JPH05149652A - Pressure reducing device - Google Patents

Abstract

PURPOSE:To improve efficiency of a nozzle by providing one or more throttling means upstream of a nozzle of a pressure reducing device to allow a fluid to pass through said means in such a manner that the fluid is in a state of low compressibility, thereby reducing the pressure thereof, so that the fluid is kept in a gas-liquid two-phase state at the entrance of the nozzle. CONSTITUTION:An ejector 4 comprises a first nozzle 4a for reducing the pressure of liquid refrigerant R1 introduced from a refrigerant condenser 3, a second nozzle 4b for blowing off the refrigerant whose pressure has been reduced, and a diffuser 4c for diffusing the refrigerant. The pressure of high pressure liquid refrigerant R1 condensed at the condenser 3 is reduced at the nozzle 4a so that the refrigerant R1 is turned into a refrigerant R2 of gas-liquid two-phase, which is blown off from the nozzle 4b and mixed with a gas refrigerant R4 drawn from a suction port 4d and the pressure of the mixture is raised at the diffuser 4c. The refrigerant is separated into gas refrigerant and liquid refrigerant at a separator 5 to send the former R7 to a compressor 2 and the latter R6 to an evaporator 6. By reducing the pressure of the liquid refrigerant to expand it at the nozzle 4a, thereby turning the refrigerant into a two-phase state at the entrance of the nozzle 4b, nozzle efficiency is improved and suction capacity of the ejector 4 is increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure reducing device having a nozzle for ejecting a fluid.

[0002]

2. Description of the Related Art Conventionally, in a vehicle air conditioner, a refrigeration cycle provided with an ejector for depressurizing the condensed refrigerant has been used. The ejector is arranged downstream of the refrigerant condenser and includes a nozzle for ejecting the refrigerant introduced from the refrigerant condenser and a diffuser for diffusing the refrigerant ejected from the nozzle. In this ejector, the nozzle efficiency is significantly reduced when the refrigerant introduced into the nozzle inlet is a liquid single phase. Therefore, for example, Japanese Patent Laid-Open No. 3-5674 discloses a technique of promoting a phase change in the nozzle by exchanging heat between the fluid inside the nozzle and the low temperature fluid.

[0003]

However, in the above-mentioned prior art, the device for exchanging heat between the fluid in the nozzle and the low temperature fluid becomes complicated, and like the refrigeration cycle for vehicles,
There is a problem that it is not suitable when the mounting space is limited. The present invention has been made based on the above circumstances, and an object thereof is to provide a small-sized and high-performance pressure reducing device.

[0004]

In order to achieve the above object, the present invention provides a decompression device having a nozzle for ejecting a fluid, wherein one or more throttle portions are provided upstream of the nozzle, The technical means is to make the inlet state of the nozzle into a gas-liquid two-phase state by reducing pressure by passing through the narrowed portion in a state of low compressibility.

[0005]

In the decompression device of the present invention having the above-described structure, the inflowing fluid having a low compressibility is decompressed by the throttle portion provided on the upstream side of the nozzle, and the gas inlet and the nozzle are in the two-phase state.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the pressure reducing device of the present invention will be described with reference to FIGS. FIG. 1 is a cross-sectional view of an ejector which is a pressure reducing device of the present invention, and FIG. 2 is a refrigeration cycle diagram.
The refrigeration cycle 1 is used for a vehicle air conditioner and, as shown in FIG. 2, is composed of respective functional components of a refrigerant compressor 2, a refrigerant condenser 3, an ejector 4, a separator 5, and a refrigerant evaporator 6. ing.

The refrigerant compressor 2 is driven by a vehicle running engine (not shown) via an electromagnetic clutch (not shown), and compresses and discharges the sucked gas refrigerant. The refrigerant condenser 3 receives the air blown from the cooling fan 7 and condenses and liquefies the high-temperature, high-pressure gas refrigerant discharged from the refrigerant compressor 2. As shown in FIG. 1, the ejector 4 ejects the first nozzle 4a (the throttle portion of the present invention) that decompresses the liquid refrigerant guided from the refrigerant condenser 3 and the refrigerant that is decompressed by the first nozzle 4a. It comprises a second nozzle 4b and a diffuser 4c for diffusing the refrigerant ejected from the second nozzle 4b.
A suction port 4d is provided on the side surface of the ejector 4,
The suction port 4d is connected to the outlet of the refrigerant evaporator 6 via the refrigerant pipe 8.

