Technology & Engineering
HVAC Systems
HVAC (Heating, Ventilation, and Air Conditioning) systems are designed to provide thermal comfort and acceptable indoor air quality. They regulate temperature, humidity, and air flow within buildings, ensuring a comfortable and healthy environment. HVAC systems are essential for maintaining optimal conditions in residential, commercial, and industrial spaces.
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12 Key excerpts on "HVAC Systems"
eBook - PDF- Barney L. Capehart, Wayne C. Turner, William J. Kennedy(Authors)
- 2020(Publication Date)
- River Publishers(Publisher)
Chapter 8 Heating, Ventilating, and Air Conditioning Systems 8.0 INTRODUCTION HVAC Systems—or Heating, Ventilating and Air-Conditioning sys-tems—are important systems to control the environment for people and equipment in our facilities. They are also major energy consumers, with cooling accounting for about 16% of the electrical energy use in a typi -cal residential building; and about 33% in a commercial or institutional building. HVAC Systems are also significant energy consumers in many manufacturing facilities. The primary purpose of the HVAC system is to provide and maintain a comfortable and safe environment within a facility for the occupants, equipment and processes being conducted. The HVAC system needs to be able to accomplish its purpose as both the inside environmental conditions and loads change, as well as when the out-side climatic conditions change. We would also like the HVAC system to accomplish its purpose with minimum energy use and minimum cost. The environmental factors that need to be controlled by the HVAC system for comfort and safety are: temperature, relative humidity, and air quality. Many facilities have HVAC Systems that were designed and in-stalled during periods of low energy costs; and these are often relatively expensive to operate because energy efficiency was not a consideration in the initial selection of the system. In addition, many HVAC Systems are designed to meet extreme load conditions of very hot or very cold weather; and they are then poorly matched to the average conditions that are experienced most of the time. Thus, improving the operation of the HVAC system provides many opportunities to save energy and reduce costs. In this chapter we describe how an HVAC system works, discuss the major components of HVAC Systems, analyze heating and cooling loads and ventilation requirements, and give methods for im-proving the energy efficiency and operation of existing HVAC Systems. 295
- Barney L. Capehart, William J. Kennedy, Wayne C. Turner(Authors)
- 2020(Publication Date)
- River Publishers(Publisher)
Chapter 8 Heating, Ventilating, and Air Conditioning 8.0 INTRODUCTION The heating, ventilating, and air conditioning (HVAC) system for a facility is the system of motors, ducts, fans, controls, and heat exchange units which delivers heated or cooled air to various parts of the facility. The purpose of the HVAC system is to add or remove heat and moisture and remove undesirable air components from the facility in order to maintain the desired environmental conditions for people, products or equipment. Providing acceptable indoor air quality is a critical function of the HVAC system, and air movement to remove odors, dust, pollen, etc. is necessary for comfort and health. It may also be necessary to air-condition an area to protect products or to meet unusual requirements such as those in a laboratory or a clean room. The HVAC system is responsible for a significant portion of the en -ergy use and energy cost in most residential and commercial buildings. Because many industrial facilities do not have heated or cooled produc-tion areas, HVAC energy use does not account for as great a portion of the total energy use for these facilities. However, a number of manufacturing plants are fully heated and air conditioned, and almost all industrial facili-ties have office areas that are heated and cooled. Thus, looking for ways to save on the energy costs of operating a facility’s HVAC system is an important part of any energy management program. Many facilities have HVAC Systems that were designed and installed during periods of low energy costs; these are often relatively expensive to operate because energy efficiency was not a consideration in the initial selection of the system. In addition, many HVAC Systems are designed to meet extreme load conditions of very hot or very cold weather; they are then poorly matched to the average conditions that are experienced most of the time.
