EP1662212A2

EP1662212A2 - Air conditioning system and method for controlling the same

Info

Publication number: EP1662212A2
Application number: EP05025039A
Authority: EP
Inventors: Chi Woo Song; Bong Soo Park; Ju Won Kim; Se Dong Chang; Baik Young Chung; Sai Kee Oh
Original assignee: LG Electronics Inc
Current assignee: LG Electronics Inc
Priority date: 2004-11-23
Filing date: 2005-11-16
Publication date: 2006-05-31
Also published as: EP1662212A3; KR100758902B1; US20060107683A1; CN1779391A; KR20060057226A

Abstract

The present invention relates to air conditioning systems, and more particularly, to an air conditioning system which can control a refrigerant flow rate to a heat exchanger exchanging heat with room air to be optimum; and a method for controlling the same.

The air conditioning system includes an outdoor heat exchange part including a compressor for compressing refrigerant, an outdoor heat exchanger for making the refrigerant to heat exchange with outdoor air, and an expansion device for expanding the refrigerant, an indoor heat exchange part including a pump for making refrigerant in a flow path independent from the outdoor heat exchange part to flow, at least one indoor heat exchanger for making the refrigerant heat exchange with room air, and a flow rate control device for controlling a flow rate of the refrigerant, and a hybrid heat exchange part for making the outdoor heat exchange part and the indoor heat exchange part, which are independent from each other, to heat exchange with each other.

According to this, the air conditioning system can be installed on a multistory building without limitation of a height of the building as far as a capacity of the pump permits. Moreover, even if a refrigerant pipe is long, the air conditioning system is applicable even to a system with a refrigerant pipe line longer than the related art as far as the capacity of the pump permits, and fine control of a room air temperature is possible.

