AIR-CONDITIONING METHOD AND AIR-CONDITIONING SYSTEM

Abstract

An air-conditioning method comprises the steps of performing a refrigerator operation using a refrigerator to which cooling water cooled in a plurality of cooling towers is supplied as a cold heat source, and performing a free cooling operation using at least some of the plurality of cooling towers as a cold heat source, wherein at a time of the free cooling operation, the number of the cooling towers which are operated is controlled.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an air-conditioning method and an air-conditioning system, and particularly relates to an air-conditioning method and an air-conditioning system for a clean room, building air-conditioning and the like.

2. Description of the Related Art

A cooling operation is performed throughout a year in a clean room and a building facility. Therefore, in the air-conditioning systems of these facilities, energy saving is an important object. Thus, free cooling has been carried out in recent years (see Japanese Patent Application Laid-Open No. 2004-132651).

Free cooling refers to a system that carries out a free cooling operation using a cooling tower as a cold heat source without using a refrigerator in winter while carrying out a refrigerator operation using the refrigerator as a cold heat source in summer. According to the system, cooling can be performed without operating the refrigerator in winter, and therefore, a large energy saving effect can be expected.

Incidentally, such cooling systems include the case where one cooling tower is shared by both a refrigerator operation and a free cooling operation, and the case where their own dedicated cooling towers are used in the respective operations.

SUMMARY OF THE INVENTION

However, in both cases, waste of the energy consumption amount in the cooling towers occurs. For example, in the case of sharing one cooling tower, the necessary amounts of cooling water (namely, cold heat amounts) differ in the refrigerator operation and free cooling operation. Therefore, the cooling tower is operated in correspondence with any one of the operations, and this becomes waste energy consumption in the other operation.

Further, when dedicated cooling towers are used in the refrigerator operation and free cooling operation respectively, there arises the problem of reducing the energy efficiency at the time of restart of operations.

The present invention is made in view of the above circumstances, and has an object to provide an air-conditioning method and an air-conditioning system capable of optimizing the energy consumption of a cooling tower.

In order to attain the above-described object, the first aspect of the invention is an air-conditioning method for performing a refrigerator operation using a refrigerator to which cooling water cooled in a plurality of cooling towers is supplied as a cold heat source, and a free cooling operation using at least some of the plurality of cooling towers as a cold heat source, and is characterized in that at a time of the free cooling operation, the number of the cooling towers which are operated is controlled.

According to the present invention, by controlling the number of cooling towers which are operated at the time of a free cooling operation, an optimal amount of cold heat can be generated in each of the operation modes, and the energy consumption amount as a whole can be reduced.

In the first aspect of the invention, the second aspect of the invention is characterized in that an intermediate operation using at least some of the plurality of cooling towers as a cold heat source in combination with the refrigerator, and at a time of the intermediate operation, the number of the cooling towers which are operated to be the cold heat source is controlled. Use of the cooling towers and the refrigerator in combination means the use of the cooling towers and the refrigerator by connecting the cooling towers and the refrigerator in series, and refers to, for example, the case in which the cooling water cooled in the cooling tower is further cooled in the refrigerator, and supplied to the air-conditioning load part.

According to the present invention, the number of cooling towers which are operated is also controlled at the time of the intermediate operation, and therefore, a suitable amount of cold heat can be generated. Thereby, the energy consumption amount as a whole can be reduced.

In the first or second aspect of the invention, the third aspect of the invention is characterized in that switching of the operation is performed in accordance with an outside air temperature and an air-conditioning load condition. According to the present invention, in accordance with the outside air temperature and the air-conditioning load condition, the cold heat amount (temperature and flow rate of the cooling water) with which the energy consumption becomes the minimum can be obtained by simulation or the like. Accordingly, by controlling the number of cooling towers which are operated in accordance with the result, the air-conditioning operation in which the energy consumption amount becomes minimum can be performed.

In any one of the first to the third aspects of the invention, the fourth aspect of the invention is characterized in that a plurality of the refrigerators are provided, and the number of the cooling towers which are operated is controlled for each of the plurality of refrigerators. According to the present invention, the number of cooling towers which are operated is controlled for each of the refrigerators. Therefore, for example, when the required cold heat amount differs in each refrigerator, the minimum required amount of cold heat can be supplied to each of the refrigerators, and the energy consumption amount as a whole can be reduced.

In any one of the first to fourth aspects of the invention, the fifth aspect of the invention is characterized in that the refrigerator is a turbo refrigerator, and inverter control is performed for the refrigerator. According to the present invention, the energy consumption of the refrigerator can be decreased.

In any one of the first to the fifth aspects of the invention, the sixth aspect of the invention is characterized in that by controlling a rotational speed of a pump which circulates the cooling water cooled in the plurality of cooling towers or the refrigerator, a flow rate of the cooling water is controlled. According to the present invention, the energy consumption amount required for circulation of the cooling water can be reduced.

In order to attain the above described object, the seventh aspect of the invention provides an air-conditioning system, characterized by including a plurality of cooling towers that cool cooling water, a refrigerator having a condenser and an evaporator, a circulation line for a refrigerator operation that circulates the cooling water cooled in the cooling tower into the condenser, and circulates the cooling water cooled in the evaporator into an air-conditioning load part, a circulation line for a free cooling operation that circulates the cooling water cooled in the cooling tower into the air-conditioning load part, a line switching device that switches the circulation line for the refrigerator operation and the circulation line for the free cooling operation, and regulates the number of cooling towers to be connected to the circulation line for the free cooling operation, and a control device that controls the line switching device and individually controls operation and stoppage of the plurality of cooling towers.

According to the present invention, the number of cooling towers which are operated at the time of the free cooling operation can be controlled. Accordingly, cold heat in the amount suitable for each operation mode can be generated, and the energy consumption amount in the entire system can be reduced.

In the seventh aspect of the invention, the eighth aspect of the invention is characterized by further including a circulation line for an intermediate operation that connects the plurality of cooling towers in series to the evaporator of the refrigerator, and characterized in that the line switching device switches the lines including the circulation line for the intermediate operation, and changes the number of cooling towers to be connected to the circulation line for the intermediate operation.

According to the present invention, by connecting the cooling towers and the evaporator of the refrigerator in series, the intermediate operation using the cooling towers and the refrigerator in combination as a cold heat source can be performed. Further, according to the present invention, the number of cooling towers which are operated at the time of the intermediate operation can be controlled. Therefore, the cold heat amount (the temperature and the flow rate of the cooling water) can be regulated to the one suitable for the intermediate operation, and the energy consumption amount of the entire system can be reduced. The circulation line for the intermediate operation can be also used as the free cooling circulation line. In this case, by stopping the refrigerator, the circulation line for the intermediate operation can be also used as the circulation line for the free cooling operation.

In the seventh or eighth aspect, the ninth aspect of the invention is characterized in that a plurality of the refrigerators are provided, and the number of the cooling towers which are connected to each of the refrigerators is changed by the line switching device.

According to the present invention, the number of cooling towers which are operated can be controlled for each of a plurality of refrigerators. Accordingly, even when the required cold heat amounts differ among a plurality of refrigerators, the cold heat amount suitable for each of them can be generated. Thereby, the energy consumption amount in the entire system can be reduced.

