JP2011149565A - Refrigerating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a refrigerating device having a two-stage screw compressor (hereinafter called compressor) having a discharge gas temperature lower than an allowable upper limit temperature, and capable of improving performance. <P>SOLUTION: This refrigerating device includes a refrigerant circuit configured by successively annularly connecting the compressor 1, an oil separator 2, a condenser 3, a supercooler 5 for cooling a refrigerant, an expansion valve 6 and an evaporator 7 by refrigerant pipes, an oil returning pipe conduit for returning a lubricant from the oil separator 2 to the compressor 1 through an oil cooler 9, a liquid refrigerant injection pipe conduit having an electronic expansion valve 13 for returning the liquid refrigerant from the condenser to an intermediate pressure chamber of the compressor 1 through the oil cooler 9 and controlling a flow rate of a liquid refrigerant for cooling the lubricant in the oil cooler 9, and a temperature sensor 14 detecting a temperature of a discharge-side refrigerant gas of the compressor 1. A microcomputer 12 controls opening/closing of the electronic expansion valve 13 so that an output of the temperature sensor 14 is kept at the predetermined allowable upper limit temperature and near the upper limit temperature over a range of operable condition. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a refrigeration apparatus having a two-stage screw compressor that compresses a refrigerant.

In a refrigeration system having a two-stage screw compressor, in order to prevent deterioration of refrigerant, lubricating oil, and components due to an increase in discharge gas temperature, the refrigeration that can be operated at a discharge gas temperature below an allowable upper limit temperature for such deterioration. Configure the cycle and control the operation. For this purpose, it is necessary to cool the refrigerant gas being compressed. As a means for this, it is common to equip the refrigeration apparatus with an oil cooler. The oil cooler is a heat exchanger that cools the lubricating oil injected into the compressor. There are a water cooling system that cools the lubricating oil using water and a refrigerant cooling system that cools the lubricating oil using a refrigerant. is there. In the case of the refrigerant cooling system, the refrigerant used for oil cooling is gasified after heat exchange with the oil cooler and injected into the compressor. At this time, there is a method of controlling the amount of refrigerant using a temperature type expansion valve so that the lubricating oil temperature or the refrigerant gas superheat degree after cooling the lubricating oil becomes a predetermined value. (For example, see Patent Document 1)
FIG. 4 is a refrigerant circuit diagram of a refrigeration apparatus having the conventional two-stage screw compressor disclosed in Patent Document 1. This type of refrigerant circuit will be described with reference to FIG. 4, and the main part Y in FIG. 4 will be described with reference to FIGS. The arrows in the figure indicate the flow directions of refrigerant and oil. The refrigerant is discharged as high-temperature and high-pressure gas in the compressor 1 and separated into refrigerant gas and lubricating oil in the oil separator 2. The refrigerant gas becomes a condensate in the condenser 3, and the liquid temperature is lowered in the subcooler 5. Further, the refrigerant gas becomes a low-pressure wet gas by the expansion valve 6 and is evaporated by exchanging heat with air in the evaporator 7. After cooling, the low-stage compression mechanism 1a of the compressor 1 is injected. A part of the main liquid flow whose liquid temperature has been lowered by the subcooler 5 flows through the motor cooling expansion valve 8 and is injected into the motor chamber 1 d for motor cooling of the compressor 1.
On the other hand, the lubricating oil separated by the oil separator 2 is cooled by the oil cooler 9 and injected into the compressor intermediate pressure chamber 1 c of the compressor 1. The cooling system for the lubricating oil in the oil cooler 9 is a refrigerant cooling system using a refrigerant.
The high-pressure liquid refrigerant from the condenser 3 is branched in two directions on the way to the supercooler 5, and the main liquid flow cooled in the above-described supercooler 5 and the temperature-type expansion that is the expansion valve for the oil cooler. The valve 10 is changed into a saturated wet gas having a low temperature and an intermediate pressure at a low temperature, and the lubricating oil from the oil separator 2 is cooled by the oil cooler 9. The refrigerant gas flowing through the expansion valve 4 and the subcooler 5 and the refrigerant gas flowing through the temperature-type expansion valve 10 and the oil cooler 9 are mixed with the low-stage discharge gas in the compressor intermediate pressure chamber 1c, and are fed to the high-stage compression mechanism 1b. Inhaled.
A method of controlling the lubricating oil temperature to a predetermined value and a method of controlling the refrigerant gas superheat degree to a predetermined value will be described with reference to FIGS.
When the amount of refrigerant is controlled so that the lubricating oil temperature after cooling the lubricating oil becomes a predetermined value, the temperature sensing cylinder 11 detects the lubricating oil temperature after cooling the lubricating oil as shown in FIG. The refrigerant quantity is controlled using the temperature type expansion valve 10 so that the temperature of the lubricating oil becomes a predetermined value.
When controlling the amount of refrigerant so that the degree of refrigerant gas superheat after cooling of the lubricating oil becomes a predetermined value, as shown in FIG. 6, the temperature sensing cylinder 11 is the refrigerant gas temperature after cooling the lubricating oil, and the pressure equalizing pipe 17 is lubricated. The pressure of the refrigerant gas after oil cooling is detected, and the amount of refrigerant is controlled using the temperature type expansion valve 10 so that the degree of refrigerant gas superheat after cooling the lubricating oil becomes a predetermined value.

