The extra power that needed by the larger condensate subcooling, can therefore easily be included without additional effort.

The Abtausystem invention for evaporators of refrigeration systems and heat pumps can also be particularly advantageous in conjunction with a power-controlled compressor and natural refrigerants, such as CO ₂ , use.

• • energetisch und anlagentechnisch effizienter Abtauprozess,
• • das für den Abtauprozess erforderliche Kältemittel wird nach dem Abtauprozess vollständig verdampft, wodurch eine Gefährdung der Verdichter durch zum Teil flüssiges Kältemittel verhindert wird,
• • es werden keine zusätzlichen Komponenten, wie z. B. Sammelbehälter, Pumpe, Heizstäbe, Phasentrenner oder Wärmespeicher, benötigt,
• • der Abtauprozess kann während des Kälte- bzw. Wärmepumpenbetriebs durchgeführt werden,
• • durch Verwendung von als Koaxialrohren ausgebildeten Kombinationsleitungen wird eine effiziente Wärmeübertragung zwischen dem im Ringspalt des Koaxialrohrs strömenden Kondensat und der Verdampferoberfläche erzielt und
• • durch Platzierung mehrerer voneinander unabhängig mit „warmen" Kondensat beaufschlagbaren Abtauleitungen im Verdampfer kann dieser sowohl vollständig als auch abschnittsweise abgetaut werden.

The significant advantages and features of the invention over the prior art are essentially:

• • energetically and plant-technically efficient defrosting process,
• • the refrigerant required for the defrosting process is completely evaporated after the defrosting process, thus preventing any risk to the compressors due in part to liquid refrigerant,
• • there are no additional components, such as B. collecting container, pump, heating rods, phase separator or heat storage, requires
• The defrosting process can be carried out during the operation of the refrigeration or heat pump,
• • By using designed as a coaxial combination tubes efficient heat transfer between the flowing in the annular gap of the coaxial condensate and the evaporator surface is achieved and
• • By placing several independently with "warm" condensate acted upon defrosting in the evaporator this can be defrosted both completely and in sections.

Further Features and advantages of the invention will become apparent to those skilled in the art from the following detailed description of preferred embodiments with regard to the attached drawings; in these show:

1 FIG. 2: shows a system diagram of a defrosting system according to the invention for evaporators of refrigeration systems and heat pumps, FIG.

2 : Detailed representation of the evaporator of refrigeration systems and heat pumps with condenser-side shut-off valves according to a preferred embodiment,

3 : Detail of the evaporator of refrigeration systems and heat pumps with condenser side and evaporator side shut-off valves according to a further preferred embodiment and

4 : Detailed view of the evaporator of refrigeration systems and heat pumps using combination pipes with condenser-side shut-off valves according to a further preferred embodiment.

The 1 illustrates a system diagram of a Abtausystems invention for refrigeration systems and heat pumps using the example of a compression refrigeration machine with single-stage compression. The compression refrigerating machine essentially comprises an evaporator in the flow direction of the refrigerant 4 , A compressor driven by an electric motor, for example 2 , a liquefier 1 as well as an expansion organ 3 using a loop 7.2 connected to each other. There is also a fan 6 and to control the compression refrigeration machine nor an unrepresented electrical switchgear and control and auxiliary equipment not shown provided. According to the previously known from the prior art circuit arrangement of the refrigeration systems is the Outlet of the evaporator 4 with the low pressure side of the compressor 2 , the high-pressure side of the compressor 2 with the inlet of the condenser 1 , the outlet of the condenser 1 with the high pressure side of the expansion device 3 and the low pressure side of the expansion device 3 with the entrance of the evaporator 4 by means of the ring line 7.2 coupled together. The refrigerant goes through a cycle, being in the evaporator 4 is evaporated with the delivery of a cooling capacity, subsequently in the compressor 2 is condensed to condenser pressure, then in the condenser 1 is liquefied under release of the heat of condensation and finally in the expansion device 3 is relaxed again to evaporator pressure. The Abtausystem invention comprises a designed as a 2-way valve multi-way valve 5 as distribution point 14 , a bypass line 7.1 and a special, described in more detail elsewhere embodiment of the evaporator 4 , The 2-way valve has three connections 5.1 to 5.3 on, of which a first inlet-side connection 5.1 with the outlet of the condenser 1 , a second outlet side connection 5.3 using the flow line bypass 7.1 with the evaporator 4 and a third drain side port 5.2 with the entrance of the expansion organ 3 are coupled. Further, a return of the bypass line 7.1 provided, extending from the evaporator 4 up to a mixing point 13 extends, the mixing point 13 on the loop 7.2 between the third drain side port 5.2 of the 2-way valve 5 and the entrance of the expansion organ 3 is placed. The in the 2 to 4 shown in detail and disclosed in the following description evaporator 4 has several defrosting lines 4.2 on, these defrosting lines 4.2 on the input side of the evaporator 4 with the flow of the bypass line 7.1 and on the output side of the evaporator 4 with the return of the bypass line 7.1 are coupled. When using several in the evaporator 4 placed defrosting lines 4.2 It has proved to be particularly advantageous when the evaporator 4 on the input side, a condensate distributor 10 and on the output side a condensate collector 9 upstream. Every single defrosting line 4.2 is shared with a neighboring evaporator line 4.1 a section of the evaporator 4 assigned or together form a section. The condensate distributor 10 and the condensate collector 9 each have a plurality of nozzles or branches, where the defrosting 4.2 using unspecified pipe sections in the condensate distributor 10 and the condensate collector 9 are involved. Between the evaporator 4 and the condensate collector 9 are several shut-off valves 8th provided for bypassing individual sections of the evaporator 4 , respectively blocking individual defrosting pipes 4.2 , are used. In every single one of these sections of the vaporizer 4 can provide the necessary subcooling performance for the entire evaporator 4 as well as the proportion of the evaporator power are delivered. By shutting off individual shut-off valves 8th can optionally one or possibly more sections of the evaporator 4 defrosted at the same time.

