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1 Downloaded from vbn.aau.dk on: January 3, 219 Aalborg Universitet Dust Load on Surfaes in Animal Buildings an experimental measuring method Lengweiler, P. ; Strøm, J. S. ; Takai, H. ; Ravn, P. ; Nielsen, Peter Vilhelm; Moser, A. Publiation date: 1998 Doument Version Publisher's PDF, also known as Version of reord Link to publiation from Aalborg University Citation for published version (APA): Lengweiler, P., Strøm, J. S., Takai, H., Ravn, P., Nielsen, P. V., & Moser, A. (1998). Dust Load on Surfaes in Animal Buildings: an experimental measuring method. Aalborg: Dept. of Building Tehnology and Strutural Engineering. Indoor Environmental Engineering, No. 91, Vol.. R9844 General rights Copyright and moral rights for the publiations made aessible in the publi portal are retained by the authors and/or other opyright owners and it is a ondition of aessing publiations that users reognise and abide by the legal requirements assoiated with these rights.? Users may download and print one opy of any publiation from the publi portal for the purpose of private study or researh.? You may not further distribute the material or use it for any profit-making ativity or ommerial gain? You may freely distribute the URL identifying the publiation in the publi portal? Take down poliy If you believe that this doument breahes opyright please ontat us at vbn@aub.aau.dk providing details, and we will remove aess to the work immediately and investigate your laim.

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3 The Indoor Environmental Engineering papers are issued for early dissemination of researh results from the Indoor Environmental Engineering Group at the Department of Building Tehnology and Strutural Engineering, Aalborg University. These papers are generally submitted to sientifi meetings, onferenes or journals and should therefore not be widely distributed. Whenever possible, referene should be given to the final publiations (proeedings, journals, et.) and not to the Indoor Environmental Engineering papers. Printed at Aalborg University

4 Dust Load on Surfaes in Animal Buildings: An Experimental Measuring Method P Lengweilet~ J. S. Stmm, H. Takai, P Ravn, P V Nielsen, A. Maser

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6 En Oslo--- EurAgEng Paper no: 98-G-15 Title: DUST LOAD ON SURFACES IN ANIMAL BUILDINGS: ~ AN EXPE~RIMENTAL MEASURING METHOD. Authors: P. Lengweiler 1, J.S. Strm 2, H. Takai 2, P. Ravn 2, P.V. Nielsen 3, A. Moser 1 1 Air&Climate Group, Researh in Building Tehnology, ETH Zurih, ETH Zentrum, 892 Zurih, Switzerland 2 Danish Institute of Animal Siene, Researh Centre Bygholm, 87 Horsens, Denmark 3 Department ofbuilding Tehnology and Strutural Engineering, Aalborg University, Sohngaardsholmsvej 57, 9 Aalborg, Denmark Summary: To investigate the physial proess of partile deposition on and resuspension from surfaes in animal buildings, a test faility and a sampling method is established. The influenes of surfae orientation and air turbulene and veloity just as other parameters on the dust load on a surfae are analysed. It is found that the surfae orientation is the parameter whih influenes the dust load most. The dust load is highest on the floor but some dust is also sampled on the walls and the eiling. The measurements indiate that the air veloity has a non-linear influene and that the turbulene has a larger effet on the deposition than on the resuspension. Therefore high turbulene auses high dust load. However, the influene of turbulene and veloity are strongly dependent on eah other and annot be analysed in isolation.

7 INTRODUCTION High onentrations of organi dust in animal buildings, primarily in swine buildings, have shown to ause health problems for both people and animals. To develop methods to eliminate dust related problems, there is, among other things, a need for better understanding of the mehanism behind dust deposition and resuspension. Dust deposition an redue onsiderably the airborne dust onentration and, on the other hand, resuspension an inrease the onentration for more than 1 % (Goddard et al. 1995). The dust load is the amount of dust building up on the surfae. The dust load is thus the balane between the mehanism of dust deposition on and resuspension from the surfae. The deposition is defined as the rate of settling partiles on the surfae and the resuspension is the rate of removal of partiles from the surfae. Both deposition and resuspensiofl are dependent on environmental onditions like air veloity and turbulene, on the surfae onditions like orientation and roughness, on the type of partiles and on other fores. Ideally, knowledge of both mehanism is needed, but as a first step the fous is on improved knowledge of fators that influene the dust load. The purpose of this paper is to desribe a faility to measure dust load on different materials used for differently orientated surfaes in animal buildings. Results from a first series of measurements is used as an example of the appliation of the faility and to show the suitability of the experimental set-up. METHOD Most of the basi information annot be determined by measurements taken in atual animal buildings beause of unknown elements suh as the amount of dust present, air veloity and turbulene. This fundamental knowledge an only be attained when the experiments are anied out in a ontrolled laboratory environment. Experimental set-up A small wind tunnel with the dimensions 3.x.5x.5 m is hosen as the experimental area (Figure 1 ). It is omposed of three parts, namely, the inlet, the working setion and the outlet. The inlet, plaed upstream of the working setion, is well rounded in order to obtain a uniform veloity and turbulene profile in the working setion. To produe different levels of turbulene in the experimental setion, sreens with different perforation levels an be installed at the wind tunnel inlet. The dust load is measured on surfae panels plaed inside the experimental setion faing up (floor), vertial (wall) and faing down (eiling). They have eah an area of 1.15x.45 m and the distane to the wind tunnel inlet is I m. To have good aess to these panels the experimental setion an be opened. 2

