Calculation of the diameters of freon pipelines manually. Recommendations for the installation of a freon pipeline for compressor and condenser units. Regulatory documentation for the design and installation of copper pipelines
Oil in the freon circuit
The oil in the freon system is necessary to lubricate the compressor. It constantly leaves the compressor - it circulates in the freon circuit along with freon. If for any reason the oil does not return to the compressor, the CM will not be sufficiently lubricated. Oil dissolves in liquid freon, but does not dissolve in vapor. Moves through pipelines:
- after the compressor - superheated freon vapor + oil mist;
- after the evaporator - superheated freon vapor + oil film on the walls and oil in drip form;
- after the condenser - liquid freon with oil dissolved in it.
Therefore, oil retention problems can occur on steam lines. It can be solved by observing a sufficient speed of steam movement in pipelines, the necessary slope of pipes, and installing oil lifting loops.
Evaporator below.
a) Oil scrapers should be spaced every 6 meters on the ascending pipes to facilitate the return of oil to the compressor;
b) Make a collecting pit on the suction line after the expansion valve;
Evaporator above.
a) At the outlet of the evaporator, install a water seal above the evaporator to prevent liquid from draining into the compressor when the machine is stopped.
b) Make a collection pit in the suction line downstream of the evaporator to collect any liquid refrigerant that may accumulate during parking. When the compressor is turned on again, the refrigerant will quickly evaporate: it is advisable to make a sump away from the sensing element of the expansion valve, in order to avoid this phenomenon affecting the operation of the expansion valve.
c) On horizontal sections of the discharge pipeline, a slope of 1% in the direction of freon movement to facilitate the movement of oil in the right direction.
Capacitor below.
No special precautions need to be taken in this situation.
If the condenser is lower than the CIB, then the lifting height should not exceed 5 meters. However, if the CIB and the system as a whole are not best quality, then liquid freon may experience difficulty in lifting even at lower elevations.
a) It is advisable to install a shut-off valve on the inlet pipe of the condenser to prevent the flow of liquid freon into the compressor after shutdown refrigeration machine. This can happen if the capacitor is located in environment with a temperature higher than the compressor temperature.
b) On horizontal sections of the discharge pipeline, a slope of 1% in the direction of freon movement to facilitate the movement of oil in the right direction
capacitor above.
a) To exclude the overflow of liquid freon from the HP to the CM, when the refrigeration machine is stopped, install a valve in front of the HP.
b) Oil lifting loops should be placed at intervals of every 6 meters on the ascending pipelines to facilitate the return of oil to the compressor;
c) On horizontal sections of the discharge pipeline, a slope of 1% to facilitate the movement of oil in the correct direction.
Oil lifting loop operation.
When the oil level reaches the top wall of the tube, the oil will push further towards the compressor.
Calculation of freon pipelines.
The oil dissolves in liquid freon, so it is possible to maintain a small velocity in liquid pipelines - 0.15-0.5 m / s, which will provide low hydraulic resistance to movement. An increase in resistance leads to a loss in cooling capacity.
The oil does not dissolve in the vaporized freon, so it is necessary to maintain a significant speed in the steam pipelines so that the oil is carried by the steam. When moving, part of the oil covers the walls of the pipeline - this film is also moved by high-speed steam. The speed on the discharge side of the compressor is 10-18m/s. The speed on the suction side of the compressor is 8-15m/s.
On horizontal sections of very long pipelines, it is allowed to reduce the speed to 6 m / s.
Example:
Initial data:
Refrigerant R410a.
