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Freon chain oil

The oil in the freon system is necessary for lubricating the compressor. It constantly leaves the compressor - circulates in the freon circuit along with Freon. If for any reason the oil will not return to the compressor, the KM will not be linked enough. The oil dissolves in a liquid fraon, but not dissolved in a vapor-shaped. On pipelines moves:

• after the compressor - overheated pairs of freon + oil fog;
• after the evaporator - overheated pairs of freon + oil film on the walls and oil in a dropway form;
• after the condenser - liquid freon with oil dissolved in it.

Therefore, on steam lines there may be a problem of oil delay. It can decide to comply with sufficient velocity of the steam movement in the pipelines, the necessary slope of the pipes, the installation of oil liners.

The evaporator is below.

a) oil-leaf loops must be located on the interval every 6 meters on the upstream pipelines to facilitate the return of oil into the compressor;

b) make a collecting pit on the suction line after TRV;

The evaporator is higher.

a) At the exit from the evaporator, install the hydrotheking above the evaporator to prevent the liquid drainage into the compressor during the parking lot.

b) Make a collecting veil on the suction line after the evaporator for collecting a liquid refrigerant, which can accumulate during the parking lot. When the compressor turns on the refrigerant, the refrigerant will quickly evaporate: it is advisable to make a veil into the distance from the sensing element of the TRV to avoid the impact of this phenomenon on the work of the TRV.

c) on horizontal sections of the injection pipeline a slope of 1% in the course of the movement of freon to facilitate oil movement in the right direction.

Condenser below.

No special precautions in this situation should be taken.

If the condenser is lower than kib, then the height of the lift should not exceed 5 meters. However, if kib and the system in general is not better qualityThe liquid freon may experience difficulties in the rise and with smaller height differences.

a) It is advisable to set the shut-off valve at the capacitor inlet nozzle to exclude the flow of liquid freon into the compressor after disconnecting the refrigeration machine. This can occur if the condenser is located in the ambient temperature above the temperature of the compressor.

b) on horizontal sections of the injection pipeline slope of 1% in the course of the movement of freon to facilitate the movement of oil in the right direction

Condenser above.

a) To eliminate the flow of liquid chladka from the CD in km when the refrigeration machine is stopped, install the valve before the CD.

b) the oil loops must be located on the interval every 6 meters on the upstream pipelines, to facilitate the return of oil into the compressor;

c) on horizontal sections of the injection pipeline, a slope of 1% to facilitate oil movement in the right direction.

The work of the oil loop.

When the oil level reaches the upper wall of the tube, the oil will push further towards the compressor.

Calculation of freon pipelines.

The oil dissolves in liquid freon, so you can maintain the speed in the liquid pipelines small - 0.15-0.5 m / s, which will provide small hydraulic resistance to the movement. An increase in resistance leads to a loss of cooling capacity.

The oil does not dissolve in a vapor-shaped freon, so it is necessary to maintain speed in steam pipelines significant so that the oil is transferred to the ferry. When moving, part of the oil covers the walls of the pipeline - this film is also moved by a steam of high speed. Speed \u200b\u200bon the discharge side of the compressor 10-18m / s. Speed \u200b\u200bon the compressor suction side 8-15m / s.

On horizontal sections of very long pipelines, it is allowed to reduce the speed to 6m / s.

Example:

Initial data:

Refrigerant R410A.
Required cooling capacity 50kW \u003d 50KJ / s
Boiling point 5 ° C, condensation temperature 40 ° С
Overheating 10 ° С, hypothermia 0 ° С

Solution for suction pipeline:

1. The specific processivity of the evaporator is equal Q.and \u003d n1-n4 \u003d 440-270 \u003d 170kj / kg

2. Freon Mass Consumption

m.\u003d 50kW / 170KJ / kg \u003d 0.289kg / s

3. Specific volume of vapor freon on the suction side

V.sun \u003d 1 / 33.67kg / m³ \u003d 0.0297m³ / kg

4. Various frequency freak consumption on the suction side

Q.= V.sun * m.

Q.\u003d 0.0297m³ / kg x 0,289kg / s \u003d 0.00858m³ / s

5. Increased diameter of the pipeline

From standard copper freon pipelines, choose a pipe with an outer diameter of 41.27mm (1 5/8 "), or 34.92mm (1 3/8").