eBook - PDF- Mohsen Sheikholeslami Kandelousi(Author)
- 2018(Publication Date)
- IntechOpen(Publisher)
Chapter 4 Types of HVAC Systems Shaimaa Seyam Additional information is available at the end of the chapter http://dx.doi.org/10.5772/intechopen.78942 Abstract HVAC Systems are milestones of building mechanical systems that provide thermal com-fort for occupants accompanied with indoor air quality. HVAC Systems can be classified into central and local systems according to multiple zones, location, and distribution. Primary HVAC equipment includes heating equipment, ventilation equipment, and cool-ing or air-conditioning equipment. Central HVAC Systems locate away from buildings in a central equipment room and deliver the conditioned air by a delivery ductwork system. Central HVAC Systems contain all-air, air-water, all-water systems. Two systems should be considered as central such as heating and cooling panels and water-source heat pumps. Local HVAC Systems can be located inside a conditioned zone or adjacent to it and no requirement for ductwork. Local systems include local heating, local air-conditioning, local ventilation, and split systems. Keywords: HVAC Systems, central HVAC Systems, local HVAC Systems, heating systems, air-conditioning systems 1. Introduction Heating, ventilation, and air conditioning (HVAC) system is designed to achieve the environ-mental requirements of the comfort of occupants and a process. HVAC Systems are more used in different types of buildings such as industrial, commercial, residential and institutional buildings. The main mission of HVAC system is to satisfy the thermal comfort of occupants by adjusting and changing the outdoor air conditions to the desired conditions of occupied buildings [1]. Depending on outdoor conditions, the outdoor air is drawn into the buildings and heated or cooled before it is distributed into the occupied spaces, then it is exhausted to the ambient air or reused in the system. The selection of HVAC © 2018 The Author(s). Licensee IntechOpen.
eBook - ePubElectrical Energy Efficiency
Technologies and Applications
- Angelo Baggini, Andreas Sumper(Authors)
- 2012(Publication Date)
- Wiley(Publisher)
11 Heat, Ventilation and Air Conditioning (HVAC) Roberto Villafáfila-Robles and Jaume SalomHeating, ventilation and air conditioning (HVAC) systems are responsible for meeting the requirements of an indoor environment, with regard to air temperature, humidity and air quality by heating or cooling the spaces. HVAC Systems represent an important part of the energy needs in industry and building sectors as it has been shown that such systems consume most of the energy in buildings, requiring almost 50% of the total energy demand [1].HVAC Systems are part of an energy chain for conditioning a space using different energy sources and converting them into thermal energy to meet the required level of comfort (see Figure 11.1 ). HVAC Systems use fuels and electricity; fossil fuels are the most common source for heating whereas electricity is the almost the only source for cooling. Apart from cooling, electricity is also used to move fluids to enable thermal energy to reach the required spaces.Fans and pumps used in thermal generation and transportation processes are the main electric energy consumers in an HVAC system. These are driven by electric motors and their energy efficiency is related to the use of power electronics-based drives, a topic that is principally covered in Chapter 9. Apart from optimizing the consumption of these electrical devices, there is a great potential for energy savings in order to decrease the energy consumption of HVAC Systems as a whole, as well as in heat and cold generators. This can be achieved by reducing the thermal energy demand by passive methods and the use of renewable energy sources to support the production of both heat and cold. This chapter deals mainly with energy saving measures to reduce the thermal energy demand in HVAC Systems and, as a consequence, achieve higher energy efficiency ratios.Heat transfer is the basis of the performance of an HVAC system in order to heat or cool a space. This transference is performed in a set of heat exchangers (evaporators and condensers) that can be on their own or a part of a cool or heat generation device. Heat exchange processes are studied using thermodynamics.
- Amritanshu Shukla, Atul Sharma, Amritanshu Shukla, Atul Sharma(Authors)
- 2018(Publication Date)
- CRC Press(Publisher)
Figure 9.2 . To accomplish this, the systems require transfer of the heat and moistness into and out of the air in addition to controlling the air pollutants level, by either directly removing them or by diluting them to tolerable levels. The heating systems increase the temperature in a space to compensate for heat losses concerning the interior space and outside. The ventilation systems supply air to space and extract contaminated air from it. The cooling of air available in the space is required to get the temperature down where heat gains have risen due to the presence of people, equipment, or the sun and are affecting human discomfort. HVAC Systems differ extensively in terms of size and the functions they perform. Some systems are large and central to the building services; these were probably designed when the building was initially commissioned and use ventilation to deliver heating and cooling. Other systems may provide heating through boilers and radiators, with some limited ventilation to provide fresh air or cooling to confident portions of the building such as conference rooms.In some cases, individual comfort cooling units have been added to a building to overcome a specific overheating problem that had not been thought of at the time of the original design. By considering HVAC Systems as a separate component rather than as an intermingling system, it would be informal to supervise the main area of energy wastage—that one element might influence one another, for example, it would be uneconomical to upsurge heating inside a building while the cooling system is combat to decrease temperatures. Consequently, it is worthwhile to look at how the components of an HVAC system interrelate with each other and fine tune every portion to save energy and money. Inappropriate design and indecorous installation of the HVAC system have an adverse effect on thermal comfort inside the buildings and on energy bills. Inappropriate design and installation of an HVAC system can intensely reduce the quality of air in a space. Poorly designed and poorly installed air circulation ducts can make unsafe conditions that may diminish the human comfort and degrade indoor air quality or even threaten the health of the homeowners.
