Heating, ventilation, and air conditioning HVAC systems are installed in millions of homes across the world and provide a simple, user-friendly way to get their living space as comfortable as possible. And while these units can be easily controlled from a few buttons and knobs on a thermostat, the science and engineering behind your comfort is something you might need to know in case repairs or replacements are in order. This article dives into the function, operation, and anatomy of HVAC systems. HVAC stands for heating, ventilation, and air conditioning. These systems can take on many shapes and forms, but they must share each of these three functions to be considered an HVAC system.
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Heating, ventilation and air conditioning HVAC systems supply fresh air and condition the indoor air temperature and humidity of a building.
Therefore, HVAC is a key component of climate change mitigation potential in the building sector. HVAC systems normally consist of components to supply, filter, heat, cool and distribute the conditioned air into targeted interior spaces. This means the high-efficiency of one component can operate at expense of the others. As an example, take two categories of HVAC systems: high- and low-pressure systems. These systems have smaller ducts and require less space to house the duct system, but require more fan energy to drive the air.
The high-velocity airflow has its speed reduced at the terminal outlets to avoid a strong flow of air that creates discomfort for occupants, known as draught. Low-pressure systems conduct supply airflow at low velocities and require larger duct spaces. In this case, HVAC system efficiency depends on the selection and integration of the key components that suit a specific building and its context. These key components, or sub-systems, are heating, cooling and ventilation. These components have constantly undergone technological upgrades to improve their efficiency.
Boilers are usually used to generate hot water or steam using coal, diesel or natural gas. Conventional boilers — i. Condensing boilers are often fired with natural gas — a less polluting energy source. They are more efficient at removing the heat from the flue gases, and can be operated more efficiently than the conventional boilers at part-load Graham, Heat pump technologies are developed as an alternative to fossil-fuel-based boilers.
The technologies extract heat from warmer underground earth, air or sub-surface water during winter months, in temperate regions, to condition the temperature for indoor usage.
Reversing the above cycle during summer months, a heat pump extracts heat from indoors to outdoors to provide cooler indoor temperature. Chillers are used to produce cool water, which is then pumped to air handling units to cool the air. Chillers use either mechanical compression or an absorption process. Among mechanical compression chillers, centrifugal chillers are the most efficient for large-capacity operation, such as in large office buildings or retail complexes.
Absorption chillers, on the other hand, produce cool water through heat sources, i. In this way, absorption chillers enable the use of hot water tapped from solar thermal systems for air conditioning. Condensers are required in chiller systems, which reject heat to the environment and allow chillers to continuously remove heat from indoor conditioned spaces. They can be air-cooled or water-cooled.
Aircooled condensers are used for small-scale application, whereas water-cooled condensers are more costly but much more efficient for large-scale systems and are usually seen in large building complexes. Water-cooled condensers require cooling towers, usually located on the rooftops of buildings, to reject heat from condensers into the environment. Energy recovery installed in the mechanical ventilation system can help save energy. Air conditioned air fume cupboards can be use to cool incoming replaced air through a heat exchanger instead of being discharged directly outdoors.
Desiccant wheels have the ability to dehumidify the air while carrying out heat exchange, and are also suitable for hot and humid regions in the tropical belt. An automatic condenser tube cleaning system allows water-cooled heat exchange type chillers to maintain good performance through constant cleaning of the condenser tubes. The system circulates cleaning sponge balls into the condenser tubes, which are then rinsed in a ball receptacle through swirling motions Hydroball, Variable Air Volume VAV systems vary the amount of air intake to a room while keeping the air temperature constant.
This strategy is different from the Constant Air Volume CAV systems, which supply a constant rate of air intake while varying the temperature of the supply air.
Displacement ventilation typically supplies conditioned air from a raised floor system through a series of adjustable floor-mounted registers. As a result, displacement ventilation helps reduce energy used for higher fan speed to drive cooled air down from the ceiling like conventional ceiling-mounted air outlets do.
Furthermore, displacement ventilation can provide the same level of comfort with a significantly higher supply air temperature, i. One of the major barriers to implementing highly efficient HVAC systems is the installation of oversized systems that result in inefficient part-load most of the time.
In order to break the vicious circle created by this conventional practice, training workshops to upgrade professional knowledge will be necessary. Furthermore, well designed demonstration building projects that are equipped with highly efficient HVAC systems and show a proven records of energy saving and good thermal comfort performance, will be a good catalyst.
Setting minimal performances in building codes provides an institutional setting for the design and implementation of more efficient HVAC systems in buildings. Therefore, supporting the development of ESCOs and energy performance contracting business will indirectly nurture the implementation of highly efficient HVAC systems. Highly efficient HVAC systems require great efforts during the design stage for coordination, selection, and design for best fit integration of HVAC components to be suitable for a specific context and unique parameters of a building.
