RU2238485C2 - Cooling machine - Google Patents

Abstract

FIELD: refrigeration equipment, particularly carbon dioxide refrigerating plants.

SUBSTANCE: cooling machine has compressor with electric motor arranged in sealed case, heat exchanger, cooler (condenser), throttle valve and evaporator. Above components are included in closed loop of coolant, namely carbon dioxide, circulation. Electric motor stator windings are placed in sealed shell. Sealed case has lower part formed as vessel and supplementary heat exchanged located inside vessel. Supplementary heat exchanger is included in feeding pipeline between compressor and heat exchanger and immersed into liquid poured in lower vessel-shaped case part. Liquid has positive coefficient of thermal volume expansion. Toluene may be used as liquid. Upper case part is provided with connection pipe linked with safety and check valves arranged in parallel one to another and connected to pressure compressor pipeline.

EFFECT: reduced metal consumption of compressor.

2 cl, 2 dwg

Description

The invention relates to refrigeration, in particular to equipment for refrigeration machines, and can be used in carbon dioxide refrigeration machines in all areas of refrigeration applications, including in all branches of the food industry, in air conditioning systems of the chemical and gas industries.

Famous chillers in which compressors equipped with an electric motor and placed in a sealed enclosure are used to prevent refrigerant leaks (see, for example, Jacobson VB Small chillers. - M.: Food industry, 1977).

Numerous modifications are known of the basic structural schemes of compressors with an electric motor placed in a sealed enclosure. So, it is known to use instead of a hermetic casing a compressor crankcase (see, for example, US Pat. No. 5,464,332; US Pat. 5,957,667), wherein the hermetic housing is filled with gas under pressure, while suction is made through a pipe into the compressor housing, after which the suction gas cools the windings electric motor and passes into the suction cavity of the compressor. It is known to use insulated stator windings in sealed vertical reciprocating refrigeration compressors (see, for example, US Pat. 5653125), where the rotor of the drive motor is enclosed in a sealed thin-walled sleeve of small magnetic material located in the gap between the rotor and the open stator, but refrigerant vapor is sucked through the crankcase.

Regardless of the design features of the well-known hermetic compressors operating as part of the refrigeration machine, and having patent protection, the characteristic features of such machines are:

- the compressor maintains a pressure below the boiling pressure of the refrigerant in the internal volume of the sealed enclosure;

- refrigerant vapor from the evaporator of the chiller is sucked into the internal volume of the sealed enclosure;

- cold steam is then used to cool the motor windings;

- in the lower part of the sealed casing is a liquid - lubricating oil, which is used to lubricate the compressor parts;

- the compressor pumps the vapors directly into the condenser of the chiller.

The disadvantages of the known refrigerators equipped with a sealed casing, which is under suction pressure, include the need to create designs designed for differential pressure Rng - Rvs, the value of which can reach values of 20 or more. This leads to a sufficiently large metal consumption of compressors.

In recent years, carbon dioxide (R744) has been rehabilitated as a refrigerant. It is known that DORIN, an Italian manufacturer of compressors, developed the first carbon dioxide machines in 1996 (see DORIN tests 40 prototypes of carbon dioxide compressors. / Holod. Biznes, 2000, No. 5, p.10). Currently, 40 pieces are operating in Europe and the United States. The Dorin development includes 10 single-stage models for temperatures up to minus 20 ° C and 10 two-stage models for temperatures up to minus 40 ° C. The design of the machines differs significantly from compressors designed for other refrigerants, for example R22 or R404A: thicker and durable cast iron housing that allows compressors to operate at a pressure of 3.0 MPa and withstand pressures up to 15.0 MPa (5.5-kilowatt models). Semi-hermetic reciprocating compressors of this company, developed specifically for the R744 with the scientific assistance of the University of Oslo (Norway), made Dorin customers submarine fleets in the USA, England, Germany and other countries, Norwegian oil producers, i.e. such facilities where equipment with a high degree of fire safety is necessary.

