Engineered Systems - March 2009 - (Page 45)

Basics For Absorption Chillers COTTONWOOD FILTER SCREENS ™ KEEP COOLING SYSTEMS CLEAN ALL SEASON LONG ”The Green Way to Keep HVAC and Cooling Tower Systems Clean and earn LEED Credits” part-load performance becomes NPLV which has the same equation as the IPLV. Ultimately, the chiller’s energy usage is primarily based upon the “lift” or temperature difference between the chilled water leaving temperature and condenser water leaving temperature. Lowering the condenser water leaving temperature or raising the chilled water leaving temperature will reduce lift and energy usage of chiller, but not necessarily chilled water system. Raising the condenser water leaving temperature or lowering the chilled water leaving temperature will increase lift and energy usage of chiller. CHILLER OPERATING PERFORMANCE As with motor-driven vapor compression chillers, absorption chillers do not operate at the standard operating conditions noted above. Though there are many variables that can be evaluated; for this article, absorption chiller COP vs. part -load percentage and chilled water leaving temperature vs. chiller capacity shall be evaluated. Note that the graphs are illustrative only. It is important that you use the particular chiller performance data for the equipment you are evaluating. Effect of part-load operation on chiller efficiency. Looking at Graph 1, all three types of absorption chillers are most efficient at 50% part load with the single-effect indirect-fired chiller having a 9.4% increase in efficiency; the double-effect direct-fired chiller having a 10% increase in efficiency; and the double-effect indirectfired chiller having a 16.7% increase in efficiency. At part loads below 50%, the chiller efficiencies are lower as the chiller part load is lower. Effect of chilled water leaving temperature. The standard chilled water leaving temperature is 44°. Looking at Graph 2, chiller capacity increases as the chilled water leaving temperature increases. At a chilled water leaving temperature of 48°, the chiller capacity increased 8% for single-effect absorption chiller and increased 9.5% for double-effect absorption chiller as compared to chilled water leaving temperature of 44°. Conversely, the chiller capacity decreases as the chilled water leaving temperature decreases. At a chilled water leaving temperature of 40°, the chiller capacity decreased 14.5% for single-effect chiller and decreased 11.4% for double-effect absorption chiller as compared to chilled water leaving temperature of 44°. ABORPTION CHILLERS AND LEED® The USGBC LEED for New Construction, Version 2.2, has a mandatory prerequisite to reduce ozone depletion by utilizing no CFC refrigerants in new construction and phasing out CFC refrigerants during renovation of existing facilities. Since the two frequently used absorption chiller refrigerants are ammonia and water, absorption chillers meet the Energy & Atmosphere Prerequisite 3, Fundamental Refrigerant Management, requirement of no CFC refrigerants. The USGBC also provides the opportunity for obtaining a credit for Enhanced Refrigerant Management. Understanding some lower ozone-depleting refrigerants are also less efficient, the Energy & Atmosphere Credit 4, Enhanced Refrigerant Management has developed a formula that weighs a refrigerant’s ozone depletion and global warming potentials. If the project’s total installed refrigerant has an average atmospheric impact less than a 100, it is eligible for the credit (See USGBC for further information on formula). The credit also recognizes “natural refrigerants” like water, carbon dioxide, ammonia, and propane as having a lower atmospheric damInput 78 at www.esmagazine.com/instantproductinfo Stops Airborne Debris Before It Can Become a Problem! Mount over Intake Openings (Stops debris at entry point) Low Static Pressure Impact (>1/10th w.g. drop @ 600 fpm) Clean with Broom, Brush, Shop Vac. or Garden Hose Doesn’t Require Removal for Cleaning Reduces / Eliminates Cleaning Chemicals (Eco-friendly) Saves Energy (Equipment operates clean all season long) Reduces Maintenance Time & Cost (up to 75%) Helps Attain LEED Credit Points (in multiple categories) Resists Mold, Mildew, UV and Flames (self-extinguishing) 15+ year service life For More Information Contact: Air Solution & Newway Company Tel 513-860-9784 or 248-676-9418 www.airsolutioncompany.com Input 193 at www.esmagazine.com/instantproductinfo w w w. esmag a zin e. c o m 45 http://www.airsolutioncompany.com http://www.airsolutioncompany.com http://www.esmagazine.com/instantproductinfo http://www.heatexamerica.com http://www.heatexamerica.com http://www.esmagazine.com/instantproductinfo http://www.esmagazine.com

Table of Contents Feed for the Digital Edition of Engineered Systems - March 2009

Engineered Systems - March 2009 Contents Editor’s Note Back2Basics Case In Point Commissioning Building Automation HVACR Designer Tips Application Checklist Teaching An Old School New Tricks Basics For Absorption Chillers A New Haven For Sustainable Schools Glossary Classifieds Advertiser Index Tomorrow’s Environment

Engineered Systems - March 2009

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