The weather is finally warm. Your plant’s HVAC system no longer needs to burn thousands of dollars each day rendering outside air suitable for the delicate constitutions of workers in the plant and offices. Now might be a perfect time to start thinking about reducing future heating bills. Unless you know something I don’t, you should expect natural gas prices to increase at a rate exceeding the recent climb in gasoline prices. Then again, maybe it would be cheaper simply to bank the fires in the boilers and furnaces and buy everyone a new down jacket, a pair of insulated boots and warm gloves. Or, take the Dickensian approach of having them each bring a bucket of coal to work each morning.
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I have no doubt that you already know about energy audits and thermography for showing where some caulking, insulation and weather-stripping might be appropriate. But, does anyone ever go back to the drawing board to see if the original heating-system design is still adequate, given the plant modifications instituted during the intervening years?
Let’s take a dive into the morass we call the Web in search of practical, zero-cost, noncommercial, registration-free Web resources that might be useful for achieving a better level of energy independence. Remember, we search the Web so you don't have to.
The big picture
“Energy Efficiency in Industrial HVAC Systems,” published by the North Carolina Division of Pollution Prevention and Environmental Assistance, is a 10-page document that can serve as a primer on the topic. Features include a list of basic HVAC-related definitions, four pages of line items that can be worked into an energy audit checklist for your HVAC system and links to building simulation software tools, some of which are free. Finally, you’ll find a worksheet for assessing the existing conditions in your facility. It all resides at www.p2pays.org/ref/26/25985.pdf.
Fixing the air
We get through life crawling around at the bottommost part of an ocean of air. It took us a while to realize that the solution to pollution isn’t dilution. We all agree that we’ve got to keep our puddle of respiratory material clean. Doing that inside your building might even improve productivity, especially among the knowledge workers hiding in the office areas. Correct me if I’m wrong, but I’d guess that solving indoor air-quality problems isn’t one of your organization’s core competencies, and that you’d probably outsource the project to someone better equipped to do the dirty work. With that in mind, I offer you “Guidelines for Selecting an Indoor Air Quality Consultant,” an article abstracted from a larger body of work published by the American Industrial Hygiene Association in Fairfax, Va. Send your desk rodent to www.cal-iaq.org/cal-iaq%20guidance.htm, where it will learn about the six steps needed to solve an IAQ problem. The article addresses determining the scope of the problem, making an inventory of the sources of airborne dusts, chemicals and allergens, examining sources of moisture intrusion or water damage and finding common HVAC problems. You also can learn the conditions that would justify calling a professional IAQ consultant, as well the categories of other professionals you might find useful in the quest for good air.
The article references another document, “Building Air Quality: A Guide for Building Owners and Facility Managers," but provides no link or information about finding it. So, we tracked down a copy for you at www.epa.gov/iaq/largebldgs/baqtoc.html. The concepts that your hired hands in Washington present here are the lessons they learned from the multiple hundreds of IAQ investigations that NIOSH has conducted in office buildings. Strictly speaking, industrial facilities aren’t included, but much of this knowledge your government is willing to impart free of charge is sufficiently general that clever engineers out there in readerland can extrapolate it into customized IAQ solutions. The entire PDF opus can be downloaded as a 2.8-MB Zip file or you can download only the sections you need. If nothing else, investigate the 19 worksheets, forms and records that allow you to better document the nasty air circulating in your buildings.
Designing an industrial HVAC system is a computationally intense activity, but you do it once — unless, of course, you start modifying, expanding or upgrading it later. That requires you either to dust off your slide rule skills or investigate the software offerings at www.geokiss.com./hsoftware.htm, brought to you by the HVAC and Energy Conservation courses at The University of Alabama. This is where you’ll find Excel spreadsheets that perform HVAC load calculations and model the famous Ductulator, psychrometric charts and the efficiency of various HVAC options. According to the site, the spreadsheets follow basic ASHRAE calculation procedures. Hey, for free, it’s worth a try.
Another software resource you should know about is found at www.connel.com/freeware/. This is where Michael J. Rocchetti, P.E., posts his CGI PERL scripts for making point estimates of psychrometric variables and flow conditions inside an air duct.
Don’t forget Jim Judge, P.E. He’s an HVAC engineer with a focus on humidity control who owns Linric Co., a consultancy in Bedford, N.H. Pointing your mouse in the general direction of www.linric.com/free4me.htm will give you access to psychrometric material, including the chart, a calculator, Excel functions and more. The fully functional software demos operate for 30 days before self-destructing in a cloud of smoke à la Mission Impossible.
The industrial arena we know and love is populated with many enormous, complex HVAC systems. These range from the finesse needed for a Class 10 clean room to the brute strength that a foundry demands. The goal, after all, is to provide an environment in which processes and personnel can function without stress and trouble. If you might have a need to reengineer an industrial HVAC system, you should read “Industrial Strength Solutions,” an article by Randy Casteel, P.E., which appeared in the September 2000 issue of Engineered Systems magazine. This publication is dedicated to the art and science of nonresidential HVAC equipment. In the article, Casteel offers advice and suggests issues you should consider at each stage of the process -- project kickoff meetings, working the load calculations, deciding how much outside air is appropriate, distribution system configuration and dealing with pressurized zones. I’d be surprised if you didn’t learn at least one thing at www.esmagazine.com/CDA/ArticleInformation/coverstory/BNPCoverStoryItem/0,2500,8712,00.html, where the story resides.
