At the moment, one of many important targets in MEP engineering design for HVAC design engineers is to enhance vitality effectivity, preserve air high quality and thermal consolation. Vitality effectivity, air high quality and luxury in a constructing rely upon how heating, cooling and air distribution programs are designed and that is the place cautious ductwork design performs a big position. Ductwork and HVAC system design are necessary because it ensures indoor air high quality, thermal consolation and air flow. If the HVAC system and ducts usually are not designed precisely, it might result in poor air high quality, warmth loss and make the conditioned house within the constructing uncomfortable.
The first perform of the ductwork design system is to make sure a least obtrusive channel is supplied by which cool and heat air can travel. When designed precisely, HVAC air distribution programs will play an necessary position in countering warmth vitality losses, sustaining indoor air high quality (IAQ) and offering thermal consolation.
To grasp how ductwork may be designed in an economical and environment friendly method, this text decodes ductwork design and supplies a short define of the design course of, strategies and requirements.
What’s Ductwork?
The essential precept of ductwork design is to warmth, cool or ventilate a constructing in probably the most environment friendly and cost-effective means. The first perform of ductwork is to design conduits or passages that enable air movement to offer heating, cooling, air flow and air-con (HVAC).
Within the duct design course of, the fundamentals of air movement have to be understood. Return air goes into an air handler unit (AHU), by a filter and into the blower and with pressure it goes by the A coil or warmth exchanger after which it goes out into the availability air system. If the ductwork is designed accurately it allows the AHU to provide the correct amount of air by the warmth exchanger. In a typical air distribution system, ducts should accommodate provide, return and exhaust air movement. Provide ducts present air required for air-con and air flow, return ducts present regulated air to take care of IAQ and temperature and exhaust air movement programs present air flow.
For ductwork design to be environment friendly, MEP engineering design groups have to have designers with a mechanical and engineering background. Ductwork design specialists or constructing service engineers should additionally possess thorough data of different disciplines akin to architectural, civil and structural ideas to make sure HVAC programs are conflict free.
The Ductwork Design Course of
The ducting system design course of is easy, supplied that the specs are clearly talked about and the inputs concerning software, exercise, constructing orientation and constructing materials are supplied. Primarily based on the data supplied calculations may be accomplished to create an energy-efficient and clash-free design. Sometimes, air-con and distribution programs are designed to fulfil three predominant necessities akin to:
• It ought to ship air movement at particular charges and velocity to stipulated areas.
• It needs to be vitality environment friendly and value efficient.
• It ought to present consolation and never generate disturbance or objectionable noise.
The method of ductwork design begins as soon as architectural layouts and inside design plans are supplied by the shopper or MEP consultants. Constructing service engineers then require specification necessities akin to software, the variety of individuals, the orientation of the constructing and architectural traits to make calculations on warmth load and air movement. Earlier than any calculations are carried out, single line drawings are drafted to showcase the movement of ductwork within the constructing. As soon as they’re authorised, calculations for warmth load and air movement are performed. As soon as the warmth load calculations are full, the air movement charges which might be required are recognized and the air retailers are mounted. With the calculations, specs and format, the ducting system design format is then designed considering architectural and structural particulars of the conditioned house and clashes with different constructing services akin to electrical, plumbing (hydraulic) and mechanical services.
To begin the ductwork design course of there are inputs required concerning particulars about the kind of software, specification necessities, constructing orientation, architectural attribute and materials.
• Software kind – Ductwork design will differ based mostly on the kind of software the constructing shall be used for akin to manufacturing, knowledge centres, medical functions, scientific analysis and luxury functions akin to eating places, workplaces, residences, institutional constructing akin to colleges and universities.
• Specification requirement – To create an environment friendly duct design, designers have to know what kind of exercise shall be performed and the common variety of individuals that can use the conditioned house. This may assist in calculating the air movement, velocity and warmth load required to take care of temperatures and IAQ. In consolation functions, as an example, an workplace or restaurant would require totally different duct design and air velocity than a residence.
• Orientation and materials of the constructing – The orientation of constructing and materials used performs a key position in gauging warmth absorption which can assist decide the cooling and air flow necessities. Primarily based on whether or not a constructing faces north, south, east or west, and the place it’s geographically situated, warmth absorption may be calculated. The kind of materials used for development additionally impacts the quantity of warmth achieve and lack of the constructing.
The challenges of incomplete inputs or non-availability of required inputs are mentioned in an upcoming article on Ductwork Design Challenges and Suggestions.
Ductwork Design Strategies
Ductwork design strategies are often decided based mostly on the fee, necessities, specs and vitality effectivity requirements. Primarily based on the load of the duct from air pressure, duct programs can usually be categorized into excessive velocity, medium velocity and low velocity programs. There are three generally used strategies for duct design:
1. Fixed Velocity Technique – This methodology, designed to take care of minimal velocity, is likely one of the easiest methods to design duct programs for provide and return air ducts. Nonetheless, it requires expertise to make use of this methodology as the wrong collection of velocities, duct sizes and selection of fixtures might enhance the fee. Furthermore, to take care of the identical charge of pressure drop in duct runs, this methodology requires partial closure of dampers in duct runs (besides index run) which might have an effect on effectivity.
