Air conditioner

Background of the Invention

Field of the Invention

The invention relates to a technique of effectively utilizing heat exchanging characteristics of respective air-side heat exchangers of an air conditioner, by means of supplying to the respective air-side heat exchangers a quantity of refrigerant appropriate for the amount of air flowing therethrough.

Background Art

Fig. 8 is an external view of, e.g., a conventional air conditioner, and Fig. 9 is a cross-sectional view of the same. As shown in Fig. 9, outlined arrows depict the flow of air, and solid-line arrows depict the flow of a refrigerant in refrigerant pipes.

In the air conditioner shown in Fig. 9, air-side heat exchangers 101a, 101b are disposed on the outside of the air conditioner. Disposed inside the air conditioner are air-side heat exchangers 102a, 102b which are provided in proximity to each other around lower sides of the air-side heat exchangers 101a, 101b and spaced apart from each other around upper sides of the air-side heat exchangers 101a, 101b. The four air-side heat exchangers 101a, 101b, 102a, and 102b are arranged in the form of an inverted letter M. A first refrigerant inlet pipe 103a connected to an expansion valve is connected to a middle section of a second refrigerant inlet pipe 103b. One end of the second refrigerant inlet pipe 103b is connected to a middle section of a third refrigerant inlet pipe 103c. The other end of the second refrigerant inlet pipe 103b is connected to a middle section of a fourth refrigerant inlet pipe 103d. Further, one end of the third refrigerant inlet pipe 103c is connected to the air-side heat exchanger 101a, and the other end of the same is connected to the air-side heat exchanger 102a. One end of the fourth refrigerant inlet pipe 103d is connected to the air-side heat exchanger 101b, and the other end of the same is connected to the air-side heat exchanger 102b.

Refrigerant outlet pipes are connected in the same manner as are the refrigerant inlet pipes. A first refrigerant outlet pipe 104a connected to a compressor is connected to a middle section of a second refrigerant outlet pipe 104b. One end of the second refrigerant outlet pipe 104b is connected to a middle section of a third refrigerant outlet pipe 104c, and the other end of the same is connected to a middle section of a fourth refrigerant outlet pipe 104d. One end of the third refrigerant outlet pipe 104c is connected to the air-side heat exchanger 101a, and the other end of the same is connected to the air-side heat exchanger 102a. One end of the fourth refrigerant outlet pipe 104d is connected to the air-side heat exchanger 101b, and the other end of the same is connected to the air-side heat exchanger 102b.

A blower 105a is disposed on an upper side of the air-side heat exchanger 102a, and another blower 105b is disposed on an upper side of the air-side heat exchanger 102b.

Operation of the air conditioner will now be described. Here, the air-side heat exchangers 101a, 101b disposed outside and the air-side heat exchangers 102a, 102b disposed inside are assumed to be utilized as evaporators. As shown in Fig. 9, a refrigerant, which has been converted into a two-phase gas, flows into the air-side heat exchangers 101a, 101b, 102a, and 102b by way of the refrigerant inlet pipes 103a through 103d disposed on the inlet sides of the air-side heat exchangers. Here, heat is exchanged between air (outside air) and the refrigerant flowing through the air-side heat exchangers, by means of the blowers 105a, 105b. As a result of heat being absorbed from air (outside air), a refrigerant is evaporated and returned to the compressor by way of the refrigerant outlet pipes 104a through 104d disposed on the outlet sides of the air-side heat exchangers.

The air conditioner is generally installed on a rooftop of a building. As a result of a recent increase in air-conditioning load associated with buildings being provided with intelligence functions, demand exists for a compact air conditioner and concentrated installation of the air conditioners in order to satisfy two necessities; namely, a necessity for installing a larger number of air conditioners in the same footprint on a rooftop than are installed conventionally; and a necessity for ensuring a space to be used for effectively utilizing a rooftop as a parking lot. In relation to realization of a compact air conditioner, air conditioner manufacturers promote development of compact air conditioners. In relation to concentrated installation of air conditioners, when three air conditioners having a structure such as that shown in Fig. 9 are to be installed, the air conditioners must be spaced a given distance away from each other in such a manner as shown in Fig. 10 in order to ensure inflow of air into the outside air-side heat exchangers 101a, 101b, because the air-side heat exchangers 101a, 101b installed outside are installed upright. In general, in the case of an air conditioner having refrigerating power of the 300 kW class, air conditioners must be spaced 2 meters (approx. 2.188 yards) to 3 meters (approx. 3.282 yards) away from each other.

