Produce building equipment and devices for heating
Commercial buildings include a variety of building types —offices, hospitals, schools, police stations, places of worship, warehouses, hotels, and shopping malls. Electricity and natural gas are the most common energy sources used in commercial buildings. Most individual commercial buildings have their own heating and cooling systems. However, there are district energy systems that supply heating and cooling to groups of commercial buildings. When many buildings are close together, such as on a college campus or in a city, having a central heating and cooling plant that distributes steam, hot water, or chilled water to multiple buildings is sometimes more efficient.VIDEO ON THE TOPIC: Making a High Temperature Electric Oven for Heat Treating Steel!!
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Gas heating - health and safety issues
Consequently, almost any business or government agency has the potential to realize significant savings by improving its control of HVAC operations and improving the efficiency of the system it uses. Extended comfort includes employing concepts such as providing warmer, but drier air using desiccant dehumidification in summer, or cooler air with warmer windows and warmer walls in winter. In addition, high-performance HVAC can provide increased user thermal comfort , and contribute to improved indoor environmental quality IEQ.
Given the range and complexity of the subject, this information should be viewed as only a starting point to access information from the many trade associations, agencies, and manufacturers linked throughout the text. Controls determine how HVAC systems operate to meet the design goals of comfort, safety, and cost-effective operation. Heating can be accomplished by heating the air within a space e.
Ventilating maintains an adequate mixture of gases in the air we breath e. Ventilation can be accomplished passively through natural ventilation , or actively through mechanical distribution systems powered by fans. Air-conditioning refers to the sensible and latent cooling of air. Sensible cooling involves the control of air temperature while latent cooling involves the control of air humidity.
Room air is cooled by transferring heat between spaces, such as with a water loop heat pump system, or by rejecting it to the outside air via air-cooled or water-cooled equipment. Heat can also be rejected to the ground using geothermal exchange. Cool air is not comfortable if it is too humid. Air is dehumidified by condensing its moisture on a cold surface, such as part of mechanical cooling , or by removing the moisture through absorption desiccant dehumidification.
In dry climates, humidification may be required for comfort instead of dehumidification. Evaporative humidification also cools the air. Further, in such climates it is possible to use radiant cooling systems, similar to the radiant heating systems mentioned above.
Controls ensure occupant comfort, provide safe operation of the equipment, and in a modern HVAC control system enable judicious use of energy resources. It is the function of the controls to ensure that the HVAC systems perform properly, reliably, and efficiently during those conditions that occur Each HVAC discipline has specific design requirements and each has opportunities for energy savings.
It must be understood, however, that energy savings in one area may augment or diminish savings in another. Therefore, understanding how one system or subsystem affects another is essential to making the most of the available opportunities for energy savings. This design approach is known as whole building design. Employing high-performance HVAC equipment in conjunction with whole building design can result in significant energy savings.
These figures apply to buildings that offer conventional comfort e. If the comfort zone is extended through natural ventilation and air movement in summer, and through lower air temperatures in winter made possible by highly-insulated and, therefore, warmer wall and window surfaces , even higher savings can be achieved.
However, note that highly energy-efficient design utilizing high-performance HVAC equipment often requires more effort and more collaboration from the design team than a conventional, sequential approach.
Consider all aspects of the building simultaneously. The building should incorporate as many features as possible that reduce heating and cooling loads, for example:. Decide on design goals as early as possible. It is important that the design team knows where it is headed long before the construction documents phase. Plan for future expansion instead of greatly oversizing the equipment.
This concept extends to accommodating for planned expansion. Don't provide excess capacity today for a future load that may never exist, instead:. The result is savings in first cost and operating cost, and savings in construction cost and down time when making expansion alterations. Commission the HVAC systems. Many advocates of high-performance buildings are urging that more general, Total Building Commissioning TBC be implemented.
More information on commissioning can be found at:. Boilers are used to generate steam or hot water and can be fired by natural gas, fuel oil, or coal. Furnaces can be used for residential and small commercial heating systems. Furnaces use natural gas, fuel oil, and electricity for the heat source. Natural gas furnaces are available in condensing and non-condensing models.
The cooling can be packaged within the system, or a cooling coil can be added. When direct expansion systems with coils are used, the condenser can be part of the package or remote.
Heat pumps are devices that add heat to or extract heat from a conditioned space. Both refrigerators and air conditioners are types of heat pumps that extract heat from a cooler, conditioned space and reject it to a warmer space i.
Heating can be obtained if this cycle is reversed: heat is moved from the outdoors to the conditioned space indoors. Heat pumps are available in two major types: conventional packaged air-source and water-source conventional or geothermal. The fourth improves the efficiency during operation. Modulating flame —The heat input to the boiler can be adjusted continually modulated up or down to match the heating load required.
