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Introduction Many of our homes and most offices and commercial facilities would not be comfortable without control of the indoor environment. The "luxury label" attached to air conditioning in earlier decades has given way to appreciate it practicality in making our live healthier and more productive. Along with rapid development in improving human comfort came the realization that goods could be produced better, faster, and more economically in a properly controlled environment.

AutoCAD MEP is the AutoCAD software for mechanical, electrical, and plumbing designers and drafters. Creation and coordination of construction documents is more efficient with AutoCAD MEP’s more intuitive systems drawing and design tools. AutoCAD MEP also assessing our vision and enhance our efficiency because of its purpose-built software for MEP designers and drafters. With AutoCAD MEP we are able to make changes much faster, thus help minimizing the financial impact, and make those changes in almost real time.

1.1

The project goal

This project aims at designing an air-conditioning system for Dawood Abdellatif building. A complete air conditioning system will be designed to control the indoor environment (temperature, relative humidity, air movement, etc.) in an economical way using AutoCAD MEP.

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Air-conditioning and Air-conditioning System Design 2.1

What is air conditioning? Heating ventilating and air-conditioning HVAC is one of the building mechanical services that include plumbing, fire protection, and escalators. Air-conditioning refers to any form of cooling, heating, ventilation or disinfection that modifies condition of air. The goal of an HVAC system is to provide an energy efficient, cost effective, healthy and comfortable indoor environment with acceptable indoor air quality. [1]

2.2

Air conditioning systems classification Corresponding to their related equipment Air conditioning systems may be classified as:

1. Central systems.

2. Decentralized systems; the distinction between central and decentralized systems is critical from an architectural perspective. According to the method by which the final within the space cooling and heating are attained, air-conditioning systems are generally divided into four basic types: 1. All-air system when energy is transferred only by means of heated or cooled air.

2. All-water system when energy is transferred only by means of hot or chilled water. 3. Air-water system when energy is transferred by a combination of heated/cooled air and hot/chilled water. 4. Unitary refrigerant based system when energy is transferred by a refrigerant.

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2.3

Central air conditioning systems

A central HVAC system serves one or more thermal zones and has its major components located outside the zone or zones being served in some convenient central location in the building or near it. District systems serving more than one building revert to central systems at the single building level.

2.3.1 Central air conditioning systems components

Central air conditioning systems basically consist of three major parts:

1. An air system or air handling unit (AHU), air distribution system (air ducts) and terminals. 2. Water system – chilled water system, hot water system, condenser water system. 3. Central plant – refrigeration (chiller) plant, boiler plant.

2.3.2Advantages of central air conditioning systems



Allow major equipment components to be isolated in a mechanical room (i.e. allows maintenance to occur with limited disruption to building functions, reduce noise and aesthetic impacts on building occupants).



Offer opportunities for economies of scale.



Larger capacity refrigeration equipment is usually more efficient than smaller capacity equipment; larger systems can utilize cooling towers that improve system efficiencies in many climates.



Central systems may permit building-wide load sharing resulting in reduced equipment sizes, costs, and the ability to shift conditioning energy from one part of a building to another.

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Central systems are amenable to centralized energy management control schemes; i.e. reduced building energy consumption.



A central system may be appropriate for other than climate control perspective; active smoke control is best accomplished by a central allair HVAC system.

2.3.3 Disadvantages of Central air conditioning systems



As a non-distributed system, failure of any key equipment component may affect the entire building.



As system size and sophistication increase, maintenance may become more difficult and may be available from fewer providers if specialists are needed.



Large centralized systems tend to be less intuitive making systems analysis and understanding more difficult.

2.4Decentralized air conditioning systems

A decentralized system serves a single thermal zone and has its major components located within the zone itself, on the boundary between the zone and the exterior environment, or directly adjacent to the zone.

Decentralized systems may be divided into:

1. Individual Systems using self-contained, factory-made air conditioner to serve one or two rooms.

2. Unitary Systems, which are similar in nature to individual systems but serve more rooms or even more than one floor, have an air system consisting of fans, coils, filters, ductwork and outlets (e.g. in small restaurants, small shops and small cold storage rooms). The term packaged air-conditioner is

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sometimes used interchangeably with the unitary air-conditioner. The airconditioning and refrigeration institute ARI defines a unitary air-conditioner as one or more factory-made assemblies that normally include an evaporator/cooling coil and a compressor and condenser combination. 2.4.1 Advantages of decentralized air conditioning systems

o Serving only a single zone, decentralized HVAC systems will have only one point of control typically a thermostat for active systems. o Each decentralized system generally does its own thing, without regard to the performance or operation of other decentralized systems. o Decentralized systems tend to be distributed systems providing greater collective reliability than do centralized systems.

2.42Disadvantages of decentralized air conditioning systems:

 Decentralized system units cannot be easily connected together

to

permit

centralized

energy

management

operations.  Decentralized systems can usually be centrally controlled with respect to on-off functions through electric circuit control, but more sophisticated central control (such as night-setback or economizer operation) is not possible.

2.5

All air systems

2.5.1 Introduction:

All-air systems provide sensible and latent cooling capacity solely through cold supply air delivered to the conditioned space. No

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supplemental cooling is provided by refrigeration sources within the zones and no chilled water is supplied to the zones. Heating may be accomplished by the same supply airstream, with the heat source located either in the central system equipment or in a terminal device serving a zone. A zone is an area controlled by a thermostat, while a room refers to a partitioned area that may or may not have a separate thermostat.

