Coolant is that type of substance that is used for reducing or regulating the system’s temperature that comes in gas or liquid form. The ideal coolant is something that has low viscosity, low-cost, chemically inert, non toxic, has high thermal capacity and neither promotes nor cause corrosion of cooling system. As a matter of fact, few applications for such need it to be good electrical insulator too.
While the phrase coolant is referred often to HVAC and automotive applications, industrial coolant is more of a technical as it’s found in heat transfer fluid that are frequently used in low and high temperature manufacturing applications. The term is covering cutting fluids at the same time. Coolants might be able to stay on its phase, gaseous or liquid or it can even undergo a transition with latent heat that adds to the efficiency of cooling. Now say for example that the latter is put into use to achieve below ambient temperature, then it is known as refrigerant.
Air is a very common form of coolant in the market. There are a couple of ways to which air cooling is used and it’s through passive cooling or also known as convective airflow as well as forced circulation by making use of fans. Hydrogen is used too for high performance gaseous coolant. Because thermal conductivity is higher in comparison to other gases, it is expected to have low density and high specific heat density allowing it to have low viscosity which many rotary machines are taking advantage of due to its vulnerability to windage loss. Currently, many big power plants are using hydrogen cooled turbo generators in their electrical generator.
Inert gases are used as coolants for the gas cooled nuclear reactors. Helium basically has low tendency to absorb neutrons and for that, the odds of it becoming radioactive is less. Carbon dioxide is actually used to be mixed with AGR reactors and Magnox. Sulfur hexafluoride on the other hand is being used for cooling and insulating high voltage power systems similar to switches, transformers, circuit breakers and so on. The steam however could be used where there’s high specific heat capacity that’s required in gaseous form.
A very common type of coolant is water. The low cost and high heat capacity it has makes it ideal for heat transfer medium. Most of the time, technicians are combining it with additives like antifreeze as well as corrosion inhibitors. The antifreeze is a solution made from suitable organic chemical oftentimes diethylene glycol, propylene glycol or ethylene glycol in water. Betaine is of similar coolant with an exception that it’s made from pure plant juice and therefore hard to ecologically dispose or non toxic. Because of the low electrical conductivity of pure de-ionized water, it’s widely used for regulating the temperature on electrical equipment.