Patent Publication Number: US-10330365-B2

Title: Air-conditioning apparatus and air-conditioning system that selects control based on sensible or latent heat cooling capability

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a U.S. national stage application of PCT/JP2014/062757 filed on May 13, 2014, the contents of which are incorporated herein by reference. 
     TECHNICAL FIELD 
     The present invention relates to an air-conditioning apparatus and an air-conditioning system. 
     BACKGROUND ART 
     An air-conditioning apparatus conventionally known is configured to control the supply air temperature, i.e., blown-out air temperature and humidity, by cooling and dehumidifying air and supplying the air to an indoor space (see Patent Literature 1, for example). 
     The air-conditioning apparatus described in Patent Literature 1 is configured to select one from between superheat degree control and evaporating temperature control in accordance with a cooling capability. 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: Japanese Unexamined Patent Application Publication No. 9-014766 (paragraph [0029]) 
     SUMMARY OF INVENTION 
     Technical Problem 
     When the air-conditioning apparatus described in Patent Literature 1 is used, however, the COP decreases when the air-conditioning apparatus exercises the superheat degree control, and the latent heat capability is insufficient when the air-conditioning apparatus exercises the evaporating temperature control. Accordingly, conventional air-conditioning apparatuses such as that described in Patent Literature 1 have the problem where it is not possible to realize blown-out air temperature control with high energy efficiency, while guaranteeing comfortability. 
     To solve the problem described above, it is an object of the present invention to provide an air-conditioning apparatus and an air-conditioning system capable of realizing blown-out air temperature control with high energy efficiency, while guaranteeing comfortability. 
     Solution to Problem 
     An air-conditioning apparatus according to one embodiment of the present invention includes: a refrigerant circuit forming a refrigeration cycle by connecting together a compressor, an outdoor heat exchanger, an expansion valve, and an indoor heat exchanger via a refrigerant pipe; and a control unit controlling a blown-out air temperature by causing the indoor heat exchanger to exchange heat while controlling the refrigeration cycle based on one of a sensible heat capability and a latent heat capability calculated from a cooling capability of the refrigerant circuit and a cooling load of the refrigerant circuit. The control unit includes: a capability judging unit judging the cooling capability of the refrigerant circuit based on the one of the sensible heat capability and the latent heat capability; and a control selecting unit selecting one from between superheat degree control to control a degree of superheat and evaporating temperature control to control an evaporating temperature, based on a determination result obtained by the capability judging unit. 
     Advantageous Effects of Invention 
     The air-conditioning apparatus of one embodiment of the present invention is configured to select one from between the superheat degree control and the evaporating temperature control on the basis of one of the sensible heat capability and the latent heat capability. Accordingly, the air-conditioning apparatus of the one embodiment of the present invention is able to avoid the situation where the latent heat capability is insufficient. Consequently, the air-conditioning apparatus of the one embodiment of the present invention achieves an advantageous effect where it is possible to realize blown-out air temperature control with high energy efficiency. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a diagram illustrating a schematic configuration of a refrigerant circuit of an air-conditioning apparatus  3  according to Embodiment 1 of the present invention. 
         FIG. 2  is a diagram illustrating examples of devices provided for the refrigerant circuit of the air-conditioning apparatus  3  according to Embodiment 1 of the present invention. 
         FIG. 3  is a chart illustrating, on a psychrometric chart, examples of fluctuations in a blown-out air temperature observed when evaporating temperature control is exercised and when superheat degree control is exercised according to Embodiment 1 of the present invention. 
         FIG. 4  is a chart illustrating examples of fluctuations in absolute values of sensible heat capability levels and latent heat capability levels corresponding to the evaporating temperature control and the superheat degree control according to Embodiment 1 of the present invention. 
         FIG. 5  is a table illustrating examples of fluctuations in a sensible heat factor of a cooling capability exhibited in conjunction with fluctuations in the blown-out air temperature observed when the evaporating temperature control is exercised and when the superheat degree control is exercised according to Embodiment 1 of the present invention. 
         FIG. 6  is a diagram illustrating an example of a functional configuration of a control unit  63  according to Embodiment 1 of the present invention. 
         FIG. 7  is a flowchart for explaining an example of control exercised in the air-conditioning apparatus  3  according to Embodiment 1 of the present invention. 
         FIG. 8  is a diagram illustrating an example of a functional configuration of the control unit  63  according to Embodiment 2 of the present invention. 
         FIG. 9  is a flowchart for explaining an example of control exercised in the air-conditioning apparatus  3  according to Embodiment 2 of the present invention. 
         FIG. 10  is a diagram illustrating an example of a functional configuration of the control unit  63  according to Embodiment 3 of the present invention. 
         FIG. 11  is a flowchart for explaining an example of control exercised in the air-conditioning apparatus  3  according to Embodiment 3 of the present invention. 
         FIG. 12  is a diagram illustrating an example of a functional configuration of the control unit  63  according to Embodiment 4 of the present invention. 
         FIG. 13  is a chart illustrating an operation concept of hysteresis control according to Embodiment 4 of the present invention. 
         FIG. 14  is a flowchart for explaining an example of control exercised in the air-conditioning apparatus  3  according to Embodiment 4 of the present invention. 
         FIG. 15  is a diagram of an example of a functional configuration of the control unit  63  according to Embodiment 5 of the present invention. 
         FIG. 16  is a flowchart for explaining an example of control exercised in the air-conditioning apparatus  3  according to Embodiment 5 of the present invention. 
         FIG. 17  is a diagram of an example of a functional configuration of the control unit  63  according to Embodiment 6 of the present invention. 
         FIG. 18  is a flowchart for explaining an example of control exercised in the air-conditioning apparatus  3  according to Embodiment 6 of the present invention. 
         FIG. 19  is a diagram of an example of a schematic configuration of an air-conditioning system  1  according to Embodiment 7 of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Embodiments of the present invention will be described in details hereinafter with reference to the drawings. 
     Embodiment 1 
     A Configuration of Embodiment 1 
       FIG. 1  is a diagram illustrating a schematic configuration of a refrigerant circuit of an air-conditioning apparatus  3  according to Embodiment 1 of the present invention. As illustrated in  FIG. 1 , the air-conditioning apparatus  3  includes an outdoor unit  11  and an indoor unit  13  and is configured to supply blown-out air that air-conditions the temperature and humidity, to an air-conditioned space. The outdoor unit  11  includes a compressor  21 , a four-way valve  23 , an outdoor heat exchanger  25 , and an outdoor fan  31 . The indoor unit  13  includes an expansion valve  27 , an indoor heat exchanger  29 , and an indoor fan  33 . The air-conditioning apparatus  3  includes a refrigerant circuit forming a refrigerant cycle by connecting together the compressor  21 , the four-way valve  23 , the outdoor heat exchanger  25 , the expansion valve  27 , and the indoor heat exchanger  29 , via a refrigerant pipe  9 . 
