Computer-aided design (CAD) package for teaching HVAC design

A series of BASIC language design programs has been developed to demonstrate the concept of computer-aided design and drafting (CADD) as well as teach many aspects of air-conditioning design. Most of these programs are designed to stand alone or to accept input data from an earlier program. The first program requires the user to enter building parameter data, then calculates the cooling load for the ambient conditions given. The airflow for either a dual-duct or a variable-air-volume (VAV) system can be determined. Given these airflows to each zone, the second program sizes and selects both diffusers and VAV boxes for each defined room in the zone. The friction loss in each branch and zone is then computed, along with the duct mains back to the mechanical room. Based on the static pressure and total flow, one or more fans can be selected from a generic set of fan curves in the computer. The computer then produces a bill of materials for the system, a cost estimate for the system, and finally draws a schematic of the ductwork showing diameters and flows to each room.