CHAPTER 14 | Sister Products

Some manufacturers offer additional products that look like cooling towers. They reject heat by evaporating water and even use many of the same components except they employ coil bundles in place of some or all of the wet deck. These ‘coil products’ are:

- Closed circuit cooling towers (aka fluid coolers) used to cool fluids or,
- Evaporative Condensers that condense refrigerant.

Closed circuit towers typically produce the same result as the 'open' cooling tower- that of cooling a water stream from an elevated temperature to a reduced temperature- although other fluids can be cooled. The process fluid is confined within a coil inside the fluid cooler. Heat is passed through the walls of numerous coil circuits to water that is sprayed over the coil(s). The process fluid remains contaminant free while the water on the exterior does the ‘dirty work’ sacrificing itself to evaporation and collecting debris from the airstream.

A small pump mounted on the side of the fluid cooler draws water from the basin and conveys it to the top of the cooler where it is sprayed over the coil.

The closed circuit tower is ideal for cooling equipment with small, hard to clean passageways that would clog with a conventional ‘open’ cooling tower.

The higher water quality comes at a price, however, with the closed circuit cooler costing appreciably more to purchase and operate. The physical size of the cooler is always bigger than an open cooling tower sized for the same duty- possibly much bigger as the approach narrows.

Coils can be made from steel, copper, stainless steel or other- more exotic- materials.

Unlike ‘open’ cooling towers that must be installed at the highest system elevation, fluid coolers can be mounted at any elevation in the system provided the maximum pressure is not exceeded. The most common application for closed circuit towers is as the heat rejecter in water source heat pump systems. (See Ch.15 for more info.)

One common mistake is to apply steel coil coolers to systems that are really open. In other words, systems that are open to the atmosphere at some point. An open system allows air to continually enter causing corrosion of the untreated coil interior reducing heat transfer and causing premature coil failure.

Deionized water will ruin steel coils in very short order. Copper coils work good for DI water.

The Evaporative Condenser is built like a fluid cooler but instead of sensible temperature reduction of a liquid stream, it accepts a vapor (such as compressor discharge in a refrigeration system) and extracts latent heat causing the vapor to condense.

Both products- particularly the evaporative condenser- are worthy of their own technical articles. Additional information will be added as time allows.