     The quantity of the indoor unit  13  to be installed may be one or more. The four-way valve  23  may be omitted when the air-conditioning apparatus  3  operates with only one of cooling and heating functions. 
       FIG. 2  is a diagram illustrating examples of devices provided for the refrigerant circuit of the air-conditioning apparatus  3  according to Embodiment 1 of the present invention. As illustrated in  FIG. 2 , as the devices provided for the refrigerant circuit, an intake-air temperature/humidity detecting unit  41 , an evaporating temperature detecting unit  43 , and a compressor frequency adjusting unit  45  are provided, for example. Further, although not illustrated in the drawings, the air-conditioning apparatus  3  also includes a refrigerant superheat degree detecting unit, a blown-out air temperature detecting unit, a blown-out air temperature target value setting unit, and other units. 
     Next, fluctuations in a sensible heat capability and a latent heat capability observed in conjunction with fluctuations in an evaporating temperature or a degree of superheat will be explained with reference to  FIGS. 3 to 5 .  FIG. 3  is a chart illustrating, on a psychrometric chart, examples of fluctuations in a blown-out air temperature observed when evaporating temperature control is exercised and when superheat degree control is exercised according to Embodiment 1 of the present invention.  FIG. 4  is a chart illustrating examples of fluctuations in absolute values of sensible heat capability levels and latent heat capability levels corresponding to the evaporating temperature control and the superheat degree control according to Embodiment 1 of the present invention.  FIG. 5  is a table illustrating examples of fluctuations in a sensible heat factor of a cooling capability exhibited in conjunction with fluctuations in the blown-out air temperature observed when the evaporating temperature control is exercised and when the superheat degree control is exercised according to Embodiment 1 of the present invention. 
     As illustrated in  FIG. 3 , when the evaporating temperature rises from Te0 to Te1 while the degree of superheat is the same, the blown-out air temperature rises as indicated with the square symbols. In that situation, as the sensible heat factor of the cooling capability changes and the sensible heat factor gradually increases, the dehumidifying amount decreases. Further, since the evaporating temperature rises, the low-pressure level of the refrigerant circuit rises, and the difference between the low-pressure side and the high-pressure side decreases. Accordingly, the workload of the compressor  21  decreases, and the COP of the refrigeration cycle also increases. 
     In contrast, when the degree of superheat increases from SH0 to SH1 while the evaporating temperature is the same, the blown-out air temperature rises, as indicated with the circle symbols. In this situation, the sensible heat factor of the cooling capability does not change. 
     Accordingly, while one of the evaporating temperature control and the superheat degree control is being exercised, even when the blown-out air temperature is the same, the sensible heat factor of the cooling capability and the COP change. For example, as illustrated in  FIG. 4 , when the evaporating temperature rises while the degree of superheat remains at SHx, the decreasing amount in the absolute value of the latent heat capability is larger than the decreasing amount in the absolute value of the sensible heat capability. Further, as illustrated in  FIG. 4 , for example, when the degree of superheat increases while the evaporating temperature remains at Tex, the changing amount in the absolute value of the sensible heat capability and the changing amount in the absolute value of the latent heat capability are not different from each other. 
     In other words, as illustrated in  FIG. 5 , to raise the blown-out air temperature, there are some situations in which the evaporating temperature is raised and other situations in which the degree of superheat is raised. When the evaporating temperature is raised among those situations, since the sensible heat factor of the cooling capability increases, the ratio of the latent heat capability to the cooling capability decreases. In contrast, when the degree of superheat is raised, the sensible heat factor of the cooling capability is constant. 
     Further, as illustrated in  FIG. 5 , for example, to lower the blown-out air temperature, there are some situations in which the evaporating temperature is lowered and other situations in which the degree of superheat is lowered. When the evaporating temperature is lowered among those situations, since the sensible heat factor of the cooling capability decreases, the ratio of the latent heat capability to the cooling capability increases. In contrast, when the degree of superheat is lowered, the sensible heat factor of the cooling capability is constant. 
     Next, an example of blown-out air temperature control utilizing the relationship among the evaporating temperature, the degree of superheat, the sensible heat capability, and the latent heat capability explained with reference to  FIG. 5  will be explained with reference to  FIG. 6 .  FIG. 6  is a diagram illustrating an example of a functional configuration of a control unit  63  according to Embodiment 1 of the present invention. 
     The control unit  63  illustrated in  FIG. 6  is configured to control the blown-out air temperature by causing the indoor heat exchanger  29  to exchange heat while controlling the refrigeration cycle on the basis of one of the sensible heat capability and the latent heat capability calculated from the cooling capability of the refrigerant circuit and a cooling load of the refrigerant circuit. As illustrated in  FIG. 6 , a setting unit  61  is configured to supply information used for controlling the blown-out air temperature to the control unit  63  and includes a heat amount information storing unit  71  and a temperature information storing unit  73 . The control unit  63  includes a temperature judging unit  83 , a capability judging unit  85 , a control selecting unit  87 , and a driving control unit  89 . 
     The heat amount information storing unit  71  obtains heat amount information, e.g., processing heat amounts such as a sensible heat capability level and a latent heat processing capability level as well as cooling load information, and supplies the obtained information to the control unit  63 . The temperature information storing unit  73  obtains temperature information, e.g., a blown-out air temperature and a blown-out air temperature target value, and supplies the obtained information to the control unit  63 . 
     The temperature judging unit  83  is configured to determine a higher/lower relationship between the blown-out air temperature controlled by the heat exchanging process performed by the indoor heat exchanger  29  and the blown-out air target temperature set value and to further supply the determination result to the capability judging unit  85 . The capability judging unit  85  is configured to determine the cooling capability of the refrigerant circuit. More specifically, when the temperature judging unit  83  has determined that the higher/lower relationship is present, the capability judging unit  85  determines the higher/lower relationship on the basis of the latent heat capability and a latent heat load and further supplies the result to the control selecting unit  87 . 
     On the basis of the determination result received from the capability judging unit  85 , the control selecting unit  87  is configured to select one from between the superheat degree control to control the degree of superheat and the evaporating temperature control to control the evaporating temperature and to further supply the selection result to the driving control unit  89 . 