8 The air is drawn through the wind tunnel by a fan plaed at the end of the outlet setion with adjustable speed in order to adjust air veloity to pre-set values. V air measuring Figure 1 Shemati experimental set-up. The wind tunnel itself is plaed in a losed room where the dust onentration is ontrolled to stable levels. The dust is produed with a multi-point dust generator, developed by the Researh Centre Bygholm (Takai et al. 1996). The dust is blown into the room and distributed with a ventilator. To get a onstant dust level over the time, it is neessary to filter out the dust of the irulating air. Measuring methods The dust load on the experimental surfaes is measured by vauum leaning the sampling surfaes with a speial leaning head ontaining glass fibre filter whih ollets the partiles (Figure 2). The amount of sampled dust is determined as the differene in weight of the filter before and after sampling. 3

9 vauum leaner sampling filter lean surfae Figure 2 Dust sampling system with vauum leaner and glass fibre filter. It is diffiult to remove all the partile from the surfae by vauum leaning, espeially the small ones. To make sure that the amount of partiles left on the surfae after sampling an be negleted, i.e. the sampling effiieny is high, the tape tehnique desribed by Shneider et al. (1987) is used. The airborne onentration at the wind tunnel inlet is measured by an Aerodynami Partile Sizer (APS) and by isokineti sampling inside the working setion. The air veloity and turbulene over the ross-setion of the working setion are measured by Laser Doppler Anemometry (LDA). The turbulene is determined as the variane of the air veloity. Moreover, a referene veloity is defined by the air volume stream through the wind tunnel. The temperature of the air, the relative humidity and the eletrostati harge are also measured, but not ontrolled. EXAMPLE OF THE APPLICATION As an example of the appliation wood-fibre plates are hosen as surfae material for all three orientations. By seleting the artifiial dust, the main purpose is to get a similar size distribution as swine dust. Therefore talum is hosen whih is moreover heap and easily available. The experiments are arried out in summer and winter onditions, i.e. a relative humidity in the air of around 6 % resp. 3 % and an air temperature of around 26 C resp. 22 C. Different veloities from.1 rnls to 1.1 m/s and two nominal turbulene levels, namely 2 % (low) and 6 % (high), are hosen. 4

10 During the experiments, the amount of dust in the air is around 5xl 5 partiles per litre air. This gives a reasonable amount of dust on the surfaes by running the experiments for 3 minutes. Sine all experiments are arried out with the same duration, no estimation about the time dependene of the dust load an be made. RESULTS AND DISCUSSION The first series of experiments show that it is possible to measure the dust load on the surfaes with the presented experimental set-up. The applied method gives reproduible results. The verifiation of the sampling effiieny with the tape tehnique demonstrates that only very few and small partiles annot be piked up by the vauum system. Hene the sampling effiieny referring to the mass of the dust is high. In Figures 3 the dust load is shown as a funtion of the air veloity under summer onditions with a variation of the surfae orientation and, for the floor, of the turbulene and relative humidity. 2.5!C! 2. 'Cii.., E 1.5 -Cl - -N- E 1..9 ~.5 e 1) Floor, Tu high 3) Wall, Tu high v--1 2) Floor, Tu low 4) Ceiling, Tu high / r""""' - / - ~ ~ -"" 2.. 3). - 4) veloity [m/s] Figure 3 Dust load on three different surfae orientations. The parameter whih influenes the dust load most is obviously the surfae orientation. Atually the surfae orientation desribes the gravity fore normal to the surfae. Therefore, no dust would be deposited on the wall and the eiling without turbulene or other fores. As expeted the highest dust load is found on the floor, but unlike assumed in most models in literature, the dust load on the walls and eiling is not 5

11 equal to zero. Considering the whole area whih is overed by the walls and the eiling, the influene of these surfaes on the airborne dust onentration an not be negleted at all. The influene of the turbulene and the veloity annot be analysed separately from other parameters sine they are dependent on eah other. A more detailed disussion about this phenomenon and about the influene of the relative humidity an be found in Lengweiler et al. (1998). However, it seems that the dust load depends on the ombined effet of both turbulene an veloity beause at a higher veloity more partiles are transported whih an be deposited by the turbulene. Comparing the wind tunnel experiments with animal buildings, a referene material has to be hosen whih has a well defined surfae struture, e.g. stainless steel. To get more detailed knowledge about the building up of the dust load, the mehanial proesses or deposition and resuspension have to be analysed separately, just as parameters like the eletrostati fore. A problem of the method is that a ompromise between maximum dust load on the floor and minimum dust load on the eiling has to be made. A too small amount of dust just as a too high amount gives a high inauray by weighing the sampling filter. Another disadvantage is that several experiments have to be done for analysing the time dependeny on the dust load. CONCLUSIONS The following onlusions are drawn from this researh: ( 1) Dust loads on surfaes an be measured by the method proposed in this researh under different environmental onditions, but a refinement of the method is neessary and also possible; (2) The surfae orientation is the most important parameter for the dust load, however the dust load on the walls and eiling may not be negleted; (3) Other parameters annot be analysed separately from eah other; (4) A refinement ofthe method is neessary to measure deposition and resuspension individually. ACKNOWLEDGEMENT This researh was supported finanially by the Danish Tehnial Researh Counil (STVF) as a part of the researh programme "Healthy Buildings" and the Swiss National Siene Foundation (SNF), researh number NF All experiments were arried out at the Researh Centre Bygholm, Denmark. 6

