Air-conditioner using a non-azeotrope refrigerant and having a composition computing unit

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 and including a control-information detecting apparatus. In particular, the invention relates to 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. 21 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. 21, 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. EP-A-0586193 describes a control information detecting apparatus having an electrostatic capacitance sensor for monitoring refrigerant composition, and means for controlling the operation of the refrigeration cycle in response to the detected composition. EP-A-0 685 692 (comprised in the state of the art in accordance with Art. 54(3) EPC) discloses a composition computing unit for computing the composition of a non-azeotrope refrigerant based upon signals received from temperature and pressure sensors. 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 a temperature detector 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. According to the present invention, there is provided 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, a condenser, a first decompressing device, and an evaporator to one another, in series; the air-conditioner further having a bypass pipe connected between a high pressure region of the cycle, between an exit of said compressor and said condenser, and a low pressure region of the cycle, between said evaporator and an entrance of said compressor, a second decompressing device being located within said bypass pipe, and a cooling means for cooling the non-azeotrope refrigerant flowing from a high pressure side of said bypass pipe into said second decompressing device; and a control-information detecting apparatus comprising: a first temperature detector for detecting a temperature of the refrigerant on a low pressure side at an exit of said second decompressing device, a pressure detector for detecting a pressure of the refrigerant on the low pressure side at the exit of the second decompressing device, and a composition computing unit for computing a composition of the refrigerant circulating through said refrigerating cycle on signals respectively detected by said first temperature detector and said pressure detector. As stated above, the air-conditioner according to the present invention computes the composition of the refrigerant circulating through the refrigerating cycle of the air- conditioner on the signals having been detected by the first temperature detector and the pressure detector with the composition computing unit 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 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. The above 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 lines showing the relationships between pressures and enthalpy; Fig. 3 is an explanatory diagram for the illustration of the operation of the composition computing unit of the embodiment 1 by using the relationships between the temperatures of a non-azeotrope refrigerant and circulation compositions; Fig. 4 is an explanatory diagram for the illustration of the operation of the composition computing unit of the embodiment 1 by using the relationships among the compositions, the saturated liquid temperatures, and the pressures of a circulating non-azeotrope refrigerant; Fig. 5 is an explanatory diagram for the illustration of the operation of the composition computing unit of the embodiment 1 by using the relationships between the temperatures of a refrigerant and the dryness thereof; Fig. 6 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 second embodiment (embodiment 2) of the present invention; Fig. 7 is an explanatory diagram for the illustration of the operation of the composition computing unit of the embodiment 2 by using lines showing the relationships between pressures and enthalpy; Fig. 8 is a flowchart showing the operation of the composition computing unit of the embodiment 2; Fig. 9 is an explanatory diagram for the illustration of the operation of the composition computing unit of the embodiment 2 by using the relationships among the dryness, the temperatures, and the pressures of a circulating non-azeotrope refrigerant; Fig. 10 is an explanatory diagram for the illustration of the operation of the composition computing unit of the embodiment 2 by using the temperatures at the dryness X of a non-azeotrope refrigerant in two phases of vapor and liquid; Fig. 11 is an explanatory diagram for the illustration of the operation of the composition computing unit of the embodiment 2 by using the temperatures at the dryness X of a non-azeotrope refrigerant in two phases of vapor and liquid and the circulation composition of the refrigerant; Fig. 12 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 third embodiment (embodiment 3) of the present invention; Fig. 13 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 fourth embodiment (embodiment 4) of the present invention; Fig. 14 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 fifth embodiment (embodiment 5) of the present invention; Fig. 15 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 sixth embodiment (embodiment 6) of the present invention; Fig. 16 is a control block diagram of a refrigeration air-conditioner using a non-azeotrope refrigerant, which air-conditioner is equipped with a control-information detecting apparatus according to the embodiment 6; Fig. 17 is an explanatory diagram for the illustration of the operation of the composition computing unit of a control-information detecting apparatus for a refrigeration air-conditioner using a non-azeotrope refrigerant according to the embodiment 6 by using the relationship between the condensation pressures of a non-azeotrope refrigerant and circulation compositions; Fig. 18 is an explanatory diagram for the illustration of the operation of the composition computing unit of a control-information detecting apparatus for a refrigeration air-conditioner using a non-azeotrope refrigerant according to the embodiment 6 by using the relationship between the evaporation pressures of a non-azeotrope