Modulating flame boilers have a minimum turn-down ratio, below which the boiler cycles off. Compared to steady-state units, the capacity of the boiler can come closer to the required heating load. Modular boilers —Another energy-efficient measure is to assemble groups of smaller boilers into modular plants. As the heating load increases, a new boiler enters on-line, augmenting the capacity of the heating system in a gradual manner.
As the heating load decreases, the boilers are taken off-line one by one. Oxygen trim systems continuously adjust the amount of combustion air to achieve high combustion efficiency. They are usually cost-effective for large boilers that have modulating flame controls. Ventilation systems deliver conditioned air to occupied spaces. In commercial and institutional buildings, there are a number of different types of systems for delivering this air:.
Constant air volume CAV systems deliver a constant rate of air while varying the temperature of the supply air. If more than one zone is served by a CAV system, the supply air is cooled at a central location to meet the need of the zone with highest demand. The other zones get overcooled or, if comfort is to be maintained, the air is reheated at the terminal units. CAV systems with reheat are inefficient because they expend energy to cool air that will be heated again.
CAV systems with reheat, however, provide superior comfort in any zone. Constant airflow reduces pockets of "dead" air, and reheat provides close control of the space temperature.
Variable air volume VAV systems vary the amount of air supplied to a zone while holding the supply air temperature constant. This strategy saves fan energy and uses less reheat than in a CAV system. VAV systems, however, can have problems assuring uniform space temperature at low airflow rates. At times, the minimum airflow required for ventilation or for proper temperature control may be higher than is required to meet the space load.
When this occurs reheat may be required. Low-flow air diffusers in VAV systems help maintain uniform air distribution in a space at low airflows. These devices can be passive or active. Passive low flow diffusers are designed to mix the supply air with the room air efficiently at low flow. Active diffusers actually move the outlet vanes of the diffuser to maintain good mixing at low flow. Active diffusers can also be used as VAV terminal units. Fan-powered VAV terminal units provide another method to improve air distribution at low load conditions.
These units combine the benefits of a VAV system, by reducing central fan energy and reheat energy, with the benefits of a CAV system, by maintaining good airflow. There are two major types, series and parallel: Series fan-powered units maintain constant airflow to the zone at all times; parallel fan-powered units allow the airflow to the zone to vary somewhat, but do not allow the airflow in the zone to drop below a desired level. Both, however, allow the central fan to throttle down to the minimum airflow required for ventilation.
Raised floor air distribution delivers air low in the space, at low velocity and relatively high temperature compared to traditional plenum mounted distribution systems. Delivering air through a series of adjustable floor-mounted registers permits room air to be stratified with lower temperatures in the bottom portion of the room where people are located and high temperatures towards the ceiling. This system type is attracting increasing interest because it has the potential to save energy and to provide a high degree of individual comfort control.
These systems have historically used constant-volume air delivery. Manufacturers arenow beginning to offer VAV systems that are more easily designed, installed, and operated with raised floor plenum systems. In recent years, ventilation control systems have become more complex and, if installed and maintained properly, more dependable. Among the advancements are:. Direct digital control DDC systems using digital-logic controllers and electrically-operated actuators are replacing traditional pneumatic controls.
Pneumatic systems use analog-logic controllers and air-pressure actuators. DDC systems are repeatable and reliable,provide accurate system responses, and can be monitored from a central computer station.
DDC systems also require less maintenance than pneumatic systems. However, pneumatic controllers can be less expensive than electric actuators. Hybrid systems use a combination of digital logic controllers and pneumatic actuators. CAV systems should have controls to reset the supply air temperature at the cooling coil to provide the warmest air possible to the space with the highest cooling load.
This reduces reheat throughout the system. However, the temperature should be no higher than is necessary to properly dehumidify the air. Another option to reduce reheat is to use a bypass system. Bypass systems work like variable volume systems at the zones, but have constant airflow across the central fan. VAV systems can now be designed to serve areas with as little as six tons of cooling load. Inlet vanes or, better yet, variable speed fans should be used to control air volume.
Heat pumps continue to represent a small share of total residential heating equipment, as more than three-quarters of sales globally were for fossil fuel or conventional electric technologies in Sweden, Estonia, Finland and Norway have the highest penetration rates, with more than 25 heat pumps sold per 1 households each year. Air-to-air heat pumping technologies dominate global sales for buildings, but purchases of other heat pump types such as air-to-water and geothermal heat pumps have also expanded in recent years.