As shown in Fig. 11, a conceivable method to solve this problem is to install air conditioners in which the air-side heat exchangers 101a, 101b, 102a, and 102b are installed in the shape of the letter W, in such a manner as shown in Fig. 12. However, the air which flows into the air-side heat exchangers 102a, 102b installed inside the air conditioner passes through pipes disposed in a lower part of the air conditioner, a location where the compressor is installed, or narrow inlet ports formed in side surfaces of the air conditioner. For these reasons, air duct resistance of the internally-installed air-side heat exchangers 102a, 102b becomes greater than air duct resistance of the externally-installed air-side heat exchangers 101a, 101b.

A substantially equal quantity of refrigerant flows into each of the air-side heat exchangers. Hence, if the quantity of refrigerant to flow is set in agreement with the heat exchangers 102a, 102b, the external air-side heat exchangers 101a, 101b become deficient in supply of refrigerant. The refrigerant located at exits of the air-side heat exchangers is greatly superheated and becomes a dry gas. Conversely, if the quantity of flowing refrigerant is set in agreement with the external heat exchangers 101a, 101b, the internal air-side heat exchangers 102a, 102b are supplied with an excessive quantity of refrigerant. As a result, heat is not sufficiently exchanged between air and the refrigerant, thereby lowering an evaporating temperature. The refrigerant located at the exits of the air-side heat exchangers becomes a wet gas, which is likely to induce a liquid back phenomenon. As mentioned above, in the air conditioner, the air-side heat exchangers which act as evaporators are not effectively utilized, thereby posing difficulty in realizing design performance. When the air conditioners are operated at low outside air temperatures, the quantity of air passing through the internal heat exchangers becomes deficient. Hence, the evaporation temperature of the internal air-side heat exchangers is lowered, and the heat exchangers become prone to frost formation. For this reason, the air conditioners frequently perform defrosting operations at time intervals of about a half-hour or an hour, thus impeding a heating operation.

A method of making the quantity of air flowing into air heat exchangers as uniform as possible is described as a solution to the foregoing problem in Japanese Patent Application Laid-Open No. 170030/1998.

Fig. 13 is an external view of an air conditioner described in Japanese Patent Application Laid-Open No. 170030/1998. Four air-side heat exchangers 101a, 101b, 102a, and 102b are arranged in the form of the letter W. Further, with a view toward correcting and making uniform a distribution of velocity of wind flowing into the air-side heat exchangers, which becomes non-uniform with respect to the vertical direction, the air conditioner is provided with covers 106a and 106b and partition walls 107, 108, 109 placed in an outside air inlet channel.

However, under the method of reducing the quantity of air flowing into the external air-side heat exchangers by provision of such resistance, to thereby render the quantity of air flowing uniform with that of air flowing into the internal air-side heat exchangers, the total quantity of air flowing into the overall air-side heat exchangers drops, thereby deteriorating performance of the air-side heat exchangers. Moreover, since the method involves provision of the partition walls in the air conditioner, the method becomes disadvantageous in terms of cost.

The invention has been conceived to solve the problem set forth and aims at providing an air conditioner which can prevent a drop in performance that would otherwise be caused by variations in the quantity of air flowing into respective air-side heat exchangers and which can be realized inexpensively.

Summary of the Invention

According to one aspect of the present invention, an air conditioner has a W-shaped heat exchanger unit, and the W-shaped heat exchanger unit includes two V-shaped heat exchanger units. Each of the V-shaped heat exchanger unit is constituted by combination of two heat exchangers arranged such that lower sides of the heat exchangers are made closely proximate to each other and upper sides of the heat exchangers are spaced apart from each other. Further, blowers 5a/5b are disposed in an upper portion of the W-shaped heat exchanger unit. Further, refrigerant flow rate regulators are provided at refrigerant inlet pipes of the heat exchangers disposed at the inside of the W-shaped arrangement for regulating the flow rate of refrigerant to flow.