refrigerant and circulation compositions; Fig. 19 is an explanatory diagram for the illustration of the operation of the composition computing unit of a control-information detecting apparatus for a refrigeration air-conditioner using a non-azeotrope refrigerant according to the embodiment 6 by using the relationships among the saturated liquid temperatures and the pressures of a non-azeotrope refrigerant and circulation compositions; Fig. 20 is an explanatory diagram for the illustration of the operation of the composition computing unit of a control-information detecting apparatus for a refrigeration air-conditioner using a non-azeotrope refrigerant according to the embodiment 6 by using the relationships among the saturated vapor temperatures and the pressures of a non-azeotrope refrigerant and circulation compositions; and Fig. 21 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. In Fig. 1 reference numeral 1 designates a compressor; numeral 2 designates a condenser; numeral 3 designates a decompressing device using, for example, a capillary tube; 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 refrigerating cycle. For example, a non-azeotrope refrigerant composed of a high boiling component "R134a" and a low boiling component "R32" is filled in the refrigerating cycle. Reference numeral 61 designates a bypass pipe for connecting the discharge pipe with the suction pipe of the compressor 1; a second decompressing device 62 composed of a capillary tube or the like is equipped at an intermediate position of the bypass pipe 61. Reference numeral 63 designates a double-pipe type heat exchanger as a cooling means for cooling the non-azeotrope refrigerant flowing into the second decompressing device 62 from the high pressure side of the bypass pipe 61; the heat exchanger 63 exchanges the heat thereof with the low pressure side of the bypass pipe 61. At the exit of the second decompressing device 62 are equipped a first temperature detector 11 for detecting the temperature of the refrigerant and a first pressure detector 12 for detecting the pressure of the refrigerant. Reference numeral 20 designates a composition computing unit, into which the signals detected by the first temperature detector 11 and the first pressure detector 12 are input. The composition computing unit 20 has the function of computing the circulation composition of the non-azeotrope refrigerant in the refrigerating cycle of the refrigeration air-conditioner on the temperatures and the pressures at the exit of the second decompressing device 62, which temperatures and pressures are respectively detected by the first temperature detector 11 and the first pressure detector 12. These first temperature detector 11, first pressure detector 12, and composition computing unit 20 comprise a control-information detecting apparatus of the embodiment. Next, the operation thereof will be described. The refrigerant gas in high temperature and high pressure having been compressed by the compressor 1 is condensed by the condenser 2 into liquid, and the liquefied refrigerant is decompressed by the decompressing device 3 into the refrigerant of two phases of vapor and liquid having a low pressure, which flows into the evaporator 4. The refrigerant is evaporated by the evaporator 4 and returns to the compressor 1 through the accumulator 5. Then, the refrigerant is again compressed by the compressor 1 to be sent into the condenser 2. The surplus refrigerants, which are produced at the time when the operation condition or the load condition of the air-conditioner is a specified condition, are stored in the accumulator 5. The refrigerants in the accumulator 5 are separated into liquid phase refrigerants rich in high boiling components and vapor phase refrigerants rich in low boiling components; the liquid phase refrigerants are stored in the accumulator 5. When the liquid refrigerants exist in the accumulator 5, the composition of the refrigerant circulating through the refrigerating cycle shows a tendency of becoming rich in the low boiling components (or the circulating components increase). A part of the high pressure vapor refrigerants discharged by the compressor 1 flows into the bypass pipe 61 to exchange the heat thereof with low pressure refrigerants at the annular part of the double-pipe type heat exchanger 63 to be condensed into liquid. The liquefied refrigerant is decompressed by the second decompressing device 62 to flow into the inner tube of the double-pipe type heat exchanger 63 in the state of a low pressure refrigerant for exchanging the heat thereof with the high pressure refrigerant in the annular part and being evaporated. The low pressure vapor refrigerant flows into the suction pipe of the compressor 1. Fig. 2 shows the changes of states of the refrigerant in the bypass pipe 61 with a diagram showing the relationships between pressures and enthalpy. In Fig. 2, point "A" designates the state of the non-azeotrope refrigerant at the entrance on the high pressure side of the double-pipe type heat exchanger 63; point "B" designates the state of the refrigerant at the exit on the high pressure side of the heat exchanger 63 or the entrance of the second decompressing device 62; point "C" designates the state of the refrigerant at the entrance on the low pressure side of the heat exchanger 63 or the exit of the decompressing device 62; and point "D" designates the state of the refrigerant at the exit on the low pressure side of the heat exchanger 63. Because the heat exchanger 63 is designed to exchange heat between the high pressure refrigerant and the low pressure refrigerant sufficiently, and because the isothermal line is almost perpendicular at the liquid phase area as shown with the alternate long and short dash line in Fig. 2, the temperature of the refrigerant at the exit on the high pressure side of the heat exchanger 63 represented by the point "B" is cooled near to the temperature of the refrigerant at the entrance on the low pressure side of the heat exchanger 63 represented by the point "C". Furthermore, because the refrigerant passing through the second decompressing