Description

The present invention relates to air conditioning systems, and more particularly, to an air conditioning system which can control a refrigerant flow rate to a heat exchanger exchanging heat with room air to be optimum; and a method for controlling the same.
In general, the air conditioning system cools or heats a room by compressing, condensing, expanding, and evaporating refrigerant. In general, the air conditioning system is provided with a compressor, an indoor heat exchanger, an expansion device, and an outdoor heat exchanger.
In the air conditioning systems, there are a cooling system in which a refrigerating cycle is operated only in one direction, to supply only cold air to the room, and a heating/cooling system in which the refrigerating cycle is operated in two directions selectively, to supply cold air or warm air to the room.
Moreover, in the air conditioning systems, depending on a number of indoor units connected thereto, there are single air conditioning systems in each of which one indoor unit is connected to one outdoor unit, and multiple air conditioning systems in each of which a plurality of indoor units are connected to one outdoor unit.
The air conditioning system uses the compressor as a driving source for making the refrigerant to flow, and oil for lubricating the compressor.
However, if a height difference or a distance between the indoor heat exchanger, and the outdoor heat exchanger is great significantly, since the related art air conditioning system has a poor oil recovery rate, to fail in supply of an adequate rate of oil to the compressor, which is liable to result in damage to the compressor, development of an air conditioning system that can solve such a problem has been required.
Accordingly, the present invention is directed to an air conditioning system and a method for controlling the same that substantially obviates one or more problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide a an air conditioning system and a method for controlling the same, which is applicable even to a case a height difference or a distance between an indoor heat exchanger, and an outdoor heat exchanger is great significantly.
Another object of the present invention is to provide an air conditioning system and a method for controlling the same, which enables a fine control of a room temperature.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, an air conditioning system includes an outdoor heat exchange part including a compressor for compressing refrigerant, an outdoor heat exchanger for making the refrigerant to heat exchange with outdoor air, and an expansion device for expanding the refrigerant, an indoor heat exchange part including a pump for making refrigerant in a flow path independent from the outdoor heat exchange part to flow, a indoor heat exchanger for making the refrigerant heat exchange with room air, and a flow rate control device for controlling a flow rate of the refrigerant, and a hybrid heat exchange part for making the outdoor heat exchange part and - the indoor heat exchange part, which are independent from each other, to heat exchange with - each other.
The flow rate control device may include a temperature sensor for measuring temperatures of refrigerant flowing in the indoor heat exchanger, a controller for determining a degree of superheat or subcooling of the refrigerant with the temperatures measured at the temperature sensor, and a flow rate control valve for controlling a refrigerant flow rate to the indoor heat exchanger according to the determination of the controller.
The flow rate control valve may be mounted on a refrigerant inlet end of the indoor heat exchanger.
The flow rate control valve may be mounted on a refrigerant outlet end of the indoor heat exchanger.
The temperature sensors are mounted on the refrigerant inlet end, the refrigerant outlet end, and a predetermined portion between the refrigerant inlet end and the refrigerant outlet end of the indoor heat exchanger. Preferably, the predetermined portion between the refrigerant inlet end and the refrigerant outlet end of the indoor heat exchanger is a section in which the refrigerant flowing in the indoor heat exchanger is in a saturated state.
In the meantime, in another aspect of the present invention, a method for controlling an air conditioning system includes the steps of setting an ideal degree of superheat, and an ideal degree of subcooling at a controller, comparing the degree of superheat or subcooling set thus with a degree of superheat or subcooling measured thus, and controlling a flow rate of refrigerant flowing in an indoor heat exchanger according to a result of the step of comparing the degree of superheat or subcooling set thus with a degree of superheat or subcooling measured thus.
The degree of superheat or subcooling is a difference between a temperature of the refrigerant at the refrigerant outlet of the indoor heat exchanger and a saturation temperature of the refrigerant flowing in the indoor heat exchanger.
The step of controlling a flow rate of refrigerant flowing in an indoor heat exchanger includes the steps of increasing the flow rate of the refrigerant flowing in the indoor heat exchanger if the degree of superheat measured is higher than the degree of superheat set, and decreasing the flow rate of the refrigerant flowing in the indoor heat exchanger if the degree of superheat measured is lower than the degree of superheat set.