Outer The diameter of pipelines is often selected in accordance with the tables given in the "Installation Instructions". In the preparation of such tables, the steam movement velocities are taken into account.

Calculation of the volume of Freon refueling

The calculation of the mass of refrigerant refueling is simplified by the formula that takes into account the volume of liquid highways. This simple formula steam highways are not taken into account because the volume occupied by the ferry is very small:

Music = P.ha. * (0.4 x V.iS +. TOg * V.res +. V.j.M.), kg,

P.ha. - the density of the saturated liquid (freon) PR410A \u003d 1.15 kg / dm³ (at a temperature of 5 ° C);

V.δ - the internal volume of the air cooler (air coolers), dm³;

V.res - the internal volume of the receiver refrigeration unit, dm³;

V.j.M.- Internal volume of liquid highways, dm³;

TOg - coefficient taking into account the circuit of the condenser installation:

TOg \u003d 0.3 for compressor capacitor units without hydraulic condensation pressure regulator;
TOg \u003d 0.4 When using a hydraulic condensation pressure regulator (installation of an aggregate on the street or execution with a remote condenser).

Akayev Konstantin Evgenievich
Candidate of Technical Sciences St. Petersburg University of Food and Low Temperature Technologies

Today there are VRF-systems of original Japanese, Korean and Chinese brands in the market. Even more VRF systems of numerous OEM manufacturers. Externally, they are all very similar, and the false impression is that all VRF systems are the same. But "not all yogurts are equally useful", as stated in popular advertising. We continue the series of articles aimed at studying the technologies of obtaining cold, which are used in the modern class of air conditioners - VRF-systems.

Designs of separators (oil separators)

Oil in oil separators is separated from the gaseous refrigerant as a result of a sharp change in direction and reduce the speed of the steam movement (up to 0.7-1.0 m / s). The direction of movement of the refrigerant of the refrigerant varies with the help of partitions or in a certain way of installed pipes. In this case, the oil separator catches only 40-60% oil carried out from the compressor. Therefore, the best results give a centrifugal or cyclone oil separator (Fig. 2). The gaseous refrigerant entering the pipe 1, falling on the guide blades 3, acquires rotary traffic. Under the action of centrifugal power, the oil drops are discarded on the body and form a slow-flowing film. The refrigerant gaseous when leaving the spiral changes dramatically changes its direction and on the nozzle 2 leaves the oil separator. Separated oil is separated from the gas jet with partition 4 to prevent the secondary grip of the oil with a refrigerant.

Despite the work of the separator, a small part of the oil is still worn with freon into the system and gradually accumulates there. A special oil return mode is applied to return. The essence of it is as follows. The outdoor unit is activated in cooling mode for maximum performance. All EEV valves in the inner blocks are fully open. But the fans of the internal blocks are turned off, so the freon in the liquid phase passes through the heat exchanger of the indoor unit without boss. Liquid oil in internal block, washed off with liquid freon in gas pipeline. And then returns to outdoor block With gaseous freon at maximum speed.

Type of refrigeration oil

The type of refrigeration oil used in refrigeration systems For lubrication of compressors, depends on the type of compressor, its performance, but most importantly - from the freon used. Oils for the refrigeration cycle are classified as mineral and synthetic.

Mineral oil is mainly used with CFC (R12) and HCFC (R22) refrigerants and is based on naphthene or paraffin, or a mixture of paraffin and acrylbenzene. HFC refrigerants (R410A, R407C) are not dissolved in mineral oil, so synthetic oil is used for them.

Heater Carter

Refrigeration oil is mixed with a refrigerant and circulates with it throughout the entire cooling cycle. The oil in the compressor crankcase contains a certain amount of dissolved refrigerant, and the liquid refrigerant in the condenser contains a small amount of dissolved oil. The lack of the latest use is the formation of foam. If a refrigerator It turns off for a long period and the oil temperature in the compressor is lower than in the inner circuit, the refrigerant is condensed and most of it dissolves in oil. If the compressor is started in this state, the pressure in the crankcase drops and the dissolved refrigerant evaporates with the oil, forming an oil foam. This process is called "foaming", it leads to the outlet of the oil from the compressor on the discharge nozzle and the deterioration of the compressor lubrication. To prevent foaming on the VRF system compressor crankcase, a heater has a heater so that the compressor crankcase temperature is always slightly higher than the ambient temperature (Fig. 3).