12 REFERENCES 1. Goddard, A.J.H.; Byme, M.A.; Lange, C. et al Aerosol Indoors: Deposition on Indoor Surfaes, Air Infiltration Review, Vol. 16, No. 2, Marh 1995, pp Lengweiler, P.; Nielsen, P.V.; Moser, A. et al Deposition and Resuspension of Partiles: Whih Parameters are important?, Roomvent '98, Stokholm (Sweden), Vol. 1, pp Shneider, T.; Eriksen, P.; Petersen,. et al Easy Method for Measuring the Quality of Cleaning, Indoor Air Quality and Climate '87, Berlin (Germany). 4. Shaw, B.W Use of a Convetive Emission Chamber to Study Partile Resuspensif!n, PhD thesis, University of Illinois at Urbana-Champaign. 5. Takai, H.; Jaobson, L.D.; Morsing, S. et al Multi-point dust generator for simulation of dust dispersion in ventilated air spaes, Roomvent '96, Tokyo (Japan), Vol. 2, pp

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14 RECENT PAPERS ON INDOOR EN VIRO NMENTAL ENGINEERING PAPER NO. 79: P.V. Nielsen: Design ofloal Ventilation by Full-Sale and Sale Modelling Tehniques. ISSN R9743. PAPER NO. 8 : P. Heiselberg, K. Svidt, H. Kragh: Appliation of CFO in Investigation of Ventilation Strategies for Improvement of Working Environment in a Waste Inineration Plant. ISSN R9745. PAPER NO. 81 : P. Heiselberg, C. Topp: Removal of Airborne Contaminants from a Swfae Tank by a Push-Pull System. ISSN R PAPER NO. 82: P. Heiselberg: Simplified Method for Room Air Distribution Design. ISSN R PAPER NO. 83: L. Davidson, P.V. Nielsen: A Study of Laminar Bakward-Faing Step Flow. ISSN R982. PAPER NO. 84 : P.V. Nielsen: Aidlow in a World Exposition Pa vilion Studied by Sale-Model Experiments and Computational Fluid Dynamis. ISSN R9825. ~ PAPER NO. 85 : P.V. Nielsen: Stratified Flow in a Room with Displaement Ventilation and Wall-Mounted Air Terminal Devies. ISSN R9826. PAPER NO. 86 : P.V. Nielsen: The Seletion of Turbulene Models for Predition of Room Aitflow. ISSN R9828. PAPER NO. 87 : K. Svidt, G. Zhang, B. Bjerg : CFO Simulation of Air Velo ity Distribution in Oupied Livestok Buildings. ISSN R PAPER NO. 88 : P. V. Nielsen, T. Tryggvason : Computational Fluil Dynamis and Building Energy Petformane Simulation ISSN R9832. PAPER NO. 89 : K. Svidt, B. Bjerg, S. Morsing, G. Zhang : Modelling of Air Flow th rough a Slatted Floor by CFO. ISSN R9833. PAPER NO. 9 : J.R. Nielsen, P.V. Nielsen, K. Svidt: The Influene of Furn iture on Air Veloity in a Room- An Isothermal Case. ISSN R9843. PAPER NO. 91 : P Lengweiler, J.S. Strrn, H. Taka i, P. Ra vn, P.V. Nielsen, A. Maser: Oust Load on Swfaes in Animal Buildings: An Experimental Measuring Method. ISSN R9844. PAPER NO. 92 : P. Lengweiler, P.V. Nielsen, A. Maser, P. Heiselberg, H. Takai : Deposition and Resuspension of Pat1iles: Whih Parameters are linpol1ant? ISSN R9845. PAPER NO. 93 : C. Topp, P.V. Nielsen, P. Heiselberg, L.E. Spa rks, E.M. Howard, M. Mason: Experiments on Evaporative Emissions in Ventilated Rooms. ISSN R9835. PAPER NO. 94 : L. Davidson, P.V. Nielsen: A Study of Low-Reynolds Number Effets in Bakward-Faing Step Flow using Large Eddy Simulations. ISSN R9834. Complete lis t of papers:

15 ISSN R9844 Dept. of Building Tehnology and Stru tural Engineering Aalborg University, Deember 1998 Sohngaarlsholmsvej 57, DK-9 Aalborg, Denmark Phone Fax : http ://iee.ivil.au. dk