2.5.2 Advantages of All air systems:

o Such systems are well suited to air-side economizer use, heat recovery, winter humidification, and large-volume outdoor air requirements. o They are the best choice for close control of zone temperature and humidity. o They are generally a good choice for applications where indoor air quality is a key concern. o They are amenable to use in smoke control systems. o There is simple seasonal changeover. o Such systems generally permit simultaneous heating and cooling in different zones.

2.53Disadvantages of All air systems:

 All-air systems use significant amounts of

energy to move air (approximately 40% of allair system energy use is fan energy).  Ductwork space requirements may add to building height.  Air balancing may be difficult.

 It is difficult to provide comfort in locations with low outdoor temperatures and typical building envelope performance when warm air is used for perimeter heating.

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 Providing ready maintenance accessibility to terminal devices

requires

close

coordination

between

mechanical, architectural, and structural designers.

27 Air and water systems

Air-and-water systems condition spaces by distributing both conditioned air and water to terminal units installed in the spaces. The air and water are cooled and/or heated in a central mechanical equipment room. The air supplied is termed primary air to distinguish it from recirculated (or secondary) room air. Air-and-water systems that have been used in buildings of various types are presented below. Not all of these systems are equally valid in the context of a given project. Not all of these systems see equal use in today’s design environment. They are presented, however, to provide a sense of the possibilities and constraints inherent in the use of an air-and-water HVAC system.

2.6.1 Advantages and Disadvantages of Air and water systems:

Because of the greater specific heat and the much greater density of water compared to air, the cross-sectional area of piping is much smaller than that of ductwork to provide the same cooling (or heating) capacity. Because a large part of the space heating/cooling load is handled by the water part of this type of system, the overall duct distribution requirements in an air-and-water system are considerably smaller than in an all-air system—which saves building space. If the system is designed so that the primary air supply is equal to the ventilation requirement or to balance exhaust requirements, a return air system can be eliminated. The air-handling system is smaller than that for an all air

system, yet positive ventilation is ensured. Numerous zones can be individually controlled and their cooling or heating demands satisfied

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independently and simultaneously. When appropriate to do so (as during unoccupied hours), space heating can be provided by operating only the water side of the system—without operating the central air system. When all primary air is taken from outdoors, cross-contamination between rooms can be reasonably controlled.

Design for intermediate season operation is critical. Changeover operation

(between

seasons)

can

be

difficult

and

requires

a

knowledgeable staff. Controls are more complicated than for all-air systems, and humidity cannot be tightly controlled. Induction and fan-coil terminal units require frequent in-space maintenance.

2.7

All water systems

In an all-water system, space cooling and/or heating is provided by chilled and/or hot water circulated from a central refrigeration/ boiler plant to terminal units located in, or immediately adjacent to, the various conditioned spaces. Heat transfer to/from the room air occurs via forced or natural convection. Except for radiant systems, radiant heat transfer is usually nominal due to the size and arrangement of the heat transfer surfaces. All-water systems can be employed for both heating and cooling. Heating water is supplied either through the same piping network used for chilled water in summer or through an independent piping system.

2.7.1 Advantages of all water systems:

 Less building space is required for distribution elements.

 They are well suited for retrofit applications due to their distribution efficiency.  Little (often no) space is needed for a central fan room.

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• There is ready potential for individual room control with little or no crosscontamination of air between rooms.  Because low-temperature water can be used for heating, they are well suited for solar heating and heat recovery applications.

2.7.2 Disadvantages of all water systems:

• Maintenance demands can be high and maintenance must be performed on terminals within occupied spaces.  Condensate drain pans and a drain system are required; in addition, they must be cleaned periodically.  Ventilation is not centrally provided or controlled and is often accomplished by opening windows or via an outdoor air inlet at each terminal unit; thus, providing for acceptable indoor air quality can be a serious concern.  Relative humidity in spaces may be high in summer, particularly if modulating chilled-water valves are used to control room temperature.

2.8

Air conditioning system design Air-conditioning system design is the process of selecting the

optimum system, subsystem, equipment, and components from various alternatives and preparing the drawings and specifications. Air-conditioning system design process comprises five phases: schematic design phase, design development phase, construction document phase, bidding or negotiation phase, and construction phase.

The purpose of conceptual/schematic design efforts is to develop an outline solution to the owner’s project requirements (OPR) that captures the owner’s attention, gets his/her buy-in for further design efforts, and meets budget. Schematic (or early design development) design efforts should serve as proof of concept for the earliest design ideas as elements of the solution are further developed and locked into place. During later

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design development/construction documents, the final drawings and specifications are prepared as all design decisions are finalized and a complete analysis of system performance is undertaken. The schematic/early design development stage should involve the preliminary selection and comparison of appropriate HVAC&R systems. All proposed systems must be able to maintain the environmental conditions for each space as defined in the OPR. The ability to provide adequate thermal zoning is a critical aspect of such capability. For each system considered during this phase, evaluate the relative space (and volume) requirements for equipment, ducts, and piping; fuel and/or electrical use and thermal storage requirements; initial and life-cycle costs; acoustical requirements and capabilities; compatibility with the building plan and the structural system; and the effects on indoor air quality, illumination, and aesthetics. Also consider energy code compliance and green design implications (as appropriate). [2]

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Using AutoCAD programs in designing projects 3.1

BIM Terminology and Definitions

The ASHRAE (American Society of Heating, Refrigerating and AirConditioning Engineers) defined BIM as the process of using intelligent graphic and data modeling software to create optimized and integrated building design solutions. BIM encompasses the use of three-dimensional, real-time, intelligent and dynamic modeling, and can be a valuable tool in facilitating successful coordination and collaboration. Architects are the heaviest users of BIM. [3]

3.2

The traditional construction design delivery method

A new project usually starts when the owner approaches a design professional with an idea for a new facility. Usually the first contact is with a project architect, who hires a team of other design specialists such as structural (civil) engineer, an HVAC and plumping (mechanical) engineer, and an electrical engineer. The main responsibility of the design professional team is to produce the schematic, layout, and detail drawings, and to prepare the job specifications and equipment schedules required to bring the job to completion.