According to the present invention, by controlling the number of cooling towers which are operated, the optimal amount of cold heat can be generated in each of the operation modes, and the energy consumption in the entire system can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a system diagram schematically showing the configuration of an air-conditioning system of a first embodiment;

FIGS. 2A and 2B are diagrams each schematically showing a conduit configuration for each operation mode;

FIG. 3 is a system diagram showing an air-conditioning system having a piping configuration differing from FIG. 1;

FIG. 4 is a system diagram showing a modified example of the air-conditioning system of FIG. 1;

FIG. 5 is a system diagram schematically showing the configuration of an air-conditioning system of a second embodiment;

FIGS. 6A to 6C are diagrams each schematically showing a conduit configuration for each operation mode;

FIG. 7 is a system diagram schematically showing the configuration of an air-conditioning system of a third embodiment;

FIGS. 8A and 8B are diagrams each schematically showing a conduit configuration for each operation mode;

FIG. 9 is a diagram schematically showing a conduit configuration for each operation mode; and

FIG. 10 is a system diagram showing a modified example of the air-conditioning system of FIG. 7.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of an air-conditioning method and an air-conditioning system according to the present invention will be described in detail in accordance with the attached drawings.

First Embodiment

FIG. 1 is a system diagram schematically showing the configuration of an air-conditioning system of a first embodiment. An air-conditioning system 10 shown in the drawing is a system for carrying out air-conditioning of a clean room facility 12.

In the clean room facility 12, a fan filter unit 16 (hereinafter, FFU) is provided on a ceiling surface of a clean chamber 14, and by the FFU 16, air in a ceiling space 18 is purified and is caused to flow down to the clean chamber 14. The floor surface of the clean chamber 14 is a grating floor, the air in the clean chamber 14 is sucked into an underfloor space 20, and further returned to the ceiling space 18 through a return chamber 22. Thereby, the air in the ceiling space 18 is sent to the clean chamber 14 again by the FFU 16, and the clean chamber 14 is kept at high cleanliness.

A sensible heat treatment coil 24Y is provided in the return chamber 22, so as to cool the air flowing in the return chamber 22 to be able to treat sensible heat. Further, in the clean chamber 14, an apparatus 26 such as a semiconductor manufacturing apparatus is provided, and a coil 28 is provided in the apparatus 26 so that a refrigerant is circulated between the coil 28 and an apparatus load heat exchanger 24X. Further, an external conditioner 30 is provided at the clean room facility 12. The external conditioner 30 includes an external conditioner coil 24Z, a humidifier 32, a heater 34, a fan 36, a filter (not illustrated) and the like, and by driving the fan 36, outside air is taken in. Subsequently, the air is subjected to dusting by a filter (not illustrated), is cooled by the external conditioner coil 24Z, is humidified by the humidifier 32, is heated by the heater 34 in accordance with necessity, and thereafter, is supplied into the facility.

The air-conditioning system 10 of the present embodiment is a system which supplies cold heat to the apparatus load heat exchanger 24X, the sensible heat treatment coil 24Y and the external conditioner coil 24Z, to meet a cooling load. The apparatus load heat exchanger 24X, the sensible heat treatment coil 24Y and the external conditioner coil 24Z differ in the temperature of the cold water which is required. For example, the temperatures of the cold water are set at 17° C. for the apparatus load heat exchanger 24X, at 12° C. for the sensible heat treatment coil 24Y, and at 7° C. for the external conditioner coil 24Z. Hereinafter, the apparatus load heat exchanger 24X, the sensible heat treatment coil 24Y and the external conditioner coil 24Z will be also called the load part 24X, the load part 24Y and the load part 24Z.

The air-conditioning system 10 is mainly configured by eight cooling towers 42A to 42H and three refrigerators 44X, 44Y and 44Z. The numbers of cooling towers and refrigerators are not limited to the example of the present embodiment, but, for example, seven cooling towers or less or nine cooling towers or more may be adopted, and two refrigerators or less or four refrigerators or more may be adopted.

The internal construction of each of the cooling towers 42A to 42H is omitted, but each of them includes a fan for forming an ascending current of outside air in the tower, a water sprinkling pipe for sprinkling cooling water into the tower, and a water collecting unit for collecting sprinkled cooling water. According to the cooling towers 42A to 42H, the cooling water is sprinkled and contacts outside air, whereby the cooling water is deprived of heat of vaporization and is cooled. The present embodiment is described with the example of a closed type cooling tower, but an open type cooling tower may be used by adding a heat exchanger.

Meanwhile, three refrigerators 44X, 44Y and 44Z are devices for generating cooling water at temperatures necessary for the load parts 24X, 24Y and 24Z respectively. Condensers 46X, 46Y and 46Z, and evaporators 48X, 48Y and 48Z are provided inside the refrigerators 44X, 44Y and 44Z. The condensers 46X, 46Y and 46Z and the evaporators 48X, 48Y and 48Z are connected by a circulation passage (not illustrated), and a refrigerant is circulated. The refrigerant is circulated in the condensers 46X, 46Y and 46Z and the evaporators 48X, 48Y and 48Z, whereby the cooling water is cooled in the evaporators 48X, 48Y and 48Z. The constructions of the refrigerators 44X, 44Y and 44Z are not especially limited, and various constructions such as a turbo type and an absorption type can be adopted, but the present embodiment is described with the example of a turbo type refrigerator.

The evaporators 48X, 48Y and 48Z of the refrigerators 44X, 44Y and 44Z are connected to the load parts 24X, 24Y and 24Z. More specifically, the evaporator 48X is connected to the load part 24X through pipings x3 and x4, and a pump 50X is placed in the piping x3. By driving the pump 50X, cooling water is circulated between the evaporator 48X and the load part 24X. Likewise, the evaporator 48Y is connected to the load part 24Y through pipings y3 and y4, and a pump 50Y is placed in the piping y3.

By driving the pump 50Y, the cooling water is circulated between the evaporator 48Y and the load part 24Y. Further, the evaporator 48Z is connected to the load part 24Z through pipings z3 and z4, and a pump 50Z is placed in the piping z3. By driving the pump 50Z, the cooling water is circulated between the evaporator 48Z and the load part 24Z. Thus, the refrigerators 44X, 44Y and 44Z, and the load parts 24X, 24Y and 24Z are connected one to one.

Each of the condensers 46X, 46Y and 46Z of the refrigerators 44X, 44Y and 44Z is respectively connected to the cooling towers 42A to 42H. The cooling towers 42A to 42H are connected to the condensers 46X, 46Y and 46Z in parallel. That is to say, pipings a1 to h1 for discharging cooling water are connected to the cooling towers 42A to 42H, and the pipings a1 to h1 are connected to a main piping j1. The main piping j1 branches into the pipings x1, y1 and z1, and thereafter, are connected to the condensers 46X, 46Y and 46Z. Pipings x2, y2 and z2 for discharging cooling water are connected to the condensers 46X, 46Y and 46Z, and the pipings x2, y2 and z2 are connected to a main piping j2. The main piping j2 is branched into pipings a2 to h2, and are connected to the water sprinkling pipes (not illustrated) of the respective cooling towers 42A to 42H. Thereby, the cooling water which is cooled in the respective cooling towers 42A to 42H can be circulated and supplied to the condensers 46X, 46Y and 46Z, and the cooling towers 42A to 42H can be used as the cooling devices of the refrigerators 42X to 42Z.

Pumps 52x, 52y and 52z are placed in the pipings x1, y1 and z1 respectively, and drive control is individually performed for the pumps 52x, 52y and 52z, whereby the cooling water is individually circulated into the respective condensers 46X, 46Y and 46Z, and the circulation amount can be regulated.

Further, three-way valves 54X, 54Y and 54Z are placed in the pipings x2, y2 and z2, and by operating the three-way valves 54X, 54Y and 54Z, part of the cooling water which flows in the pipings x2, y2 and z2 flows into the pipings x1, y1 and z1 through bypass pipes 56X, 56Y and 56Z, so that the flow rate regulation is performed.