eBook - PDF- Francis Shinskey(Author)
- 2012(Publication Date)
- Academic Press(Publisher)
Part IV ENERGY SYSTEMS IN BUILDINGS This page intentionally left blank Chapter 9 Heating, Ventilating, and Air-Conditioning Much of our fuel is consumed in attempting to provide a comfortable envi-ronment for the occupants of homes and buildings. The word attempting is used intentionally in that the conditions within which one must live and work are a frequent source of complaint for most of us. In many cases, the complaints are justifiable in that the heating, ventilating, and air-conditioning system—hereafter abbreviated HVAC system—is deficient in one or more respects. But comfort is also a subjective issue—conditions that are com-fortable to one individual may not be to others. Energy conservation in HVAC Systems must be approached from three directions. The equipment must be designed and configured for maximum efficiency: it must be controlled for minimum energy expenditure consistent with its objectives, but of equal importance is the proper conditioning of the occupants. As the seasons change, the metabolism of warm-blooded creatures slowly adjusts. An unseasonably cool day in the summer can cause more discomfort than a colder day in midwinter, because of the relative condition of blood viscosity and other parameters which affect metabolic heat transfer. In attempting to create uniform indoor conditions year round, the HVAC engineer is doing a disservice to the occupants. A person living in 60-65-°F 287 288 9. Heating, Ventilating, and Air-Conditioning surroundings will be less affected upon exposure to 0-25-°F outdoor tem-peratures than one living in a 70-75-°F environment. He will also be less susceptible to illness and use less fuel. Because energy usage depends heavily on behavior patterns, this chapter opens with a discussion on comfort—what it means and what it costs.
eBook - ePub- Frank Kreith, D. Yogi Goswami, Frank Kreith, D. Yogi Goswami(Authors)
- 2016(Publication Date)
- CRC Press(Publisher)
6Heating, Ventilating, and Air-Conditioning Control Systems
Bryan P. Rasmussen, Jan F. Kreider, David E. Claridge, and Charles H. CulpCONTENTS
6.1 Introduction: The Need for Control 6.2 Modes of Feedback Control 6.3 Basic Control Hardware 6.3.1 Pneumatic Systems 6.3.2 Electronic Control Systems 6.4 Basic Control System Design Considerations 6.4.1 Steam and Liquid Flow Control 6.4.2 Airflow Control 6.5 Example HVAC System Control Systems 6.5.1 Outside Air Control 6.5.2 Heating Control 6.5.3 Cooling Control 6.5.4 Complete Systems 6.5.5 Other Systems 6.6 Commissioning and Operation of Control Systems 6.6.1 Control Commissioning Case Study 6.6.1.1 Design Conditions 6.6.1.2 Optimization of AHU Operation 6.6.1.3 Optimization at the Terminal Box Level 6.6.1.4 Water Loop Optimization 6.6.1.5 Central Plant Measures 6.6.1.6 Results 6.6.2 Commissioning Existing Buildings 6.7 Advanced Control System Design Topics 6.7.1 Nonlinear Compensation 6.7.1.1 Case Study: Nonlinear Compensation for Air Conditioning Expansion Valves 6.7.2 Model Predictive Control 6.7.2.1 Case Study: MPC for Air Conditioning Expansion Valves 6.8 Summary References6.1 Introduction: The Need for Control
This chapter describes the essentials of control systems for heating, ventilating, and air conditioning (HVAC) of buildings designed for energy conserving operation. Of course, there are other renewable and energy conserving systems that require control. The principles described herein for buildings also apply with appropriate and obvious modification to these other systems. For further reference, the reader is referred to several standard references in the list at the end of this chapter.HVAC system controls are the information link between varying energy demands on a building’s primary and secondary systems and the (usually) approximately uniform demands for indoor environmental conditions. Without a properly functioning control system, the most expensive, most thoroughly designed HVAC system will be a failure. It simply will not control indoor conditions to provide comfort.
