Prediction of yearly energy requirements of indoor ice rinks

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    Energy and Buildings 41 (2009) 500511

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    Contents lists available at ScienceDirect

    Energy and

    journal homepage: www.e ls1. Introduction

    Indoor ice rinks are large buildings without internal partitionsand with high-energy consumption. They have a complex energysystem in which a large ice sheet is cooled andmaintained at a lowtemperature by a refrigeration system, while the stands are heated(or cooled) to ensure comfortable conditions for the spectators.Also, the building is ventilated to ensure good air quality. Themovement of the ventilation air through these wide-open areasand the simultaneous operation of heating and cooling equipmentsincrease energy consumption and greenhouse gas (GHG) emis-sions.

    A study by Lavoie et al. [1] shows that the potential for energysavings in a typical ice rink in Quebec is roughly 620 MWh/yearand the potential GHG emission reduction is 146 tons-equivalentCO2/year. Since there are 435 indoor ice rinks in Quebec andseveral thousand in North America, it would be interesting toimprove their energy efciency while preserving good ice qualityand comfort for the spectators. To achieve this objective precisemethods for the calculation of the corresponding loads arenecessary.

    Three different methods are commonly used for the thermalmodeling of buildings: the nodal method, computational uiddynamics (CFD) and the zonal method. The rst one is the simplest

    building, or of large parts thereof, by a single node. Therefore thenodal method does not necessitate an important computingcapacity but, on the other hand, it does not provide a detaileddescription of the indoor conditions. The application of such amodel to ice rinks (or other large buildings without internalpartitions such as supermarkets or gymnasia) can lead to veryimprecise results because the mass uxes between different partsof the inside volume are extremely difcult to estimate.

    On the other hand, the modeling of an ice rink for CFDcalculations is very complex due rstly to their size and geometry,and secondly to the variety of the heat and mass transfermechanisms which take place therein. Thus, the model must takeinto account heat transfer through the envelope and heat gains fromthe ground, airmotionwithin the building due to forced and naturalconvection, vapourdiffusion and condensationon the ice sheet, heattransfer by radiationbetweenall internal surfaces, conduction in theice and oor as well as heat generation by the lights, the resurfacingoperations, the refrigeration system, etc. Hence, the literaturereview revealed fewCFD studies for large buildings such as ice rinks.Jones andWhittle [2] described the status and capabilities of CFD forbuilding air ow prediction while Jian and Chen [3] as well as Yanget al. [4] used a CFD code to evaluate air quality in large ventilatedenclosures. However, these studies did not calculate heating andrefrigeration loads and ignored the interaction between the indoorand outdoor environments.

    More recently Bellache et al. [5,6] have carried out numericalsimulations in 2D and steady state conditions using a CFD codewhich predicts velocity, temperature and absolute humiditydistributions in an indoor ice rink with ventilation and heating.

    * Corresponding author.

    E-mail address: nicolas.galanis@usherbrooke.ca (N. Galanis).

    Abbreviations: AIM, above ice model; BIM, below ice model; IST, ice surface

    temperature.

    0378-7788/$ see front matter 2008 Elsevier B.V. All rights reserved.Prediction of yearly energy requiremen

    Lot Seghouani, Ahmed Daoud, Nicolas Galanis *

    Departement de Genie Mecanique, Universite de Sherbrooke, Sherbrooke, Qc, Canada J1

    A R T I C L E I N F O

    Article history:

    Received 24 April 2008

    Received in revised form 20 October 2008

    Accepted 22 November 2008

    Keywords:

    Zonal method

    Ground conduction

    Radiation exchanges

    Convection

    Condensation

    Refrigeration load

    A B S T R A C T

    A model of the transient

    indoor ice rink and the bri

    coupled with a previousl

    radiation and phase cha

    humidifying (or cooling a

    resulting simulation too

    consumption by the venti

    stands and the undergro

    American cities with very

    ventilation air stream in tdoi:10.1016/j.enbuild.2008.11.014of indoor ice rinks

    R1

    t transfer between the ground under and around the foundations of an

    circulating in pipes embedded in the concrete slab under the ice has been

    eveloped model calculating heat uxes towards the ice by convection,

    s. Subroutines calculating the energy consumption for heating and

    reheating) the ventilation air have also been added to the model. The

    as been used to calculate monthly refrigeration loads and energy

    on system, the lights, the brine pump, the radiant heating system of the

    electric heating used to prevent freezing and heaving for four North

    fferent climates. Correlations expressing the energy consumption of the

    s of the sol-air temperature are formulated.