In another aspect of the invention, the air conditioner further comprises temperature sensors disposed at refrigerant outlet pipes of heat exchangers arranged at the inside of the W-shaped arrangement. A controller is proveided for controlling the flow rate of refrigerant of the refrigerant flow rate regulators on the basis of the temperature data sensed by the temperature sensors.

In another aspect of the invention, two blowers are disposed in respective upper portions of the V-shaped heat exchanger unit and each blower is disposed nearer to the internally-located heat exchanger than to the the outside-located heat exchanger of the V-shaped heat exchanger unit.

Other and further objects, features and advantages of the invention will appear more fully from the following description.

Brief Description of the Drawings

Fig. 1 is an external view showing an air conditioner according to a first embodiment of the present invention.

Fig. 2 is a cross-sectional view of the air conditioner cut along a plane perpendicular to air-side heat exchangers.

Fig. 3 is a refrigerant pipe schematic flow diagram showing an air conditioner according to a first embodiment of the invention.

Fig. 4 is a comparison chart showing a comparison between performances of the present invention and of a conventional technique.

Fig. 5 is a refrigerant pipe schematic flow diagram showing an air conditioner according to a second embodiment of the invention.

Fig. 6 is a refrigerant pipe schematic flow diagram showing an air conditioner according to a third embodiment of the invention.

Fig. 7 is a cross-sectional view showing an air conditioner according to a fourth embodiment of the invention.

Fig. 8 is an external view of a conventional air conditioner.

Fig. 9 is a cross-sectional view of a conventional air conditioner.

Fig. 10 shows an installation of air conditioners in a conventional technique.

Fig. 11 shows an installation of heat exchangers in an air conditioner.

Fig. 12 shows an installation of air conditioners in a conventional technique.

Fig. 13 is an external view of a conventional air conditioner.

Detailed Description of the Preferred Embodiments

First Embodiment

A first embodiment of the present invention will now be described by reference to drawings.

Fig. 1 is an external view showing an air conditioner according to a first embodiment of the present invention; and Fig. 2 is a cross-sectional view of the air conditioner when the air conditioner is cut along a plane perpendicular to air-side heat exchangers.

As shown in Fig. 2, air-side heat exchangers 1a, 1b are disposed on the outside of the air conditioner, and air-side heat exchangers 2a, 2b connected to lower sides of the respective air-side heat exchangers 1a, 1b are disposed inside the air conditioner, whereby four air-side heat exchangers are disposed in the form of the letter W. A first refrigerant inlet pipe 3a connected to an expansion valve (not shown) is connected to a middle section of a second refrigerant inlet pipe 3b. One end of the second refrigerant inlet pipe 3b is connected to a middle section of a third refrigerant inlet pipe 3c, and the other end of the same is connected to a middle section of a fourth refrigerant inlet pipe 3d. Further, one end of the third refrigerant inlet pipe 3c is connected to the air-side heat exchanger 1a, and the other end of the same is connected to the air-side heat exchanger 2a. One end of the fourth refrigerant inlet pipe 3d is connected to the air-side heat exchanger 1b, and the other end of the same is connected to the air-side heat exchanger 2b.

Refrigerant outlet pipes are connected in the same manner as are the refrigerant inlet pipes. A first refrigerant outlet pipe 4a connected to a compressor (not shown) is connected to a middle section of a second refrigerant outlet pipe 4b. One end of the first refrigerant outlet pipe 4b is connected to a middle section of a third refrigerant outlet pipe 4c, and the other end of the same is connected to a middle section of a fourth refrigerant outlet pipe 4d. Further, one end of the third refrigerant outlet pipe 4c is connected to the air-side heat exchanger 1a, and the other end of the same is connected to the air-side heat exchanger 2a. One end of the fourth refrigerant outlet pipe 4d is connected to the air-side heat exchanger 1b, and the other end of the same is connected to the air-side heat exchanger 2b.

