DE202022105684U1 - Dry expansion evaporator for ammonia chillers - Google Patents

Abstract

Dry expansion evaporator (1) for ammonia refrigeration systems with a collector pipe (2) and an outlet pipe (3) for the refrigerant gas, characterized in that the collector pipe (2) and the outlet pipe (3) are connected to one another via a siphon (5) and that the siphon (5) is arranged on the evaporator bottom (4) at the lowest point of the dry expansion evaporator (1).

Description

The invention relates to a dry expansion evaporator for ammonia refrigeration systems.

Generic dry expansion evaporators are used, for example, in refrigeration and cooling systems in warehouses, cold stores and for air conditioning.

Ammonia refrigeration systems are increasingly being used again in industry, trade and commerce. Ammonia as a refrigerant is referred to as R717, is a natural refrigerant and has no direct greenhouse effect (GWP) and also no ozone depletion potential (ODP). Various efforts are therefore being made to replace climate-damaging CFC refrigerants in order to increasingly use ammonia as a refrigerant again.

However, in order to ensure efficient operation of the ammonia refrigerating plants, so-called flooded evaporators are used in the ammonia refrigerating plants. The flooded operation of the evaporators leads to large amounts of refrigerant and also to a large amount of space required for the liquid separator after the evaporator.

Due to the toxic properties of ammonia and the technical requirements mentioned, more efforts are being made to reduce the capacity of the systems. This is possible, for example, when the ammonia refrigeration systems are operated in so-called dry expansion operation.

In the dry expansion operating mode, the evaporator of the ammonia refrigeration system is constantly flowed through by the 2-phase mixture of the refrigerant. The refrigerant is completely vaporized in the evaporator of the refrigeration system. The gaseous, dry refrigerant is then sucked in by the compressor and, after compression, circulated further.

In ammonia refrigeration systems, refrigeration machine oil is added to the refrigerant with the aim of lubricating moving machine parts of the compressor and sealing the pressure-building areas within the compressor. Furthermore, the heat generated in the lubricating gap is dissipated by the refrigeration machine oil. In order to ensure low-friction operation of the compressor, the refrigeration machine oil must be constantly supplied to the compressor in the appropriate dosage and kept in circulation.

Furthermore, in order to defrost icy evaporators in ammonia refrigeration systems, a hot gas defrost for heating and ice melting of the evaporator in refrigerant-air refrigeration systems is used by reverse operation of the refrigeration system. To make matters worse, refrigerant condenses in the evaporator and liquid condensate can collect in the evaporator.

However, in particular when using the so-called hot gas defrosting in the prior art, the disadvantage is known, as mentioned, that condensate forms in the evaporator, which condensate accumulates in the lower part of the evaporator and remains there. This is derived in particular from the design of the collector with a raised suction connection of the evaporator, which means that the iced-up evaporator can sometimes only be defrosted insufficiently.

Another disadvantage is that the refrigerant ammonia mixes relatively poorly with the refrigerator oil.

In dry expansion operation of the ammonia refrigeration system, almost miscible oil is added to the ammonia refrigerant. The oil settles in the present gas phase of the ammonia in the components of the refrigeration system at the respective lowest points.

Thus, in ammonia refrigeration systems, this effect leads to the risk of refrigeration machine oil accumulating at the evaporator outlet in the lowest rows of tubes. Due to the risk of liquid hammer, the accumulation of refrigeration machine oil in certain areas of the system should be reduced and the affected components should be de-oiled. If this aspect is neglected, a build-up of refrigeration machine oil in the evaporator can result in a surge of the liquid mixture being sucked in by the compressor. This creates the risk of the compressor room being flooded with oil, which can lead to the destruction of the compressor due to liquid hammer.

The object of the invention is to design an evaporator for ammonia refrigeration systems for dry expansion operation in such a way that the risk of liquid hammer for the compressor is reduced.

The object is achieved by an object with the features according to claim 1 protection. Further developments are specified in the dependent claims.

The object of the invention is achieved in particular by a dry expansion evaporator for ammonia refrigeration systems, which in addition to the usual components of evaporators at least with a collector pipe and an outlet pipe for the refrigerant gas is equipped. According to the invention, the collector pipe and the outlet pipe are connected to one another via a siphon. The siphon is located on the bottom of the evaporator at the lowest point of the dry expansion evaporator.