    2008 Elsevier B.V. All rights reserved.

    Buildings

    evier .com/ locate /enbui ld

  • L. Seghouani et al. / Energy and Buildings 41 (2009) 500511 501Nomenclature

    A area (m2)

    Cp specic heat (J/kg K)

    Cd discharge coefcient

    g acceleration of gravity (m/s2)

    h height (m)

    k thermal conductivity (W/(m K)The CFD code also calculates the heat uxes toward the ice due toconvection from the air, to condensation of vapour and to radiationfrom the walls and ceiling. However, these calculations did nottake into account the contributions of ice resurfacing, systempump work and ground heat to the refrigeration load.

    This 2D CFD model was later improved by Bellache et al. [7] byincluding transient phenomena, heat transfer through the groundand energy gains from lights as well as the effects of resurfacingand dissipation of pumpwork in the coolant pipes. The ground at a

    mi; j airow between zones i and j (kg/s)

    mB brine ow rate (kg/s)

    M mass (kg)

    P static pressure (Pa)

    qcd conductive ux (W/m2)

    qcv convective ux (W/m2)

    qrd radiative ux (W/m2)

    qcond condensation ux (W/m2)

    qrs heat ux due to resurfacing (W/m2)

    QCool cooling rate (W)

    QHeat heating rate (W)

    QHumid energy rate due to humidication (W)

    QRe heat energy rate due to reheating (W)

    QH electrical power in sand layer (W)

    QIce heat rate into node 1 calculated by AIM (W)

    Qnode lateral heat transfer to node n (W)

    R thermal resistance (m2 K/W)

    Snode surface for lateral heat transfer at node n (m2)

    t time (h)

    T temperature (K)

    Tb brine temperature (K)

    Tgr temperature of ground surface (K)

    Tnode temperature at node n (K)

    Tsol-air sol-air temperature (8C)

    Unode average conductance for lateral heat transfer at

    node n (W/m2 K)

    Wg moisture source term (kg/s)

    z1, z2 top and bottom depths of ground segment (m)

    Subscripts and superscriptsi cell i or surface i

    i, j between surface or cell i and j

    o outside

    p present time step

    p + 1 next time step

    Greek symbolsDt time step (s)eij constant depending on ow direction (1)r air density (kg/m3)

    v absolute humidity (kgmoisture/kgdry air)depth of 2 m was assumed to have a constant temperature whilethe horizontal plane through the centers of the brine pipes wasassumed to be an isothermal surfacewith temperature equal to theaverage of the supply and return brine temperatures.

    Ouzzane et al. [8] contributed preliminary experimentalmeasurements for a Canadian indoor ice rink which provide abetter understanding of its thermal and energy behaviour. Thesemeasured valueswere also used for the verication and calibrationof the numerical model developed by Bellache et al. [7]. The maindrawback of the CFD approach is that it requires considerablecomputer memory and CPU time for the simulations. Thus, thetransient 2D model by Bellache et al. [7] requires approximately24 h of calculations on amodern desktop computer to simulate theresponse of an ice rink over a period of 1 day.

    An alternative method to CFD, which requires less calculationtime and computer memory, was developed by Daoud et al. [911].It combines a zonal airow model, a radiation model, a humiditytransport and condensation model and takes into account resurfa-cing and occupation. This above ice model (AIM) predicts the heatuxes through the envelope aswell as the temperature and absolutehumidity distributions for a 3D transient regime during an entiretypicalmeteorological year. In particular it calculates the heat uxesinto the ice sheet by convection, radiation and condensation. Thetemperature below the ice sheet was assumed uniform andconstant. The results show a satisfactory agreement with corre-sponding measurements and CFD calculations.

    The present article describes a second part in the developmentof a global 3D transient model of an ice rink. The below ice model(BIM) was developed using an implicit unidirectional electricalanalogy, taking into account the secondary loop and brinemovement and the heat gain from the ground (with changingmeteorological conditions). The BIMwas coupled successfullywiththe previously mentioned AIM. The combined model eliminatesthe assumption of constant temperature below the ice sheet usedin AIM. Instead the temperature of the brine entering the pipesbelow the ice sheet must be specied. The combined modelevaluates the return brine temperature, the total refrigeration load,the ice surface temperature (IST), the heat gain from ground, aswell as the energy consumption of the ventilation system and ofthe radiant heaters. Parametric studies were undertaken in orderto evaluate the impact of the climate, brine inlet temperature, icethickness and other parameters on the calculated results and theirresults are presented in the last part of the present paper.