Incidentally, the cooling towers 42A to 42H are connected in series to the evaporators 48X, 48Y and 48Z of the refrigerators 44X, 44Y and 44Z.

More specifically, the piping x3 is connected to the main piping j2 through the piping x6 and is connected to the main piping j1 through the piping x5. Accordingly, the cooling water which flows in the piping x3 flows into at least one of the cooling towers 42A to 42H through the piping x6 and the main piping j2, and returns to the original piping x3 through the main piping j1 and the piping x5. Thereby, the cooling towers 42A to 42H are connected in series to the evaporator 48X of the refrigerator 44X. A pump 58X is provided in the piping x6, and by driving the pump 58X, the cooling water of the piping x3 flows into the piping x6. On-off valves 60X and 62X are provided at the downstream side directly from the connecting portions in the piping x3 and the piping x6. An on-off valve 63X is provided in the piping x5. By performing opening and closing operation of the on-off valves 60X, 62X and 63X, it can be selected whether or not to feed the cooling water in the piping x3 to the cooling towers 42A to 42H. Further, a three-way valve 64X is placed in the piping x6, and by operating the three-way valve 64X, part of the cooling water flowing in the piping x6 flows into the piping x5 through a bypass pipe 66X, so that flow rate regulation is performed.

Likewise, the piping y3 is connected to the main piping j2 through the piping y6, and is connected to the main piping j1 through the piping y5. Accordingly, the cooling water flowing in the piping y3 flows into at least one of the cooling towers 42A to 42H through the piping y6 and the main piping j2, and returns to the original piping y3 through the main piping j1 and the piping y5. Thereby, the cooling towers 42A to 42H are connected in series to the evaporator 48Y of the refrigerator 44Y. A pump 58Y is provided in the piping y6, and by driving the pump 58Y, the cooling water in the piping y3 flows into the piping y6. In the piping y3 and piping y6, on-off valves 60Y and 62Y are provided at the immediate downstream side from the connecting portions, and an on-off valve 63Y is provided in the piping y5. By performing an opening and closing operation of these on-off valves 60Y, 62Y and 63Y, it can be selected whether or not to feed the cooling water flowing in the piping y3 into the cooling towers 42A to 42H. Further, a three-way valve 64Y is placed in the piping y6, and by operating the three-way valve 64Y, part of the cooling water flowing in the piping y6 flows into the piping y5 through a bypass pipe 66Y, so that the flow rate regulation is performed.

Further, the piping z3 is connected to the main piping j2 through the piping z6, and is connected to the main piping j1 through the piping z5. Accordingly, the cooling water flowing in the piping z3 flows into at least one of the cooling towers 42A to 42H through the piping z6 and the main piping j2, and returns to the original piping z3 through the main piping j1 and the piping z5. Thereby, the cooling towers 42A to 42H are connected in series to the evaporator 48Z of the refrigerator 44Z. A pump 58Z is provided in the piping z6, and by driving the pump 58Z, the cooling water in the piping z3 flows into the piping z6. In the piping z3 and piping z6, on-off valves 60Z and 62Z are provided at the downstream side directly from the connecting portions, and an on-off valve 63Z is provided in the piping z5. By performing an opening and closing operation of these on-off valves 60Z, 62Z and 63Z, it can be selected whether or not to feed the cooling water flowing in the piping z3 into the cooling towers 42A to 42H. Further, a three-way valve 64Z is placed in the piping z6, and by operating the three-way valve 64Z, part of the cooling water flowing in the piping z6 flows into the piping z5 through a bypass pipe 66Z, so that flow rate regulation is performed.

As such, in the present embodiment, the cooling towers 42A to 42H can be connected in series to the evaporators 48X, 48Y and 48Z of the refrigerators 44X, 44Y and 44Z. Thereby, the cooling towers 42A to 42H and the refrigerators 44X, 44Y and 44Z can be used at the same time, and the intermediate operation using the cooling towers and the refrigerators in combination as the cold heat source can be performed. Specifically, the cooling water preliminarily cooled in any of the cooling towers 42A to 42H is supplied to the refrigerators 44X, 44Y and 44Z to be able to cool the refrigerators. Thereby, energy consumption of the refrigerators 44X, 44Y and 44Z can be decreased.

Further, according to the present embodiment, by stopping circulation of the refrigerant in the refrigerators 44X, 44Y and 44Z in the state in which the cooling towers 42A to 42H are connected in series to the evaporators 48X, 48Y and 48Z of the refrigerators 44X, 44Y and 44Z, a free cooling operation with only the cooling towers 42A to 42H as the cold heat source can be performed.

Incidentally, a plurality of on-off valves 68 for selecting the cooling towers 42A to 42H are placed in the aforementioned main pipings j1 and j2. The on-off valves 68 are placed between the connecting portions where the pipings a1 to h1 are connected on the main piping j1, or placed between the connecting portions where the pipings a2 to h2 are connected on the main piping j2. By opening or closing any of the on-off valves 68, the cooling towers 42A to 42H in which the cooling water circulates can be selected. An opening and closing operation of the on-off valve 68 is performed by a control device 70.

The control device 70 is connected to a sensor 72 which measures the wet-bulb temperature of outside air, and receives the measurement data of the outside air temperature from the sensor 72. Further, the control device 70 is connected to the respective load parts 24X, 24Y and 24Z, and receives the data of the load conditions from the respective load parts 24X, 24Y and 24Z. Further, the control device 70 is connected to a drive device (not illustrated) of fans or the like of the cooling towers 42A to 42H, so as to be able to control operation and stoppage of the cooling towers 42A to 42H individually. The control device 70 obtains the flow rate of the cooling water to be the minimum required flow rate by simulation from the outside air temperature and the data of the load conditions, and determines the cooling towers to be operated among the cooling towers 42A to 42H so as to be able to supply the cooling water corresponding to the flow rate. The control device 70 operates the cooling towers among the cooling towers 42A to 42H, and circulates the cooling water into the cooling towers among the cooling towers 42A to 42H by controlling the on-off valve 68. Further, for the cooling towers into which the cooling water does not have to be fed among the cooling towers 42A to 42H, those cooling towers among the cooling towers 42A to 42H are stopped.

Next, an operation method of the air-conditioning system 10 which is configured as described above will be described.

In summer when outside air temperature is high, a refrigerator operation using the refrigerators 44X, 44Y and 44Z as the cold heat source is performed. In the refrigerator operation, the on-off valves 60X, 60Y and 60Z are opened, and the on-off valves 62X, 62Y, 62Z, 63X, 63Y and 63Z are closed. Thereby, a conduit construction as shown in FIG. 2A is formed. As shown in FIG. 2A, the cooling towers 42A to 42H are connected to the condensers 46X, 46Y and 46Z of the refrigerators 44X, 44Y and 44Z, and the cooling water cooled in the cooling towers 42A to 42H is circulated and supplied to the condensers 46X, 46Y and 46Z. Further, the evaporators 48X, 48Y and 48Z of the refrigerators 44X, 44Y and 44Z and the load parts 24X, 24Y and 24Z are connected, and the cooling water cooled in the evaporators 48X, 48Y and 48Z is supplied to the load parts 24X, 24Y and 24Z. Thereby, the refrigerators 44X, 44Y and 44Z are used as the cold heat source, and cold heat can be supplied to the load parts 24X, 24Y and 24Z. In the refrigerator operation, all the cooling towers 42A to 42H are used, but by performing an opening and closing operation of any of the on-off valves 68 (see FIG. 1), the number of the cooling towers 42A to 42H to be used may be controlled. For example, by closing the on-off valves 68 disposed in the main pipings j1 and j2 between the cooling tower 42F and the cooling tower 42G, the cooling towers 42A to 42F can be used, and the number of cooling towers which are operated can be decreased to six from eight.