Japanese Patent Laid-Open No. 2002-31420 (page 5, FIGS. 2 to 5)

(1) Description of problems in the prior art In the conventional refrigeration apparatus described in the above-mentioned Patent Document 1, since the operable condition range is wide, after cooling the lubricating oil in accordance with the condition that the discharge gas temperature is highest in the operating range. Set lubricant temperature or refrigerant gas superheat. This method is a conventional general method. For this reason, the amount of refrigerant used for cooling the lubricating oil and injected into the compressor becomes excessive except under the conditions set above. Thereby, the fall of the refrigerating capacity, the increase in input generate | occur | produced, and the subject that performance fell occurred.

  In addition, when the lubricating oil is supercooled due to the excessive refrigerant amount and a large amount of refrigerant is dissolved in the lubricating oil, the oil separation efficiency is reduced, and the amount of lubricating oil flowing out from the oil separator to the condenser is reduced. Increased risk of oil spilling. There was a case where the refrigerator broke down due to the occurrence of oil rising. It should be noted that the oil does not always rise when a large amount of refrigerant dissolves in the lubricating oil.

(2) Description of the object of the invention The present invention has been made to solve the above-described problems, and is a two-stage screw capable of improving performance when the discharge gas temperature is not more than the allowable upper limit temperature. An object is to obtain a refrigeration apparatus having a compressor.

A refrigeration apparatus according to the present invention includes a two-stage screw compressor having a low-stage compression section, a high-stage compression section, and an intermediate pressure chamber located between both compression sections, an oil separator, and a condenser. A refrigerant circuit in which a subcooler for cooling the refrigerant, an expansion valve, and an evaporator are sequentially connected in an annular manner with refrigerant pipes, and lubricating oil is returned from the oil separator to the two-stage screw compressor via the oil cooler. Liquid refrigerant having an oil return line and a flow rate adjusting mechanism for returning the liquid refrigerant from the condenser to the intermediate pressure chamber via the oil cooler and controlling the flow rate of the liquid refrigerant for cooling the lubricating oil by the oil cooler A pipe for injection, a temperature sensor for detecting the temperature of the refrigerant gas on the discharge side of the two-stage screw compressor,
And a control unit that controls the flow rate adjusting mechanism so that the output of the temperature sensor is equal to or lower than a predetermined allowable upper limit temperature over the entire operating condition range and is close to the upper limit temperature.

  A refrigeration apparatus according to the present invention includes a two-stage screw compressor having a low-stage compression section, a high-stage compression section, and an intermediate pressure chamber positioned between both compression sections, an oil separator, a condenser, A refrigerant circuit in which a subcooler that cools the refrigerant, an expansion valve, and an evaporator are sequentially connected in a ring with a refrigerant pipe, and oil that returns lubricating oil from the oil separator to the two-stage screw compressor via the oil cooler Liquid refrigerant injection having a return line and a flow rate adjusting mechanism for controlling the flow rate of the liquid refrigerant for returning the liquid refrigerant from the condenser to the intermediate pressure chamber via the oil cooler and cooling the lubricating oil by the oil cooler Pipeline, a temperature sensor for detecting the temperature of the refrigerant gas on the discharge side of the two-stage screw compressor, and the output of this temperature sensor is below a predetermined allowable upper limit temperature over the entire operating condition range, and near the upper limit temperature And a control unit for controlling the flow rate adjusting mechanism to be Since, in the prior art since the there is no injection of excess refrigerant in the operable condition amount of refrigerant is excessive, thereby improving the performance.

It is a refrigerant circuit diagram of the refrigeration apparatus in Embodiment 1 of the present invention. It is a principal part refrigerant circuit figure of the freezing apparatus in Embodiment 1 of this invention. It is a principal part refrigerant circuit figure of the freezing apparatus in Embodiment 2 of this invention. It is a refrigerant circuit figure of the refrigerating device of the conventional invention. It is a principal part refrigerant circuit figure of the method of controlling the lubricating oil temperature after the lubricating oil cooling in the refrigerating device of the conventional invention to a predetermined value. It is a principal part refrigerant circuit figure of the method of controlling the refrigerant gas superheat degree after lubricating oil cooling in the refrigerating device of the conventional invention to a predetermined value.

Hereinafter, Embodiment 1 of the present invention will be described with reference to the drawings.
The overall refrigerant circuit is almost the same as that shown in FIG. 4 described in the background art section, so detailed description is omitted and only different parts will be described.
In the present invention, the main part Y of the circuit shown in FIG. 4 is a refrigerant circuit as shown in FIGS.

