Ministry of Education and Science of the Russian Federation

NOVOSIBIRSK STATE TECHNICAL UNIVERSITY

_____________________________________________________________

DEFINITION OF CHARACTERISTICS
REFRIGERATION UNIT

Methodical instructions

for FES students of all forms of education

Novosibirsk
2010

UDC 621.565 (07)

Compiled by: Cand. tech. Sciences, Assoc. ,

Reviewer: Dr. Sciences, prof.

The work was prepared at the Department of Thermal Power Plants

© Novosibirsk State

Technical University, 2010

PURPOSE OF THE LABORATORY WORK

1. Practical consolidation of knowledge on the second law of thermodynamics, cycles, refrigeration units.

2. Familiarization with refrigeration unit IF-56 and its technical characteristics.

3. Study and construction of refrigeration cycles.

4. Determination of the main characteristics, refrigeration unit.

1. THEORETICAL BASIS OF WORK

REFRIGERATION UNIT

1.1. Reverse Carnot cycle

A refrigeration unit is designed to transfer heat from a cold source to a hot one. According to Clausius' formulation of the second law of thermodynamics, heat cannot by itself pass from a cold body to a hot one. In a refrigeration plant, this heat transfer does not occur by itself, but due to the mechanical energy of the compressor spent on compressing the refrigerant vapor.

The main characteristic of the refrigeration unit is the refrigeration coefficient, the expression of which is obtained from the equation of the first law of thermodynamics, written for the reverse cycle of the refrigeration unit, taking into account the fact that for any cycle the change in the internal energy of the working fluid D u= 0, namely:

q= q 1 – q 2 = l, (1.1)

where q 1 - heat given to the hot spring; q 2 - heat removed from a cold source; l – mechanical work compressor.

From (1.1) it follows that heat is transferred to a hot source

q 1 = q 2 + l, (1.2)

a the coefficient of performance is the fraction of heat q 2, transferred from a cold source to a hot one, per unit of compressor work expended

(1.3)

The maximum value of the coefficient of performance for a given temperature range between T hot mountains and T the cold of cold heat sources has a reverse Carnot cycle (Fig.1.1),

Rice. 1.1. Reverse Carnot cycle

for which the heat supplied at t 2 = const from a cold source to a working fluid:

q 2 = T 2 ( s 1 – s 4) = T 2 Ds (1.4)

and the warmth given off at t 1 = const from the working fluid to the cold source:

q 1 = T one · ( s 2 – s 3) = T 1 Ds, (1.5)

In the reverse Carnot cycle: 1-2 - adiabatic compression of the working fluid, as a result of which the temperature of the working fluid T 2 gets higher temperature T hot spring mountains; 2-3 - isothermal heat removal q 1 from the working fluid to the hot spring; 3-4 - adiabatic expansion of the working fluid; 4-1 - isothermal heat supply q 2 from a cold source to a working medium. Taking into account relations (1.4) and (1.5), equation (1.3) for the refrigerating coefficient of the reverse Carnot cycle can be represented as:

The higher the e value, the more efficient the refrigeration cycle and the less work l required for heat transfer q 2 from cold source to hot.

1.2. Cycle of a vapor compression refrigeration unit

Isothermal supply and removal of heat in a refrigeration unit is possible if the refrigerant is a low-boiling liquid, the boiling point of which at atmospheric pressure t 0 £ 0 oC, and for negative temperatures boiling boiling pressure p 0 must be more than atmospheric to prevent air leaks into the evaporator. low compression pressures make it possible to manufacture lightweight compressor and other elements of the refrigeration unit. With a significant latent heat of vaporization r low specific volumes are desirable v, which allows to reduce the size of the compressor.

A good refrigerant is ammonia NH3 (at the boiling point t k = 20 ° C, saturation pressure p k = 8.57 bar and at t 0 = -34 оС, p 0 = 0.98 bar). Its latent heat of vaporization is higher than that of other refrigerating agents, but its disadvantages are toxicity and corrosiveness towards non-ferrous metals, therefore, ammonia is not used in household refrigeration units. Methyl chloride (CH3CL) and ethane (C2H6) are good refrigerants; sulphurous anhydride (SO2) is not used due to its high toxicity.

