Thereby, as illustrated in for example time range B at the center of the figure, the number of revolutions of the supply fan 12 (supplied air volume Fsa) increases (FIG. 3C) and thereby return air temperature Tra becomes lower than setting value STRA (FIG. 3A). This means that excessive cold air is supplied to the server apparatuses 2, whereas this does not mean lack of cooling and is not particularly problematic. Also, this excessive supply is temporary, and thus is not particularly problematic in view of the energy saving.
Note that regarding differential pressure value ΔP in time range B, it is also possible to employ a configuration in which ΔP≈ΔSP is kept almost all during time range B for example in addition to the example illustrated in FIG. 3B and ΔP≥ΔSP is satisfied at the last timing in time range B, and thereby the same control mode (execution mode in step S14) as in time range A is used again in time range C.
The features of indirect outside air air-conditioning devices based on a conventional method, the present method, etc. are illustrated in FIG. 4A. They are estimated values based on calculations. FIG. 4B through FIG. 4D illustrate graphs of such features.
