Water cooling

Lore & Background

Water cooling has been employed for industrial heat removal, including in steam power stations where large volumes of water are required to condense low-pressure steam. Many electric power plants use millions of gallons of water per day for cooling, which may alter natural water environments and create new environments. Thermal pollution of rivers, estuaries and coastal waters is a consideration when siting such plants. Once-through cooling systems may be used on very large rivers or at coastal and estuarine sites, relying upon an ample supply of river water or seawater. These facilities are built with intake structures designed for bringing in large volumes of water at a high rate of flow, which tend to also pull in large numbers of fish eggs and larvae.

Water cooling systems may be recirculating (open or closed) or single-pass once-through cooling. Recirculating systems are open if they rely upon evaporative cooling or closed if heat removal is accomplished in heat exchangers with negligible evaporative loss. A heat exchanger or condenser may separate non-contact cooling water from a fluid being cooled, or contact cooling water may directly impinge on items like saw blades. Water accelerates corrosion of metal parts and is a favorable medium for biological growth. Dissolved minerals in natural water supplies are concentrated by evaporation to leave deposits called scale. Cooling water often requires the addition of chemicals to minimize corrosion and insulating deposits of scale and biofouling.

Reader's Guide

Water cooling's significance lies in its ability to efficiently remove waste heat from industrial processes, power generation, and high-performance computing. Its high specific heat capacity and enthalpy of vaporization allow effective heat transfer over distance with low rates of mass transfer, and the option of evaporative cooling in cooling towers or cooling ponds. However, water's properties also introduce challenges: it accelerates corrosion, promotes biological growth, and forms scale from dissolved minerals. These issues necessitate chemical treatment with corrosion inhibitors (such as zinc, chromates, and phosphates) and biocides (such as hypochlorite), which raise environmental concerns regarding toxicity and eutrophication in blowdown or once-through cooling water returned to natural aquatic environments. The legacy of water cooling includes its widespread adoption in power stations, where thermal pollution and intake impacts on aquatic life are ongoing considerations. In personal computers, water cooling offers lower CPU and component temperatures compared to air cooling, though it remains limited to high-end systems. The balance between efficient heat removal and environmental management continues to define the use of water cooling across applications.

Did You Know?

• Water has unusually high specific heat capacity among commonly available liquids at room temperature and atmospheric pressure.
• Water's high enthalpy of vaporization allows efficient evaporative cooling in cooling towers or cooling ponds.
• Chlorine may be added as hypochlorite to decrease biofouling, but is later reduced to chloride to minimize toxicity of blowdown or once-through cooling water.