JPH07260264A - Refrigerating device - Google Patents

Abstract

PURPOSE:To make it possible to easily and accurately determe the mixing ratio of the refrigerants during operation of a refrigerating device. CONSTITUTION:The subject relates to a refrigerating device having a refrigerant circuit in which a compressor 1, condenser 2, expansion mechanism 3, and evaporator 4 are connected and through which a nonazeotropic mixture of refrigerants is circulated. In this refrigerating system there are provided a pressure detector 5 which detects the discharge pressure of the compressure 1 and a plurality of temperature detectors 7, 8 which detect the temperatures of the refrigerant inside the condenser 2 at a plurality of spots positioned therein with specified distances apart from the condenser exit 2a. From the ratio of the differential temperature of the refrigerant detected by these temperature detectors 7, 8 to the difference between the distances from the condenser exit 2a to the respective temperature detectors 7, 8 the gradient of a change in temperature of the refrigerant inside the condenser 2 is obtained. Furthermore, there are provided a first calculating means and a second calculating means: the first calculating mans is for obtaining the condensing saturation temperature of the refrigerant at the condenser exit 2a on the basis of the above-mentioned gradient and the second calculating means is for obtaining the mixing ratio of the refrigerants on the basis of the condensing saturation temperature determined by the first calculating means and the discharge pressure detected by the pressure detector 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refrigerating apparatus using a non-azeotropic mixed refrigerant as a working medium.
The present invention relates to a refrigerating device which makes it possible to easily obtain a mixing ratio of refrigerant circulating in a refrigerant circuit.

[0002]

2. Description of the Related Art A refrigeration system using a non-azeotropic mixed refrigerant in which two or more kinds of refrigerants having different boiling points are mixed as a working medium has been well known.

This non-azeotropic mixed refrigerant differs in the boiling point of the mixed refrigerants from each other. Therefore, unlike the case where a single refrigerant is used, a phase change (for example, liquid phase → gas phase or The refrigerant temperature in the evaporator or condenser that produces the gas phase → liquid phase is not constant and changes linearly with a predetermined odor.

By the way, as one means for improving the efficiency of the refrigeration cycle, there is a method of controlling the opening degree of the expansion mechanism so that the degree of superheat of the refrigerant on the outlet side of the evaporator becomes constant. In order to perform the above, it is necessary to know the saturation temperature of the refrigerant on the outlet side of the evaporator. This saturation temperature can be easily obtained by simply detecting the refrigerant pressure in the case of a refrigeration system using a single refrigerant, but in the case of a refrigeration system using a non-azeotropic mixed refrigerant, the saturation temperature must be determined if it is unknown. I can't. That is, in the case of a single refrigerant, the saturation temperature can be obtained only by the pressure information from the compressor suction part,
In the case of a non-azeotropic mixed refrigerant, information on pressure, dryness, and mixing ratio is required to obtain the saturation temperature.

For the above reasons, in order to control the degree of superheat in a refrigeration system using a non-azeotropic mixed refrigerant, it is necessary to obtain the refrigerant mixture ratio in the refrigeration cycle.

From such a demand, a temperature detector is provided at a position that is likely to be close to the saturation temperature of the evaporator, and the temperature detected by the temperature detector is assumed to be the refrigerant saturation temperature to obtain the refrigerant mixture ratio. What was done (Japanese Patent Publication No. 5-45868)
(See Japanese Laid-Open Patent Publication No. 61-138), or the temperature and pressure of the refrigerant when the refrigeration system is stopped, and the mixture ratio of the refrigerant is calculated based on these.
No. 058) has already been proposed.

[0007]

However, in the former case of the above-mentioned known example, it is difficult to set the point where the refrigerant is completely saturated, so that it is difficult to accurately detect the saturation temperature.
The resulting mixing ratio may also be inaccurate. Further, in the latter case of the above-mentioned known example, there is a problem that the refrigerant mixture ratio during operation cannot be obtained because it is based on the temperature and the pressure when the operation is stopped. Note that the refrigerant mixing ratio often differs between when the operation is stopped and when the operation is in progress due to the influence of the load of the refrigeration cycle and the like.

