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. 4 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. 4, 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. In view of the foregoing, 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, composed in a simple construction, can exactly detect the circulation composition of the refrigerant in the refrigerating cycle of the air-conditioner by computing the signals from three temperature detectors or more and a pressure detector of the apparatus with a composition computing unit thereof even if the circulation composition has changed owing to the change of the operation condition or the load condition of the air-conditioner, 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. EP-A-0586 193 discloses a refrigeration cycle in which the composition of a refrigerant is detected for control purposes. 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 based upon signals received from temperature and pressure sensors. According to the present invention, there is provided a refrigeration air-conditioner using a non-azeotrope refrigerant as defined in claim 1. Optional features may be provided as defined in the other claims. As stated above, the control-information detecting apparatus computes the composition of the refrigerant circulating through the refrigerating cycle on the signals having been detected by the three temperature detectors or more and the pressure detector respectively for exactly detecting the circulation composition even if the circulation composition has changed owing to the change of the operation condition or the load condition of the air-conditioner, 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. 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 control-information detecting apparatus for a refrigeration air-conditioner using a non-azeotrope refrigerant 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 temperatures of a non-azeotrope refrigerant at the distances from the entrance of a double-pipe type heat exchanger; Fig. 3 is an explanatory diagram for the illustration of the operation of the composition computing unit of the embodiment 1 by using the temperatures of the compositions of a circulating non-azeotrope refrigerant; and Fig. 4 is a block diagram showing the construction of a conventional refrigeration air-conditioner using a non-azeotrope refrigerant. Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings. EMBODIMENT 1 Fig. 1 is a block diagram showing the construction of a control-information detecting apparatus for a refrigeration air-conditioner using a non-azeotrope refrigerant according to a first embodiment of the present invention. The embodiment is equipped with five temperature detectors 65a, 65b, 65c, 65d, and 65e near the exit of the pipe on the high pressure side of the double-pipe type heat exchanger 63. And a pressure detector 66 for measuring the high pressure of the bypass pipe 61 is equipped at the entrance of the bypass pipe 61. The composition computing unit 20 has the function of computing the circulation composition of the non-azeotrope refrigerant in the refrigerating cycle on the temperatures and the pressure detected by the five temperature detectors 65 and the pressure detector 66 respectively. The embodiment uses a capillary tube as the second pressure detector 62. Next, the operation of the composition computing unit 20 will be described. The high pressure vapor refrigerant flown into the double-pipe type heat exchanger 63 exchanges the heat thereof with the low temperature and low pressure refrigerant to be condensed into liquid. A change of the temperature of the high pressure refrigerant is shown in Fig. 2. There exist a superheated vapor area at the entrance on the high pressure side. of the heat exchanger 63, two-phase area at the intermediate part thereof, and the supercooled liquid area at the exit thereof. The values detected by the five temperature detectors 65 equipped on the pipe on the high pressure side of the heat exchanger 63 are shown in Fig. 2 as Ta, Tb, Tc, Td, and Te. Because the refrigerant in the two-phase area varies with latent heat, the variation of the temperature thereof is small, and then the variations of the detected temperatures Ta, Tb, and Tc are also small. On the other hand, because the refrigerant in the supercooled liquid area varies with sensible heat, the variation of the temperature thereof is large, and then the variations of the detected temperatures Td and Te are also large. Accordingly, by comparing the differences between the temperatures detected adjoining temperature detectors among the five detectors along the direction of the flow of the refrigerant in order, the temperature at the point where the differences varies in a large scale can be regarded as the saturated liquid temperature thereof. For example, as to the example shown in Fig. 2, by comparing the temperature differences (Ta - Tb), (Tb - Tc), (Tc - Td), (Td - Te) in the order of the direction of the flow, the temperature difference (Tc - Td) is proved to be larger than the temperature differences (Ta - Tb) and (Tb - Tc). As a result, the temperature Tc can be regarded as the saturated liquid temperature. The composition computing unit 20 computes the circulation composition α from the relationship among the saturated liquid temperatures, pressures, and the circulation compositions shown in Fig. 3 on the saturated liquid temperature Tc and the high pressure P detected by the pressure detector 66. The control-information detecting apparatus for a refrigeration air-conditioner using a non-azeotrope refrigerant is constructed so as to compute the composition of the refrigerant circulating through the refrigerating cycle of the air-conditioner on the signals having been detected by the three temperature detectors or more and the pressure detector of the apparatus for detecting the temperatures and the pressure of the refrigerant on the high pressure side of the bypass pipe of the air-conditioner respectively, and consequently, the apparatus can exactly detect the circulation composition in the refrigerating cycle even if the circulation composition has changed owing to the change of the operation condition or the load condition of the air-conditioner, 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. 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 first decompressing device (3), and an evaporator (4); the air-conditioner further having a bypass pipe (61) for connecting a high pressure side extending from an exit of said compressor to said first decompressing device to a low pressure side extending from said first decompressing device to an entrance of said compressor with a second decompressing device (62) between them, and a cooling means (63) for cooling a non-azeotrope refrigerant flowing from a high pressure side of said bypass pipe to said second decompressing device; said air conditioner further comprising a control-information detecting apparatus comprising: three temperature detectors (65a-65e) or more for detecting the temperature of the refrigerant on the high pressure side of said bypass pipe, a pressure detector (66) for detecting the pressure of the refrigerant on the high pressure side of the bypass pipe, and a composition computing unit (20) for computing a composition of the refrigerant circulating through said refrigerating cycle based on signals respectively detected by said temperature detectors and said pressure detector. The refrigeration air-conditioner using a non-azeotrope refrigerant according to Claim 1, wherein said cooling means is constructed so as to exchange heat between the high pressure side and a low pressure side of said bypass pipe. The refrigeration air-conditioner using a non-azeotrope refrigerant according to Claim 1, wherein said control-information detecting apparatus further comprises: 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, c/o Mitsubishi D. K.K. of W. S., Morimoto, Osamu, c/o 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