City University of Hong Kong Department Name

 

Stratum ventilation

Innovative ventilation strategies are investigated. Stratum ventilation is developed for elevated indoor temperatures recommended by governments in East Asia, which is proposed based on the following rationales:

      IAQ in the breathing zone is most important;

      Head level needs more cooling in warm conditions;

      Cooling effect includes air temperature and movement;

      New ASHRAE Standard 55-2010 allows increased air movement to cool the occupants in warm conditions;

      Air should therefore be introduced into the breathing zone/head level to form a young and moving air layer; and

      Air temperature gradient is reverse and small in the occupied zone.

Fig.1 Conceptual diagrams of stratum ventilation

Year-round energy consumption of stratum ventilation is found to be low due to the following eight factors:

1.   Stratum ventilation has been found to have neutral temperature above 27ºC. For identical relative humidity, the higher the room temperature, the higher the humidity ratio and therefore the lower the latent load;

2.   Smaller temperature difference between the indoors and the outdoors;

3.   Smaller enthalpy difference between the indoors and the outdoors;

4.    Longer free cooling period;

5. Higher ventilation effectiveness and therefore lower ventilation load;

6.   Reverse temperature gradient in the occupied zone, which avoids over-cooling the lower zone;

7.   Elevated supply air temperature allows higher evaporative temperature of the associate chiller(s); and

8.   Smaller pumps and fans because of lower cooling capacity.

Fig. 2  Thermal sensation under different air distribution methods

Fig.2 Thermal sensation under different air distribution methods

Sample database of air temperature and speed for stratum ventilation

Fig.3 Sample database of air temperature and speed for stratum ventilation

           Fig.4 Air supply layer visualized during test       Fig.5 Grid mesh of small test chamber


Fig.6 A large test chamber

      Integrative experimental and computational fluid dynamics (CFD) techniques are used in the development. With properly designed supplied air velocity and volume flow, as well as suitable locations of supply and exhaust, the proposed system has shown to maintain high thermal neutral temperature with a small and reverse temperature gradient between the head and foot levels, lower year-round energy consumption, and better indoor air quality (IAQ) in the breathing zone.

Related publications:

Keynote Speeches:

Lin Z, Chow TT, Tsang CF. Prediction of the performance of the new stratum ventilation system in a typical retail workshop using CFD. The Proceedings of the 22th Congress of International Institute of Refrigeration. Beijing, China, 20-26 August 2007, p 160 + CD-ROM.

Lin Z. Stratum ventilation and its design. 18th China HVAC&R Congress, Yantai, China, 24 每 26 October 2012.

Journal articles:

Lin Z, Chow TT, Tsang CF, 2006. Validation of CFD model for research into stratum ventilation. International Journal of Ventilation, 5(3): 345-363.

Tian L, Lin Z, Liu J, Wang Q, 2008. Numerical study of indoor air quality and thermal comfort under stratum ventilation. Progress in Computational Fluid Dynamics, 8(7-8): 541-548.

Lin Z, Chow TT, Tsang CF, Fong KF, Chan LS, 2009. Stratum ventilation - a potential solution to elevated indoor temperatures. Building and Environment, 44(11): 2256-2269.

Tian L, Lin Z, Wang Q, Liu J, 2009. Numerical investigation of indoor aerosol particle dispersion under stratum ventilation and under displacement ventilation. Indoor and Built Environment, 18(4): 360-375.

Tian L, Lin Z, Wang Q, 2010. Comparison of gaseous contaminant diffusion under stratum ventilation and under displacement ventilation. Building and Environment, 45(9):2035-2046.

Lin Z, Chow TT, Tsang CF, Fong KF, Chan LS, 2010. Stratum ventilation for a workshop under elevated indoor temperature. International Journal of Ventilation, 9(1): 47-58.

Lin Z, Tian L, Yao T, Wang Q, Chow TT, 2011. Experimental and numerical study of room airflow under stratum ventilation. Building and Environment, 46: 235-244.

Tian L, Lin Z, Liu J, Yao T, Wang Q, 2011. The Impact of Temperature on Mean Local Air Age and Thermal Comfort in a Stratum Ventilated Office. Building and Environment, 46: 501-510.

Lin Z, Lee CK, Fong KF, Chow TT, Yao T, Chan ALS, 2011. Comparison of annual energy performances with different ventilation methods for cooling. Energy and Buildings, 43: 130–136.

Fong ML, Lin Z, Fong KF, Chow TT, Yao T, 2011. Evaluation of thermal comfort conditions in a classroom with three ventilation methods. Indoor Air, 21(3), 2011, 231-239.

Tian L, Lin Z, Wang Q, 2011. Experimental investigation of thermal and ventilation performances of stratum ventilation. Building and Environment, 46: 1309-1320.

Lin Z, 2011. Effective draft temperature for evaluating the performance of stratum ventilation. Building and Environment, 46: 1843-1850.

Lin Z, Yao T, Chow TT, Fong KF, Chan LS, 2011. Performance Evaluation and Design Guidelines for Stratum Ventilation. Building and Environment, 46 (2011) 2267-2279.

Lin Z, Wang J, Yao T, Chow TT, 2012. Investigation into anti-airborne infection performance of stratum ventilation. Building and Environment, 54: 29-38.

Lin Z, Lee CK, Fong KF, Chow TT, 2012. Comparison of annual energy performances with different ventilation methods for temperature and humidity control. Energy and Buildings, 43: 3599-3608.

Lee CK, Fong SKF, Lin JZ and Chow TT. Year-round energy saving potential of stratum ventilated classrooms with temperature and humidity control. HVAC&R Research, 19(8), 2013, 986-991.