Next, an intermediate operation which is performed at an outside air temperature between summer and winter will be described. The intermediate operation is the one using the refrigerators 44X, 44Y and 44Z and some of the cooling towers 42A to 42H as a cold heat source. The on-off valves 62X, 62Y, 62Z, 63X, 63Y and 63Z are opened and the on-off valves 60X, 60Y and 60Z are closed. Thereby, some of the cooling towers 42A to 42H and the evaporators 48X, 48Y and 48Z are connected in series. Therefore, the cooling water is preliminarily cooled in some of the cooling towers 42A to 42H first, and thereafter, is cooled in the evaporators 48X, 48Y and 48Z, and is supplied to the load parts 24X, 24Y and 24Z. Accordingly, some of the cooling towers 42A to 42H and the refrigerators 44X, 44Y and 44Z can be used in combination as the cold heat source. In the intermediate operation, remaining cooling towers among the cooling towers 42A to 42H, and the condensers 46X, 46Y and 46Z of the refrigerators 44X, 44Y and 44Z are connected, whereby the cooling water which is cooled in the remaining cooling towers among the cooling towers 42A to 42H is circulated and supplied to the condensers 46X, 46Y and 46Z, and is used for cooling of the refrigerators 44X, 44Y and 44Z.

On the occasion of the intermediate operation, the number of cooling towers 42A to 42H which are used can be controlled by opening and closing any of the on-off valves 68 (see FIG. 1). As one example of it, FIG. 2B shows the example in which the on-off valves 68 on the main pipings j1 and j2 are closed between the cooling tower 42F and the cooling tower 42G, between the cooling tower 42D and the cooling tower 42E, and between the cooling tower 42C and the cooling tower 42D. In this example, the two cooling towers 42G and 42H are connected in series to the evaporator 48X of the refrigerator 44X, the two cooling towers 42E and 42F are connected in series to the evaporator 48Y of the refrigerator 44Y, and the one cooling tower 42D is connected in series to the evaporator 48Z of the refrigerator 44Z. Accordingly, the number of the cooling towers for preliminary cooling can be controlled to two, two and one. Meanwhile, the three cooling towers 42A to 42C are connected to the condensers 46X, 46Y and 46Z of the refrigerators 44X, 44Y and 44Z. Accordingly, the number of cooling towers which are used as the cooling devices of the refrigerators 44X, 44Y and 44Z can be controlled to three. The above description is only one example, and by changing the positions of the on-off valves 68 which are closed, the number of cooling towers for preliminary cooling in each system, and the number of cooling towers for cooling refrigerators can be individually controlled.

In winter when the outside air temperature is low, a free cooling operation using any of the cooling towers 42A to 42H as the cold heat source is performed. In the free cooling operation, the on-off valves 62X, 62Y, 62Z, 63X, 63Y and 63Z are opened, and the on-off valves 60X, 60Y and 60Z are closed. Thereby, as in the intermediate operation, any of the cooling towers 42A to 42H is connected to the load parts 24X, 24Y and 24Z. At this time, by stopping the operation of the refrigerators 44X, 44Y and 44Z, the cooling water which is cooled in the cooling towers 42A to 42H is circulated and supplied to the load parts 24X, 24Y and 24Z, and the free cooling operation using the cooling towers 42A to 42H as the cold heat source is performed. At the time of the free cooling operation, by opening and closing any of the on-off valves 68, the number of cooling towers 42A to 42H which are used can be individually controlled in each system. Further, the systems of the load parts 24X, 24Y and 24Z are connected to different cooling towers 42A to 42H, and therefore, an optimum amount of the cooling water at an optimum temperature can be generated for each of the systems.

The aforementioned refrigerator operation, intermediate operation and free cooling operation are automatically switched in accordance with the outside air temperature and the load conditions. Further, switching of the operation mode at this time is not limited to simultaneous switching in all the systems of the load parts 24X, 24Y and 24Z, but may be individually controlled in each of the systems. For example, while the intermediate operation and the free cooling operation are performed in the systems of the load parts 24X and 24Y, the refrigerator operation may be performed in the system of the load part 24Z. In this case, in the system of the load part 24Z, the cooling tower for preliminary cooling and the cooling tower for free cooling are not required, and therefore, the number of cooling towers which are used in the systems of the load part 24X and the load part 24Y can be increased.

For various combinations of the operation modes and the number of cooling towers used on that occasions, various patterns are simulated with the outside air temperature and the load condition as the input values. From the result, the minimum required cold heat amount is obtained, and in order to supply the cold heat amount, selection is made from the cooling towers 42A to 42H to operate the selected cooling towers. Thereby, the energy consumption amount as an entire system can be reduced.

As described above, according to the present embodiment, the number of cooling towers in each of the operation modes that are the refrigerator operation, intermediate operation and free cooling operation can be controlled. Therefore, by operating the minimum required number of cooling towers 42A to 42H, energy consumption can be reduced.

In the above described embodiment, turbo refrigerators are adopted as the refrigerators 44X, 44Y and 44Z, and can be controlled by an inverter. In this case, the energy consumption of the refrigerators 44X, 44Y and 44Z can be reduced.

Further, in the above described embodiment, the rotational speeds of the pumps 50X, 50Y, 50Z, 52X, 52Y, 52Z, 58X, 58Y and 58Z can be controlled by an inverter. Thereby, the flow rate of the cooling water can be controlled, and the energy consumption which is spent in circulation of the cooling water can be reduced.

The above described embodiment is the example in which the pipings are connected so that the numbers of cooling towers for the load parts 24X, 24Y and 24Z are two, two and one at the time of the intermediate operation and the free cooling operation, but the connection of the pipings is not limited to this, and various modes can be adopted. For example, FIG. 3 is an example in which the number of cooling towers for the load part 24X can be increased. In the air-conditioning system of FIG. 3, bypass pipings 80 and 82 are provided, and one end (right end in FIG. 3) of the piping 80 is connected to the piping x6, whereas the other end (left end in FIG. 3) is branched and connected to the main piping j2 to be in communication with the pipings a2, b2 and c2. One end (right end in FIG. 3) of the piping 82 is connected to the piping x5, and the other end (left end in FIG. 3) is branched to be connected to the main piping j1 so that branched portions are communicable with the pipings a1, b1 and c1. Further, the on-off valves 84 are provided in the branched pipe portions of the piping 80 and the branched pipe portions of the piping 82, and by opening and closing the on-off valves 84, the cooling towers 42A, 42B and 42C communicate with or are shut off from the load part 24X through the pipings x5 and x6. The on-off valves 84 are electrically connected to the control device 70, and are subjected to opening and closing control by the control device 70. Accordingly, the control device 70 can select whether or not to operate the cooling towers 42A, 42B and 42C for the load part 24X.

In the air-conditioning system of FIG. 3 configured as described above, the five cooling towers 42A, 42B, 42C, 42G and 42H can be operated for the load part 24X while the two cooling towers 42E and 42F are operated for the load part 24Y at the time of free cooling, and the number of cooling towers for the load part 24X can be controlled in the range of zero to five. Further, if the free cooling operation of the load parts 24Y and 24Z is stopped, the number of cooling towers for the load part 24X can be controlled in the range of zero to eight. Therefore, according to the present embodiment, the number of cooling towers for the load part 24X can be increased, and the free cooling operation can be performed for a long term.