Required cooling capacity 50kW=50kJ/s
Evaporating temperature 5°C, condensing temperature 40°C
Superheat 10°C, Subcooling 0°C
Suction line solution:
1. The specific cooling capacity of the evaporator is q u=H1-H4=440-270=170kJ/kg
saturated liquid | Saturated steam |
||||||||
Temperature, ° С | Saturation pressure, 10 5 Pa | Density, kg/m³ | Specific enthalpy, kJ/kg | Specific entropy, kJ/(kg*K) | Saturation pressure, 10 5 Pa | Density, kg/m³ | Specific enthalpy, kJ/kg | Specific entropy, kJ/(kg*K) | Specific heat of vaporization, kJ/kg |
2. Freon mass consumption
m\u003d 50kW / 170kJ / kg \u003d 0.289kg / s
3. Specific volume of freon vapor on the suction side
v sun = 1/33.67kg/m³= 0.0297m³/kg
4. Volume flow rate of freon vapor on the suction side
Q= v Sun * m
Q\u003d 0.0297 m³ / kg x 0.289 kg / s \u003d 0.00858 m³ / s
5. Pipe inner diameter
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 pipe diameters are often selected in accordance with the tables given in the "Installation Instructions". When compiling such tables, the steam speeds necessary for the transfer of oil are taken into account.
Calculation of the volume of refueling freon
Simplified, the calculation of the mass of refrigerant charge is made according to a formula that takes into account the volume of liquid lines. This simple formula does not take into account steam lines, since the volume occupied by steam is very small:
Mzapr = P Ha. * (0.4 x V Spanish + TO g* V res + V l.m.), kg,
P Ha. - density of saturated liquid (freon) РR410a = 1.15 kg/dm³ (at 5°С);
V isp - internal volume of the air cooler (air coolers), dm³;
V res - the internal volume of the receiver of the refrigeration unit, dm³;
V l.m. - internal volume of liquid lines, dm³;
TO g is the coefficient taking into account the capacitor mounting scheme:
TO g=0.3 for condensing units without hydraulic condensing pressure regulator;
TO g=0.4 when using a hydraulic condensing pressure regulator (installation of the unit outdoors or version with a remote condenser).
Akaev Konstantin Evgenievich
Candidate of Technical Sciences St. Petersburg University of Food and Low-Temperature Technologies
When designing refrigeration units, it may be necessary to place the evaporative-compressor unit on the ground floor or in the basement, and the air-cooled condenser on the roof of the building. In such cases, special attention must be paid right choice the diameter and configuration of the discharge line to circulate the lubricating oil in the system.
In freon refrigeration units, unlike ammonia units, lubricating oil dissolves in freon, is carried away with the discharge vapor from the compressor, and can accumulate in various places of the pipeline system. In order for the oil leaving the compressor to rise through the discharge pipeline to the condenser, a siphon loop is installed on the horizontal section of the pipeline before going to the vertical section, in which oil accumulates. The size of the loop in the horizontal direction should be as small as possible. Usually it is made from bends bent at an angle of 90 °. Freon vapors passing through the siphon "crush" the oil accumulated there and carry it up the pipeline.
In refrigeration units with a constant (unregulated) cooling capacity, the speed of freon movement in the pipe does not change. In such installations, if the height of the vertical section is 2.5 m or less, the siphon may not be installed. At a height of more than 2.5 m, a siphon is installed at the beginning of the riser and additional siphons (oil-lifting loops) every 5-7 m, and the horizontal section of the pipeline is mounted with a slope towards the vertical riser.
The diameter of the discharge pipeline is determined by the formula:
Where: V=G/ρ- freon volume flow, m 3 / s; ρ, kg / m 3 - freon density; G- mass consumption of freon (kg / s) - G A \u003d Q 0 / (i 1 "" + i 4), the value of which is determined using the diagram i-lg p for the freon used in the installation at known (given) cooling capacity ( Q0), evaporation temperature ( t o) and condensation temperature ( t k).
If the refrigeration compressor is equipped with a cooling capacity control system (for example, from 100% to 25%), then when it decreases and, consequently, the flow rate and freon velocity in the ascending discharge pipeline decrease to a minimum value (8 m / s), the oil rise will stop. Therefore, in refrigeration units with adjustable compressor capacity, the ascending section of the pipeline (riser) is made of two parallel branches (Fig. 1).
Refrigeration unit scheme
At maximum performance of the installation, freon vapor and oil rise through both pipelines. At minimum performance and, consequently, the speed of freon movement in the main branch ( B ) oil accumulates in the siphon, preventing the movement of freon through this pipeline. In this case the rise of freon and oil will be carried out only through the pipeline BUT .