Regardless of how clever an engineer might be, HVAC designs and operations, like so many other technical disciplines, have no choice but to respond to the immutable rules of thermodynamic theory. There’s no getting around that old harpy, Mother Nature. Discussing the topic at a technical level involves knowing the precise definitions of the many terms and phrases needed to communicate and quantify the characteristics of the HVAC system in your plant. You might be interested in a bit of a refresher course about the meaning of such constructs as isothermal, isentropic, adiabatic mixing, throttling, exergy, sensible heat and latent heat. If so, pop over to visit the good folks from Taftan Data, Vancouver, B.C., who have been kind enough to offer “Applied Thermodynamics,” a page of links to definitions for these and many more concepts. Send that inquisitive mouse of yours to www.taftan.com/thermodynamics/ for the details.
Doing the math
The typical HVAC calculation is performed on a psychrometric chart. Applying the chart’s moisture and thermal data to the real-world airflow and heat load is the key to sizing humidifiers, reheat coils, air conditioners, air-handling units and the other system components. The most uncontrollable variable in the HVAC mix is the temperature and humidity that one assumes for the outside air that’s being processed. What values should one use? The atmosphere can be hot and humid, cold and dry, and anything in between. One way to estimate correctly is by plotting your climatic data on a psych chart. The eye can pick out graphic patterns in the resulting scattergram better than the brain can guess accurate values. To help you plot the thousands of points that represent a year’s worth of data, I offer you a software package called Get Psyched. Produced by kW Engineering, Oakland, Calif., it transfers climatic data from an Excel spreadsheet to the psych chart automatically. The neat feature is that it corrects for altitude to 15,000 ft. The package can be downloaded freely, but it immobilizes itself in 60 days unless you pay for it. Send your plodding mouse to www.kw-energy.com/psych.htm to get the goods. It will save you a lot of pencil lead.
Most of your HVAC costs are determined by the prevailing weather conditions in your part of the world. Lucky are those who live where the temperature hovers around 70ºF and the relative humidity is always between 60% and 70%. The rest of us, however, either consume energy to make the indoor microclimate reasonably tolerable or we suffer uncomfortably. But, there are measures a plant can take to help minimize those costs. Or, so say the architects anyway. With that perspective, please read “Climatic Design of Buildings - An Overview,” by Sam CM Hui at Hong Kong University’s Department of Architecture. Here is where you can learn the details about analyzing sunshade, wind, humidity and rain. Read the section on passive design considerations for hot regions. The material is found at www.arch.hku.hk/~cmhui/teach/65156-7.htm.
Hui references something called PSYCHWIN, a software package that eliminates having to make point estimates of psychrometric variables in favor of using graphical analysis. Unfortunately, he doesn’t link to the free download. That feature is to be found at http://arch.hku.hk/teaching/archisci/archisci.zip.
Working the chart
Finding an online psych chart is far easier than locating a cogent tutorial that explains how to use the blasted thing for HVAC calculations. Thanks to the good folks at Denco Limited, Hereford, England, a manufacturer of air conditioning equipment, you have the opportunity to learn more about the curves and the computations they drive than you ever wanted to know. When you arrive at www.denco.co.uk/index.htm, scroll to the lower right-hand corner of the page. Look for a set of PDF reference works about psychrometry, thermodynamics, ideal gas data and suggested answers to the quizzes sprinkled around the former documents. From there, it’s a case of click and learn. Too bad it won’t get you any continuing education credits.
From the archives
Knowing how to run the numbers isn’t very useful if you don’t have the numbers to run. But climatic data is available if you know where to look. One repository of such thing climatological, the World Data Center for Meteorology, Asheville, in Asheville, N.C., claims to have at least 150 years worth of weather data and keeps adding to the pile at the rate of 55 Gb per day, the equivalent of 18 million pages. Who does the proofreading, I ask you? It’s a good thing that digital memory is cheap. But I digress.
Let me direct your attention to a Web site that has monthly weather records and averages for more than 16,439 cities worldwide. Zip over to www.weatherbase.com/ and check what’s available for your location. Navigation on the site is quite intuitive.
Don’t forget the National Oceanic and Atmospheric Administration (NOAA), the official word on domestic weather. Our hired hands in Washington have built a huge Web site to disseminate their archives of weather data. You can enter the site, but beware. Amid so much interesting data, it’s easy to lose track of time. You’d best set an alarm clock before jumping in at www.noaa.gov/pastweather.html. Most of the data you’ll find there is free of charge, as long as you access it online. If you want NOAA to send a CD full of free data, you’ll pay. Also, some data sets have a price, regardless of delivery method. They warn you when you’re getting too close to the edge on this matter. Nevertheless, I have no doubt that if you poke around long enough, you’ll find some data sets that can be put to profitable use.