A New Method To Determine Age Of Air Under Less Perfect Conditions

At present, the local mean age of air and the room mean age of air may be measured by three versions of the tracer gas technique, which are the Decay method, the Pulse method and the Step-up method. All of the methods require that the concentration of tracer gas at the supply should be constant during the whole test procedure (Pulse method requires the concentration of tracer gas at the supply should be constant after injection). Thus it needs more equipment to maintain the tracer gas to be constant during the test procedure. Moreover, as we know the most air conditioning system is mixing system, which means the concentration of tracer gas at the supply could not be constant at all. So this experiment cannot be done at all. Facing these problems, the paper deduced new expressions for the local mean age of air and the room mean age of air. And also some cases are used to validate the theory.