Refrigeration air-conditioner using a non-azeotrope refrigerant and having a control-information detecting apparatus

Abstract: A control-information detecting apparatus for a refrigeration air-conditioner using a non-azeotrope refrigerant is equipped with a temperature detector (11) and a pressure detector (12) at the refrigerating cycle of the air-conditioner, which cycle is formed by connecting a compressor (1), a condenser (2), a decompressing device (3), and an evaporator (4), to detect the temperature (T 1 ) and the pressure (P 1 ) of the refrigerant circulating the cycle for obtaining the circulation composition of the refrigerant with the composition computing unit (2) thereof. The usual optimum operation of the cycle is thereby enabled even if the circulation composition of the refrigerant has changed.

Description: This invention relates to a refrigeration air-conditioner using a non-azeotrope refrigerant composed of a high boiling component and a low boiling component. In particular, the invention relates to a refrigeration air-conditioner comprising a control-information detecting apparatus for efficiently operating a refrigeration air-conditioner with high reliability even if the composition of a circulating refrigerant (hereinafter referred to as a circulating composition) has changed to another one different from initially filled one. Fig. 3 is a block diagram showing the construction of a conventional refrigeration air-conditioner using a non-azeotrope refrigerant illustrated in, for example, Japanese Unexamined Patent Application Published under No. 6546/86 (Kokai Sho-61/6546). In Fig. 3, reference numeral 1 designates a compressor; numeral 2 designates a condenser; numeral 3 designates a decompressing device using an expansion valve; numeral 4 designates an evaporator; and numeral 5 designates an accumulator. These elements are connected in series with a pipe between them, and compose a refrigeration air-conditioner as a whole. The refrigeration air-conditioner uses a non-azeotrope refrigerant composed of a high boiling component and a low boiling component as the refrigerant thereof. Next, the operation thereof will be described. In the refrigeration air-conditioner constructed as described above, a refrigerant gas having been compressed into a high temperature and high pressure state by the compressor 1 is condensed into liquid by the condenser 2. The liquefied refrigerant is decompressed by the decompressing device 3 to a low pressure refrigerant of two phases of vapor and liquid, and flows into the evaporator 4. The refrigerant is evaporated by the evaporator 4 to be stored in the accumulator 5. The gaseous refrigerant in the accumulator 5 returns to the compressor 1 to be compressed again and sent into the condenser 2. In this apparatus, the accumulator 5 prevents the return to the compressor 1 of a refrigerant in a liquid state by storing surplus refrigerants, which have been produced at the time when the operation condition or the load condition of the refrigeration air-conditioner is in a specified condition. It has been known that such a refrigeration air-conditioner using a non-azeotrope refrigerant suitable for its objects as the refrigerant thereof has merits capable of obtaining a lower evaporating temperature or a higher condensing temperature of the refrigerant, which could not be obtained by using a single refrigerant, and capable of improving the cycle efficiency thereof. Since the refrigerants such as "R12" or "R22" (both are the codes of ASHRAE: American Society of Heating, Refrigeration and Air Conditioning Engineers), which have conventionally been widely used, cause the destruction of the ozone layer of the earth, the non-azeotrope refrigerant is proposed as a substitute. Since the conventional refrigeration air-conditioner using a non-azeotrope refrigerant is constructed as described above, the circulation composition of the refrigerant circulating through the refrigerating cycle thereof is constant if the operation condition and the load condition of the refrigeration air-conditioner are constant, and thereby the refrigerating cycle thereof is efficient. But, if the operation condition or the load condition has changed, in particular, if the quantity of the refrigerant stored in the accumulator 5 has changed, the circulation composition of the refrigerant changes. Accordingly, the control of the refrigerating cycle in accordance with the changed circulation composition of the refrigerant, namely the adjustment of the quantity of the flow of the refrigerant by the control of the number of the revolutions of the compressor 1 or the control of the degree of opening of the expansion valve of the decompressing device 3, is required. Because the conventional refrigeration air-conditioner has no means for detecting the circulation composition of the refrigerant, it has a problem that it cannot keep the optimum operation thereof in accordance with the circulation composition of the refrigerant thereof. Furthermore, it has another problem that it cannot operate with high safety and reliability, because it cannot detect the abnormality of the circulation composition of the refrigerant thereof when the circulation composition has changed by