The present invention has been made in view of the above points, and it is an object of the present invention to easily and accurately determine the mixing ratio of the refrigerant during the operation of the refrigeration system.

[0009]

DISCLOSURE OF THE INVENTION The present invention relates to a refrigerating apparatus in which a non-azeotropic mixed refrigerant is circulated in a refrigerant circuit connecting a compressor, a condenser, an expansion mechanism and an evaporator. And a plurality of temperature detectors for detecting the refrigerant temperature at a plurality of locations (two or more locations) apart from the condenser outlet in the condenser by a predetermined temperature detector. Obtain the odor of the refrigerant temperature change in the condenser by the ratio of the difference in the detected refrigerant temperature and the difference in the distance from the condenser outlet to the temperature detector, and based on the odor, the refrigerant at the condenser outlet A first calculation means for obtaining a condensation saturation temperature, and a second calculation means for obtaining a refrigerant mixture ratio based on the condensation saturation temperature obtained by the first calculation means and the discharge pressure detected by the pressure detector.
The basic configuration is a configuration including a computing means.

[0010]

In the present invention, a plurality of locations (two or more locations) in the condenser, which are separated from the condenser outlet by a predetermined distance.
The ratio of the difference in the refrigerant temperatures detected by the temperature detectors that detect the refrigerant temperature to the difference in the distance from the condenser outlet to the temperature detector determines the scent of the refrigerant temperature change in the condenser. , The condensation saturation temperature of the refrigerant at the outlet of the condenser is obtained based on the odor distribution. In other words, when the temperature distribution of the refrigerant temperature change is constant in the predetermined region on the outlet side of the condenser, the condensation saturation temperature of the refrigerant at the condenser outlet is naturally obtained if the temperature distribution of the refrigerant temperature change is obtained.

Since there is a slight supercooling zone on the outlet side of the condenser, if the refrigerant temperature detection points are two, the length of the supercooling zone must be ignored. Generally, the refrigerant temperature on the outlet side of the condenser is only supercooled by a few degrees, so if the distance from the temperature detector near the supercooling area to the condenser outlet is sufficiently long, the condensation saturation temperature will be accurate. Well obtained. When the number of refrigerant temperature detection points is three or more, the length of the supercooling zone can be deleted in the process of calculation, so that an accurate condensation saturation temperature can be obtained without being affected by the supercooling zone.

Thereafter, when the condensation saturation temperature at the condenser outlet is obtained as described above, the mixture ratio of the refrigerant is obtained based on the condensation saturation temperature and the pressure at that time (that is, the discharge pressure of the compressor). To be This refrigerant mixture ratio is obtained from, for example, an isobaric vapor-liquid equilibrium diagram of a non-azeotropic mixed refrigerant. In addition,
Since the pressure loss in the condenser is small, there is no problem even if the discharge pressure of the compressor is used as the pressure at the outlet of the condenser.

[0013]

EFFECTS OF THE INVENTION According to the present invention, in a refrigerating apparatus using a non-azeotropic mixed refrigerant, a plurality of locations (two or more locations) apart from a condenser outlet by a predetermined distance in a condenser.
Of the temperature difference of the refrigerant temperature detected by a plurality of temperature detectors to detect the refrigerant temperature and the ratio of the difference in the distance from the condenser outlet to the temperature detector to obtain the scent of the refrigerant temperature change in the condenser, Since the condensation saturation temperature of the refrigerant at the outlet of the condenser is obtained based on the scent, and the mixing ratio of the refrigerant is obtained based on the condensation saturation temperature thus obtained and the discharge pressure detected by the pressure detector. It is said that an accurate refrigerant mixture ratio during operation of the refrigeration system can be obtained from the fact that the condensation saturation temperature at the condenser outlet can be accurately obtained by simply obtaining the refrigerant temperature change pattern that is constant in the predetermined region on the outlet side of the refrigerator. It has an excellent effect.

If there are two refrigerant temperature detection points, there is a slight supercooling zone on the outlet side of the condenser, so the length of the subcooling zone must be ignored. But
Generally, the refrigerant temperature on the outlet side of the condenser is only supercooled by a few degrees, so if the distance from the temperature detector near the supercooling area to the condenser outlet is sufficiently long, the condensation saturation temperature will be accurate. Good results are obtained, and the accuracy of detecting the refrigerant mixture ratio does not decrease.