The step of controlling a flow rate of refrigerant flowing in an indoor heat exchanger includes the steps of increasing the flow rate of the refrigerant flowing in the indoor heat exchanger if the degree of subcooling measured is higher than the degree of subcooling set, and decreasing the flow rate of the refrigerant flowing in the indoor heat exchanger if the degree of subcooling measured is lower than the degree of subcooling set.
In another aspect of the present invention, an air conditioning system includes at least one first heat exchanger for heat exchange with room air, a second heat exchanger for transferring heat from the first heat exchanger to an outside of a refrigerant flow path having the first heat exchanger mounted therein, a pump for circulating the refrigerant to the first heat exchanger and the second heat exchanger, a third heat exchanger in a flow path independent both from the first heat exchanger and the second heat exchanger for heat exchange with the second heat exchanger, a fourth heat exchanger for transferring heat from the third heat exchanger to outdoor air, a compressor for compressing the refrigerant and circulating the refrigerant to the third heat exchanger and the fourth heat exchanger, a plurality of temperature sensors for measuring temperatures of the refrigerant flowing in the first heat exchanger, at least one flow rate control valve for controlling a flow rate of the refrigerant flowing in the first heat exchanger according to temperatures measured at the temperature sensors.
The temperature sensors are provided at a refrigerant inlet end and a refrigerant outlet end of the first heat exchanger, and at a predetermined portion between the refrigerant inlet end and the refrigerant outlet end, respectively. The temperature sensor provided at a predetermined portion between the refrigerant inlet end and the refrigerant outlet end measures a saturation temperature of the refrigerant flowing in the first heat exchanger.
The flow rate control valves are provided to a refrigerant inlet end and a refrigerant outlet end of the indoor heat exchanger. At the time of controlling a refrigerant flow rate, an opening of the flow rate control valve at the refrigerant inlet end of the first heat exchanger is adjusted, and an opening of the flow rate control valve at the refrigerant outlet end is opened to the maximum.
It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principle of the invention. In the drawings;
FIG. 1 illustrates a diagram of an air conditioning system in accordance with a preferred embodiment of the present invention, schematically;
FIG 2 illustrates a diagram of an indoor heat exchange part in the air conditioning system in FIG. 1, schematically;
FIG. 3 illustrates a flow chart showing the steps of a method for controlling an air conditioning system in accordance with a preferred embodiment of the present invention;
FIG. 4 illustrates a P-h diagram showing a state change of refrigerant in cooling operation of the air conditioning system in FIG 1; and
FIG. 5 illustrates a P-h diagram showing a state change of refrigerant in heating operation of the air conditioning system in FIG. 1.
Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.
FIGS. 1 and 2 illustrate diagrams each showing an air conditioning system in accordance with a preferred embodiment of the present invention.
Referring to FIGS. 1 and 2, the air conditioning system includes an indoor heat exchange part 10 for heat exchange with room air, an outdoor heat exchange-part 20 for heat exchange with outdoor air, and a hybrid heat exchanger 30 for making refrigerant in the indoor heat exchange part 10 and refrigerant in the outdoor heat exchange part 20 to heat exchange with each other.
The indoor heat exchange part 10 includes a first heat exchanger 14 for heat exchange with the room air, a pump 12 for circulating the refrigerant to the first heat exchanger 14, and a flow rate control device for controlling a flow rate of the refrigerant to the first heat exchanger 14.
The outdoor heat exchange part 20 has a refrigerant flow path independent from the indoor heat exchange part 10, and includes a fourth heat exchanger 24 for making the refrigerant to heat exchange with outdoor air, and a compressor 22 for compressing, and circulating the refrigerant to the fourth heat exchanger 24.
The outdoor heat exchange part 20 includes an expansion device 28 for expanding the refrigerant to drop a pressure of the refrigerant, and a flow controller 23 for controlling a flow direction of the refrigerant, additionally.
In the meantime, the outdoor heat exchange part 20 may have many variations as far as the part can transfer heat to the refrigerant in the indoor heat exchange part 10. As an example, the part may use warm water or waste heat as a heat source.
The hybrid heat exchange part 30 is configured such that the indoor heat exchange part 10 and the outdoor heat exchange part 20 having refrigerant flow paths independent from each other can heat exchange with each other, without mix of the refrigerant between the indoor heat exchange part 10 and the outdoor heat exchange part 20.
