●Circulating fluid, constant temperature circulating fluid
Fluid that circulates among the customer’s equipment, with temperature controlled by a chiller.
Taking freezing temperature, boiling point, electrical insulation properties and so on into consideration, clear water, deionized water, ethylene glycol aqueous solution, fluorinated fluids, etc., can be selected depending on the application.
●Clear water
Water that has been filtered and distilled and any impurities eliminated. It is also known as purified water.
●Cooling capacity
The volume of heat (heat energy) that temperature control equipment can absorb (cool) per unit of time, at an arbitrary temperature.
●Degree of viscosity
Thickness of a fluid. The units used to express absolute degree of viscosity are [Pa·s] units, but it is often expressed within the CGS system of units with [P] (Poise).
1 [Pa·s] = 10 [P]
The value obtained by dividing absolute degree of viscosity by density is called the kinetic viscosity. This can be measured in [m2/s] units, but in general, [St] (Stokes) are used.
1 [St] = 0.0001 [m2/s]
●Deionized water
Water that has had any impurities or ion elements removed. It is obtained by removing ion elements with ion exchange resin, after filtering out impurities with a particle filter. Its theoretical specific resistance has a limit of 18.3 [MΩ·cm], but it is impossible to actually attain this value. As a general rule, water with a specific resistance of 1 to 10 MΩ·cm is referred to as deionized water.
●Density, specific gravity
The weight per unit of volume, measured in units of [kg/m3].
Specific gravity is the ratio of the density of a given substance to the density of water (1.0 [g/cm3]), and is a dimensionless quantity. When expressing this quantity within the CGS system of units, density and specific gravity have the same value.
●Electrical conductivity
A value indicating the ease with which electricity passes through a liquid, and is inversely proportional to the specific resistance. The unit used is [S/m], incorporating [S] (Siemens), the opposite of [Ω] (resistance).
At 25°C, the electrical conductivity of theoretically 100% deionized water is 0.055 [μS/m].
●Ethylene glycol aqueous solution
Ethylene glycol is a type of alcohol, and adding it to water causes the freezing point of the water to drop. It is a major ingredient in antifreeze for automobiles. At a concentration of 60%, the freezing point drops to –40°C or lower, but the viscosity increases as the temperature drops, so taking fluidity into account, it is practical to consider about –20°C as the minimum temperature.
By adding ethylene glycol to deionized water, it is possible to raise the fluid’s specific resistance, so it can be used for applications where circulating fluid with high insulating properties is desired.
●Fluorinated fluids
Inert fluids in the fluorine series. There are many types, including perfluoropolyether (PFPE), perfluorocarbon (PFC), hydrofluoropolyether (HFPE), and hydrofluoroether (HFE), but they share the characteristic of high electrical insulation properties, and grades can be selected with appropriate fluidity even at low temperatures, such as –100°C, and high temperatures, such as 200°C and above.
They are chemically inert and non-poisonous.
Products are sold on the market, such as Fluorinert?, made by 3M, and GALDEN?, made by Solvay Solexis.
●Fluorinert?
The product name of a fluorinated fluid manufactured by 3M.
Its basic structure is a perfluorocarbon, but it has a wide variety of chemical structures, and various grades can be selected with differing temperature and viscosity ranges.
●GALDEN?
The product name of a fluorinated fluid manufactured by Solvay Solexis. It is a perfluoropolyether with a high polymer compound, and various grades can be selected with differing temperature ranges and viscosity ranges depending on the degree of polymerization.
●Heat
Terms such as heat, heat load, cooling capacity, etc., that are used in this catalog, indicate quantities of heat that can be absorbed or radiated per unit of time. As a result, the units employed are [W] = [J/s] (work rate) or [kcal/hr].
1 kW = 860 kcal/hr
●Heat load
→ Cooling capacity
●Propylene glycol aqueous solution
Propylene glycol is a type of alcohol, and adding it to water causes the freezing point of water to drop. Like ethylene glycol, it is a major ingredient in antifreeze for automobiles.
It has lubricating properties, and is characteristically non-volatile.
●Specific heat, specific heat capacity
The heat energy required to increase the temperature of an object by a certain temperature interval, under specific pressure and volume conditions.
The specific heat of water: 1 [cal/g·K] = 4.184 x 103 [J/kg·K]
●Specific resistance
A value indicating the electrical insulating properties of a liquid, and the unit used is [Ω·cm]. When expressing the specific resistance of deionized water, it is sometimes called “DI level.”
At 25°C, the specific resistance of theoretically 100% deionized water is 18.3 [MΩ·cm].
