T-method duct optimization with Excel

Introduction
Duct design methods are presented in the 1997 ASHRAE Handbook-Fundamentals. Three methods are presented: equal friction, static regain, and the T-method.
As non-optimization-based methods, the equal friction method is widely used for low-pressure system in most buildings. 
The T-method, introduced by Tsal et al. (1988), is the only optimization-based method, described in the 1997 ASHRAE Handbook- Fundamentals. 
I wrote a macro for EXCEL spreadsheet for the calculation of the systems duct with equal friction and T-method.
You can compare the results of the two methods. 
For the definition of the variables used in the Excel sheet see ASHRAE fundamental book.

Rules for numbering of the trunks / branches 
You must enumerate the network hydraulically disadvantaged. The network consists of trunks. In each trunk the air flow rate is constant. It begins with the trunk with great air flow up to the trunk with smaller air flow ( see figure 1 ).
fig.1
fig.1

Subsequently be numbered branches from those that branch off from the trunks to reach higher up than those in the lower reach (see figure 2).
fig.2
fig.2

In addition to number the branches must be inserted in the trunk which they refer ( see figure 3 ).
 
fig.3
   
 BRANCH  TRUNK 
BR1  TR1 
BR2  TR1 
BR3  TR2 
BR4 TR2 
BR5  TR6 
BR6  TR6 
BR7   TR..n-1
BR8  TR..n-1
fig.3

If it is necessary to calculate a network with a T must insert a truncated length equal to the fictitious example to 0.1m (see figure 4). 
fig.4
fig.4

From a branch can not start another branch (see figure 5).
fig.5
fig.5
Excel example figures
For the Excel example i referred to the duct network following (see fig.6).
fig.6
fig.6

References
  1. 2005 ASHRAE Handbook—Fundamentals, Chapter 35 – Duct Design
  2. 2009 ASHRAE Journal – Equal friction sulution for duct sizing - Fred W. Dougherty
  3. 1991 Thesis Oklahoma State University - Computer Aided Optimal Design of Duct Systems - Wang, F.
  4. 1988 ASHRAE Transactions n.3154, T-METHOD DUCT DESIGN, PART I: OPTIMIZATION THEORY
  5. 1988 ASHRAE Transactions n.3155, T-METHOD DUCT DESIGN, PART II: CALCULATION PROCEDURE AND ECONOMIC ANALYSIS

Pagine secondarie (1): Download excel file