the leakage of the refrigerant during the operation of the refrigerating cycle or an operational error at the time of filling up the refrigerant. It is an object of the present invention to provide a control-information detecting apparatus for a refrigeration air-conditioner using a non-azeotrope refrigerant, which apparatus can exactly detect the circulation composition of the refrigerant in the refrigerating cycle of the air conditioner by providing a liquid level detector for detecting a liquid level in the accumulator thereof even if the circulation composition has changed owing to the change of the operation condition or the load condition thereof, or even if the circulation composition has changed owing to the leakage of the refrigerant during the operation thereof or an operational error at the time of filling up the refrigerant. JP-A-6117737 discloses an apparatus for detecting refrigerant composition using a capacitance sensor in an evaporation portion of the refrigerant cycle. EP-A-0 685 692, which is comprised in the state of the art in accordance with Article 54(3) EPC for those parts based on Japanese priority document 116966/94, discloses a refrigerant circulation system having a composition computing unit for computing the composition of the refrigerant on a signal detected by a liquid level detector. According to the present invention, there is provided a refrigeration air-conditioner using a non-azeotrope refrigerant as defined in claim 1. As stated above, the control-information detecting apparatus according to the present invention detects the liquid level in the accumulator with the liquid level detector thereof to input the detected signal into the composition computing unit. If the unit computes the composition of the refrigerant by using the relationships between the liquid levels and the circulation compositions of the refrigerant, which relationships have been investigated previously, the air-conditioner can be controlled in the optimum condition thereof with the simply constructed control-information detecting apparatus even if the circulation composition of the refrigerant has changed. The above and further objects of the present invention will more fully appear from the following detailed description when the same is read in connection with the accompanying drawings. It is to be expressly understood, however, that the drawings are for purpose of illustration only and are not intended as a definition of the limits of the invention. Fig. 1 is a block diagram showing the construction of a refrigeration air-conditioner using a non-azeotrope refrigerant, which air-conditioner is equipped with a control-information detecting apparatus for it according to a first embodiment (embodiment 1) of the present invention; Fig. 2 is an explanatory diagram for the illustration of the operation of the composition computing unit of the embodiment 1 by using the relationship between the liquid levels of a refrigerant in an accumulator and the compositions of a refrigerant circulating through a refrigerating cycle; Fig. 3 is a block diagram showing the construction of a conventional refrigeration air-conditioner using a non-azeotrope refrigerant. EMBODIMENT 1 Fig. 1 is a block diagram showing the construction of a refrigeration air-conditioner using a non-azeotrope refrigerant, which air-conditioner is equipped with a control-information detecting apparatus for it according to a first embodiment of the present invention. The present embodiment is equipped with a liquid level detector 15 for detecting the liquid level of the refrigerant in the accumulator 5 therein, and the signals detected by the liquid level detector 15 are input into the composition computing unit 20. Well known level gauges such as an ultrasonic level gauge and a capacitance type level gauge may be employed as the liquid level detector 15. The unit 20 has the function of computing the circulation composition α of the non-azeotrope refrigerant on the liquid level h of the refrigerant in the accumulator 5, which is detected by the liquid level detector 15, and the operation of the unit 20 will be described hereinafter. The control-information detecting apparatus of the present embodiment comprises these liquid level detector 15 and composition computing unit 20. When the unit 20 begins to operate, the unit 20 takes therein the liquid level h. The refrigerant in the accumulator in a refrigerating cycle using a non-azeotrope refrigerant is generally separated into a liquid phase rich in high boiling components and a vapor phase rich in low boiling components, and the liquid phase rich in high boiling components is stored in the accumulator. The composition of the refrigerant circulating through the refrigerating cycle consequently has the inclination of having much low boiling components (or the circulation composition increases), if the liquid refrigerant exists in the accumulator. Fig. 2 shows a relationship between the liquid level h in the accumulator and the circulation composition α. The higher the liquid level in the accumulator becomes, or the larger the quantity of the liquid refrigerant in the accumulator becomes, the larger the circulation composition becomes. The circulation composition