Moreover, a blower 5a is disposed at an elevated position in an upper part of a space defined between the air-side heat exchangers 1a, 2a, and another blower 5b is disposed at an elevated position in an upper part of a space defined between the air-side heat exchangers 1b, 2b. A throttle resistor 6a having a fixed throttle level is provided at a position on the third refrigerant inlet pipe 3c closer to the air-side heat exchanger 2a than to a junction between the third refrigerant inlet pipe 3c and the second refrigerant inlet pipe 3b. A throttle resistor 6b having a fixed throttle level is provided at a position on the fourth refrigerant inlet pipe 3d closer to the air-side heat exchanger 2b than to a junction between the fourth refrigerant inlet pipe 3d and the second refrigerant inlet pipe 3b.

Flow of the refrigerant in the air conditioner shown in Fig. 2 will now be described by reference to a refrigerant pipe schematic flow diagram shown in Fig. 3. Here, the air-side heat exchangers 1a, 1b, 2a, and 2b of interest are utilized as evaporators.

As shown in Fig. 3, the refrigerant that has been converted into a two-phase gas by means of an expansion valve (not shown) flows into the air-side heat exchangers 1a, 1b, 2a, 2b by way of the refrigerant inlet pipes 3a through 3d located on the inlet sides of the air-side heat exchangers and by way of the throttle resistors 6a, 6b disposed in the internal air-side heat exchangers 2a, 2b. Air is supplied by the blowers 5a, 5b, whereby the air flows through the air-side heat exchangers. Heat is exchanged between air (outside air) and the refrigerant flowing through the air-side heat exchangers, thereby absorbing heat from air (outside air). The refrigerant then evaporates and returns to the compressor (not shown) by way of the refrigerant outlet pipes 4a through 4d disposed on the outlet sides of the air-side heat exchangers.

At this time, all exterior surfaces of the external air-side heat exchangers 1a, 1b are open (i.e., housings of the heat exchangers 1a, 1b are not partitioned and are exposed to outside air). Hence, air can be caused to pass through the exterior surfaces. In contrast, air can be caused to flow into the internal air-side heat exchangers 2a, 2b by way of only a space released in a lower part of the air-side heat exchangers (denoted by reference numeral 1 in Fig. 1) and only a clearance (denoted by reference numeral 2 in Fig. 1) defined between walls of the housings perpendicular to the air-side heat exchangers. Provided that the quantity of air flowing through the external air-side heat exchangers 1a, 1b is taken as 100%, the quantity of air flowing through the internal air-side heat exchangers 2a, 2b assumes a value of 60 to 70%. The quantity of refrigerant flowing through the internal air-side heat exchangers 2a, 2b is controlled so as to become 60 to 70% the quantity of refrigerant flowing through the external air-side heat exchangers 1a, 1b, by means of the throttle resistors 6a, 6b having fixed throttle levels, thereby effectively utilizing the heat exchange characteristics of the respective air-side heat exchangers. More specifically, a larger quantity of refrigerant is caused to flow to air-side heat exchangers through which a large quantity of air flows, and a smaller quantity of refrigerant is caused to flow to air-side heat exchangers through which a smaller quantity of air flows. Thus, a refrigerant is controlled such that the refrigerants exiting the respective air-side heat exchangers achieve an equivalent state.

Fig. 4 is a comparison chart showing a comparison between a case where the quantity of refrigerant flowing through the air-side heat exchangers 2a, 2b installed inside is regulated and a casewhere the quantity of refrigerant is not regulated.

As can be seen from Fig. 4, as a result of adoption of the method of the present invention, the heat exchange efficiency of an overall W-shaped heat exchanger unit consisting of the air-side heat exchangers 1a, 1b, 2a, and 2b is improved. In contrast with a case where the quantity of refrigerant flowing through the internally-installed heat exchangers 2a, 2b is not regulated, the power of the air conditioner is improved by about 5%. Further, during operation of the air conditioner at a low outside air temperature, a drop in the evaporation temperatures of the air-side heat exchangers 2a, 2b can be prevented. A test that was conducted shows that a time interval between defrosting operations can be prolonged to about two hours.

