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27-11-2010, 09:58 AM
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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.
The project and implimentation goal
This project and implimentation 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.
Air-conditioning and Air-conditioning System Design
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.
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.
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.
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.
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.
• 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.
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.
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
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.
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.
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.
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