The calculation of the injection twin pipeline begins with the determination of the diameter of this pipeline. Since the cooling capacity is known for it (for example, 0.25 Q km) and the required freon vapor velocity (8 m/s), the required pipeline diameter is determined by formula (1), after which, according to the catalog copper pipes pipelines select a pipe whose diameter is closest to the value obtained by calculation.
Main branch pipeline diameter d B determined from the condition that at the maximum performance of the installation, when freon rises along both parallel branches, the hydraulic losses in the branches are the same:
G A + G B = G km (2)
Δr A = Δr B (3)
Where: λ - coefficient of hydraulic friction; ζ - coefficient of local losses.
From fig. 1 shows that the lengths of the sections, the number and nature of local resistances in both branches are approximately the same. That's why
Where
Problem solution example determining the diameters of the discharge pipelines of the refrigeration machine.
Determine the diameters of the discharge pipelines of the refrigeration machine for cooling water in the air conditioning system, taking into account the following initial data:
capacity control range .................................100-25%;
refrigerant ............................................................... ..............R 410A;
boiling temperature................................................ ...........to = 5 °C;
condensing temperature .................................................................. ....tk = 45 °C.
cooling load .................................................................. .........320 kW;
The dimensions and configuration of pipelines are shown in Fig.1.
p(for freon R 410A) is shown in fig. one.
Freon R410A parameters at the nodal points of the cycle are shown in Table 1.
Refrigeration cycle diagram in i-lg diagram p(for freon R404A)
Table 1
Freon R410A parameters at the key points of the refrigeration cycle(table to Fig. 2)
| points | Temperature, ° С |
Pressure, Bar |
Enthalpy, kJ/kg |
Density, |
| 1 | 10 | 9,30 | 289 | 34,6 |
| 1"" | 5 | 9,30 | 131 | 34,6 |
| 2 | 75 | 27,2 | 331 | 88,5 |
| 3 | 43 | 27,2 | 131 | 960 |
| 4 | 5 | 9,30 | 131 | - |
Solution.
Determining the diameters of pipelines, we start with the pipeline BUT , for which it is known that the freon speed in it must be at least 6 m / s, and the freon consumption must be minimal, i.e., at Q 0 \u003d 0.25 Q km= 0.25 x 320 = 80 kW.
1) specific cooling capacity at boiling point t 0 \u003d 5 ° С:
q 0 = 289 - 131 = 158 kJ/kg;
2) the total mass flow rate of freon in pipelines (in the discharge pipe of the compressor):
G km \u003d Q o, km / q 0 \u003d 320/158 \u003d 2.025 kg / s;
3) mass flow of freon in the pipeline BUT :
G A \u003d 0.25 x 2.025 \u003d 0.506 kg / s.
Determine the diameter of the pipeline BUT :
In 1952 he received a diploma from Moscow State Technical University. Bauman (Moscow) and was sent for distribution to the Ural Compressor Plant.
In 1954, upon his return to Moscow, he went to work at MRMK Refrigeration Equipment. Then the labor activity was continued at the All-Union Scientific Research Refrigeration Institute (VNIHI) as a senior researcher.
In 1970 he defended his dissertation and received the degree of candidate of technical sciences.
Later he worked in design organizations in the direction related to the design of refrigeration and air conditioning systems, at the same time taught and translated technical literature from in English.
The experience gained was the basis of the popular textbook - "Course and diploma design of refrigeration and air conditioning systems", the 3rd edition of which was published in 1989.
Today, Boris Konstantinovich continues to successfully consult and perform design work (in the ACAD environment), refrigeration units and air conditioning systems, and also provides services for the translation of technical literature and texts from English on the subject of refrigeration units and air conditioning systems.
For individuals and organizations interested in cooperation, personally, with Yavnel B.K., please send requests to.
Thanks.
A small manual for laying freon pipeline and drainage routes. With details and little tricks. All of them were born and came from, and I really hope they will greatly simplify the installation of ventilation and air conditioning systems.