In order to enable the indoor heat exchanger 10 and the outdoor heat exchanger 20 make heat exchange with each other, the hybrid heat exchange part 30 includes a second heat exchanger 16 in a flow path of the indoor heat exchange part 10, and a third heat exchanger 26 in a flow path of the outdoor heat exchange part 20 for heat exchange with the second heat exchanger 16.
That is, the second heat exchanger 16 exchanges heat with the third heat exchanger 26 so that the indoor heat exchange part 10 and the outdoor heat exchange part 20 make heat exchange.
Moreover, the second heat exchanger 16 forms a refrigerant circulating flow path as a portion of the indoor heat exchange part 10, and the third heat exchanger 26 forms a refrigerant circulating flow path as a portion of the outdoor heat exchange part 20.
That is, the outdoor heat exchange part 20 forms a refrigerant flow path with the third heat exchanger 26, the fourth heat exchanger 24, the compressor 22, and the expansion device 28, and the indoor heat exchange part 10 forms a refrigerant flow path with the first heat exchanger 14, the second heat exchanger 16, the pump 12, and a flow rate control device.
The second heat exchanger 16 and the third heat exchanger 26 may have many variations. That is, the second heat exchanger 16 and the third heat exchanger 26 may be constructed of heat dissipation plates, or refrigerant tubes.
The hybrid heat exchange part 30 is configured to enable the second heat exchanger 16, and the third heat exchanger 26 in the outdoor heat exchange part to make thermal contact with each other.
For an example, the hybrid heat exchange part 30 may be constructed of a stack of a plurality of plate type heat conductive fins having the second heat exchanger 16 and the third heat exchanger 26 placed therebetween so as to be thermally in contact with each other.
Or alternatively, the hybrid heat exchange part 30 may has a structure in which the second heat exchanger and the third heat exchanger heat exchange with each other through a heat conductive fluid. Or, the second heat exchanger 16 and the third heat exchanger 26 are configured to have a form of a double tube.
In the meantime, the indoor heat exchange part 10 will be described in more detail.
As described before, the indoor heat exchange part 10 has a flow path independent from the outdoor heat exchange part 20, and includes a first heat exchanger 14, a pump 12, a flow rate control device, and a second heat exchanger 16 of the hybrid heat exchange part 30.
The indoor heat exchange part 10 has a pump 12 instead of a compressor as a driving source for making the refrigerant to flow, and has no separate expansion device for expanding the refrigerant. Owing to this, the indoor heat exchange part 10 requires no oil for operation of the compressor, and consequently, no operation for recovery of the refrigerant is required.
It is preferable that the pump 12 includes a pumping motor (not shown) and an impeller (not shown). Moreover, it is preferable that liquid refrigerant is supplied to the pump 12, for which, though not shown, a separate refrigerant storage tank may be provided between the hybrid heat exchange part 30 and the pump 12, for supplying refrigerant to the pump 12.
It is preferable that an inverter motor is employed as the pumping motor for controlling a rotation speed of the motor, to control a flow rate of the refrigerant. Of course, a constant speed motor having a constant rotation speed may be used.
In general, the first heat exchanger 14 is mounted in an indoor unit 15 installed in a room which requires cooling/heating. That is, the first heat exchanger 14 is an indoor heat exchanger for heat exchange with room air to cool or heat the room.
There may be a plurality of indoor units 15 installed in a room if required, and according to this, a plurality of indoor heat exchangers 14 may be mounted thereon.
The flow rate control device includes a plurality of temperature sensors 17a, 17b, and 17c for measuring temperatures of the refrigerant flowing through the indoor heat exchanger 14, a controller (not shown) for determining a degree of superheat or subcooling of the refrigerant in the indoor heat exchanger 14 with reference to the temperatures measured at the temperature sensors 17a, 17b, and 17c, and flow rate control valves 13a, and 13b for controlling a flow rate of the refrigerant to the indoor heat exchanger 14 according to the determination of the controller.
It is preferable that the flow rate control valve 13a, and 13b are solenoid valves each for controlling an opening of a flow passage with an electromagnetic force. Of course, there can be a variety of the flow rate control valves 13a, and 13b as far as the valve can control the opening of the flow passage.
Moreover, though it is preferable that the flow rate control valve 13a, and 13b are mounted on opposite ends of the indoor heat exchanger 14 into which the refrigerant flows in/out, the mounting positions of the flow rate control valve 13a, and 13b are not limited to this, but the flow rate control valve 13a, and 13b may be mounted only one of the opposite ends.
Mounting positions of the temperature sensors will be described with reference to FIG. 2.
It is preferable that the temperature sensors 17a, 17b, and 17c are mounted on an inlet 17a through which the refrigerant is introduced into the indoor heat exchanger 14, an outlet 17b through which the refrigerant is discharged from the indoor heat exchanger 14, and a predetermined portion 17c between the inlet 17a, and the outlet 17b, respectively.
