There are several main ways to dissipate heat in a PLC control cabinet:
Air cooling
Natural air cooling: heat is dissipated by allowing air to flow naturally through the heat source in the control cabinet and transferring heat to the air. In the design of the control cabinet, vents, shutters and other structures will be reserved, and the principle of hot air rising and cold air falling will be used to allow air to circulate naturally and take away heat. This method is suitable for some small PLC control cabinets with low heat generation, or places with low heat generation requirements, low ambient temperature and relatively stable. The advantages are that no additional power equipment is required, low cost, no noise, and simple maintenance; the disadvantages are that the heat dissipation efficiency is relatively low and is greatly affected by ambient temperature and air flow speed.
Forced air cooling: install a fan or air duct system in the control cabinet, and accelerate the air flow through the rotation of the fan, thereby quickly taking away heat. According to the size and heat generation of the control cabinet, fans of appropriate quantity and specifications can be selected, such as axial flow fans, centrifugal fans, etc. Special air ducts can also be designed to guide air to flow along a specific path to improve the heat dissipation effect. This method is suitable for most PLC control cabinets, especially for occasions with high heat generation and high heat dissipation requirements. Compared with natural air cooling, it has higher heat dissipation efficiency and can effectively reduce the temperature in the control cabinet, but it needs to consume a certain amount of electricity, and the fan has certain noise and maintenance costs, such as regular cleaning of fan blades and replacement of damaged fans. 57.
Liquid cooling
Direct liquid cooling: The coolant is directly in contact with the heat-generating components, and the heat is removed by the circulation of the coolant. For example, a liquid cooling radiator is installed on the surface of the key heat-generating components (such as power modules, power modules, etc.) in the PLC control cabinet. There is a coolant channel inside the radiator. The coolant flows in the channel, absorbs the heat of the heat-generating components, and then dissipates the heat to the outside through an external cooling device (such as a cooler, cooling tower, etc.).
Indirect liquid cooling: The heat in the control cabinet is transferred to the coolant through a heat exchanger, and then the coolant takes the heat out of the control cabinet. A heat exchanger is set in the control cabinet. The heat exchanger exchanges heat with the air or heating components in the control cabinet, and transfers heat to the coolant in the heat exchanger. The coolant is transported to the external cooling equipment through a circulating pump for heat dissipation. Liquid cooling has high heat dissipation efficiency and is not affected by the external ambient temperature. It can stabilize the operating temperature of the control cabinet and is suitable for some large PLC control cabinets with extremely high heat dissipation requirements and long-term stable operation. However, the system is relatively complex and costly, and the coolant system needs to be regularly maintained to prevent leakage and other problems.
Heat pipe heat dissipation
The heat in the control cabinet is quickly transferred to the outside by using the efficient heat transfer performance of the heat pipe. The heat pipe is a heat transfer element with high thermal conductivity. It is filled with a working fluid. When heated at one end, the working fluid evaporates into steam. The steam quickly flows to the other end under a small pressure difference. After being cooled at the cold end, it condenses into liquid. The liquid then flows back to the hot end through capillary action or gravity. This cycle is repeated to achieve rapid heat transfer. Heat pipe heat dissipation has the advantages of high thermal conductivity, good isothermal properties, arbitrary change of heat transfer area on both sides of the hot and cold sides, and long-distance heat transfer. It is suitable for some PLC control cabinets with high heat dissipation requirements and limited space. It can achieve efficient heat dissipation in a small space, but the cost of heat pipes is relatively high, and there are certain requirements for the installation and use environment3.
Other heat dissipation methods
Heat sink heat dissipation: Install heat sinks on the shell or internal heating elements of the PLC control cabinet to increase the heat dissipation area and improve the heat dissipation effect. Heat sinks are usually made of metal materials with good thermal conductivity (such as aluminum alloy, copper, etc.). Heat is transferred to the surface of the heat sink and then taken away by air. Heat sinks of different shapes and sizes can be designed according to the shape, size and heat generation of the heating element, such as fin type, pin type heat sink, etc.
Air conditioning heat dissipation: Install an air conditioning system in the room or cabinet where the control cabinet is located to reduce the temperature of the PLC control cabinet by adjusting the ambient temperature. This method can accurately control the ambient temperature and provide a stable and suitable working environment for the PLC control cabinet. It is suitable for places with high requirements on ambient temperature, large changes in ambient temperature or where multiple control cabinets are placed together. However, it requires additional air-conditioning equipment and operating costs, and has certain requirements for installation space.
