Duct design calculation

We’re going to focus on the equal friction method in this example as. So we’ll jump straight into designing a system. The first one being the shape of the ductwork.

Ductulator calculats duct dimensions using equal friction method or velocity method. It calculates both rectangular and round duct dimensions. Today we use all that to find out how big the ducts need to be.

The total energy per unit volume of air flowing in a duct system is equal to the sum of the static energy, kinetic energy and potential energy. When applied to airflow in ducts , the flow work or static energy is represented by the static pressure of the air, and the velocity pressure of the air represents the kinetic energy. THREE STEPS TO SIZING AIR DUCTS.

Designing a duct system is important but there are a few critical steps that come first. Because of this, HVAC professionals and amateurs alike typically don’t calculate the final HVAC ducting size by themselves. Therefore the pressure loss is 0. Conduct an accurate sizing calculation for a specific duct using duct friction sheets or the duct slide rule, 2. Size the ducts in the distribution system to ensure that the proper amount of air reaches each room utilizing ACCA’s duct slide rule.

Then, you simply match this friction rate to the desired cfm on a duct calculator to determine the appropriate duct size.

Notice that you have to calculate the friction rate, and that it’s based on the effective length of the duct system. This is not just a number you pull out of your hat. ASHRAE design temperature tables.

These are also located inside the ACCA Manual J. For example, the design temperature for St. Louis, Missouri is 95°F (35°C) for cooling and 2°F (-1°C) for heating. LIMITS Generally, the indoor temperatures are limited only by the type of equipment used and the design of the duct system. Part of this design is calculating duct size.

It delivers an schematic drawing of the duct system including locations and sizes of trunk-lines, branch ducts , outlet registers, an inlet grilles. A Leader in the Industry Through a Commitment to Quality, Service, and Innovation. DUCT DESIGN , LEVEL 1: FUNDAMENTALS Distribution Systems Space Availability The sizing criteria will often be defined by the space available to run the ductwork (Figure 1). To size a flex duct you utilize the same methods as if you were sizing regular HVAC rigid duct. Measure the length and width of the room where the flex duct will be supplying the air.

Multiply the length and width together to get the square footage of the room. Manual-D is ACCA’s duct design method for properly sizing the airflow pathways – the ductwork – within a residential heating and cooling system. Even though this method has been around for many years, it is rarely implemented (and even less-often implemented correctly). The program can calculate using either the static regain, equal friction, or constant velocity methods. Ducts that are not well designed result in discomfort, high energy costs, bad air quality, and increased noise levels.

Choosing the right-sized duct is critical to maintain proper air flow in the system.

Most designers, over a period of time with experience in a spe-cific location, may develop their own quick methods. Design Master HVAC is an integrated HVAC building design and drafting program that runs on top of AutoCAD. Calculate Required Airflow per Room Step 4.