Right this moment, one of many vital aims in MEP engineering design for HVAC design engineers is to enhance power effectivity, keep air high quality and thermal consolation. Vitality effectivity, air high quality and luxury in a constructing depend upon how heating, cooling and air distribution techniques are designed and that is the place cautious ductwork design performs a major position. Ductwork and HVAC system design are essential 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 way of which cool and heat air can travel. When designed precisely, HVAC air distribution techniques will play an essential position in countering warmth power losses, sustaining indoor air high quality (IAQ) and offering thermal consolation.
To grasp how ductwork could be designed in a cheap and environment friendly method, this text decodes ductwork design and offers a quick define of the design course of, strategies and requirements.
What’s Ductwork?
The fundamental precept of ductwork design is to warmth, cool or ventilate a constructing in probably the most environment friendly and cost-effective manner. The first operate of ductwork is to design conduits or passages that enable air stream to supply heating, cooling, air flow and air-con (HVAC).
Within the duct design course of, the fundamentals of air stream should be understood. Return air goes into an air handler unit (AHU), by way of a filter and into the blower and with pressure it goes by way of the A coil or warmth exchanger after which it goes out into the provision air system. If the ductwork is designed accurately it permits the AHU to provide the correct amount of air by way of the warmth exchanger. In a typical air distribution system, ducts should accommodate provide, return and exhaust air stream. Provide ducts present air required for air-con and air flow, return ducts present regulated air to keep up IAQ and temperature and exhaust air stream techniques 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 comparable to architectural, civil and structural ideas to make sure HVAC techniques are conflict free.
The Ductwork Design Course of
The ducting system design course of is straightforward, offered that the specs are clearly talked about and the inputs relating to software, exercise, constructing orientation and constructing materials are offered. Primarily based on the data offered calculations could be accomplished to create an energy-efficient and clash-free design. Usually, air-con and distribution techniques are designed to fulfil three major necessities comparable to:
• It ought to ship air stream at particular charges and velocity to stipulated places.
• It must 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 consumer or MEP consultants. Constructing service engineers then require specification necessities comparable to software, the variety of folks, the orientation of the constructing and architectural traits to make calculations on warmth load and air stream. Earlier than any calculations are carried out, single line drawings are drafted to showcase the stream of ductwork within the constructing. As soon as they’re permitted, calculations for warmth load and air stream are performed. As soon as the warmth load calculations are full, the air stream charges which can be required are identified and the air shops are fastened. With the calculations, specs and structure, the ducting system design structure is then designed considering architectural and structural particulars of the conditioned area and clashes with different constructing services comparable to electrical, plumbing (hydraulic) and mechanical services.
To begin the ductwork design course of there are inputs required relating to particulars about the kind of software, specification necessities, constructing orientation, architectural attribute and materials.
• Software sort – Ductwork design will fluctuate primarily based on the kind of software the constructing shall be used for comparable to manufacturing, information centres, medical functions, scientific analysis and luxury functions comparable to eating places, workplaces, residences, institutional constructing comparable to colleges and universities.
• Specification requirement – To create an environment friendly duct design, designers have to know what sort of exercise shall be performed and the typical variety of folks that can use the conditioned area. This may assist in calculating the air stream, velocity and warmth load required to keep up 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 could be calculated. The kind of materials used for building additionally impacts the quantity of warmth acquire 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 price, necessities, specs and power effectivity requirements. Primarily based on the load of the duct from air pressure, duct techniques can usually be labeled into excessive velocity, medium velocity and low velocity techniques. There are three generally used strategies for duct design:
1. Fixed Velocity Technique – This technique, designed to keep up minimal velocity, is without doubt one of the easiest methods to design duct techniques for provide and return air ducts. Nonetheless, it requires expertise to make use of this technique as the inaccurate collection of velocities, duct sizes and selection of fixtures might enhance the price. Furthermore, to keep up the identical fee of pressure 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 typical technique used for each provide and return ducts maintains the identical frictional pressure drop throughout major and department ducts. This technique ensures dissipation of pressure drops as friction in duct runs slightly than in balancing dampers. Nonetheless, like the speed technique, partial closure of dampers is required and this might result in noise technology.
3. Static Regain Technique – This technique generally used for giant provide techniques with lengthy ducts is a excessive velocity system that maintains fixed static pressure earlier than every department or terminal. Whereas it is 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 fluctuate from software to software, duct system efficiency and system balancing and optimisation should be thought-about. After the air dealing with unit (AHU) is put in, the system must be balanced and optimised to reinforce efficiency. In system balancing and optimisation, air stream charges of provide air shops and return air inlets are measured, and dampers and fan pace are adjusted. Particularly in massive buildings, balancing air-con techniques could also be costly and time-consuming, however it’s required because it offers advantages that outweigh the price incurred in putting in the system. To minimise whole and working price, 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 techniques which can be power environment friendly and value efficient, HVAC system designs should embody primary engineering pointers and cling to sure design requirements. Allow us to take into account a few of the pointers and requirements used within the business in numerous international locations.
Ductwork Design Requirements
When designing air-con techniques, HVAC design engineers should be educated in regards to the primary strategies, pointers and requirements relevant, from the kind of models used, calculations required, strategies of building, sort of fabric, duct system layouts, pressure losses, duct leakage, noise concerns to optimisation utilizing testing, adjusting and balancing (TAB). Listed under are a few 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 offers a handbook on HVAC techniques duct design that features primary but elementary strategies and procedures with significance on power effectivity and conservation. Whereas the handbook doesn’t embody 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 techniques 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, techniques and gear. Up to date each 4 years, the handbook consists of worldwide models of measurement comparable to SI (techniques 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 techniques. The Codes and Tips printed by CIBSE are recognised internationally and regarded as the factors for greatest practices within the areas of sustainability, building and engineering.
• BSRIA (Constructing Services Analysis and Data Affiliation) – is an affiliation that gives services that assist corporations improve their designs to extend power effectivity in adherence to Constructing Laws, mock-up testing of techniques and BIM help our website.
Australia
• AIRAH (Australian Institute of Refrigeration Air Conditioning) – offers 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 comparable 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 information for out of doors design situations 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 frequent 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 make sure that native codes are utilized in designs, power effectivity is a major goal as effectively. Ductwork design performs a major position in regulating indoor air high quality, thermal consolation and air flow. The important thing operate of ductwork design is to supply the least obtrusive channel by way of which cool and heat air can travel in probably the most environment friendly and cost-effective manner.
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 pressure loss, deciding on the proper duct dimension, balancing air pressure and controlling acoustics, ductwork designers might optimise manufacturing, operational, environmental and commissioning prices.