Freons - fluorochlorine derivatives of the simplest hydrocarbons (mainly methane) - are widely used as refrigerants. Distinctive properties of freons are their chemical resistance, non-toxicity, lack of interaction with construction materials at t < 200 оС. В прошлом веке наиболее wide use received R12, or freon - 12 (CF2CL2 - difluorodichloromethane), which has the following thermophysical characteristics: molecular weight m = 120.92; boiling point at atmospheric pressure p 0 = 1 bar; t 0 = -30.3 oC; critical parameters R12: p cr = 41.32 bar; t cr = 111.8 ° C; v cr = 1.78 × 10-3 m3 / kg; adiabatic exponent k = 1,14.

The production of freon-12, as a substance destroying the ozone layer, was banned in Russia in 2000, only the use of R12 already produced or extracted from equipment is allowed.

2. operation of the IF-56 refrigeration unit

2.1. refrigeration unit

Unit IF-56 is designed to cool air in refrigerating chamber 9 (Fig. 2.1).

Fan "href =" / text / category / ventilyator / "rel =" bookmark "> fan; 4 - receiver; 5 - capacitor;

6 - filter drier; 7 - throttle; 8 - evaporator; 9 - refrigerating chamber

Rice. 2.2. Refrigeration cycle

In the process of throttling liquid freon in throttle 7 (process 4-5 in ph diagram), it partially evaporates, while the main evaporation of freon occurs in evaporator 8 due to the heat taken from the air in the refrigerating chamber (isobaric-isothermal process 5-6 at p 0 = const and t 0 = const). Superheated steam with temperature enters compressor 1, where it is compressed from pressure p 0 to pressure p K (polytropic, valid compression 1-2d). In fig. 2.2 also depicts the theoretical, adiabatic compression 1-2A at s 1 = const..gif "width =" 16 "height =" 25 "> (process 4 * -4). Liquid freon flows into the receiver 5, from where it flows through the filter-drier 6 to the throttle 7.

Technical details

Evaporator 8 consists of finned batteries - convectors. The batteries are equipped with a choke 7 with a thermostatic valve. Condenser 4 with forced air cooled, fan performance V B = 0.61 m3 / s.

In fig. 2.3 shows the actual cycle of a vapor compression refrigeration unit, built according to the results of its tests: 1-2а - adiabatic (theoretical) compression of refrigerant vapors; 1-2d - actual compression in the compressor; 2d-3 - isobaric cooling of vapors to
condensing temperature t TO; 3-4 * - isobaric-isothermal condensation of refrigerant vapors in the condenser; 4 * -4 - condensate overcooling;
4-5 - throttling ( h 5 = h 4), as a result of which the liquid refrigerant partially evaporates; 5-6 - isobaric-isothermal evaporation in the evaporator of the refrigerating chamber; 6-1 - isobaric superheat of dry saturated steam (point 6, X= 1) to temperature t 1.

Rice. 2.3. Refrigeration cycle in ph-chart

2.2. performance characteristics

The main performance characteristics refrigeration unit are refrigerating capacity Q, power consumption N, refrigerant consumption G and specific refrigerating capacity q... Cooling capacity is determined by the formula, kW:

Q = Gq = G(h 1 – h 4), (2.1)

where G- refrigerant consumption, kg / s; h 1 - enthalpy of steam at the outlet from the evaporator, kJ / kg; h 4 - enthalpy of the liquid refrigerant before the choke, kJ / kg; q = h 1 – h 4 - specific refrigerating capacity, kJ / kg.

The specific volumetric cooling capacity, kJ / m3:

q v = q/ v 1 = (h 1 – h 4)/v 1. (2.2)

Here v 1 - specific volume of steam at the outlet of the evaporator, m3 / kg.

Refrigerant flow rate is found by the formula, kg / s:

G = Q TO/( h 2D - h 4), (2.3)

Q = c’pmV V( t IN 2 - t IN 1). (2.4)

Here VВ = 0.61 m3 / s - capacity of the fan cooling the condenser; t IN 1, tВ2 - air temperature at the inlet and outlet of the condenser, ºС; c’pm- average volumetric isobaric heat capacity of air, kJ / (m3 K):

c’pm = (μ cpm)/(μ v 0), (2.5)

where (μ v 0) = 22.4 m3 / kmol - the volume of a kilo mole of air under normal physical conditions; (μ cpm) Is the average isobaric molar heat capacity of air, which is determined by the empirical formula, kJ / (kmol K):

(μ cpm) = 29.1 + 5.6 10-4 ( t B1 + t IN 2). (2.6)

Theoretical power of adiabatic compression of refrigerant vapors in the process 1-2A, kW:

