Heat recovery ventilation

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Heat recovery vents ( HRV ), also known as mechanical ventilation heat recovery ( MVHR ), ventilation using equipment known as heat recovery ventilators, heat exchanger, air exchanger, or air-to-air heat exchanger using cross flow or backflow heat exchanger (exchange of alternating current) between inlet and outflow air.

Energy recovery Ventilator (ERV) is closely related; however, ERV also transfers the moisture level of the exhaust air into the intake air.

Video Heat recovery ventilation

Benefits

Since the building's efficiency is enhanced by the isolation and stripping of the weather, the buildings are deliberately made more airtight, and consequently are less well-ventilated. The HRV system provides ventilation without heat or moisture loss, which can cause pressure on the heating, ventilation/ventilation and AC (HVAC) systems of the building. HRV introduces fresh air into buildings and improves climate control, while promoting efficient energy use.

UK building regulations require one air change every two hours (0.5 ACH). With special ventilation extract-only which means the home boiler needs to warm the house full of cold air 12 times a day.

Maps Heat recovery ventilation

Technology

HRV and ERV can be stand-alone devices that operate independently, or they can be built or added to existing HVAC systems. For small buildings where almost every room has exterior walls, the HRV/ERV device can be small and provide single room ventilation. Larger buildings will require many small units or large central units. The only requirement for the building is the air supply, either directly from the exterior wall or channeled to one, and the energy supply for air circulation, such as wind or electric energy for fans and electronic control systems. When used with 'central' HVAC systems, the system will be a type of 'air force'.

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Air-to-air heat exchanger

There are a number of air-to-air heat exchangers that can be used in HRV devices:

• cross flow heat exchanger to 60% efficient (passive)
• Recuperator, or cross-plate heat exchange, heat exchanger in the opposite direction, as illustrated on the right
• Thermal Wheel, or rotary heat exchanger (requires motors to twist the wheels)
• Hot pipes
• thin hot cable (fine wire heat exchanger)

Also see:

• shell and tube heat exchanger
• Heat exchanger plate
• dish dorsal heat exchanger
• Earth heat exchanger
• The surface heat exchanger is dynamically digested
• Waste Heat Recovery Unit
• Heat exchanger
• Heat brew exchange heaters

Inlet air

The air coming into the heat exchanger should be above 0 Â ° C. Otherwise, the humidity in the exit air can condense, freeze and block the heat exchanger.

High air intake temperatures can also be reached by

• circulate some of the exhaust air (causing loss of air quality) when needed,
• by using a very small heat pump (1 kW) to warm the inlet air above freezing before entering the HRV device. (The 'cold' side of the heatpump is located in a warm air outlet.)
• using heat-supplied "batteries" from heat sources eg. hot water circuits from wood-fired boilers, etc.

src: homevent.com.au

Air-to-air heat exchanger

This can be done with a warm-up pipe ("heat exchanger connected to the ground"), typically about 30 m to 40 m long and 20 cm, usually buried about 1.5 m below ground level. In Germany and Austria this is a common configuration for geothermal-to-air exchangers.

In high humidity areas where internal condensation can cause mold/mildew growth in tubes leading to airborne contamination, several steps exist to prevent this.

• Ensure a sewer
• Regular cleaning
• Tubes with an embedded bactericide layer like silver ions (non-toxic to humans)
• Air filter F7/EU7 (& gt; 0.4 micrometer) to trap prints (sizes between 2 and 20 micrometers)
• UV air purification
• Use the earth for "water heaters", see below

The pipes can become wavy/placed to increase heat transfer and provide condensate or fine/solid drainage to prevent gas/liquid transfer.

Air quality

It really depends on the site.

Radon

One of the critical problems of using an earth-to-air heat exchanger is on the ground with a layer of rock beneath which emits radon. In this situation the tube must be airtight from the surrounding soil, or the air-to-water heat exchanger should be used.

Bacteria and fungi

Formal research shows that Earth-to-Air Heat Exchangers (EAHX) reduce air pollution of buildings. Rabindra (2004) states, "The Earth-Air tunnel is found not to support the growth of bacteria and fungi, but is found to reduce the amount of bacteria and fungi thus making the air safer for humans to inhale.Hence it is clear that the use of geothermal-to-air exchangers not only help save energy but also help reduce air pollution by reducing bacteria and fungi. "

Likewise, Flueckiger (1999) in a study of twelve Earth-to-Heat Exchangers that varied in design, plumbing materials, size and age, stated, "This study was conducted due to concerns of potential microbial growth in buried pipelines of 'soil systems but the results indicate that no harmful growth is occurring and that the concentration of airborne spores and bacteria can live in the air, with some exceptions, even decreasing after passing through the pipeline system, "and further stated," Based on this investigation of geothermal exchanges -to-air ground-coupled can be received during the regular control is performed and if appropriate cleaning facilities are available ".

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Earth-to-water heat exchanger

An alternative to geothermal-to-air exchanger is a geothermal-to-water exchanger. This is usually similar to a geothermal heat pump tube embedded horizontally on the ground (or it can be a vertical pipe/sonde) to the same EAHX depth. It uses about twice the length of the pipe ËÅ"35 mm which is about 80 meters compared to EAHX. A heat exchanger coil is placed before the air passage from HRV. Usually salt water (highly salted water) is used as a slightly more efficient and environmentally friendly heat exchange solution than a polypropylene heat transfer fluid.

In temperate climates in energy-efficient buildings, such as the passivhaus, this is more than enough for comfortable cooling during the summer without using an air conditioning system. In a more extreme hot climate, a very small air-to-air micro-heat pump inverted with an evaporator (providing heat) to the air intake passage after a HRV heat exchanger and condenser (taking heat) from the outlet air after a heat exchanger will suffice.

src: www.a1airconditioning.ca

Passing seasonal

At certain times of the year, it is more efficiently thermally to pass the Heat-ventilation-HRV heat exchanger or EAHX.

For example, during winter, the earth at the depth of the heat-to-air exchanger is usually warmer than the air temperature. The air became warmer by the earth before reaching the heat exchanger.

In summer, what happens is the opposite. The air becomes cold on earth for air exchangers. But after passing through EAHX, the air is warmed by a heat recovery ventilator using the warmth of the air out. In this case, HRV can have an internal bypass so that air enters through a heat exchanger that maximizes the cooling potential of the earth.

In the fall and spring there may be no thermal benefits from EAHX - it may heat up/cool the air too much and it would be better to use the external air directly. In this case, it helps to have the bypass in such a way that the EAHX is disconnected and the air is taken directly from the outside. Differential temperature sensor with motorized valve can control cutting function.

src: www.a1airconditioning.ca

See also

src: ecoperformancebuilders.com

References

src: www.jlmelectrical.co.uk

External links

Non-commercial links

• AIVC VIP6 Information Paper "Heat-to-Air Heat Recovery in Ventilation System"
• Industrial Heat Recovery
• Energy and Heat Recovery Ventilator (ERV/HRV)

Source of the article : Wikipedia