Cheng Y, Fong ML, Yao T, Lin Z, Fong SKF. Uniformity of stratum ventilated thermal environment and thermal sensation. Indoor Air, 2014, DOI: 10.1111/ina.12097.

Lin Z, Yao T. An investigation into the performance of fabric diffusers used in stratum ventilation. Building and Environment, 2014, DOI: 10.1016/j.buildenv.2014.06.016.

Conference papers:

Lin Z, Chow TT, Tsang CF. Stratum ventilation? a conceptual introduction. Proceedings of the 10th International Conference on Indoor Air Quality and Climate, Beijing, 4-9 September 2005, pp 3260-3264.

Lin JZ, Chow TT, and Tsang CF. Intelligent control of stratum ventilation. Creating a healthy indoor environment for people (Proceedings of Healthy Building 2006), Lisboa, 4-8 June 2006, vol. 4, pp 315-320.

Lin Z, Chow TT, Tsang CF. Perceived control of stratum ventilation system. Proceedings of Clima 2007 Wellbeing Indoors, Helsinki, 10-14 June, 2007, p 168 + CD ROM.

Lin Z, Chow TT, Tsang CF. Stratum ventilation for Hong Kong buildings. The Proceedings of Joint Symposium 2007 Building Services Engineering for a World Class City. Hong Kong, China, 13 November 2007, pp 103-112.

Lin Z, Chow TT, Tsang CF. Ventilation system for elevated indoor temperature. Proceedings of Henan 每 Hong Kong Joint Symposium 2008, Zhengzhou, China, 30 June - 1 July 2008, pp. 75-86. (in Chinese with English abstract)

Lin Z, Chow TT, Tsang CF. Stratum ventilation 每 solution to elevated indoor temperatures. The Proceedings of the First International Conference on Building Energy and Environment. Dalian, China, 13-16 July 2008, p 175 + CD-ROM.

Lin Z, Chow TT, Tsang CF. Stratum ventilation 每 solution to higher room temperature settings. The Proceedings of the Fifth National Symposium on Innovative Technologies in Refrigeration and Air Conditioning. Xiamen, China, 4-7 August 2008, p 60 + CD-ROM.

Lin Z, Chow TT, Tsang CF. Prediction of the performance of the new stratum ventilation system in a typical classroom. Proceedings of 11th International Conference on Air Distribution in Rooms (Roomvent2009), Busan, Korea, May 2009, pp.1719-1726.

Lin Z, Fong ML, Fong KF, Shum WS. Stratum Ventilation for a Retrofitted Classroom. Proceedings of 30th AIVC conference ※Trends in high performance buildings and the role of Ventilation§, Berlin, Germany, October 2009, CD-ROM.

Lin Z, Chow TT, Tsang CF. Stratum Ventilation for a Workshop under Elevated Indoor Temperature. Proceedings of Ventilation 2009, Zurich, Switzerland, October 2009, pp.701-704.

Lin Z, Chow TT, Tsang CF, Fong KF. A case study of energy saving potential of stratum ventilation. Proceedings of Clima 2010 每 10th REHVA World Congress ※Sustainable Energy Use in Buildings§, Antalya, Turkey, 9-12 May 2010, CD-Rom (ISBN 978-975-6907-14-6).

Lee CK, Lin Z, Fong KF. Year-round energy saving potential for a stratum ventilated subtropical office. Proceedings of 31th AIVC conference ※Low Energy and Sustainable Ventilation for Green Buildings§, Seoul, Korea, October 2010, CD-ROM.

Lee CK, Lin Z, Fong KF. Year-round energy saving potential for a stratum ventilated subtropical classroom. Proceedings of Indoor Air 2011 ※The 12th International Conference on Indoor Air Quality and Climate§, Austin, Texas, USA, June 2011, CD-ROM.

Lee CK, Lin Z, Fong KF. Year-round energy saving potential for control of temperature and humidity in a stratum ventilated subtropical office. Proceedings of Roomvent 2011 ※12th International Conference on Air Distribution in Rooms§, Trondheim, Norway, June 2011, CD-ROM.

Lee CK, Lin Z, Fong KF. Year-round energy saving potential of a stratum ventilated classroom with temperature and humidity control. Proceedings of Healthy Buildings 2012 每 10th International Conference, Brisbane, Queensland, Australia, 8 每 12 July 2012, CD-ROM.

Wang Guan, Lin Z, Wang Fenghao. Progress Made in Stratum Ventilation Research. Proceedings of 7th National Symposium on New Refrigeration and Air Conditioning Technologies 2012, Xi*an, China, 25 每 26 August 2012, CD-ROM.

Lee CK, Lin Z, Fong KF. Year-Round Energy Saving Potential of a Stratum Ventilated Retail Shop with Temperature and Humidity Control. Proceedings of Clima 2013 – "the 11th REHVA World Congress and the 8th Conference on Indoor Air Quality, Ventilation and Energy Conservation in Buildings", Prague, Czech Republic, 16-19 June 2013, CD-Rom (ISBN 978-80-260-4001-9).

Lin Z, Fong ML. Design of Thermal Comfort in a Stratum Ventilated Classroom. Proceedings of Clima 2013 – "the 11th REHVA World Congress and the 8th Conference on Indoor Air Quality, Ventilation and Energy Conservation in Buildings", Prague, Czech Republic, 16-19 June 2013, CD-Rom (ISBN 978-80-260-4001-9).

Lin Z, Fong ML, Wang J. Stratum Ventilation 求 a Solution to Elevated Room Temperatures. Proceedings of Clima 2013 – "the 11th REHVA World Congress and the 8th Conference on Indoor Air Quality, Ventilation and Energy Conservation in Buildings", Prague, Czech Republic, 16-19 June 2013, CD-Rom (ISBN 978-80-260-4001-9).

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