Principles of selecting radiators for a room

A radiator transfers heat to a room in two main ways: through convection (heating the layer of air near the radiator’s walls, followed by the convective movement of warm air upward and cold air downward within the heated room) and through radiation (radiation, approx. 5%–30% of the energy emitted). This is because every object with a temperature above absolute zero (0 K, or -273.15°C) emits electromagnetic radiation, including thermal radiation, from its surface.

Main parameters of a radiator

Three basic parameters characterizing the operation of a radiator can be distinguished:

Tz – supply temperature – the temperature of the medium entering the radiator

Tp – return temperature – the temperature of the medium leaving the radiator

m – mass flow rate of the medium – the amount of medium flowing through the radiator per unit of time in kg/s (for water in a central heating system, a density of 1 kg/dm³ can be assumed).

By multiplying the temperature difference, the flow rate, and the specific heat of the medium (the amount of thermal energy stored per unit mass of the medium – 4.19 kJ/kgK), we obtain the radiator’s power. However, the size of the radiator is selected to ensure the transfer of an appropriate heat flux (thermal power) under given conditions. However, one cannot rely solely on parameters set “in advance,” because the radiator—in the dominant convective range—will operate at the heat output allowed by the difference between the average surface temperature of the radiator and the temperature of the heated room.

Another factor significantly affecting the radiator’s output is the heat exchange surface area—the larger the surface area, the greater the amount of thermal energy transferred to the room. Therefore, the heat output of the radiator is proportional to its surface area and depends on the supply temperature and the flow rate of the heat transfer fluid. The return temperature, on the other hand, is determined by the heat flux (power) absorbed by the radiator from the heat transfer fluid and transferred to the room—that is, by all of the above parameters.

Another very important factor in selecting the size of a radiator is its location in the room and the ability for air to circulate freely around the radiator’s surface.

How to select the radiator’s power?

The power of the heating element in the room must be such that, at the design outdoor temperature for the given region—in accordance with the “Division of Poland into Climate Zones” per the PN–EN 12831 standard – it ensures the required temperature for the given type of room, in accordance with the requirements of the Regulation of the Minister of Infrastructure on the conditions to be met by buildings and their location (Journal of Laws 2002 No. 75, item 690, as amended). The heating capacity of the radiator must cover all heat losses from the room due to heat transfer through partitions (to the outside, to the ground, to other rooms) as well as the heat demand for heating the ventilation air.

Ferro Radiators

Radiators - depending on their intended use and output - come in various designs, shapes, and surfaces. Among them, the most popular are panel radiators, e.g., FERRO steel radiators (Type C with side connections, Type V with bottom connections, and an integrated valve-and-pipe system equipped with an M30x1.5 thermostatic insert (Heimeier type), as well as plugs and air vents).

Steel panel radiators are constructed from steel sheet in the form of two welded plates shaped so that channels are formed between them, through which the heating medium flows, transferring heat to the surrounding air. The channels are equipped with fittings such as: connectors for joining the plates, ports for connecting the radiator to the central heating system, air vents, and, depending on the version, valves . The radiators are designed for heating rooms in residential, office, public utility, industrial, and service buildings, as well as other facilities with normal humidity levels. They can be used in closed-loop water systems (or open-loop systems up to 30 kW, provided an inhibitor protection system is installed). Maximum operating parameters: pressure up to 1.0 MPa (10 bar) and temperature up to 110°C. Radiator finish: dip cataphoresis followed by electrostatic powder coating and subsequent oven curing.

Bathroom radiators - tubular, flat, or curved - are ladder-shaped with two vertical main pipes that distribute the medium to the cross pipes. The main pipes at both ends can be fitted with connectors, valves, air vents, and an electric heater used outside the heating season. They are finished with white paint or a chrome coating.

You now know the different types of radiators and the parameters that affect their efficient operation. With this knowledge, you can choose a product that meets your expectations and those of your household members. At Ferro, you’ll find radiators that combine functionality with high quality and impeccable aesthetics. Trust our years of experience and choose a top-of-the-line product!