     More specifically, the control selecting unit  87  selects the evaporating temperature control, when the temperature judging unit  83  has determined that the blown-out air temperature is lower than the target temperature set value, while the capability judging unit  85  has determined that the latent heat capability is higher than the latent heat load. 
     In other words, when the blown-out air temperature has not reached the target temperature, while the latent heat capability exceeds the latent heat load, since the latent heat capability is satisfied, there will be no possibility that the latent heat capability becomes excessive when control is exercised to raise the evaporating temperature by which the latent heat capability is decreased. Consequently, an appropriate selection is exercising control to raise the evaporating temperature. 
     In contrast, the control selecting unit  87  selects the superheat degree control, when the temperature judging unit  83  has determined that the blown-out air temperature is lower than the target temperature set value, while the capability judging unit  85  has determined that the latent heat capability is equal to or lower than the latent heat load. 
     In other words, when the blown-out air temperature has not reached the target temperature, while the latent heat capability does not exceed the latent heat load, since the latent heat capability is not satisfied, if control were exercised to raise the evaporating temperature by which the latent heat capability would be decreased, the latent heat capability would be insufficient. Consequently, an appropriate selection is exercising control to raise the degree of superheat. 
     As another example, the control selecting unit  87  selects the superheat degree control, when the temperature judging unit  83  has determined that the blown-out air temperature is equal to or higher than the target temperature set value, while the capability judging unit  85  has determined that the latent heat capability is higher than the latent heat load. 
     In other words, when the blown-out air temperature exceeds the target temperature, while the latent heat capability exceeds the latent heat load, since the latent heat capability is satisfied, if control were exercised to lower the evaporating temperature by which the latent heat capability would be increased, the latent heat capability would be excessive. Consequently, an appropriate selection is exercising control to lower the degree of superheat. 
     In contrast, the control selecting unit  87  selects the evaporating temperature control, when the temperature judging unit  83  has determined that the blown-out air temperature is equal to or higher than the target temperature set value, while the capability judging unit  85  has determined that the latent heat capability is equal to or lower than the latent heat load. 
     In other words, when the blown-out air temperature exceeds the target temperature, while the latent heat of the cooling capability is equal to or lower than the latent heat of the cooling load, since the latent heat capability is not satisfied, the latent heat capability will be increased when control is exercised to lower the evaporating temperature by which the latent heat capability is increased. Consequently, an appropriate selection is exercising control to lower the evaporating temperature. 
     The driving control unit  89  is configured to control the frequency of the compressor  21  and the opening degree of the expansion valve  27 , in accordance with the control selected by the control selecting unit  87 . 
     More specifically, when the temperature judging unit  83  has determined that the blown-out air temperature is lower than the target temperature set value, while the capability judging unit  85  has determined that the latent heat capability is higher than the latent heat load, the driving control unit  89  controls the evaporating temperature by controlling the frequency of the compressor  21 . 
     In contrast, when the temperature judging unit  83  has determined that the blown-out air temperature is lower than the target temperature set value, while the capability judging unit  85  has determined that the latent heat capability is equal to or lower than the latent heat load, the driving control unit  89  controls the degree of superheat by controlling the opening degree of the expansion valve  27 . 
     As another example, when the temperature judging unit  83  has determined that the blown-out air temperature is equal to or higher than the target temperature set value, while the capability judging unit  85  has determined that the latent heat capability is higher than the latent heat load, the driving control unit  89  controls the degree of superheat by controlling the opening degree of the expansion valve  27 . 
     In contrast, when the temperature judging unit  83  has determined that the blown-out air temperature is equal to or higher than the target temperature set value, while the capability judging unit  85  has determined that the latent heat capability is equal to or lower than the latent heat load, the driving control unit  89  controls the evaporating temperature by controlling the frequency of the compressor  21 . 
     As yet another example, when it is determined that there is no difference between the blown-out air temperature and the target temperature set value, the driving control unit  89  ends the control selected by the control selecting unit  87 . 
     An Operation According to Embodiment 1 
     Next, an example of the blown-out air temperature control exercised in the air-conditioning apparatus  3  will be explained, with reference to  FIG. 7 .  FIG. 7  is a flowchart for explaining an example of the control exercised in the air-conditioning apparatus  3  according to Embodiment 1 of the present invention. 
     &lt;Step S 11 &gt; 
     The temperature judging unit  83  determines whether or not the difference between the blown-out air temperature and the blown-out air temperature target value is negative. When the difference between the blown-out air temperature and the blown-out air temperature target value is negative, the temperature judging unit  83  proceeds to step S 12 . On the contrary, when the difference between the blown-out air temperature and the blown-out air temperature target value is not negative, the temperature judging unit  83  proceeds to step S 15 . 
     &lt;Step S 12 &gt; 
     The capability judging unit  85  determines whether or not the latent heat capability is higher than the latent heat load. When the latent heat capability is higher than the latent heat load, the capability judging unit  85  proceeds to step S 13 . On the contrary, when the latent heat capability is equal to or lower than the latent heat load, the capability judging unit  85  proceeds to step S 14 . 
     &lt;Step S 13 &gt; 
     The control selecting unit  87  selects the evaporating temperature control. Further, the control selecting unit  87  supplies a control command related to the selected evaporating temperature control, to the driving control unit  89 . On the basis of the control command related to the evaporating temperature control, the driving control unit  89  controls the frequency of the compressor  21 . For example, the driving control unit  89  controls the frequency of the compressor  21 , by employing the compressor frequency adjusting unit  45 . 
     &lt;Step S 14 &gt; 
     The control selecting unit  87  selects the superheat degree control. Accordingly, the control selecting unit  87  supplies a control command related to the selected superheat degree control, to the driving control unit  89 . On the basis of the control command related to the superheat degree control, the driving control unit  89  controls the opening degree of the expansion valve  27 . 
     &lt;Step S 15 &gt; 
     The capability judging unit  85  determines whether or not the latent heat capability is higher than the latent heat load. When the latent heat capability is higher than the latent heat load, the capability judging unit  85  proceeds to step S 16 . On the contrary, when the latent heat capability is equal to or lower than the latent heat load, the capability judging unit  85  proceeds to step S 17 . 
     &lt;Step S 16 &gt; 
     The control selecting unit  87  selects the superheat degree control. Accordingly, the control selecting unit  87  supplies a control command related to the selected superheat degree control to the driving control unit  89 . The driving control unit  89  controls the opening degree of the expansion valve  27 , on the basis of the control command related to the superheat degree control. 
