One of the main goals in MEP designing engineering for HVAC designers is to enhance energy use efficiency and maintain temperature and air quality. The efficiency of energy use, the quality of air, and comfort in buildings depend on how the heating, cooling, and air distribution system are created. This is why the careful design of ductwork installation is crucial. The method of HVAC systems and ductwork are essential as they guarantee the quality of indoor air thermal comfort and air circulation. When your HVAC equipment and the ducts have not been adequately designed, it may result in inadequate air quality, loss of heat, and create a conditioned area inside the building uncomfortable.
The principal purpose of the design system for ductwork is to ensure that a minimally intrusive channel is created by which warm and cool air can move. If designed correctly, HVAC air distribution systems will play an essential part in preventing loss of heat energy, keeping the indoor Air Quality (IAQ), and ensuring thermal comfort.
To comprehend how ductwork can be developed in a cost-effective, efficient manner, this post describes the design of ductwork. It provides an outline of the process of designing, techniques, and guidelines.
What is Ductwork?
The principle behind the ductwork design is to warm, cool, or ventilate buildings efficiently and cost-effectively. The primary role of ductwork is to construct conduits or passageways which allow air to flow through them to supply cooling, heating, air conditioning, and ventilation (HVAC).
When designing ducts, the basic concepts of airflow need to be comprehended. The return air flows through an air handler unit (AHU), which is then passed through a filter and into the blower. With pressure, it passes through the heat exchanger or coil before being released into the system to supply air. If the ductwork has been designed correctly, it will allow the AHU to create the proper quantity of air via its heat exchanger. In the standard air distribution structure, ducts have to be able to accommodate supply, return and exhale airflow. Supply ducts are used to supply air for ventilation, and air conditioning return ducts regulate mood to ensure IAQ and temperature. Exhaust airflow systems are used to provide air circulation.
To make ductwork design productive, MEP engineering design teams require designers with a background in engineering and mechanical. Design specialists for ductwork and building services engineers should be well-versed in other disciplines, such as civil and structural concepts, to ensure that HVAC systems are free of clashes.
The Ductwork Design Process
The design of ducting systems is easy, provided the specifications are precise and inputs on construction, application, orientation, and construction material are included. Based on the data provided, calculations can be carried out to produce an energy-efficient and non-clash design. In general, distribution and air conditioning systems are constructed to satisfy three essential requirements:
* It must deliver airflow to the locations at a specific rate and speed.
* It must be economical and energy efficient.
* It should offer comfort and not cause disturbing or unwelcome noise.
The design of ductwork begins once architectural layouts and internal design designs are supplied either by the customer or MEP consultants. Building service engineers require specifications, such as the applications, the number of people who will be using the facility, the location of the building, and architectural features to calculate the heat loads and the flow of air. Before carrying any calculations out, single-line drawings are created to show the ductwork’s flow within the building. After approval, the heat load and air flow calculations are carried out. When those calculations are completed and the airflow rates needed are identified, the outlets for air are set. Based on the estimates, specifications, and design layout, the ducting system design layout is created considering the structural and architectural details of the space being conditioned. It conflicts with other construction services like plumbing, electrical (hydraulic), and mechanical systems.
To begin the design process, inputs are necessary regarding the application type and specifications requirements, as well as the orientation of the building, architectural characteristics, and material.
* Type of application Ductwork designs will differ according to the type of use the building will be used for, such as production, data centers, and medical applications, as well as research and comfort-related applications like residential, offices, restaurants, or institutional buildings such as universities and schools.
* Specification requirements –To design a duct that is an efficient design, the designers must determine the kind of work that is planned to be performed as well as the number of people who be using the space. This can help calculate airflow, the velocity and heat load needed to maintain temperature, and IAQ. For comfort settings like restaurants and offices require a different duct layout and airflow than a house.
*Orientation and materials of the building the orientation and type of the building and the materials used play an important role in gauging the absorption of heat, which can help determine the need for cooling and ventilation. The heat absorption rate can be estimated based on whether a structure is facing north, south, east, or west and the location of its geographical position. The material used in construction also influences the degree of heat loss and gain of the structure.
The issues of insufficient inputs or the inability to access required information will be discussed in a forthcoming piece about Ductwork Design Challenges and Recommendations.
Ductwork Design Methods
The ductwork installation design is usually based on project costs, specifications, requirements, and energy efficiency standards. According to the force placed on the duct due to the air pressure, ducts are typically classified into high, medium velocity, and low-speed systems. There are three standard methods of designing ducts:
1. Continuous Velocity Method: This technique, designed to ensure that the velocity is maintained at a minimum, is among the easiest methods of designing duct systems for return and supply air ducts. It is, however, a process that requires some expertise to apply this method, as the wrong selection of velocities and dimensions of ducts and the choice of fixtures can result in a rise in the price. In addition, to ensure the same pressure drop across ducts, the method calls for closing dampers only in the ducts (except index runs) that could impact efficiency.
2. Equal Friction Method – This standard method, employed for both return and supply ducts, ensures the same pressure drop in friction across the branch and central vents. This method lets pressure drop as the conflict occurs in duct ducts rather than in dampers that balance. But, as with the velocity method, dampers are closed only partially is necessary, which can result in noise production.
3. The Static Regain Method is commonly employed for supply systems with long ducts. It is a velocity system that keeps the same static pressure at every terminal or branch. Although this is a balanced system since it does not require tempering, long ducts could impact air distribution in the conditioned areas.
The duct design and construction methods utilized vary from application installation to the performance of the duct system, as well as system balancing and optimization, which must be considered. When an air handler (AHU) is implemented, the system must be balanced and optimized to increase performance. In balancing and optimizing a scenario, the airflow rates of supply outlets and the return air intakes are measured, and fan speed and dampers are set. In large buildings, balancers for air conditioning systems can be costly and time-consuming; however, it is necessary as it can provide benefits that far exceed the cost of setting up the system. Various optimization techniques are employed to reduce operating, and total costs, like the T-Method Optimisation described within the DA3 Application Manual of AIRAH (Australian Institute of Refrigeration Air Conditioning).