In the event that all sections of the evaporator 4 be defrosted at the same time, it is necessary, the individual sub-volume flows in each Abtauleitungen 4.2 to balance hydraulically. These are the shut-off valves 8th are formed as control valves and are vorgesrosselt different depending on the portion associated with this portion of the evaporator pressure loss differently, to a same pressure drop across all Abtauleitungen 4.2 including the bypass 7.1 , to achieve. Another possibility is an equal pressure drop across all defrosting lines, including the bypass line 7.1 In addition, it is to provide the flow and the return of the bypass line 7.1 to the condensate distributor 10 and to the condensate collector 9 according to the principle of the same path lengths mutually connect.

The shut-off valves and the control valves 8th can be operated manually or preferably by an electric motor. In the latter case, the associated servo motors of the shut-off valves 8th coupled using signal lines with a control and regulating device, not shown, and are acted upon by this with a control signal. The also coupled with this control device and designed as a distributor 2-way valve 5 has two flow paths. A first flow path extends from the input-side first terminal 5.1 to the output side connection 5.2 , In the event that this first flow path is fully opened, the refrigerant flows using the loop 7.2 in the conventional cooling mode in the circuit through the evaporator 4 , the compressor 2 , the liquefier 1 , the 2-way valve 5 and then the expansion organ 3 , In addition, the 2-way valve 5 a second flow path extending from the input side first port 5.1 to the output side connection 5.3 extends. In the event that this second flow path is fully opened, the refrigerant flows with open shut-off valves 8th both in defrost mode and in cooling or heat pump operation - starting from the 2-way valve 5 - via the supply line of the bypass 7.1 to the evaporator 4 , from the evaporator 4 over the return line of the bypass 7.1 to the mixing point 13 , there flows into the ring line 7.2 and flows over the evaporator 4 to the compressor 2 , continue through the condenser arranged below 1 and closing the refrigeration cycle up to the 2-way valve 5 , It is understood by those skilled in the art that the 2-way valve 5 also assume each open position between the first and the second flow path steadily can. In each case, a predeterminable refrigerant partial volume flow flows in each flow path. The valve cone of the 2-way valve 5 can be designed with a linear, quadratic or equal-percentage valve characteristic, equal on both sides, ie symmetrical or different, ie asymmetrical. Depending on the defrost requirement of the evaporator 4 can the ratio of the refrigerant partial volume flows in favor of a larger release of the connection 5.3 of the 2-way valve 5 be varied. At each position of the valve cone of the 2-way valve 5 in which the second flow path is not completely closed, ie the connection 5.3 is at least partially open, designed as a compression refrigeration unit refrigeration system both defrosting at the same time to defrost the evaporator 4 as well as in cooling mode, respectively mixed operation, work. However, it should be noted here that the necessary evaporator capacity in the defrosting operation is higher by the supercooling capacity and, as a result, the evaporator may have to be designed to be larger. The refrigerant then has a lower enthalpy when entering the evaporator than without condensate supercooling, which must be compensated for complete evaporation. The further the connection 5.3 is open, the larger the partial volume flow, which during the defrosting of the evaporator 4 in the defrosting lines 4.2 of the evaporator 4 is undercooled. During the mixing operation, the two, a different temperature refrigerant partial volume flows combine to the total refrigerant flow. Again 1 it can be seen, on the low pressure side of the compression refrigeration machine only the total refrigerant volume flow and on the high pressure side, both the total refrigerant volume flow and the two refrigerant partial volume flows can flow. The evaporator 4 is preferably oriented inclined in its installed position, so that the resulting condensate collects at a point and can be reliably removed from this point. Hereinafter, three preferred embodiments of the structure of the evaporator 4 based on 2 to 4 described.

