Paper 4
Effects of Nozzle Geometry on Air Flow Jet and Temperature Distribution in
an Enclosed Space
M.I.
Khan
Hulley and
Kirkwood
Consulting Engineers, Solihull,
Birmingham
,
UK
Abstract
The aim of the work was to
investigate the effect of upstream geometry of the nozzle on the
turbulence mixing and temperature distribution in still air large enclosed
spaces. Prototype experiments
were carried out with the JETs (Jet Environmental Techniques) existing
nozzle geometry in a test room. These were used to validate, under
steady state conditions, the application of an RNG kappa-epsilon
turbulence model. In the next
stage a range of nozzle profiles of similar inlet and contraction
diameters were tested under identical conditions similar to the prototype
test room. Comparisons of the
axial mean streamwise velocity decay, mass entrainment, turbulence
characteristics and the temperature distribution in the enclosed space
were reported for each of the nozzle geometries to evaluate their
performance in the space. From
the analysis of data, it was found that enhanced mixing between the jet
flows and surrounding fluid was noticed for the nozzles which generated
relatively higher turbulence kinetic energy in the near field transition
region. Examination of the
temperature profiles in the numerical space revealed that nozzles
generating high turbulence kinetic promoted better mixing of the
temperature in the near flow field and the jet fluid.
Key words: Ventilation,
HVAC, nozzle, thermal comfort, CFD, turbulence.
References
Chen
Q: (1995). “Comparision of different
models for indoor air flow computations”, Numerical Heat
Trans, B. Fundamental, 28,
(3), pp353-369.
Gan G:
(1998). “Prediction of turbulent buoyant flow using an RNG
model”, Numerical Heat
Transfer, Part A, 33, pp169-189.
Holmes PJ,
Berkooz G and Lumley JL: (1996). “Turbulence, coherent structures,
dynamical systems and symmetry”, Cambridge University Press,
Cambridge
.
Hunt JCR,
Sadham
ND
, Vassilicos JC, Launder BF, Monkiewitz PA and Hewitt GE: (2001).
“Developments in turbulence research: a review
based on the 1999 program of the Issac Newton Institute,
Cambridge
”, Journal of Fluid Mechanics, 436, pp353.
Jiang X and
Luo KH: (2003). “Dynamics and structures of transitional buoyant jet
diffusion flames with side-wall effects, Combustion and Flame, 133,
pp29-45.
Jimenez
J and Pinelli A: (1997). “Wall turbulence: how it works and how
to damp it”, AIAA paper
97, pp2122-2154.
Khan MI, Simons RR and Grass AJ:
(2005a). “Effect on turbulence production due to sudden change in flow
regimes, Journal of Hydraulic Research, 43, (5), pp1-7.
Khan MI, Simons RR and Grass AJ:
(2005b). “Upstream turbulence effect on pollution dispersion”, Journal
of Environmental Fluid Mechanics, 5, (5), pp393-413.
Khan MI, Simons RR and Grass AJ:
(2006a). “Influence of cavity flow regimes on turbulence diffusion
coefficient”, Journal of Visualisation, 9, (1), pp57-68.
Khan
MI: (2006b). “A performance evaluation of the HVAC-based nozzles,” Proc.
The 3rd Asian Conference on Refrigeration and Air-conditioning,
Seoul
National
University
,
Gyeongju
,
Korea
.
Khan
MI, Barigou M and Gilbert T: (2006c), “Nozzle side wall geometry effect
on the near flow field mixing,” Proc. International
Heat Transfer Conference-13,
Australia
.
Liu T and
Sullivan JP: (1996), “Heat transfer and flow structures in an excited
circular impinging jet, International Journal of Heat and Mass Transfer,
39, (17), pp3695-3706.
Panchapakesan
NR and Lumley JL: (1993). “Turbulence measurements in axisymmetric jets
of air and helium. Part 1: air jets”, Journal of Fluid Mechanics,
246, pp197-223.
Robinson
SK, Kline SJ and Spalart PR: (1989). “A review of quasi-coherent
structures in a numerically simulated turbulent boundary layer,” NASA
Technical Memorandum 102191.
Sbrizzai F, Verzicco R, Pidria MF and Soldati A: (2004). “Mechanisms
for selective radial dispersion of micro particles in the transitional
region of a confined turbulent round jet”, International Journal of
Multiphase Flow, 30, pp1389-1417.
Schluter J and Schonfeld T: (2000).
“LES of jets in cross flow and its application to a gas turbine burner, Flow,
Turbulence Combustion, 65, pp177-203.
Shy SS:
(1995). “Mixing dynamics of jet interaction with sharp density
interface”, Experimental Thermal and Fluid Science, 10,
pp355-369.
U.S.
Patent 4295788, (1981). “Turbine wheel and
Nozzle arrangement”.
Wang
SK
: (2001). “Handbook of Air Conditioning and Refrigeration”, 2nd
edition, Mc-Graw Hill, pp1232.
Wegner B,
Huai Y and Sadiki A: ((2004). “Comparative study of turbulent mixing in
jet in cross-flow configurations using LES, International Journal of
Heat and Fluid Flow, 25, pp767-775.
White FM:
(1986). “Fluid Mechanics,” Second edition, Mc Graw Hill, New York.
Yakhot V
and Orszag SA: (1986). “Renormalisation group analysis of turbulence, I.
Basic theory”, Journal of Scientific Computing, 1, (1),
ppp3-51. |
Contents
Paper 1
Indoor
Air Quality in Fifty Residences in
Athens
: Santamouris, M., Argiroudis, K., Georgiou, M., Livada,
I.
, Doukas, P., Assimakopoulos, M.N., Sfakianaki, A., Pavlou,
K., Geros V. and Papaglastra, M.
Paper
2
Variable Air Volume-Flow Systems - A Possible Way
to Reduce Energy Use in the Swedish Dairy Industry: Rohdin, P. and
Moshfegh, B.
Paper
3
Experimental
Evaluation of Combined DCV and Economizer Cycle Using a FLC Variable Air
Volume (VAV) System: Karunakaran, R., Parameshwaran, R., Iniyan, S. and
Anand A. Samuel
Paper
4
Effects
of Nozzle Geometry on the Air Flow Jet and Temperature Distribution in an
Enclosed Space: Khan, M.I.
Paper
5
Automatic
Ventilation Control of Trickle Ventilators: Ridley,
I.
, Davies, M., Booth, W., Judd, C., Oreszczyn, T. and Mumovic, D.
Paper
6
Minimum Outdoor Air Supply for Radon in High Rise
Residential Buildings - Natural Ventilation v Air-Conditioning Unit: Lam,
K.S., Chan, E.H.W., Chan, D.W.T., Fung, W.Y., Law, K.C. and Tai, C.T.
Paper
7
Measurement and Prediction of Aerodynamic
Stability of an Axial-Flow Ventilation Fan near the Stall Condition: Cao,
R. and Hu, J.
Paper
8
Natural
and Mixed Ventilation Design via CFD and Architectural Modelling:
Todorovic, M., Ecim, O., Marjanovic, A. and Randjelovic, I.
|
