Hotel Chain Stands By Desuperheating

June 28, 2002
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Many of the favorite resort spots around the globe are found in the tropics. One prominent chain of such hotels/motels — Melia — has more than 400 facilities in 30 countries, including Brazil, Mexico, Italy, Panama, and Spain.

The chain offers executive suites, meeting facilities, sports, and entertainment. But even in a scenic paradise, hotel management must contend with pressing issues such as rising energy costs.

In particular, hotels/motels use considerable amounts of hot water on a daily basis. Owners, managers, and maintenance personnel need practical methods to hold down costs while offering guests air conditioned rooms and ample hot water. Thus, they are among the most open-minded individuals when it comes to new methods of adding to their bottom line without forfeiting comfort.

Sales Engineering, Contracting & Associates (SECA), a design-build mechanical contractor and purchasing agent, has worked with several Melia hotels over the years on various projects. Since the early 1990s, the firm has assisted 10 of the chain’s resorts, improving existing potable water systems and providing significant hot water cost reduction.

Jorge Hernandez, SECA president, turned to Doucette Industries and its desuperheater heat recovery system to help in the energy savings efforts.

The A/C Series Desuperheater/ Water Heater™ heats potable water to 140 degrees F via recovered heat from reciprocating, scroll, and screw compressors.

Figure 1. The internal workings of a desuperheater.

HEAT RECOVERY

Hernandez dubbed the desuperheater the “ultimate accessory” for any mechanical refrigeration system from 5 to 200 tons. The heat recovery unit is designed to heat domestic hot water, taking heat recovered from the refrigeration system to heat water directly rather than using a facility’s boiler system. By capturing 15% to 20% of a system’s heat rejection, the unit is said to be able to heat up to 100% of domestic hot water requirements and dramatically reduce hot water expenses.

“Typical hotel applications use a chiller system to cool water that is distributed throughout pipelines to each room within the hotel. Heat generated during the cooling process is removed, usually through an air- or water-cooled condensing unit,” said Hernandez. “A considerable amount of that heat is recovered by the desuperheater to heat the potable water consumed by kitchens, cleaning, showers, and other needs.

“What’s interesting is how the desuperheater recovers enough heat for the whole motel, making it possible to obtain heated potable water practically for free.”

Hernandez noted that the desuperheater has double-wall copper construction, allowing for separation of potable water from the refrigeration circuit. The double-wall system consists of fluted tubing to create a vent path between tubes so should a tube leak occur, the fluid vents to the atmosphere for early detection. The desuperheater is also designed to eliminate work hardening via its free-floating tube design, thus allowing the inside tubing to expand and contract as needed.

“It’s the vented double-wall construction that provides added security overall,” said John Lebo, Doucette president. “Premature failure can be avoided by using the desuperheater in place of single-wall, plate, or shell-and-tube heat exchangers, because that is where thermal shock can often occur. This creates hardened conditions within heat exchanger tubing and can, ultimately, lead to refrigerant leaks.”

In addition, the desuperheater can be installed with an existing cooling configuration. “They are easy to install for a variety of situations, adding up to 15% more condenser capacity for the overall system,” Lebo said.

WATCHING ELECTRIC BILLS

It is not uncommon for a system with a desuperheater to experience a 5% to 10% reduction in chiller operation costs, as well as better performance and longer compressor life. Hernandez noted, “It depends on the model used and the size of the system; there is considerable savings on electric bills.”

Facilities using the desuperheater often realize a payback period of two years or less, Lebo claimed. “For instance, when installed with a 5-ton system, the desuperheater has the potential to save about $1,260 a year and literally pay for itself within two years. Applying the same unit to a 200-ton system could see savings in excess of $50,000 for a payback in under 10 months.”

The desuperheater is designed with a mechanical, cleanable counterblow system. It is installed in-line with the compressor discharge piping located close to the compressor, to avoid piping costs and pressure drop. The A/C Series referenced in this article can be applied to air- or water-cooled systems using R-22, -404A, and -507, as well as others.

For more information, contact John Lebo, president, Doucette Industries, Inc., 701 Grantley Rd., York, PA 17403-3525; 717-845-8746; www.doucetteindustries.com (e-mail).

Publication date: 07/01/2002

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