The effect of impurities on the work of the refrigeration circuit

1. Technological oil (machine, oil for assembly). If the system using HFC refrigerant will get technological oil (for example, machine), then such an oil will be separated, forming flakes and causing the capillary tubes.
2. Water. If the cooling system that uses the HFC refrigerant is water, the acidity of the oil increases, the destruction of polymer materials used in the compressor engine occurs. This leads to the destruction and breakdowns of the exclusion of the electric motor, clogging capillary tubes, etc.
3. Mechanical trash and dirt. Arriving problems: clogging filters, capillary tubes. Decomposition and separation of oil. The destruction of the insulation of the compressor electric motor.
4. Air. The consequence of a large amount of air (for example, the system was refueling without vacuuming): anomalous pressure, an increased acidity of oil, a compressor insulation test.
5. impurities of other refrigerants. If a large number of refrigerants fall into the cooling system of different typesThere is an abnormal working pressure and temperature. The consequence of this is damage to the system.
6. impurities of other refrigeration oils. Many refrigeration oils are not mixed with each other and fall into the sediment in the form of flakes. Flakes are clogged with filters and capillary tubes, reducing freon consumption in the system, which leads to overheating of the compressor.

The following situation is repeatedly found associated with the oil return mode to the compressors of external blocks. The VRF-air conditioning system is mounted (Fig. 4). Refueling system, work parameters, pipeline configuration - everything is normal. The only nuance is part of the internal blocks is not mounted, but the loading coefficient of the outer block is permissible - 80%. Nevertheless, compressors are regularly issued due to jamming. What is the reason?

And the reason is simple: the fact is that branches were prepared for mounting the missing internal blocks. These branches were dead-up "appendixes", into which the oil circulating with Freon got into, but it could not come back and then accumulated there. Therefore, compressors were out of order due to the usual "oil starvation". That this does not happen, on branches as close as possible to splitters it was necessary to put locking valves. Then the oil would freely circulate in the system and returned in the oil collection mode.

Melted loops

For VRF-systems of Japanese manufacturers there are no requirements for the installation of oil loops. It is believed that separators and oil return mode effectively return the oil into the compressor. However, there is no rules without exceptions - on MDV systems V5 series, it is recommended to install oil loops if the outer block is above the internal and the height difference of more than 20 m (Fig. 5).

The physical meaning of the oil loop is reduced to the accumulation of oil before vertical lifting. The oil accumulates at the bottom of the pipe and gradually overlaps the hole for freon skip. Freon gaseous increases its velocity in the free section of the pipeline, capturing the accumulated liquid oil.

With full overlap of the cross section of the pipe oil, Freon pushes this oil as a plug before the next oil loop.

Output

Oil separators are the most important and mandatory element of the high-quality VRF system of air conditioning. Only thanks to the return of freon oil back to the compressor is achieved reliable and trouble-free operation of the VRF system. Most optimal option Constructions - when each compressor is equipped with a separate separator, since only in this case the uniform distribution of freon oil in multicompressor systems is achieved.

In the process of acceptance testing, once again, it is necessary to deal with errors made in designing and installing copper pipelines for freon air conditioning systems. Using the accumulated experience, and based on the requirements regulatory documentsWe tried to combine the basic rules for the organization of the highways of copper pipelines under this article.

It will be about the organization of the tracks, and not about the rules for mounting copper pipelines. Issues of placing pipes, their mutual location, the problem of selecting the diameter of freon pipelines, the need for oil lubricants, compensators, etc. We will bypass the rule of the installation of a specific pipeline, the technology of compounds and other parts. At the same time, issues of larger and general views on the device of copper trails will be affected, some practical problems are considered.

Mainly this material Regards freon air conditioning systems, whether traditional split systems, multizone air conditioning systems or precision air conditioners. At the same time, we will not touch the installation of water pipes in cheiller systems and installation of relatively short freon pipelines inside refrigeration machines.

