Antifreeze
The term frost protection summarizes all measures and methods that are intended to prevent liquids from freezing. Under certain circumstances, this is technically necessary because the volume of ice becomes larger than that of liquid water and the space requirement that is a few percent larger can lead to great forces ( frost blasting ).
There are three strategies for frost protection:
- the freezing point is lowered by adding to the water, or
- by supplying heat, temperatures of the component to be protected below zero degrees Celsius are prevented, or
- the water flow in pipes must not come to a standstill.
Furthermore, frost protection is an abbreviation for the broken aggregate of the frost protection layer .
Frost protection is available as a Union brand name through the Munich Patent Office (EUIPO, European Intellectual Property Office) with registration number 015696933 Europe-wide for class 33 (alcoholic preparations for making beverages; alcoholic beverages, except beer) and since March 2, 2017 with the registration number 015140007 Europe-wide for class 32 (beer and brewery products; non-alcoholic beverages; preparations for making beverages).
Frost protection of plants
Plants are damaged or die when their cell water freezes. While some plants protect themselves through the appropriate composition of the cell fluid, others partially or completely die from frost . For the root zone of crops is frost penetration into the soil crucial.
Frost is particularly important economically during the fruit bloom. The trunk of woody plants that can withstand freezing temperatures can also be damaged by a sharp drop in temperature if the water content under the bark has not yet been sufficiently reduced.
Examples of frost protection for plants:
- Cover with straw, manure, towels and / or boards to isolate the plants from the cold air. This measure is mainly used in horticulture .
- White (lime paint) of the trunks: the effect does not arise (as is often assumed) through reduced heat radiation at night, but through less warming during the day from the sun, which means that the plant is more likely to adapt to frost (it has to reduce the water content).
- Glass roofing or glass houses: Glass is opaque to the wavelength of heat radiation (mid- infrared around 10 micrometers wavelength ) and is therefore able to hold back this radiation by heating itself up and shifting the radiation balance to higher temperatures (this so-called greenhouse effect occurs also in the atmosphere when it is cloudy, therefore higher night temperatures prevail when the sky is cloudy than on cloudless nights).
- Area heating through small stoves in close arrangement in which oil, coal or candle wax ("frost candles") is burned. This measure is mainly used in steep orchards without access to water and in viticulture. Other heating systems , e.g. B. warm air heaters are also used.
- Frost protection sprinkling : sprinkling crops, especially fruit blossoms, with very fine water droplets. As a result of this irrigation, they can withstand freezing temperatures for a limited time, because a thin layer of ice forms on the frost-sensitive flowers. During this process, the water's solidification heat is released and the temperature inside the ice shell cannot fall significantly below freezing point over a longer period of time. In order to avoid subsequent damage, the frost protection irrigation must be continued until the ice has melted again or the temperature is significantly above freezing point.
Frost protection of systems and devices
Devices and systems containing water - especially water-cooled - must be protected from frost to prevent the freezing water from destroying containers and pipes due to the water anomaly (volume increase when solidifying).
Frost protection can either be achieved by adding antifreeze agents to the water or - if this is not possible - by using a frost protection heater, appropriate insulation (in the event of brief frost exposure) or removing the water from the system.
Examples:
- Radiator thermostatic valves have a “star” position at which they keep the temperature just above freezing point to prevent them from freezing.
- So-called frost protection thermostats (electrical heating + temperature switch) are used in living rooms.
- In systems and devices, heaters, frost protection thermostats, or self-regulating NTC heating elements, etc. You may also ensure that certain components remain functional (e.g. oil-filled circuit breakers, electrolytic capacitors , heavy oil tanks and lines on ships).
- Some systems must be drained of water (e.g. laser devices) before they are transported at risk of frost.
- Water-cooled internal combustion engines contain water with an antifreeze additive as the coolant.
Frost protection of water pipes
Water pipes laid in the ground are largely protected from frost by their laying depth (in Germany> 0.5 m). Lines laid outdoors must be protected from freezing, as the formation of insulated ice plugs over the entire cross-section of the line (e.g. at points with thermal bridges) can lead to damage. Due to their elasticity, water pipes made of plastic are not at risk to the same extent as metal pipes. Nevertheless, in the case of pipes carrying drinking water there is a hygiene risk due to the stagnation of the water.
Metal water pipes at risk of frost can be protected from freezing with thermal insulation if water is regularly exchanged (water removed). The water provided by the water supplier usually has an annual minimum temperature of 6 ° C. In the case of constant water exchange through extraction, there is therefore an input of heat from the water flowing in. With sufficient insulation, the water temperature can be kept above freezing point. If this cannot be guaranteed, heating conductors can be laid along the line. The VDI 2069 guideline contains practical information on the operation and insulation of pipes and the design and control of trace heating.
In the case of non-drinking water pipes, effective protection against freezing is possible through timely disconnection and emptying. For this purpose, the lines must be planned and designed accordingly (slope, drainage at the lowest point). Non-drinking water pipes must, however, be separated from pipes carrying drinking water by a safety device in accordance with DIN EN 1717. Shutting off frost-prone parts of drinking water installations, e.g. B. garden and garage taps, or from lines to and in temporarily unused and unheated buildings, such as holiday homes, is to be rejected for reasons of hygiene, as the water remaining in the lines stagnates over the duration of the shut-off and leads to serious contamination of the entire drinking water -Installation can result. Insulated parts of the drinking water installation that are to be protected by shutting off must therefore be blown dry.
Window antifreeze for car windshield washer systems
Windscreen cleaner additives for car windscreen washers based on ethanediol prevent the spray nozzles from freezing. In Germany, the use of windscreen frost protection in wintry weather conditions has been a legal requirement since October 2006. In addition to frost protection, cleaning performance is an essential quality feature for the windscreen cleaner additive. Creating clear visibility as quickly as possible is the characteristic that characterizes good products and contributes to safety in road traffic.
Current vehicles with fan nozzles place particularly high demands on windscreen antifreeze, as a low viscosity is required despite the low freezing point . Cars with xenon headlights must be equipped with a headlight cleaning system. The high-pressure nozzles used here are also fed from the windscreen washer system and have similarly high demands on the quality of the windscreen antifreeze used.
Inexpensive products are available on the market which do not guarantee material compatibility. These can be paint, rubber and plastics such as B. attack headlight housing made of polycarbonate and lead to stress cracks.
See also
Web links
Individual evidence
- ↑ Vintners use frost candles . Süddeutsche Zeitung , accessed on May 8, 2016.
- ↑ Michael Breu: Farmers arming - With the hay blower against the frost. In: srf.ch . May 6, 2019, accessed May 7, 2019 .
- ↑ VDI 2069. Retrieved on March 4, 2014 .
- ↑ DIN EN 1717. (No longer available online.) Archived from the original on February 23, 2014 ; accessed on March 4, 2014 .
- ↑ VDI / DVGW 6023. Retrieved on March 4, 2014 .