device 62 expands in the state of iso-enthalpy, almost all of the refrigerant at the entrance on the low pressure side of the heat exchanger 63 represented by the point "B" becomes the saturated liquid state in a low pressure. Next, the operation of the composition computing unit 20 will be described in connection with the vapor-liquid equilibrium diagram of Fig. 3. The unit 20 takes therein the temperature T1 and the pressure P1 of the refrigerant in a saturated liquid state of a low pressure at the exit of the second decompressing device 62 with the first temperature detector 11 and the first pressure detector 12. The saturated liquid temperature of the non-azeotrope refrigerant at the pressure P1 varies according to the circulation composition in the refrigerating cycle, or the circulation composition in the bypass pipe 61, as shown in Fig. 3. The circulation composition is represented by the weight ratio of the low boiling components of the non-azeotrope refrigerant. Consequently, the circulation composition α in the refrigerating cycle can be detected from the temperature T1 and the pressure P1 detected by the first temperature detector 11 and the first pressure detector 12 respectively by using the relationships shown in Fig. 3. Fig. 4 is a diagram showing the relationships among the saturated liquid temperatures T1, the pressures P1, and the circulation compositions α obtained from the vapor-liquid equilibrium diagram of the non-azeotrope refrigerant shown in Fig. 3. By memorizing these relationships in the composition computing unit 20 previously, the circulation composition α can be computed on the temperature T1 and the pressure P1. The relationships shown in Fig. 4 can be expressed in, for example, the following formula. α = (a•T12 + b•T1 + c) x (d•P12 + e•P1 + f) where a, b, c, d, e, and f respectively designates a constant. The composition computing unit 20 computes the circulation composition α by means of the aforementioned formula. The method of detecting the circulation composition concerns the saturated liquid state refrigerant at the entrance on the low pressure side of the heat exchanger 63, but the detection accuracy of the circulation composition is fully secured even if the refrigerant at the entrance does not reach to the saturated liquid state but comes to a two-phase state of vapor and liquid owing to the insufficient heat exchanging in the heat exchanger 63. This is why the changes of the equilibrium temperatures of the non-azeotrope refrigerant composed of, for example, "R32" and "R134a" to the change of the dryness thereof in the two-phase state of vapor and liquid is small as shown in Fig. 5. Fig. 5 is a diagram showing the changes of the equilibrium temperatures to the dryness X in two-phase state of vapor and liquid of the non-azeotrope refrigerant having been made by mixing "R32" and "R134a" in the pressure of 500 kilo-Pa at 25% and 75% in weight ratios respectively. As for "R32" and "R134a", the difference between the saturated liquid temperature (the temperature at X = 0) and the saturated vapor temperature (the temperature at X = 1) is a small value around 6°C, and the difference between the equilibrium temperature at 0.1 of X and the saturated liquid temperature is a small value around 0.8°C consequently. Therefore, even if the refrigerant at the entrance on the low pressure side of the heat exchanger 63 becomes the two-phase state of vapor and liquid, the dryness X of which is about 0.1, the difference between the temperature of the refrigerant in the two-phase state and the temperature of the refrigerant in the saturated liquid state is vary small in the circulation composition detecting method of the present embodiment, and consequently, the accuracy of detecting the circulation composition is practically secured sufficiently. The present embodiment uses the double-pipe type heat exchanger 63 for exchanging the heat thereof with the refrigerant on the low pressure side as a cooling means for the refrigerant on the high pressure side, but similar effects can be obtained by exchanging the heat by touching the pipe on the high pressure side and the pipe on the low pressure side to each other. The mixed refrigerant, which is a two-component system in the present embodiment, may be a multi-component system such as a three-component system for obtaining similar effects. EMBODIMENT 2 Fig. 6 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 second embodiment of the present invention. The embodiment uses a second decompressing device 120 using an electric expansion valve. At the entrance of the decompressing device 120 is equipped a second temperature detector 13 for detecting the temperature of the refrigerant at that place. The composition computing unit 20 has the function of computing the dryness of the refrigerant at the exit of the decompressing device 120 and the circulation composition of the non-azeotrope refrigerant in the refrigerating cycle on the temperatures and the pressures respectively detected by the first temperature detector 11, the first pressure detector 12, and the second temperature detector 13. Reference numeral 21 designates a control unit for the decompressing device 120, which unit 21 has the function of controlling the degree of opening of the electric expansion valve on the temperature at the exit of the decompressing device 120 detected by the first temperature detector 11 and the temperature at the exit on the low pressure side of the double-pipe type heat exchanger 63 detected by the second temperature detector 13. Next, the operation thereof will be described. A part of the vapor refrigerant in a high pressure having discharged from the compressor 1 flows into the bypass pipe 61 to exchange the heat thereof with low pressure refrigerants at the annular part of the heat exchanger 63 to be condensed into liquid. The liquid refrigerant is decompressed by the decompressing device 120 to flow into the inner tube of the heat exchanger 63 in the state of low pressure two-phase refrigerant of vapor and liquid, the dryness of which is X. Then, the two-phase refrigerant exchanges the heat