Any installation of an air conditioner (in our case, the most common option is a split system) begins with the laying of copper pipes for freon circulation. Depending on the model of the air conditioner and its power (in terms of cooling parameters, in KW), copper pipes have different diameters. At the same time, the tube intended for gaseous freon has a larger diameter, and the tube for liquid freon, respectively, is smaller. Since we are dealing with copper, we must always remember that this material is very delicate and easily deformable. Therefore, the laying of tracks must be carried out only by qualified personnel and very carefully. The fact is that damage to copper pipes can cause freon leakage and, as a result, failure of the entire air conditioning system as a whole. This is complicated by the fact that freon does not have a pronounced odor and it is possible to understand exactly where the leak occurs only with the help of a special leak detector device.
So begin installation work by unwinding a coil of copper tube. They have a standard length of 15 meters. .
Important. There are two types of copper tubes: annealed and not. Annealed comes in coils and is easy to bend, unannealed comes in whips and has a rigid structure.
If we are lucky, and the distance between the indoor and outdoor unit is less than 15 meters, the work will only consist in laying one bay (each diameter). If the distance exceeds this footage, then the copper tubes must be soldered together.
After the required length of the copper tube is unwound from the coil, the excess must be cut off. This is done using a special pipe cutter, since when cutting the pipe it does not leave metal chips that can get inside the system. And this is unacceptable. In my practice, there were those who bit the pipes with wire cutters and even cut them off with a grinder! As a result of such installation, the air conditioner will live for a couple of three months and the compressor will break down "for unknown reasons."
Important. After the copper tube is cut to a suitable size, it must be closed with special plastic plugs or simply sealed with plumbing tape.
It's time to isolate the copper traces. For these purposes, special insulation based on foamed rubber is used. It is produced in whips of two meters each and differs in standard sizes for each specific diameter of the copper tube. When pulling the insulation on the pipe, care must be taken not to tear it. Between themselves, the whips, after tightly adjoining each other, are glued together with adhesive tape. Most often, gray plumbing tape is used. Further, a pair of copper pipes prepared in this way (liquid and gas) is mounted in the serviced room. Usually, the routes run in the interceiling space (between the concrete floor and the false ceiling). Also in the composition of the freon pipeline line there is an interconnect cable. It links the internal and outdoor unit. When fastening tracks to a concrete floor, perforated tape is most widely used. It is cut into small pieces and the tubes are pulled for secure fixation.
Important. Excessive force is not allowed when fixing with perforated tape, as this can lead to deformation of a rather plastic and soft copper tube. Also, very strongly compressed insulation loses its thermal insulation properties and condensation may occur in such places.
In laying the copper routes of the freon pipeline, the most difficult place is the passage of holes in the walls, especially in thick monolithic ones. At the same time, rather capricious insulation usually breaks, and this is unacceptable. the places of the tubes where it is not present are frosted over. To avoid this, they resort to a kind of "reinforcement" of the insulation. To do this, along the entire length of the tube (which will pass through the hole), right on top of the insulation, they glue it with dense plumbing tape, which takes on the main “blow”.
That, in fact, is all. The installation of the copper lines of the freon piping is completed. Now it remains only to carefully check the integrity of the insulation and general form the tracks themselves.
Method for calculating the diameters of refrigeration pipelines using nomograms
1. Initial data taken in the preparation of nomograms.
A. Maximum losses in pipelines:
Suction line at -8°C: 2°K;
Suction line at -13°C, -18°C, -28°C and -38°C: 1.5°K;
On the discharge line: 1 °K
On the liquid line: 1 °K.
B. Speeds:
The maximum allowable gas flow velocity is 15 m/s, so as not to exceed the noise level that is unacceptable to the environment;
Minimum allowable gas flow rate;
a) in vertical pipes with bends: the minimum gas velocity in vertical sections is selected from the condition of ensuring the return of oil to the compressor and depends on the temperature of the refrigerant and the diameter of the pipeline;
b) in horizontal pipes: not less than 3.5 m/s to ensure normal oil return;
The maximum speed of the liquid phase is not more than 1.5 m/s in order to avoid the destruction of solenoid valves during hydraulic shocks.
