Nielsen, Peter V.

Ravn, Peter

Rong, Li

Tong, Guohong

Zhang, Guoqiang

English

    Aalborg UniversitetEffect of Environmental Deflector on Air Exchange in Slurry Pit and ConcentrationDistribution in a Two-dimensional Ventilation ChamberZhang, Guoqiang; Tong, Guohong; Ravn, Peter; Rong, Li; Nielsen, Peter V.Published in:AgEng2008 : International Conference on Agricultural EngineeringPublication date:2008Document VersionPublisher's PDF, also known as Version of recordLink to publication from Aalborg UniversityCitation for published version (APA):Zhang, G., Tong, G., Ravn, P., Rong, L., & Nielsen, P. V. (2008). Effect of Environmental Deflector on AirExchange in Slurry Pit and Concentration Distribution in a Two-dimensional Ventilation Chamber. In AgEng2008: International Conference on Agricultural Engineering: Agricultural & Biosystems Engineering for a SustainableWorld : Knossos Royal Village, Hersonissos - Crete, 23-25 June 2008, Greece : Book of Abstracts (pp. 15).AgEng.General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright ownersand it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.            ? Users may download and print one copy of any publication from the public portal for the purpose of private study or research.            ? You may not further distribute the material or use it for any profit-making activity or commercial gain            ? You may freely distribute the URL identifying the publication in the public portal ?Take down policyIf you believe that this document breaches copyright please contact us at vbn@aub.aau.dk providing details, and we will remove access tothe work immediately and investigate your claim.

Effect of Environmental Deflector on Air Exchange in Slurry Pit and Concentration Distribution in a Two-dimensional Ventilation Chamber

Variations of air exchanges in slurry pit with four angles of an environmental deflector, namely 0° (parallel to the side wall or without deflector), 30°, 45° and 90°, were investigated using a tracer gas method. The investigations were performed in a two-dimensional ventilation chamber in the Air physics Lab, University of Aarhus. Ventilation rates used in the experiments were 100 and 200 m3/h. The experiment results showed that using the deflectors of 30°, 45° and 90° the airflow patterns were obviously changed in the room space near the slatted floor and in the head space of the pit compared with the setup without deflector. It was also found that of all the deflector angle performances with respect to air-exchange ratio and concentration distribution, the deflector position of 45° in two airflow rates cases behaved better with the lowest pit ventilation and the highest concentration in the head space.Variations of air exchanges in slurry pit with four angles of an environmental deflector, namely 0° (parallel to the side wall or without deflector), 30°, 45° and 90°, were investigated using a tracer gas method. The investigations were performed in a two-dimensional ventilation chamber in the Air physics Lab, University of Aarhus. Ventilation rates used in the experiments were 100 and 200 m3/h. The experiment results showed that using the deflectors of 30°, 45° and 90° the airflow patterns were obviously changed in the room space near the slatted floor and in the head space of the pit compared with the setup without deflector. It was also found that of all the deflector angle performances with respect to air-exchange ratio and concentration distribution, the deflector position of 45° in two airflow rates cases behaved better with the lowest pit ventilation and the highest concentration in the head space