Regulatory documentation for the design and installation of copper pipelines

Among regulatory documentationconcerning the installation of copper pipelines, highlight the following two standards:

• One hundred Nostroy 2.23.1-2011 "Installation and commissioning of evaporative and compressor-condenser blocks of household air conditioning systems in buildings and structures";
• SP 40-108-2004 "Design and Installation internal systems Water supply and heating of copper pipe buildings. "

The first document describes the features of the installation of copper pipes in relation to the air-conditioning air-conditioning systems, and the second - applied to heating and water supply systems, but many of them are applicable for air conditioning systems.

Selection of diameters of copper pipelines

The selection of the diameter of copper pipes is carried out on the basis of directories and equipment for calculating air conditioning equipment. In split-systems, the diameter of the pipes are selected according to the connecting nozzles of the internal and external blocks. In the case of multizone systems, the calculation programs are correct. IN precision air conditioners The manufacturer's recommendations are used. However, with a long freon highway, non-standard situations that are not specified in the technical documentation may occur.

In general, to ensure the return of oil from the contour to the compressor crankcase and acceptable pressure losses, the flow rate in the gas highway must be at least 4 meters per second for horizontal sites and at least 6 meters per second for ascending sites. In order to avoid occurrence of unacceptable high level Noise The maximum permissible gas flow rate is limited to 15 meters per second.

The rate of refrigerant flow in the liquid phase is significantly lower and is limited by the potential destruction of the valve-adjusting reinforcement. The maximum speed of the liquid phase is not more than 1.2 meters per second.

At high rains with long trails, the inner diameter of the liquid highway should be chosen so that the pressure drop in it and the pressure of the fluid column (in the case of an uptren pipeline) did not lead to the boiling of the fluid at the end of the line.

In precision air conditioning systems, where the length of the track can achieve and exceed 50 meters, the vertical areas of the gas lines of the low diameter are often taken, as a rule, one size (per 1/8 ").

We also note that often the calculated equivalent length of pipelines exceeds the limit specified by the manufacturer. In this case, it is recommended to agree on the actual route with the air conditioner manufacturer. It is usually it turns out that the length of length is permissible for magnitude up to 50% maximum length Trails specified in catalogs. In this case, the manufacturer specifies the necessary diameters of the pipelines and the percentage of increasing cooling capacity. According to the experiment, the understatement does not exceed 10% and does not have a decisive value.

Oil liner

The oil lubs are installed in the presence of vertical sections of 3 meters long and more. At higher loops, it should be installed every 3.5 meters. At the same time, the top point is installed in the top cover of the loop.

But there are exceptions here. When negotiating a non-standard route, the manufacturer can recommend to establish an additional oil lining and refuse unnecessary. In particular, in the conditions of a long route in order to optimize the hydraulic resistance, a refusal from the reverse loop was recommended. In another project, due to specific conditions on the rise of about 3.5 meters, they ordered two hinges.

The oil lined loop is an additional hydraulic resistance and should be taken into account when calculating the equivalent length of the route.

In the manufacture of the oil lucid loop, it should be borne in mind that its dimensions should be as small as possible. The loop length should not exceed 8 diameters of the copper pipeline.

Fastening copper pipelines

Fig. 1. Scheme of fastening pipelines in one of the projects,
from which the mount of the clamp directly to the pipe
It is not obvious that it became the subject of disputes

In terms of fastening copper pipelines, the most common error is the fastening of the clamps through isolation, allegedly to reduce the vibration effect on the fasteners. The controversial situations in this matter can be caused and not enough for a detailed drawing of the sketch in the project (Fig. 1).

In fact, metal plumbing clamps consisting of two parts twisted with screws and having rubber sealing inserts should be used for fastening pipes. They will provide the necessary breeding of vibrations. The clamps must be attached to the pipe, and not to isolation, should have the appropriate size and ensure the rigid fastening of the track to the surface (wall, ceiling).

The choice of distances between the fasteners of pipelines from solid copper pipes is generally calculated according to the procedure presented in the application of the document SP 40-108-2004. This method should be resorted in the case of using non-standard pipelines or in the case of controversial situations. In practice, more often use specific recommendations.

