TYFO: A refrigerant is a product that changes phase from liquid to gas to remove heat energy and cool the environment. That’s how it refrigerates. Natural refrigerants include ammonia, carbon dioxide, water, and hydrocarbons. These substances occur in nature. In contrast, chlorine and hydrofluorocarbons are artificial refrigerants.
Cooling brine is another somewhat older term for coolant. A traditional cooling brine is a water-based sodium chloride solution. Cooling brines are thus nothing more than water-based salt solutions. Due to their ability to be chilled far below the freezing point of water, they are used to cool equipment.
Coolants and heat transfer fluids, from a purely physical standpoint, are both doing the same thing—they’re transporting heat energy. Depending on whether the goal is to increase or decrease temperatures at a specific location, we call them either a coolant or a heat transfer fluid. They serve to move heat or cold (the absence of heat) from one place to another. But they don’t generate any heat themselves.