C. The concept of equivalent length .
To take into account local resistances (valves, turns), the concept of equivalent length is introduced, which is determined by multiplying the actual length of the line by a correction factor. The coefficient values are as follows:
For lengths from 8 to 30 m: 1.75
For lengths over 30 m: 1.50.
D. Theoretical working conditions :
Condensing temperature: +43°С - without hypothermia;
Intake gas temperature;
a) for -8°С and -18°С: +18°С
b) for -28°С and -38°С: 0°С
2. Use of nomograms for selection of pipe diameters.
A. Select the nomogram corresponding to the refrigerant used.
B. Suction lines.
Select the nomogram whose reference suction temperature is closest to the set temperature;
Plot along the ordinate axis - the given cooling capacity, along the abscissa axis - the actual measured length of the line (the correction for the equivalent length has already been taken into account when constructing the nomogram).
Near the point of intersection found in this way, select the corresponding most suitable diameter. The decisive factor in this case always remains the consideration of restrictions on the flow rate:
The found point must be shifted to the right if you want to reduce pressure losses as much as possible;
If the found point is in the zone of acceptable losses, it should be shifted to the left (see Examples).
To check the correctness of the selected diameter, it is necessary, for a given cooling capacity and a selected diameter value, to determine from the nomograms the length of the pipe, which corresponds to the losses indicated and the title of the nomogram. Then the real losses can be calculated by the formula:
∆Р(∆ Т) actual = ∆Р(∆ Т)nom х D fak
Dnom.
∆Р(∆ Т) actual- respectively, the pressure (or temperature) loss, actual and nominal, indicated in the title of the nomogram;
D fak- actually measured length of pipelines;
D nom.- the length of the pipeline, determined by the nomogram at the point of intersection of the selected diameter of the pipeline and the ordinate of the given cooling capacity.
When choosing a pipe diameter, one should pay attention to the position of the obtained diameter value in relation to the curves that limit the permissible values of the flow velocity in the pipe: for horizontal pipelines - not less than 3.5 m / s, for vertical pipelines - not lower than the values \u200b\u200bcorresponding to the curve "minimum gas velocity in vertical pipelines for oil return". For vertical piping, the selected diameter value should be to the left of this curve. At the same time, it is desirable that the gas velocity does not exceed 15 m/s, if the noise level in the pipes is important for the installation.
C. Injection lines.
The diameter selection method is the same as for the suction lines, but the reference value for the condensing temperature is assumed to be +43 °C.
D. Double piping.
Designed for ascending vertical suction or discharge lines with variable flow (multi-compressor units, compressors with capacity control or multi-chamber units), as well as for single pipeline diameters above 2 5/8".
To determine the diameters of twin pipes, first select the allowable diameter of a single ascending pipe for a given cooling capacity, similar to point "A". Then, using the table indicated at the top left of the diagram, find the recommended diameters for a pair of ascending pipelines, equivalent to the found value of a single pipeline. This pair is selected in a proportion of about 1/3 ÷ 2/3 of the specified cooling capacity.
E. Liquid lines.
Pressure losses in liquid lines are determined by two factors:
Dynamic pressure losses, depending on the speed of the fluid (indicated directly in the nomograms);
Static pressure losses due to the difference in column heights (calculated depending on the layout of the installation, taking into account the magnitude of static losses per meter of the pipeline rise height: for liquid R22 at a temperature of +43 ° C - 0.112 bar or 0.28 ° K per 1 m, and with taking into account subcooling ≈ 0.12 bar or ≈ 0.3 °K).
These piping must be carefully dimensioned to avoid pressure losses that exceed the allowable subcooling. Otherwise, the refrigerant in the liquid line may spontaneously boil (premature vaporization). If the circuit contains quick-acting valves (for example, electromagnetic), the speed of the liquid in the pipelines must not exceed 1.5 m/s. There are no restrictions from below for the speed of fluid movement in pipes (see Example 1). For lines connecting the condenser to the receiver, this speed must always be below 0.5 m/s. In any case, the receiver must be below the condenser. The minimum height difference is 0.3 m. If these conditions are not met, the condenser will accumulate more refrigerant than calculated, i.e. its performance will be lower and the condensing pressure higher than calculated.
