Which cooling method should you use?

Many processes require cooling, either for the product being processed or for the equipment to achieve optimal performance. And, a number of water sources -- including tap or well water, tower water, building chilled water or a recirculating chiller -- are available. How do you know when to invest in a dedicated cooling system? The answer lies in a thorough evaluation of your process and a look at your options.

Water is a scarce and expensive natural resource. Drought conditions and regional restrictions on water use make it essential that processors do their part to conserve. More importantly, many demanding applications such lasers, welders and other temperature-sensitive operations require a cooling source that can provide stable temperature, pressure and flow.

The four most common cooling water sources all have advantages and disadvantages. Taking a closer look should help you narrow your choices.

A recirculating chiller can provide a dedicated cooling water source for a specific application.

Tap and Well Water

Provided to your plant by your municipality or well, tap and well water are seemingly free of charge. However, just the opposite is true, as you must pay for the water itself, and you may have to pay a sewer charge as well.

Advantages -- Seemingly plentiful supply. Works well for many applications. Suitable for hydraulic fluid cooling, plastics, paper and general process cooling where stability is not an issue. No power consumption. Reliable.

Disadvantages -- Expensive, limited natural resource. Unclean. Unstable temperature, flow and pressure. Illegal to use in some regions. No pay back. Not suitable for lasers, welders, spindles or applications where temperature stability is important.

Tower Water

A water tower can eliminate the waste associated with tap and well water because it provides a closed loop. However, water temperature is not stable because the tower is located outdoors, vulnerable to changes in ambient temperature.

Advantages -- Closed loop, no waste. Tower will pay for itself over time if replacing tap water. Relatively inexpensive system. Suitable for hydraulic fluid cooing, plastics, paper and general process cooling where stability is not an issue. Small or no power consumption. Reliable.

Disadvantages -- Unstable temperature, flow and pressure. Fluid temperature can be high during the summer in warm climates. Must be treated. Not suitable for lasers, welders, spindles or applications where temperature stability is important.

Building Chilled Water

A refrigerated fluid circulator usually used to air- condition a building, this compressor-based cooling system is similar to an air conditioner. The main difference is that a building chiller cools water rather than air. Water temperature is controlled, so it can maintain cooling water at a setpoint within +/-5 to 10oF.

Advantages -- Closed loop, no waste. Temper-ature controller provides stable water temperatures. A building chiller system can pay for itself over time if replacing tap water. Suitable for hydraulic fluid cooling, plastics, paper, welders, some lasers, machine tools and spindles.

Disadvantages -- Must meet the needs of the entire plant rather than one or two specific processes. Can be expensive. Tem-perature, flow and pressure may not be stable enough for some processes. Condensation may occur due to low recirculating temperatures. Mechanical and electrical components can cause reliability issues compared to tap or tower water. Higher power consumption than tap or tower water. Should be filtered. Not suitable for some lasers or applications where high temperature stability is important.

Refrigerated Recirculating Chiller

Usually dedicated to one or two processes, a refrigerated recirculating chiller is similar to a building chilled water system in that it is a compressor-based cooling system with a temperature controller and recirculating pump. Its main advantage is that its use is dedicated to a specific process or two, and therefore it can be configured to satisfy process requirements.

Advantages -- Closed loop, no waste. Configured specifically for the application. Short payback if replacing tap water. Relatively inexpensive. Suitable for any application.

Disadvantages -- Mechanical and electrical components can cause reliability issues compared to tap or tower water. Higher power consumption than tap or tower water.

Once you evaluate your process, you cooling choices should be clear. Evaluating your volume, temperature stability, reliability and payback requirements should point you in the right direction.