Gravitational circulation (definition)

Gravitational circulation - this is a process of natural movement coolant (liquid or gas) in a heating or cooling system, based on the difference in density of the hot and cold substance. In this case, the hot coolant, having a lower density, rises up, and the cold one, with a higher density, goes down, creating a natural flow in the system without the need for mechanical pumps.

Main characteristics:

1. Principle of operation:
   • Thermal gradient: In a gravity circulation system, the hot liquid (or gas) is heated and expands, making it less dense. This causes the hot coolant to rise, while the cold coolant, cooled and denser, falls. This creates a natural movement of the coolant through the system.
2. Advantages:
   • Simplicity: Does not require the use of circulation pumps or other complex equipment.
   • Reliability: Less risk of breakdowns as there are no moving parts to fail.
   • Energy efficiency: No need for electricity to operate the pumps reduces operating costs.
3. Restrictions:
   • Efficiency: Gravity circulation may be less effective in large systems or in systems with long pipelines where the temperature difference is not always sufficient to create significant pressure.
   • Adjustment: More complex regulation of temperature and heat distribution, since there is no possibility to precisely control the flow of the coolant.
4. Equipment:
   • Pipelines: The system must be designed to accommodate gravity circulation, which includes using pipes installed at the correct angle for optimal fluid movement.
   • Radiators and convectors: Should be installed so that hot liquid can effectively rise to them and cooled liquid can return to the system.
5. Installation and setup:
   • Pipe laying: Pipes must be installed with the correct slope to ensure natural flow of fluid. This usually requires slopes of 1-2% depending on the length and diameter of the pipes.
   • Adjustment: It is important to set up the system correctly to ensure efficient movement of the coolant and avoid circulation problems.
6. Application:
   • Small heating systems: Gravity circulation is often used in older or smaller heating systems where complex pumping systems are not needed.
   • Traditional systems: Can be used in traditional heating systems where the system was designed taking into account the natural movement of the coolant. Gravity circulation is an economical option for an autonomous system.

Example of use:

In a traditional gravity circulation heating system, hot water rises up to radiators located on the upper floors and then returns back down to the boiler after cooling. This ensures that heat is distributed evenly throughout the system without the need for electricity to power the pumps.