N A = G/(h 2A - h 1), (2.7)

Relative adiabatic and actual refrigerating capacities:

k A = Q/N A; (2.8)

k = Q/N, (2.9)

representing the heat transferred from a cold source to a hot one, per unit of theoretical power (adiabatic) and actual (electric power of the compressor drive). The coefficient of performance has the same physical meaning and is determined by the formula:

ε = ( h 1 – h 4)/(h 2D - h 1). (2.10)

3. Refrigeration testing

After starting the refrigeration unit, it is necessary to wait for the establishment of a stationary mode ( t 1 = const, t 2Д = const), then measure all the readings of the devices and enter them into the measurement table 3.1, based on the results of which, build the cycle of the refrigeration unit in ph- and ts-coordinates using the steam diagram for Freon-12, shown in Fig. 2.2. The calculation of the main characteristics of the refrigeration unit is carried out in table. 3.2. Evaporation temperature t 0 and condensation t K is found depending on the pressures p 0 and p K according to the table. 3.3. Absolute pressures p 0 and p K is determined by the formulas, bar:

p 0 = B/750 + 0,981p 0M, (3.1)

p K = B/750 + 0,981p KM, (3.2)

where V – Atmosphere pressure on the barometer, mm. rt. Art .; p 0M - excess pressure of evaporation according to the manometer, ati; pКМ - overpressure of condensation according to the manometer, ati.

Table 3.1

Measurement results

Table 3.2

Calculation of the main characteristics of the refrigeration unit

Table 3.3

Freon-12 saturation pressure (CF2 Cl2 - difluorodichloromethane)

1. Scheme and description of the refrigeration unit.

2. Tables of measurements and calculations.

3. Completed task.

Exercise

1. Build a refrigeration unit cycle in ph-diagram (Fig. A.1).

2. Make a table. 3.4 using ph-chart.

Table 3.4

Initial data for constructing a refrigeration unit cycle ints -coordinates

2. Build a refrigeration unit cycle in ts-chart (Fig. A.2).

3. Determine the value of the coefficient of performance of the reverse Carnot cycle using the formula (1.6) for T 1 = T To and T 2 = T 0 and compare it with the coefficient of performance of a real installation.

LITERATURE

1. Sharov, Yu. I. Comparison of the cycles of refrigeration units on alternative refrigerants / // Energetika i teploenergetika. - Novosibirsk: NSTU. - 2003. - Issue. 7, - S. 194-198.

2. Kirillin, V.A. Technical thermodynamics /,. - M .: Energiya, 1974 .-- 447 p.

3. Vargaftik, N. B. Reference for thermophysical properties gases and liquids /. - M .: science, 1972 .-- 720 p.

4. Andryushchenko, A. I. Fundamentals of technical thermodynamics of real processes /. - M .: graduate School, 1975.

Compressor type:

refrigeration piston, non-direct-flow, single-stage, stuffing box, vertical.

Designed for work in stationary and transport refrigeration units.

Technical specifications , ,

Compressor characteristics and description ...

Cylinder diameter - 67.5 mm
The piston stroke is 50 mm.
The number of cylinders is 2.
The rated shaft speed is 24s-1 (1440 rpm).
The compressor is allowed to operate at a shaft rotation speed s-1 (1650 rpm).
The described piston volume, m3 / h - 32.8 (at n = 24 s-1). 37.5 (at n = 27.5 s-1).
The type of drive is through a V-belt transmission or a clutch.

Refrigerating agents:

R12 - GOST 19212-87

R22- GOST 8502-88

R142- TU 6-02-588-80

Compressors are repairable items and require periodic maintenance:

Maintenance after 500 hours; 2000 h, with oil change and gas filter cleaning;
- Maintenance after 3750 h:
- Maintenance after 7600 h;
- medium, repair after 22500 hours;
- overhaul after 45,000 h.

In the process of manufacturing compressors, the design of their units and parts is constantly being improved. Therefore, in the supplied compressor, individual parts and assemblies may slightly differ from those described in the passport.

