Abstract
Electromagnetic valves in air conditioning units generate an excitation force that gives rise to pipe vibration. Pipe stress caused by this excitation force should be evaluated at the design stage to determine an appropriate piping structure. We conducted an experiment in which we released compressed air from the electromagnetic valve and measured the excitation force generated using a load cell. We focused our attention on fluid-step excitation force and we clarified its magnitude, application point and application direction. We proposed a formula for computing the magnitude of the step force and showed how this formula could be used to determine the excitation force. We conducted an experiment using refrigerant-circulating equipment to determine whether this computational formula for excitation force could be applied to refrigerant used in actual equipment. We indirectly measured excitation force using a differential-pressure gauge and flow meter and demonstrated that the formula was also valid for actual refrigerant.