The traditional construction Design-Bid-Build delivery method for Architecture, Engineering, Construction, and Facility Management industry is fragmented, and is based on traditional use of 2D information systems as well as on the use of 2D paper documents. Errors and omissions in

paper documents often cause unanticipated field costs, delays and eventual lawsuits between the various parties in a project team. These problems cause friction, financial expense and delays.

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For the traditional paper-based delivery process, the poor field productivity

and

non-effective

information

flow

can

explain

how

unnecessary waster and errors are generated. The lack of industry leadership and lack of labor saving innovations could be the reasons that lower the productivity in construction industry. Also, due to the fragmentation of the industry, integrated information systems, better supply chain management and improved collaboration tools cannot be efficiently implemented in the construction industry. Furthermore, the use of cheap labor has stagnated the innovation of construction tools and equipment. It is considered that, Building Information Modeling, on the other hand, can reduce the waste generated from the interoperability issue and can increase the productivity as well.

3.3

What is gbXML?

The

Green Building XML schema, referred to as ―gbXML‖,

was developed to facilitate the transfer of building information stored in CAD building information models, enabling integrated interoperability between building design models and a wide variety of engineering analysis tools and models available today. Today, gbXML has the industry support and wide adoption by the leading CAD vendors, Autodesk, Graphisoft, and Bentley. With the development of export and import capabilities in several major engineering modeling tools, gbXML has become a defacto industry standard schema. Its use streamlines the transfer of building information to and from engineering models, eliminating the need for time consuming plan take-offs. This removes a significant cost barrier to designing resource efficient buildings and specifying associated equipment. It enables building design teams to truly collaborate and realized the potential benefits of Building Information Modeling.

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XML, extensible markup language, is a type of computer language that allows software programs to communicate information with little to no human interaction. This approach allows building designers to focus on what they want to do most - design beautiful, environmentally responsible buildings that use intelligent technologies to meet their client's needs at the lowest cost possible. Helping realize the promise of Building Information Modeling, gbXML allows intelligent solutions for the design, certification, operation, maintenance, and recycling of buildings. [4]

3.4

Global benefits of BIM concept: To understand the benefits of BIM to our industry, we must explore

some of the global benefits of BIM and discuss the direct benefits to ASHRAE and its members of embracing and adopting BIM, integration and interoperability. Globally one of the great advantages of Building Information Modeling is the ability to create an accurate model that is useful throughout the entire life of the building, from initial design through occupancy and operation (see definitions). Ideally, a BIM would be created in the early stages of the design, updated as the design is refined and used by the construction team, and refined continuously as the facility is built. Post-occupancy, the BIM would be used by the owner and owner’s maintenance team to improve understanding of building operation and to make adaptations, renovations, additions and alterations to the building faster and for less cost than through traditional processes. Future benefits may include linking manufacturers’ R&D databases, which will be discussed later in this guide. In addition, operating level BIMs may be linked through integrated and interoperable pipelines to local and national emergency response and disaster management systems to help improve life-safety save lives and mitigate damage.

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The power of BIM can be realized though its ability to allow the whole building to be optimized in lieu of optimizing individual components. Each discipline and trade benefits through integration and optimization within a BIM and becomes more efficient by providing parametric responses to single discipline changes through the use of consistent data sets for calculation and decision making. The work of the HVAC industry has an impact on every other design and construction discipline and trade including the following: architecture, electrical engineering, lighting design, roof and envelope consultation, food service, fire protection, civil engineering, structural engineering, security consultants, acoustical engineering and others. BIM can benefit these associated and complimentary disciplines and trades through precise interdisciplinary coordination using parametric geometric modeling. However, much of the existing software, such as load calculation, plumbing, piping, lighting design and life-cycle assessment tools, only receive input data from the BIM at this time and are not fully parametric. Software and hardware developments that will allow adjustments and fine tuning of the calculations via changes in the BIM and vice versa that would result in optimizing the BIM in real time will be available in the near future.

The benefits of BIM are evident in its capability of capturing, organizing, integrating, maintaining and growing the vast amount of knowledge, data and information required to conceive, plan, design, construct, operate, maintain, adapt, renovate and, finally, beneficially deconstruct a building at the end of its life cycle. The HVAC&R industry impacts building owners, users, regulatory agencies, legal, finance, operation and maintenance, the environment, and community. BIM can benefit project participants and these entities through improved

multidiscipline

collaboration

to

achieve

optimal

solutions,

interference checking prior to construction, reduced errors and omissions,

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automated code/regulatory reviews, accelerated permitting, and earlier beneficial occupancy, leading to enhanced return on investment (ROI) for the building owner/developer. Real-time monitoring of a building’s temperature, humidity, ventilation, air quality, pressurization, isolation, compartmentation, and occupant location integrated into the BIM can benefit first responders in public health, safety, fire, law enforcement and disaster recovery to help save lives, protect property, and mitigate environmental and property damage. During design and construction all disciplines and trades involved on a project can benefit from using BIM through: 1. Early Collaboration:

