COWARD ENVIRONMENTAL SYSTEMS, INC.
500 Birchfield Drive, Suite 501, Mt. Laurel, NJ 08054
856-727-4400 -fax 856-727-4344
e-mail: cesi@cowardenvironmental.com

Optimization

In all our forty business years, we cannot remember a client that purchased a system or component from us "just for fun".

The only reason to make an investment in engineered systems is to, in some way, improve the quality of life of the investor. It may improve his comfort level, production capability or whatever, but he expects a return on his investment.

The more our systems are "optimized" the high the return from each dollar, particularly in cost of operation. This multi-billion dollar industry of ours represents such a consequential part of our economy that optimization within it should not be ignored.

ASHRAE has placed the highest priority on the efficient use of energy. Government has established minimum "EER'S". Foreign competition is forcing production efficiency. All of this motivates us to place system "optimization" near the top of our priority list.

There are few places where this becomes more consequential than in the heat transfer filed:

1. The higher the required refrigerant temperature, the lower the horsepower per ton required. The days of assuming "a 40 degree suction temperature" are over.

2. The colder the air supplied to an occupied space, the lower the air quantity required to satisfy it.

3.The higher the water temperature rise through a cooling coil, the lower the required flow, pump and pipe size.

4. The lower the air quantity required, the smaller the filter and coil face areas required and the smaller fans, fan motors and ducts become.

The proper selection of each system component becomes a "trade-off" against total system cost and it does not assume a straight line relationship. An increase in the size of one component may reduce the size of another and end up proving advantageous. At the point where the two curves cross, optimization has occurred and the greatest advantage has been obtained. This becomes particularly obvious when cost of operation is considered and the "cost-benefit" ratio is computed.

In no place is this more obvious than in the selection of coils where the depth in direction of air flow so directly influences the required cooling (or heating) medium temperature and/or quantity.

1.Each application is plotted on a psychrometric chart.

2.Cooling coils are ten rows deep and with no more than 8 fins per inch.

3. The proper chilled water temperature rise is calculated for each application (the assumption of 45 to 55 degrees is obsolete).

4.The proper hot water temperature is calculated (the assumption of 180 to 160 degrees is obsolete).

5.Wet coil casings and their drain pans are of stainless steel (the use of galvanized steel shortens expected life).

Why not let us help you "optimize" your selections? The computer is a wonderful tool that has made many of the assumptions of prior years, obsolete.

By:

Kenneth W. Wicks

ASHRAE Fellow

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