ground-coupled heat exchanger

A geothermal heat exchanger ( EWT), or ground heat exchanger, geothermal heat exchanger or air fountain is a system for heating or cooling of air that is mostly used for ventilation systems of buildings.

Construction

There are different kinds of building a geothermal heat exchanger, systems that use geothermal heat directly collect and brine earth heat exchanger, at the sole filled pipes geothermal before.

Pipes or hoses, for example, plastic or concrete to be laid in the ground. The beginning of the pipe system is above ground, for example, at the end of the ventilation system. By means of a fan air is sucked and discharged by the system. The diameter can be from a few centimeters to several meters, the total length of up to a hundred meters.

Another structure is that fewer total length and promotes the air with direct " contact with the ground ." For this, a trench or pit is filled with gravel or other coarse material. Material in a tube and ends in a fan. Here too, air is sucked and transported through the interstices of the coarse material. This system was already used in ancient times.

A simple variant of an air preheating represents a so-called " Luftsiphon ", which ends at the bottom of an unused house well or ends in a domestic wells ( a Luftsiphon is a ventilating pipe cut from a basement window or grated extra- vent usually leads to the basement floor and about 10 cm ends above the ground. Although it may incorporate fresh air to a heating system, warm rising air but not drain to the outside). Cold air supply from the outside thus drops to the bottom of the well house, warms up on the walls of the well and rises. For a possible moisture absorption heat would be required. The system is used only for unused private wells, private wells in use there is a risk that the water pipe freezes, is also to provide a suitable fountain cover.

In winter gardens a so-called " Hypo exchanger " system is sometimes used with the overheating problems or drafts can be avoided. In the warm air in the winter garden water evaporates ( irrigation water fountain or water), the Ascended moist air is exhausted at the highest point of the conservatory and passed through hypocaust pipes on cold ground. Where the water vapor condenses, and the liberated heat of condensation is discharged to the ground. The moist poor but not necessarily more cold air is then fed back into the conservatory to cool the winter garden in the circuit.

Operation

The temperature of transported air is like at it flows through the system of the Earth's temperature. In good -sized plants, the air temperature can change by up to 10 degrees. The principle agrees in principle with the geothermal collector who works with liquid media, agree.

Method

The temperature of the upper soil follows the course of the year the ambient temperature. The closer to the surface of the closer to the daily average, the lower the more subdued and out of phase with the seasons. From around six meters depth, the temperature is constant.

This temperature difference makes you look more advantage:

• Is the outside air temperature as the ground, so the air before it is led into the building heated by the soil.
• Conversely, the incoming outside air is cooled by the earth in very warm weather.

In both directions of work energy is exchanged; soil is removed and the soil heat is supplied to heat. See also heat transfer

Trivia

The sucked air can be in buildings by means of a ventilation system, preferably with heat, distributed or fed. At air temperatures below 0 ° C can form inside the heat recovery device condensate and freeze into ice. To avoid this, one can use a geothermal heat exchanger. Secondly, the Heat recovery rate of the ventilation system increases.

Also, the geothermal heat exchanger can be mounted in front of an air heat pump.

In the system is created with warm air ( on the cold surfaces of the system) condensate, it should be derived.

Ancient versions for water production and reproduction

Even in ancient times were well air (French for " Puits aerien " English "air well" ( condenser ) ) is known. They were used for space cooling and water extraction from the air. The previously oldest known system of this type is the air fountain, destroyed by the Huns, originally Greek colony Teodosia in the Crimea, dating from the 4th century BC

The principle is based on the high temperature difference between the outside and inside and between day and night temperature, which can condense the humidity. The Belgian engineer Achille Knapen Built in 1931 according to this principle on a 600 meters high hill above Trans-en -Provence an air wells. The existing only as a ruin tower in Trans-en -Provence is about 45 meters high and has a wall thickness up to 10 meters. However, the wells produced only five liters of water per night.

Whether there may be older wells, which correspond to the principle of construction of the underground air well described in the Oeconomische Encyclopedia of Johann Georg Krünitz, is currently being discussed and explored by archaeologists and engineers on the basis of the well of Santa Cristina in Paulilatino in Sardinia. Of particular interest here is whether the amount produced was sufficient water to define the design principle as edification reason.

Hazards

Through contact with the ground rock the radon indoor air can rise. Contamination of transported air with radon ( due to a leaking pipe system, direct contact of the porous material with soil or rock at radonbelastendem gravel bed ) should be avoided for health reasons.