File Name: heat ventilation and air conditioning system .zip
Metrics details. In the face of climate change, the protection of vulnerable patients from extreme climatic conditions is of growing interest to the healthcare sector and governments.
- Heating, ventilation and air conditioning (HVAC) in intensive care unit
- Types of HVAC Systems
- Chapter 12: Heating, Air Conditioning, and Ventilating
Heating, ventilation and air conditioning (HVAC) in intensive care unit
HVAC systems are milestones of building mechanical systems that provide thermal comfort 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 cooling 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. HVAC System. Heating, ventilation, and air conditioning HVAC system is designed to achieve the environmental 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 systems in a given building will depend on the climate, the age of the building, the individual preferences of the owner of the building and a designer of a project, the project budget, the architectural design of the buildings [ 1 ].
HVAC systems can be classified according to necessary processes and distribution process [ 2 ]. The required processes include the heating process, the cooling process, and ventilation process. Other processes can be added such as humidification and dehumidification process. These process can be achieved by using suitable HVAC equipment such as heating systems, air-conditioning systems, ventilation fans, and dehumidifiers.
The HVAC systems need the distribution system to deliver the required amount of air with the desired environmental condition.
The distribution system mainly varies according to the refrigerant type and the delivering method such as air handling equipment, fan coils, air ducts, and water pipes. System selection depends on three main factors including the building configuration, the climate conditions, and the owner desire [ 2 ]. The design engineer is responsible for considering various systems and recommending more than one system to meet the goal and satisfy the owner of a building.
Some criteria can be considered such as climate change e. However, the selection of a system has some constraints that must be determined. These constraints include the available capacity according to standards, building configuration, available space, construction budget, the available utility source, heating and cooling building loads. The basic components or equipment of an HVAC system that delivers conditioned air to satisfy thermal comfort of space and occupants and the achieve the indoor air quality are listed below [ 3 ]: Mixed-air plenum and outdoor air control.
The major classification of HVAC systems is central system and decentralized or local system. Types of a system depend on addressing the primary equipment location to be centralized as conditioning entire building as a whole unit or decentralized as separately conditioning a specific zone as part of a building. Therefore, the air and water distribution system should be designed based on system classification and the location of primary equipment. The criteria as mentioned above should also be applied in selecting between two systems.
An equipment room is located outside the conditioned area, or adjacent to or remote from the building. Installing secondary equipment for the air and water distribution which requires additional cost. Four requirements are the bases for any HVAC systems [ 4 ]. Primary equipment includes heating equipment such as steam boilers and hot water boilers to heat buildings or spaces, air delivery equipment as packaged equipment to deliver conditioned ventilation air by using centrifugal fans, axial fans, and plug or plenum fans, and refrigeration equipment that delivers cooled or conditioned air into space.
It includes cooling coils based on water from water chillers or refrigerants from a refrigeration process. Space requirement is essential in shaping an HVAC system to be central or local. It is preferable to be centrally located in the building to reduce the long duct, pipe, and conduit runs and sizes, to simplify shaft layouts, and centralized maintenance and operation.
HVAC facilities: heating equipment and refrigeration equipment require many facilities to perform their primary tasks of heating and cooling the building. The heating equipment requires boiler units, pumps, heat exchangers, pressure-reducing equipment, control air compressors, and miscellaneous equipment, while the refrigeration equipment requires water chillers or cooling water towers for large buildings, condenser water pumps, heat exchangers, air-conditioning equipment, control air compressors, and miscellaneous equipment.
The design of equipment rooms to host both pieces of equipment should consider the size and the weight of equipment, the installation and maintenance of equipment, and the applicable regulations to combustion air and ventilation air criteria. Fan rooms contain the HVAC fan equipment and other miscellaneous equipment. The rooms should consider the size of the installation and removal of fan shafts and coils, the replacement, and maintenance. The size of fans depends on the required air flow rate to condition the building, and it can be centralized or localized based on the availability, location, and cost.
It is preferable to have easy access to outdoor air. Vertical shaft: provide space for air distribution and water and steam pipe distribution. The air distribution contains HVAC supply air, exhaust air, and return air ductwork. Pipe distribution includes hot water, chilled water, condenser water, and steam supply, and condenser return. Equipment access: the equipment room must allow the movement of large, heavy equipment during the installation, replacement, and maintenance.
Air distribution considers ductwork that delivers the conditioned air to the desired area in a direct, quiet, and economical way as possible. Air distribution includes air terminal units such as grilles and diffusers to deliver supply air into a space at low velocity; fan-powered terminal units, which uses an integral fan to ensure the supply air to the space; variable air volume terminal units, which deliver variable amount of air into the space; all-air induction terminal units, which controls the primary air, induces return air, and distributes the mixed air into a space; and air-water induction terminal units, which contains a coil in the induction air stream.
All the ductwork and piping should be insulated to prevent heat loss and save building energy. It is also recommended that buildings should have enough ceiling spaces to host ductwork in the suspended ceiling and floor slab, and can be used as a return air plenum to reduce the return ductwork.
The piping system is used to deliver refrigerant, hot water, cooled water, steam, gas, and condensate to and from HVAC equipment in a direct, quiet and affordable way. Piping systems can be divided into two parts: the piping in the central plant equipment room and the delivery piping.
HVAC piping may or may not be insulated based on existing code criteria. A central HVAC system may serve one or more thermal zones, and its major equipment is located outside of the served zone s in a suitable central location whether inside, on top, or adjacent to the building [ 4 , 5 ]. Central systems must condition zones with their equivalent thermal load.
Central HVAC systems will have as several control points such as thermostats for each zone. The thermal energy transfer medium can be air or water or both, which represent as all-air systems, air-water systems, all-water systems. Also, central systems include water-source heat pumps and heating and cooling panels. All of these subsystems are discussed below. The thermal energy transfer medium through the building delivery systems is air.