     &lt;Step S 17 &gt; 
     The control selecting unit  87  selects the evaporating temperature control. Further, the control selecting unit  87  supplies a control command related to the selected evaporating temperature control to the driving control unit  89 . The driving control unit  89  controls the frequency of the compressor  21 , on the basis of the control command related to the evaporating temperature control. For example, the driving control unit  89  controls the frequency of the compressor  21  by employing the compressor frequency adjusting unit  45 . 
     &lt;Step S 18 &gt; 
     The temperature judging unit  83  determines whether or not the blown-out air temperature is satisfied. When the blown-out air temperature is satisfied, the temperature judging unit  83  ends the process. On the contrary, when the blown-out air temperature is not satisfied, the temperature judging unit  83  returns to step S 11 . Alternatively, in consideration of responsiveness of the refrigerant circuit, the temperature judging unit  83  may determine the temperature when a predetermined time period has elapsed, instead of immediately after the control selected from between the evaporating temperature control and the superheat degree control is exercised. 
     Advantageous Effects of Embodiment 1 
     As explained above, according to Embodiment 1, the air-conditioning apparatus  3  is configured to select one from between the superheat degree control and the evaporating temperature control, on the basis of the latent heat capability. More specifically, by exercising the control based on the latent heat capability, when the latent heat capability is insufficient, the air-conditioning apparatus  3  exercises control so that the latent heat will not further be decreased from the current level or so that the latent heat can be increased. Further, by exercising the control based on the latent heat capability, when the latent heat capability is excessive, the air-conditioning apparatus  3  exercises control so that the latent heat will not further be increased from the current level or so that the latent heat can be decreased. Accordingly, the air-conditioning apparatus  3  is able to avoid the situation where the latent heat capability is insufficient. Consequently, the air-conditioning apparatus  3  is able to realize the control over the blown-out air temperature with high energy efficiency. 
     Further, when exercising the control to raise the evaporating temperature, the air-conditioning apparatus  3  is capable of improving the COP. Consequently, the air-conditioning apparatus  3  is also capable of exercising energy-saving control. 
     Embodiment 2 
     A Configuration of Embodiment 2 
       FIG. 8  is a diagram illustrating an example of a functional configuration of the control unit  63  according to Embodiment 2 of the present invention. In Embodiment 2, the items that are not particularly noted are the same as those in Embodiment 1. The same functions and configurations will be referred to by using the same reference characters. As illustrated in  FIG. 8 , the control unit  63  further includes a cooling capability judging unit  81 . 
     The cooling capability judging unit  81  is configured to determine a higher/lower relationship between the cooling capability and the cooling load and to further supply the determination result to one selected from between the temperature judging unit  83  and the driving control unit  89  in accordance with the determination result. More specifically, when the cooling capability is lower than the cooling load, the cooling capability judging unit  81  causes the driving control unit  89  to exercise control so that the cooling capability stops being lower than the cooling load. On the contrary, when the cooling capability is not lower than the cooling load, the cooling capability judging unit  81  causes the temperature judging unit  83  to determine the higher/lower relationship between the blown-out air temperature and the blown-out air temperature target value and further causes the capability judging unit  85  to determine whether or not the latent heat capability has a processing heat amount to process the cooling load. In this situation, the cooling load and the cooling capability each correspond to a processing heat amount of the total heat. 
     An Operation According to Embodiment 2 
       FIG. 9  is a flowchart for explaining an example of the control exercised in the air-conditioning apparatus  3  according to Embodiment 2 of the present invention. In the following sections, differences from Embodiment 1 will be explained, and the explanation of the other operations will be omitted. In other words, the processes performed at steps S 33  to S 40  in  FIG. 9  are the same as the processes performed at steps S 11  to S 18  in  FIG. 7 . 
     &lt;Step S 31 &gt; 
     The cooling capability judging unit  81  determines whether or not the cooling capability is lower than the cooling load. When the cooling capability is lower than the cooling load, the cooling capability judging unit  81  proceeds to step S 32 . On the contrary, when the cooling capability is not lower than the cooling load, the cooling capability judging unit  81  performs the operations performed at the temperature judging unit  83  and thereafter. 
     &lt;Step S 32 &gt; 
     The driving control unit  89  performs an air-conditioning operation in such a manner that the cooling capability does not become lower than the cooling load, and the process returns to step S 31 . 
     Advantageous Effects of Embodiment 2 
     As explained above, according to Embodiment 2, the air-conditioning apparatus  3  is configured to compare the higher/lower relationship between the load and the capability with respect to the processing heat amount of the total heat, before proceeding to the latent heat capability determining process and to further perform the operations in accordance with the comparison result. Accordingly, the air-conditioning apparatus  3  is able to perform the process of determining the latent heat capability in the state where the air-conditioned space has been controlled to some extent. Thus, it is possible to enhance the level of precision of the latent heat capability judging process. Further, since the air-conditioning apparatus  3  operates in such a manner that the cooling capability does not become lower than the cooling load, i.e., in such a manner that the cooling capability is kept equal to or higher than the cooling load, the air-conditioning apparatus  3  is able to guarantee comfortability. 
     Embodiment 3 
     A Configuration of Embodiment 3 
       FIG. 10  is a diagram illustrating an example of a functional configuration of the control unit  63  according to Embodiment 3 of the present invention. In Embodiment 3, the items that are not particularly noted are the same as those in Embodiments 1 and 2. The same functions and configurations will be referred to by using the same reference characters. 
     The capability judging unit  85  illustrated in  FIG. 10  is configured to determine the processing heat amount by making a comparison of sensible heat factors. More specifically, the capability judging unit  85  determines whether or not the refrigerant circuit has a processing heat amount to process the cooling load, on the basis of a sensible heat factor of the cooling capability and a sensible heat factor of the cooling load. In this situation, the sensible heat factor is a ratio of the sensible heat to the total heat. 
     Next, a relationship between a comparison using the sensible heat factor and a comparison using the latent heat will be explained. As explained above, as the sensible heat factor of the cooling capability increases, the ratio of the latent heat capability to the cooling capability decreases. On the contrary, as the sensible heat factor of the cooling capability decreases, the ratio of the latent heat capability to the cooling capability increases. Accordingly, by taking the sensible heat factor of the cooling capability into consideration, it is possible to exercise control while taking the ratio of the latent heat capability into consideration. Next, a specific example of the control will be explained. 
     An example will be explained in which the blown-out air temperature is lower than the blown-out air temperature target value, while the sensible heat factor of the cooling capability is lower than the sensible heat factor of the cooling load. When the sensible heat factor of the cooling capability is lower than the sensible heat factor of the cooling load, it means that the latent heat capability is higher than the latent heat load. Accordingly, in that situation, there will be no possibility that the latent heat capability becomes excessive when control is exercised to raise the evaporating temperature by which the latent heat capability is decreased. Consequently, in that situation, an appropriate selection is exercising control to raise the evaporating temperature, to raise the blown-out air temperature to reach the blown-out air temperature target value. 
