Direct drive power Electrical drive power Combining a CHP or cogeneration plant with an absorption refrigeration system allows utilisation of seasonal excess heat for cooling.
A simple stylized diagram of the refrigeration cycle: The system refrigerant starts its cycle in a gaseous state. The compressor pumps the refrigerant gas up to a high pressure and temperature.
From there it enters a heat exchanger sometimes called a condensing coil or condenser where it loses energy heat to the outside, cools, and condenses into its liquid phase. An expansion valve also called metering device regulates the refrigerant liquid to flow at the proper rate.
The liquid refrigerant is returned to another heat exchanger where it is allowed to evaporate, hence the heat exchanger is often called an evaporating coil or evaporator.
As the liquid refrigerant evaporates it absorbs energy heat from the inside air, returns to the compressor, and repeats the cycle.
In the process, heat is absorbed from indoors and transferred outdoors, resulting in cooling of the building. In variable climates, the system may include a reversing valve that switches from heating in winter to cooling in summer.
By reversing the flow of refrigerant, the heat pump refrigeration cycle is changed from cooling to heating or vice versa. This allows a facility to be heated and cooled by a single piece of equipment by the same means, and with the same hardware.
Free cooling Free cooling systems can have very high efficiencies, and are sometimes combined with seasonal thermal energy storage so that the cold of winter can be used for summer air conditioning. Common storage mediums are deep aquifers or a natural underground rock mass accessed via a cluster of small-diameter, heat-exchanger-equipped boreholes.
Some systems with small storages are hybrids, using free cooling early in the cooling season, and later employing a heat pump to chill the circulation coming from the storage.
The heat pump is added-in because the storage acts as a heat sink when the system is in cooling as opposed to charging mode, causing the temperature to gradually increase during the cooling season.
Some systems include an "economizer mode", which is sometimes called a "free-cooling mode".
When economizing, the control system will open fully or partially the outside air damper and close fully or partially the return air damper. This will cause fresh, outside air to be supplied to the system.
When the outside air is cooler than the demanded cool air, this will allow the demand to be met without using the mechanical supply of cooling typically chilled water or a direct expansion "DX" unitthus saving energy.
The control system can compare the temperature of the outside air vs. In both cases, the outside air must be less energetic than the return air for the system to enter the economizer mode. Minisplit ductless systems are used in these situations.
Outside of North America, packaged systems are only used in limited applications involving large indoor space such as stadiums, theatres or exhibition halls.
An alternative to packaged systems is the use of separate indoor and outdoor coils in split systems. Split systems are preferred and widely used worldwide except in the North America.
In the North America, split systems are most often seen in residential applications, but they are gaining popularity in small commercial buildings.
With the split system, the evaporator coil is connected to a remote condenser unit using refrigerant piping between an indoor and outdoor unit instead of ducting air directly from the outdoor unit. Indoor units with directional vents mount onto walls, suspended from ceilings, or fit into the ceiling.
Other indoor units mount inside the ceiling cavity, so that short lengths of duct handle air from the indoor unit to vents or diffusers around the rooms. Split systems are more efficient and the footprint is typically smaller than the package systems.
On the other hand, package systems tend to have slightly lower indoor noise level compared to split system since the fan motor is located outside. Dehumidification[ edit ] Dehumidification air drying in an air conditioning system is provided by the evaporator.
Since the evaporator operates at a temperature below the dew pointmoisture in the air condenses on the evaporator coil tubes. This moisture is collected at the bottom of the evaporator in a pan and removed by piping to a central drain or onto the ground outside. A dehumidifier is an air-conditioner-like device that controls the humidity of a room or building.
It is often employed in basements which have a higher relative humidity because of their lower temperature and propensity for damp floors and walls.
In food retailing establishments, large open chiller cabinets are highly effective at dehumidifying the internal air. Conversely, a humidifier increases the humidity of a building.
Maintenance[ edit ] All modern air conditioning systems, even small window package units, are equipped with internal air filters. These are generally of a lightweight gauzy material, and must be replaced or washed as conditions warrant.
For example, a building in a high dust environment, or a home with furry pets, will need to have the filters changed more often than buildings without these dirt loads.
Failure to replace these filters as needed will contribute to a lower heat exchange rate, resulting in wasted energy, shortened equipment life, and higher energy bills; low air flow can result in iced-over evaporator coils, which can completely stop air flow.
Additionally, very dirty or plugged filters can cause overheating during a heating cycle, and can result in damage to the system or even fire.
Because an air conditioner moves heat between the indoor coil and the outdoor coil, both must be kept clean.Heating and Cooling School Program Information.
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