All-air systems can be sub-classified based on the zone as single zone and multizone, airflow rate for each zone as constant air volume and variable air volume, terminal reheat, and dual duct [ 5 ]. A single zone system consists of an air handling unit, a heat source and cooling source, distribution ductwork, and appropriate delivery devices.
The air handling units can be wholly integrated where heat and cooling sources are available or separate where heat and cooling source are detached. The integrated package is most-commonly a rooftop unit and connected to ductwork to deliver the conditioned air into several spaces with the same thermal zone.
The main advantage of single zone systems is simplicity in design and maintenance and low first cost compared to other systems. However, its main disadvantage is serving a single thermal zone when improperly applied. Control may be either modulating or on—off to meet the required thermal load of the single zone.
This can be achieved by adjusting the output of heating and cooling source within the packaged unit. Although few buildings can be a single thermal zone, a single zone can be found in several applications.
One family residential buildings can be treated as single zone systems, while other types of residential buildings can include different thermal energy based on the occupation and building structure. Movements of occupants affect the thermal load of the building, which results in dividing the building into several single zones to provide the required environmental condition.
This can be observed in larger residences, where two or more single zone systems may be used to provide thermal zoning. In low-rise apartments, each apartment unit may be conditioned by a separate single zone system. Many sizeable single story buildings such as supermarkets, discount stores, can be effectively conditioned by a series of single zone systems.
Large office buildings are sometimes conditioned by a series of separate single zone systems. In a multi-zone all-air system, individual supply air ducts are provided for each zone in a building. Cold air and hot or return air are mixed at the air handling unit to achieve the thermal requirement of each zone.
Multi-zone all-air system consists of an air handling unit with parallel flow paths through cooling coils and heating coils and internal mixing dampers. It is recommended that one multi-zone serve a maximum of 12 zones because of physical restrictions on duct connections and damper size. If more zones are required, additional air handlers may be used.
The advantage of the multi-zone system is to adequately condition several zones without energy waste associated with a terminal reheat system. However, leakage between the decks of air handler may reduce energy efficiency. The main disadvantage is the need for multiple supply air ducts to serve multiple zones. This can be performed by adding heating equipment, such as hot water coil or electric coil, to the downstream of the supply air from air handling units near each zone.
Each zone is controlled by a thermostat to adjust the heat output of heating equipment to meet the thermal condition. The supply air from air handling units is cooled to the lowest cooling point, and the terminal reheat adds the required heating load. The advantage of terminal reheat is flexible and can be installed or removed to accommodate changes in zones, which provides better control of the thermal conditions in multiple zones.
However, the design of terminal reheat is not energy-efficient system because a significant amount of extremely cooling air is not regularly needed in zones, which can be considered as waste energy. Therefore, energy codes and standards regulate the use of reheat systems.
The dual duct all-air system is a terminal-controlled modification of the multi-zone concept. These air streams are distributed throughout the area served by the air handling unit in separate and parallel ducts. Each zone has a terminal mixing box controlled by zone thermostat to adjust the supply air temperature by mix the supply cold and hot air. This type of system will minimize the disadvantages of previous systems and become more flexible by using terminal control.
Some spaces require different airflow of supply air due to the changes in thermal loads. Therefore, a variable-air-volume VAV all-air system is the suitable solution for achieving thermal comfort. The previous four types of all-air systems are constant volume systems. The temperature of supply air of each zone is controlled by manipulating the supply air flow rate.
Types of HVAC Systems
First and foremost, HVAC stands for heating, ventilation, and air conditioning. This system provides heating and cooling to residential and commercial buildings. You can find HVAC systems anywhere from single-family homes to submarines where they provide the means for environmental comfort. Becoming more and more popular in new construction, these systems use fresh air from outdoors to provide high indoor air quality. This provides a better quality of air indoors and involves the removal of moisture, smoke, odors, heat, dust, airborne bacteria, carbon dioxide, and other gases as well as temperature control and oxygen replenishment.
Heating, ventilation, and air conditioning HVAC  is the technology of indoor and vehicular environmental comfort. Its goal is to provide thermal comfort and acceptable indoor air quality. HVAC system design is a subdiscipline of mechanical engineering , based on the principles of thermodynamics , fluid mechanics and heat transfer. HVAC is an important part of residential structures such as single family homes, apartment buildings, hotels and senior living facilities, medium to large industrial and office buildings such as skyscrapers and hospitals, vehicles such as cars, trains, airplanes, ships and submarines, and in marine environments, where safe and healthy building conditions are regulated with respect to temperature and humidity, using fresh air from outdoors. Ventilating or ventilation the "V" in HVAC is the process of exchanging or replacing air in any space to provide high indoor air quality which involves temperature control, oxygen replenishment, and removal of moisture, odors, smoke, heat, dust, airborne bacteria, carbon dioxide, and other gases. Ventilation removes unpleasant smells and excessive moisture, introduces outside air, keeps interior building air circulating, and prevents stagnation of the interior air.
HVAC systems are milestones of building mechanical systems that provide thermal comfort 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 cooling 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.
Superstructure Heating, Cooling, and Ventilation .. 7. 6. Coordination of HVAC and Fire Detection and Alarm System
Chapter 12: Heating, Air Conditioning, and Ventilating
The main purposes of a Heating, Ventilation and Air-Conditioning HVAC system are to help maintain good indoor air quality through adequate ventilation with filtration and provide thermal comfort. HVAC systems are among the largest energy consumers in schools. The choice and design of the HVAC system can also affect many other high performance goals, including water consumption water cooled air conditioning equipment and acoustics.
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