thereof with the high pressure refrigerant in the annular part to be evaporated. The low pressure vapor refrigerant flows into the suction pipe of the compressor 1. Fig. 7 shows the changes of states of the refrigerant in the bypass pipe 61 with a diagram showing the relationships between pressures and enthalpy. In Fig. 7, point "A" designates the state of the refrigerant at the entrance on the high pressure side of the heat exchanger 63; point "B" designates the state of the refrigerant at the exit on the high pressure side of the heat exchanger 63, or the entrance of the second decompressing device 62; point "C" designates the state of the refrigerant at the entrance on the low pressure side of the heat exchanger 63, or the exit of the second decompressing device 62; and point "D" designates the state of the refrigerant at the exit on the low pressure side of the heat exchanger 63. The heat exchanger 63 is designed to exchange heat between the high pressure refrigerant and the low pressure refrigerant sufficiently, and designed so that the refrigerants, represented by point "B", at the exit on the high pressure side of the double-pipe type heat exchanger 63, or the entrance of the decompressing device 120 become a supercooled state. Next, the operation of the composition computing unit 20 will be described in connection with the flowchart shown in Fig. 8. When the unit 20 begins to operate, the unit 20 takes therein the temperature T1 and the pressure P1 of the refrigerant at the exit of the decompressing device 120, and the temperature T2 of the refrigerant at the entrance of the decompressing device 120, which temperatures T1, T2 and the pressure P1 are respectively detected by the first temperature detector 11, the second temperature detector 13, and the first pressure detector 12, at STEP ST1. Then, the circulation composition α in the refrigerating cycle is assumed as a certain value at STEP ST2, and the dryness X of the refrigerant at the exit of the decompressing device 120 is calculated on the assumed value a of the circulation composition, the temperature T2 at the entrance of the decompressing device 120, and the pressure P1 at the exit of the decompressing device 120 at STEP ST3. That is to say, because the refrigerant passing through the decompressing device 120 expands in the state of iso-enthalpy, the relationships shown in Fig. 9 exist in the temperature T2 at the entrance of the decompressing device 120, the pressure P2 at the exit of the decompressing device 120, and the dryness X. Accordingly, if the aforementioned relationships have been memorized in the composition computing unit 20 in advance as the following relational formula (1), the dryness X of the refrigerant at the exit of the decompressing device 120 can be computed on the temperature T2, the pressure P1, and the assumed circulation composition value α by using the formula (1). X = f1 (T2, P1, α) Furthermore, at STEP ST4, a circulation composition α' is calculated from the temperature T1, the pressure P1 of the refrigerant at the exit of the decompressing device 120, and the dryness X obtained at STEP ST3. Namely, the temperature of the non-azeotrope refrigerant in two-phase state of vapor and liquid, the dryness of which is X, at the pressure P1 varies in accordance with the circulation composition in the refrigerating cycle, or the circulation composition flowing through the bypass pipe 11, as shown in Fig. 10. Accordingly, the circulation composition α' in the refrigerating cycle can be calculated on the temperature T1, the pressure P1 at the exit of the decompressing device 120, and the dryness X by using the characteristic shown in Fig. 10. Fig. 11 shows the relationships of the circulation composition α to the temperature T1, the pressure P1 at the exit of the decompressing device 120, and the dryness X from the relationships shown in Fig. 10. Accordingly, by memorizing the relationships shown in Fig. 11 in the composition computing unit 20 as the following relational formula (2) in advance, the circulation composition α' can be calculated on the temperature T2, the pressure P1 at the exit of the decompressing device 120, and the dryness X by using the formula (2). α' = f2 (T1, P1, X) At STEP ST5, the circulation composition α' and the circulation composition α having been assumed previously are compared. If both of them are equal, the circulation composition is obtained as the α. If both of them are not equal, the circulation composition α is re-assumed at STEP ST6. Then, the composition computing unit 20 again returns to STEP ST3 to compute the aforementioned calculations and continue them until the circulation composition α' and the circulation composition α accord with each other. Next, the operation of the control unit 21 will be described. The unit 21 controls the degree of opening of the electric expansion valve of the decompressing device 120 so that the refrigerant at the exit on the high pressure side of the heat exchanger 63 surely becomes a supercooled state. That is to say, the unit 21 takes therein the temperature T1 at the exit of the decompressing device 120 detected by the first temperature detector 11 and the temperature T2 at the entrance of the decompressing device 120 detected by the second temperature detector 13, and computes the difference of them (or T2 - T1). The unit 21 further computes a modifying value of the degree of opening of the electric expansion valve of the decompressing device 120 with a feed back control such as the PID control so that the temperature difference become a prescribed value (for example 10°C) and below to output a command of the degree of opening to the decompressing device 120. Consequently, the refrigerant at the exit on the high pressure side of the heat exchanger 63 surely becomes supercooled condition, which makes it possible to minimize the quantity of flow of the refrigerant flowing through the bypass pipe 61 for minimizing the energy loss of the refrigerating cycle. Since the composition computing unit 20 of the present embodiment computes the circulation composition by calculating the dryness of the refrigerant