Requirements for the design of modern semi-hermetic compressors on the R744, as well as special safety measures are considered in the work: Koptelov KA. Semi-hermetic piston and screw compressors for cascade CO ₂ refrigeration systems. // Compressor technology and pneumatics - 2001, No. 1, - p. 11-12 /. It is noted that semi-hermetic compressors when working on R744 due to high loads should have a more solid structure and some design features due to high loads on the bearings and bending loads on the crankshaft. The casing must be made with a fivefold safety margin in pressure. An additional potential for increasing working pressure when using the standard wall thickness of the compressor housing is provided by replacing lamellar cast iron with spherical cast iron. But this requires special execution of a number of body parts and is associated with a significant increase in the cost of the compressor. The cooling of the electric motor by the suction pairs of R744 is quite intensive, but due to the need to create powerful built-in electric motors, the serial semi-hermetic compressors on R22, as the basis for creating similar semi-hermetic compressors on R744, can be realized only in very rare cases.

Thus, the existing technical solutions do not allow to effectively solve the problem that has arisen - the creation of refrigeration machine compressors when working mainly on R744, characterized by low metal consumption and the ability to use the existing compressor engineering base to create new machines, including those working on R744.

The present invention aims to reduce the metal consumption of a refrigeration compressor by creating a pressure in the sealed casing equal to or greater than the compressor discharge pressure.

This object is achieved by the fact that according to the claimed invention, the refrigeration machine contains in a closed circuit the refrigerant, mainly carbon dioxide, a compressor with an electric motor, placed in a sealed casing, a heat exchanger, a cooler (condenser), a throttle valve and an evaporator, while the stator windings of the electric motor are placed in a sealed sleeve, a sealed casing is made in the lower part in the form of a container into which an additional heat exchanger is placed, and an additional heat exchanger is introduced in the discharge line between the compressor and the heat exchanger, the upper part of the casing is equipped with a nozzle connected to parallel mounted safety and non-return valves connected to the compressor discharge pipe, and the additional heat exchanger is immersed in the liquid filling the lower part of the casing in the form of a container, and this liquid is characterized by positive values volume expansion coefficient versus temperature, for example toluene.

The implementation of a sealed casing in the lower part in the form of a container, in which an additional heat exchanger is placed, which is introduced into the discharge line between the compressor and the heat exchanger and immersed in the liquid filling the lower part of the casing in the form of a container, and this liquid is characterized by positive values of the coefficient of volume expansion from temperature, allows during the operation of the compressor and increasing the discharge temperature to increase the vapor pressure above the liquid due to the volume expansion of the liquid from heating. In this case, the vapor pressure in the volume between the inner surface area of the casing and the outer surface of the compressor and the sealed sleeve increases to a value equal to or greater than the compressor discharge pressure.

Equipping the upper part of the casing with a nozzle connected to parallel mounted safety and non-return valves with the compressor discharge pipe ensures that the volume between the inner surface of the casing and the outer surface of the compressor maintains the initial pressure equal to the refrigerant vapor pressure when the compressor is stopped, and the excess steam pressure is relieved from this volume when the discharge temperature is higher than the calculated value.

The placement of the stator winding of the compressor motor in a sealed sleeve provides cooling of the windings with low pressure suction steam.

Figure 1 shows a schematic diagram of a refrigeration machine equipped with a compressor placed in an airtight casing; figure 2 - graphs of the change in the volume of fluid V in the capacity of the casing and the pressure P in the casing from the discharge temperature Tg of the refrigerant after the compressor.

The refrigeration machine (Fig. 1) contains in a closed circuit the circulation of refrigerant, mainly carbon dioxide, a compressor 1 with an electric motor, a heat exchanger 2, a cooler (condenser) 3, a throttle valve 4 and an evaporator 5. The stator windings of the compressor motor 1 (not shown conventionally) placed in a sealed sleeve 6, the compressor 1 with an electric motor placed in a sealed casing 7.

The suction pipe 8 passes through a sealed casing 7 and is inserted into a sealed sleeve 6.