FIG. 4 shows a modified example of the air-conditioning system 10 of FIG. 1. The air-conditioning system shown in FIG. 4 has a system configuration in which the intermediate operation and the free cooling operation are not performed in the load part 24Z. Specifically, as compared with the air-conditioning system 10 of FIG. 1, the air-conditioning system of FIG. 4 does not have the cooling tower 42D, the pipings d1, d2, z5 and z6, the on-off valves 60Z, 62Z and 63Z, the three-way valve 64Z and the bypass pipe 66Z, and has a configuration at reduced cost. Further, the connecting position of the piping y5 and the main piping j1 and the connecting position of the piping y6 and the main piping j2 differ from each other.

As an operation example of the air-conditioning system of FIG. 4 as configured as described above, for example, in the season at a high outside air temperature (for example, June to September), the refrigerator operation is performed in all the load parts 24X, 24Y and 24Z. On this occasion, especially in the time of the year in which the outside air temperature is high (for example, July and August), the number of cooling towers is controlled to six (42A, 42B, 42C, 42E, 42F, 42G), and in the time of the year (for example, June and September) in which the outside air temperature is slightly lower than July and August, the number of cooling towers is controlled to five (42A, 42B, 42C, 42E, 42F). Control of the number of cooling towers is performed by controlling the on-off valves 68 and the cooling towers 42A to 42H by the control device 70 as in the above described air-conditioning system of FIG. 1.

In the time of the year (for example, May and October) in which the outside air temperature is slightly lower than that at the time of the refrigerator operation, the refrigerator operation is performed in the load parts 24Y and 24Z, whereas in the load part 24X, the operation is switched to the free cooling operation. At this time, the three cooling towers 42A to 42C are allowed to communicate with the condensers 46Y and 46Z of the refrigerators 44Y and 44Z, and are used for the refrigerator operation of the load parts 24Y and 24Z. Further, the four cooling towers 42E to 42H are used for the free cooling operation of the load part 24X.

At the time of the year (for example, November to April) when the outside air temperature is low, free cooling is performed in the load parts 24X and 24Y. At this time, the number of cooling towers can be changed in accordance with the outside air temperature. More specifically, at the time of the year when the outside air temperature is slightly high (for example, November and April), the number of cooling towers for the load part 24Y is increased to five (42A, 42B, 42C, 42E, 42F), and the number of cooling towers for the load part 24X is reduced to two (42G, 42H). Further, at the time of the year when the outside air temperature is low (for example, December to March), the number of cooling towers for the load part 24Y is decreased to four (42A, 42B, 42C, 42E), and the number of the cooling towers for the load part 24X is increased to three (42F, 42G, 42H).

The above described operation pattern can be determined based on the outside air wet bulb temperature and the load conditions of the load parts 24X to 24Z. For example, based on the outside air wet bulb temperature and the load conditions, switch control of the number of cooling towers can be performed by the optimization arithmetic operation of the number of cooling towers and systems with the energy consumption amount as the evaluation function. Further, the arithmetic operation result may be tabulated, and control may be performed.

Second Embodiment

FIG. 5 is a system diagram schematically showing the configuration of an air-conditioning system 11 of a second embodiment. The air-conditioning system 11 shown in FIG. 5 is the system which air-conditions the load part 24 of one system. The members having the same configurations and operations as those in the first embodiment shown in FIG. 1 will be assigned with the same reference numerals and characters (X to Z are excluded) and the description of them will be omitted.

The air-conditioning system 11 shown in FIG. 5 includes one refrigerator 44 and three cooling towers 42A to 42C. A condenser 46 of the refrigerator 44 is connected to each of the cooling towers 42A to 42C, and the cooling towers 42A to 42C are connected in parallel to the condenser 46. Specifically, the pipings a1 to c1 for draining the cooling water are connected to the cooling towers 42A to 42C, and after the pipings a1 to c1 are connected to the main piping j1, the main piping j1 is connected to the condenser 46. The main piping j2 connected to the condenser 46 is branched into the pipings a2 to c2 for inflow of the cooling water, and the pipings a2 to c2 are connected to the respective cooling towers 42A to 42C. A pump 52 is placed in the main piping j1, and by driving the pump 52, the cooling water circulates between the cooling towers 42A to 42C and the condenser 46, and the circulation amount of the cooling water is regulated. Further, a three-way valve 54 is provided in the main piping j2 to allow part of the cooling water flowing in the main piping j2 into the main piping j1 through a bypass piping 56 so that the flow rate regulation can be performed.

An evaporator 48 of the refrigerator 44 is connected to the load part 24 through pipings k3 and k4. The pump 52 is connected to the piping k3. Thereby, the cooling water cooled in the evaporator 48 can be circulated and supplied to the load part 24.

The cooling towers 42A to 42C are connected in series to the evaporator 48. Specifically, the piping k3 is connected to the main piping j2 through the piping k6, and is connected to the main piping j1 through the piping k5. Accordingly, the cooling water which flows in the piping k3 flows into at least one of the cooling towers 42A to 42C through the piping k6 and the main piping j2, and returns to the original piping k3 through the main piping j1 and the piping k5. Thereby, the cooling towers 42A to 42C are connected in series to the evaporator 48 of the refrigerator 44. A pump 58 is provided in the piping k6, and by driving the pump 58, the cooling water in the piping k3 flows into the piping k6. Further, in the piping k3 and the piping k6, on-off valves 60 and 62 are provided at the immediate downstream side from the connecting portions. Further, an on-off valve 63 is provided in the piping k5. By performing opening and closing operation of these on-off valves 60, 62 and 63, it can be selected whether or not to feed the cooling water in the piping k3 to the cooling towers 42A to 42C. Further, a three-way valve 64 is placed in the piping k6, and by operating the three-way valve 64, part of the cooling water which flows in the piping k6 flows into the piping k5 through the bypass pipe 66, and flow rate regulation is performed.

In the above described main pipings j1 and j2, a plurality of on-off valves 68 for selecting the cooling towers 42A to 42C are placed. The on-off valves 68 are placed between the connecting portions where the pipings a1 to c1 are connected on the main piping j1, or between the connecting portions where the pipings a2 to c2 are connected on the main piping j2. By opening and closing any of the on-off valves 68, selection can be made from the cooling towers 42A to 42C in which the cooling water is circulated. The opening and closing operation of the on-off valve 68 is performed by the control device 70.

The control device 70 is connected to the sensor 72 for measuring an outside air wet-bulb temperature, and receives the measurement data of the outside air temperature from the sensor 72. Further, the control device 70 is connected to the load part 24, and receives the data of the load condition from the load part 24. Further, the control device 70 is connected to a drive device (not illustrated) of fans or the like of the cooling towers 42A to 42C, and can control operation and stoppage of the cooling towers 42A to 42C. The control device 70 obtains the minimum required flow rate of the cooling water by simulation from the outside air temperature and the data of the load condition, and determines the cooling towers to be operated among the cooling towers 42A to 42C so as to be able to supply the cooling water at the corresponding flow rate. The control device 70 operates the cooling towers among the cooling towers 42A to 42C, and controls the on-off valves 68 to circulate the cooling water into the cooling towers among the cooling towers 42A to 42C. For the cooling towers into which the cooling water does not need to be fed among the cooling towers 42A to 42C, such cooling towers among the cooling towers 42A to 42C are stopped.

Next, an operation method of the air-conditioning system 11 configured as described above will be described.

