Engineered Systems - April 2008 - (Page 12)

Take the HVAC CHALLENGE ™ BY STEVEN G. LIESCHEIDT, P.E., CSI-CCS, CCPR ST STEVEN TE LIESCHEIDT, P.E., CSI-CCS, CCPR HEIDT, EIDT, CSI-CCS, C R Cooling Towers water water circulation rate rate. e 2. 2. This type of evaporative cooling device pe evap ap apo ap rect ct involves indirect co indirect contact between heated mo os o fluid and atmospher and essentially comatmosphere ea eat exchanger and cooling tower at bines a hea ex heat exchan into one rela t er y compact device. into one re atively c relatively co 3. Special-purpose t w Special- urpose to al-purpose towers containing a conl ventional mechanical-draft unit in combinatio io o mecha ventional mechanica tion with an air coo e heat exchanger. o air cool tion with cooled 5. This rate 5. This rate at design conditions is approxiThi design design mately 1% o t t mately 1% of the w the water flow rate for each 12.5°F of water temperature range. 2. 2F ater m 12.5°F of water temp 8. Chimney towers th Chimney mn mne mne rs th s that have air induced tower to ow through the tow by the air density differentials that exist between the lighter, heat-humidified chimney air and the outside atmosphere. 10. An economizer that is known as free cooling. 11. Heated water discharged from a cooling tower. To brush up on the facts behind this month’s clues, refer to Chapter 36 (“Cooling Towers”) in the 2004 ASHRAE Handbook – Systems and Equipment. Liescheidt is a sales engineer with Langendorf Supply Co., Inc. in St. Louis, MO. E-mail him at stevel@lsco-inc.com. Can't wait until next issue? Now, check out the answers for this month's "HVAC Challenge" on page 73 or check out answers from past puzzles on ACROSS 1. This type of evaporative cooling device, also known as an open cooling tower, deposits water directly to the cooling atmosphere and transfers the source heat load directly to the air. 4. Of the direct-contact devices, this is the most rudimentary type of tower that exposes water to the air without any heat transfer media or fill. 6. This type of spray tower uses high-pressure sprays to induce large air quantities and improve air/water contact. 7. The difference between the leaving water temperature and entering air wetbulb temperature of a cooling tower. 9. This type of spray tower has air velocities that are relatively low and are susceptible to adverse wind effects, and it is normally used to satisfy a low-cost requirement when operating temperatures are not critical to the system. 12. This type of cooling tower film maximizes contact area and time by forcing the water to cascade through successive elevations of splash bars arranged in staggered rows. 13. This may be predicted by projecting a straight line on a psychrometric chart from the tower entering air conditions to a point representing the discharge conditions. 14. This organization publishes Guideline 12, “Minimizing the Risk of Legionellosis Associated with Building Water Systems.” 15. The heat transfer media in a cooling tower that is installed below the water distribution system in the path of the air. 16. The organization that publishes Standard ATC-1055, “Acceptance Test Code for Closed Circuit Cooling Towers.” 17. This type of cooling type fill achieves the same effect by causing the water to flow in a thin layer over closely spaced sheets. www.esmagazine.com. Solution to March’s HVAC Challenge™ DOWN 1. The rate of this loss from a tower is a function of tower configuration, eliminator design, airflow rate through the tower, and water loading; in general, an efficient eliminator design reduces this loss to between 0.001% and 0.005% of the 12 En gi neer ed S y stem s April 2008 http://www.esmagazine.com

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Engineered Systems - April 2008 Contents Editor’s Note Back2Basics HVAC Challenge Case In Point Commissioning Building Automation Energy Wiz HVACR Designer Tips This Time, Water Cooled Was All Wet Cleanroom Design In 10 Easy Steps It's Not The Heat, It's The Humidity Issues & Events Computers and Software Products Glossary Classifieds Advertiser Index Tomorrow’s Engineer

Engineered Systems - April 2008

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