Thermosiphon convection brake

from Wikipedia, the free encyclopedia
Schematic comparison of hot water storage tanks without / with thermosiphon

As a thermosyphon , a heat sink or heat siphon (engl. Heat trap (siphon) ) refers to the installation of a downfalling pipe directly to a hot water tank to the heat loss by natural convection within the limit hot water connecting pipe. Alternatively, a downward-facing plate can be provided in the hot water connection in or on the storage tank, which prevents the heated water from circulating in the connection pipe.

functionality

In the case of heat accumulators, such as those used in central heating systems for the provision of hot water or in thermal solar systems for heat storage, if the pipe routing is unfavorable (e.g. directly from the storage tank vertically upwards as with the outdated gravity heating), convection occurs within the connected pipe or in the The solar thermal even in the connected collector. These convection losses can be reduced by laying pipes in the form of an upside-down pipe siphon , i.e. a downward-facing pipe that prevents the lighter, heated water from rising.

Even in a connection line with a steadily downward gradient from the storage tank, no significant convection can occur. However, if the pipe is led back up after the downward stretch, it is recommended - depending on the source - either to lead the downwardly directed pipe up to 20 cm below the connection, or 3 to 12 times as a scale for this distance Pipe diameter to choose.

With a connection without a thermosiphon, the warm water rises due to its lower density and cools down on the pipe wall of the connected pipe. The heavier, cool water flows back into the storage tank along the pipe wall. The colder water flowing back into the tank can also break up a desired stratification within the tank. With a thermosiphon construction, circulation can only occur up to the highest point of the pipe run, as the warm water does not follow the downward pipe. Convection losses are therefore limited to the route up to the siphon. Ideally, the connections directly on the tank should be designed so that the water is led down a short distance.

Alternatively, a convection brake in the form of a non-return valve can be installed at the connection to the storage tank . In contrast to non-return valves, which are intended to prevent the heated water from being pushed back into the drinking water line at the cold water inflow to the storage tank, convection brakes do not have to close completely tightly, or may not be allowed to do so at all.
Check valves or non-return valves as convection barriers or gravity brakes are also provided in heating circuits and circulation lines in order to prevent free convection when the pump is switched off.

literature

swell

  1. ↑ Have we forgotten to make heat traps? , a technical article in English by Esbe AB, May 2012
  2. ↑ a b Information on the thermosiphon on the Internet pages of master craftsmen and vocational school subject teachers i. R. Bruno Bosy; accessed in August 2016.

Web links