     Next, an example will be explained in which the blown-out air temperature is lower than the blown-out air temperature target value, while the sensible heat factor of the cooling capability is equal to or higher than the sensible heat factor of the cooling load. When the sensible heat factor of the cooling capability is equal to or higher than the sensible heat factor of the cooling load, it means that the latent heat capability is equal to or lower than the latent heat load. Accordingly, in that situation, if control were exercised to raise the evaporating temperature by which the latent heat capability would be decreased, the latent heat capability would be insufficient. Consequently, in that situation, an appropriate selection is exercising control to raise the degree of superheat, to raise the blown-out air temperature to reach the blown-out air temperature target value. 
     Next, an example will be explained in which the blown-out air temperature is equal to or higher than the blown-out air temperature target value, while the sensible heat factor of the cooling capability is lower than the sensible heat factor of the cooling load. When the sensible heat factor of the cooling capability is lower than the sensible heat factor of the cooling load, it means that the latent heat capability is higher than the latent heat load. Accordingly, in that situation, if control were exercised to lower the evaporating temperature by which the latent heat processing capability would be increased, the latent heat capability would be excessive. Consequently, in that situation, an appropriate selection is exercising control to lower the degree of superheat, to lower the blown-out air temperature to reach the blown-out air temperature target value. 
     Next, an example will be explained in which the blown-out air temperature is equal to or higher than the blown-out air temperature target value, while the sensible heat factor of the cooling capability is equal to or higher than the sensible heat factor of the cooling load. When the sensible heat factor of the cooling capability is equal to or higher than the sensible heat factor of the cooling load, it means that the latent heat capability is equal to or lower than the latent heat load. Accordingly, in that situation, the latent heat capability will increase when control is exercised to lower the evaporating temperature by which the latent heat processing capability is increased. Consequently, in that situation, an appropriate selection is exercising control to lower the evaporating temperature, to lower the blown-out air temperature to reach the blown-out air temperature target value. 
     An Operation According to Embodiment 3 
       FIG. 11  is a flowchart for explaining an example of the control exercised in the air-conditioning apparatus  3  according to Embodiment 3 of the present invention. Operations that are different from those in Embodiments 1 and 2 will be explained, and the explanations of the other operations will be omitted. In other words, the processes performed at steps S 51  to S 53  and S 61  in  FIG. 11  are the same as the processes performed at steps S 31  to S 33  and S 40  in  FIG. 9 . 
     &lt;Step S 54 &gt; 
     The capability judging unit  85  determines whether or not the sensible heat factor of the cooling capability is lower than the sensible heat factor of the cooling load. When the sensible heat factor of the cooling capability is lower than the sensible heat factor of the cooling load, the capability judging unit  85  proceeds to step S 55 . On the contrary, when the sensible heat factor of the cooling capability is equal to or higher than the sensible heat factor of the cooling load, the capability judging unit  85  proceeds to step S 56 . 
     &lt;Step S 55 &gt; 
     After the control selecting unit  87  has selected the evaporating temperature control, the driving control unit  89  raises the evaporating temperature. 
     &lt;Step S 56 &gt; 
     After the control selecting unit  87  has selected the evaporating temperature control, the driving control unit  89  lowers the evaporating temperature until the sensible heat factor of the cooling capability becomes equal to the sensible heat factor of the cooling load by cooperating with the capability judging unit  85 . As a result, the latent heat of the cooling capability increases, so that the state where the latent heat processing capability satisfies a processing heat amount to process the cooling load is achieved. 
     &lt;Step S 57 &gt; 
     After the control selecting unit  87  has selected the superheat degree control, the driving control unit  89  raises the degree of superheat. 
     &lt;Step S 58 &gt; 
     The capability judging unit  85  determines whether or not the sensible heat factor of the cooling capability is lower than the sensible heat factor of the cooling load. When the sensible heat factor of the cooling capability is lower than the sensible heat factor of the cooling load, the capability judging unit  85  proceeds to step S 59 . On the contrary, when the sensible heat factor of the cooling capability is equal to or higher than the sensible heat factor of the cooling load, the capability judging unit  85  proceeds to step S 60 . 
     &lt;Step S 59 &gt; 
     After the control selecting unit  87  has selected the superheat degree control, the driving control unit  89  lowers the degree of superheat. 
     &lt;Step S 60 &gt; 
     After the control selecting unit  87  has selected the evaporating temperature control, the driving control unit  89  lowers the evaporating temperature. 
     Advantageous Effects of Embodiment 3 
     As explained above, according to Embodiment 3, the air-conditioning apparatus  3  is configured to select one from between the superheat degree control and the evaporating temperature control on the basis of the sensible heat factors. More specifically, by exercising the control based on the sensible heat factors, when the latent heat capability is insufficient, the air-conditioning apparatus  3  exercises control so that the latent heat will not further be decreased from the current level or so that the latent heat can be increased. Also, by exercising the control based on the sensible heat factors, when the latent heat capability is excessive, the air-conditioning apparatus  3  exercises control so that the latent heat will not further be increased from the current level or so that the latent heat can be decreased. Accordingly, the air-conditioning apparatus  3  is able to avoid the situation where the latent heat capability is insufficient. Consequently, the air-conditioning apparatus  3  is able to realize the control over the blown-out air temperature with high energy efficiency. In addition, since the air-conditioning apparatus  3  operates in such a manner that the cooling capability does not become lower than the cooling load, i.e., in such a manner that the cooling capability is kept equal to or higher than the cooling load, the air-conditioning apparatus  3  is able to guarantee comfortability. 
     Further, when the blown-out air temperature is lower than the blown-out air temperature target value, while the sensible heat factor of the cooling capability is equal to or higher than the sensible heat factor of the cooling load, the air-conditioning apparatus  3  lowers the evaporating temperature until the sensible heat factor of the cooling capability becomes equal to the sensible heat factor of the cooling load. As a result, the air-conditioning apparatus  3  is able to increase the latent heat capability. Consequently, the air-conditioning apparatus  3  is able to avoid the situation where the latent heat capability is insufficient. 
     Embodiment 4 
     A Configuration of Embodiment 4 
       FIG. 12  is a diagram illustrating an example of a functional configuration of the control unit  63  according to Embodiment 4 of the present invention.  FIG. 13  is a chart illustrating an operation concept of hysteresis control according to Embodiment 4 of the present invention. In Embodiment 4, the items that are not particularly noted are the same as those in Embodiments 1 to 3. The same functions and configurations will be referred to by using the same reference characters. 
