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From: Food Quality & Safety magazine, August/September 2010

Reduce Water Usage, Eliminate Excess Waste

Intelligent process cooling can reduce water use by up to 98%

by Al Fosco

The food and beverage processing industry is known as the largest industrial user of water, consuming up to 20,000 gallons of water per ton of product, according to the North Carolina Division of Pollution Prevention and Environmental Assistance. And, with over 17,000 food and beverage processors in the United States alone, curbing this dependence on a community’s clean water supply is a top concern.

Predicted environmental challenges, such as a global water shortage, make it even more important to analyze the industry’s demand for water as a principal ingredient, cleaning source, transportation conveyor, sanitizer, and temperature regulator. Some of the ways processors currently use water include:

  • critical washing and rinsing in the fruit and vegetable sector (accounting for 50% of water use);
  • meat processing, with minimum cleaning requirements set by the United States Department of Agriculture;
  • as a primary ingredient in the beverage sector;
  • showering the product and removing heat during the pasteurization process;
  • keeping foods frozen year round in cold storage units; and
  • in packaging processes like thermoforming, blow molding, or vacuum forming.
In hot weather, outside air passes through the adiabatic chamber before reaching the heat exchanger. In this chamber, a fine mist of water is pulsed into the incoming air stream. The mist evaporates instantly, cooling the air before it impinges on the cooling coils that carry the process water.
In hot weather, outside air passes through the adiabatic chamber before reaching the heat exchanger. In this chamber, a fine mist of water is pulsed into the incoming air stream. The mist evaporates instantly, cooling the air before it impinges on the cooling coils that carry the process water.

With all these critical uses, processors need to find other places for water savings or face the negative impact of water shortages on their future operations.

Food and beverage manufacturers can take proactive measures now to conserve on resources and prevent these issues from affecting their plants. One way to do this is by evaluating existing process cooling technology.

Many facilities still utilize traditional cooling towers and central chillers for their process cooling needs, even though these inefficient cooling systems rank high on the list of water-related problems cited by the U.S. Food and Drug Administration and other regulatory bodies. A 100-ton cooling tower consumes 1 to 1.5 million gallons of water a year, water that is often contaminated. Newer, closed-loop technology seeks to reduce this unnecessary and excessive waste of clean water resources.

Traditional Cooling Tower Disadvantages

Water use isn’t the only challenge of a cooling tower/central chiller system. Such a system requires heavy maintenance and consumes unnecessary energy and chemicals, resulting in higher costs for facilities, lower productivity, and potentially even contaminated products.

When utilizing an open-loop cooling tower system, process water is far from ideal. Extremely dirty water filled with dust and other airborne contaminants is a common occurrence. Cooling towers also suffer from solid deposits, gases, algae, bacteria/Legionella, microbiological growth, scale accumulation, and oxidation. And all of these issues must be fixed with chemicals.

The actual consumption of water occurs as it evaporates or as the chemically treated water is dumped down a drain, making it a costly issue for food and beverage manufacturers. Given environmental issues, inefficient technology, and ever higher food quality standards, food and beverage manufacturers must concentrate their efforts on changing their ways.

The Closed-Loop Alternative

One alternative to a cooling tower is a concept known as intelligent process cooling. Food and beverage manufacturers using this process can realize big savings on water and energy, in addition to reducing waste. The technology works by means of a closed-loop, dry-cooling system. Proven for years in Europe, where water restrictions have been far more limiting, it is now is starting to gain popularity in North America.

This system often provides up to a 98% reduction in process cooling water. For example, it uses only 20,000-40,000 gallons per year, compared to a 100-ton cooling tower’s annual use of up to 1.5 million gallons. Where applicable, the system also reduces energy consumption by up to 95% compared to equivalent capacity refrigerated water chillers, making it a strong consideration for food processors looking for more sustainable options.

With this technology, manufacturers can expect water-friendly results that include:

  • a closed-loop design that ensures the water is never exposed to outside elements for contamination or evaporation and never disposed of into groundwater;
  • water returning from the process that is re-pumped into heat exchangers and cooled with ambient air flow, providing clean water at the right temperature year round; and
  • advanced controls that ensure the most efficient use of water, even during extremely hot and cold weather conditions.
A closed-loop, dry-cooling system like the one shown here can provide up to a 98% reduction in process cooling water. For example, it uses only 20,000-40,000 gallons per year, compared to a 100-ton cooling tower’s annual use of up to 1.5 million gallons.
A closed-loop, dry-cooling system like the one shown here can provide up to a 98% reduction in process cooling water. For example, it uses only 20,000-40,000 gallons per year, compared to a 100-ton cooling tower’s annual use of up to 1.5 million gallons.

Besides its closed loop construction, this technology operates differently than other options because of what is called an adiabatic chamber. To maintain water below a set point in hot weather (85°F or above), outside air passes through the adiabatic chamber before reaching the heat exchanger. In this chamber, a fine mist of water is pulsed into the incoming air stream. The mist evaporates instantly, cooling the air before it impinges on the cooling coils that carry the process water; hence the term “dry-cooling.” This chamber drops the temperature to at, or below, the set point.

This fine mist, the only consumed water in the system, is only activated in temperatures over 85°F. Because of this, the system runs for much of the year without needing more water than it contains, using it over and over within the closed-loop process.

Intelligent Controls

An intelligent control system makes any necessary adjustments, seeking optimized equipment operation and conservation of resources. It takes into account real-time ambient temperature and continuously adjusts the system’s fan speed, adiabatic functions, free-cooling valve, and pumping stations, all without the need for an operator.

During colder months, in situations in which antifreeze is not acceptable, the system has a fully automatic, self-draining option that protects it from freezing. It also provides free cooling when used in conjunction with chiller water systems, which means the compressors turn off when the outside air temperature drops below a set point, and the system uses ambient temperatures to cool the process water.

Recent updates to this process have improved heat rejection through a redesigned and more efficient adiabatic chamber. The latest iteration features an enhanced, V-shaped adiabatic chamber that allows for greater, unrestricted airflow into the unit. This produces greater overall cooling capacity, better humidification of the air in the adiabatic chamber, and reduced air pressure within the cooling chamber.

As the food and beverage industry faces environmental challenges, rising sustainability objectives, and higher quality requirements, closed-loop dry-cooling systems may be the answer.

Fosco is industrial markets sales manager for Frigel North America, a global manufacturer of process cooling and temperature control equipment. Reach him at a.fosco@frigel.com, or for more information, go to www.frigel.com/na.

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