Abstract: Provided are an air conditioning plant control method by which an air conditioning plant can be operated in a most desirable state, and an air conditioning plant so controlled. An air conditioning plant is controlled, which has at least one air conditioner, a refrigerating machine supplying cold water to the air conditioner and a cooling tower supplying cooling water to the refrigerating machine. Within an extent satisfying set conditions of air conditioning, setpoints of the draft temperature of the at least one air conditioner, the cold water temperature of the refrigerating machine and the temperature of cooling water from the cooling tower are altered and optimized so as to minimize energy consumption, operating cost or carbon dioxide emission of the air conditioning plant.

Abstract: Provided are an air conditioning plant control method by which an air conditioning plant can be operated in a most desirable state, and an air conditioning plant so controlled. An air conditioning plant is controlled, which has at least one air conditioner, a refrigerating machine supplying cold water to the air conditioner and a cooling tower supplying cooling water to the refrigerating machine. Within an extent satisfying set conditions of air conditioning, setpoints of the draft temperature of the at least one air conditioner, the cold water temperature of the refrigerating machine and the temperature of cooling water from the cooling tower are altered and optimized so as to minimize energy consumption, operating cost or carbon dioxide emission of the air conditioning plant.

Abstract: An LED display unit comprises a printed circuit board. A plurality of LEDs are packaged on the printed circuit board. Portions of the respective LEDs except for light emitting sections thereof are sealed by a resin. The LEDs having the portions thereof sealed by the resin are received in a case. A plurality of the cases are arranged on the attaching plate, to form a large-sized display panel. The case has a rear face thereof which is brought to a configuration in which spaces exist between the attaching plate and portions of the case except for a fixing portion thereof to the attaching plate and a connector for wiring.

Abstract: By extracting hydrogen fluoride from 2,2,3,3-tetrafluorooxetane with a halogenated hydrocarbon, a mixture of 2,2,3,2-tetrafluorooxetane and the halogenated hydrocarbon containing a small amount of hydrogen fluoride is obtained. The mixture may be distilled at least twice to obtain a mixture of 2,2,3,2-tetrafluorooxetane and the halogenated hydrocarbon containing substantially no hydrogen fluoride.