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Daria DenisikhinaABOK memberPhD, LEED AP BD+C, Associate Professor of Saint Petersburg State
University of Architecture and Civil Engineering, St.-Petersburg, RussiaDeputy Director, MM-Technologies Ltd, | Mikhail SamoletovABOK memberExecutive DirectorMM-Technologies Ltd, St.-Petersburg, Russiasamoletov@mm-technologies.ru | Marianna BrodachVice-President ABOKProfessor of Moscow Architectural Institute (State Academy), Moscow,
Russia |
Heating,
ventilating, and air conditioning (HVAC) are among the most energy consumption
systems in civil engineering.
Due to the
increased need to control the consumption of energy resources reduce negative
impacts on the environment, at present, particular attention has been paid to
designing "green buildings". HVAC systems are extremely necessary,
not only to reduce electricity consumption, but also to make sure that the
designed systems, in practice, are able to provide a comfortable environment
for human and/or technological requirements for the project, otherwise, we
cannot speak about the efficient use of energy resources. Thus, if we develop
energy efficient buildings, it is necessary first to analyse the adequacy and quality
of engineering solutions which are incorporated in the design.
Modern
sports facilities using artificial ice rinks are the structures with very
sophisticated technical and high-power consuming engineering solutions.
Designation of refrigeration, ventilation and air conditioning systems consist
of maintaining the required temperature level of ice rink as well as air
temperature and humidity within the space of ice arena bowl. One of the basic
designing problems of the ice arena air distribution and conditioning system is
the need to maintain different parameters of air in the zone of ice rink
(defined by ice surface requirements) and parameters of air in spectators’
area.
Tribunes full of spectators generate free-convective warm air flows which could be strong enough to determine air circulation pattern throughout the entire arena bowl space. This creates a hazard of warm and moist air transition towards ice rink space which is inadmissible (ice melting may cause ice surface warping and fog generation above the rink surface).
The design
of ice arena air distribution system should take into account interaction of
air flows generated by supply air devices and convective air flows generated by
spectators. Taking into consideration a very complex character of air flow
generated in arena space, to select zones of influence and behaviour of the
above-mentioned flows is becoming rather difficult. Besides, the presence of
artificial ice lead to necessity take into account the radial component on a
considerable part of surfaces participating in heat exchange process (ice,
roofing, walls surfaces).
In such case, the designer may encounter deficit of information and techniques enabling him to find proper technical solutions while simplified engineering techniques are no longer yielding adequate values. As a result, it appears that requirements to ice arena air parameters are generally considered in design calculations but not in actual conditions of facilities operation.
The
foregoing features generate a need to make use of computational fluid dynamics
(CFD) methods based on numerical solution of differential conservation
equations, namely, three-dimensional Navier-Stokes equations.
At the same
time, numerical simulation of air distribution in indoor ice rinks is an
uncommon task demanding in-depth analysis of mathematic model used.
Setting the mathematic model demands consideration of a number of specific features, like assignment of boundary conditions characterizing heat gains by arena bowl and necessity to consider radiative heat exchange.
Below there
is a simulation of air flow behaviour formed in the volume of Sochi “Iceberg
Arena” (erected for 2014 Olympic Games) by the designed air distribution
systems.
The CFD
software STAR-CCM+ based on numerical solution of tri-dimensional differential
conservation equations has been selected as a research tool.
Radiative
component of heat exchange in roofed buildings with artificial ice is a
considerable factor. This is due to intermitting radiation in “ice-roof-walls”
system. It is necessary to bear in mind that, not only interior surfaces of
arena structures may be the source of radiation, but spectators as well. The
latter factor should be taken into account in mathematic model.
Correlation
betweenspectators’ sensible heat input radiant and convective components within
ambient temperature range from 10°С to 26°С is approximately 50% by
50%. Assuming that sensible heat is transferred from spectators to the premise
only with convective constituent is leading to overestimation of velocities in
free-convective flow above spectators and, as a result, to improper air
circulation in the entire volume of arena.
To
illuminate the ice rinks the ice arenas normally employ illumination devices
providing angular concentration of light by means of lamps light redistribution
inside small solid angles achieved by the use of illumination fixtures
reflectors and lenses. Different types of illumination devices are used: based
on incandescent lamps (halogen), gas-discharge lamps (metal-halogen lamps,
sodium vapour lamp), light diode lamps.
Radiation
of illumination fixtures, unlike human’s radiation, is taking place within
visible (l=380 – 780 nm) and
short-wave constituent of infrared (l = 0.74 – 2.5 µm)
radiation range and not within long-wave infrared range (l = 50 – 2000 µm).
In the mathematical
model, it is required to make separate account for narrow-directional
high-frequency radiation of lighting fixture (directed to ice surface) and
omnidirectional low-frequency radiation emitted by lighting fixtures heated
surfaces (including fixtures casings).
Light
output value, specified in product documentation, does not contain data
regarding amount of power falling on illuminated surface outside the visible
range. However, considerable part of illumination fixture radiation power
pertains to high-frequency infrared radiation.
While
numerical simulation of flow in ice arena bowls it is required to exactly know
total amount of energy falling onto illuminated surface.
Illumination
fixture surface will emit (by convection and radiation of infrared range
low-frequency part) heat. The higher the air velocity is in the zone of
illumination fixture installed in the ice rink, the more heat will be withdrawn
by convection towards the upper area of premise volume.
“Iceberg”
ice arena capacity is 12.000 spectators.
