03 Mar 16 Chilled water is commonly used in industrial processes such as aluminum anodizing, mold cooling and plating applications as well as the vast majority of large commercial buildings. Any good energy conservation strategy should include monitoring the system efficiency but there are additional benefits in doing so. When one of these machines goes down it’s like giving your budget the ole one two. Not only is production down… the cost of the repair itself can be a wallet buster.
Many might believe that a great many catastrophic failures occur without warning, but this is simply not true. The fact is that the vast majority of breakdowns provide ample warning if you know what to look for. The simple fact is that long before almost every significant breakdown, there will be a glaring change in system efficiency. So not only is it a good idea to know how efficient your chilled water systems are for energy saving reasons, experience shows that by acting on efficiency change, breakdowns will almost never happen.
So how does one measure efficiency of a chilled water system?
Speaking in terms of Imperial units the efficiency of a chilled water system is normally measured in KW/Ton. Basically, this is a measure of how much electrical power is needed to produce a certain amount of cooling.
To calculate tonnage:
Tons = 12,000 / 500 * GPM * TD
Where:
TD is the temperature of the water entering and leaving the chiller evaporator
GPM is the gallons per minute flow rate going through the chiller
12,000 and 500 are constants in the equation
Divide the result of this calculation into the kilowatts the chiller is consuming and you get KW/Ton efficiency.
Most chilled water systems will automatically unload as needed, which means that the KW/Ton will change when the load on the chilled water system changes. Therefore, it is important to benchmark how many KW/Ton the chilled water produces at varying loads under normal operation. This will not only help you understand how much your chiller costs to operate it will also give you the tools for an early warning sign of impending failure.
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