Right now, one of many important targets in MEP engineering design for HVAC design engineers is to enhance power effectivity, preserve air high quality and thermal consolation. Power effectivity, air high quality and luxury in a constructing depend upon how heating, cooling and air distribution methods are designed and that is the place cautious ductwork design performs a big function. 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 should not designed precisely, it might result in poor air high quality, warmth loss and make the conditioned area within the constructing uncomfortable.
The first operate of the ductwork design system is to make sure a least obtrusive channel is offered by means of which cool and heat air can journey. When designed precisely, HVAC air distribution methods will play an necessary function in countering warmth power losses, sustaining indoor air high quality (IAQ) and offering thermal consolation.
To know how ductwork will be designed in an economical and environment friendly method, this text decodes ductwork design and offers a short define of the design course of, strategies and requirements.
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 operate of ductwork is to design conduits or passages that permit 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 means of a filter and into the blower and with strain it goes by means of the A coil or warmth exchanger after which it goes out into the provision air system. If the ductwork is designed appropriately it allows the AHU to supply the correct amount of air by means of 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 methods present air flow.
For ductwork design to be environment friendly, MEP engineering design groups must have designers with a mechanical and engineering background. Ductwork design specialists or constructing service engineers should additionally possess thorough information of different disciplines similar to architectural, civil and structural ideas to make sure HVAC methods are conflict free.
The Ductwork Design Course of
The ducting system design course of is easy, offered that the specs are clearly talked about and the inputs concerning software, exercise, constructing orientation and constructing materials are offered. Primarily based on the knowledge offered calculations will be accomplished to create an energy-efficient and clash-free design. Sometimes, air-con and distribution methods are designed to fulfil three major necessities similar to:
• It ought to ship air movement at particular charges and velocity to stipulated places.
• It needs to be power 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 offered by the shopper or MEP consultants. Constructing service engineers then require specification necessities similar to software, the variety of folks, 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 carried out. As soon as the warmth load calculations are full, the air movement charges which are required are identified and the air shops are mounted. With the calculations, specs and format, the ducting system design format is then designed taking into account architectural and structural particulars of the conditioned area and clashes with different constructing providers similar to electrical, plumbing (hydraulic) and mechanical providers.
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.
• Utility kind – Ductwork design will differ primarily based on the kind of software the constructing will probably be used for similar to manufacturing, information centres, medical functions, scientific analysis and luxury functions similar to eating places, places of work, residences, institutional constructing similar to colleges and universities.
• Specification requirement – To create an environment friendly duct design, designers must know what kind of exercise will probably be carried out and the typical variety of folks that may use the conditioned area. It will 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 function 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 will be calculated. The kind of materials used for building 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 normally decided primarily based on the fee, necessities, specs and power effectivity requirements. Primarily based on the load of the duct from air strain, duct methods can sometimes be labeled into excessive velocity, medium velocity and low velocity methods. There are three generally used strategies for duct design:
1. Fixed Velocity Technique – This technique, designed to take care of minimal velocity, is without doubt one of the easiest methods to design duct methods for provide and return air ducts. Nonetheless, it requires expertise to make use of this technique as the inaccurate choice of velocities, duct sizes and selection of fixtures might improve the fee. Furthermore, to take care of the identical fee of strain drop in duct runs, this technique requires partial closure of dampers in duct runs (besides index run) which might have an effect on effectivity.
2. Equal Friction Technique – This standard technique used for each provide and return ducts maintains the identical frictional strain drop throughout major and department ducts. This technique ensures dissipation of strain drops as friction in duct runs somewhat than in balancing dampers. Nonetheless, like the rate technique, partial closure of dampers is required and this might result in noise era.
3. Static Regain Technique – This technique generally used for giant provide methods with lengthy ducts is a excessive velocity system that maintains fixed static strain earlier than every department or terminal. Whereas this can be a balanced system because it doesn’t contain dampering, longer ducts could 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 should 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 shops and return air inlets are measured, and dampers and fan velocity are adjusted. Particularly in massive buildings, balancing air-con methods could also be costly and time-consuming, however it’s required because it offers 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 Utility Guide of AIRAH (Australian Institute of Refrigeration Air Conditioning).
To design air distribution methods which are power environment friendly and value efficient, HVAC system designs should embody fundamental engineering pointers and cling to sure design requirements. Allow us to take into account among the pointers and requirements used within the trade in numerous international locations.
Ductwork Design Requirements
When designing air-con methods, HVAC design engineers have to be educated concerning the fundamental strategies, pointers and requirements relevant, from the kind of models used, calculations required, strategies of building, kind of fabric, duct system layouts, strain losses, duct leakage, noise issues to optimisation utilizing testing, adjusting and balancing (TAB). Listed beneath are among the requirements organisations and associations within the U.S., U.Okay., Australia and India, that present manuals, codes and requirements for the HVAC trade.
• SMACNA (Sheet Steel and Air Conditioning Contractors’ Nationwide Affiliation) – It offers a guide on HVAC methods duct design that features fundamental but basic strategies and procedures with significance on power effectivity and conservation. Whereas the guide doesn’t embody load calculations and air air flow portions, it’s sometimes 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 methods by specializing in power effectivity and indoor air high quality. The ASHRAE Handbook is a four-volume information that gives the basics of refrigeration, functions, methods and gear. Up to date each 4 years, the handbook contains worldwide models of measurement similar to SI (methods worldwide) and I-P (inch-pound).
• CIBSE (The Chartered Establishment of Constructing Providers Engineers) – is the authority within the UK that units requirements for constructing providers engineering methods. The Codes and Tips revealed by CIBSE are recognised internationally and regarded as the factors for greatest practices within the areas of sustainability, building and engineering.
• BSRIA (Constructing Providers Analysis and Data Affiliation) – is an affiliation that gives providers that assist corporations improve their designs to extend power effectivity in adherence to Constructing Laws, mock-up testing of methods and BIM assist.
• AIRAH (Australian Institute of Refrigeration Air Conditioning) – offers technical manuals for professionals within the HVAC trade and knowledge starting from air-con load estimation, ductwork for air-con, pipe sizing, centrifugal pumps, noise management, followers, air filters, cooling towers, water remedy, upkeep, indoor air high quality and constructing fee.
• 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 trade similar to security code for air-con, specification for air ducts, thermostats to be used in air conditioners, steel duct work, air-cooled warmth exchangers and information for out of doors design circumstances for air-con for Indian cities
• ISHRAE (The Indian Society of Heating, Refrigerating and Air Conditioning Engineers) – offers indoor environmental high quality requirements and testing and ranking pointers primarily based on widespread IEQ parameters requirements and standards for the classification of buildings primarily based on power effectivity.
Whereas HVAC design engineers should maintain related requirements in thoughts and be sure that native codes are utilized in designs, power effectivity is a major goal as nicely. Ductwork design performs a big function in regulating indoor air high quality, thermal consolation and air flow. The important thing operate of ductwork design is to offer the least obtrusive channel by means of which cool and heat air can journey in probably the most environment friendly and cost-effective means.
Inaccurate duct designs might end in poor indoor air high quality, warmth loss and uncomfortable conditioned area within the constructing. A well-designed air-con HVAC system will finally optimise prices. By regulating strain loss, choosing the suitable duct dimension, balancing air strain and controlling acoustics, ductwork designers might optimise manufacturing, operational, environmental and commissioning prices.