at the exit of the decompressing device 120, the circulation composition surely can be detected even if the state of the operation of the refrigerating cycle has changed to change the quantity of heat exchanged by the heat exchanger 63. And also, since the quantity of the flow of the refrigerant flowing through the bypass pipe 61 is controlled by the decompressing device 120 so that the refrigerant at the exit on the high pressure side of the heat exchanger 63 surely becomes supercooled state, the circulation composition is surely detected, and the quantity of the flow of the refrigerant flowing through the bypass pipe 61 is minimized for enabling the energy loss of the refrigerating cycle to be minimum. EMBODIMENT 3 Fig. 12 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 third embodiment of the present invention. In Fig. 12, a heat-pump type refrigerant air-conditioner, which can heating and cooling air by switching a four-way type valve 31, is shown. Reference numeral 32 designates an outdoor heat exchanger that operates as a condenser at the time of air cooling and as an evaporator at the time of air heating; and numeral 41 designates an indoor heat exchanger that operates as an evaporator at the time of air cooling and as a condenser at the time of air heating. The construction of the bypass pipe 61, the composition computing unit 20, the control unit 21, etc., is the same as that of the embodiment 2. The principle of the detection of the circulation composition described as to the embodiment 10 is true in case of using the temperature and the pressure at the exit and the temperature at the entrance of the first decompressing device 3 in the main circuit, but because the directions of the flow of the refrigerant in the first decompressing device 3 are different in the cases of air cooling and air heating, a pair of a temperature detector and a pressure detector is needed at the exit and the entrance of the first decompressing device 3 respectively for detecting the circulation compositions at the time of air cooling and the time of air heating respectively. Thus four detectors are needed to be provided in all. But the control information detecting apparatus of the present embodiment can always detect the circulation composition with three detectors of the first temperature detector 11, the first pressure detector 12, and the second temperature detector 13 in the bypass pipe 61 despite at the time of air cooling or the time of air heating. That is to say, the present embodiment can detect the circulation composition at the time of air cooling and the time of air heating with fewer detectors in low costs. EMBODIMENT 4 Fig. 13 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 fourth embodiment of the present invention. The embodiment uses a second decompressing device 62 using a capillary tube. The operation of the composition computing unit 20 is similar to that of the embodiment 1, and consequently the description thereof is omitted. The embodiment can detect the circulation composition of the non-azeotrope refrigerant cheaply in cost by using the capillary tube cheaper than an electric expansion valve as the second decompressing device 62. EMBODIMENT 5 Fig. 14 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 fifth embodiment of the present invention. The embodiment uses a double-pipe type heat exchanger 63 that exchanges the heat thereof with surrounding air for cooling the high pressure refrigerant in the bypass pipe 61. The heat of the vapor of the refrigerant lead into the bypass pipe 61 is exchanged with the surrounding air by the heat exchanger 63 to be condensed into a liquid. The liquefied refrigerant is decompressed by the decompressing device 62 into a low pressure refrigerant to flow into the accumulator 5. The double-pipe type heat exchanger 63 is equipped with fins 64 on the surface of the pipe thereof, which a high pressure refrigerant flows in, for promoting the heat exchange with the surrounding air. The operation of the computing unit 20 is similar to that of the embodiment 10, and the operation thereof is omitted. The present embodiment uses the cheap pipe equipped with fins 64 as the refrigerating means thereof, therefore it can detect the circulation composition of the non-azeotrope refrigerant cheaply in costs. EMBODIMENT 6 Fig. 15 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 sixth embodiment of the present invention. A refrigeration air-conditioner composed of an outdoor unit and two indoor unit connected to the outdoor unit is shown in Fig. 15. In the figure, reference numeral 30 designates the outdoor unit comprising a compressor 1, a bypass pipe 61, an outdoor heat exchanger 32, an outdoor blower 33, and an accumulator 5. A second pressure detector 66 is equipped on the pipe on the discharge side of the compressor 1. Reference numeral 40 designates the indoor units comprising indoor heat exchangers 41a and 41b (hereinafter referred to as 41 generically) and first decompressing devices 3a and 3b (hereinafter referred to as 3 generically) using first electric expansion valves. Third heat exchangers 42a and 42b (hereinafter referred to as 42 generically) and fourth temperature detectors 43a and 43b (hereinafter referred to as 43 generically) are equipped at the entrances and the exits of the indoor heat exchangers 41 respectively. Reference numeral 61 designates the bypass pipe for connecting the discharge pipe of the compressor 1 with the suction pipe thereof. A second decompressing device 120 using an electric expansion valve is equipped at an intermediate position of the bypass pipe 61. Reference numeral 63 designates a cooling means for cooling the non-azeotrope refrigerant flowing from the high pressure side of the bypass pipe 61 into the second decompressing device 120. The cooling means 63 is composed as a double-pipe type heat exchanger for exchanging the heat thereof with the low pressure side of the bypass pipe 61. Furthermore, a first temperature detector 11 for detecting the temperature of the refrigerant and a first pressure detector 12 for detecting the pressure of the refrigerant are