The 2 shows a detailed view of the evaporator 4 the refrigeration system with fan and condenser-side shut-off valves according to a preferred embodiment. In this embodiment of the invention, the evaporator 4 seven defrosting lines 4.2 and six evaporator lines 4.1 on, which are each equipped with longitudinally extending fins and alternately and parallel to each other in the evaporator 4 are placed. Test series have shown that in a heat pump with 10 kW heating capacity, equivalent to about 9 kW evaporator capacity, about 2.5 kW supercooling capacity are available. Alone to defrost the entire evaporator 4 with an assumed defrost bag of 0.5, about 1.2 kW of subcooling power is necessary. The evaporator 4 is in this case in 7 Divide sections, taking each section of the evaporator 4 the necessary subcooling performance for the entire evaporator 4 plus the evaporator capacity "of a section" is made available 4.1 and the defrosting lines 4.2 each extend U-shaped over almost the entire width of the evaporator 4 , wherein in each case the headers and the returns of the evaporator lines 4.1 as well as the headers and the return lines of the defrosting lines 4.2 are placed mutually to each other, ie on the opposite sides of the evaporator 4 , begin or end.

At the viewer's right side of the evaporator 4 are the evaporator collector 11 and the evaporator manifold 12 placed, which is substantially orthogonal to the direction of flow of air through the evaporator 4 extend. The evaporator distributor 12 is here using the loop 7.2 according to 1 on the one hand with output, ie the low pressure side, of the expansion organ 3 and on the other hand with the individual headers of the evaporator lines 4.1 connected. The evaporator collector 11 however, with the returns of the individual evaporator lines 4.1 and according to 1 using the loop 7.2 with the suction side of the compressor 2 connected. At the viewer's left side of the evaporator 4 are the condensate collector 9 and the condensate distributor 10 placed, which is substantially orthogonal to the direction of flow of air through the evaporator 4 extend. The condensate distributor 10 is here according to 1 on the one hand with the flow of the bypass line 7.1 and on the other hand with the individual headers of the defrosting lines 4.1 connected. The condensate collector 9 is here according to 1 on the one hand with the return of the bypass line 7.1 and on the other hand with the returns of the individual defrosting lines 4.2 connected. Between the individual returns of the individual defrosting lines 4.2 and the condensate collector 9 are outside the evaporator 4 each shut-off valves 8th arranged to ensure the hydraulic balancing as well as the partial defrosting of the evaporator 4 are provided. For the partial defrosting, the defrosting line assigned to any section becomes 4.2 using the associated shut-off valve 8th opened and the remaining shut-off valves 8th closed. The defrost of the individual sections of the evaporator 4 is preferably in succession, but can be done simultaneously. Both the condensate collector 9 and distributors 10 as well as the evaporator collector 11 and distributors 12 can be designed as desired in cross-section and in the material condition. In practice, one would expediently choose a pressure and temperature-resistant plastic or a light metal.

The 3 shows a detailed view of the evaporator 4 the refrigeration system with condenser-side and evaporator-side shut-off valves 8th according to a further preferred embodiment. The construction of the evaporator 4 is essentially the same as the 2 , The difference over 2 However, this is that between the evaporator collector 11 and the individual evaporator lines 4.1 each additional shut-off valves 8th are placed. Since, as already mentioned, the evaporator lines 4.1 and the defrosting lines in the evaporator 4 alternating, ie evaporator lines 4.1 and defrosting lines 4.2 are alternately juxtaposed, it is for the purpose of completely defrosting a portion of the evaporator 4 particularly advantageous that the immediately adjacent to the Abtauleitungen 4.2 arranged evaporator lines 4.1 do not switch refrigerant leading. The reason for this is the fact that the relatively large temperature difference between the evaporation temperature of the refrigerant of the evaporator lines 4.1 and the temperature of the refrigerant condensate to be cooled, complete defrosting of the evaporator 4 with special needs. For this purpose, during defrosting any section of the evaporator 4 the evaporator lines placed in this section 4.1 by means of the associated evaporator-side shut-off valves 8th closed while the remaining shut-off valves 8th are open. Since in this embodiment of the invention always a portion of the evaporator 4 is not available for evaporation of the refrigerant, it should be noted that the evaporator 4 must be oversized by the proportion of a section. However, this is offset by the advantages that also defrost the evaporator 4 during cooling or heat pump operation is possible and only one expansion device 3 and no additional storage and phase separator (gaseous / liquid) are needed.