·
In
order to maintain design requirements regarding thermal and humidity air
parameters in “Iceberg Arena” air supply is foreseen:
·
via
circumferentially located jet nozzle diffusers located 22 meters above the
ice rink;
·
via
swirl diffusers circumferentially located by arena perimeter at 27.8 meters
height (first circle);
·
via
supply grills located by arena perimeter at 12.2 meters height (second
circle);
·
via
grills made in building structures and located under spectators’ seats located
by arena perimeter (air supply towards under-tribune space) at heights 0.65 – 3.80 m
(third circle);
Air is
extracted via grilles circumferentially located 32 m above the ice rink
with flow rate Ltotal = 48 000 m³/h and via
grilles located by arena perimeter above spectator seat rows at height
25.4 m with Ltotal = 450 000 m³/h.
Figure 1.
“Iceberg Arena”. Sochi. Russia.
Location of
air distribution devices is shown in Figure 2.
Figure 2.
Equipment location.
Parameters
of ice arena supply air are listed in tablebelow.
Supply air parameters.
Description | qtotal [m³/s] | T [°С] | x [g/kg] |
Nozzles directed toward ice
rink | 42 700 | 18 | 4 |
Diffusers (first circle) | 82 200 | 16 | 4 |
Grilles (second circle) | 283 300 | 16 | 4 |
Grilles (third circle) | 19 200 | 16 | 4 |
Grilles in tribunes (third
circle) | 65 300 | 18 | 4 |
Figure 3.
“Iceberg Arena”. Sochi. Russia.
For the
simulation purpose, we built-up a finite volume computation mesh consists of 14
million cells. Specific attention was paid to mesh resolution in zone of flows
delivered via nozzles and diffusers and to computation mesh quality near ice and
roofing surfaces.
Simulation
results show that originally designed delivery of 18°С air towards ice
rink creates excessive air motion in the zone of ice surface disturbing the
“cold bedding” which should be provided above ice surface (Figure 4a) and, thus, preventing formation of design-required air parameters
above the ice surface. In flow distribution areas at 1 meter above the ice
surface it is possible to view areas with excessive (up to 21°С)
temperatures (Figure 4a).
Error in
the design solution under consideration took place due to omission of the fact
that ice arenas have considerable non-isothermally of air throughout the
premise height. Thus, air temperature near ice surface is normally within
12°С – 15°С (depending on the sport event) and it may
reach 24°С – 26°С as measured in the top part of the
premise. In view of the above, we can conclude that 18°С air delivered
via air jet nozzles can be treated as “cold” (being accelerated relatively to
isothermal flow), while approaching the ice surface it may be treated as “warm”
(it begins to come up). That complicated behaviour of inflow is not correctly
described by equipment selection program which takes into account nozzles
output temperature and air temperature in the proximity to ice surface. In such
case long-range capability of supply air is considered to be much lower than it
is in reality. The latter reason caused, as verified by numerical simulation
results, ingress of warm air (drawn-up by supply air) to ice rink zone and, as
a result, considerable increase of air temperature in the said area.
To improve
the design solution, it was proposed to increase supply air nozzles temperature
from 18°С to 23°С.
Calculations
results show that in the latter case flows delivered by the nozzles are not
reaching the ice rink surface and the “cold bedding” is no longer disturbed (Figure 4b). Temperature 1 meter above the ice surface is falling from 20°С
to 15°С (Figure 4b).
Improvement
of design decision enabled the operators to avoid (during further exploitation
of arena) ice melting, ice surface warping and fog generation above the ice
surface.
Figure 4.
Temperature and velocity field: a) Original design, b)
Improved design.
Physical
experiment was performed in “Iceberg Arena” bowl without spectators and
players, with ventilation and air conditioning systems operating and
illumination system operating. Measurements were performed for a series of
points located in different levels throughout arena height. Correlation of results
of physical and numerical experiment performed for identical boundary
conditions is shown in Figure 6.
Figure 5.
“Iceberg Arena”. Sochi. Russia. Physical experiment.
Figure 6.
Correlation of numerical simulation and physical experiment results.
As seen
from above figures, data variation in physical and numerical experiments in
temperature fields amounts to less than 5% and less than 10% in moisture
content fields. Accuracy of ventilation and air conditioning system flow rates
adjustment is normally around 10%, therefore, there is no need to obtain more
accurate calculations since accuracy of boundary conditions assignment is
approximately 10%. Therefore, accuracy of mathematic model is sufficient for
analysis of ice arenas air distribution designs.
Radiative
component of heat exchange in indoor ice rink is considerable and it should be
taken into account in the mathematic model.
Assignment
of sensible heat inputs outgoing from spectators only via convective component
may lead (due to considerable increased values of free-convective flow
velocities) to improper air circulation in the entire volume of ice arena bowl.
Heat flows
from heated surfaces of illumination fixtures should be modelled with account
to separation into radiative and convective components.
Applying of
numerical simulation methods to analyse air distribution in Sochi “Iceberg
Arena” enabled the researchers to reveal defects of original design and,
therefore, prevented the implementation in the design of an ineffective
solution.
Correlation
of results of numerical simulation (performed with no spectators inside arena)
with physical experiments results gave 4% – 7% calculation mismatch.
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Bellache, O.; Galanis, N.; Ouzzane, M.; Sunyé, R.; Giguère, D. Two-Dimensional Transient Model of Airflow and Heat Transfer in Ice Rinks (2006) ASHRAE Transactions, vol. 112 (2), pp. 706-716.
Bellache, O., Ouzzane, M., Galanis, N. Numerical prediction of ventilation patterns and thermal processes in ice rinks (2005) Building and Environment, vol. 40, pp. 417-426.
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Stobiecka, A., Lipska, B., Koper, P. Comparison of air distribution systems in ice rink arena ventilation (2013) Science - Future of Lithuania, vol. 5(4), pp. 429-434.
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