2. Equal Friction Technique – This typical methodology used for each provide and return ducts maintains the identical frictional pressure drop throughout predominant and department ducts. This methodology ensures dissipation of pressure drops as friction in duct runs relatively than in balancing dampers. Nonetheless, like the rate methodology, partial closure of dampers is required and this might result in noise era.
3. Static Regain Technique – This methodology generally used for big provide programs with lengthy ducts is a excessive velocity system that maintains fixed static pressure earlier than every department or terminal. Whereas this can be a balanced system because it doesn’t contain dampering, longer ducts might have an effect on air distribution to conditioned areas.
Whereas totally different duct design strategies used differ from software to software, duct system efficiency and system balancing and optimisation have to be thought of. After the air dealing with unit (AHU) is put in, the system must be balanced and optimised to boost efficiency. In system balancing and optimisation, air movement charges of provide air retailers and return air inlets are measured, and dampers and fan pace are adjusted. Particularly in massive buildings, balancing air-con programs could also be costly and time-consuming, however it’s required because it supplies advantages that outweigh the fee incurred in putting in the system. To minimise complete and working value, many optimisation strategies are used as such because the T-Technique Optimisation described within the DA3 Software Guide of AIRAH (Australian Institute of Refrigeration Air Conditioning).
To design air distribution programs which might be vitality environment friendly and value efficient, HVAC system designs should embrace primary engineering pointers and cling to sure design requirements. Allow us to contemplate a number of the pointers and requirements used within the business in numerous nations.
Ductwork Design Requirements
When designing air-con programs, HVAC design engineers have to be educated in regards to the primary strategies, pointers and requirements relevant, from the kind of items used, calculations required, strategies of development, kind of fabric, duct system layouts, pressure losses, duct leakage, noise issues to optimisation utilizing testing, adjusting and balancing (TAB). Listed beneath are a number of the requirements organisations and associations within the U.S., U.Okay., Australia and India, that present manuals, codes and requirements for the HVAC business.
U.S.
• SMACNA (Sheet Metallic and Air Conditioning Contractors’ Nationwide Affiliation) – It supplies a handbook on HVAC programs duct design that features primary but elementary strategies and procedures with significance on vitality effectivity and conservation. Whereas the handbook doesn’t embrace load calculations and air air flow portions, it’s usually used along with the ASHRAE Fundamentals Handbook.
• ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers) – It’s an affiliation that emphasises on the sustainability of constructing programs by specializing in vitality effectivity and indoor air high quality. The ASHRAE Handbook is a four-volume information that gives the basics of refrigeration, functions, programs and tools. Up to date each 4 years, the handbook consists of worldwide items of measurement akin to SI (programs worldwide) and I-P (inch-pound).
U.Okay.
• CIBSE (The Chartered Establishment of Constructing Services Engineers) – is the authority within the UK that units requirements for constructing services engineering programs. The Codes and Tips printed by CIBSE are recognised internationally and regarded as the standards for greatest practices within the areas of sustainability, development and engineering.
• BSRIA (Constructing Services Analysis and Data Affiliation) – is an affiliation that gives services that assist corporations improve their designs to extend vitality effectivity in adherence to Constructing Laws, mock-up testing of programs and BIM help click resources.
Australia
• AIRAH (Australian Institute of Refrigeration Air Conditioning) – supplies technical manuals for professionals within the HVAC business and knowledge starting from air-con load estimation, ductwork for air-con, pipe sizing, centrifugal pumps, noise control, fans, air filters, cooling towers, water remedy, upkeep, indoor air high quality and constructing fee.
India
• BIS (Bureau of Indian Requirements) – is a nationwide authority that gives requirements and pointers as per the Worldwide Group for standardisation (ISO). The handbooks by BIS stipulates the code of practices relevant to the HVAC business akin to safety code for air-con, specification for air ducts, thermostats to be used in air conditioners, steel duct work, air-cooled warmth exchangers and knowledge for out of doors design circumstances for air-con for Indian cities
• ISHRAE (The Indian Society of Heating, Refrigerating and Air Conditioning Engineers) – supplies indoor environmental high quality requirements and testing and score pointers based mostly on frequent IEQ parameters requirements and standards for the classification of buildings based mostly on vitality effectivity.
Whereas HVAC design engineers should maintain related requirements in thoughts and be sure that native codes are utilized in designs, vitality effectivity is a main goal as nicely. Ductwork design performs a big position in regulating indoor air high quality, thermal consolation and air flow. The important thing perform of ductwork design is to offer the least obtrusive channel by which cool and heat air can travel in probably the most environment friendly and cost-effective means.
Inaccurate duct designs might lead to poor indoor air high quality, warmth loss and uncomfortable conditioned house within the constructing. A well-designed air-con HVAC system will in the end optimise prices. By regulating pressure loss, deciding on the precise duct measurement, balancing air pressure and controlling acoustics, ductwork designers might optimise manufacturing, operational, environmental and commissioning prices.