A siphon is generally an odour-tight or gas-tight but liquid-permeable closure of pipe systems and vessels. The functional principle is based on an S-shaped tube, the lower bend of which always remains filled with liquid, thus preventing the passage of gases, such as sewer gases.

The siphon is preferably designed as a flat, cylindrical and upright container which has a flat, closed siphon bottom as the lower boundary. The side surface is formed by a circular-cylindrical siphon casing. The siphon cover closes the siphon at the top. Recesses are arranged in the siphon cover, the vertical header pipe and the vertical insertion end of the outlet pipe, which penetrate the siphon cover from above.

Advantageously, the outlet pipe essentially consists of three areas, viewed against the direction of flow, of a horizontal section with a connection to the suction port of the compressor, an adjoining bend and a vertical section. The vertical section has an insertion end which is beveled. With the insertion end, the outlet pipe is inserted into the siphon up to the bottom of the siphon.

The insertion end of the outlet pipe in the siphon is preferably designed as a baffle plate.

The refrigerant evaporator tubes are integrated into the collector tube above the siphon so that the siphon forms the lowest point of the evaporator. The embodiment of the invention is particularly preferably designed as a ceiling evaporator with an output of 70 kW.

• Die Absaugung und Entölung des angestauten Kältemittels erfolgt am tiefsten Punkt des Verdampfers der Kälteanlage über einen Siphon, so dass eine größere Ansammlung von Kondensat und Kältemaschinenöl nicht entstehen kann. Der Siphon ist auf kleinstem Raum und sehr platzsparend im Vergleich zu herkömmlichen Abscheidern bei überfluteten Verdampfern ausgeführt. Der Siphon ist am unteren Ende des Kältemittelsammlers unterhalb der letzten Rohrreihe angeordnet und stellt somit den tiefsten Punkt des Verdampfers da, in dem sich das Kältemittel und das Kältemaschinenöl sammelt. Konstruktionsgemäß läuft Flüssigkeit im Verdampfer schwerkraftgetrieben bis zu diesem Punkt.

The concept of the invention can be summarized as follows:

• The suction and de-oiling of the accumulated refrigerant takes place at the lowest point of the evaporator of the refrigeration system via a siphon, so that a large accumulation of condensate and refrigeration machine oil cannot occur. The siphon takes up very little space and is very space-saving compared to conventional separators for flooded evaporators. The siphon is located at the lower end of the refrigerant collector below the last row of pipes and is therefore the lowest point of the evaporator where the refrigerant and the refrigeration machine oil collect. By design, liquid in the evaporator travels to this point by gravity.

The suction nozzle is beveled and is inserted vertically into the siphon from above and guided to the bottom of the siphon. The inserted nozzle side is beveled in order to achieve a supporting effect on the suction of the refrigerant and the refrigeration machine oil through the surface tension between the pipe and the oil. The inserted pipe also acts as a baffle plate, which enables the gaseous refrigerant to be extracted from the evaporator with low pressure loss.

The advantages of the invention are manifold. In this way, the refrigerant and refrigeration machine oil can be completely extracted from the evaporator via the siphon. The defrosting times for an iced evaporator are greatly reduced because the evaporator is completely drained of liquid and the hot gas defrosting can take effect immediately. Furthermore, a temporary accumulation of oil in the evaporator is avoided and instead a continuous oil extraction and thus a constant oil supply to the compressor is ensured. This protects the compressor against surges of oil intake and flooding of the compressor room.

• 1: Seitenansicht Teilbereich Trockenexpansionsverdampfer,
• 2: Perspektivansicht Siphon mit Sammlerrohr und Austrittsrohr und
• 3: Seitenansicht des Siphons.

Further details, features and advantages of embodiments of the invention result from the following description of exemplary embodiments with reference to the associated drawings. Show it:

• 1 : Side view of the dry expansion evaporator section,
• 2 : Perspective view of siphon with collector pipe and outlet pipe and
• 3 : Side view of the siphon.

