Energy recovery ventilation ( ERV ) is the energy recovery process of energy exchange contained in a building or space air that normally runs out and uses it to treat outdoor air ventilation (prerequisites) entered in residential and commercial HVAC systems. During the warmer seasons, the system cools and removes moisture during moisture and preheating in colder seasons. The advantage of using energy recovery is the ability to meet ASHRAE & amp; energy standards, while improving indoor air quality and reducing total HVAC equipment capacity.
This technology not only shows an effective way to reduce energy costs and heating and cooling loads, but has made it possible to reduce equipment. In addition, the system will allow the indoor environment to keep relative humidity from 40% to 50%. This range can be maintained basically all conditions. The only energy penalty is the power that the blower needs to overcome the pressure drop in the system.
Video Energy recovery ventilation
Importance
Almost half of the global energy is used in buildings, and half of the heating/cooling costs are caused by ventilation when done with the "open window" method according to the rules [define method and include citation]. Second, energy and network generation are built to meet peak power demand. To use proper ventilation; recovery is a cost-effective, sustainable and quick way to reduce global energy consumption and provide better indoor air quality (IAQ) and protect buildings, and the environment.
Maps Energy recovery ventilation
Transfer method
The energy recovery ventilator (also abbreviated ERV) is a type of air-to-air heat exchanger that not only transfers reasonable heat but also latent heat. As temperature and humidity are removed, ERV can be considered a total enthalpy device. On the other hand, the heat recovery ventilator (HRV) can only transfer reasonable heat. HRVs can be considered as a sensible device simply because they only exchange reasonable heat. In other words, while all ERVs are HRV, not all HRV is ERV, but many people use the term HRV, AAHX (air-to-air heat exchangers), and ERV alternately.
Throughout the winter, the system works to cool and eliminate incoming air humidity. This is done by a system that takes the rejected heat and sends it into the exhaust air stream. Furthermore, this air cools the condenser coil at a lower temperature than when the rejected heat does not enter the exhaust air stream. During the heating season, the system works in reverse. Instead of removing heat into the exhaust stream, the system draws heat from the exhaust stream for pre-heat incoming air. At this stage, air passes through the main unit and then into space. With this type of system, it is normal, during the cooling seasons, to keep the exhaust air cooler than the air vents and, during the heating season, warmer than the air vents. For this reason the system works very efficiently and effectively. The performance coefficient (COP) will increase as conditions become more extreme (ie hotter and humid for cooling and cold for heating).
Efficiency
The efficiency of an ERV system is the ratio of energy transferred between two airflows compared to the total energy transported through a heat exchanger.
With various products in the market, efficiency will also vary. Some of these systems have been known to have a heat exchange efficiency as high as 70-80% while others have as low as 50%. Although this lower number is better than the basic HVAC system, it is not equivalent to the rest of its class. Studies are underway to improve heat transfer efficiency by up to 90%.
The use of low-cost low-cost heat-exchange technology will enable significant efficiency improvements. The use of high conductivity porous materials is believed to produce an exchange effectiveness of more than 90%. By exceeding a 90% effective rate, an increase of up to five factors in energy loss can be seen.
The Home Ventilation Institute (HVI) has developed standardized tests for any and all units manufactured in the United States. Regardless, not all have been tested. It is important to investigate the claims of efficiency, comparing the data generated by HVI as well as those manufactured by the manufacturer. (Note: all units sold in Canada are placed through the R-2000 program, a standard test identical to the HVI test).
Energy recovery device type
** Total energy exchange is available only in hygroscopic units and condensate return units
Rotary air-to-air enthalpy wheel
The rotating wheel's heat exchanger consists of a rotating cylinder filled with air permeable material resulting in a large surface area. The surface area is the medium for reasonable energy transfer. When the wheel spins between ventilation and the exhaust stream, it takes the heat energy and releases it into the cooler air stream. The driving force behind the exchange is the temperature difference between opposing air currents, also called thermal gradients. Commonly used media consists of polymers, aluminum, and synthetic fibers.
The enthalpy exchange is done through the use of desiccation. Desiccants transfer moisture through a predominant adsorption process driven by a partial pressure difference of vapor in the opposite airflow. Special driers consist of silica gel, and molecular sieves.
Enthalpy wheel is the most effective device for transferring latent and sensible energy but there are many types of constructions that determine the durability of wheels. The most common materials used in rotor construction are Polymer, Aluminum and Fiberglass.
When using a rotary energy recovery device, two airflows must be adjacent to each other to allow local energy transfer. Also, there should be special consideration paid in cold climates to avoid wheel frosting. The system can avoid frosting by modulating wheel speed, preheating the air, or stopping/jogging the system.
The heat exchanger
The plate heat exchanger still has no moving parts, and consists of alternating layers of plates that are separated and sealed. Typical flow is cross flow and since the majority of plates are solid and not permeable, a reasonable transfer is the result.
Incoming fresh air temperatures are carried out by a heat recovery core or energy. In this case, the core is made of aluminum or plastic plate. The humidity level is adjusted by moisture transfer. This is done with a good spinning wheel that contains a drying agent or permeable plate.
The anterior plate was introduced in 2006 by Paul, a specialized company for ventilation systems for passive homes. A cross-air air-to-air heat exchanger built with moisture permeability material. Polymer fixed-plate countercurrent energy recovery ventilators were introduced in 1998 by Building Performance Equipment (BPE), a residential, commercial, and industrial air-to-air energy recovery manufacturer. This heat exchanger can be introduced as a retrofit for increased energy and fresh air savings as well as alternatives to new construction. In new construction situations, energy recovery will effectively reduce the heating/cooling capacity required by the system. The percentage of total energy saved will depend on the efficiency of the device (up to 90% reasonable) and the latitude of the building.
Due to the need to use several parts, the fixed plate energy exchanger is often associated with higher pressure drops and larger footprints. Due to their inability to offer large amounts of latent energy transfer, the system also has a high probability for frosting in cold climates.
Technology patented by Finnish company, RecyclingEnergy Int. Corp. is based on regenerative plate heat exchangers that utilize air humidity with cyclic condensation and evaporation, for example latent heat, enabling not only high annual thermal efficiency but also microbial free plate due to self-cleaning/washing methods. Therefore this unit is called an enthalpy recovery ventilator rather than a heat or energy recovery ventilator. Company patented patentHeatPump is based on an enthalpy recovery ventilator that has COP 33 in summer and 15 in winter.
References
External links
- http://www.engineeringtoolbox.com/heat-recovery-efficiency-d_201.html
- Designing a Special Outdoor Air System, Stanley A. Mumma
- http://www.lowkwh.com - energy recovery methods and publications
- http://www.UltimateAir.com
- Energy and Heat Recovery Ventilator (ERV/HRV)
- Heat Recovery Ventilation TANGRA
- Heat Recovery Vent Heat Recovery
Source of the article : Wikipedia
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