Thus, the recommendations on the distance between the supports of the copper pipelines are shown in Table. 1. The distance between the fasteners of horizontal pipelines of semi-solid and soft pipes is permissible to take less than 10 and 20%, respectively. If necessary, more accurate values \u200b\u200bof distances between the attachments on horizontal pipelines should be determined by the calculation. At least one mount should be installed on the riser, regardless of the height of the floor.

Table 1 Distance between the supports of copper pipelines

Note that the data from the table. 1 approximately coincide with the schedule shown in Fig. 1 p. 3.5.1 SP 40-108-2004. However, we adapted the data of this standard under the pipelines used in air conditioning systems relative to a small diameter.

Temperature expansion compensators

A question that often puts in the deadlock of engineers and installers is the need to install temperature expansion compensators, choosing their type.

The refrigerant in air conditioning systems in general has a temperature in the range from 5 to 75 ° C (more accurate values \u200b\u200bdepend on the elements of the refrigeration circuit under consideration). The ambient temperature changes in the range from -35 to +35 ° C. Specific estimated temperature differences are made depending on where the pipeline in question is located in a room or on the street, and between which elements of the refrigeration circuit (for example, the temperature between the compressor and the condenser is in the range from 50 to 75 ° C, and between the TRV and the evaporator - ranging from 5 to 15 ° C).

Traditionally, the construction uses P-shaped and M-shaped compensators. Calculation of the compensating ability of P-shaped and M-shaped elements of pipelines is made by the formula (see the scheme in Figure 2)

where
L K - departure of the compensator, m;
L is the linear deformation of the pipeline section when the air temperature changes during installation and operation, m;
A - coefficient of elasticity of copper pipes, A \u003d 33..

Linear deformation is determined by the formula

L is the length of the deformable section of the pipeline at the installation temperature, m;
T is the temperature difference between the temperature of the pipeline in various modes during operation, ° C;
- The coefficient of linear copper expansion equal to 16.6 · 10 -6 1 / ° C.

For example, we calculate the necessary free distance l to from the movable pipeline support D \u003d 28 mm (0.028 m) to rotation, the so-called departure of the M-shaped compensator at a distance to the nearest stationary support L \u003d 10 m. The pipe area is located indoors (pipeline temperature non-working chiller 25 ° C) between the refrigeration machine and the remote capacitor (the operating temperature of the pipeline is 70 ° C), that is, T \u003d 70-25 \u003d 45 ° C.

By the formula we find:

L \u003d · L · T \u003d 16.6 · 10 -6 · 10 · 45 \u003d 0.0075 m.

Thus, the distances of 500 mm are quite enough to compensate for the temperature extensions of the copper pipeline. Once again we emphasize that L is the distance to the stationary support of the pipeline, L to - the distance to the movable support of the pipeline.

In the absence of turns and use of the P-shaped compensator, we obtain that for every 10 meters the direct portion requires a half-meter compensator. If the width of the corridor or other geometric characteristics of the pipeline laying is not allowed to arrange a compensator with a departure of 500 mm, compensators should be set more often. At the same time, dependence, as can be seen from the formula, quadratic. With a decrease in the distance between compensators, 4 times the departure of the compensator will be shorter than just 2 times.

To quickly determine the departure of the compensator, it is convenient to use Table. 2.

Table 2. Departure of the compensator L to (mm) depending on the diameter and extension of the pipeline

Finally, we note that only one fixed support should be between the two compensators.

Potential places where compensators may be required, of course, those where the highest temperature difference between the working and non-working modes of the air conditioner is observed. Since the hottest refrigerant flows between the compressor and the condenser, and the most low temperature It is characteristic of outdoor sections in winter, the external areas of pipelines in chiller systems with remote capacitors are most critical, and in precision air conditioning systems - when using internal closet air conditioners and a remote capacitor.

Such a situation has developed on one of the objects where remote capacitors I had to install on the frame 8 meters from the building. At such a distance, with a temperature drop in excess of 100 ° C, there was only one removal and rigid fastening of the pipeline. Over time, the pipe bending appeared in one of the attachments, after half a year after entering the system, leakage appeared. Three systems mounted in parallel to each other had the same defect and demanded an emergency repair with a change in the configuration of the track, the introduction of compensators, re-crimping and looping the contour.