In 1 a dry expansion evaporator 1 of an ammonia refrigeration system is shown in part in the area of the evaporator bottom 4 . The dry expansion evaporator 1 is characterized in that the collector pipe 2 for the exiting refrigerant gas and the outlet pipe 3 for the connection to the intake port of the compressor of the refrigeration system are fluidically connected to one another via a siphon 5 . The refrigerant gas flows from the collector tube 2 via the siphon 5 into the outlet tube 3 and is then sucked in by the compressor of the refrigeration system. Liquid refrigerant, or condensate, as well as liquid refrigeration machine oil runs in the gravity driven Collector tube 2 down into the siphon 5 and is continuously entrained by the gas flow.

The siphon 5 is arranged at the lowest point of the dry expansion evaporator 1 in order to be able to continuously suck the refrigerant oil and liquid refrigerant that settles out of the evaporator during operation. This ensures that no accumulations of liquid can form in the dry expansion evaporator 1 .

In 2 the siphon 5 is shown as a component of the dry expansion evaporator 1 in a perspective view. The collector tube 2 is arranged vertically and ends in the siphon 5 , so that any condensate that may form from the refrigerant and refrigerant oil collect in the siphon 5 . The outlet pipe 3 for the refrigerant vapor is arranged upwards out of the siphon 5, via which the refrigerant-oil mixture leaves the dry expansion evaporator 1 to the intake port of the compressor of the refrigeration system.

Refrigerant evaporator tubes 6 are shown as an example, which are arranged vertically and open into the collector tube 2 . The lowest refrigerant evaporator tubes 6 are arranged above the entrance of the collector tube 2 into the siphon 5 .

In the perspective view, the siphon 5 is shown as a flat, cylindrical container with a diameter that is the sum of the diameters of the collector pipe 2 and the outlet pipe 3.

In 3 the siphon 5 is shown as a detail and enlarged in the side view.

The siphon 5 consists of a circular-cylindrical siphon jacket 10, the flat siphon base 9 and the perforated siphon cover 11. The vertical part of the outlet pipe 3 is beveled below and inserted into the siphon 5 from above and guided to the siphon base 9. The lowest refrigerant evaporator pipe 6 is introduced into the collector pipe 2 above the siphon 5 , so that the entire refrigerant volume flow is passed through the siphon 5 . The refrigerant volume flow undergoes a deflection of 180° from the entry into the siphon 5 from the collector pipe 2 to the exit from the siphon 5 through the insertion end 7 of the outlet pipe 3. The refrigerant flow undergoes a further deflection in the area of the elbow 8 by 90° and leaves in a horizontal direction Direction the outlet pipe 3 in the direction of the compressor, not shown.

reference list

1

dry expansion evaporator

2

collector tube

3

outlet pipe

4

evaporator bottom

5

siphon

6

refrigerant evaporator tube

7

Plug-in outlet pipe

8th

manifold

9

siphon bottom

10

siphon jacket

11

siphon cover

Claims (6)

Dry expansion evaporator (1) for ammonia refrigeration systems with a collector pipe (2) and an outlet pipe (3) for the refrigerant gas, characterized in that the collector pipe (2) and the outlet pipe (3) are connected to one another via a siphon (5) and that the siphon (5) is arranged on the evaporator bottom (4) at the lowest point of the dry expansion evaporator (1). Dry expansion evaporator (1) after claim 1 , characterized in that the siphon (5) is designed as a flat, cylindrical, upright container which has a closed siphon bottom (9) at the bottom and an inlet for the vertical collector pipe (2) and the vertical insertion end (7) of the outlet pipe (3 ) having. Dry expansion evaporator (1) after claim 1 or 2 , characterized in that the outlet pipe (3) is formed from a horizontal section, an elbow (8) and a vertical section, the vertical section as the insertion end (7) of the outlet pipe (3) being slanted and extending down to the siphon bottom ( 9) is inserted into the siphon (5). Dry expansion evaporator (1) according to one of Claims 1 until 3 , characterized in that the insertion end (7) of the outlet pipe (3) forms a baffle plate area in the siphon (5). Dry expansion evaporator (1) according to one of Claims 1 until 4 , characterized in that refrigerant evaporator tubes (6) are integrated into the collector tube (2) above the siphon (5). Dry expansion evaporator (1) according to one of Claims 1 until 5 , characterized in that the dry expansion evaporator (1) is designed as a ceiling evaporator with an output of 70 kW.

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