BIM fosters collaboration in the early phases of a project between team members through the use of consistent and more complete information more effectively than do traditional approaches. This allows design decisions to be made that optimize the whole building at a stage when they are far less expensive to analyze, rather than the traditional approach of optimizing individual components. This should minimize the need to make changes later in the design or during the construction process when even small changes can have enormous effects on both the construction cost and life-cycle cost of the building. 2. Parametric Modeling:

Certain features, objects and components represented within a BIM can be related parametrically. (See definitions of parameter, parametric and intelligent objects.) Therefore, a number of related conditions can be updated by changing only one property. For example, if a diffuser is associated with a certain low-pressure duct, and that diffuser is moved,

the associated duct will automatically relocate to the appropriate new position relative to the diffuser. Thus, not only can design changes be made earlier, they can also be made much faster and easier. This

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provides the designer greater certainty that all views have been updated with current information. 3. Quality:

The ability of BIM to integrate multiple disciplines with the use of a common model means that coordination between team members is made easier, and design optimization and interference checking can be performed more frequently. This can be achieved through proprietary, single vendor solutions or through viewers and model checkers that can take advantage of interoperability and read, translate and understand multiple vendor file formats, possibly through IFC interfaces, domain specific XML tagging and other data exchange specifications and standards. This ability offers the potential for more thorough quality control in the design phase prior to construction activity beginning, which should result in fewer requests for information (RFIs) and change orders. For example, early interference checking and clash avoidance between ductwork and structural members facilitated by better 3-D visualization by designers and automated clash detection and model checking features that exist in the BIM or through interoperable applications can result in HVAC systems operating at lower static pressures, lower noise levels and lower horsepower than a system where the clashes are resolved in the field, by the ―first trade there‖ method of clash detection, which can result in multiple offsets, cumbersome ―work-arounds,‖ changes in duct dimensions, waste and re-work in the field. Another benefit of BIM is the potential for ongoing commissioning. Real-time performance data gathering, verification and management allows for effective adjustments to systems to improve human comfort

and safety and to optimize performance while

environmental impacts.

minimizing

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4. Economics:

BIM can provide economic benefits for all stake holders. For example, investing in BIM technology by the design team frequently involves some initial expense; however, there is great potential to reduce design and production cost through more efficient use of time and better visualization. Contractors can benefit from the use of BIM through better coordination, better cost estimating and procurement management, use of the BIM for automation of off-site fabrication, and for better scheduling, which can provide cleaner and safer construction sites and shorter construction duration. The owner can benefit from the BIM through achieving greater certainty in outcomes with respect to project cost and time that can be better estimated when 4-D and 5-D BIM are integrated into the process earlier. 5. Sustainability and climate protection:

BIM will play a major role in helping us meet the world’s need for sustainable construction and climate protection. HVAC&R systems are one of the largest users of energy in a building. BIM will allow a design team to better take a ―reduce and optimize‖ approach to reaching a client’s and building project’s sustainability and climate protection goals by focusing on reducing energy first. The most important aspect of providing sustainable high performance buildings is the attention to detail that can be given to the selection, optimization and use of materials and components based on whole building life-cycle assessment (LCA). A large component of an LCA is the building’s use of nonrenewable energy sources. BIM allows the rapid and economical (relative terms) consideration of alternatives, what ifs, and game scenarios early in the evolution of a building to optimize the building’s life-cycle impact.

For buildings to be sustainable, they must be adaptable. A building’s materials, components, contents and systems should ultimately be 100%

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recyclable either through adaptive reuse, preservation, restoration, salvage, and/or traditional recycling processes. A building that serves as a school today should be able to function as an office building or medical facility in the future. A BIM is a living historical database of every material, component, assembly, and system used in the building. The BIM can contain design, construction, and life-cycle assessment information; operation, service and maintenance data; along with energy use down to the system and component level that could be used for intelligent strategic planning for the adaptive reuse or recycling of a building should renovation, restoration or demolition become necessary. The popular mantras ―reduce, reuse, and recycle‖ will be better served through the use of BIM, integration and interoperability.

3.5

Benefits of BIM to HVACR industry Design professional: The greatest benefits of BIM to the design

professional will be its fundamental effect on the process of design. By moving away from 2-D and 3-D CAD and paper-based review, analysis and work product delivery processes, BIM will help increase productivity, lower design cost and improve design quality. Increased productivity and lower design cost will be realized by using information about the building contained in the BIM to automate precise quantity, material and assembly takeoff, reduce the time required to perform HVAC&R load analyses, energy modeling, duct design, air distribution design, piping system design, equipment selection, cost estimating and specification production. Improved design quality will be achieved through greater visualization and, thus, better understanding of end results, more precise interdisciplinary coordination and clash and conflict avoidance prior to construction, reduced requests for interpretation (can also be referred to as requests of information) from contractors and, as a result, less coordination related

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change orders. BIM, integration and interoperability will allow the design professional to work in an environment that provides greater certainty of the correlation between design intent and the final construction and operation of the building. Construction professional: Similar benefits as stated for the design professional will also accrue to the construction professional as a result of more precise and integrated design processes that include fabrication and constructability evaluations. In addition, the construction professional who learns to take advantage of a design level BIM, takes over its management and adds construction level details, subcontractor information, piece and part numbers and 4-D and 5-D data, will then increase productivity, lower construction cost, improve construction quality, better manage risk and enhance job-site safety. Increased productivity and lower construction cost will be realized by using information about the building contained in the design level BIM to automate precise quantity, material and assembly take-off, automate scheduling of crews, subcontractors, temporary facilities and manage procurement, delivery and fabrication processes. Improved construction quality will be achieved through greater visualization and, thus, better understanding of end results, more precise trade coordination and clash and conflict avoidance prior to fabrication and erection, reduced requests for interpretation to the design professional and, as a result, less coordination related change orders. BIM, integration and interoperability will allow the construction professional to also work in an environment that provides greater certainty of outcomes with respect to the final construction and operation of the building.