Zone control is the first and easiest strategy for a highly efficient HVAC including heating and cooling system. This way, users are able to adjust the room temperature independently to suit their thermal comfort level. Proper sizing of components. This is a simple concept but is hard to achieve. The conventional practice of mechanical and electrical engineers is to base sizing on the worst-case scenario for simultaneous load demands e.
However, in recent years, empirical data from building science research has proven that oversized equipment operates less efficiently and costs more. Location of fresh air intake has to be carefully considered and placed away from any potential pollution and odour, such as from basement garage floor or directly facing garbage collection points.
It is also not desirable to locate an air intake close to an air exhaust outlet. In this way, incoming air to the HVAC systems is fresh and of good quality. Shifting peak load in cooling systems to utilise off-peak electricity at night or solar energy during the day to generate thermal energy, e.
This will result in lower electricity peak demand and will reduce energy costs. Heat delivery in heating systems to the occupancy spaces includes two common methods, hydronic heat and forced hot air. Heat is radiated from the hot water to warm the occupancy spaces. The advantages of these systems is quietness, and that heat can be distributed evenly.
In forced hot air systems, heated water is circulated through a fan-coil unit to warm the heat exchanger. Air from inside the building is then circulated and is passed through the warm heat exchanger.
Finally, the warmed air is delivered to the occupancy space s. The warm air outlets are recommended to be located on the floor or lower wall of the occupancy spaces.
Ceiling mounted outlets work against the natural buoyancy of warm air, and thus requires additional energy for higher fan speeds to drive the warm air down to the human level.
Global demand for general HVAC equipment has been reported to increase by 6. With growing worldwide demand, highly efficient HVAC systems stand to enjoy good market prospects. Moreover, rising oil and electricity prices, coupled with wider public awareness of being energy efficient, will help to push the demand toward the highly efficient section of the market. The IPCC also highlights the trend of higher demand for individual apartment and home air conditioning in developing countries, reaching even higher levels in developed countries Levine et al.
This trend is evident in the production trends of such air conditioning units — from This is because in China, many buildings and factories already have diesel generators and fuel storage tanks to address blackouts. Therefore, it makes more economic sense for building owners to install absorption chillers than to install those that run on electricity Bradsher, However, the take up rate of displacement ventilation in North America has been much lower, i.
Due to the high percentage of energy consumption, highly efficient HVAC systems contribute to both economic and environmental development. With the right government regulations and support, ESCO businesses could prosper in this area, which in turn stimulate more market demand and the adoption of highly efficient HVAC systems. Highly efficient HVAC systems deliver cleaner and better quality air to the indoor environment — i.
This, in turn, contributes to better indoor living and working environments, reduction of sick building syndrome, and better living comfort and productivity. As highly efficient HVAC systems can be achieved in many ways, depending on the nature of the buildings, their financial requirements vary. If highly efficient HVAC systems are designed during the design stage, additional investment costs may be minimal in many cases, thanks to that the equipment cost is reduced from proper sizing instead of oversizing of the equipment.
Additional investment costs are sometimes required for additional HVAC subsystems for example, from installation of automatic condenser tube cleaning systems, larger piping areas or ice storage systems. In general, the increased investment costs for highly efficient HVAC systems will be recouped from energy savings and reduced maintenance costs. The following are some indicative investment costs for highly efficient HVAC sub-systems in Singapore:.
Skip to main content. Connecting countries to climate technology solutions. User menu About us Contact Newsletter Login. Heating- Ventilation and Air Conditioning. Energy efficiency. Technology group:. The built environment. Heating - Ventilation and Air Conditioning. Introduction HVAC systems normally consist of components to supply, filter, heat, cool and distribute the conditioned air into targeted interior spaces.
Heating systems Boilers are usually used to generate hot water or steam using coal, diesel or natural gas. Cooling systems Chillers are used to produce cool water, which is then pumped to air handling units to cool the air.
Air conditioning, or cooling, is more complicated than heating. Instead of using energy to create heat, air conditioners use energy to take heat away. The most common air conditioning system uses a compressor cycle similar to the one used by your refrigerator to transfer heat from your house to the outdoors. Picture your house as a refrigerator. There is a compressor on the outside filled with a special fluid called a refrigerant.