Finally, another factor that should be taken into account when calculating and designing compensators of temperature expansion, especially P-shaped, is a significant increase in the equivalent length of the freon contour due to the additional length of the pipeline and four taps. If the total length of the track reaches critical values \u200b\u200b(and if we are talking about the need to use compensators, the length of the track is obviously rather big), then coordinate with the manufacturer follows the final scheme with the indication of all compensators. In some cases, joint efforts can work out the most optimal solution.

The routes of air conditioning systems should be laid hidden in furrows, channels and mines, trays and on the suspension, and with a hidden gasket, access to detachable connections and fittings should be provided by device and removable shields, on the surface of which there should be no sharp protrusions. Also, with a hidden laying of pipelines in places of collapsible compounds and reinforcements, it is necessary to provide service hatches or removable shields.

Vertical sites should be deposited only in exceptional cases. Mostly it is advisable to stir in the canals, niches, furrows, as well as for decorative panels.

In any case, the hidden laying of copper pipelines should be carried out in the casing (for example, in corrugated polyethylene pipesoh). The use of corrugated pipes from PVC is not allowed. Prior to sealing places of pipeline laying, it is necessary to perform an actuating scheme for the installation of this section and conduct hydraulic tests.

An open laying of copper pipes is allowed in places that exclude their mechanical damage. Open areas can be covered with decorative elements.

The laying of pipelines through the walls without sleeves, I must say, it is practically not necessary to observe. Nevertheless, we recall that for the passage through building structures it is necessary to provide for sleeves (cases), such as polyethylene pipes. The inner diameter of the sleeve must be 5-10 mm more than the outer diameter of the pipe paved. The clearance between the pipe and the case is necessary to close up with a soft waterproof material allowing the pipe moving along the longitudinal axis.

When installing copper pipes, use a specially intended tool - rolling, pipe bender, press.

A lot of useful information on the installation of freon pipelines can be obtained from experienced installation of air conditioning systems. It is especially important to transmit these information to designers, since one of the problems of the project industry is its conclusion from installation. As a result, the projects are difficult to solvely implemented in practice. As they say, the paper erased everything. It is easy to draw - do it difficult.

By the way, that is why all advanced training courses in the APIC training and consulting center are carried out by teachers who have experience in construction and installation work. Even for managerial and design specialties, teachers from the realization are invited to ensure complex perception of the industry by listeners.

So, one of the basic rules is to provide at the project level convenient for installation height of the gasket of freon routes. The ceiling is also recommended to withstand at least 200 mm. With the suspension of pipes on the studs, the most comfortable lengths of the latter - from 200 to 600 mm. With long-length studs, it is difficult to work. Studs of greater length are also inconvenient in installation and can sway.

When installing pipelines in the tray, you should not hang the tray to the ceiling closer than 200 mm. Moreover, it is recommended to leave about 400 mm from the tray to the ceiling for a comfortable pipe soldering.

Outdoor routes are most convenient to put it in trays. If the pitch allows, then in the trays with a lid. If not - the pipes are protected in a different way.

The constant problem of many objects is the lack of marking. One of the most common comments when working in the field of copyright or technical supervision is to march the cables and air conditioning system pipelines. For ease of operation and subsequent maintenance of the system, it is recommended to label cables and pipes every 5 meters of length, as well as before and after building structures. In the marking, use the system number, type of pipeline.

When installing various pipelines on each other on the same plane (wall), it is necessary to install below the one that is most likely the formation of condensate during operation. In case of parallel installation of each other of two gas lines various systemsThe following must be installed in which heavier gas flows.

Conclusion

When designing and installing large objects with multiple air conditioning systems and long tracks, special attention should be paid to the organization of freonopal routes. Such an approach to the development of the general pipe gasket policy will save time both at the design stage and in the installation phase. In addition, this approach avoids the mass of errors with which you have to meet in real construction: forgotten compensators of temperature expansion or compensators that do not fit in the corridor due to adjacent engineering systems, error schemes for fastening pipes, incorrect calculations of the equivalent pipeline length.

