ASHRAE Journal - January 2013 - 70

iaq applications
Energy-efficient air-conditioning and air-distribution systems include: desiccant dehumidification system; dedicated outdoor air system (DOAS); decoupled ventilation/recirculation systems; personalized ventilation (PV) system; displacement ventilation (DV) system; and underfloor air-distribution (UFAD) system. Desiccant systems offer good dehumidifying performance, but depend largely on the availability of waste heat (such as condenser heat) or renewable energy (such as solar heat) for recuperating the desiccant and to make the entire proposition a cost effective one.6 Desiccant system has also been seen as a viable technology when combined with chilled ceilings, although the condensation risk in hot and humid climates is cautioned.7 The underlying principle of DOAS or decoupling ventilation requirements from cooling is the distinct flexibility offered in achieving zone-level control of outdoor and recirculated air. By conditioning these two airstreams separately, one having a predominantly high latent cooling demand while the other has a predominantly high sensible cooling demand, it is possible to achieve good humidity control without consuming too much energy.8 The thermal comfort, IAQ and energy benefits of PV and UFAD systems have been alluded to earlier. Energy recovery features that help achieve better humidity control. In view of the high energy penalty associated with cooling and dehumidification in hot and humid climates, any means of recovering energy is always attractive. These would include runaround coil and heat pipe systems.9 Another interesting strategy that can potentially contribute to significant energy benefit is the use of condensate for precooling the hot humid outdoor air as well as in replenishing the cooling tower water.10 Comfort air-conditioning in hot and humid climates is usually associated with cold indoor temperatures, relatively high indoor humidity levels, high recirculation rates and often inadequate ventilation. By all possible measures, the indoor humidity level is the key parameter that could potentially lead to adverse health effects due to the possibility of mold growth and poor IAQ. Sustainable designs in such climates call for a different paradigm that will likely include warmer indoor temperatures, lower indoor humidity levels, increased exposure level or breathing zone ventilation. Innovative design strategies and technological developments are imperative to the creation of energy-efficient healthy buildings in these climates.

References
1. Sekhar, S.C., K.W. Tham, K.W. Cheong. 2003. “Indoor air quality and energy performance of air-conditioned office buildings in Singapore.” Indoor Air 13(4):315–331. 2. Sekhar, S.C., A.H. Lim. 2003. “Indoor air quality and energy issues of refrigerant modulating air-conditioning systems in the tropics.” Building and Environment 38/6: 815-825. 3. Sekhar, S.C., L.T. Tan. 2009. “Optimization of cooling coil performance during operation stages for improved humidity control.” Energy and Buildings 41(2):229–233. 4. Melikov, A.K. 2004. “Personalized ventilation.” Indoor Air 14(Suppl 7): 157–167. 5. Ruixin, L. S.C. Sekhar, A. Melikov. 2011. “Thermal comfort and indoor air quality in rooms with integrated personalized ventilation and under-floor air distribution systems.” HVAC&R Research 17(5):829–846. 6. Lowenstein, A. 2008. “Review of liquid desiccant technology for HVAC applications.” HVAC&R Research 14(6). 7. Niu, J.L., L.Z. Zhang, H.G. Zuo. 2002. “Energy savings potential of chilled-ceiling combined with desiccant cooling in hot and humid climates.” Energy and Buildings 34(5):487–95. 8. Mumma, S.A., K.M. Shank. 2001. “Achieving dry outdoor air in an energy efficient manner.” ASHRAE Transactions 107 (1). 9. Licina, D., S.C. Sekhar. 2012. “Energy and water conservation from air handling unit condensate in hot and humid climates.” Energy and Buildings 45:257–263. 10. Vasiliev, L.L. 2005. “Heat pipes in modern heat exchangers (Review).” Applied Thermal Engineering 25:1–19. Chandra Sekhar, Ph.D., is an associate professor at the National University of Singapore.
January 2013

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ASHRAE Journal - January 2013