When the number of refrigerant temperature detection points is three or more, the length of the supercooling region can be deleted in the process of calculation, so that an accurate condensation saturation temperature can be obtained without being affected by the subcooling region. The accuracy of detecting the refrigerant mixture ratio is further improved.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Some preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

Embodiment 1 FIGS. 1 and 2 show a refrigerating apparatus using a non-azeotropic mixed refrigerant according to Embodiment 1 of the present invention.

As shown in FIG. 1, the refrigerating apparatus of this embodiment comprises a refrigerant circuit A in which a compressor 1, a condenser 2, an electric expansion valve 3 acting as an expansion mechanism, and an evaporator 4 are connected. The non-azeotropic mixed refrigerant is circulated in the refrigerant circuit A to condense and liquefy the non-azeotropic mixed refrigerant that exchanges heat with the fluid to be heated in the condenser 2 and the non-azeotropic mixture that exchanges heat with the fluid to be cooled in the evaporator 4. It is supposed to evaporate the refrigerant.

On the discharge side of the compressor 1, the discharge pressure P ₁
Is provided with a discharge pressure detector 5 for detecting the
A suction pressure detector 6 for detecting the suction pressure P ₂ is provided on the suction side of. Further, in the condenser 2, two temperature detectors 7 and 8 for detecting the refrigerant temperatures T ₁ and T ₂ at the respective locations are provided at two locations apart from the outlet 2a of the condenser 2 by a predetermined distance, A temperature detector 9 for controlling the degree of superheat is provided on the outlet side of the evaporator 4.

As shown in FIG. 4, the temperature detectors 7 and 8 are provided at two positions apart from the outlet 2a of the condenser 2 by a predetermined distance a and b and within the gas-liquid two-phase region. The distance a between the temperature detector 7 located on the outlet side of 2 and the condenser outlet 2a
Since there exists a slight supercooling region (region of a distance c from the outlet 2a of the condenser 2) on the outlet side of the condenser 2, it is desirable to set so that a >> c. In addition, the distance c of the supercooling area
Is extremely smaller than the total length L of the condenser 2.

Further, the refrigerant circuit A is additionally provided with a controller 10 for performing various calculations for detecting a refrigerant mixture ratio, which will be described later, and calculations for superheat degree control and a control signal output.

The controller 10 comprises, for example, a microcomputer, and as shown in FIG. 2, the temperature difference between the refrigerant temperatures T ₁ and T ₂ detected by the temperature detectors 7 and 8.
(T ₂ -T ₁₎ and the condenser distance a from the outlet 2a to the temperature detector 7 and 8, the ratio of the difference of b (b-a) (T 2 -T 1) / (b-a) by condensation The temperature distribution of the refrigerant in the condenser 2 is calculated, and the condensation saturation temperature Tc of the refrigerant at the condenser outlet 2a is calculated based on the temperature distribution.
And a second calculating means 11 for calculating the refrigerant mixture ratio C based on the condensation saturation temperature Tc calculated by the first calculating means 11 and the discharge pressure P ₁ detected by the discharge pressure detector 5. Computing means 12 and the second computing means 1
Superheat degree control means 1 for outputting a control signal to the electric expansion valve 3 so as to control the superheat degree at the outlet of the evaporator 4 to be constant based on the refrigerant mixture ratio C obtained by 2.
3 and 3.

Next, the operation of the controller 10 in the refrigerating apparatus of this embodiment will be described with reference to the flow chart shown in FIG.

In step S ₁ , the pressures P ₁ and P ₂ detected by the pressure detectors 5 and 6 and the refrigerant temperatures T ₁ and T ₂ detected by the temperature detectors 7 and 8 are input, and in step S ₂ . The first calculator 11 calculates the condensation saturation temperature Tc of the refrigerant at the condenser outlet 2a.

The condensation saturation temperature Tc is calculated as follows.

First, since the temperature variation of the refrigerant in the condenser 2 is constant as shown in FIG. 5, the temperature variation of the refrigerant between the temperature detectors 7 and 8 and the temperature detector 7 are The temperature change odor of the refrigerant is equal to that of the upstream end of the supercooling region, and the following equation is established.