     The control unit  63  further includes an operation history judging unit  86 . The operation history judging unit  86  is configured to determine the control selected by the control selecting unit  87  and to prevent the situation where the control is switched frequently between the evaporating temperature control and the superheat degree control. 
     More specifically, when having determined that an operation to lower the degree of superheat is performed during the superheat degree control selected by the control selecting unit  87 , the operation history judging unit  86  causes the control selecting unit  87  to exercise the superheat degree control so as to raise the degree of superheat. 
     In contrast, when having determined that an operation to raise the evaporating temperature is performed during the evaporating temperature control selected by the control selecting unit  87 , the operation history judging unit  86  causes the control selecting unit  87  to exercise the evaporating temperature control so as to lower the evaporating temperature. 
     As illustrated in  FIG. 13 , for example, the operation history judging unit  86  has a reference value and a tolerance range ±δ for the reference value. In other words, when the superheat degree control is being exercised, the operation history judging unit  86  keeps the superheat degree control exercised, as long as the value falls in the range “reference value ±δ”. Similarly, when the evaporating temperature control is being exercised, the operation history judging unit  86  keeps the evaporating temperature control exercised, as long as the value falls in the range “reference value ±δ”. 
     In other words, when the control selecting unit  87  has selected the superheat degree control, the operation history judging unit  86  keeps the superheat degree control exercised continuously. In contrast, when the control selecting unit  87  has selected the evaporating temperature control, the operation history judging unit  86  keeps the evaporating temperature control exercised continuously. 
     An Operation According to Embodiment 4 
       FIG. 14  is a flowchart for explaining an example of the control exercised in the air-conditioning apparatus  3  according to Embodiment 4 of the present invention. Explanations of some of the operations that are the same as those in Embodiments 1 to 3 will be omitted. In other words, the processes performed at steps S 71  to S 74 , S 76 , S 77 , S 79 , and S 81  in  FIG. 14  are the same as the processes performed at steps S 51  to S 54 , S 55 , S 56 , S 58 , and S 59  in  FIG. 11 . 
     &lt;Step S 75 &gt; 
     The operation history judging unit  86  determines whether or not the degree of superheat has been lowered. When the degree of superheat has been lowered, the operation history judging unit  86  proceeds to step S 78 . On the contrary, when the degree of superheat has not been lowered, the operation history judging unit  86  proceeds to step S 76 . 
     &lt;Step S 78 &gt; 
     The operation history judging unit  86  raises the degree of superheat. 
     &lt;Step S 80 &gt; 
     The operation history judging unit  86  determines whether or not the evaporating temperature has been raised. When the evaporating temperature has been raised, the operation history judging unit  86  proceeds to step S 81 . On the contrary, when the evaporating temperature has not been raised, the operation history judging unit  86  proceeds to step S 82 . 
     &lt;Step S 82 &gt; 
     The operation history judging unit  86  lowers the evaporating temperature. 
     &lt;Step S 83 &gt; 
     The temperature judging unit  83  determines whether or not the blown-out air temperature has become equal to the blown-out air temperature target value. When the blown-out air temperature has become equal to the blown-out air temperature target value, the temperature judging unit  83  ends the process. On the contrary, when the blown-out air temperature has not become equal to the blown-out air temperature target value, the temperature judging unit  83  returns to step S 71 . 
     Advantageous Effects of Embodiment 4 
     As explained above, according to Embodiment 4, the air-conditioning apparatus  3  is configured to keep exercising control by using the same control method as previously used, as long as the value falls in the range “the reference value ±δ”. In other words, by incorporating hysteresis into the control methods such as the evaporating temperature control and the superheat degree control, the air-conditioning apparatus  3  is able to avoid the situation where the control method is switched frequently. 
     Embodiment 5 
     A Configuration of Embodiment 5 
       FIG. 15  is a diagram of an example of a functional configuration of the control unit  63  according to Embodiment 5 of the present invention. In Embodiment 5, the items that are not particularly noted are the same as those in Embodiments 1 to 4. The same functions and configurations will be referred to by using the same reference characters. 
     As illustrated in  FIG. 15 , the setting unit  61  further includes a humidity information storing unit  75 . The humidity information storing unit  75  is configured, for example, to obtain an absolute humidity value of the indoor air and a target absolute humidity set value of the indoor air and to further supply the two values to the control unit  63 . When the temperature judging unit  83  has determined that the higher/lower relationship is present, the capability judging unit  85  in  FIG. 15  judges whether or not the refrigerant circuit has a processing heat amount to process the cooling load required when causing the absolute humidity value of the indoor air to reach the target absolute humidity set value of the indoor air, on the basis of the absolute humidity value of the indoor air and the target absolute humidity set value of the indoor air. 
     More specifically, when the temperature judging unit  83  has determined that the blown-out air temperature is lower than the target temperature set value, while the capability judging unit  85  has determined that the refrigerant circuit has a processing heat amount to process the cooling load, the control selecting unit  87  selects the evaporating temperature control. 
     In contrast, when the temperature judging unit  83  has determined that the blown-out air temperature is lower than the target temperature set value, while the capability judging unit  85  has determined that the refrigerant circuit does not have a processing heat amount to process the cooling load, the control selecting unit  87  selects the evaporating temperature control to lower the evaporating temperature until there is no longer a difference between the absolute humidity value of the indoor air and the absolute humidity target value of the indoor air and subsequently selects the superheat degree control. As a result, since the absolute humidity value of the indoor air becomes equal to the absolute humidity target value of the indoor air, the control unit  63  is now in the state where a latent heat processing capability is available. 
     As another example, when the temperature judging unit  83  has determined that the blown-out air temperature is equal to or higher than the target temperature set value, while the capability judging unit  85  has determined that the refrigerant circuit has a processing heat amount to process the cooling load, the control selecting unit  87  selects the superheat degree control. 
     In contrast, when the temperature judging unit  83  has determined that the blown-out air temperature is equal to or higher than the target temperature set value, while the capability judging unit  85  has determined that the refrigerant circuit does not have a processing heat amount to process the cooling load, the control selecting unit  87  selects the evaporating temperature control. 