A refrigerant flow rate regulator corresponds to throttle resistors having fixed throttle levels. Hence, the only requirement is to add only fixed throttles to a conventional air conditioner, thus enabling inexpensive improvements to the air conditioner.

Here, the case where the air-side heat exchangers 1a, 1b, 2a, 2b are utilized as evaporators has been described. However, the embodiment can also be applied to a case where air-side heat exchangers are utilized as condensers.

Second Embodiment

Fig. 5 is a refrigerant pipe schematic flow diagram showing an air conditioner according to a second embodiment of the invention. The air conditioner is modified and analogous to that shown in Fig. 3. A refrigerant flow rate regulator 7a whose flow rate is variable is provided at a position on the third refrigerant inlet pipe 3c closer to the air-side heat exchanger 2a than to a junction between the third refrigerant inlet pipe 3c and the second refrigerant inlet pipe 3b. A refrigerant flow rate regulator 7b whose flow rate is variable is provided at a position on the fourth refrigerant inlet pipe 3d closer to the air-side heat exchanger 2b than to a junction between the fourth refrigerant inlet pipe 3d and the second refrigerant inlet pipe 3b. Further, a temperature sensor 8a is disposed at a position on the third refrigerant outlet pipe 4c closer to the air-side heat exchanger 1a than to a junction between the third refrigerant outlet pipe 4c and the second refrigerant outlet pipe 4b; a temperature sensor 8b is disposed at a position on the third refrigerant outlet pipe 4c closer to the air-side heat exchanger 2a than to the junction between the third refrigerant outlet pipe 4c and the second refrigerant outlet pipe 4b; a temperature sensor 8c is disposed at a position on the fourth refrigerant outlet pipe 4d closer to the air-side heat exchanger 2b than to a junction between the fourth refrigerant outlet pipe 4d and the second refrigerant outlet pipe 4b; and a temperature sensor 8d is disposed at a position on the fourth refrigerant outlet pipe 4d closer to the air-side heat exchanger 1b than to a junction between the fourth refrigerant outlet pipe 4d and the second refrigerant outlet pipe 4b. In accordance with values sensed by the temperature sensors, a controller 9 controls openings of the refrigerant flow rate regulators 7a, 7b. In Fig. 5, those configurations, which are identical with or correspond to those shown in Fig. 3, are assigned the same reference numerals, and their explanations are omitted.

Operation of the air conditioner will now be described. Here, the air-side heat exchangers 1a, 1b, 2a, and 2b of interest are utilized as evaporators.

Flow of refrigerant shown in Fig. 5 is identical with that shown in Fig. 3 in connection with the first embodiment, and hence its explanation is omitted.

The temperature sensors 8a through 8d disposed on the third and fourth refrigerant outlet pipes 4c, 4d detect temperatures of exits for a refrigerant, and the thus-sensed temperatures are delivered to the controller 9. The controller 9 regulates the openings of the refrigerant flow rate regulators 7a, 7b such that the temperatures at the exits for a refrigerant detected by the temperature sensors become equal to each other. Specifically, when the temperature detected by the temperature sensor 8a is higher than that detected by the temperature sensor 8b, the controller 9 increases the opening of the refrigerant flow rate regulator 7a for reducing the temperature, thereby increasing the quantity of refrigerant flowing through the air-side heat exchanger 2a. Conversely, when the temperature detected by the temperature sensor 8a is lower than that detected by the temperature sensor 8b, the controller 9 decreases the opening of the refrigerant flow rate regulator 7a for increasing the temperature, thereby decreasing the quantity of refrigerant flowing through the air-side heat exchanger 2a.

The quantity of air flowing through the air-side heat exchangers is susceptible to the influence of an installation environment, such as weather conditions. A designed quantity of air is not always obtained. However, the air conditioner shown in Fig. 5 can regulate the quantity of refrigerant according to circumstances, thereby performing efficient operation.

Here, the case, where the air-side heat exchangers 1a, 1b, 2a, and 2b are utilized as evaporators, has been described. However, the embodiment can also be applied to a case where the air-side heat exchangers are utilized as condensers.