The principle of operation of the compressor is as follows:

when the crankshaft rotates, the pistons are reciprocated
translational motion... When the piston moves downward in the space formed by the cylinder and the valve plate, a vacuum is created, the suction valve plates bend, opening the holes in the valve plate through which refrigerant vapors pass into the cylinder. Filling with refrigerant vapors will continue until the piston reaches its bottom position. The upward movement of the piston closes the suction valves. The pressure in the cylinders will increase. As soon as the pressure in the cylinder is greater than the pressure in the discharge line, the discharge valves will open the holes in the 'Valve plate' for the refrigerant vapor to flow into the discharge chamber. Having reached the upper position, the piston will begin to lower, the discharge valves will close and there will be a vacuum in the cylinder again. Then the cycle repeats. Compressor crankcase (Fig. 1) is a cast iron with support for crankshaft bearings at the ends. On one side of the crankcase cover there is a graphite oil seal, on the other side the crankcase is closed with a cover in which a cracker is located, which serves as a stop for the crankshaft. The crankcase has two plugs, one of which is used to fill the compressor with oil and the other to drain the oil. A sight glass is located on the side wall of the crankcase for monitoring the oil level in the compressor. The flange in the upper part of the crankcase is intended for attaching the cylinder block to it. The cylinder block combines two cylinders into one cast-iron casting, which has two flanges: the upper one for attaching the valve plate with the block cover and the lower one for attaching to the crankcase. In order to protect the compressor and the system from clogging, a filter is installed in the suction cavity of the unit. To ensure the return of oil accumulated in the suction cavity, a plug with an opening is provided, which connects the suction cavity of the block with the crankcase. The connecting rod-piston group consists of a piston, a connecting rod, finger. sealing and oil scraper rings. The valve plate is installed in the upper part of the compressor between the cylinder blocks and the cylinder head, and consists of a valve plate, plates for suction and discharge valves, suction valve seats, springs, bushings, and guides for discharge valves. The valve plate has removable suction valve seats in the form of hardened steel plates with two elongated slots in each. The slots are closed with steel spring plates, which are located in the grooves of the valve plate. Saddles and plate are secured with pins. The plates of the discharge valves are steel, round, located in the annular grooves of the plate, which are the valve seats. To prevent lateral displacement, during operation, the plates are centered by stamped guides, the legs of which rest against the bottom of the annular groove of the valve plate. From above, the plates are pressed to the valve plate by springs using a common bar, which is bolted to the plate with bushings. There are 4 pins fixed in the bar, on which bushings are placed that limit the lifting of the discharge valves. The bushes are pressed against the directional valves by buffer springs. The buffer springs do not work under normal conditions; They serve to protect the valves from breakage during hydraulic shocks in the event of liquid refrigerant or excess oil entering the cylinders. The valve plate is split internal baffle cylinder covers for suction and discharge cavities. In the upper, extreme position of the piston between the valve plate and the bottom of the piston there is a gap of 0.2 ... 0.17 mm, called the linear dead space. The oil seal seals the outward drive end of the crankshaft. Stuffing box type - self-aligning graphite. Shut-off valves - suction and discharge, are used to connect the compressor to the refrigerant system. An angled or straight fitting, as well as a fitting or tee for connecting devices, is attached to the body of the shut-off valve. When the spindle rotates clockwise, it closes the main passage through the valve into the system with a spool in the extreme position and opens the passage to the fitting. When the spindle rotates counterclockwise, in the extreme position, it closes with a cone, the passage to the fitting and completely opens the main passage through the valve into the system and closes the passage to the tee. In intermediate positions, the passage is open both to the system and to the tee. The moving parts of the compressor are lubricated by spraying. Lubrication of the crankshaft connecting rod journals occurs through the drilled sloped channels in the upper part of the lower connecting rod head. The upper connecting rod head is lubricated with oil flowing down from the inner side of the bottom, piston and entering the drilled hole of the upper connecting rod head. To reduce oil carryover from the crankcase, the oil is a removable ring on the piston, which dumps some of the oil from the cylinder walls back into the crankcase.

The amount of oil to be filled: 1.7 + - 0.1 kg.

Cooling performance and effective power, see the table:

Notes: 1. Data are given in the following mode: boiling point - minus 15 ° С; condensation temperature - 30 ° С; suction temperature - 20 ° С; liquid temperature in front of the throttle device 30 ° С - for R12, R22 freons; boiling point - 5 ° С; condensation temperature - 60 С; suction temperature - 20 ° С: liquid temperature in front of the throttle device - 60 ° С - for freon 142;

A deviation from the nominal values ​​of refrigerating capacity and effective power is allowed within ± 7%.

The difference between the discharge and suction pressures should not exceed 1.7 MPa (17 kgf / s * 1), and the ratio of the discharge pressure to the suction pressure should not exceed 1.2.