That is, at least three temperature sensors 17a, 17b, and 17c are mounted on every indoor heat exchanger 14 mounted on the indoor unit 15.
Of the three temperature sensors 17a, 17b, and 17c, it is preferable that the temperature sensor 17c mounted on the predetermined portion between the inlet 17a, and the outlet 17b is mounted on one point where refrigerant in the indoor heat exchanger 14 is in a saturated state, so that the temperature sensor 17c can measure a temperature at a saturated state of the refrigerant.
The temperature at a saturated state is a temperature when there is no temperature change even if a phase of the refrigerant changes following heat exchange of the refrigerant.
The controller has an ideal degree of superheat and an ideal degree of subcooling preset thereto at a pressure of the refrigerant, and an actual degree of superheat and an actual degree of subcooling are calculated with temperatures measured at respective portions of the indoor heat exchanger 14 with the temperature sensors 17a, 17b, and 17c.
The degrees of superheat or subcooling is a temperature difference measured between the temperature sensor 17b at the outlet and the temperature sensor 17c at the middle of the indoor heat exchanger 14.
The degree of superheat is a temperature difference at the time of cooling, and the degree of subcooling is a temperature difference at the time of heating.
A method for controlling a flow rate of refrigerant with reference to the degree of superheat or subcooling in the air conditioning system will be described.
FIG 3 illustrates a flow chart showing the steps of a method for controlling an air conditioning system in accordance with a preferred embodiment of the present invention.
Referring to FIG 3, the method for controlling an air conditioning system includes the steps of setting an ideal degree of subcooling and an ideal degree of superheat at a controller (S1), measuring the degree of subcooling or superheat of the refrigerant flowing in an indoor heat exchanger (S2), comparing the degree of subcooling or superheat set thus to the degree of subcooling or superheat measured (S3), and controlling a flow rate of the refrigerant flowing in the indoor heat exchanger according to a result in the step S3 in which the degree of subcooling or superheat set thus is compared to the degree of subcooling or superheat measured.
As described, the degree of superheat or the degree of subcooling is a difference between a temperature of the refrigerant at the outlet of the indoor heat exchanger 14, and a temperature of the refrigerant at a saturation state of the refrigerant flowing in the indoor heat exchanger 14.
Moreover, as described, the temperatures of the refrigerant are measured with a plurality of temperature sensors 17a, 17b, and 17c mounted on the indoor heat exchanger 14.
At first, a setting step (S1) is performed, in which an ideal degree of superheat and an ideal degree of subcooling at the time of operation of the indoor heat exchanger are set at the controller. The ideal degree of superheat and the ideal degree of subcooling vary with a pressure of the refrigerant and an environmental temperature.
Then, a measuring step (S2) is performed, in which an actual degree of superheat or an actual degree of subcooling of the refrigerant flowing in the indoor heat exchanger 14 is measured. In the measuring step (S2), the temperatures of the refrigerant are measured with the temperature sensors 17a, 17b, and 17c mounted on the indoor heat exchanger 14.
That is, since the degree of superheat or the degree of subcooling is a difference of a temperature of the refrigerant at the outlet of the indoor heat exchanger 14 and a saturation temperature of the refrigerant flowing in the indoor heat exchanger, the controller can calculate the degree of superheat or the degree of subcooling with the temperatures measured at the temperature sensors 17a, 17b, and 17c.
Then, a determination step (S3) is performed, in which a measured degree of superheat or subcooling is compared to a preset degree of superheat or subcooling. In the determination step (S3), it is determined whether the measured degree of superheat or subcooling converges to the preset degree of superheat or subcooling, or not; or if not, which one has how much difference.
Then, an adjusting step (S4) is performed, in which a flow rate of the refrigerant flowing in the indoor heat exchanger 14 is adjusted according to a result of determination in the determination step (S3).
In the adjusting step (S4), the flow rate of the refrigerant is adjusted by controlling the flow rate control valve 13a, and 13b at opposite ends of the indoor heat exchange part 10.
In more detail, if the degree of superheat measured is higher than the preset degree of superheat at the time of room cooling, opening of the flow rate control valves 13a, and 13b are adjusted, to increase a flow rate of the refrigerant flowing in the indoor heat exchanger 14 (S4a), and if the degree of superheat measured is lower than the preset degree of superheat at the time of room cooling, opening of the flow rate control valves 13a, and 13b are adjusted, to decrease a flow rate of the refrigerant flowing in the indoor heat exchanger 14 (S4c).