Manufacturer: The manufacturing industries have recognized the benefits

of information

management,

computer-aided

design

and

modeling, integration and automation for decades. In most cases, many

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manufacturing processes aren’t as diverse or fragmented as the design and construction process. Manufacturers who adopt interoperable and integrated BIM technologies to promote their products and services to owners, design and construction professionals will accrue many of the same benefits previously stated. BIM provides mechanisms for the earlier use of supplier information for selecting products and assessing their installation, commissioning, operation and maintenance characteristics when making design and installation decisions. By providing product data that integrates with and is interoperable with design and analysis tools, detailing and specification systems, cost and scheduling systems, and procurement and construction management systems, manufacturers can better predict future manufacturing needs for their products, better control inventories and improve just-in-time manufacturing and delivery methods. BIM integration can also reduce the cost of creating and updating owner documentation for sales literature, shop drawings, product data, installation instructions, warranty management, training, commissioning, operation and maintenance by including links to the manufacturer’s digital,

Web-based product information. By taking this thought a little further, a manufacturer capable of gathering data, feedback and real-time information embedded in operating level BIMs will be able to use the built environment as a large research and development laboratory to monitor and improve existing products and create new products and opportunities.

Software

developer:

As

previously

stated,

our

technical

knowledge base is doubling at the rate of almost once every two years. Web based applications, cloud computing, model servers, integrated project management and data repositories either exist now or are being developed and tested as this guide is being written. Great economic benefits and opportunities exist to software vendors who can develop interoperable applications, both proprietary and open source solutions,

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that respond to the changing needs and demands of the design, construction, owning, operating and maintenance industries and are capable of keeping up with and maintaining compatibility with the rapid advances that are constantly occurring in science and technology. Academic sector: As our knowledge base expands and more reliable data and metrics are captured from better connected databases and operating level BIMs, researchers will be able to provide better, more focused study, innovations and solutions. They will be the leaders in creating new knowledge to benefit our industry, the community and the environment. BIM is also a training tool for future engineers. ASHRAE: The combined benefits of BIM to every discipline and sector defined above will all accrue to the benefit of ASHRAE. Converting the combined knowledge base contained in our standards, guidelines, handbooks and other publications into digital computer-proccessable resources, so they can be integrated with building information modelling software, will make ASHRAE more valuable to its members and all of humanity.[5]

3.6

Using AutoCAD in designing projects

Depending on BIM concept, Autodesk Company created 3D design packages (AutoCAD MEP, AutoCAD civil3D, AutoCAD Architecture…). With more information being shared throughout the project team, using intelligent, 3D Autodesk design packages, it is now possible to test design considerations in the virtual building model before anything, literally, gets set in concrete which is expensive to fix in the field.

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37 Features of AutoCAD MEP

 One of the major benefits of AutoCAD MEP is the improved coordination with the architectural and structural designs (mechanical, electrical, plumping).  With AutoCAD MEP, production of construction documents is automated, helping to save time and allowing for the creation of single-line and double-line systems in addition to schematics. Whether you are working on a building project led by an architect or partnering with professionals from other disciplines such as structural and civil engineering for the design of water/wastewater facilities, AutoCAD MEP allows you to work in the familiar AutoCAD environment while implementing new systems and documentation tools at your own pace.  Better Design Accuracy: With constant requests to accommodate last minute changes, MEP professionals need to efficiently create and edit designs. Using AutoCAD MEP, you can more easily assess designs, sizing, and system balances with integrated calculators that help ensure accuracy. Errors are minimized with automated drafting tasks and built in calculators.  Coordinate Design Information: With continuous pressure to reduce costs, you can help reduce requests for information (RFIs) and costly design changes in the field with more accurate and consistent construction documents produced with AutoCAD MEP. Design systems using realworld parts and equipment, which can be used throughout the fabrication and construction of the building helping to save time and money.

 Collaborate More Effectively: Since most projects require collaboration with professionals from other disciplines, take advantage of architectural and structural plans developed using AutoCAD-based software coordinate with your extended team.

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applications to better

AutoCAD MEP software helps you to minimize interferences prior to construction, allowing greater coordination and collaboration.

• Single/Double-Line Design: Automate your workflow by creating construction documents more efficiently with single line for design development and convert automatically to double line for construction documents. Lay out mechanical systems in single line with un sized parts early in the design process, and then use duct-sizing tools and convert the layout to double line. Enhanced sizing tools help to increase drafting productivity when moving from design development to construction documentation.  AutoCAD MEP enable us to make zones boundaries and adding engineering properties for each zone separately, engineering properties like light, no. of people, devices, tools, and sun light. Then export zones with their properties to a cooling load calculation program and receive the results. [6]

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AutoCAD MEP concepts 4.1

Working with drawing management projects

The Drawing Management feature formalizes the processes related to building system design and documentation. This feature automates the management, viewing, and construction of building systems, ensuring consistency in all aspects of the project. Consequently, your entire design team has a centralized project environment for accessing the most current documents. The basis of the Drawing Management feature is a sophisticated referenced drawing (xref) feature enhanced from standard AutoCAD xref functionality. Project elements are referenced into constructs; constructs are referenced into views, and views are referenced into plotting sheets. Powerful linking features ensure that source files can be distributed over many different locations on a single computer or network, enabling simultaneous access by others working on the same project.