The separator 5 is arranged downstream of the ejector 4 and separates the gas-liquid two-phase refrigerant flowing out of the ejector 4 into a gas refrigerant and a liquid refrigerant. The gas refrigerant separated by the separator 5 is sucked into the refrigerant compressor 2 via the refrigerant pipe 9, and the liquid refrigerant is supplied to the refrigerant evaporator 6 via the refrigerant pipe 10. The refrigerant evaporator 6 evaporates the refrigerant by heat exchange between the low-temperature low-pressure refrigerant and the air in the vehicle interior. The air cooled by heat exchange with the refrigerant is blown into the vehicle compartment by receiving the air blow from the blower 11. Further, the gas refrigerant vaporized in the refrigerant evaporator 6 is sucked into the ejector 4 through the suction port 4d due to the pressure drop in the ejector 4, is mixed with the refrigerant ejected from the second nozzle 4b, and is pressurized by the diffuser 4c.

Next, the operation of this embodiment will be described. next,
The operation of this embodiment will be described with reference to the Mollier diagram shown in FIG. This Mollier diagram depicts the operating points of the refrigeration cycle 1. The refrigerant states of R1 to R8 on the refrigeration cycle 1 shown in FIG. 2 are changed to R1 to R8 on the Mollier diagram shown in FIG. Corresponding. The high-temperature, high-pressure gas refrigerant (R8) compressed by the refrigerant compressor 2 is condensed and liquefied (R1) by exchanging heat with the vehicle outside air in the refrigerant condenser 3. This condensed and liquefied high-pressure liquid refrigerant is
When the pressure is reduced by the first nozzle 4a of the ejector 4, it becomes a gas-liquid two-phase state (R2). The gas-liquid two-phase refrigerant is mixed with the gas refrigerant (R4) ejected from the second nozzle 4b (R3) and sucked from the suction port 4d, and is pressurized by the diffuser 4c (R5).

The gas-liquid two-phase refrigerant flowing out from the ejector 4 is separated by the separator 5 into a gas refrigerant and a liquid refrigerant.
The separated gas refrigerant (R7) is sucked into the refrigerant compressor 2 and the liquid refrigerant (R6) is supplied to the refrigerant evaporator 6. Then, the gas refrigerant (R4) that has been heat-exchanged with the vehicle interior air in the refrigerant evaporator 6 and evaporated is again sucked into the ejector 4.
In the above operation, the higher the nozzle efficiency of the ejector 4, that is, the higher the outlet speed of the refrigerant ejected from the second nozzle 4b, the more the refrigerant suction action (suction of the gas refrigerant vaporized in the refrigerant evaporator 6) increases. Therefore, when the relationship between the refrigerant state at the inlet of the second nozzle 4b and the nozzle efficiency is examined, it is found that the gas-liquid two-phase has better nozzle efficiency than the liquid single-phase, as shown in FIG. In FIG. 4, x: dryness, sc: supercooling degree.

This will be described below. The nozzle efficiency is proportional to the square of the outlet speed of the second nozzle 4b, as shown in the following equation.

[0012]

[Equation 1]

The outlet speed of the second nozzle 4b is determined by the volumetric flow rate of the fluid when the weight flow rate of the fluid flowing in the second nozzle 4b and the outlet diameter of the second nozzle 4b are constant, and the volumetric flow rate is large. At this time, the outlet speed of the second nozzle 4b becomes high. To increase the volumetric flow rate, the second nozzle 4
It is necessary to sufficiently expand the inside of b, and for that purpose, it is sufficient to induce the expansion at the inlet of the second nozzle 4b and then to make the fluid flow into the second nozzle 4b.