If the degree of superheat measured is the same with the preset degree of superheat at the time of room cooling, the flow rate of the refrigerant flowing in the indoor heat exchanger 14 is maintained (S4b).
In the meantime, if the degree of subcooling measured is higher than the preset degree of subcooling at the time of room heating, opening of the flow rate control valves 13a, and 13b are adjusted, to increase a flow rate of the refrigerant flowing in the indoor heat exchanger 14 (S4a), and if the degree of subcooling measured is lower than the preset degree of subcooling at the time of room cooling, opening of the flow rate control valves 13a, and 13b are adjusted, to decrease a flow rate of the refrigerant flowing in the indoor heat exchanger 14 (S4c).
If the degree of superheat measured is the same with the preset degree of superheat at the time of room cooling, the flow rate of the refrigerant flowing in the indoor heat exchanger 14 is maintained (S4b).
The operation of the air conditioning system will be described.
FIGS. 4 and 5 illustrate graphs showing variations of a pressure 'P' and enthalpy 'h' of refrigerant at the outdoor heat exchange part 20 and the indoor heat exchange part 10 at the time of room cooling and room heating of the air conditioning system, respectively.
The air conditioning system cools or heats the room depending on an operation.
At the time of cooling or heating, the hybrid heat exchange part 30 exchanges heat between the outdoor heat exchange part 20 and the indoor heat exchange part 10.
The cooling operation will be described with reference to FIGS. 1 and 2.
The refrigerant in the outdoor heat exchange part 20 is compressed at the compressor 22, and forwarded to the flow controller 23 (A-B section). The flow controller 23 changes over the refrigerant to a side of the fourth heat exchanger 24. In this instance, the refrigerant introduced to the fourth heat exchanger 24 is condensed as the refrigerant heat exchanges with outdoor air (B-C section). The condensed refrigerant changes to a refrigerant of a low temperature and low pressure as the refrigerant passes through the expansion device 28 (C-D section). After cooling down the third heat exchanger 26 of the hybrid heat exchange part 30, the low temperature and low pressure refrigerant is introduced into the compressor 22 through the flow controller 23 (D-A section). In the outdoor heat exchange part 20, the compressor 22 serves as a driving source if the refrigerant flow.
Then, the refrigerant in the indoor heat exchange part 10 is cooled down as the second heat exchanger 16 and the third heat exchanger 26 in the hybrid heat exchange part 30 exchange heat (e-a section). The refrigerant cooled down thus is pumped to a side of the first heat exchanger by the pump 12 (a-b section). In this instance, the refrigerant is neither in a two phase state, nor at a saturated temperature. The pumped refrigerant is introduced to the first heat exchanger 14 through the flow rate control valves 13a, and 13b at an inlet of the first heat exchanger 14, and discharged from the first heat exchanger 14 after heat exchanger with room air (b-c-d section).
The refrigerant in the indoor heat exchange part 10 reaches to a saturation temperature at which the refrigerant is involved no temperature change, but a phase change as the refrigerant heat exchanges with room air (c point). In this step, the temperature sensor 17c between opposite ends of the first heat exchanger 14 measures a saturation temperature of the refrigerant, and the temperature sensor 17b at the outlet of the first heat exchanger 14 (corresponding to 'd' point) measures a superheated temperature of the refrigerant.
According to this, the controller determines a difference between the saturation temperature and the superheated temperature, to derive the degree of superheat, compares the derived degree of superheat to the preset degree of superheat of the refrigerant, and adjusts opening of the flow rate control valves 13a, and 13b.
That is, if it is determined that the measured degree of superheat is higher than the preset degree of superheat, opening of the flow rate control valves 13a, and 13b on the first heat exchanger 14 is made greater, to increase a flow rate of the refrigerant.
Opposite to this, if it is determined that the measured degree of superheat is lower than the preset degree of superheat, opening of the flow rate control valves 13a, and 13b on the first heat exchanger 14 is made smaller, to decrease a flow rate of the refrigerant.
In this instance, of the flow rate control valves 13a, and 13b on opposite ends of the first heat exchanger 14, though it is preferable that opening of the flow rate control valve 13a at an inlet end of the first heat exchanger 14 is made greater or smaller, and opening of the flow rate control valve 13b at an outlet end of the first heat exchanger 14 is opened to the maximum, the way of opening of the flow rate control valves 13a, and 13b is not limited to this one.
According to this, the flow rate of the refrigerant to the first heat exchanger 14 can be controlled to the optimum.
After making heat exchange at the first heat exchanger 14, the refrigerant is discharged from the first heat exchanger 14 to the second heat exchanger 16 of the hybrid heat exchange part 30, and cooled therein again, to circulate therefrom.
