Paper 7
Active Chilled Beam Wall Jet
Prediction by the Free Convection Model
Guangyu
Cao1, Jarek Kurnitski1, Panu Mustakallio2
and Olli Seppänen1
1Department
of Mechanical Engineering, Helsinki University of Technology, 02150 ESPOO,
Finland
2Halton
Oy Haltonintie 1-3, 47400 Kausala, Finland
Abstract
In this study, the
measured and predicted air distribution of an active chilled beam in a
typical office room is described. A free convection model was applied for
the vertical downward air jet along the wall by superposing a free
convection velocity and an isothermal jet velocity. The velocity and
temperature of the wall jet were measured at six different heights and six
distances from the wall in the near wall zone and in the wall-floor corner
zone. The experiment implemented two airflow rates of 20 and 28 L/s
with three cooling loads of 0, 40 and 100 W/m2. The
results of the measurements show that the maximum velocities were close to
the wall surface, between 0.025 to 0.05 m from the wall. Below the
height of 1.7 m, air velocities decreased quasi-linearly when
approaching the floor level. The calculated non-isothermal wall jet
velocities superposed with the free convection velocity show that the
introduced model can be used for the prediction of the maximum velocity of
the wall jet. The model is free of a problem of the conventional
non-isothermal jet equation, which predicts velocities slightly increasing
downwards, while the measured ones significantly decreased along the wall.
Key words: chilled
beam, air distribution, airflow, free convection model.
References
Alamdari
F, Butler DJG, Grigg PF and Shaw MR: (1998) “Chilled ceilings and
displacement ventilation”, Renewable Energy, 15,
pp300-305.
Awbi HB: (1991).
“Ventilation of Buildings”. E& FN Spon, 313 pages.
Cao GY, Kurnitski J and Mustakallio P. (2007a) “Draught risk evaluation in rooms with chilled beams”, In: Proceedings
of the 10th International Conference on Air Distribution in Rooms -
Roomvent 2007, Helsinki.
Cao GY, Kurnitski J, Mustakallio P and Seppänen O: (2007b) “Performance of chilled beam air distribution close to the wall”, In:
Proceedings of the 10th International Conference on Air Distribution in
Rooms - Roomvent 2007, Helsinki.
Cao GY, Kurnitski J, Mustakallio P and Seppänen O: (2007c)
“Chilled beam’s air distribution measurements and plane wall jet
modeling”, In: Proceedings of The 5th International Symposium on
Heating, Ventilating and Air Conditioning - ISHVAC 2007 Congress,
pp288-295.
Costelloe
B and Finn D: (2003) “Indirect evaporative cooling potential in
air–water systems in temperate climates”, Energy and Buildings,
35, (6), July, pp573-591.
Fredriksson
J, Sandberg M and Moshfegh B: (2001) “Experimental investigation of the
velocity field and airflow pattern generated by cooling ceiling beams”. Building
and Environment, 36, pp891-899.
Hagström
K, Siren K and Zhivov AM: (1999) “Calculation methods for air supply
design in industrial facilities”. Helsinki University of Technology,
HAVC Laboratory, Report B60, Finland, pp50-58.
Kosonen
R and Virta M: (2007a) “Taking flexibility into account in designing beam systems”, In:
Proceedings of the 9th Federation of European Heating and
Air-Conditioning Associations World Congress- WellBeing Indoors Clima
2007, Helsinki.
Kosonen
R, Melikov A, Yordanova B and Bozkhov L:
(2007b) “Impact of heat load
distribution and strength on airflow pattern in rooms with exposed chilled
beams”,
In: Proceedings of the 10th International Conference on Air Distribution in
Rooms - Roomvent 2007, Helsinki.
Kosonen
R, Virta M and Melikov A: (2007c) “The impact of thermal loads on indoor air flow”, In:
Proceedings of the 9th Federation of European Heating and
Air-Conditioning Associations World Congress- WellBeing Indoors Clima
2007, Helsinki.
Klobut K and Palonen J: (1992) “Ilmasuihkut Kirjallisuuskatsaus”, Technology report, Helsinki.
Kurnitski J, Cao GY and Mustakallio P: (2007) “Draft assessment for ceiling vs. wall type chilled beams”, In:
Proceedings of the 10th International Conference on Air Distribution in
Rooms - Roomvent 2007, Helsinki.
Melikov
A, Yordanova B, Bozkhov L, Zboril V and Kosonen
R: (2007) “Human
response to thermal environment in rooms with chilled beams”, In:
Proceedings of the 9th Federation of European Heating and
Air-Conditioning Associations World Congress- WellBeing Indoors Clima
2007, Helsinki.
Miettinen A and Aitta T: (1992) “Virtaus
ja Lämmönsiirto”, Invent-Teknologiaohjelma, Report 8,
Helsinki, pp18-20 .
Rajaratnam
N: (1976) “Turbulent Jets”, Elsevier,
Amsterdam, The Netherlands, pp214-216.
Riffat
SB, Zhao X and Doherty PS: (2004) “Review of research into and
application of chilled ceilings and displacement ventilation systems in
Europe”, Int. J. Energy Res., 28, pp 257–286.
Yu
H, Liao CM, Liang HM and Chiang KC: (2007) “Scale model study of airflow
performance in a ceiling slot-ventilated enclosure: Non-isothermal
condition”. Building and Environment, 42, pp1142-1150.
Zboril
V, Melikov A, Yordanova B, Bozkhov L, Kosonen R: (2007)
“Airflow distribution in rooms with active chilled beams”, In:
Proceedings of the 10th International Conference on Air Distribution in
Rooms - Roomvent 2007, Helsinki.
|
