JPS59211790A - Refrigerating plant - Google Patents

Abstract

PURPOSE:To aim at the improvement of efficiency in a low partial load range, by adding a capacity control system using an inverter to a stageless capacity control mechanism by means of a slide valve. CONSTITUTION:Capacity control by means of a slide valve 9 is adjusted in a range of about 25-100% at stageless capacity. When the slide valve 9 exists in a position of 100-75% with a switch 12, it is driven by a commercial power source without passing an inverter 10, and when the slide valve 9 reaches to the range of 50%, it is used with power frequency with power frequency raised high at a position of the switch 12 shown in illustration via the inverter 10. In time of using the commercial power source of 60Hz as usual, when the slide valve 9 exists in a position of 50-25%, power frequency of a motor 7 is raised up to 90Hz or so, and it is used with the number of revolution in a rotor 8 accelerated up to about 5,000r.p.m. whereby a refrigerator is operated in the state that efficiency of a compressor is heightened as much as by about 5-10%. With this constitution, a sharp improvement in the efficiency of operation in time of partial load is made possible.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a configuration suitable for a method for improving a capacity control mechanism in all areas of the capacity control range of a refrigeration system using a hermetic screw compressor.

[Background of the invention]

A conventional method for controlling the capacity of a screw compressor is a partial load operation method using an O induction motor directly connected to a commercial power source. For this reason, the limit for full load operation is 100 g, and the practical lower limit for minimum capacity control operation is 20 to 259 g. Conventionally, a slide valve was moved between this time,
Stepless control is the mainstream, but during partial load operation,
As shown in FIG. 2, the problem was that the refrigeration effect of the unit input screen, that is, the reduction in efficiency, was large especially when operating at a load of 50 to 251. For example, in Fig. 2, to draw out the cooling capacity of 30 inches, 40 inches of power consumption is required, and the efficiency decreases to 30/40 = 75% of the efficiency when operating 100 inches (assumed to be 100). It has the disadvantage that it consumes a large amount of electricity during low partial load operation.

[Purpose of the invention]

This invention has been made based on the above-mentioned achievements, and aims to provide a screw type refrigeration system that improves efficiency particularly in the low partial load region of the partial load operation characteristics of screw compressors, which have been considered to be disadvantageous in the past. be.

[Summary of the invention]

The characteristic feature of this invention is that the screw compressor has two
Operates at commercial frequency (50/60 °C) using a polar motor.
2880/3470 r-p-m) at lx), we focused on the fact that efficiency would be improved by further increasing the speed and operating at approximately 500 or-p-m. The purpose is to add a capacity control method using an inverter to the capacity control mechanism to perform increased speed operation at low loads.

Here, when the load factor of the refrigerator is from 100 to 75 inches, the partial load characteristics of the refrigerator are good even at the compressor rotational speed due to the commercial power frequency, so the conventional stepless capacity control method using a slide valve is adopted. The purpose of this is to keep the maximum capacity of the inverter to about 75 inches, which is the motor capacity when the compressor is operated with a load of 100 inches, and to increase speed only in the low partial load region using a relatively inexpensive low capacity inverter. That is. Table 1 shows these relationships. Table 1 shows the relationship between the position of the slide valve of the compressor, the usage range of the inverter, and the load factor and efficiency of the refrigerator.

By selectively using the speed-up operation using the inverter depending on the position of the slide valve, the efficiency can be increased to a refrigerator load factor of 100 to 37.
．． It can be seen that the improvement is achieved in all areas of 5%.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be explained in more detail with reference to FIG.