Types of Cooling Systems
Introduction The quotes below provide a profound lesson in the need for housing to provide protection from both the heat and cold. The bitter cold that gripped the Northeast through the weekend and iced over roads was blamed for at least three deaths, including that of a Philadelphia man found inside a home without heat. Heating and cooling are not merely a matter of comfort, but of survival. Both very cold and very hot temperatures can threaten health. Excessive exposure to heat is referred to as heat stress and excessive exposure to cold is referred to as cold stress. In a very hot environment, the most serious health risk is heat stroke.
Chapter 12: Heating, Air Conditioning, and Ventilating
Central air conditioners circulate cool air through a system of supply and return ducts. Supply ducts and registers i. This cooled air becomes warmer as it circulates through the home; then it flows back to the central air conditioner through return ducts and registers. Air conditioners help to dehumidify the incoming air, but in extremely humid climates or in cases where the air conditioner is oversized, it may not achieve a low humidity. Running a dehumidifier in your air conditioned home will increase your energy use, both for the dehumidifier itself and because the air conditioner will require more energy to cool your house. If you have a central air system in your home, set the fan to shut off at the same time as the compressor, which is usually done by setting the "auto" mode on the fan setting.SEE VIDEO BY TOPIC: How does your AIR CONDITIONER work?
James Braun is a professor of Mechanical Engineering at Purdue. He received his Ph. D from the University of Wisconsin in HVAC is his primary research area. John W. Mitchell , James E. Heating Ventilation and Air Conditioning by J. Mitchell and J. Braun provides foundational knowledge for the behavior and analysis of HVAC systems and related devices. The emphasis of this text is on the application of engineering principles that features tight integration of physical descriptions with a software program that allows performance to be directly calculated, with results that provide insight into actual behavior.
Heating, ventilation, and air conditioning
It includes heating, cooling, humidifying, dehumidifying, filtering, and distribution of air at suitable conditions for the maintenance of human comfort or for the undertaking of a particular process. In order to design an air conditioning system the appropriate heating, cooling, and other environmental loads must first be calculated and a variety of other factors such as initial and running costs, plant room and distribution space, control requirements etc. In practice, there are a wide variety of air conditioning systems available and selection is often dictated by factors other than the air conditioning loads.
Last updated: August 12, W hat's the best way to cool down your kitchen on a hot summer's day? If your immediate answer is "Open the refrigerator door," you're way off target. Every bit of heat a refrigerator sucks in through its cool box is pumped straight out of the metal fins at the back. If anything, because of the sheer inefficiency of the machine, you'll make the room even hotter. But using a refrigerator to cool a home isn't such a mad idea as it might seem: with a few slight modifications, it's almost exactly how an air conditioner works. Let's take a closer look! Photo: A typical air conditioner unit outside a restaurant. This is the fan that blows away the hot air.
Heating- Ventilation and Air Conditioning
HVAC stands for Heating, Ventilating, and Air Conditioning, and HVAC systems are, effectively, everything from your air conditioner at home to the large systems used in industrial complexes and apartment blocks. A good HVAC system aims to provide thermal control and indoor comfort, and one that is designed using the principles of thermodynamics, fluid mechanics, and heat transfer. The big air conditioner boxes that you might see on top of apartment blocks or offices are examples of the visible part of HVAC systems. But heating and cooling systems you use in your home are also HVAC systems. They may take a different form, but many of the fundamental principles determining how they operate, as well as their efficiency, crosses over from the smallest of personal devices right through to the biggest commercial installations.
Heating, ventilation and air conditioning HVAC systems supply fresh air and condition the indoor air temperature and humidity of a building. Therefore, HVAC is a key component of climate change mitigation potential in the building sector. HVAC systems normally consist of components to supply, filter, heat, cool and distribute the conditioned air into targeted interior spaces. This means the high-efficiency of one component can operate at expense of the others. As an example, take two categories of HVAC systems: high- and low-pressure systems. These systems have smaller ducts and require less space to house the duct system, but require more fan energy to drive the air. The high-velocity airflow has its speed reduced at the terminal outlets to avoid a strong flow of air that creates discomfort for occupants, known as draught. Low-pressure systems conduct supply airflow at low velocities and require larger duct spaces. In this case, HVAC system efficiency depends on the selection and integration of the key components that suit a specific building and its context. These key components, or sub-systems, are heating, cooling and ventilation.
Types of HVAC Systems
Additions and corrections. Bukupedia , The result is that engineers are better able to keep indoor environments safe and productive while protecting and preserving the outdoors for generations to come.
HVAC Systems: What You Need to Know
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.
This heat exchanger depends on two coils, placed diagonally and then connected in the middle. The humidity of the air measured by the number of grains of water vapor present in one cubic meter of air. The less volatile of the two working fluids in an absorption cooling device. In physics, the taking up of light, heat, or other energy by molecules.
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.