Decoupling the Design of Variable Air Volume Systems by Tuning the Tolerances of the DPs

An important discussion on the application of the Axiomatic Design Theory (ADT) is how to address coupled designs. Coupled designs are somewhat usual in engineering and call for solutions in the field of ADT. This paper addresses a class of designs where one or more functional requirements can be fulfilled by design parameters of the type "the higher the better". A good example of this kind of designs is one of the most widespread types of air conditioning systems for office applications: the variable air volume (VAV) system. A VAV system controls the air temperature of multiple rooms by adjusting the flow of cooled air that is supplied by the VAV box that serves each room of the office. The essential functional requirements (FRs) of any modern air conditioning system are: "to control the air temperature", and "to provide indoor air quality (IAQ)" to each served room. The drawback of the VAV systems is that the renewal of the stale air depends on the heat loading of all the rooms, which makes it a coupled design. This paper shows how this coupled design can be decoupled by using a design parameter (the outdoor airflow), which value may be set large enough to fulfil the related functional requirement (the IAQ). The VAV application serves as an example of the application of a new proposed theorem of the ADT that allows decoupling a matrix equation.