Plant Services - November 2007 - (Page 55)

EFFICIENCY Compressors ure 2, the air compressor is close to the loading dock. All that was needed to recover compressor heat for the dock was a short duct run vented into the dock area. Potential heat recovery rates for space heating can be high. e U.S. Department of Energy’s Compressed Air Challenge Source Book (www1.eere.energy.gov/industry/best practices/compressed_air.html) indicates that heat recovery eﬃciencies of 80% to 90% are common. But remember, you can only recover as much heat as you need. Capturing anything more raises the space temperature above the set point and, unless that’s tolerable, you’ll need to put a thermostatic control on your heat recovery system to duct the excess heat outside. For a lot of smaller- to mediumsized plants, it’s somewhat redundant to talk about compressor heat recovery for space heating because the compressor is inside the plant anyway and is already providing space heating. What ducting can do is move that heat from a place where it might not be wanted to somewhere that it is. On the other hand, ducting the compressor’s waste heat outside has a kind of an anti-heat-recovery beneﬁt. Many plants are air-conditioned for quality control reasons, so ducting compressor waste heat outside can save money on air-conditioning. Assuming 50,000 Btu/hr per 100 cfm, the savings would be about 4 tons of cooling, or roughly 6 kW. Multiply that by the number of your cooling operating hours and the unit price of your kWh to get a rough estimate of cooling cost savings. Shaft alignment in a Flash® Do the math Estimating the savings from heat recovered for use in industrial processes or water heating requires an analysis that considers the temperatures and ﬂow rates involved, as well as the heat exchanger eﬀectiveness. If you assume a heat exchanger eﬀectiveness of 70%, you can estimate the amount of heat you can recover once you’ve calculated the minimum product of speciﬁc heat and mass ﬂow rate. As an example, consider recovering heat from 100 cfm of compressed air at 250°F, for use in a process that requires heating 10 gpm of water entering at 70°F. e mass ﬂow rate of air is about 455 lbs per hr, and for New! Measure and correct for dynamic growth in a Flash. Now, when you add the patented “OL2R” (offline-to-running) hardware+software expansion kit to the revolutionary XA alignment system, you can measure the dynamic movement of critical machines as they reach operating conditions from a cold start. The resulting data is stored in the XA and is readily accessible to automatically adjust future alignments. Onscreen animated graphics make accurate alignments of critical machines fast and easy. Seasonal order Figure 1. Ducting routs heat into the plant in the winter, out the roof in the summer. www.vibralign.com 800-379-2250 Flash is a registered trademark of Adobe Systems Incorporated. N .PLANTSERVICES. 55 http://www1.eere.energy.gov/industry/bestpractices/compressed_air.html http://www1.eere.energy.gov/industry/bestpractices/compressed_air.html http://www.vibralign.com http://www.PLANTSERVICES.com

Table of Contents Feed for the Digital Edition of Plant Services - November 2007

Plant Services - November 2007 Contents New Tools Letters Let Us Know Where to Put the Gas Up and Running How are you Fighting Crisis? What Works Why is the Best Practice Transfer so Hard? Who are you Going to Call? Chained to Power Mobile Mindset Making Money in the Lube Lab Grabbing a Moving Target Bagging the BTUs Keeping Mellow Preserving Health and Safety The Power of Reliability Excellence

Plant Services - November 2007

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