In summer when the outside air temperature is high, a refrigerator operation using the refrigerator 44 as the cold heat source is performed. In the refrigerator operation, the on-off valve 60 is opened, and the on-off valves 62 and 63 are closed. Thereby, a conduit configuration as shown in FIG. 6A is formed. As shown in FIG. 6A, the cooling towers 42A to 42C are connected to the condenser 46 of the refrigerators 44, and the cooling water cooled in the cooling towers 42A to 42C is circulated and supplied to the condenser 46. Further, the evaporator 48 of the refrigerator 44 and the load part 24 are connected, and the cooling water cooled in the evaporators 48 is supplied to the load part 24. Thereby, the refrigerator 44 is used as the cold heat source, and cold heat can be supplied to the load part 24. At this time, by opening and closing any of the on-off valves 68, the number of cooling towers to be used of the cooling towers 42A to 42C can be controlled.

In an intermediate operation, the on-off valves 62 and 63 are opened, and the on-off valve 60 is closed. Thereby, some of the cooling towers 42A to 42C and the evaporator 48 are connected in series. Therefore, the cooling water is preliminarily cooled in some of the cooling towers 42A to 42C first, and thereafter, is cooled in the evaporator 48, and is supplied to the load part 24. Accordingly, some of the cooling towers 42A to 42C and the refrigerator 44 can be used in combination as the cold heat source. In the intermediate operation, remaining cooling towers of the cooling towers 42A to 42C and the condenser 46 of the refrigerator 44 are connected, whereby the cooling water which is cooled in the remaining cooling towers of the cooling towers 42A to 42C is circulated and supplied to the condenser 46, and is used for cooling of the refrigerator 44. At the time of the intermediate operation, the number of cooling towers 42A to 42C which are used can be controlled by opening and closing any of the on-off valves 68. As one example of it, FIG. 6B shows the example in which the on-off valves 68 are closed between the cooling tower 42A and the cooling tower 42B, and between the cooling tower 42B and the cooling tower 42C. In this example, the one cooling tower 42C is connected in series to the evaporator 48 of the refrigerator 44, and therefore, the number of the cooling towers for preliminary cooling is one. Further, the one cooling tower 42A is connected to the condenser 46 of the refrigerator 44, and therefore, the number of cooling towers to be used as the cooling device for the refrigerator 44 is controlled to one. The above description is one example, and by changing the positions of the on-off valves 68 to be closed, the number of cooling towers for preliminary cooling and the number of cooling towers for cooling the refrigerator can be individually controlled.

In winter when the outside air temperature is low, a free cooling operation using any of the cooling towers 42A to 42C as the cold heat source is performed. In the free cooling operation, the on-off valves 60 are closed. Thereby, as in the intermediate operation, the cooling towers 42A to 42C are connected to the load part 24. At this time, the operation of the refrigerator 44 is stopped. Accordingly, the cooling water which is cooled in the cooling towers 42A to 42C is circulated and supplied to the load part 24, and the free cooling operation with the cooling towers 42A to 42C as the cold heat source is performed. At the time of the free cooling operation, by opening and closing any of the on-off valves 68, the number of cooling towers 42A to 42C to be used can be controlled. For example, as in FIG. 6C, the two cooling towers 42B and 42C can be used for a free cooling operation.

As described above, according to the present embodiment, the number of cooling towers in each of the operation modes that are the refrigerator operation, intermediate operation and free cooling operation can be controlled. Therefore, by operating the minimum required number of cooling towers 42A to 42C, energy consumption can be reduced.

In the above described first and second embodiments, the number of cooling towers which are operated is controlled, but while all the cooling towers are being operated, the numbers of cooling towers assigned to the circulation destinations of the cooling water may be changed.

Third Embodiment

FIG. 7 is a system configuration schematically showing the configuration of an air-conditioning system 10 of a third embodiment. The air-conditioning system 10 shown in FIG. 7 is the system which air-conditions the load part 24 of one system. The members having the same configurations and operations as those in the first embodiment shown in FIG. 1 will be assigned with the same reference numerals and characters and the description of them will be omitted in some cases.

As compared with the first embodiment, besides the number of cooling towers and refrigerators, the cooling towers are open type cooling towers including heat exchangers and the load part is of one system in the third embodiment.

The air-conditioning system 10 shown in FIG. 7 includes two refrigerators 44X and 44Y, five cooling towers 42A to 42E, and heat exchangers 80X and 80Y for free cooling which are connected to the cooling towers 42A to 42E. In the present embodiment, the cooling towers 42A to 42E are configured by open type cooling towers. An open type cooling tower includes a water sprinkling pipe for sprinkling cooling water, and a water collecting pipe for collecting the sprinkled cooling water, and the cooling water is sprinkled from the water sprinkling pipe to be in contact with outside air, and thereby deprived of heat of vaporization to be cooled. When open type cooling towers are adopted as the cooling towers 42A to 42E, in the operation in the refrigerators 44X and 44Y, the cooling water temperature of the refrigerators 44X and 44Y becomes low as compared with the case of adopting closed type cooling towers, the coefficients of performance of the refrigerators 44X and 44Y are improved, and energy saving is realized. Further, the open type cooling tower can make the installation area smaller as compared with the closed type cooling tower, and cost can be reduced.

The connection relation of the heat exchangers 80X and 80Y, the cooling towers 42A to 42E and the load part 24 will be described. The pipings a1 to e1 for draining the cooling water are connected to the cooling towers 42A to 42E, and the pipings a1 to e1 are connected to the main piping j1. After the main piping j1 is branched into pipings x5 and y5, they are connected to the heat exchangers 80X and 80Y.

The pipings x6 and y6 for draining the cooling water are connected to the heat exchangers 80X and 80Y, and the pipings x6 and y6 are connected to the main piping j2. The main piping j2 is branched into the pipings a2 to e2, which are connected to water sprinkling pipes (not illustrated) of the respective cooling towers 42A to 42E. Pumps 59x and 59y are placed in the pipings x5 and y5. By performing drive control of the pumps 59x and 59 individually, the cooling water is individually circulated between each of the heat exchangers 80X and 80Y and the cooling towers 42A to 42E.

Pipings x7 and x8 are connected to the heat exchanger 80X. The piping x7 is connected to the piping x3, and the piping x8 is connected to the pipings x3 and x4. Further, pipings y7 and y8 are connected to the heat exchanger 80Y. The piping y7 is connected to the piping y3, and the piping y8 is connected to the piping y4. The heat exchanger 80X is connected to the load part 24 through the pipings x3, x4, x7 and x8. The heat exchanger 80Y is connected to the load part 24 through the pipings y3, y4, y7 and y8.

The pump 58X is placed in the piping x7, and the pump 58Y is placed in the piping y7. By driving the pump 58X, the cold water can be circulated between the heat exchanger 80X and the load part 24. Similarly, by driving the pump 58Y, the cooling water can be circulated between the heat exchanger 80Y and the load part 24.

The on-off valve 60X is provided in the piping x3, the on-off valve 62X is provided in the piping x7, and the on-off valve 63X is provided in the piping x8. By performing an opening and closing operation of these on-off valves 60X, 62X and 63X, it can be selected whether to feed the cold water in the pipings x3 and x4 to the heat exchanger 80X or to the refrigerator 44X.

Similarly, the on-off valve 60Y is provided in the piping y3, the on-off valve 62Y is provided in the piping y7, and the on-off valve 63Y is provided in the piping y8. By performing opening and closing operation of these on-off valves 60Y, 62Y and 63Y, it is selected whether to feed the cold water in the pipings y3 and y4 to the heat exchanger 80y or to the refrigerator 44Y.

Next, the connection relation of the refrigerators 44X and 44Y, the cooling towers 42A to 42E and the load part 24 will be described. The refrigerators 44X and 44Y includes therein the condensers 46X and 46Y, and the evaporators 48X and 48Y. The evaporator 48X is connected to the load part 24 through the pipings x3 and x4. Further, the evaporator 48Y is connected to the load part 24 through the pipings y3 and y4.