The 4 illustrates a detail of the evaporator 4 the refrigeration system using combination tubes with condenser-side shut-off valves according to a further preferred embodiment. Outside the evaporator 4 are again each one to the bypass line 7.1 connected condensate distributor 10 and collectors 9 and one each to the ring line 7.2 connected evaporator distributor 12 and collectors 11 placed. Between the condensate collector 9 and the evaporator 4 are in the defrosting lines 4.2 Shut-off valves 8th arranged, with which individual defrosting lines 4.2 Refrigerant leading can be switched. The construction of the evaporator 4 differs from the design of the evaporator 4 in the 1 and 2 to the effect that the evaporator lines 4.1 and the defrosting lines 4.2 not alternating, so are placed alternately next to each other, but each an evaporator line 4.1 and a defrosting line 4.2 as combination line 4.3 are formed. In the example shown, the evaporator 4 six as a coaxial tube, so tube-in-tube formed combination cables 4.3 on that in the evaporator 4 next to each other and thereby orthogonal to the flow direction of the evaporator 4 are placed through flowing air. Each coaxial tube is a section in the evaporator 4 assigned, in which refrigerant is evaporated and which is used for subcooling, ie for defrosting. The refrigerant having the evaporator pressure is in this case in the inner tube and the refrigerant present as condensate and having the condenser pressure in the outer tube surrounding the inner tube. The advantage of using coaxial tubes used for defrosting and evaporation is the good heat transfer between the condensate and the evaporator surface. Furthermore, the same heat conduction conditions for the defrosting and the heat absorption during the evaporation are to be noted, wherein the arrangement of the fins of the coaxial tubes can be additionally optimized to increase the heat conduction conditions. As in the previously described embodiments of the evaporator 4 according to the 1 and 2 , also exists with the evaporator 4 according to 4 the possibility of the evaporator 4 Partially defrost. In order to still provide sufficient supercooling performance for defrosting one or more sections at outdoor air temperatures below 0 ° C, the section that is being defrosted must be covered. To cover preferably flaps are used, which are controlled by a motor. According to the invention a combination line is for each 4.3 having provided portion each having either a fixed cover, or a single movable strip-like cover for all sections together. For the latter case, the arranged on a slide strip-like cover extends between the guide rails of an electric motor driven propulsion device. It has proven to be particularly advantageous if the flap associated with a section or covering a section and the associated shut-off valve 8th control technology can be coupled together using a central control and regulating device, not shown. During the defrosting process of a section of the evaporator 4 opens the associated shut-off valve 8th so that the condensate refrigerant through the defrosting 4.2 flows, is undercooled there and thus defrosts this evaporator section. At the same time closes the portion of the evaporator to be defrosted 4 Covering flap and thus prevents extensive contact of this section with the ambient air. To prevent the combination tube during defrosting 4.3 Cold air flows through the fins of the evaporator are parallel to Longitudinal axis of the combination tubes 4.3 aligned. In those sections of the evaporator 4 that are not being defrosted, the "standing" condensate refrigerant acts as an insulator, requiring a lower evaporative temperature to be required.

1

condenser

2

compressor

3

expansion element

4

Evaporator

4.1

evaporator line

4.2

defrost duct

4.3

combination line

5

Multi-way valve

5.1

input side connection

5.2

output side connection

5.3

output side connection

6

fan

7

connecting line

7.1

bypass line

7.2

loop

8th

shut-off valve

9

condensate collector

10

condensate distributor

11

evaporator collector

12

evaporator distributor

13

mixing point

14

distribution point

Claims (13)