equipped at the exit of the second decompressing device 120. A second temperature detector 13 for detecting the temperature of the refrigerant is equipped at the entrance of the decompressing device 120. An indoor blower is also equipped in the embodiment, but is omitted to be shown in Fig. 15. The composition computing unit 20 has the function of computing the dryness of the refrigerant at the exit of the decompressing device 120 in the bypass pipe 61 and the circulation composition of the refrigerant in the refrigerating cycle on the temperatures and the pressure detected by the temperature detectors 11, 13 and the pressure detector 12 respectively. Reference numeral 21 designates a control unit into which the circulation composition signals from the composition computing unit 20 and the signals from the first temperature detector 11, the first pressure detector 12, the second pressure detector 66, the third temperature detectors 42 and the fourth temperature detectors 43 in the indoor units 40 are input. The control unit 21 calculates the number of revolutions of the compressor 1, the number of the revolutions of the outdoor blower 33, the degrees of opening of the electric expansion valves of the first decompressing devices 3 of the indoor units 40, and the degree of opening of the electric expansion valve of the second decompressing device 120 of the bypass pipe 61 in accordance with the circulation composition on the input signals to transmit commands to the compressor 1, the outdoor blower 33, the first decompressing devices 3, and the second decompressing device 120 respectively. The compressor 1, the outdoor blower 33, and the first and the second decompressing devices 3 and 120 receive the command values transmitted from the control unit 21 to control the numbers of revolutions of them or the degrees of opening of their electric expansion valves. Reference numeral 22 designates a comparator, into which circulation composition signals are input from the composition computing unit 20 to compare whether the circulation compositions are within a predetermined range or not. The comparator 22 transmits a warning signal to the warning device 23, which is connected thereto, when the circulation composition is out of the predetermined range. These comparator 22 and warning device 23 are a part of the control-information detecting apparatus of the present embodiment. Next, the operation of the present embodiment thus constructed will be described in connection with the block diagram of Fig. 15 and the control block diagram of Fig. 16. The composition computing unit 20 takes therein the signals from the first temperature detector 11, the first pressure detector 12 and the second temperature detector 13, all of which are equipped on the bypass pipe 61, to calculate the dryness X of the refrigerant at the exit of the second decompressing device 120 similarly to the method of the embodiment 10 for computing the circulation composition α in the refrigerating cycle. The control unit 21 computes the command of the optimum number of revolutions of the compressor 1, the command of the optimum number of revolutions of the outdoor blower 33, the commands of the optimum degree of opening of the first decompressing devices 3, and the command of the optimum degree of opening of the second decompressing device 120 respectively in accordance with the computed circulation composition α. At first, the operation of air heating of the air-conditioner will be described. At the time of the operation of air heating, the refrigerant circulates to the directions shown by the arrows of the full lines in Fig. 15. In this case, the outdoor heat exchanger 32 operate as an evaporator, and the indoor heat exchangers 40 operate as condensers for air heating. The number of revolutions of the compressor 1 is controlled so that the pressure of condensation accords with a desired value, at which the condensation temperature Tc becomes, for example, 50°C. If the condensation temperature of a non-azeotrope refrigerant is defined as an average value of the saturated vapor temperature thereof and the saturated liquid temperature thereof, the desired value of the condensation pressure Pc at which the condensation temperature Tc becomes 50°C is uniquely determined in accordance with the circulation composition α as shown in Fig. 17. Accordingly, by memorizing the relationship shown in Fig. 17 in the control unit 21 as the following relational formula (3), the control unit 21 can compute the desired value of the condensation pressure Pc by using the relational formula (3) on the circulation composition signals α transmitted from the composition computing unit 20. Pc = f3 (α) The unit 21 further computes a modifying value to the number of revolutions of the compressor 1 in accordance with the difference between the pressure P2 detected by the second pressure detector 66 and the desired value of the condensation pressure Pc by using a feedback control such as the PID control to output a command of the number of revolutions to the compressor 1. The number of revolutions of the outdoor blower 33 is controlled so that the evaporation pressure accords with a desired value, at which the evaporation temperature Te becomes 0°C. If the evaporation temperature of a non-azeotrope refrigerant is defined as an average value of the saturated vapor temperature thereof and the saturated liquid temperature thereof, the desired value of the evaporation pressure Pe, at which the evaporation temperature Te becomes 0°C, is uniquely determined in accordance with the circulation composition α as shown in Fig. 18. Accordingly, by memorizing the relationship shown in Fig. 18 in the control unit 21 as the following relational formula (4), the control unit 21 can compute the desired value of the evaporation pressure Pe by using the relational formula (4) on the circulation composition signals α transmitted from the composition computing unit 20. Pe = f4 (α) The control unit 21 further computes a modifying value to the number of revolutions of the outdoor blower 33 in accordance with the difference between the pressure P1 