(T ₂ −T ₁ ) / (b−a) = (T ₁ −Tc) / (a−c) where the unknown value is the distance c between the condensation saturation temperature Tc and the supercooling region.
However, since the refrigerant temperature on the outlet side of the condenser 2 is generally only supercooled by a few degrees, the distance a from the temperature detector 7 to the condenser outlet 2a is sufficiently long. , The distance c in the supercooling zone can be ignored. Therefore, the condensation saturation temperature Tc at the condenser outlet 2a can be obtained from the above equation.

Then, in step S ₃ , the condensation saturation temperature Tc and the discharge pressure detector 5 obtained as described above are measured.
Discharge pressure P ₁ and dryness detected by (in this case,
Since the condensation end position, dryness = 0) controller 10
The second computing means 12 obtains the mixing ratio C of the non-azeotropic mixed refrigerant by collating with the mixing ratio calculation map (see FIG. 6) provided therein. That is, if the boiling point at the condensation saturation temperature Tc is obtained in the mixture ratio calculation map (constant pressure = discharge pressure P ₁ , dryness = 0) in FIG. 6, the mixture ratio C at that time can be obtained. Since the pressure loss in the condenser 2 is small, the pressure at the condenser outlet 2a is almost equal to the discharge pressure P ₁ .

Next, in step S ₄ , the superheat control means 13 executes the superheat control. For the superheat control, the evaporation saturation temperature Te at the outlet of the evaporator 4 is required. . This evaporation saturation temperature Te is the suction pressure P ₂ detected by the suction pressure detector 6, the dryness (in this case, the dryness is 1.0 because it is the evaporation end position), and the refrigerant mixture ratio C obtained in step S ₃ . Is compared with the evaporation saturation temperature calculation map (see FIG. 7). That is,
If the dew point at the mixing ratio C is found in the evaporation saturation temperature calculation map of FIG. 7 (constant pressure = suction pressure P ₂ , dryness = 1.0), the evaporation saturation temperature Te at that time can be found. The opening control signal is sent to the electric expansion valve 3 so that the temperature difference between the evaporation saturation temperature Te calculated in this way and the refrigerant temperature detected by the superheat degree control temperature detector 9 becomes constant. Is output.

As described above, according to the present embodiment, the refrigerant detected by the temperature detectors 7 and 8 provided in the condenser 2 at two positions separated from the condenser outlet 2a by the predetermined distances a and b. The temperature change gradient is obtained from the temperature, the condensation saturation temperature Tc of the refrigerant at the condenser outlet 2a is obtained from the temperature change gradient, and the mixture ratio C of the refrigerant is obtained from the thus obtained condensation saturation temperature Tc. The refrigerant mixture ratio C during the operation of the device can be easily and accurately obtained. In addition, in the case of the present embodiment, since there is a slight supercooling region on the outlet side of the condenser 2, the length c of the subcooling region needs to be ignored. Since the temperature of the refrigerant on the outlet side is only supercooled by a few degrees, the temperature detector 7 close to the supercooled region is connected to the condenser outlet 2
If the distance a to a is sufficiently long, the condensation saturation temperature can be obtained with high accuracy, and the accuracy of detecting the refrigerant mixture ratio will not be reduced.

Embodiment 2 FIGS. 8 and 9 show a refrigerating apparatus according to Embodiment 2 of the present invention.

In the case of this embodiment, temperature detectors 7, 8 and 14 are provided at three locations inside the condenser 2 which are separated from the condenser outlet 2a by a predetermined distance a, b and d (see FIG. 10). . Therefore, the temperature information (that is, the refrigerant temperatures T ₁ , T ₂ , T ₃ ) from the temperature detectors 7, 8, 14 is input to the first computing means 11. The other configuration is similar to that of the first embodiment, and thus the description is omitted.

In the case of the present embodiment, when the condensation saturation temperature Tc at the condenser outlet 2a is obtained in step S ₂ in the flowchart of FIG. 3, the first computing means 11 carries out the following computation.

