Cheap industrial water is a bill most plants still haven't worked out properly. In cooling systems and boilers, water quality directly impacts operating cost and equipment availability.
When it isn't properly treated, the real cost shows up in maintenance spend, unplanned shutdowns, and lost efficiency in industrial processes and steam generation systems.
Specific Heat: Why It Matters
The key point here is water's role in handling industrial heat. Specific heat is a physical property that indicates the amount of thermal energy required to raise the temperature of a unit mass of a substance by one degree:
- Q = amount of heat (in Joules or calories)
- m = mass of the substance (in kg or g)
- c = specific heat (in J/(kg·°C) or cal/(g·°C))
- ΔT = temperature change (in °C or K)
The higher the specific heat, the more heat is carried per unit of mass. Turning that around: the higher the specific heat, the less mass is needed to carry it, which is precisely water's advantage.
Comparison of Specific Heats (Source: NIST Chemistry WebBook)
| Substance | Specific Heat |
|---|---|
| Hydrogen (H₂, gas) | 14.3 J/g·°C |
| Helium (He, gas) | 5.19 J/g·°C |
| Water (liquid) | 4.18 J/g·°C |
| Methanol | 2.5 J/g·°C |
| Ethanol | 2.4 J/g·°C |
| Glycerin | 2.4 J/g·°C |
| Acetic acid | 2.0 J/g·°C |
Notice that among the substances with a higher specific heat than water, two are gases: one very rare (helium) and the other highly explosive (hydrogen). Thermal oils, which are more costly and used only in specific situations, have a specific heat close to 2.2 J/g·°C, lower than water's.
Water for Removing Heat
In cooling systems, large amounts of heat can be pulled out of industrial processes with a quantity of water that can be handled without major issues. A critical example is continuous casting, where the copper mold receives liquid steel at around 1600°C and must be kept between 200 and 400°C. Water enters at very high velocity to remove that heat. Any resistance to heat exchange has the potential to cause process failures and safety risks.
Water as a Heat Source
Within industrial processes, water also carries heat into the process through boilers. Water shines here too, since it has the highest heat of vaporization among commonly known substances (Source: NIST Chemistry WebBook):
| Substance | Heat of Vaporization |
|---|---|
| Water (H₂O) | 2.26 kJ/g (at 100°C) |
| Isopropyl alcohol | 1.02 kJ/g (at 82.5°C) |
| Acetone | 1.16 kJ/g (at 56°C) |
| Ethanol | 0.84 kJ/g (at 78°C) |
| Benzene | 0.394 kJ/g (at 80.1°C) |
The Need for Proper Treatment
Water can also become a source of problems if it isn't properly treated. Scaling, deposition, corrosion and microbiological growth all negatively affect industrial processes.
For example, the impact of just 0.1 mm of CaCO₃ scale on the tubes of a boiler operating at 64 bar reduces heat transfer by around 8%, considering a CaCO₃ conductivity of 2.5 W/(m·K) and a clean overall heat transfer coefficient of 2000 W/(m²·K).
Wasted water is wasted energy. Proper treatment is the foundation of efficiency for any industrial water system.