As the experience experience has shown, the accounting of these tips and recommendations really gives a positive effect at the device of the device of air conditioning systems, significantly reduces the number of issues during installation and the number of situations where it is emergency to find a solution to a complex problem.

Yuri Khomutsky, technical editor of the magazine "World of Climate"

Today there are at the marketVRF. - Systems of original Japanese, Korean and Chinese brands. Much moreVRF. -Systems numerousOEM. manufacturers. Externally they are all very similar and the false impression is that allVRF. - Systems are the same. But "not all yogurts are equally useful", as stated in popular advertising. We are starting a series of articles aimed at studying the technologies of obtaining cold, which are used in the modern class of air conditioners -VRF. - Systems. We have already considered the refrigerant hypothermation system and its effect on the characteristics of the air conditioner, various layouts of the compressor node. In this article we will explore -system of oil waste .

What is oil in the refrigeration circuit? For lubrication compressor. And there should be oil in the compressor. In a conventional split-system, the oil freely circulates together with freon and is evenly distributed throughout the refrigeration circuit. The VRF systems have a refrigeration outline too large, so the first problem with which manufacturers of VRF systems have collided, it is a decrease in the oil level in compressors and the failure of them due to "oil starvation".

There are two technologies with which the refrigeration oil returns back to the compressor. First - applied device oil separator (oil separator) in the outer block (in Figure 1). Oil separators are installed on the compressor discharge pipe between the compressor and the condenser. The oil is carried out from the compressor both in the form of small droplets and in a vapor state, since at temperatures from 80c to 110s there is a partial evaporation of oil. Most of Oil sedates in the separator and returns to a separate oil pipeline into the compressor crankcase. This device significantly improves the compressor lubrication mode and ultimately increases the reliability of the system. From the point of view of the design of the refrigeration circuit, there are systems at all without oil separators, systems with one oil separator for all compressors, systems with an oil separator on each compressor. Perfect option Uniform oil distribution This is when each compressor has a "its" separator of oil (Fig. 1).

Fig. one . Diagram of the refrigeration circuit VRF - systems with two freon oil separators.

Designs of separators (oil separators).

Oil in oil separators is separated from the gaseous refrigerant as a result of a sharp change in the direction and decrease in the speed of the steam movement (up to 0.7 - 1 m / s). The direction of movement of the gaseous refrigerant varies with partitions or certainly installed pipes. In this case, the oil separator catches only 40-60% oil carved from the compressor. Therefore, the best results give a centrifugal or cyclone oil separator (Fig. 2). The gaseous refrigerant flowing to the pipe 1, falling on the guide blades 4, acquires a rotational movement. Under the action of centrifugal power, the oil drops are discarded on the body and form slowly flowing down the film. The refrigerant gaseous when leaving the spiral changes dramatically and turns its direction from the nozzle 2 from the oil separator. Separated oil is separated from the gas jet by partition 5 to prevent the secondary grip of the oil with a refrigerant.

Fig. 2. Construction of the centrifugal oil separator.

Despite the work of the oil separator, a small part of the oil is still carved with freon into the system and gradually accumulates there. To return it, a special mode is applied, which is called oil return mode. The essence of it is as follows:

The outdoor unit is activated in cooling mode for maximum performance. All valveev in the inner blocks are fully open. But the fans of the internal blocks are turned off, so the freon in the liquid phase passes through the heat exchanger of the indoor unit without boss. Liquid oil in the inner block is washed off with liquid freon in the gas pipeline. And further returns to the outer block with gaseous freon at the maximum speed.

Type of refrigeration oilused in refrigeration systems for lubricating compressors depends on the type of compressor, its performance, but the main thing used by freon. Oils for the refrigeration cycle are classified as mineral and synthetic. Mineral oil is mainly used with CFC (R 12) and HCFC (R 22) refrigerants (R 22) and is based on naphthene or paraffin, or a mixture of paraffin and acrybenzene. HFC refrigerants (R 410A, R 407C) are not dissolved in mineral oil, therefore, synthetic oil is used for them.

