Energy efficiency in HVAC systems with dry-cooler free-cooling applications (Kuru Soğutuculu Doğal Soğutma Uygulamaları ile İklimlendirme Sistemlerinde Enerji Verimliliği)
Original title Kuru Soğutuculu Doğal Soğutma Uygulamaları ile İklimlendirme Sistemlerinde Enerji Verimliliği (Energy efficiency in HVAC systems with dry-cooler free-cooling applications)
TMMOB Makina Mühendisleri Odası (MMO) · Hasan Acül
Hasan Acül's TESKON 2009 congress paper on water-side free cooling with dry coolers and chillers with integrated free-cooling coils, targeting 24/7 loads such as server rooms and data centres.
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Overview
This paper was presented at the IX National Installation Engineering Congress (TESKON 2009, Izmir) and appears on page 83 of the proceedings published by the Chamber of Mechanical Engineers (MMO); the author is Hasan Acül. It explains water-side free cooling with dry coolers and chillers fitted with integrated free-cooling coils, and explicitly targets 24/7 loads such as server rooms and internet/telecom data centres.
The paper defines three operating regimes by the difference between ambient and chilled-water temperatures: full mechanical, partial (load-sharing) and full free cooling. Partial free cooling can begin once ambient air is about 1.5-2.0 C below the required chilled-water temperature; full free cooling needs ambient at least 5 C below it. In the worked example for 10/15 C water, winter at 5 C ambient is full free cooling (only fan power), spring at 13 C is partial via a 3-way valve, and summer at 35 C has the coil bypassed.
Its practical value is the annual temperature-bin hours (Nbin, h/yr) for Turkish cities, given in six daily time periods and for all provinces in Tables 2 and 3, which let designers estimate free-cooling potential. Integrated free-cooling chillers are cited as letting the UK cover about 62% of annual cooling demand by free cooling, leaving 38% mechanical. These data make it possible to estimate, from the local climate, how many hours a year an economiser can run at a site in Turkey.
Glycol protection is also covered: about 20% ethylene glycol by volume protects to about -8 C and about 30% to about -16 C; glycol lowers coil capacity and usually requires an intermediate heat exchanger to keep glycol out of terminal units. Direct water-spray wet/dry coolers switch on only in the hottest hours under thermostat control, and their effectiveness depends on bringing air close to 100% RH. The paper dates from 2009 and also covers fan speed control.
Key points
- Partial (load-sharing) free cooling can begin once ambient is about 1.5-2.0 C below the required chilled-water temperature; full free cooling needs at least 5 C below it.
- 10/15 C water example: winter at 5 C ambient is full free cooling (only fan power), spring at 13 C partial via 3-way valve, summer at 35 C coil bypassed.
- Annual bin-hour tables (Nbin, h/yr) for Turkish cities, in six daily time periods and for all provinces (Tables 2 and 3).
- About 20% ethylene glycol by volume protects to about -8 C, about 30% to about -16 C; glycol lowers coil capacity and usually needs an intermediate heat exchanger.
- Integrated free-cooling chillers are cited as letting the UK cover about 62% of annual cooling by free cooling, leaving 38% mechanical.
- Direct water-spray wet/dry coolers switch on only in the hottest hours under thermostat control; effectiveness depends on bringing air close to 100% RH.
- Targets 24/7 loads such as server rooms and data centres.
Using it in design
- Use the paper's mode thresholds (approach of about 2 C for partial and about 5 C for full free cooling) as defaults in a free-cooling-hours estimator, fed by city bin data for Turkish sites.
- Warn when glycol is specified without an intermediate heat exchanger or capacity derating.
- Expose glycol percentage versus freeze-protection temperature in the chiller/dry-cooler catalogue.
- Show in scenarios that raising chilled-water temperature increases free-cooling hours.
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Who should read it
HVAC and data center cooling designers sizing economiser operation in the Turkish climate.
Related standards
- ASHRAE 90.4
Publication details
- Authors
- Hasan Acül
- Publisher
- TMMOB Makina Mühendisleri Odası (MMO)
- Year
- 2009
- Document number
- TESKON 2009 Bildiriler Kitabı, s. 83
- Event
- IX. Ulusal Tesisat Mühendisliği Kongresi (TESKON 2009), İzmir
- Document language
- English
- Source type
- Industry body
- Access
- Free to read
- Licence
- Copyright retained; citation only — the publisher’s terms apply to the original document
Citation
Hasan Acül (2009). Kuru Soğutuculu Doğal Soğutma Uygulamaları ile İklimlendirme Sistemlerinde Enerji Verimliliği (Energy efficiency in HVAC systems with dry-cooler free-cooling applications). TMMOB Makina Mühendisleri Odası (MMO). TESKON 2009 Bildiriler Kitabı, s. 83. IX. Ulusal Tesisat Mühendisliği Kongresi (TESKON 2009), İzmir. http://www.mmoteskon.org/wp-content/uploads/teskonkitaplar/teskon2009/teskon2009.pdf
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