Embodiment 1 FIG.
(1.1) Detailed Description of Configuration FIG. 1 is a refrigerant circuit diagram illustrating a refrigeration apparatus according to Embodiment 1 of the present invention.
In the figure, the same reference numerals as those in FIG. The overall refrigerant circuit of FIG. 1 is almost the same as that of FIG. 4 described in the background art section, so detailed description is omitted and only different parts will be described.
FIG. 2 is a principal refrigerant circuit diagram of the refrigeration apparatus in Embodiment 1 of the present invention. The temperature of the discharge gas is detected by the temperature sensor 14, and the microcomputer (hereinafter referred to as a microcomputer. This microcomputer constitutes a control unit) 12 so that the discharge gas temperature is equal to or lower than the allowable upper limit temperature and close to the upper limit temperature. Sends a signal to the electronic expansion valve 13 to control the amount of refrigerant used for cooling the lubricating oil.
The electronic expansion valve 13 constitutes a flow rate adjusting mechanism that adjusts the flow rate of the refrigerant.

(1.2) Detailed Description of Operation and Effect In the refrigeration apparatus configured as described above, the discharge gas temperature is detected, and the discharge gas temperature is equal to or lower than the allowable upper limit temperature and is close to the upper limit temperature. The microcomputer 12 controls the opening and closing of the electronic expansion valve 13 to control the amount of refrigerant used for cooling the lubricating oil.
Thereby, according to this Embodiment 1, compared with the conventional method of controlling the amount of refrigerant using a temperature type expansion valve so that the lubricating oil temperature after cooling the lubricating oil or the refrigerant gas superheat degree becomes a predetermined value, The refrigerant is not excessively injected over the entire operable condition range, and the performance of the refrigeration apparatus is improved.
Moreover, since overcooling of the lubricating oil can be suppressed, a large amount of refrigerant is difficult to dissolve in the lubricating oil, and the risk of oil rising is reduced. Thereby, failure of the refrigeration apparatus due to oil rising can be prevented, and a highly reliable refrigeration apparatus can be obtained.

Embodiment 2. FIG.
(2.1) Detailed Description of Configuration In the second embodiment, the configuration of the main part in FIG. 1 is the same except that the configuration of FIG. 2 is changed to the configuration of FIG.
FIG. 3 shows a main refrigerant circuit according to the second embodiment. In the first embodiment, the microcomputer 12 is controlled using the electronic expansion valve 13, whereas in the second embodiment, the microcomputer 12 is controlled using at least one set of the capillary tube 15 and the electromagnetic valve 16.
The temperature sensor 14 detects the discharge gas temperature, and the microcomputer 12 controls the opening and closing of at least one electromagnetic valve 16 so that the discharge gas temperature is equal to or lower than the allowable upper limit temperature and close to the upper limit temperature, whereby the capillary tube 15 and controls the amount of refrigerant used for cooling the lubricating oil.
(2.2) Effect According to the second embodiment, the same effect as in the first embodiment is obtained.
The solenoid valve 16 and the capillary tube 15 constitute a flow rate adjusting mechanism that adjusts the flow rate of the refrigerant.

  1 Compressor, 1a Low stage compression mechanism, 1b High stage compression mechanism, 1c Compressor intermediate pressure chamber, 1d Motor chamber, 2 Oil separator, 3 Condenser, 4 Intercooler expansion valve, 5 Supercooler, 6 Main Liquid expansion valve, 7 Evaporator, 8 Motor cooling expansion valve, 9 Oil cooler, 10 Temperature type expansion valve, 11 Temperature sensitive cylinder, 12 Microcomputer, 13 Electronic expansion valve, 14 Temperature sensor, 15 Capillary tube, 16 Solenoid valve 17 Pressure equalizing pipe.

Claims (3)

A two-stage screw compressor having a low-stage compression section, a high-stage compression section, and an intermediate pressure chamber located between these compression sections, an oil separator, a condenser, and a supercooler that cools the refrigerant A refrigerant circuit in which an expansion valve and an evaporator are sequentially connected in a ring shape with a refrigerant pipe,
An oil return line for returning lubricating oil from the oil separator to the two-stage screw compressor via an oil cooler;
Liquid refrigerant from the condenser is returned to the intermediate pressure chamber via the oil cooler, and liquid refrigerant injection has a flow rate adjusting mechanism for controlling the flow rate of the liquid refrigerant that cools the lubricating oil by the oil cooler. A pipeline,
A temperature sensor for detecting the temperature of the refrigerant gas on the discharge side of the two-stage screw compressor;
A control unit that controls the flow rate adjusting mechanism so that the output of the temperature sensor is equal to or lower than a predetermined allowable upper limit temperature over the entire operating condition range and close to the upper limit temperature. apparatus.   The refrigeration apparatus according to claim 1, wherein the flow rate adjusting mechanism is an electronic expansion valve, and the control unit controls opening and closing of the electronic expansion valve.   2. The flow rate adjusting mechanism includes at least one set of a solenoid valve and a capillary tube, and the control unit controls opening and closing of the at least one solenoid valve. Refrigeration equipment.

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