Due to global warming, chillers have now-a-days become a necessity of any industry. For instance, if air conditioning system of an organization or industry fails or goes haywire, people become helpless due to hot temperatures if immediately an alternative arrangement is not provided. During summer, particularly, a poor or non-working cooling system could potentially spoil people’s holidays leading to maligning organization’s or hotel’s reputation.
Inefficient chillers can waste significant amount of electricity, and even modest improvements in efficiency may yield substantial energy savings and attractive paybacks.
However, it’s important to select a chiller (and its associated efficiency) carefully by buying a chiller that is highly efficient. However, it may not be cost-effective in all cases. It is also important to remember that chillers are actually part of a chilled water system, and the efficiency and control of pumps and cooling towers can have a significant impact on overall efficiency.
Maximizing the efficiency of the chiller alone does not ensure that the system will operate efficiently. To maximize cost-effectiveness, we recommend analyzing the entire chilled water system as well as exercising care in specifying the efficiency of the chiller itself.
Understanding of Specification Before Purchasing a Chiller
Tons: One ton of cooling is the amount of heat absorbed by one ton of ice melting in one day, which is equivalent to 12,000 Btu/h or 3.516 thermal kW.
kW/ton Rating: Commonly referred to as efficiency, but actually power input to compressor motor divided by tons of cooling produced, or kilowatts per ton (kW/ton). Lower kW/ton indicates higher efficiency.
Coefficient of Performance (COP): Chiller efficiency measured in Btu output (cooling) divided by Btu input (electric power). Multiplying the COP by 3.412 yields the energy-efficiency ratio.
Energy Efficiency Ratio (EER): Performance of smaller chillers and rooftop units is frequently measured in EER rather than kW/ton. EER is calculated by dividing a chiller’s cooling capacity (in Btu/h) by its power input (in watts) at full-load conditions. The higher is the EER, the more efficient is the unit.
ARI Conditions: Standard reference conditions at which chiller performance is measured, as defined by the Air-Conditioning and Refrigeration Institute (ARI): 44oFF for water leaving the chiller and, for water entering the condenser, 85oF at 100 percent load and 60oF at zero percent load.
Integrated part-load value (IPLV): This metric attempts to capture a more representative ‘average’ chiller efficiency over a representative operating range. It is the efficiency of the chiller, measured in kW/ton, averaged over four operating points, according to a standard formula.
In most manufacturing and workplace buildings, chillers are the solitary widespread energy-using component. In many facilities, more than 70 percent of annual electricity use can be attributed to the building chillers. So, proper operation and maintenance of the building chillers should be a high priority in any facility energy management program. It is surprising, however, to see just how often chillers are operated or maintained inefficiently or ineffectively, resulting in higher energy costs, lower system performance and reliability, and decreased equipment life.
While many factors contribute to decreased chiller efficiency, the five most common ones include poor operating practices, ignored or deferred maintenance, ignored cooling tower maintenance, oversizing, and ignoring alternate-fuel chillers. While each of these factors poses a real and significant threat to chiller efficiency, all can be easily controlled or eliminated by maintenance managers.
Under Loading or Overloading
Without knowledge of proper operating practices not only can decrease the chiller efficiency, but also chiller life.
Means such practices are the result of two situations: trying to get a chiller to do something that
- High/low flow rate: Providing more cooling water to a facility is to increase the rate of chilled water flow through the chiller. The belief is that with a higher flow rate, more cooling water will be available. But practically, increasing the flow rate through a chiller beyond the manufacturers stated limit actually reduces the operating efficiency of the chiller.2.Flow rate: Equally important, flow rates higher than those recommended increase the rate of erosion in the chiller’s tubes, leading to early tube failure.
Prevention is better than cure (Ignorance leads to big loss rather than small saving)
It is always advisable to think and take corrective action on future problems. Good practices are important to the efficient operation of all building equipment; there are few areas where this is more evident than in the maintenance of building chillers.
Most new, high efficiency centrifugal chillers carry a full-load efficiency rating of approximately rated kW per ton. If that chiller is well maintained, in five years it can be expected to have a full-load efficiency of 55-60 %. On an annual basis, poorly maintained chiller will use 20-25% more energy annually to produce the same cooling.
Corrosion and Solutions
Most chiller tubes are copper, and experience galvanic corrosion due to two metals being dissimilar. The corrosion and loss of carbon steel can affect the performance of the chiller due to hard water or poor water quality resulting in flow issues and sediment buildup. This will finally lead to damage of the tube and refrigerant loss. To fight this problem as mentioned in many research paper, eco-friendly, chemical-free treatment with the help of ‘Advance E-water Descaler’ device can solve hard water problem 70-85 % without adding any chemical or extra components of the chiller.
| BEFORE | AFTER | BENEFITS |
 |  | Cooling Tower Fins remains rust and scale free. Faster cooling and maintain, Delta T and Heat transfer efficiency. |
 |  | Boiler tubes also remains scale free and saves life of boiler tubes Increase efficiency |
With ‘Advance E-water Descaler’, we carry a large variety of products to get the machinery working to prevent downtime and dissatisfaction. It is one of the cheapest solutions in the world offering the best results in the market. It is composed of hydrogen and oxygen. As water gets contaminated by the substances with which it comes into contact, it is not available for use in its pure state. To some degree, water can dissolve with every naturally occurring substance on the earth. Because of this property, water has been termed a ‘universal solvent.’ Although beneficial to mankind, the solvency power of water can pose a major threat to industrial chillers, laboratory chillers, process chillers and other cooling systems. Corrosion reactions cause the slow dissolution of metals by water. Deposition reactions, which produce scale on heat transfer surfaces, represent a change in the solvency power of water as its temperature is varied. The control of corrosion is a major focus of water treatment technology for all chiller systems. Facilities managers, lab personnel, and maintenance engineers often ignore scaling and corrosion issues.
Conclusion
Overall, the water used in a chiller system should be of the best quality available. As a general rule, water treated through ‘Advance E-water Descaler’ is better than soft water particularly for industrial applications, which is far better than hard water. Some users resist the use of demineralised water because of the high cost and common belief is more aggressive or corrosive than raw or softened water. So, intermediate solution is water treated not with the help of costly DM Plant or RO Plant but economically viable technology ‘E-water Descaler’ is the next generation solution. Although it is true that untreated, oxygenated demineralized water is very corrosive, corrosion inhibitors passivate metal surfaces and remove dissolved oxygen resulting in final system water that is non-corrosive.
AUTHORS CREDIT & PHOTOGRAPH
Prof Gaurang Sharma
Professor,
BVM Engineering College, V V Nagar, Anand, Gujarat