     An Operation According to Embodiment 5 
       FIG. 16  is a flowchart for explaining an example of the control exercised in the air-conditioning apparatus  3  according to Embodiment 5 of the present invention. Explanations of some of the operations that are the same as those in Embodiments 1 to 4 will be omitted. In other words, the processes performed at steps S 71  to S 73 , S 75 , S 77 , and S 79  to S 81  in  FIG. 16  are the same as the processes performed at steps S 51  to S 53 , S 55 , S 57 , and S 59  to S 61  in  FIG. 11 . 
     &lt;Step S 74 &gt; 
     The capability judging unit  85  determines whether or not the target absolute humidity set value of the indoor air is equal to or higher than the absolute humidity value of the indoor air. When the target absolute humidity set value of the indoor air is equal to or higher than the absolute humidity value of the indoor air, the capability judging unit  85  proceeds to step S 75 . On the contrary, when the target absolute humidity set value of the indoor air is not equal to or higher than the absolute humidity value of the indoor air, the capability judging unit  85  proceeds to step S 76 . 
     &lt;Step S 76 &gt; 
     In cooperation with the capability judging unit  85 , the driving control unit  89  lowers the evaporating temperature until the absolute humidity value of the indoor air becomes equal to the absolute humidity target value of the indoor air. 
     &lt;Step S 78 &gt; 
     The capability judging unit  85  determines whether or not the target absolute humidity set value of the indoor air is equal to or higher than the absolute humidity value of the indoor air. When the target absolute humidity set value of the indoor air is equal to or higher than the absolute humidity value of the indoor air, the capability judging unit  85  proceeds to step S 79 . On the contrary, when the target absolute humidity set value of the indoor air is not equal to or higher than the absolute humidity value of the indoor air, the capability judging unit  85  proceeds to step S 80 . 
     Advantageous Effects of Embodiment 5 
     As explained above, according Embodiment 5, the air-conditioning apparatus  3  is configured to select one from between the superheat degree control and the evaporating temperature control on the basis of the absolute humidity value. More specifically, by exercising the control based on the absolute humidity value, when the latent heat capability is insufficient, the air-conditioning apparatus  3  exercises control so that the latent heat will not further be decreased from the current level or so that the latent heat can be increased. In contrast, by exercising the control based on the absolute humidity value, when the latent heat capability is excessive, the air-conditioning apparatus  3  exercises control so that the latent heat will not further be increased from the current level or so that the latent heat can be decreased. Accordingly, the air-conditioning apparatus  3  is able to avoid the situation where the latent heat capability is insufficient. Consequently, the air-conditioning apparatus  3  is able to realize the control over the blown-out air temperature with high energy efficiency. In addition, since the air-conditioning apparatus  3  operates in such a manner that the cooling capability does not become lower than the cooling load, i.e., in such a manner that the cooling capability is kept equal to or higher than the cooling load, the air-conditioning apparatus  3  is able to guarantee comfortability. 
     Furthermore, when the blown-out air temperature is lower than the blown-out air temperature target value, while the target absolute humidity set value of the indoor air is not equal to or higher than the absolute humidity value of the indoor air, the air-conditioning apparatus  3  lowers the evaporating temperature until the absolute humidity value of the indoor air becomes equal to the absolute humidity target value of the indoor air. As a result, the air-conditioning apparatus  3  is able to avoid the situation where the latent heat capability is insufficient. 
     Embodiment 6 
     A Configuration of Embodiment 6 
       FIG. 17  is a diagram of an example of a functional configuration of the control unit  63  according to Embodiment 6 of the present invention. In Embodiment 6, the items that are not particularly noted are the same as those in Embodiments 1 to 5. The same functions and configurations will be referred to by using the same reference characters. 
     The control unit  63  further includes a limit value judging unit  101 . The limit value judging unit  101  is configured to determine a limit value of the evaporating temperature and a limit value of the degree of superheat. 
     More specifically, when the temperature judging unit  83  has determined that the difference between the blown-out air temperature and the target temperature set value exceeds a predetermined value, while the evaporating temperature observed after an operation under the evaporating temperature control has reached the limit value of the evaporating temperature, the limit value judging unit  101  causes the control selecting unit  87  to select the superheat degree control. 
     In contrast, when the temperature judging unit  83  has determined that the difference between the blown-out air temperature and the target temperature set value exceeds the predetermined value, while the degree of superheat observed after an operation under the superheat degree control has reached the limit value of the degree of superheat, the limit value judging unit  101  causes the control selecting unit  87  to select the evaporating temperature control. 
       FIG. 18  is a flowchart for explaining an example of the control exercised in the air-conditioning apparatus  3  according to Embodiment 6 of the present invention. Explanations of some of the operations that are the same as those in Embodiments 1 to 5 will be omitted. In other words, the processes performed at steps S 91  to S 97  in  FIG. 18  are the same as the processes performed at steps S 53  to S 55  and S 57  to S 60  in  FIG. 11 . 
     &lt;Step S 98 &gt; 
     The temperature judging unit  83  determines whether or not the blown-out air temperature has become equal to the blown-out air temperature target value. When the blown-out air temperature has become equal to the blown-out air temperature target value, the temperature judging unit  83  ends the process. On the contrary, when the blown-out air temperature has not become equal to the blown-out air temperature target value, the temperature judging unit  83  proceeds to step S 99 . 
     &lt;Step S 99 &gt; 
     The limit value judging unit  101  determines whether or not the evaporating temperature control has been selected. When the evaporating temperature control has been selected, the limit value judging unit  101  proceeds to step S 100 . On the contrary, when the evaporating temperature control has not been selected, the limit value judging unit  101  proceeds to step S 102 . 
     &lt;Step S 100 &gt; 
     The limit value judging unit  101  determines whether or not the limit value of the evaporating temperature has been reached. When the limit value of the evaporating temperature has been reached, the limit value judging unit  101  proceeds to step S 101 . On the contrary, when the limit value of the evaporating temperature has not been reached, the limit value judging unit  101  returns to step S 91 . 
     &lt;Step S 101 &gt; 
     The limit value judging unit  101  causes the control selecting unit  87  to select the superheat degree control. The driving control unit  89  controls the degree of superheat, and the process returns to step S 91 . 
     &lt;Step S 102 &gt; 
     The limit value judging unit  101  determines whether or not the superheat degree control has been selected. When the superheat degree control has been selected, the limit value judging unit  101  proceeds to step S 103 . On the contrary, when the superheat degree control has not been selected, the limit value judging unit  101  returns to step S 91 . 
     &lt;Step S 103 &gt; 
     The limit value judging unit  101  determines whether or not the limit value of the degree of superheat has been reached. When the limit value of the degree of superheat has been reached, the limit value judging unit  101  proceeds to step S 104 . On the contrary, when the limit value of the degree of superheat has not been reached, the limit value judging unit  101  returns to step S 91 . 