detected by the first pressure detector 12 and the desired value of the evaporation pressure Pe by using a feedback control such as the PID control to output a command of the number of revolutions to the outdoor blower 33. The degrees of opening of the electric expansion valves of the first decompressing devices 3 are controlled so that the degrees of supercooling at the exits of the indoor heat exchangers 40 become a predetermined value, for example, 5°C. The degrees of supercooling can be obtained as the differences between the saturated liquid temperatures at the pressures in the indoor heat exchangers 40 and the temperatures at the exits of the heat exchangers 40, and the saturated liquid temperatures can be obtained as functions of pressures and circulation compositions as shown in Fig. 19. Accordingly, by memorizing the relationships shown in Fig. 19 in the control unit 21 as the following relational formula (5), the control unit 21 can compute the saturated liquid temperature Tbub and the degrees of supercooling (Tbub - T4) at the exits of the indoor heat exchangers 40 by using the relational expression (5) on the circulation composition signals transmitted from the composition computing unit 20, the pressure signals P2 transmitted from the second pressure detector 66, and the temperature signals T4 transmitted from the third temperature detector 42. Tbub = f5 (P2, α) The control unit 21 further computes a modifying value to the degrees of opening of the electric expansion valves of the first decompressing devices 3 in accordance with the differences between the degrees of supercooling at the exits and a predetermined value (5°C) by using a feedback control such as the PID control to output commands of the degrees of opening of the electric expansion valves to the decompressing devices 3. The degree of opening of the electric expansion valve of the second decompressing device 120 is controlled so that the refrigerant at the high pressure side exit of the double-pipe type heat exchanger 63 surely becomes a supercooled state. That is to say, the control unit 21 takes therein the temperature T1 at the exit of the second decompressing device 120, which is detected by the first temperature detector 11, and the temperature T2 at the entrance of the second decompressing device 120, which is detected by the second temperature detector 13, to calculate the temperature difference (T2 - T1). The control unit 21 further computes a modifying value to the degree of opening of the decompressing device 120 by using a feed back control such as the PID control so that the temperature difference becomes a predetermined value (for example 10°C) and below to output a command of the degree of opening to the decompressing device 120. As a result, the refrigerant at the high pressure side exit of the heat exchanger 63 surely becomes a supercooled state, and the quantity of the refrigerant flowing in the bypass pipe 61 becomes minimum, which enables the energy loss of the refrigerating cycle to be minimum. On the other hand, at the time of the operation of air cooling, the refrigerant circulates to the directions shown by the arrows of the dotted lines in Fig. 15. The outdoor heat exchanger 33 operates as a compressor, and the indoor heat exchangers 40 operate as evaporators for air cooling. The number of revolutions of the compressor 1 is controlled so that the pressure of evaporation accords with a desired value, at which the evaporation temperature Te becomes, for example, 0°C. The desired value Pe of the evaporation pressure is determined in conformity with the relational formula (4) similarly in the operation of air heating. Accordingly, the control unit 21 can compute the desired value Pe of the evaporation pressure by using the circulation composition signal α transmitted from the composition computing unit 20. The unit 21 further computes a modifying value to the number of revolutions of the compressor 1 in accordance with the difference between the pressure P1 detected by the first pressure detector 12 and the desired value Pe by using a feedback control such as the PID control to output a command of the number of revolutions to the compressor 1. The number of revolutions of the outdoor blower 33 is controlled so that the condensation pressure accords with a desired value, at which the condensation temperature Tc becomes, for example, 50°C. The desired value Pc of the condensation pressure is determined in conformity with the relational formula (3) similarly in the operation of air heating. Accordingly, the control unit 21 can compute the desired value Pc by using the circulation composition signal α transmitted from the composition computing unit 20. The unit 21 further computes a modifying value to the number of revolutions of the outdoor blower 33 in accordance with the difference between the pressure P2 detected by the second pressure detector 66 and the desired value Pc by using a feedback control such as the PID control to output a command of the number of revolutions to the outdoor blower 33. The degrees of opening of the electric expansion valves of the first decompressing devices 3 are controlled so that the degrees of superheating at the exits of the indoor heat exchangers 40 become a predetermined value, for example, 5°C. The degrees of superheating can be obtained as the differences between the saturated vapor temperatures at the pressures in the indoor heat exchangers 40 and the temperatures at the exits of the indoor heat exchangers 40, and the saturated vapor temperatures can be obtained as the functions of pressures and circulation compositions as shown in Fig. 20. Accordingly, by memorizing the relationships shown in Fig. 20 in the control unit 21 as the relational formula (6), the unit 21 can compute the saturated vapor temperature Tdew and the degree of superheating (T5 - Tdew) at the exits of the indoor heat exchangers 40 by using the relational formula (6) on the circulation composition α transmitted from the composition computing unit 20, the pressure signal P1 transmitted from the first pressure detector 12, and the temperature signal T5 