The Drawing Management feature has two main components • Project Browser: Project Browser creates projects and specifies high-level project information and settings, such as the project number, project name, contact information, and the file locations of the drawing templates, tool palettes, and the project-specific Content Browser library to use. • Project Navigator:

Project Navigator centralizes project-specific tasks, such as defining building levels and divisions (wings), creating project drawings, and creating plotting sheets. A drawing must be part of a project to synchronize with project standards. The Drawing Management feature ensures that project standards are

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properly enforced. You cannot apply project standards to standalone drawings. You can copy standard styles and display settings into standalone drawings, but they are not synchronized when the standards change.

4.2

Establishing project standards

Typically, at the beginning of a project, you establish the standards that guide the project design. Project standards, called CAD standards, enhance efficiency, automate repetition, and maintain consistency across your project drawings and construction documents.

The Project Standards feature lets you establish, maintain, and synchronize standards across all drawings in a Drawing Management project. Project standards include standard styles, display settings, and AutoCAD standards that are used across all project drawings. Standard styles and display settings are specified in one or more standards drawings associated with the project. Project drawings can then be synchronized with these standards throughout the project life cycle, either automatically, or on demand.

Templates store the following standards required to begin a drawing:

o

Unit type and precision.

o Drawing and plotting scales. Dimension and text styles. o Layer structures. o

Line types and line weights.

You can also establish the following design-specific standards on a drawing-by-drawing basis or add them to a template:

 Design and drawing preferences.  Coordinate systems.

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 Design and plotting display layouts.  Title blocks and borders.

4.3

AutoCAD MEP Layer Standards

The Layer Management feature in AutoCAD MEP lets you organize, sort, and group layers using layer standards, layer key styles, and layer overrides. Layer standards define the naming of new layers according to the structure defined in the standard. AutoCAD MEP includes a number of predefined layer standards and matching layer key styles based on common building system industry norms. You can change any part of the layer name structure using layer key overrides within the layer key style. You can also override layer names for all of the layer keys in a layer key style or for individual layer key styles.

4.4

AutoCAD MEP Displays Traditional, manual CAD designs require that you draw a single

object (such as a duct or a pipe) multiple times in different drawings to produce different views of the same object. For example, you might have 1-line drawing of a duct and piping layout and a separate 2-line drawing of the same layout to clarify the construction documents. For each drawing, you use a separate collection of drafting entities to represent the objects. AutoCAD MEP provides tools to view an object in the layout in different ways. This saves time and maintains consistency across all your project

drawings.

26

4.5

Working with referenced drawings When you create an AutoCAD MEP drawing, you often need to relate your

layout to an architectural drawing, such as a floor plan, a reflected ceiling plan, or an AutoCAD Architecture building model. You can begin with a drawing that contains the walls and other spatial elements that you need by attaching another drawing called a referenced drawing or xref. Xref are drawings that are linked to, and displayed in, the current drawing. Whenever you open a drawing, the software reloads the xref drawings attached to it so that changes made to the xref drawings are reflected in your building system drawing. For example, if you attach an architectural floor plan as an xref, and the architect subsequently changes the location of the building’s mechanical room, the changes to the architectural floor plan are automatically reflected in your building systems drawing the next time that you open it. You can also reload xrefs on demand and check for interferences between building system objects and structural members by applying interference detection highlighting to your drawing. There are 2 types of xrefs: attachment and overlay. Unlike an attached xref, an overlaid xref is not displayed when the drawing is itself attached or overlaid as an xref to another drawing—a process referred to as nesting xrefs. Overlaid xrefs are designed for data sharing in a network environment. By overlaying an xref, you can see how your drawing relates to the drawings of other groups without changing your drawing by attaching an xref. Changes made to an xref drawing, whether attached or overlaid, are displayed in your drawing when you open the drawing or reload the xref. Linking xrefs to your drawings is effective when creating design drawings and construction documents.

Design projects typically involve the coordination of many drawings, and sharing the content of those drawings is fundamental to efficient project management. Establishing standards for using xrefs helps you to use drawings optimally and minimize the need to re-create drawing content.

27

The following cite several advantages to using xrefs in AutoCAD MEP drawings:  You can reference an architectural drawing as a base for your mechanical, electrical, or plumbing drawings.  In addition, you are aware immediately of any changes to the architectural drawing because the changes are reflected when you open your drawing or reload the xref.  You can assemble master drawings from individual design drawings. For example, several people can work with different sections of a design for a large building (such as by floor or by wing), and the individual designs can be referenced into a master drawing.  You can attach drawings containing borders, title blocks, and other office standards for plotting as xrefs for easy maintenance.  You can choose not to load an xref if you do not need it as a reference. The xref does not use system resources when it is not loaded. [7]

28

System design 51Project description

5.1.1Geographical location

Site is located in university of Khartoum, Gamaa Avenue, south of El Gazafi hall between faculty of law and Building and Roads Research Institute.

