Is there an ideal system for keeping an electrical enclosure cool? As we have already seen, the components inside an electrical panel produce heat due to the Joule effect, which needs to be dissipated in order to avoid overheating and related damages.
Fandis offers a wide range of cooling and ventilation solutions for enclosures on board, depending on the design needs. Today we distinguish the main systems, describing for each the characteristics in order to choose the most suitable one in different situations. For example, it might be appropriate to calculate the thermal balance of the electrical cabinet before making a final choice.
Cooling of the enclosure with natural ventilation
Natural ventilation is a technique based on air flow, which enters the lower part of the cabinet, heats up due to heat exchanges with the components and, thanks to the dilation of the molecules, tends to rise, until it reaches the ejection grid. It’s preferable that this opening is located on the top and not on a side wall, to follow the normal thermal flow of the air. If, however, both the slots are on vertical surfaces, they must be on opposite walls.
This is the least effective system, because it does not allow a real control of the air flows, nor of the relative humidity. The solution is recommended only if the internal design temperature is at least 10°C higher than the external one.
Cooling of the electrical panel with forced ventilation
Forced ventilation uses fan filter units (fan + filter) or individual fans, to forcibly convey the air in the electrical cabinet. This solution allows controlling the flow of air coming from the outside, which is mixed with the one present inside the cabinet, to cool it. It’s an effective system, but only if the conditions of the installation environment are favorable, such as:
- the room temperature must always be at least 5°C lower than the one desired in the enclosure;
- the relative humidity in the installation environment must never exceed 60%;
- the amount of contaminants in the installation environment must not be excessive (a system not very suitable for chemical industries, wood processing, etc.).
The fan filter unit, like those of the Virdis series, can be installed on a cabinet wall, in the lower area if it works in compression (direct air flow) or higher if in suction (reverse air flow). There are different types of installation combinations, which we invite you to read in this article. If, instead, the problem is the installation space, an excellent solution could be a roof exhaust unit.
Cooling of the electrical cabinet with cooling units
The use of a cooling unit inside the electrical cabinet is an almost obligatory choice, in case the external temperature is higher than the one desired internally or when the power to be dissipated is very high. The cooling units for electrical panels are thermal machines that allow to control both the temperature and the humidity and are therefore the best solution for outdoor installations, which have high peaks of relative humidity, problems related to the dew point, cooling and dehumidifying the air at the same time, avoiding dangerous phenomena, such as corrosion.
Cooling of the electrical enclosure with TCU thermoelectric units
The thermoelectric units, or TCU, are heat pumps that exploit the Peltier effect to convey and dissipate thermal power. The thermoelectric unit is composed externally by two ceramic plates and inside by copper plates, connected to the ceramic part with semiconductors. The power cables must be connected to the semiconductors (Peltier modules): the positive pole coincides with the heat absorption side, while the negative pole determines the release side and needs a heat sink to avoid overheating harmful to the thermoelectric unit itself.
This system is reversible, simply by changing the polarity of the electrical connection, allowing it to heat up, but also to cool. During the design phase, the designers of thermoelectric units optimize a single heat exchange direction, the one recommended for use.
TCUs are available for nominal refrigeration powers of less than or equal to 200W. Up to this value, they are preferable to cooling units, because:
- Do not require maintenance;
- Do not use synthetic refrigerants (used in cooling units), with a strong environmental impact.
Cooling of the electrical panel through water-air exchangers
The water-air exchangers separate the air flow inside the cabinet from the external one. The installation on electrical panels is recommended in environments very contaminated by dust or chemical agents, because the external air is never in contact with the air inside the panel, preserving the components. The water, having a high specific heat (4,186kJ / kgK), turns out to be a good heat transfer fluid and it’s effective in heat exchange.
The installation of water-air exchangers is more complex than the previous systems mentioned above, as it is necessary to:
- design a hydronic network for the transport of water to and from the exchangers;
- keep the supply water towards the exchanger at the required temperature.
The water-air exchangers, therefore, turn out to be an excellent solution in places with a high rate of contaminants in the installation environment and they are a particularly advantageous solution from an energy point of view, when the water used can be taken at the required temperature directly from natural sources (lakes, rivers, etc.).
Thermoelectric units and heat exchangers are all part of our Bordos range.
To learn more about the Fandis ventilation and cooling systems of electrical panels, visit our website fandis.it or leave a comment to this article. One of our technicians will answer you as soon as possible.