Next, heating operation will be described with reference to FIGS. 1, 2, and 5.
After compressed at the compressor 22 in the outdoor heat exchange part 20, the refrigerant is forwarded to the flow controller 23 (A-B). The flow controller 23 changes over the refrigerant to a side of the third heat exchanger 26 of the hybrid heat exchange part 30. In this instance, the refrigerant introduced into the hybrid heat exchange part 30 discharges heat, and condensed at the third heat exchanger 26 (B-C). The condensed refrigerant is changed to refrigerant of a low pressure and a low temperature as the refrigerant passes through the expansion device 28 (C-D), introduced into the fourth heat exchanger 24, heat exchanges with outdoor air, and is introduced into the compressor through the flow controller 23 (D-A). A circulation direction of the refrigerant in the outdoor heat exchange part 20 is opposite to the cooling operation.
Then, the refrigerant at the indoor heat exchange part 10 has a pressure boosted by pumping of the pump 12 (a-b). The pumped refrigerant is heated as the refrigerant heat exchanges at the second heat exchanger 16 of the hybrid heat exchange part 30 with the third heat exchanger 26 of the outdoor heat exchange part 20 (b-c).
The refrigerant heated thus is forwarded to a side of the first heat exchanger 14 by the pump 12. The refrigerant introduced into the first heat exchanger 14 heat exchanges with room air to heat the room, while the refrigerant itself is condensed (c-a).
In this instance, as the refrigerant in the first heat exchanger 14 heat exchanges with the room air, the refrigerant reaches to a saturation temperature at which the refrigerant is involved in no temperature change, but a phase change (d-e). In such a step, the temperature sensor 17c between the refrigerant inlet/outlet of the first heat exchanger 14 measures the saturation temperature of the refrigerant ('e' point), and the temperature sensor 17b at the outlet of the first heat exchanger 14 measures a superheated temperature of the refrigerant ('a' point).
According to this, the controller derives the degree of superheat as a difference between the saturation temperature and the superheated temperature, compares the derived degree of superheat to the preset degree of superheat of the refrigerant, and adjusts opening of the flow rate control valves 13a, and 13b.
That is, if it is determined that the measured degree of superheat is higher than the preset degree of superheat, opening of the flow rate control valves 13a on the refrigerant inlet of the first heat exchanger 14 is made greater, to increase the flow rate of the refrigerant to the first heat exchanger 14.
Opposite to this, if it is determined that the measured degree of superheat is lower than the preset degree of superheat, opening of the flow rate control valves 13a is made smaller, to decrease a flow rate of the refrigerant. According to this, the flow rate to the first heat exchanger 14 is adjusted.
The refrigerant having room air heat exchanged therewith at the first heat exchanger 14 makes circulation in which the refrigerant is introduced into, and heated again at the second heat exchanger 16 of the hybrid heat exchange part 30.
As has been described, the air conditioning system and the method for controlling the same of the present invention have the following advantages.
The supply of refrigerant to the indoor heat exchange part by using a pump as a driving source that requires no oil permits to dispense with an oil recovery operation at the indoor heat exchange part.
According to this, the air conditioning system can be installed on a multistory building without limitation of a height of the building as far as a capacity of the pump permits. Moreover, even if a refrigerant pipe is long, the air conditioning system is applicable even to a system with a refrigerant pipe line longer than the related art as far as the capacity of the pump permits.
Moreover, the compressor and the expansion device of the outdoor heat exchange part may be placed outside of a room mounted on the outdoor unit. Therefore, even if the compressor and the expansion device generate noise, the noise can not reach to the user.
Furthermore, since the outdoor heat exchange part is connected to the indoor heat exchange part through the hybrid heat exchange part, a length of the refrigerant pipeline of the outdoor heat exchange part can be shortened significantly regardless of a height of the building. According to this, a refrigerant recovery ratio can be improved significantly, to prevent the compressor suffering from damage caused by a poor refrigerant recovery ratio.
Since the saturation temperature of the refrigerant can be measured at the first heat exchanger in the indoor heat exchange part, control of the refrigerant flow rate to the first heat exchanger can be optimized.
The optimum control of the refrigerant flow rate from the first heat exchanger permits fine control of the room temperature.
The no provision of the compressor and the expansion device to the indoor heat exchange part to be installed in a room permits simple structure of the indoor heat exchange part, which enables to reduce price of the indoor unit.
It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope of the inventions. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.