In the refrigeration cycle shown in FIG. 1, high-temperature, high-pressure refrigerant gas discharged from a hermetic screw compressor 1 radiates heat to a condenser 2 and cooling water 3, where it is condensed and liquefied. The liquefied high-pressure liquid refrigerant is adiabatically reduced in pressure in a pressure reducing device 4 to become a low-temperature, low-pressure saturated liquid refrigerant, which is led to an evaporator 5 where it absorbs heat from the cold water 6 and evaporates into gas. In the evaporator 5, the cold water 6 is cooled to a desired temperature and exhibits the desired cooling effect. The gas refrigerant leaving the evaporator 5 is sucked into the compressor 1, and the same cycle is repeated again. Now, the screw compressor 1 includes a pair of screw rotors 8 driven by an electric motor 7.
The refrigerant gas is compressed by passing between the rotor and the rotor. The compression capacity of the compressor is determined by adjusting the effective length of the rotor using a slide valve 9. Capacity control by the slide valve is steplessly adjusted in a range of about 25 to 100%. Power for the electric motor 7 is supplied from a commercial power source 11, but a switch 12 and a slide valve 10
When the slide valve is at a position of 0 to 75 inches, it is driven by commercial power without going through the inverter 10, and when the slide valve reaches 50 inches, the power frequency is increased via the inverter 10 at the switch position shown in the figure. and use it. Normally, when using a commercial power supply of 60) Iz, when the slide valve is in the 50 to 25% position, the power frequency of the motor 7 is increased to about 9 (] Hz, and the rotation speed of the rotor 8 is increased to about 500 Or-p. - m, and the refrigerator is operated with the efficiency of the compressor improved by approximately 5 to 10 inches.These relationships are explained using the partial load characteristic diagram in Figure 3.In Figure 3, the curve ■ is 347
When operating at 0 r-p-m, curve ■ is 500 Or
When operating at -p-m, the higher the rotation speed, the better the efficiency is by about 10 cm. Use this to adjust the slide valve position to 50~
At 25% load, the speed increases to 5,000 revolutions (approximately 165 times when using commercial power)6, and the discharge amount of the compressor is approximately 1.
Because it will be 5 times (50-25%) xl, 5÷75-37
．． The refrigerator can be operated with a refrigeration capacity of 5q6, and can be used in an efficient operation range (below the 45° diagonal line). Further, in FIG. 3, the point ◎ indicates the minimum unload at the time of starting to reduce the starting load.

〔Effect of the invention〕

As described above, according to the present invention, the value of the operating vehicle during partial load is improved over the entire range of capacity control of the compressor compared to the value during full load (100% load) operation, resulting in energy savings throughout the year. Effects can be obtained. In addition, in order to limit the range of use of the inverter to an area that is 75 times smaller than the load of the refrigerator,
The required inverter capacity can be reduced in size, and the refrigerator can be manufactured at a lower cost than by using an inverter-based speed increasing mechanism over the entire range.

[Brief explanation of the drawing]

FIG. 1 shows a refrigeration cycle system diagram according to the present invention. Second
The figure shows a partial load characteristic diagram of a conventional screw type refrigerator.
FIG. 3 shows a partial load characteristic diagram when using the partial load operation method of the present invention. Furthermore, FIG. 4 shows the relationship between the position of the compressor capacity control slide valve, the inverter use range, and the refrigerator load factor and efficiency when using the partial load operation method of the present invention. 1...Hermetic screw compressor 2...Condenser 3
... Cooling water 4 ... Pressure reducing device 5 ... Evaporator 6 ... Chilled water 7 ... Electric motor 8 ... Screw rotor 9 ... Slide valve 10 - ... Inverter 11 ... Commercial power supply 12...Power switch agent patent attorney Akio Takahashi/Tsu)

Claims (1)

[Claims] 1. In a refrigeration system consisting of a hermetic screw compressor, a condenser, a pressure reducing device, an evaporator, and their connecting conduits, the capacity control mechanism of the screw compressor has a stepless slide valve. A time-sharing stroke control mechanism is provided, and an inverter rotation speed control mechanism powered by a commercial power source is installed on the compressor's conductive motor, which is directly connected to the compressor. Machine capacity 10θ~1
In the capacity control range of 5-, partial load operation is performed using only the slide valve, and in the capacity control range of 75 to 37.5 inches, the system compressor rotation speed is increased by approximately 1.5 times using an inverter. Increase the speed and use the slide valve in the range of 50 to 25 inches, the entire range of capacity control (100 to 37.5 inches)
A refrigeration system characterized by performing stepless capacity control operation with efficiency better than that of operation under 100% load. 2. Claim 1, characterized in that when starting the compressor, the slide valve is set to the minimum capacity control position, and the inverter is started at the minimum rotation speed to reduce the current value at the time of starting.
Refrigeration equipment as described in section.