     &lt;Step S 104 &gt; 
     The limit value judging unit  101  causes the control selecting unit  87  to select the evaporating temperature control. The driving control unit  89  controls the evaporating temperature, and the process returns to step S 91 . 
     Advantageous Effects of Embodiment 6 
     As explained above, according to Embodiment 6, the air-conditioning apparatus  3  is able to switch the control method into the superheat degree control even when the evaporating temperature has reached the limit value of the control range. Further, the air-conditioning apparatus  3  is able to switch the control method into the evaporating temperature control even when the degree of superheat has reached the limit value of the control range. Accordingly, the air-conditioning apparatus  3  is able to arrange the blown-out air temperature to be close to the blown-out air temperature target value, while taking into consideration the processing heat amount with which the refrigerant circuit processes the cooling load. 
     Embodiment 7 
     A Configuration of Embodiment 7 
       FIG. 19  is a diagram of an example of a schematic configuration of an air-conditioning system  1  according to Embodiment 7 of the present invention. In Embodiment 7, the items that are not particularly noted are the same as those in Embodiments 1 to 6. The same functions and configurations will be referred to by using the same reference characters. 
     The air-conditioning system  1  includes a storing unit  111 , a heat load predicting unit  113 , a controller  115 , and a plurality of air-conditioning apparatuses  3  and is configured to select, for the entire system, one from between the superheat degree control and the evaporating temperature control on the basis of the latent heat capability. 
     The storing unit  111  is configured to store therein, for example, data related to environmental conditions and operation data from a past period (hereinafter, “the past”). The environmental conditions are related to the air-conditioned spaces of the air-conditioning apparatuses  3  and may include, for example, set values and measured values such as an envelope performance of the building, the weather, the number of people who are present in the room, and the temperature and humidity of the indoor air. The operation data from the past denotes operation data from the past of the air-conditioning apparatuses  3  that are put under the control of the controller  115  and operation data from the past of an air-conditioning apparatus that is not put under the control of the controller  115  but is provided in an air-conditioned space similar to that of the air-conditioning apparatuses  3  put under the control of the controller  115 . In other words, the operation data from the past includes the operation data from the past of the air-conditioning apparatuses  3  and the operation data from the past of an air-conditioning apparatus  3  that is different from the air-conditioning apparatuses  3 . 
     In other words, the data stored in the storing unit  111  is data to be used for calculating sensible heat factors and other values. For example, an outdoor air total heat load, an outdoor air sensible heat load, an indoor total heat load, an indoor sensible heat load, a heat transmission load, the number of people who are present in the room, and an air volume of ventilation are used for calculating the sensible heat factors and other values. 
     On the basis of the information stored in the storing unit  111 , the heat load predicting unit  113  is configured to calculate, for example, a cooling load, a cooling capability, a sensible heat factor of the cooling load, and a sensible heat factor of the cooling capability and to further supply the calculation results to the controller  115 . As explained above, the sensible heat factor is a ratio of the sensible heat to the total heat. For example, “Lc” denotes a cooling load with respect to the total heat and the unit thereof is kW. Further, “Cc” denotes a cooling capability with respect to the total heat, and the unit thereof is kW. Also, “SHF_L” denotes a sensible heat factor of the cooling load and is calculated as “a sensible heat load/a total heat load” and thus requires no unit of measurement. Further, “SHF_C” denotes a sensible heat factor of the cooling capability and is calculated as “a sensible heat capability/a total heat capability” and thus requires no unit of measurement. In the following sections, “Lc” will be referred to as a cooling load, “Cc” will be referred to as a cooling capability, “SHF_L” will be referred to as a sensible heat factor of the cooling load, and “SHF_C” will be referred to as a sensible heat factor of the cooling capability. 
     On the basis of information that is related to the cooling capability and is supplied from the heat load predicting unit  113 , the controller  115  is configured to control the plurality of air-conditioning apparatuses  3  put under the control thereof. More specifically, in accordance with a control command from the controller  115 , the air-conditioning apparatuses  3  exercise control based on the latent heat capability to exercise control so that, when the latent heat capability is insufficient, the latent heat will not further be decreased from the current level or the latent heat can be increased. Further, in accordance with a control command from the controller  115 , the air-conditioning apparatuses  3  exercise control based on the latent heat capability to exercise control so that, when the latent heat capability is excessive, the latent heat will not further be increased from the current level or the latent heat can be decreased. 
     Advantageous Effects of Embodiment 7 
     Accordingly, the air-conditioning apparatuses  3  are able to avoid the situation where the latent heat capability is insufficient, in accordance with the control commands from the controller  115 . Consequently, the air-conditioning apparatuses  3  are able to realize the control over the blown-out air temperature with high energy efficiency, in accordance with the control commands from the controller  115 . 
     In this situation, the location where the heat load predicting unit  113  is materialized is not particularly limited. For example, the heat load predicting unit  113  may be provided in a server such as a system management apparatus (not illustrated) or may be provided in the controller  115  disposed on the subordinate side of a server. 
     A Summary of Embodiments 1 to 7 
     In the air-conditioning apparatus  3 , the control unit  63  is configured to select one from between the superheat degree control and the evaporating temperature control, on the basis of the latent heat capability. Further, the functional configuration of the control unit  63  may be structured by causing a computer program to be executed by hardware such as a microcomputer, a computer, or any other device. Further, the functional configuration of the heat load predicting unit  113  may similarly be structured by causing a computer program to be executed by hardware such as a microcomputer, a computer, or any other device. In other words, the environment in which the operations described above are materialized is not particularly limited. 
     Further, the flow path of the refrigerant circuit explained above is merely an example and is not particularly limited. For instance, the refrigerant circuit may include a flow path having a reservoir. 
     REFERENCE SIGNS LIST 
       1  air-conditioning system  3  air-conditioning apparatus  9  refrigerant pipe  11  outdoor unit  13  indoor unit  21  compressor  23  four-way valve 
       25  outdoor heat exchanger  27  expansion valve  29  indoor heat exchanger  31  outdoor fan  33  indoor fan  41  intake-air temperature/humidity detecting unit  43  evaporating temperature detecting unit  45  compressor frequency adjusting unit  61  setting unit  63  control unit  71  heat amount information storing unit  73  temperature information storing unit  75  humidity information storing unit  81  cooling capability judging unit  83  temperature judging unit  85  capability judging unit  86  operation history judging unit  87  control selecting unit  89  driving control unit  101  limit value judging unit  111  storing unit  113  heat load predicting unit  115  controller.