Claims

An air conditioning system comprising:
an outdoor heat exchange part including a compressor for compressing refrigerant, an outdoor heat exchanger for making the refrigerant to heat exchange with outdoor air, and an expansion device for expanding the refrigerant;

an indoor heat exchange part including a pump for making refrigerant in a flow path independent from the outdoor heat exchange part to flow, a indoor heat exchanger for making the refrigerant heat exchange with room air, and a flow rate control device for controlling a flow rate of the refrigerant; and

a hybrid heat exchange part for making the outdoor heat exchange part and the indoor heat exchange part, which are independent from each other, to heat exchange with each other.
The system as claimed in claim 1, wherein the flow rate control device includes;
a temperature sensor for measuring temperatures of refrigerant flowing in the indoor heat exchanger,
a controller for determining a degree of superheat or subcooling of the refrigerant with the temperatures measured at the temperature sensor, and
a flow rate control valve for controlling a refrigerant flow rate to the indoor heat exchanger according to the determination of the controller.
The system as claimed in claim 2, wherein the flow rate control valve is mounted on a refrigerant inlet end of the indoor heat exchanger.
The system as claimed in claim 2, wherein the flow rate control valve is mounted on a refrigerant outlet end of the indoor heat exchanger.
The system as claimed in claim 2, wherein the temperature sensors are mounted on the refrigerant inlet end, the refrigerant outlet end, and a predetermined portion between the refrigerant inlet end and the refrigerant outlet end of the indoor heat exchanger.
The system as claimed in claim 5, wherein the predetermined portion between the refrigerant inlet end and the refrigerant outlet end of the indoor heat exchanger is a section in which the refrigerant flowing in the indoor heat exchanger is in a saturated state.
A method for controlling an air conditioning system comprising the steps of:
setting an ideal degree of superheat, and an ideal degree of subcooling at a controller;

comparing the degree of superheat or subcooling set thus with a degree of superheat or subcooling measured thus; and

controlling a flow rate of refrigerant flowing in an indoor heat exchanger according to a result of the step of comparing the degree of superheat or subcooling set thus with a degree of superheat or subcooling measured thus.
The method as claimed in claim 7, wherein the degree of superheat or subcooling is a difference between a temperature of the refrigerant at the refrigerant outlet of the indoor heat exchanger and a saturation temperature of the refrigerant flowing in the indoor heat exchanger.
The method as claimed in claim 7, wherein the step of controlling a flow rate of refrigerant flowing in an indoor heat exchanger includes the steps of;
increasing the flow rate of the refrigerant flowing in the indoor heat exchanger if the degree of superheat measured is higher than the degree of superheat set, and
decreasing the flow rate of the refrigerant flowing in the indoor heat exchanger if the degree of superheat measured is lower than the degree of superheat set.
The method as claimed in claim 7, wherein the step of controlling a flow rate of refrigerant flowing in an indoor heat exchanger includes the steps of;
increasing the flow rate of the refrigerant flowing in the indoor heat exchanger if the degree of subcooling measured is higher than the degree of subcooling set, and
decreasing the flow rate of the refrigerant flowing in the indoor heat exchanger if the degree of subcooling measured is lower than the degree of subcooling set.