Defrost system for evaporators ( 4 ) of refrigeration systems and heat pumps, consisting of a refrigeration cycle and acted upon by a refrigerant condensate defrosting passage, wherein the refrigeration cycle is a ring line ( 7.2 ) with an evaporator arranged in the flow direction of the refrigerant ( 4 ) with at least one evaporator line ( 4.1 ), a compressor ( 2 ), a liquefier ( 1 ) as well as an expansion organ ( 3 ), characterized in that the defrost passage a bypass line ( 7.1 ) which, starting from one between the liquefier ( 1 ) and the expansion organ ( 3 ) placed distribution point ( 14 ) via at least one additional in the evaporator ( 4 ) arranged defrosting line ( 4.2 ) to one between the liquefier ( 1 ) and the expansion organ ( 3 ) placed mixing point ( 13 ). Defrosting system according to claim 1, characterized in that the distribution point ( 14 ) as a 2-way valve with an input port ( 5.1 ) and two output terminals ( 5.2 . 5.3 ), wherein the output of the condenser ( 1 ) with the input terminal ( 5.1 ), the first output terminal ( 5.3 ) with the bypass ( 7.1 ) of the defrost passage and the second output port ( 5.2 ) with the ring line ( 7.1 ) of the refrigeration cycle are coupled. Defrosting system according to claim 1 or 2, characterized in that the defrosting line ( 4.2 ) and / or the evaporator line ( 4.1 ) of the evaporator on the input side or on the output side a shut-off valve ( 8th ). Defrosting system according to one of claims 1 to 3, characterized in that the defrosting lines ( 4.2 ) and the evaporator lines ( 4.1 ) of the evaporator ( 4 ) one distributor each ( 10 . 12 ) and a collector ( 9 . 11 ) is connected downstream. Defrosting system according to one of claims 1 to 4, characterized in that the evaporator lines ( 4.1 ) and the defrosting lines ( 4.2 ) alternately and alternately in the evaporator ( 4 ), wherein in each case a defrosting line ( 4.2 ) and an adjacent evaporator line ( 4.1 ) a section of the evaporator ( 4 ) or a section of the evaporator ( 4 ) form. Defrosting system according to one of claims 1 to 5, characterized in that in each case an evaporator line ( 4.1 ) and a defrosting line ( 4.2 ) of the evaporator ( 4 ) together in a coaxial line designed as a combination line ( 4.3 ), wherein in the annular gap of the coaxial line, the refrigerant located on the condenser pressure and in the inner tube is the refrigerant located on the evaporator pressure. Defrosting system according to claim 5 or 6, characterized in that each section of the evaporator ( 4 ) each having a hinged cover or a single movable, strip-like hinged cover for all sections of the evaporator ( 4 ) is provided jointly. Defrost system according to claim 7, characterized in that the hinged cover and the shut-off valve ( 8th ) the defrosting line ( 4.2 ) of a section of the evaporator ( 4 ) are coupled together using a central control and regulating device such that the hinged cover and the shut-off valve ( 8th ) are mutually in the open and closed state. Defrosting system according to one of claims 1 to 8, characterized in that each section of the evaporator ( 4 ) the total defrosting capacity as well as the evaporator capacity corresponding to this section is available. Defrosting system according to one of claims 1 to 9, characterized in that between the individual sections of the evaporator ( 4 ) parallel to the defrosting lines ( 4.2 ) extending separation elements, for example dividing plates, are provided which allow an air-side heat exchange between the sections of the evaporator (FIG. 4 ) prevent. Method for operating the defrosting system using the device features of the defrosting system according to claims 1 to 3, characterized in that during the cooling or heat pump operation, the partial defrosting of the evaporator ( 4 ) starting from a closed flow path of the bypass line ( 7.1 ) comprises the following method steps: a. at least partially releasing the flow path of the bypass ( 7.1 ) using the designed as a 2-way valve distribution point ( 14 b. Opening the shut-off valve ( 8th ) a defrosting line ( 4.2 ) of the evaporator ( 4 ) and closing the other shut-off valves ( 8th ) of the evaporator ( 4 c. after defrosting a section of the evaporator, repeating the method step of method step b. for all other defrosting lines ( 4.2 ) and evaporator lines ( 4.1 ) of the evaporator ( 4 ) in chronological order and d. Closing the flow path of the bypass ( 7.1 ) using the designed as a 2-way valve distribution point ( 14 ). A method according to claim 11, characterized in that the partial defrosting of the evaporator ( 4 ) without interrupting the cooling or heat pump operation a. with complete release of the flow path of the bypass ( 7.1 ) and b. upon complete closure of the flow path of the loop ( 7.2 ) using the designed as a 2-way valve distribution point ( 14 ) he follows. Method according to claim 11 or 12, characterized in that the simultaneous defrosting of all sections of the evaporator ( 4 ) by simultaneously opening all shut-off valves ( 8th ) the defrosting line ( 4.2 ) of the evaporator ( 4 ) he follows.