5.1.2 Building components

The building consists of two floors, a ground floor, eastern and southern entrances. The total area of the building is about 1288.2 m2

The ground floor consists of:

1. A big hall has a capacity of 170 people. Hall (1).

2. Two halls have a capacity of 60 persons for each one. Hall (2) and Hall

(3). 3. Two offices, an office capacity are 3 persons.

4. An entrance hall. 5. Corridors. 6. Bathrooms.

The first floor consists of:

1. A big hall has a capacity of 150 people Hall (4).

2. Two halls have a capacity of 40 persons for each one. Hall (4) and Hall

(5). 3. Corridors. 4. Bathrooms.

29

The second floor consists of:

1. A big hall has a capacity of 500 people Hall (6). 2. Four offices, an office capacity are 3 people. 3. Corridors.

The table below (Table 5.1) summarizes the above mentioned information

Floor

Hall no.

No.

of Area

Purpose

peopl e

(m2)

Hall (1)

170

174.2

Lecture room

Hall (2)

60

88.8

Lecture room

Hall (3)

60

88.8

Lecture room

Office (1)

3

20.6

Office

Office (2)

3

20.6

Office

Hall (4)

250

158.4

Lecture room

Hall (5)

40

88.4

Lecture room

Ground floor

First floor

Hall (6)

40

88.4

Lecture room

Office (3)

3

22.6

office

Office (4)

3

22.6

office

Hall (7)

500

461

Lecture room

Office (5)

3

13.3

Office

Office (6)

3

13.3

Office

Office (7)

2

11.6

Office

Office (8)

2

11.6

Office

Second floor

30

5.2

Design Procedure

5.2.1 Specifying the project

We started with drawing management using project browser component and created the project by drawing the building plans since they were not drawn by ACAD MEP. Then using project navigator we defined building levels and divisions floor by floor.

5.2.2 Establishing project standards and space styles:

Typically, at the beginning of the project, we established ACAD MEP standards that guide the project design, enhance efficiency, automate repetition, and maintain consistency across our project drawings and construction documents.

Then we specified space styles from ACAD MEP standards, we then select ASHRAE 62.1 – 2004 and define space engineering styles (i.e. lightening load per area (25 W/m2), and equipment load per area (0.2 W/m2). After establishing project standards and space styles we made the following steps: 1. We specified spaces boundaries and that by using one of the analysis tools which is space generating tool. Then we specified space styles

for each space (office, lecture hall, lecture class, corridor). 2. After we generate spaces we add properties for each, basic properties like space name, space dimensions (overall space height, floor thickness, ceiling height, ceiling thickness, height above ceiling, and height below floor). Other properties and their description are explained in (Table 6.1).

31

The table below (Table 5.2) summarizes building properties and its description

Property

Description

Occupancy

We entered the number of occupants for the room. This value is used for calculating the required outdoor air flow dependingonthecodeand classification. If Occupancy is 0, the occupant density for the classification is used to calculate outside air.

Condition type

Condition

Type

Specify

how

to

condition the room.

Lighting Load

We entered the lighting load for the room.

We

override

that

value

by

entering a value for Lighting Load here (W/m2).

Equipment Load

We entered the equipment load for the room.

We

override

that

value

entering a value for equipment Load

by

here (W/m2).

Outside Air Flow

We can overrides the required air flow calculated

from

the

classification

take it. (Base color, base finish, base material,

Room finished objects

ceiling finish, ceiling material, etc).

3. Also we specified surface types, such as exterior walls (exposed to sun light), interior walls (treated as partitions) using the Space/Zone Manager tool.

32

or

4. After that we specify the north direction on the plan using geographic location tool (its options are either using Google earth or add it manually).

5.2.3 Creating zone styles Zones are used to group spaces together to represent an actual building zone that requires its own temperature control. So we configured a zone style for each space style we had configured previously. After that we added zones and attached spaces to zones, a zone can be a single space or more than one space controlled by a thermostat, then we specified design temperatures for zones. Finally we used space/zone manager tool to review space and zone configuration.

5.2.4 Exporting gbXML data After we modeled and configured spaces and zones we exported the data in gbXML format, this format is used in an external analysis tool to calculate heating and cooling loads for the building plan.

5.2.5 System Analysis Thermal load calculations are often considered one of the most important aspects in any HVAC system design. Accurate load calculations are needed to ensure proper system and equipment selection. A proper system/equipment selection can guarantee maximum performance and maintain desired comfort levels.

The computer software program that was utilized to perform the thermal load calculations was Loadsoft 6.0, which is a commercial and industrial HVAC (Heating, Ventilation, and Air Conditioning) load calculation

software

package

issued

by

Carmel

Software.

Load

calculations are based on radiant time series (RTS) method {ASHRAE

33

2001 Fundamentals}. This program generates a complete 24-hour building load profile of all systems selected. This feature is very useful when a complete system analysis is completed. Another feature is the ability of the program to provide an accurate hour-by-hour analysis for one complete year for each individual zone so that we may properly specify the correct size HVAC equipment (whether it is a packaged rooftop unit or a boiler). This program is geared specifically toward the HVAC engineer, architect, design/build mechanical contractor, and building maintenance supervisor.

5.2.5.B Analysis steps: 1. We imported the gbXML file to Loadsoft program and created a project in it. 2. We revised the imported data to the program (Loadsoft inputs).

3. We calculated the cooling load and required air flow; the results are exported to the ACAD MEP software using gbXML (Loadsoft outputs appendix (A)).