eBook - PDF- Cornelius T. Leondes(Author)
- 2000(Publication Date)
- CRC Press(Publisher)
Then conflict resolution for energy conservation and indoor air quality control is discussed. Finally a new control strategy, integrated intelligent control framework for HVAC processes is proposed. 4,2. BACKGROUND OF HVAC Systems AND OPERATIONS It is important for readers to understand the HVAC process before discussing the research project. Therefore, a description concerning HVAC system structures and air handling processes as well as control schemes will be presented. In addition, the problems with the HVAC conventional control strategies will be discussed. 4.2.1. System Structure and Classification There exist many types of HVAC Systems and various air handling equipment to meet the requirements for all kinds of buildings and weather. The system entity structure for HVAC Systems is demonstrated in Figure 1, which con tains decomposition, coupling and taxonomy information. Most residential or office buildings only require temperature conditioning, whereas some industrial environment need to condition both temperature and humidity. A single zone system sets all conditioned rooms at the same temperature and humidity, but a multizone system sets different indoor parameters for the conditioned rooms. Air washer and cooler both are used to cool and dehumidify air, which are chosen by the HVAC system designer depending on the weather and other factors. For a large commercial building, terminal controller or a distributed control system may be required. In this research project, we are only concerned about central HVAC Systems. There exists a total of sixteen types of central HVAC Systems (Figure 1), which may be classified as follows: • TSC: conditioning temperature, single zone and constant air volume system. Outside air is mixed with return air, then filtered, and heated or cooled to meet supply air requirement. A constant air volume fan supplies processed air to rooms. INTELLIGENT HVAC Systems 203 Figure 1. Structure classification for HVAC Systems.
eBook - PDF- Frank Kreith, D. Yogi Goswami, Frank Kreith, D. Yogi Goswami(Authors)
- 2016(Publication Date)
- CRC Press(Publisher)
HVAC system controls are the information link between varying energy demands on a building’s primary and secondary systems and the (usually) approximately uniform demands for indoor environmental conditions. Without a properly functioning control system, the most expensive, most thoroughly designed HVAC system will be a failure. It simply will not control indoor conditions to provide comfort. The HVAC control system must • Sustain a comfortable building interior environment • Maintain acceptable indoor air quality • Be as simple and inexpensive as possible and yet meet HVAC system operation criteria reliably for the system lifetime • Result in efficient HVAC system operation under all conditions • Be commissioned, including the building, equipment, and control systems • Be fully documented, so that the building staff successfully operates and main- tains the HVAC system A considerable challenge is presented to the HVAC system designer to design a control system that is energy efficient and reliable. Inadequate control system design, inadequate commissioning, and inadequate documentation and training for the building staff often create problems and poor operational control of HVAC Systems. This chapter develops the basics of HVAC control and follows through with the operational needs for successfully maintained operation. The reader is encouraged to review the following references on the subject: ASHRAE (2002, 2003, 2004, 2005), Haines (1987), Honeywell (1988), Levine (1996), Sauer et al. (2001), Stein and Reynolds (2000), and Tao and Janis (2005). To achieve proper control based on the control system design, the HVAC system must be designed correctly and then constructed, calibrated, and commissioned according to the mechanical and electrical systems drawings. These must include properly sized primary and secondary systems.