Therefore, in the ejector 4 of the present embodiment, the liquid refrigerant is decompressed and expanded by the first nozzle 4a provided upstream of the second nozzle 4b, so that the refrigerant state at the inlet of the second nozzle 4b becomes two-phase gas-liquid. It can be in a state. As a result, the nozzle efficiency is increased and the suction capacity of the ejector 4 is improved, so that the amount of the refrigerant circulating in the refrigerant evaporator 6 is increased and the cooling performance can be improved (see FIG. 5). Next, the concept for determining the optimum shape of the first nozzle 4a will be described. As shown in the above equation, the second
The outlet speed of the nozzle 4b is represented by the product of the nozzle efficiency ηn and the enthalpy difference Δi. Therefore, when the pressure reduction Δp by the first nozzle 4a is increased, the dryness x at R2 on the Mollier diagram shown in FIG. 3 increases and the nozzle efficiency ηn improves. However, the enthalpy difference Δi between R2 and R3 decreases. On the contrary, when the pressure reduction Δp by the first nozzle 4a is reduced, the dryness x at R2 decreases and the nozzle efficiency ηn decreases. However, the enthalpy difference Δi between R2 and R3 increases.

Actually, the relationship between the pressure reduction Δp by the throttle portion and the nozzle efficiency ηn was measured (condensation pressure of the refrigerant condenser: 12 atg, evaporation pressure of the refrigerant evaporator: 3 atg, subcool amount at the nozzle inlet: 10 ° C.). 6), as shown in FIG. 6, the nozzle efficiency ηn shows the optimum value when the pressure reduction Δp by the throttle portion is in the range of 5 to 7 kgf / cm ² . A solid line graph a in FIG. 6 is a measurement result when the throttle portion is a nozzle, and a solid line graph b is a measurement result when the throttle portion is an orifice. As described above, since the reduced pressure Δp by the first nozzle 4a has the optimum value, the shape of the first nozzle 4a is determined based on the optimum value.

In the above embodiment, the nozzle shape is used as the throttle portion, but the orifice 1 as shown in FIG. 7 is used.
2 or a capillary tube may be used. Also, the second
The throttle portion provided upstream of the nozzle 4b does not have to be limited to one location, and may be two or more locations. Although the decompression device of the present invention has been described as the ejector 4 used in the refrigeration cycle 1, the decompression device is not limited to the refrigeration cycle 1 and can be applied as a decompression device for geothermal power generation using steam.

[0017]

According to the decompression device of the present invention, the throttle portion provided on the upstream side of the nozzle can make the fluid having a low compressibility enter into the gas-liquid two-phase state at the inlet of the nozzle. As a result, the outlet speed of the fluid flowing out from the nozzle is increased, and the nozzle efficiency can be improved. This decompression device has a simple structure and does not increase in size only by providing a throttle portion upstream of the nozzle. Therefore, it can be used even in a place having a limited mounting space, such as a vehicle refrigeration cycle.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an ejector that is a pressure reducing device of the present invention.

FIG. 2 is a refrigeration cycle diagram.

FIG. 3 is a Mollier diagram of the refrigeration cycle.

FIG. 4 is a graph showing a relationship between a refrigerant state at a nozzle inlet and nozzle efficiency.

FIG. 5 is a graph showing cooling capacity.

FIG. 6 is a graph showing a relationship between decompression by a throttle unit and nozzle efficiency.

FIG. 7 is a cross-sectional view showing a modified example of a diaphragm unit.

[Explanation of symbols]

 4 Ejector (pressure reducing device) 4a 1st nozzle (throttle part) 4b 2nd nozzle (nozzle)

Claims (1)

[Claims] 1. A pressure reducing device having a nozzle for ejecting a fluid, wherein one or more throttle portions are provided upstream of the nozzle, and the fluid is reduced in pressure by passing through the throttle portion in a state of low compressibility. As a result, the pressure reducing device is characterized in that the inlet state of the nozzle is in a gas-liquid two-phase state.