Discharge temperature should not exceed 160 ° С for R22 and 140 ° С for R12 and R142.

Design pressure 1.80 MPa (1.8 kgf.cm2)

Compressors must remain tight when checked overpressure 1.80 mPa (1.8 kgf.cm2).

When working on R22, R12 and R142, the suction temperature should be:

tvs = t0 + (15 ... 20 ° С) at t0 ≥ 0 ° С;

tvs = 20 ° С at -20 ° С< t0 < 0°С;

tvs = t0 + (35 ... 40 ° С) at t0< -20°С;

Unit IF-56 is designed to cool air in refrigerating chamber 9 (Fig. 2.1). The main elements are: a freon reciprocating compressor 1, an air-cooled condenser 4, a throttle 7, evaporative batteries 8, a filter drier 6 filled with a desiccant - silica gel, a receiver 5 for collecting condensate, a fan 3 and an electric motor 2.

Rice. 2.1. Refrigerating unit diagram IF-56:

Technical details

Evaporator 8 consists of two ribbed batteries - convectors. the batteries are equipped with a 7 throttle with a thermostatic valve. 4 forced air cooled condenser, fan capacity

VB = 0.61 m3 / s.

In fig. 2.2 and 2.3 show the actual cycle of a vapor compression refrigeration unit, built according to the results of its tests: 1 - 2а - adiabatic (theoretical) compression of refrigerant vapors; 1 - 2d - actual compression in the compressor; 2e - 3 - isobaric cooling of vapors to

condensation temperature tк; 3 - 4 * - isobaric-isothermal condensation of refrigerant vapors in the condenser; 4 * - 4 - condensate overcooling;

4 - 5 - throttling (h5 = h4), as a result of which the liquid refrigerant partially evaporates; 5 - 6 - isobaric-isothermal evaporation in the evaporator of the refrigerating chamber; 6 - 1 - isobaric superheat of dry saturated steam (point 6, x = 1) to temperature t1.

Refrigeration unit

Unit IF-56 is designed to cool air in refrigerating chamber 9 (Fig. 2.1).

Rice. 2.1. Refrigeration unit IF-56

1 - compressor; 2 - electric motor; 3 - fan; 4 - receiver; 5 - capacitor;

6 - filter drier; 7 - throttle; 8 - evaporator; 9 - refrigerating chamber

Rice. 2.2. Refrigeration cycle

In the process of throttling liquid freon in throttle 7 (process 4-5 in ph diagram), it partially evaporates, while the main evaporation of freon occurs in evaporator 8 due to the heat taken from the air in the refrigerating chamber (isobaric-isothermal process 5-6 at p 0 = const and t 0 = const). Superheated steam with temperature enters compressor 1, where it is compressed from pressure p 0 to pressure p K (polytropic, valid compression 1-2d). In fig. 2.2 also shows the theoretical, adiabatic compression of 1-2 A at s 1 = const... In the condenser, 4 vapors of freon are cooled to the condensation temperature (process 2d-3), then condense (isobaric-isothermal process 3-4 * at p K = const and t K = const... In this case, the liquid freon is supercooled to a temperature (process 4 * -4). The liquid freon flows into the receiver 5, from where it flows through the filter drier 6 to the throttle 7.

Technical details

Evaporator 8 consists of finned batteries - convectors. The batteries are equipped with a choke 7 with a thermostatic valve. 4 forced air cooled condenser, fan capacity V B = 0.61 m 3 / s.

In fig. 2.3 shows the actual cycle of a vapor compression refrigeration unit, built according to the results of its tests: 1-2а - adiabatic (theoretical) compression of refrigerant vapors; 1-2d - actual compression in the compressor; 2d-3 - isobaric cooling of vapors to
condensing temperature t TO; 3-4 * - isobaric-isothermal condensation of refrigerant vapors in the condenser; 4 * -4 - condensate overcooling;
4-5 - throttling ( h 5 = h 4), as a result of which the liquid refrigerant partially evaporates; 5-6 - isobaric-isothermal evaporation in the evaporator of the refrigerating chamber; 6-1 - isobaric superheat of dry saturated steam (point 6, X= 1) to temperature t 1 .