The temperatures of the refrigerant exits of the externally-installed air-side heat exchangers 1a, 1b and those of the refrigerant exits of the internally-installed air-side heat exchangers 2a, 2b are detected. Here, provided that the air flowing through the air-side heat exchanger 1a and that flowing through the air-side heat exchanger 1b are substantially equal in quantity with each other and that the air flowing through the air-side heat exchanger 2a and that flowing through the air-side heat exchanger 2b are substantially equal in quantity with each other, the openings of the refrigerant flow rate regulators 7a, 7b may be regulated by reference to, e.g., the temperature of the refrigerant exit of the first air-side heat exchanger 1a and the temperature of the refrigerant exit of the second air-side heat exchanger 2a.

Third Embodiment

Fig. 6 is a refrigerant pipe schematic flow diagram showing an air conditioner according to a third embodiment of the invention. In the air conditioner shown in Fig. 6, a pressure sensor 10 is mounted on the first refrigerant outlet pipe 4a. On the basis of the temperatures sensed by the temperature sensors 8a through 8d and the pressure sensed by the pressure sensor 10, the controller 9 controls the openings of the refrigerant flow rate regulators 7a, 7b. In Fig. 6, those configurations, which are identical with or correspond to those shown in Fig. 5, are assigned the same reference numerals, and their explanations are omitted.

Operation of the air conditioner will now be described. Here, the air-side heat exchangers 1a, 1b, 2a, and 2b of interest are utilized as evaporators.

Flow of refrigerant shown in Fig. 6 is identical with that shown in Fig. 5 in connection with the second embodiment, and hence its explanation is omitted.

The temperature sensors 8a through 8d provided on the third and fourth refrigerant outlet pipes 4c, 4d detect temperatures of the exits for refrigerant, and the pressure sensor 10 provided at the first refrigerant outlet pipe 4a senses low pressure of the refrigerant. The thus-sensed temperatures and low pressure are delivered to the controller 9. The controller 9 determines the degree of refrigerant superheat at the exits of the respective air-side heat exchangers from the temperatures of the refrigerant exits detected from the respective air-side heat exchangers and the sensed low pressure. Refrigerant superheat are compared with each other, thereby regulating the openings of the refrigerant flow rate regulators 7a, 7b such that a uniform refrigerant superheat is achieved at the exits of the air-side heat exchangers. More specifically, when superheat at the refrigerant exit of the air-side heat exchanger 2a is higher than that of the refrigerant exit of the air-side heat exchanger 1a, the controller 9 increases the opening of the refrigerant flow rate regulator 7a for decreasing refrigerant superheat, thereby increasing the quantity of refrigerant flowing into the heat exchanger 2a.

Conversely, when refrigerant superheat at the refrigerant exit of the air-side heat exchanger 2a is lower than that of the refrigerant exit of the air-side heat exchanger 1a, the controller 9 decreases the opening of the refrigerant flow rate regulator 7a for increasing superheat, thereby reducing the opening of the refrigerant flow rate regulator 7a.

In such an air conditioner, the openings of the refrigerant flow regulators 7a, 7b are controlled by means of determining refrigerant superheat at the refrigerant exits. Hence, even when operating conditions have changed, highly efficient operation can be continued without fail as compared with a case where only temperatures of refrigerant exits are controlled.

Here, the case where the air-side heat exchangers 1a, 1b, 2a, and 2b are utilized as evaporators has been described. However, the embodiment can also be applied to a case where the air-side heat exchangers are utilized as condensers.

Fourth Embodiment

Fig. 7 is a cross-sectional view showing an air conditioner according to a fourth embodiment of the invention.