Table of Contents for the Digital Edition of ASHRAE Journal - January 2013

ASHRAE Journal - January 2013
Contents
Commentary
Industry News
Letters
Meetings and Shows
Feature Articles
Long-Term Commercial GSHP Performance: Part 6: Maintenance and Controls
Thermally Active Floors, Part 1
Technology Award Case Studies:
Aquathermal Systems
Standing Columns
Data Centers
People
Emerging Technologies
IAQ Applications
Engineer's Notebook
Washington Report
Refrigeration Applications
Classified Advertising
Advertisers Index
ASHRAE Journal - January 2013 - ASHRAE Journal - January 2013
ASHRAE Journal - January 2013 - Cover2
ASHRAE Journal - January 2013 - 1
ASHRAE Journal - January 2013 - 2
ASHRAE Journal - January 2013 - Contents
ASHRAE Journal - January 2013 - Commentary
ASHRAE Journal - January 2013 - 5
ASHRAE Journal - January 2013 - Industry News
ASHRAE Journal - January 2013 - 7
ASHRAE Journal - January 2013 - 8
ASHRAE Journal - January 2013 - 9
ASHRAE Journal - January 2013 - 10
ASHRAE Journal - January 2013 - 11
ASHRAE Journal - January 2013 - 12
ASHRAE Journal - January 2013 - 13
ASHRAE Journal - January 2013 - 14
ASHRAE Journal - January 2013 - 15
ASHRAE Journal - January 2013 - Letters
ASHRAE Journal - January 2013 - 17
ASHRAE Journal - January 2013 - Meetings and Shows
ASHRAE Journal - January 2013 - 19
ASHRAE Journal - January 2013 - 20
ASHRAE Journal - January 2013 - 21
ASHRAE Journal - January 2013 - 22
ASHRAE Journal - January 2013 - 23
ASHRAE Journal - January 2013 - Long-Term Commercial GSHP Performance: Part 6: Maintenance and Controls
ASHRAE Journal - January 2013 - 25
ASHRAE Journal - January 2013 - 26
ASHRAE Journal - January 2013 - 27
ASHRAE Journal - January 2013 - 28
ASHRAE Journal - January 2013 - 29
ASHRAE Journal - January 2013 - 30
ASHRAE Journal - January 2013 - 31
ASHRAE Journal - January 2013 - Thermally Active Floors, Part 1
ASHRAE Journal - January 2013 - 33
ASHRAE Journal - January 2013 - 34
ASHRAE Journal - January 2013 - 35
ASHRAE Journal - January 2013 - 36
ASHRAE Journal - January 2013 - 37
ASHRAE Journal - January 2013 - 38
ASHRAE Journal - January 2013 - 39
ASHRAE Journal - January 2013 - 40
ASHRAE Journal - January 2013 - 41
ASHRAE Journal - January 2013 - 42
ASHRAE Journal - January 2013 - 43
ASHRAE Journal - January 2013 - 44
ASHRAE Journal - January 2013 - 45
ASHRAE Journal - January 2013 - 46
ASHRAE Journal - January 2013 - 47
ASHRAE Journal - January 2013 - Aquathermal Systems
ASHRAE Journal - January 2013 - 49
ASHRAE Journal - January 2013 - 50
ASHRAE Journal - January 2013 - 51
ASHRAE Journal - January 2013 - 52
ASHRAE Journal - January 2013 - 53
ASHRAE Journal - January 2013 - 54
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ASHRAE Journal - January 2013 - 56
ASHRAE Journal - January 2013 - 57
ASHRAE Journal - January 2013 - 58
ASHRAE Journal - January 2013 - 59
ASHRAE Journal - January 2013 - 60
ASHRAE Journal - January 2013 - Data Centers
ASHRAE Journal - January 2013 - 62
ASHRAE Journal - January 2013 - 63
ASHRAE Journal - January 2013 - People
ASHRAE Journal - January 2013 - Emerging Technologies
ASHRAE Journal - January 2013 - 66
ASHRAE Journal - January 2013 - 67
ASHRAE Journal - January 2013 - IAQ Applications
ASHRAE Journal - January 2013 - 69
ASHRAE Journal - January 2013 - 70
ASHRAE Journal - January 2013 - 71
ASHRAE Journal - January 2013 - Engineer's Notebook
ASHRAE Journal - January 2013 - 73
ASHRAE Journal - January 2013 - 74
ASHRAE Journal - January 2013 - 75
ASHRAE Journal - January 2013 - Washington Report
ASHRAE Journal - January 2013 - Refrigeration Applications
ASHRAE Journal - January 2013 - Classified Advertising
ASHRAE Journal - January 2013 - Advertisers Index
ASHRAE Journal - January 2013 - 80
ASHRAE Journal - January 2013 - Cover3
ASHRAE Journal - January 2013 - Cover4
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