The condensers 46X and 46Y of the refrigerators 44X and 44Y are respectively connected to the cooling towers 42A to 42E. The cooling towers 42A to 42E are connected in parallel to the condensers 46X and 46Y. The pipings a1 to e1 for draining the cooling water are connected to the cooling towers 42A to 42E, and the pipings a1 to e1 are connected to the main piping j1. After the main piping j1 is branched into the pipings x1 and y1, they are connected to the respective condensers 46X and 46Y. The pipings x2 and y2 for draining the cooling water are connected to the condensers 46X and 46Y, and the pipings x2 and y2 are connected to the main piping j2. The main piping j2 is branched into the pipings a2 to e2, and they are connected to the water sprinkling pipes (not illustrated) of the respective cooling towers 42A to 42E. Thereby, the cooling water cooled in the respective cooling towers 42A to 42E can be circulated and supplied to the condensers 46X and 46Y, and the cooling towers 42A to 42E can be used as the cooling device for the refrigerators 42X and 44Y.

The pumps 52x and 52y are placed in the pipings x1 and y1. By performing drive control of the pumps 52x and 52y individually, the cooling water is circulated into the respective condensers 46X and 46Y individually, and the circulation amount of it is regulated.

The evaporator 48X of the refrigerator 44X is connected to the load part 24 through the pipings x3 and x4. The pump 50X is placed in the piping x3, and by driving the pump 50X, the cold water is circulated between the evaporator 48X and the load part 24. Similarly, the evaporator 48Y of the refrigerator 44Y is connected to the load part 24 through the pipings y3 and y4. The pump 50Y is placed in the piping y3, and by driving the pump 50Y, the cold water is circulated between the evaporator 48Y and the load part 24.

The pipings a1 to e1 are connected to the main piping j1, the pipings a2 to e2 are connected to the main piping j2, and the aforementioned cooling towers 42A to 42E are connected in parallel to the refrigerators 44X and 44Y. Similarly, the cooling towers 42A to 42E are connected in parallel to the heat exchangers 80X and 80Y. In the present embodiment, the main pipings j1 and j2 form a common circulation passage of the cooling water with respect to the heat exchangers 80X and 80Y and the refrigerators 44X and 44Y.

A plurality of on-off valves 68 for selecting the cooling towers 42A to 42E are placed in the aforementioned main pipings j1 and j2. The on-off valves 68 are placed between the connecting portions where the pipings a1 to e1 are connected on the main piping j1, or are placed between the connecting portions where the pipings a2 to e2 are connected on the main piping j2. By opening and closing any of the on-off valves 68, the cooling towers 42A to 42E to which the cooling water is circulated can be selected. The opening and closing operation of the on-off valve 68 is performed by the control device 70.

The control device 70 is connected to the sensor 72 for measuring the outside air wet bulb temperature, and receives the measurement data of the outside air temperature from the sensor 72. Further, the control device 70 is connected to the load part 24, and receives the data of the load conditions from the load part 24. Further, the control device 70 is connected to the drive device (not illustrated) of the fans or the like of the cooling towers 42A to 42E, so as to be able to control operation and stoppage of the cooling towers 42A to 42E. The control device 70 determines the cooling towers to be operated among the cooling towers 42A to 42E by the simulation from the outside air temperature and the data of the load condition. Subsequently, the control device 70 operates the cooling towers among the cooling towers 42A to 42E, and controls the on-off valve 68 to circulate the cooling water to the cooling towers among the cooling towers 42A to 42E. Further, for the cooling towers into which the cooling water does not have to be fed among the cooling towers 42A to 42E, the control device 70 stops such cooling towers among the cooling towers 42A to 42E.

Further, by the control device 70, each of the inverters provided in the fans of the cooling towers 42A to 42E, the pumps 50X, 50Y, 52X, 52Y, 58X, 58Y, 59X and 59Y is controlled, and is driven so that the total power consumption of the refrigerators, fans and pumps becomes the minimum value.

The control is performed as follows as an example. First, the outside air wet bulb temperature, the load, the cooling water temperatures at the outlets of the cooling towers 42A to 42E, and the cold water temperatures at the outlets of the heat exchangers 80X and 80Y are used as input values, and the input value data are input to the simulator which performs simulation for obtaining the total value of the power consumption of the fans of the cooling towers 42A to 42E, and the pumps 50X, 50Y, 52X, 52Y, 58X, 58Y, 59X, 59Y and the like. At this time, the input value data are input to the simulator while the input values of the cooling water temperatures and the cold water temperature are changed. From the simulation result, the frequencies (rotational speeds) of the fans of the cooling towers 42A to 42E and the pumps 50X, 50Y, 52X, 52Y, 58X, 58Y, 59X and 59Y at which the total value of the power consumption becomes minimum are obtained as the optimal values. By the control device 70, the actual cooling water temperature and the cold water temperature are set to the obtained optimal values. By the control device 70, the inverters of the cooling water pumps (52X, 52Y, 59X, 59Y) and the cold water pumps (50X, 50Y) are controlled to correspond to the change of the outside air wet bulb temperature state and the cooling load amount to change the flow rate, and energy saving is realized.

In the system operating the refrigerators, by using the simulator for performing simulation for obtaining the total value of the power consumption of the refrigerator, cooling tower, cooling water pump and cold water pump, the cooling water pump frequency, the cooling water temperature and the cold water temperature at which the total value of the power consumption becomes minimum are obtained, and the cooling tower fans and pumps are controlled.

Next, an operation method of the air-conditioning system 10 configured as described above will be described. In summer when the outside air temperature is high, the refrigerator operation using the refrigerators 44X and 44Y as the cold heat source is carried out. In the refrigerator operation, the on-off valves 60X and 60Y are opened, and the on-off valves 62X, 62Y, 63X and 63Y are closed. Thereby, the conduit configuration as shown in FIG. 8A is formed. As shown in FIG. 8A, the cooling towers 42A to 42E are connected to the condensers 46X and 46Y of the refrigerators 44X and 44Y. By driving the pumps 52X and 52Y, the cooling water cooled in the cooling towers 42A to 42E is circulated and supplied to the condensers 46X and 46Y. The evaporators 48X and 48Y of the refrigerators 44X and 44Y and the load part 24 are connected. By driving the pumps 50X and 50Y, the cold water cooled in the evaporators 48X and 48Y is supplied to the load part 24. Therefore, cold heat can be supplied to the load part 24 with the refrigerators 44X and 44Y as the cold heat source. At this time, by opening and closing operation of any of the on-off valves 68, the number of cooling towers 42A to 42E to be used can be also controlled.

In winter when the outside air temperature is low, a free cooling operation using any of the cooling towers 42A to 42E as the cold heat source is performed. In the free cooling operation, the pumps 50X and 50Y are stopped, the on-off valves 60X and 60Y are closed, and the on-off valves 62X, 62Y, 63X and 63Y are opened. The pressure loss of the on-off valves 63X and 63Y is smaller than the pressure loss of the pumps 50X and 50Y. Therefore, the cold water from the heat exchangers 80X and 80Y flows in the pipings x8 and y8, and flows into the load part 24 through the on-off valves 63X and 63Y. Thereby, the cooling towers 42A to 42E are connected to the heat exchangers 80X and 80Y, and the heat exchangers 80X and 80Y are connected to the load part 24. At this time, operation of the refrigerators 44X and 44Y is stopped. By driving the pumps 59X and 59Y, the cooling water cooled in the cooling towers 42A to 42E is circulated and supplied to the heat exchangers 80X and 80Y. By driving the pumps 58X and 58Y, the cold water cooled in the heat exchangers 80X and 80Y is supplied to the load part 24. At the time of a free cooling operation, by opening and closing any of the on-off valves 68, the number of cooling towers 42A to 42E to be used can be controlled. For example, in FIG. 8B, the three cooling towers 42C to 42E can be used for the free cooling operation.