- Jan F. Kreider(Author)
- 2000(Publication Date)
- CRC Press(Publisher)
4 -1 0-8493-9584-4/01/$0.00+$.50 © 2001 by CRC Press LLC 4 HVAC Equipment and Systems 4.1 Heating Systems ................................................................. 4 -1 Natural Gas and Fuel Oil-Fired Equipment • Boilers • Service Hot Water • Electric Resistance Heating • Electric Heat Pumps • Low Temperature Radiant Heating • Solar Heating 4.2 Air Conditioning Systems ............................................... 4 -29 Vapor Compression Cycle • Refrigerants Use and Selection • Chilled Water Systems • Packaged Equipment • Evaporative Cooling 4.3 Ventilation and Air Handling Systems ........................... 4 -67 Anatomy of Air Handling Systems • Coils • Fans • Ducts • Terminal Units • Diffusers • Air Handling System Control • Secondary Air System Design • Air System Commissioning and Operation • Definition of Terms 4.4 Electrical Systems .......................................................... 4 -107 Review of Basics • Electrical Motors • Lighting Systems • Electrical Distribution Systems • Power Quality • Summary 4.1 Heating Systems Jan F. Kreider This chapter discusses equipment used for producing heat from fossil fuels, electricity, or solar power. The emphasis is on design-oriented information, including system characteristics, operating efficiency, the significance of part load characteristics, and criteria for selecting from among the vast array of heat producing equipment available. The heating plants discussed in this chapter are often called the primary systems . Systems intended to distribute heat produced by the primary systems are called secondary systems and include ducts and pipes, fans and pumps, terminal devices, and auxiliary components. Such secondary systems for heating and cooling are described in Chapter 4.3. The terms primary and secondary are equivalent to the terms plant and system used by some building analysts and HVAC system modelers.
- John W. Mitchell, James E. Braun(Authors)
- 2014(Publication Date)
- Wiley(Publisher)
Although the control system is often specified at the end of the design, it is important to be aware of the possibilities and capabilities of the management system during the design. With a sophisticated control system, many design options that enhance performance may be feasible. Summary of the Example Design Table 21.1 provides the basic information for the overall HVAC system design. It would allow the design engineer to begin a preliminary layout for the equipment. Further, the building owner might desire to reevaluate some of the decisions made in this preliminary design, such as the choice of a packaged unit or a built-up system. As can be seen in the table, there are tradeoffs. The packaged system is less expensive with fewer components and requires less maintenance, but the installed power is much higher (a total 132 kW) than that for the built-up system (75 kW). The energy costs for the packaged system would also be considerably higher. Further decisions would be needed on the details of the air distribution system (ducts, diffusers, etc.) and the water distribution system (piping, perimeter heat exchangers). The exact equipment would need to be selected. Although many more decisions would be needed, this overall evaluation would allow the design to proceed. 21.2 Design Methodology 561 21.3 LIFE-CYCLE COST The Life-Cycle Cost (LCC) of an HVAC system is the present worth of all of the owning and operating costs over the lifetime of the system. It includes all of the equipment and the operating costs and accounts for the effect of interest.
eBook - PDF- Stephan A. Roosa, Steve Doty, Wayne C. Turner(Authors)
- 2020(Publication Date)
- River Publishers(Publisher)
CAV and VAV reheat systems are frequently used to condition spaces with extremely rigid requirements for humidity control, such as museums, printing plants, textile mills, and industrial process settings. Energy management professionals have many opportunities in most facilities to develop ECOs which reheat energy consumption. 10.5.4.4 Single Zone Systems The single duct, single-zone system is the sim-plest of the all-air HVAC Systems. When connected to a central heating and cooling plant, it is one of the most energy-efficient systems and one of the least expensive to install. It uses a minimum of distribution fan energy since equipment is typically located within or immedi-ately adjacent to the area that it conditions. The system is directly controlled by a zone temperature sensor, which adjusts to provide cooling or heating to maintain space temperature and humidity requirements. Single zone systems can provide conditioned spac-es with either cooling or heating or both. These systems can be configured to operate in a heating, cooling, fan only, or fan off control sequence, or in a reheat control sequence. Single zone systems may be designed to in-troduce outdoor air into the space. The outdoor air pro-vided may only meet the minimum outdoor air require-ments, or the system may have the capability to provide the unit's entire airflow capacity using outside air when ambient conditions permit. Applications of single-zone systems are large spaces with fairly uniform loads, such as retail stores, public assembly spaces, exhibit halls, auditoriums, lec-ture halls, warehouse spaces and arenas. 10.5.4.5 Multiple Zone Systems Multiple zone HVAC Systems function similar to single zone systems, with the exception that the tem-peratures of individual zones are controlled by a zone temperature sensor which adjusts the volume and tem-perature of air discharged into the space. This arrange-ment allows a high degree of local temperature control at a moderate cost.
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