    2. Description and modeling

    2.1. Ice rink description

    Figs. 1 and 2 show a schematic representation of the studied icerink Camilien Houde located in Montreal (Canada). The buildingis 64.2-m long, 41.5-mwide and its height is 9.2 m. The ice surfaceis 61-m long, 25.9-mwide and is surrounded by a narrow corridor.The space above the stands is heated by eight radiant heaters(22 kW 8) which are controlled by a thermostat. Seven inletssupply a stream of ventilation air. Its ow rate is 4270 L/s exceptduring resurfacing of the ice when it is increased to 10,384 L/s toevacuate the combustion gases of the resurfacing vehicle. The airexits through four outlets on thewalls. Heat gains from lighting are10 W/m2 above the ice and 5W/m2 above the stands; those due tothe presence of the audience are also taken into account while thenumber of spectators is specied according to a weekly schedule[7,11]. The ice resurfacing takes place several times per day, lasts12 min and is modeled as a 1 mm lm of hot water at 60 8C. Itsfrequency, specied in the schedule mentioned above, is higher inthe evenings and weekends. The stands, corridors and boards arealso modeled in the AIM.

  • the

    L. Seghouani et al. / Energy and Buildings 41 (2009) 500511502Fig. 1. Schematic section of the ice rink andThe ground structure beneath the ice rink is represented inFig. 1 and comprises horizontal layers of ice (50 mm), concrete(150 mm), thermal insulation (100 mm), sand (200 mm) and,nally, soil. The total depth of this structure included in thecalculation domain is 4 m.

    The secondary coolant used to maintain the ice at the desiredtemperature is calcium chloride brine. It is supplied from aheader located at the west end of the ice sheet and circulates inthe concrete slab at a depth 57.5 mm below the ice surfacewithin 74 uniformly distributed, four-pass polyethylene tubes(25 mm ID). The spacing between tubes is 87.5 mm. The maincollector has an internal diameter of 150 mm. The ow rate ofthe pump is 28.5 L/s.

    An electrical heater of 8 kW is activated in the sand layer whenthe ground temperature at a depth of 4 m is below 4 8C to preventfreezing under the concrete slab which can cause damage to theunderground structure and ice.

    2.2. Model of air movement and heat exchanges above the ice (AIM)

    The air movement and heat exchanges occurring in the rinkabove the ice surface are simulated using a 3D transient modelwith 64 zones [911]. It consists of six coupled submodels solvedwith the onion method. The rst submodel is the energy modelwhich uses theMultizone BuildingModel (type 56) of TRNSYS [12].It is based on two relations. The rst one expresses energy

    Fig. 2. Top view of the ice showing the diffdifferent layers under the ice (not to scale).conservation inside each thermal zone i:

    MCpidTidt

    qcvAi Xj

    m j! iCpT j (1)

    while the second expresses energy conservation for each internalsurface in contact with the air in the building:

    qcd qcv qrd qcond qrs (2)

    The conductive ux through the wall is evaluated using thetransfer functions method while the convection ux between thewall surface and the air inside the building is calculated using aconstant heat transfer coefcient (3 W/m2 K). The radiation uxbetween internal surfaces of the building is provided by asubmodel (radiative transfer submodel) based on the Gebhartmethod [13]. The condensation ux is attributed to the ice surfacewhen its temperature is below the dewpoint of the air above it. It isprovided by a submodel (humidity transport submodel) whichcalculates the absolute humidity of the air in every thermal zoneinside the building using the following conservation equation:

    Mair;idvidt

    Xi; j

    mi; jv j vi Wg;i (3)

    Finally, qrs corresponds to the heat ux occurring when theresurfacing operation deposits approximately 0.5 m3 of water at

    erent zones and the ow of the brine.

  • 60 8C on the ice surface. It is calculated using the equationrecommended by ASHRAE [14].

    The airow mi,j between thermal zones used in Eq. (1) isprovided by the zonal airow submodel. The formulation usedexpresses the mass ow crossing the common surface betweentwo zones i and j in terms of their pressure difference. Thus, in thecase of a vertical interface

    mi; j ei; jCd2ri

    pAi; jjP j Pij1=2 (4)

    While in the case of a horizontal interface

    Fig. 3. Schematic representation

    L. Seghouani et al. / Energy and Buildings 41 (2009) 500511 503mi; j ei; jCd2ri

    pAi; j P j Pi

    1

    2righi r jgh j

    1=2

    (5)

    The coefcient eij is equal to +1 when ow is from zone i to zonej and equal to 1 for ow from zone j to zone i.

    A new submodel not described in our previous publications[9,10] is used to simulate the behaviour of the ventilationsystem. It consists of two units (see Fig. 3). The rst one is usedfor cooling, dehumidifying and reheating the external air whenits temperature is above 23 8C while the second unit is forheating and humidifying it when its temperature is below 15 8C.When the temperature of the entering air is between 23 8C and15 8C none of the units is in operation unless the humidity levelis too high or too low. The humidity controls are such that therelative humidity of the air entering the ice rink is maintainedbetween 20% and 33%. The equations modeling the operation ofthese two units are the mass and energy conservation equationsfor a gasvapour mixture in a steady state, steady ow process.It should be noted that...

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