In Fig. 7, the air-side heat exchangers 1a, 1b are situated outside, and the air-side heat exchangers 2a, 2b are situated inside. The four heat exchangers are arranged in the form of the letter W. A blower 5a is disposed at an elevated position in an upper part of a space defined between the air-side heat exchangers 1a, 2a, and another blower 5b is disposed at an elevated position in an upper part of a space defined between the air-side heat exchangers 1b, 2b. The air blowers 5a, 5b are disposed close to the internal air-side heat exchangers 2a, 2b respectively. More specifically, the blower 5a is situated such that a distance between the center of the blower 5a and the upper end of the heat exchanger 2a and a distance between the center of the blower 5a and the upper end of the heat exchanger 1a assume a 4:6 ratio. The blower 5b is situated such that a distance between the center of the blower 5b and the upper end of the heat exchanger 2b and a distance between the center of the blower 5b and the upper end of the heat exchanger 1b assume a 4:6 ratio.

As a result, the proportion of air flowing to the air-side heat exchangers 2a. 2b disposed at interior positions with respect to that flowing the externally-disposed air-side heat exchangers 1a, 1b can be increased, thereby diminishing an imbalance of the quantity of air.

Combinations of the above-mentioned aspects are considered to be within the scope of the invention. More specifically, an air conditioner with a W-shaped heat exchanger unit might have refrigerant flow rate regulators with fixed throttle levels according to the first embodiment and might also have air blowers which are disposed close to the internal air-side heat exchangers according to the fourth embodiment of the invention as described above. Furthermore, an air conditioner according to the first embodiment or fourth embodiment or a combination of these might also possess temperature sensors, a controller and refrigerant flow rate regulators with variable flow rate according to the third embodiment as described above, or might possess temperature and pressure sensors, a controller and refrigerant flow rate regulators with variable flow rate according to the fourth embodiment as described above, respectively.

The invention has been constructed in the manner as mentioned above and yields the following effects.

In an air conditioner according to the invention, refrigerant flow rate regulators for regulating the flow rate of a refrigerant to flow are provided at a pipe close to refrigerant entrances of heat exchanger disposed at the inside of a heat exchanger unit, wherein heat exchangers are disposed in the unit in the form of the letter W. A larger quantity of refrigerant is caused to flow into air-side heat exchangers in which a large quantity of air flows, and a smaller quantity of refrigerant is caused to flow into the air-side heat exchangers through which a smaller quantity of air flows. As a result, an equivalent state of refrigerant can be achieved at the exits of the respective air-side heat exchangers. Consequently, respective air-side heat exchangers are effectively utilized, thereby improving the overall power of the air conditioner. Further, unbalanced defrosting of the air-side heat exchangers through which a small quantity of air flows is also improved, thereby prolonging time intervals between defrosting operations.

Arefrigerant flow rate regulator corresponds to throttle resistors having fixed throttle levels. Hence, the only requirement is to add only fixed throttles to a conventional air conditioner, thus enabling inexpensive improvements to the air conditioner.

According to another aspect, an air conditioner has temperature sensors disposed at refrigerant outlet pipes of heat exchangers disposed at the inside of a W-shaped arrangement, and a controller for controlling the flow rate of refrigerant of flow rate regulators on the basis of temperature data detected by the temperature sensors. Even when a change has arisen in the temperatures of refrigerant exits as a result of variations in operating conditions, an improvement in the power of overall system can be maintained by means of control of throttle levels of the refrigerant flow rate regulators.

According to another aspect, an air conditioner has temperature sensors and pressure sensors disposed at refrigerant outlet pipes of heat exchangers disposed at the inside of a W-shaped arrangement, and a controller for controlling the flow rates of the refrigerant flow rate regulators on the basis of temperature data detected by the temperature sensors and pressure data detected by the pressure sensors. The power or capacity of the overall air conditioner can be maintained against changes in operating conditions more reliably than in a case where control is performed on the basis of only temperature data.

According to another aspect, in the air-conditioner of the invention, a distance between an upper side of an externally-located heat exchanger in a heat exchanger unit, in which heat exchangers are disposed in the form of the letter W, and the rotary shaft of a blower is made longer than a distance between an upper side of an internally-located heat exchanger in the heat exchanger unit and the rotary shaft of the blower. By virtue of this arrangement, the ratio of the quantity of air flowing into the internally-disposed heat exchangers to the quantity of air flowing into the heat exchangers disposed at the outside of the W-shaped arrangement can be increased.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may by practiced otherwise than as specifically described.