α can be computed from the liquid level h in the accumulator 5, which is detected by the liquid level detector 15, by previously obtaining the relationship shown in Fig. 2 by experiments or the like accordingly. When the control unit 21 begins to operate, the temperature T2 at the exit of the condenser 2 and the pressure P2 are detected by the temperature detector 13 and the pressure detector 14 respectively. Then, the control unit 21 takes therein the circulation composition α calculated by the composition computing unit 20 from the unit 20, and calculates the saturated liquid temperature T L at the condensation pressure P2 on the pressure P2 and the circulation composition α. This saturated liquid temperature T L is uniquely determined on the pressure P2, since the circulation composition α is fixed. The control unit 21 calculates the degree of supercooling SC of the refrigerant at the exit of the condenser 2 on the temperature T2 at the exit and the saturated liquid temperature T L (SC = T L - T2). Then, the unit 21 judges whether the degree of supercooling accords with a predetermined value, for example, 5°C or not. When the degree of supercooling accords with the predetermined value, the unit 21 moves to the end step. When the degree of supercooling is not judged to be in accord with the predetermined value, the unit 21 executes the alteration process of the degree of opening of the electric expansion valve of the decompressing device 3. The present embodiment can detect the circulation composition in the refrigerating cycle only on the liquid level of the refrigerant in the accumulator 5, which makes it possible to obtain a control-information detecting apparatus with a simple construction and to keep the degree of supercooling at the exit of the condenser 2 to an appropriate value despite the change of the circulation composition for enabling the usual optimum operation of the refrigeration air-conditioner. An ultrasonic or a capacitance type level gauge is used as the liquid level detector 15 of the aforementioned embodiment, but similar effects can be obtained by detecting the liquid level in the accumulator 5 by computing the surplus quantity of the refrigerant in the refrigerating cycle on the operation condition or the load condition thereof. Namely, the liquid level in the accumulator 5 may be detected by computing it from the relationship between the operation condition and the surplus quantity of the refrigerant, which relationship has been measured in advance by experiments or the like and is the fact, for example, that the surplus refrigerant is not produced in case of the operation of air cooling and a certain quantity of the surplus refrigerant is produced in case of the operation of air heating. Furthermore, the accuracy of detecting the liquid level in the accumulator may be improved by adding the information such as the temperature of the air inside a room and the temperature of the air outside the room at the time of the operation of air cooling or air heating. The control-information detecting apparatus for a refrigeration air-conditioner using a non-azeotrope refrigerant is constructed so that the comparison operation means of the apparatus generates a warning signal when the composition of the refrigerant detected by the composition computing unit thereof is out of a predetermined range, and that the warning means thereof operates on the warning signal generated by the comparison operation means, and consequently, when the composition of the refrigerant is out of the prescribed range, the fact can immediately be known. While preferred embodiments of the present invention have been described using specific terms, such description is for illustrative purposes only, and it is to be understood that changes and variations may be made without departing from the scope of the following claims.

Claims: A refrigeration air-conditioner using a non-azeotrope refrigerant as a refrigerant thereof; the air-conditioner having a refrigerating cycle composed by connecting a compressor (1), a condenser (2), a decompressing device (3), an evaporator (4), an accumulator (5); said air-conditioner further comprising a control-information detecting apparatus comprising: a liquid level detector (15) for detecting the liquid level in said accumulator; a composition computing unit (20) for computing the composition of the refrigerant circulating through said refrigerating cycle based on a signal detected by said liquid level detector; a comparison operation means for generating a warning signal when the composition of the refrigerant computed by said composition computing unit is out of a predetermined range, and a warning means operating on a warning signal generated by said comparison operation means.

Inventors: KASAI TOMOHIKO, MORIMOTO OSAMU, OKAZAKI TAKASHI, SUMIDA YOSHIHIRO, KASAI, TOMOHIKO, MORIMOTO, OSAMU, OKAZAKI, TAKASHI, SUMIDA, YOSHIHIRO, Kasai, Tomohiko, Mitsubishi D. K.K. of W. S., Morimoto, Osamu, Mitsubishi D. K.K. of W. S., Okazaki, Takashi, c/o Mitsubishi D. K.K. C. K., Sumida, Yoshihiro, c/o Mitsubishi D. K.K. C. K.
Applicants: MITSUBISHI ELECTRIC CORP, MITSUBISHI DENKI KABUSHIKI KAISHA
Application year: 1995
Main classification: F25B49
IPC codes: F25B9