transmitted from the fourth temperature detector 43. Tdew = f6 (P, α) The control unit 21 further computes modifying values to the degrees of opening of the electric expansion valves of the first decompressing devices 3 in accordance with the difference between the degree of supercooling at the exits and a predetermined value (5°C) by using a feedback control such as the PID control to output commands of the degrees of opening of the electric expansion valves to the first decompressing devices 3. Since the control of the degree of opening of the second decompressing device 120 is similar to that at the time of the operation of air heating, the description thereof is omitted. Next, the operation of the comparator 22 will be described. The comparator 22 takes therein circulation composition signals from the composition computing unit 20 to judge whether the circulation compositions are within a previously memorized appropriate circulation composition range or not. The operation of the refrigeration air-conditioner is continued as it is if the circulation composition is in the appropriate circulation composition range. On the other hand, if the circulation composition has changed owing to the leakage of the refrigerant during the operation of the air-conditioner, or if the circulation composition has changed owing to an error operation at the time of filling up the refrigerant, the comparator 22 judges that the circulation composition is out of the previously memorized appropriate circulation composition range to transmit a warning signal to the warning device 23. The warning device 23 having received the warning signal sends out a warning for a predetermined time for warning the operator that the circulation composition of the non-azeotrope refrigerant of the air-conditioner is out of the appropriate range. The present embodiment controls the number of revolutions of the outdoor blower 33 so that the values detected by the first pressure detector 12 accord with the desired value of the evaporation pressure, which is computed from the circulation composition, but similar effects can be obtained by providing a temperature detector at the entrance of the outdoor heat exchanger 32 and controlling so that the temperature detected by the temperature detector becomes a predetermined value (for example 0°C). The embodiment controls the degrees of opening of the electric valves of the first decompressing devices 3 at the time of the operation of air cooling so that the degrees of superheating at the exits of the indoor heat exchangers 40 become a predetermined value (for example 5°C), but similar effects can be obtained also by controlling them so that the differences between the temperatures at the entrances and the temperatures at the exits of the indoor heat exchangers 40 become a predetermined value (for example 10°C), that is to say, so that the temperature differences between the temperatures detected by the fourth temperature detectors 43 and the temperatures detected by the third temperature detectors 42 become the predetermined value. The air-conditioner of the embodiment has one outdoor unit 30 and two indoor units 40 connected to the outdoor unit 30, but the number of the indoor units 40 is not restricted to two. Similar effects can be obtained also by connecting only one indoor unit or three indoor units or more to the outdoor unit. It will be appreciated that, in accordance with the present invention, the composition computing unit of the 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 first temperature detector and the pressure detector of the apparatus, 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) to one another, in series; the air-conditioner further having a bypass pipe (61) connected between a high pressure region of the cycle, between an exit of said compressor (1) and said condenser (2), and a low pressure region of the cycle, between said evaporator (4) and an entrance of said compressor (1), a second decompressing device (62, 120) being located within said bypass pipe (61), and a cooling means (63) for cooling the non-azeotrope refrigerant flowing from a high pressure side of said bypass pipe (61) into said second decompressing device (62); and a control-information detecting apparatus comprising: a first temperature detector (11) for detecting a temperature of the refrigerant on a low pressure side at an exit of said second decompressing device (62), a pressure detector (12) for detecting a pressure of the refrigerant on the low pressure side at the exit of the second decompressing device (62), and a composition computing unit (20) for computing a composition of the refrigerant circulating through said refrigerating cycle on signals respectively detected by said first temperature detector (11) and said pressure detector (12). An air-conditioner as claimed in Claim 1, wherein said cooling means (63) is constructed so as to exchange heat between the high pressure side and a low pressure side of said bypass pipe (61). An air-conditioner as claimed in Claim 1, further comprising a second temperature detector (13) for detecting a temperature of the refrigerant on the high pressure side at an entrance of said second decompressing device (120); wherein said composition computing unit (20) computes a composition of the refrigerant circulating through said refrigerating cycle on signals respectively detected by said first temperature detector (11), said pressure detector (12), and said second temperature detector (13). An air-conditioner as claimed in Claim 1, further comprising: a comparison operation means (22) for generating a warning signal when the composition of the refrigerant computed by said composition computing unit (20) is out of a predetermined range, and a warning means (23) operating on the 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 DENKI K.K., MORIMOTO, OSAMU, C/O MITSUBISHI DENKI K.K., OKAZAKI, TAKASHI, C/O MITSUBISHI DENKI K.K., SUMIDA, YOSHIHIRO, C/O MITSUBISHI DENKI K.K.
Applicants: MITSUBISHI ELECTRIC CORP, MITSUBISHI DENKI KABUSHIKI KAISHA
Application year: 1995
Main classification: F25B49
IPC codes: F25B9