Rice. 2.3. Refrigeration cycle in ph-chart

Performance characteristics

The main operational characteristics of the refrigeration unit are refrigeration capacity Q, power consumption N, refrigerant consumption G and specific refrigerating capacity q... Cooling capacity is determined by the formula, kW:

Q = Gq = G(h 1 – h 4), (2.1)

where G- refrigerant consumption, kg / s; h 1 - enthalpy of steam at the outlet from the evaporator, kJ / kg; h 4 - enthalpy of the liquid refrigerant before the choke, kJ / kg; q = h 1 – h 4 - specific refrigerating capacity, kJ / kg.

The specific volumetric refrigerating capacity, kJ / m 3:

q v = q / v 1 = (h 1 – h 4)/v 1 . (2.2)

Here v 1 - specific volume of steam at the outlet of the evaporator, m 3 / kg.

Refrigerant flow rate is found by the formula, kg / s:

G = Q TO /( h 2D - h 4), (2.3)

Q = c’pm V V ( t IN 2 - t IN 1). (2.4)

Here VВ = 0.61 m 3 / s - capacity of the fan cooling the condenser; t IN 1 , tВ2 - air temperature at the inlet and outlet of the condenser, ºС; c’pm- average volumetric isobaric heat capacity of air, kJ / (m 3 K):

c’pm = (μ c pm)/(μ v 0), (2.5)

where (μ v 0) = 22.4 m 3 / kmol - the volume of a kilo mole of air under normal physical conditions; (μ c pm) Is the average isobaric molar heat capacity of air, which is determined by the empirical formula, kJ / (kmol K):

(μ c pm) = 29.1 + 5.6 · 10 -4 ( t B1 + t IN 2). (2.6)

Theoretical power of adiabatic compression of refrigerant vapors in the process of 1-2 A, kW:

N A = G/(h 2A - h 1), (2.7)

Relative adiabatic and actual refrigerating capacities:

k A = Q/N A; (2.8)

k = Q/N, (2.9)

representing the heat transferred from a cold source to a hot one, per unit of theoretical power (adiabatic) and actual (electric power of the compressor drive). The coefficient of performance has the same physical meaning and is determined by the formula.

All small refrigeration machines produced in our country are freon. They are not mass-produced to operate on other refrigerants.

Fig. 99. Refrigerating machine IF-49M:

1 - compressor, 2 - condenser, 3 - thermostatic valves, 4 - evaporators, 5 - heat exchanger, 6 - sensitive cartridges, 7 - pressure switch, 8 - water expansion valve, 9 - dryer, 10 - filter, 11 - electric motor, 12 - magnetic switch.

Small refrigeration machines are based on the above-mentioned freon compressor-condensing units of the corresponding capacity. The industry produces small refrigeration machines mainly with units with a capacity of 3.5 to 11 kW. These include machines IF-49 (Fig. 99), IF-56 (Fig. 100), XM1-6 (Fig. 101); XMV1-6, XM1-9 (Fig. 102); XMV1-9 (Fig. 103); machines without special brands with AKFV-4M units (Fig. 104); AKFV-6 (Fig. 105).

Fig. 104. Refrigeration machine diagram with AKFV-4M unit;

1 - condenser KTR-4M, 2 - heat exchanger TF-20M; 3 - VR-15 water regulating valve, 4 - RD-1 pressure switch, 5 - FV-6 compressor, 6 - electric motor, 7 - OFF-10a filter-drier, 8 - IRSN-12.5M evaporators, 9 - TRV thermostatic valves -2M, 10 - sensitive cartridges.

Machines with VS-2.8, FAK-0.7E, FAK-1.1E and FAK-1.5M units are also produced in significant quantities.

All these machines are intended for direct cooling of stationary cold rooms and various trade refrigeration equipment catering establishments and grocery stores.

As evaporators, wall-mounted ribbed coil batteries IRSN-10 or IRSN-12.5 are used.

All machines are fully automated and equipped with thermostatic valves, pressure switches and water regulating valves (if the machine is equipped with a water-cooled condenser). Relatively large of these machines - ХМ1-6, ХМВ1-6, ХМ1-9 and ХМВ1-9 - are equipped, in addition, with solenoid valves and chamber temperature switches, one common solenoid valve is installed on the armature shield in front of the liquid manifold, with which you can turn off the supply of freon to all evaporators at once, and the chamber solenoid valves - on the pipelines supplying liquid freon to the cooling devices of the chambers. If the chambers are equipped with several cooling devices and freon is supplied to them through two pipelines (see diagrams), then a solenoid valve is placed on one of them so that not all the cooling devices of the chamber are turned off by means of this valve, but only those that it supplies.