5.2.6 Importing the analyzed gbXML file:

In this step we imported the analyzed gbXML file that includes calculated load and air flow values for each zone. The imported data is added in the engineering data properties for each zone. After we imported calculations we specified values for outside air flow, supply air flow, and return air flow. We used this information when designing our HVAC

system.

34

5.2.7 Layout of the system

The system selected for the lecture halls, and rooms is a central chilled water system with combined central station air handling units (all air system - constant air volume) and fan coil units (all water system).

• The major components are: 1. Chiller. 2. Air handling units. 3. Ducts. 4. Diffusers. 5. Grilles.

6. Water pipes. Details of the selected components are mentioned in appendix (B). • The steps of layout of the system are as follows: 1. We started with placing ceiling diffusers and its elevation.

2. Then we placed the AHUs (for lecture rooms) and fan coils (for offices). 3. We sized duct layout while we were drafting (AutoCAD MEP uses equal friction method for sizing ducts).

4. We placed the chiller and drew piping works. • The system drawing sheets is in appendix (C).

35

Conclusion and recommendations___________________

In this project, AutoCAD MEP program, building information modeling (BIM) software, is used to design a central air conditioning system. Building engineering data have been exported from architectural plans, using gbXML format, to Loadsoft 6.0 software for cooling load analysis. The software obtained a total cooling load of 136.1 TOR.

The calculated cooling load was imported to the AutoCAD software which is used to design a central air conditioning system. The software analyzed the imported data and used it for duct sizing and equipment selection.

A central chilled water system air-conditioning system comprising an aircooled screw type chiller of capacity of 137 TOR, 10 air handling units with different capacities according to the cooling load, and 4 fan coils units complete with piping and ducting system was obtained. The layout of the complete airconditioning system was shown in Appendix (C).

61 Recommendations

1. We recommend that the roof material of the second floor (consists of sheet metal and for ceiling) be changed or been properly insulated since the cooling load value is too high. 2. Make this project an inter-disciplinary project; a design project done by an architect student, mechanical student, electrical, and civil students so that the full features of AutoCAD MEP and BIM concept can be utilized to produce a complete system design, make good decisions, and utilize green building concepts with

low emissions to the environment and lower cost.

36

3. The department is required to provide a full version of ACAD MEP, and the load calculation program (the analysis tool) to make use of its all features and capabilities.

37

References [1] Salah Ahmed Abdallah, Air conditioning course notes, university of Khartoum. 2] Walter T.Grondzic, Air conditioning system design manual, second edition. 3]

www.ashrae.org, An Introduction to building information modeling, 2009.

4] Previous resource. 5] Previous resource. 6] Autodesk Company, autocad_mep brochure, 2009. 7] Autodesk Company, AutoCAD MEP 2010 user’s guide, March 2009.

38

Appendix (A) Cooling load calculations results:

1. Ground floor:

Zone

Total area

Sensible

name

(m2)

Hall 1

174.2

51,614.2

Hall 2

88.8

Hall 3

Total

Summer

Total

L/s

tonnage

73,029.8

1,597.7

20.8

20,430.2

27,988.6

745.6

8.0

88.8

20,430.2

27,988.6

745.6

8.0

Office 001

22.6

3,093.9

3,497.5

212.6

1.0

Office 002

22.6

3,093.9

3,497.5

212.6

1.0

Total

Summer

Total

L/s

tonnage

1,345.5

18.1

cooling (W) cooling (W)

Total Tonnage : 38.8

2. First floor:

Zone

Total area

name

(m2)

Hall 4

158.4

Sensible

cooling (W) cooling (W) 44,760.0

63,656.1

Hall 5

88.4

14,322.7

19,361.7

554.7

5.5

Hall 6

88.4

14,322.7

19,361.7

554.7

5.5

Office 101

22.6

2,837.6

3,234.2

191.6

0.9

Office 102

22.6

2,837.6

3,234.2

191.6

0.9

Total Tonnage: 31.0

39

3. Second floor:

Zone

Total

Sensible

Total

Summer

Total

name

area (m2)

cooling

cooling

L/s

tonnage

(W)

(W)

Hall 7

461.0

161,643.9

221,166.0

5,506.6

63.0

Office

13.3

2,904.6

3,301.2

197.1

0.9

13.3

2,904.6

3,301.2

197.1

0.9

11.6

2,236.0

2,386.4

166.7

0.7

11.6

2,236.0

2,386.4

166.7

0.7

201 Office 202 Office 203 Office 204 Total Tonnage: 66.3

40

Appendix (B) Details of selected system components:

 Selected Chiller: • Name: PSC 155 • Capacity: 137 TOR

• Water flow rate: 330 GPM • Power input: 193.3 kW • Water pressure drop: 4.4 Psi.  The selected Air Handling Units:

Room

Model

Q cfm

No. of units

Hall 1

CM 48

4464

1

Hall 2

CM 24

1579.84

1

Hall 3

CM 24

1579.84

1

Hall 4

CM 38

2851.16

1

Hall 5

CM 15

1175.34

1

Hall 6

CM 15

1175.34

1

Hall 7

CM 38

11667.8

4

The selected Fan Coils units:

Room

Model

Q cfm

No. of units

Office 001

CB/CBP 5

450.287

1

Office 002

CB/CBP 5

450.287

1

Office 101

CB/CBP 5

450.287

1

Office 102

CB/CBP 5

450.287

1

Office 203

CB/CBD 3

353.217

1

Office 204

CB/CBD 3

353.217

1

41

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