3. Practical examples.
A. Selection of pipelines for a typical installation (one unit, one cold room).
Initial data: refrigerant R22;
evaporation temperature -18 °С;
compressor/chamber distance 40 m;
compressor/condenser distance 20 m;
consumed cooling capacity W, at -16 °С;
nominal cooling capacity W, at -18 °С.
According to the nomogram for R22 at Тsp = -18 "С, we determine that with a cooling capacity of 23000 W and losses of 1.5 °K, the length of the vertical pipeline with a diameter of 1 5/8" should be about 30 m, and the length of the horizontal pipeline with a diameter of 2 1/8 "About 150 m.
Losses for a 40 m pipeline can be calculated using the above formula. For pipelines with horizontal and vertical sections, different section diameters are selected, the losses in each of the sections are calculated, and then the results are added up. When determining the diameter of the pipelines, it is necessary to take into account the steady value of the cooling capacity of the unit at equilibrium temperature, and not the cooling capacity, which is necessary to ensure the operation of the chamber in continuous mode.
It can be seen that among the initial data taken into account when choosing the diameter of pipelines from a variety of acceptable options, depending on the needs and restrictions of the installation, priority is given to pressure losses, speed, noise level, operating costs, investment volume.
C. Selection of pipeline diameters for multi-chamber plants with a central compressor unit (CCU).
To determine the diameter of a pipeline section common to all chambers, the distance from the Central Design Bureau to the most distant chamber should be taken as the length taken into account;
To determine the diameter of the pipeline for each chamber, the distance from this chamber to the CCB should be taken as the length taken into account.
Installation scheme
and 1 1/8" at -13 ° C (the first value is the liquid line, the second is the suction line).
Chamber 2: W, 45 m: 1/2" and 1 1/8" at -8°C.
♦Chamber 1+2:W, 70m: 5/8" and 1 5/8" at -18°C.
Chamber 3: 3000W, 60m: 3/8" and 3/4" at -8°C. (-13 °C)
Chamber 4: 6000 W, 50 m: 1/2" and 1 1/8" at -18°C.
♦Camera 3+4: 9 000W, 60m: 1/2" and I 3/8" at -18°C
♦Chamber 1+2+3+4:W, 70m: 3/4" and 2 1/8" at -18°C.
♦Upstream dual common piping: 1 5/8" = 7/8" + 1 3/8".
This approach takes into account both the length of the pipelines and the pressure losses due to this length, taking into account that the chambers have different evaporation temperatures, and that these losses are at least the same as on the evaporation pressure regulator.
Oil-lifting and oil-locking loops (traps) on gas pipe when the evaporator is above the condensing unit (CCU).
Oil-lifting and oil-locking loops (traps) on the gas pipe when the evaporator is below the condensing unit (CCU).
| EUROPA LE |
Length up to 10M |
Length up to 20 m |
Length up to 30 m |
|||
|
Ø
gas, MM |
Ø
liquid, MM |
Ø
gas, MM |
Ø
liquid, MM |
Ø
gas, MM |
Ø
liquid, MM |
|
| 6 | 18 | 12 | 18 | 12 | 18 | 12 |
| 8 | 18 | 12 | 18 | 12 | 18 | 16 |
| 10 | 18 | 12 | 22 | 16 | 22 | 16 |
| 14 | 22 | 16 | 22 | 16 | 28 | 16 |
| 16 | 22 | 16 | 28 | 16 | 28 | 18 |
| 18 | 28 | 16 | 28 | 18 | 28 | 18 |
| 21 | 28 | 16 | 28 | 18 | 28 | 22 |
| 25 | 28 | 18 | 28 | 18 | 35 | 22 |
| 28 | 28 | 18 | 35 | 22 | 35 | 22 |
| 31 | 35 | 18 | 35 | 22 | 35 | 22 |
| 37 | 35 | 22 | 35 | 22 | 35 | 28 |
| 41 | 35 | 22 | 35 | 22 | 35 | 28 |
Estimated amount of refrigerant required to charge the KKB refrigeration system (M total.) is determined by the following formula:
M total. \u003d M kkb + M isp. + M tr. ;
where M kkb(kg) - the mass of the refrigerant attributable to the KKB (determined according to table 2),M isp.- the mass of the refrigerant per evaporator (determined by the formula ),M tr.- the mass of the refrigerant per pipeline (determined by the formula ).