That is, the temperature variation of the refrigerant between the temperature detectors 7 and 8, the temperature variation of the refrigerant between the temperature detectors 8 and 14, the temperature detectors 7 and 8 and the upstream end of the supercooling region. And the temperature variation pattern of the refrigerant are equal to each other, and the following two expressions are established (see FIGS. 10 and 11).

(T ₂ −T ₁ ) / (b−a) = (T ₁ −Tc) / (a−c) (T ₃ −T ₂ ) / (d−b) = (T ₂ −Tc) / (b−c) Here, the unknown value is the distance c between the refrigerant saturation temperature Tc and the supercooling region.
However, the length c of the supercooling zone is eliminated by the above equation 2 and the condensation saturation temperature Tc at the condenser outlet 2a is obtained.

Therefore, in the case of the present embodiment, since it is not necessary to make the length c of the subcooling zone approximately 0 as in the first embodiment, the condensation saturation temperature Tc can be calculated with higher accuracy. .

The other functions and effects are the same as those of the first embodiment, and the description thereof will be omitted.

In the condenser 2, the condenser outlet 2a
When the temperature detectors are provided at four or more positions separated by a predetermined distance from, the measurement accuracy can be further improved by calculating the average value of the condensation saturation temperature obtained by the same method as above. .

In the above embodiment, the refrigerating device dedicated to cooling is explained, but the present invention is also applicable to a heat pump type refrigerating device.

[Brief description of drawings]

FIG. 1 is a refrigerant circuit diagram of a refrigeration system according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing the contents of a controller in the refrigerating apparatus according to the first embodiment of the present invention.

FIG. 3 is a flowchart illustrating the operation of the controller in the refrigerating apparatus according to the first embodiment of the present invention.

FIG. 4 is a Mollier diagram showing the state of the refrigerant in the refrigerating apparatus according to the first embodiment of the present invention.

FIG. 5 is a characteristic diagram showing a refrigerant temperature change in the condenser in the refrigerating apparatus according to the first embodiment of the present invention.

FIG. 6 is a mixture ratio calculation map of the non-azeotropic mixed refrigerant used in the refrigeration apparatus according to the first embodiment of the present invention.

FIG. 7 is an evaporation saturation temperature calculation map of a non-azeotropic mixed refrigerant used in the refrigerating apparatus according to the first embodiment of the present invention.

FIG. 8 is a refrigerant circuit diagram of the refrigerating apparatus according to the second embodiment of the present invention.

FIG. 9 is a block diagram showing the contents of a controller in the refrigerating apparatus according to the second embodiment of the present invention.

FIG. 10 is a Mollier diagram showing the state of the refrigerant in the refrigerating apparatus according to the second embodiment of the present invention.

FIG. 11 is a characteristic diagram showing a change in refrigerant temperature in the condenser in the refrigerating apparatus according to the second embodiment of the present invention.

[Explanation of symbols]

1 is a compressor, 2 is a condenser, 2a is a condenser outlet, 3 is an expansion mechanism (electrical expansion valve), 4 is an evaporator, 5 is a discharge pressure detector, 7 and 8 are temperature detectors, and 10 is a controller. , 11 is a first calculation means, 12 is a second calculation means, 13 is a superheat control means, and 14 is a temperature detector.

Claims (3)

[Claims] 1. A refrigeration system for circulating a non-azeotropic mixed refrigerant in a refrigerant circuit connecting a compressor, a condenser, an expansion mechanism and an evaporator, the pressure detector detecting a discharge pressure of the compressor. And a plurality of temperature detectors for detecting the refrigerant temperature at a plurality of locations separated by a predetermined distance from the condenser outlet in the condenser, and the temperature difference from the condenser outlet and the temperature difference between the refrigerant temperatures detected by these temperature detectors. The ratio of the difference in the distance to the detector and the ratio of the refrigerant temperature change in the condenser are calculated,
First computing means for obtaining the condensation saturation temperature of the refrigerant at the outlet of the condenser based on the odor, and refrigerant based on the condensation saturation temperature obtained by the first computation means and the discharge pressure detected by the pressure detector. And a second calculation means for obtaining the mixing ratio of the refrigeration system. 2. The refrigerating apparatus according to claim 1, wherein the temperature detectors are provided at two locations. 3. The refrigerating apparatus according to claim 1, wherein the temperature detectors are provided at three or more places.