Proposing an alternative method for the design of air ductworks through coding in EES software

In the design of air ductworks, a permissible velocity for air in the main branch is taken firstly. Then, according to this velocity and flow rate in the main branch, the diameter of the duct and the corresponding head loss are computed. Here, for the rectangular ducts, the dimensions are found taking into account the limitations in the height of the duct. Thereafter, the diameter of the duct (or the dimensions of the rectangular duct) are calculated in other branches according to the flow rate in each branch as well as the head loss in the main branch. Finally, the fan head is obtained based on the head loss in the branches having the highest losses. It is obvious that change in the conditions in accompanied with the repetition of the computations. To remove this shortcoming, in this work, an alternative method is proposed through coding in the EES software. In this method, the branches are input to the code once. Then, with any changes in the conditions, the code is required to be run once more. To demonstrate the suitability of this method, it is utilized here for the design of a typical ductwork. Thereafter, a parametric analysis is undertaken to examine the effects of the duct height as well as the velocity on the main branch on the area of the consumed plate. This analysis is based on the response surface method.