The sealed casing 7 is made in the lower part in the form of a container 9, in which an additional heat exchanger 10 is placed, which is introduced into the discharge line 11 between the compressor 1 and the heat exchanger 4. The upper part of the casing 3 is equipped with a pipe 12 connected to a parallel mounted safety 13 and check valve 14 with the compressor discharge pipe 11, and an additional heat exchanger 10 is immersed in the liquid 15 filling the lower part of the casing 7 in the form of a container 9. This liquid is characterized by positive values of the volumetric coefficient about expansion from temperature, for example, toluene, which has an inherent coefficient of volume expansion α = 109.9 · 10 ^-5 1 / deg (see the Mechanical Engineering Manual, vol. 2. Ed. 3. / Ed. Acerkana /. - M .: Mashgiz, 1960).

The refrigeration machine (figure 1 and 2) operates as follows.

After starting the electric motor, compressor 1 lowers the pressure in the sealed sleeve 6. From the evaporator 5, refrigerant vapor flows through the pipe 8 into the cavity of the sleeve 6, cools the stator windings of the electric motor (not shown conditionally) and then is sucked into the compressor 1. Compressed refrigerant vapor from compressor 1 enters heat exchanger 10, then sequentially pass through the discharge pipe 11 to the heat exchanger 2, then to the cooler 3; then the refrigerant through the throttle valve 4 is returned to the evaporator. The work cycle is ending.

At the beginning of the compressor 1 from the pipeline 11 through the check valve 14 and the pipe 12, the refrigerant vapor enters the volume between the inner surface area of the casing 7 and the outer surface of the compressor 1 and the sealed sleeve 6. The vapor pressure of the refrigerant in this volume is equal to the discharge pressure.

Since the temperature Tg of the refrigerant vapor injected by the compressor 1 is higher than the ambient temperature Tos, the liquid 15 filling the lower part of the casing 7 in the form of a container 9 and having a volume V ₀ begins to heat up. Due to the increase in temperature with a positive value of the coefficient of volume expansion α on temperature, in accordance with the well-known dependence Vj = V ₀ · (1 + α · Δ t), the liquid volume increases to Vj. This reduces the volume occupied by refrigerant vapor in the volume between the inner surface area of the casing 7 and the outer surface of the compressor 1 and the sealed sleeve 6. In this case, the vapor pressure Pj in the volume between the inner surface area of the casing 7 and the outer surface of the compressor 1 and the sealed sleeve 6 increases to , greater discharge pressure Rng compressor. When the vapor pressure Pj reaches a value of Rpc, for example, corresponding to point A (figure 2), set as the maximum allowable, the safety valve 13 is activated and the vapor with excess pressure is discharged into the discharge pipe 11.

When the compressor 1 stops and the liquid is cooled to Tos, the volume occupied by the liquid in the volume between the inner surface area of the casing 7 and the outer surface of the compressor 1 and the sealed sleeve 6 decreases and the pressure Pj decreases to the value Png. The work cycle is ending.

Thus, the inventive refrigeration machine, shown in figure 1 and ensuring the flow of processes according to figure 2 in the volume between the inner surface area of the casing 7 and the outer surface of the compressor 1 and the sealed sleeve 6, in comparison with the known one reduces the metal consumption of the compressor by reducing the pressure drop between the compressor parts and the environment surrounding the compressor due to the equality of the pressures Pj and Png (or a slight excess of the pressure Pj = Ppc relative to the pressure Png).

Claims (2)

1. The chiller, containing in a closed circuit the circulation of refrigerant, mainly carbon dioxide, a compressor with an electric motor, placed in a sealed casing, a heat exchanger, a cooler (condenser), a throttle valve and an evaporator, characterized in that the stator windings of the electric motor are placed in a sealed sleeve, sealed the casing is made in the lower part in the form of a container in which an additional heat exchanger is placed, while an additional heat exchanger is introduced into the discharge line between the compressor and the heat exchange nickname, the upper housing portion is equipped with a branch pipe, connected in parallel with the established safety and non-return valve connected to the discharge line of the compressor and a further heat exchanger immersed in the liquid filling the lower part of the casing in a container form. 2. The refrigeration machine according to claim 1, characterized in that the lower part of the casing in the form of a container is filled with a liquid characterized by positive values of the coefficient of volume expansion from temperature, for example, toluene.

Images