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 Design2.1 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.

2.3.2 Advantages 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 all-air

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.

2.4 Decentralized 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 air-

conditioning 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.

oDecentralized systems tend to be distributed systems providing greater collective reliability than do centralized systems.

2.4.2 Disadvantages 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.

2.5.3 Disadvantages of All air systems:

All-air systems use significant amounts of energy to move air (approximately 40% of all-air 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.

2.7 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 cross-contamination 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 projects3.1 BIM Terminology and Definitions

The ASHRAE (American Society of Heating, Refrigerating and Air-

Conditioning 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 minimizing

environmental impacts.

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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, en-

ergy 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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3.7 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 real-world 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 applications to better coordinate with your extended team.

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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 concepts4.1 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.

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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.

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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]

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System design5.1 Project description

5.1.1 Geographical 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.

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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

people (m2)Hall (1) 170 174.2 Lecture room

Hall (2) 60 88.8 Lecture room

Ground floor 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

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

Second floor Office (6) 3 13.3 Office

Office (7) 2 11.6 Office

Office (8) 2 11.6 Office

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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).

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

Property DescriptionOccupancy We entered the number of occupants

for the room. This value is used forcalculating the required outdoor air flowdependingonthecodeandclassification. If Occupancy is 0, theoccupant density for the classification isused to calculate outside air.

Condition type Condition Type Specify how tocondition the room.

Lighting Load We entered the lighting load for theroom. We override that value byentering a value for Lighting Load here(W/m2).

Equipment Load We entered the equipment load for theroom. We override that value byentering a value for equipment Loadhere (W/m2).

Outside Air Flow We can overrides the required air flowcalculated from the classification ortake it.

Room finished objects (Base color, base finish, base material,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.

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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.

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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).

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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 air-

cooled 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 air-

conditioning system was shown in Appendix (C).

6.1 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.

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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.

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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.

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Appendix (A)Cooling load calculations results:

1. Ground floor:

Zone Total area Sensible Total Summer Total

name (m2) cooling (W) cooling (W) L/s tonnageHall 1 174.2 51,614.2 73,029.8 1,597.7 20.8

Hall 2 88.8 20,430.2 27,988.6 745.6 8.0

Hall 3 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 Tonnage : 38.8

2. First floor:

Zone Total area Sensible Total Summer Total

name (m2) cooling (W) cooling (W) L/s tonnageHall 4 158.4 44,760.0 63,656.1 1,345.5 18.1

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

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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

201

Office 13.3 2,904.6 3,301.2 197.1 0.9

202

Office 11.6 2,236.0 2,386.4 166.7 0.7

203

Office 11.6 2,236.0 2,386.4 166.7 0.7

204

Total Tonnage: 66.3

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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

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