Much of this is owing to energy intensity improvements in major heating markets such as Canada, China, the European Union, Russia and the United States. Nevertheless, fossil fuels still supply most space heating and hot water production needs in buildings and direct emissions from heating in buildings have remained stable since as a result. But progress is not fast enough to fulfil SDS ambitions, which call for the use of high-efficiency fossil fuel-based equipment e. To be in line with the Sustainable Development Scenario SDS , the share of clean energy technologies such as heat pumps and solar thermal heating needs to triple to more than one-quarter of new heating equipment sales by Nearly 20 million households purchased heat pumps in , up from 14 million in , but most of this growth is from higher sales of reversible units that can also provide air conditioning, which reflects rising cooling demand.
Additions and corrections. Bukupedia , 15 thg 7, - trang. 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. Main sections cover comfort, industrial, energy-related, general applications, and building operations and management. ASHRAE Technical Committees in each subject area have reviewed all chapters and revised them as needed for current technology and design practice. Reader comments are enthusiastically invited. Mark S. Owen Editor.
But, you should have at least a basic understanding of how the system works and what options you have when the heater needs replacing. There four basic types of residential water heaters: tank-type, hybrid, tank-less, and point-of-use. Tank-type heaters are by far the most popular kind but tank-less water heaters are growing exponentially each year. A vast majority of homes have conventional tank-type water heaters , which are powered by either gas or electricity. Generally speaking, gas water heaters are more expensive to buy than electric models, but cost less to operate because gas is cheaper than electricity.
Most labs use at least one type of heating device, such as ovens, hot plates, heating mantles and tapes, oil baths, salt baths, sand baths, air baths, hot-tube furnaces, hot-air guns and microwave ovens. Steam-heated devices are generally preferred whenever temperatures of o C or less are required because they do not present shock or spark risks and can be left unattended with assurance that their temperature will never exceed o C. Ensure the supply of water for steam generation is sufficient prior to leaving the reaction for any extended period of time.
Understanding Heat Exchangers
With this the Seventh edition, a year publishing tradition continues for Time-Saver Standards. Conceived in the mid-. The first hardbound edition of Time-Saver. Palm, appears as a reprint in the.
Electric heating is a process in which electrical energy is converted to heat energy. Common applications include space heating , cooking , water heating and industrial processes. An electric heater is an electrical device that converts an electric current into heat. Most modern electric heating devices use nichrome wire as the active element; the heating element, depicted on the right, uses nichrome wire supported by ceramic insulators. Alternatively, a heat pump uses an electric motor to drive a refrigeration cycle , that draws heat energy from a source such as the ground or outside air and directs that heat into the space to be warmed.
U.S. Energy Information Administration - EIA - Independent Statistics and Analysis
Note: Full citations to supporting materials can be found in the pdf version of this brief. This brief provides an overview of emissions trends and projections, and of decarbonization challenges and opportunities, in the U. Residential and commercial buildings use large quantities of energy for heating, cooling, lighting, and other needs. In —, the median ages of a U. Slow turnover means that by mid-century much of the existing U. Population and economic growth will also drive substantial increases in the total building stock. Substantially decarbonizing the building sector requires steps in the near term to reduce the energy demand and carbon intensity of both existing buildings and new construction.
Victorian government portal for older people, with information about government and community services and programs. Type a minimum of three characters then press UP or DOWN on the keyboard to navigate the autocompleted search results. Gas heaters need to be professionally installed and serviced by a trained and qualified gasfitter.
What Is CHP?
United States. Committee on Banking, Currency and Housing. Subcommittee on Housing and Community Development.
Decarbonization Opportunities and Challenges
Romina Ronquillo. Heat exchangers are devices designed to transfer heat between two or more fluids—i. Depending on the type of heat exchanger employed, the heat transferring process can be gas-to-gas , liquid-to-gas , or liquid-to-liquid and occur through a solid separator, which prevents mixing of the fluids, or direct fluid contact.
Last updated: May 23, F ire was one of humankind's earliest and greatest discoveries—something like one or two million years ago. In our modern age of jet engines , space rockets , steel skyscrapers, and synthetic plastics , smoke and flames might seem positively prehistoric. But all four of those inventions—and dozens of others besides—rely on fire in one crucial way or another.
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 and Cooling of Buildings: Principles and Practice of Energy Efficient Design, Third Edition is structured to provide a rigorous and comprehensive technical foundation and coverage to all the various elements inherent in the design of energy efficient and green buildings. Along with numerous new and revised examples, design case studies, and homework problems, the third edition includes the HCB software along with its extensive website material, which contains a wealth of data to support design analysis and planning. It serves as an up-to-date technical resource for future designers, practitioners, and researchers wishing to acquire a firm scientific foundation for improving the design and performance of buildings and the comfort of their occupants. He is the author of two textbooks and has close to refereed journal and conference papers, and several book chapters and technical research reports.