Table 2. Mass of refrigerant attributable to KKB, kg
| EUROPA LE | 6 | 8 | 10 | 14 | 16 | 18 | 21 | 25 | 28 | 31 | 37 | 41 |
| Refrigerant mass, kg | 1,0 | 1,3 | 1,6 | 2,4 | 2,7 | 3,2 | 3,7 | 4,4 | 5,1 | 5,6 | 6,6 | 7,4 |
The mass of refrigerant per evaporator (in one circuit) can be calculated using a simplified formula:
M isp. = VSpanishx 0.316 ÷ n ;
where VSpanish(l) - the internal volume of the evaporator (volume of the medium), which is indicated in the technical description for the ventilation unit in the cooler section or on the nameplate,n- number of evaporator circuits. This formula can be used with the same capacity of the evaporator circuits. In the case of several circuits with different capacities, instead of "÷ n" should be replaced with "x proportion of circuit performance”, for example, for a circuit with 30% capacity it will be “x 0.3».
The mass of refrigerant per pipeline (in one circuit) can be calculated using the following formula:
M tr. \u003d M tr.zh x L tr.zh + M tr.vs x L tr.vs;
where M tr.zh And M tr.sun(kg) - the mass of the refrigerant per 1 meter of the liquid pipe and the suction pipe, respectively (determined according to table 3),L tr.g And L tr.sun(m) are the lengths of the liquid and suction pipes. If, for any justified reason, the diameters of the actually installed pipelines do not correspond to the recommended ones, then in the calculation it is necessary to choose the value of the mass of the refrigerant for the actual diameters. In case of non-compliance of the actual diameters of the pipeline with the recommended ones, the manufacturer and supplier disclaim any warranty obligations.
Table 3. Mass of refrigerant per 1 meter of pipe, kg
| pipe Ø, mm | 12 | 16 | 18 | 22 | 28 | 35 | 42 | 54 | 67 | 76 |
| Gas, kg/m | 0,007 | 0,014 | 0,019 | 0,029 | 0,045 | 0,074 | 0,111 | 0,182 | 0,289 | 0,377 |
| Liquid, kg/m | 0,074 | 0,139 | 0,182 | 0,285 | 0,445 | 0,729 | 1,082 | 1,779 | 2,825 | 3,689 |
EXAMPLE
It is necessary to calculate the amount of refrigerant to be charged a system consisting of a double-circuit evaporator, two EUROPA LE 25 ECUs, with pipe lengths KKB1 liquid 14 m, KKB1 suction 14.5 m, KKB2 liquid 19.5 m, KKB2 suction 20.5 m, internal volume of the evaporator 2 .89 l.
M total 1 \u003d M kkb1 + M isp. 1 + M tr. 1 \u003d
= 4,4 + (VSpanish
\u003d 4.4 + (2.89 x 0.316 ÷ 2) + (0.182 x 14 + 0.045 x 14.5) \u003d 8.06 kg
M total .2 = M kkb 2 + M isp .2 + M tr .2 =
= 4,4 + (VSpanishx 0.316 ÷ number of evaporator circuits) + M tr.l х L tr.l + M tr.vs x L tr.vs =
\u003d 4.4 + (2.89 x 0.316 ÷ 2) + (0.182 x 19.5 + 0.074 x 20.5) \u003d 9.92 kg
Specialists of the Airkat Klimatekhnik company will select the most efficient refrigeration scheme and quickly calculate the cost. The price may also include: design, installation and commissioning. For advice, you can contact any of the branches and representative offices of the company.