Heater Carter. Refrigeration oil is mixed with a refrigerant and circulates with it throughout the entire cooling cycle. The oil in the compressor crankcase contains a certain amount of dissolved refrigerant, and the liquid refrigerant in the condenser contains a small amount of dissolved oil. The lack of using soluble oil is the formation of foam. If the refrigerator turns off for a long period and the oil temperature in the compressor is lower than in the inner contour, the refrigerant is condensed and most of it dissolves in oil. If in this state, the compressor starts, the pressure in the crankcase drops and the dissolved refrigerant evaporates along with the oil, forming an oil foam. This process is called foaming, it leads to the outlet of the oil from the compressor over the discharge nozzle and the deterioration of the compressor lubrication. To prevent foaming on the VRF compressor crankcase, a heater has a heater so that the compressor crankcase temperature is always slightly higher than the ambient temperature (Fig. 3).

Fig. 3. Compressor Card Heater

The effect of impurities on the work of the refrigeration circuit.

Technological oil (Machine oil, oil for assembly). If the system using HFC refrigerant will fall technological oil (for example, machine), then such an oil will be separated, forming flakes and causing a blockage of capillary tubes.

Water. If the cooling system that uses the HFC refrigerant is water, the acidity of the oil increases, the destruction of polymer materials used in the compressor engine occurs. This leads to the destruction and breakdowns of the exclusion of the electric motor, clogging capillary tubes, etc.

Mechanical trash and dirt. Arriving problems: clogging filters, capillary tubes. Decomposition and separation of oil. The destruction of the insulation of the compressor electric motor.

Air. The consequence of a large amount of air (for example, the system was refueling without vacuuming): anomalous pressure, an increased acidity of oil, a compressor insulation test.

Impurities of other refrigerants. If a large number of refrigerants of various types fall into the cooling system, an abnormal working pressure and temperature occurs. The consequence of which is damage to the system.

Impurities of other refrigeration oils.Many refrigeration oils are not mixed with each other and fall into the sediment in the form of flakes. Flakes are clogged with filter and capillary tubes, reducing freon consumption in the system, which leads to overheating of the compressor.

The following situation is repeatedly found associated with the oil return mode to the compressors of external blocks. The VRF is mounted - air conditioning (Fig. 4). Refueling system, work parameters, pipeline configuration - all normal. The only nuance is part of the internal blocks are not mounted, but the loading coefficient of the outdoor unit is permissible - 80%. Nevertheless, compressors are regularly issued due to jamming. What is the reason?

Fig. 4. Scheme of partial installation of internal blocks.

And the reason was simple: the fact is that branches were prepared for mounting the missing internal blocks. These branches were deadly "appendixes", into which the oil circulating together with Freon fell, but it could not come back to come back and accumulated. Therefore, the compressor was out of order due to the usual "oil starvation". That this does not happen, on branches as close as possible to splitters it was necessary to put locking valves. Then the oil would freely circulate in the system and returned in the oil collection mode.

Oil liner.

For VRF-Systems of Japanese manufacturers there are no requirements for the installation of oil liners. It is believed that separators and oil return mode effectively return the oil into the compressor. However, there is no rules without exception - on MDV systems of the V 5 series, it is recommended to install oil lines if the outer block is higher above the internal and the height difference more than 20 meters (Fig. 5).

Fig. 5. Scheme of the oil linguching loop.

For FreonaR. 410 A. Melted loops are recommended to put every 10-20 meters of vertical sections.

For freonR. 22 I.R. 407C oil lucked loops are recommended to be put in 5 meters of vertical sites.

The physical meaning of the oil liner is reduced to the accumulation of oil before the vertical lift. The oil accumulates at the bottom of the pipe and gradually overlaps the hole for freon skip. Gaseous Freon increases its velocity in the free cross section of the pipeline, capturing the liquid oil. With full overlap of the cross section of the pipe oil, Freon pushes the oil as a plug before the next oil luggage.

Output.

Oil separators are an essential and mandatory element of high-quality VRF-System of air conditioning. Only due to the return of freon oil back to the compressor reached a reliable and trouble-free operation of VRF-Systems. The most optimal design option, when each compressor is equipped with a separate separator, because Only in this case the uniform distribution of freon oil in many-compressor systems is achieved.

Bruch Sergey Viktorovich, OOO "Company MEL"