As the first detailed case study of conceptual design using the parameter analysis methodology, this chapter presents a relatively simple design example. Only a partial need analysis, highlighting the most important issues, is given here. The discussion under the value category uncovers the importance of keeping the cost down, and this issue also proves to be the dominant parameter in the development of the concept. This case study demonstrates the sequential evolution of the design throughout the parameter analysis process.

The Initial Need

Heating, ventilating, and air conditioning (HVAC) systems in buildings consist of a heating source, a cooling source, a fan to force airflow, and a closed-loop temperature control system. The last-named component usually includes a computer to compare actual temperature readings to set, or desired, values and activate the system accordingly. Such a system can handle the temperature well, but it does not account for the “freshness” of the indoor air. If conditions happen to be such that the temperature does not need to be actively changed by the system for a relatively long period of time, the air may become uncomfortably stale. The need is therefore to design a sensor to measure the airflow in HVAC ducts to allow the control system to monitor the number of air-volume exchanges in the rooms.

Abbreviated Need Analysis

Performance

The sensor needs to tell the computer how much volume of air per unit time passes through the duct.