Thermal fluids are substances that transfer heat efficiently in various applications, such as heating, cooling, and energy generation. They can be liquids or gases and are often used in systems like heat exchangers, solar thermal systems, and geothermal energy to manage temperature and energy flow. These fluids are designed to have specific properties, such as high thermal conductivity and stability at different temperatures. Common examples include water, oil, and specialized synthetic fluids. The choice of thermal fluid depends on the operating conditions and the desired efficiency of the thermal system.