Next, the intermediate operation which is performed at the time of the outside air temperature between summer and winter will be described with reference to FIG. 9. In the intermediate operation, the cooling towers are switched to the refrigerator side and the heat exchanger side for free cooling. Specifically, the operation using the refrigerators 44X and 44Y and some of the cooling towers 42A to 42E as the cold heat source is performed. The on-off valve 68 at the inlet side and the on-off valve 68 at the outlet side between the cooling towers 42B and 42C are closed. In accordance with the outside air temperature and the load condition, the on-off valve 68 between the cooling towers 42A and 42B and the on-off valve 68 between the cooling towers 42C and 42D are switched to closing. The on-off valves 60X, 63X, 60Y and 63Y are closed, and the on-off valves 62X and 62Y are opened. Thereby, the passage for feeding water to the refrigerator is formed in the rear stage of the heat exchanger for free cooling. Specifically, the cold water flows in the pipings x3 and x7, the heat exchanger 80X, and the pipings x8, x3 and x4, and is circulated and supplied to the evaporator 48X as shown by the arrows. Similarly, the cold water flows in the pipings y3 and y7, the heat exchanger 80y, and the pipings y8, y3 and y4, and is circulated and supplied to the evaporator 48y as shown by the arrows.

As such, according to the present embodiment, the number of cooling towers in each of the operation modes of the refrigerator operation, intermediate operation and free cooling operation can be controlled. Therefore, by operating the minimum required number of cooling towers among the cooling towers 42A to 42E, energy consumption amount can be reduced.

Further, the piping system including the on-off valves 63X and 63Y is eliminated, that is, the piping for connecting the piping x3 and the piping x4, and the piping for connecting the piping y3 and y4 are eliminated, and at the time of a free cooling operation, cold water is fed to the refrigerators in the case of the intermediate operation as in FIG. 6 to cope with the cases of the refrigerator operation, the intermediate operation and the free cooling operation.

FIG. 10 shows a modified example of the air-conditioning system 10 of FIG. 7. The air-cooling system shown in FIG. 10 has a piping system which can switch the cooling water system for feeding the water for each cooling tower.

As shown in FIG. 10, the main piping j1 is connected to the refrigerators 44X and 44Y through the pipings x2 and y2. The main piping j2 is connected to the refrigerators 44X and 44Y through the pipings x1 and y1. The pipings a1 to e1 are connected to the main piping j1, and the cooling towers 42A to 42E and the main piping j1 are connected through the pipings a1 to e1. The on-off valve 68 is provided at each of the pipings a1 to e1. The pipings a2 to e2 are connected to the main piping j2, and the cooling towers 42A to 42E and the main piping j2 are connected through the pipings a2 to e2. The on-off valve 68 is provided in each of the pipings a2 to e2.

Meanwhile, a main piping j3 is connected to the heat exchangers 80X and 80Y through the pipings x5 and y5. Further, a main piping j4 is connected to the heat exchangers 80X and 80Y through the pipings x6 and y6. Pipings a3 to e3 are connected to the main piping j3, and the cooling towers 42A to 42E and the main piping j3 are connected through the pipings a3 to e3. The on-off valve 68 is provided at each of the pipings a3 to e3. Pipings a4 to e4 are connected to the main piping j4, and the cooling towers 42A to 42E and the main piping j4 are connected through the pipings a4 to e4. The on-off valve 68 is provided at each of the pipings a4 to e4.

In the present embodiment, the circulation passage is formed between the refrigerators 44X and 44Y and the cooling towers 42A to 42E by the main pipings j1 and j2, and a circulation passage is formed between the heat exchangers 80X and 80Y and the cooling towers 42A to 42E by the main pipings j3 and j4.

By opening and closing any of a plurality of on-off valves 68 provided in the pipings a1 to e1, a2 to e2, a3 to e3 and a4 to e4, any of the refrigerators 44X and 44Y and the heat exchangers 80X and 80Y for free cooling can be selected for the cooling water for each of the cooling towers 42A to 42E.

By adopting such a configuration, the number of on-off valves where the cooling water passes when the cooling water is fed to the pipings can be reduced. Thereby, the piping resistance becomes low, and the power of the pump can be reduced. In the present embodiment, by feeding the cooling water through only one on-off valve 68, the cooling water from the cooling towers 42A to 42E can be fed to the main piping j1 or j3.

Meanwhile, in the configuration shown in FIG. 7, the number of on-off valves to the heat exchanger is large in the cooling towers far from the heat exchanger, and the piping resistance is large. For example, the cooling water in the cooling tower 42A passes through a plurality of on-off valves 68 and is fed to the heat exchangers 80X and 80Y.

Further, in the air-conditioning system 10 shown in FIG. 10, water can be fed irrespective of the sequence from the heat exchangers and the refrigerators.

Accordingly, the degree of freedom of selection of the cooling tower to be switched to the heat exchanger system and the refrigerator system becomes high. The systems of the inlet and outlet of the cooling tower may be realized by the branched pipes.

Claims

1. An air-conditioning method comprising the steps of:

performing a refrigerator operation using a refrigerator to which cooling water cooled in a plurality of cooling towers is supplied as a cold heat source, and

performing a free cooling operation using at least some of the plurality of cooling towers as a cold heat source,

wherein at a time of the free cooling operation, the number of the cooling towers which are operated is controlled.

2. The air-conditioning method according to claim 1,

wherein an intermediate operation which uses at least some of the plurality of cooling towers as a cold heat source in combination with the refrigerator is performed, and at a time of the intermediate operation, the number of the cooling towers which are operated to be the cold heat source is controlled.

3. The air-conditioning method according to claim 1,

wherein switching of the operation is performed in accordance with an outside air temperature and an air-conditioning load condition.

4. The air-conditioning method according to claim 1,

wherein a plurality of the refrigerators are provided, and the number of the cooling towers which are operated is controlled for each of the plurality of refrigerators.

5. The air-conditioning method according to claim 1,

wherein the refrigerator is a turbo refrigerator, and inverter control is performed for the refrigerator.

6. The air-conditioning method according to claim 1,

wherein by controlling a rotational speed of a pump which circulates the cooling water cooled in the plurality of cooling towers or the refrigerator, a flow rate of the cooling water is controlled.

7. An air-conditioning system, comprising:

a plurality of cooling towers that cool cooling water;

a refrigerator having a condenser and an evaporator;

a circulation line for a refrigerator operation that circulates the cooling water cooled in the cooling tower into the condenser, and circulates the cooling water cooled in the evaporator into an air-conditioning load part;

a circulation line for a free cooling operation that circulates the cooling water cooled in the cooling tower into the air-conditioning load part;

a line switching device that switches the circulation line for the refrigerator operation and the circulation line for the free cooling operation, and regulates the number of cooling towers to be connected to the circulation line for the free cooling operation; and

a control device that controls the line switching device and individually controls operation and stoppage of the plurality of cooling towers.

8. The air-conditioning system according to claim 7, further comprising a circulation line for an intermediate operation that connects the plurality of cooling towers in series to the evaporator of the refrigerator,

wherein the line switching device switches the lines including the circulation line for the intermediate operation, and changes the number of cooling towers to be connected to the circulation line for the intermediate operation.

9. The air-conditioning system according to claim 7,

wherein a plurality of the refrigerators are provided, and the number of the cooling towers which are connected to each of the refrigerators is changed by the line switching device.