    Aalborg UniversitetEffect of Environmental Deflector on Air Exchange in Slurry Pit and ConcentrationDistribution in a Two-dimensional Ventilation ChamberTong, Guohong; Zhang, Guoqiang; Ravn, Peter; Rong, Li; Nielsen, Peter V.Published in:AgEng 2008 International Conference on Agricultural EngineeringsPublication date:2008Document VersionPublisher's PDF, also known as Version of recordLink to publication from Aalborg UniversityCitation for published version (APA):Tong, G., Zhang, G., Ravn, P., Rong, L., & Nielsen, P. V. (2008). Effect of Environmental Deflector on AirExchange in Slurry Pit and Concentration Distribution in a Two-dimensional Ventilation Chamber. In AgEng 2008International Conference on Agricultural Engineerings: Conference Proceedings CD : Agricultural & BiosystemsEngineering for a Sustainable World : Knossos Royal Village, Hersonissos - Crete, 23-25 June 2008, GreeceAgEng.General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright ownersand it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.            ? Users may download and print one copy of any publication from the public portal for the purpose of private study or research.            ? You may not further distribute the material or use it for any profit-making activity or commercial gain            ? You may freely distribute the URL identifying the publication in the public portal ?Take down policyIf you believe that this document breaches copyright please contact us at vbn@aub.aau.dk providing details, and we will remove access tothe work immediately and investigate your claim.EFFECT OF ENVIRONMENTAL DEFLECTOR ON AIR EXCHANGE IN SLURRY PIT AND CONCENTRATION DISTRIBUTION IN A TWO-DIMENSIONAL VENTILATION CHAMBER Guohong Tong1,2), Guoqiang Zhang1)*, Peter Ravn1), Li Rong3), Peter V. Nielsen3)  1)  Department of Agricultural Engineering, Research Centre Bygholm, University of Aarhus, Schüttesvej 17, DK-8700 Horsens, Denmark, E-mail of corresponding author: guoqiang.zhang@agrsci.dk  2)  College of Water Conservancy, Shenyang Agricultural University, Shenyang 110161, China,  E-mail: guohongtong@yahoo.com.cn  3)  Department of Civil Engineering, University of Aalborg, Sohngaardsholmsvej 57, DK-9000 Aalborg E-mail: pvn@civil.aau.dk  Abstract Variations of air exchanges in slurry pit with four angles of an environmental deflector, namely 0° (parallel to the side wall or without deflector), 30°, 45° and 90°, were investigated using a tracer gas method. The investigations were performed in a two-dimensional ventilation chamber in the Air physics Lab, University of Aarhus. Ventilation rates used in the experiments were 100 and 200 m3/h. The experiment results showed that using the deflectors of 30°, 45° and 90° the airflow patterns were obviously changed in the room space near the slatted floor and in the head space of the pit compared with the setup without deflector. It was also found that of all the deflector angle performances with respect to air-exchange ratio and concentration distribution, the deflector position of 45° in two airflow rates cases behaved better with the lowest pit ventilation and the highest concentration in the head space. Key words: ventilation, slurry pit, environmental deflector, tracer gas 1. Introduction        The interaction between air movements in the room and in the slurry channel affects the odorant and ammonia transport in and total emission from ventilated livestock production buildings. Air motion is manipulated mainly by the ventilation, and its pattern is related to the distribution of contaminant inside the building (Arogo, et al., 1997; Zhang and strøm,1999; Demmers, et al. 2000; Morsing et al., 2008). Ventilation effectiveness was affected by many factors, such as inlet and outlet locations (Zhang et al. 2001, Chung and Hsu, 2001), Pen partitions (Bjerg et al. 2000), slat orientations and manure depths (Buiter and Hoff,1998), locations of the pollutant source (Demmers, et al. 2000), ventilation rates (Buiter and Hoff,1998, Demmers, et al. 2000), ventilation methods (Yang et al. 2004) and so on.  The  2ventilation effectiveness will affect on local air mixings and consequently on emission from the ventilated room space. Furthermore, Local air velocities play important roles on contaminant emission. Zhang et al. (1994) indicated that increasing the air velocities over the manure surface result in increased ammonia releasing from manure pits. Therefore, reducing the air ventilation in slurry pit to decrease the ammonia transport in and emission from livestock building became more interested.          The objective of this study was to apply an airflow deflector in room to adjust the air movements in the room and slurry pit. Four angles of the deflector, namely 0° (parallel to the side wall or without deflector), 30°, 45° and 90°, were investigated in a two-dimentional ventilation chamber in the Air physics Lab, University of Aarhus. The key objective of this study is to evaluate the ventilation effectiveness for the positions of deflector. Figure 1. Two-dimensional ventilation chamber and concentration sampling positions. 2. Materials and methods 2.1 2D chamber A two-dimensional ventilation chamber in the Air physics Lab, University of Aarhus was established to investigate the performances of environmental deflector on pit ventilation (Fig.1). The chamber was with inside dimensions 2.18 m×2.41 m × 0.62 m. The front face was made of laminated glasses, and the back and side plywood surfaces were painted in dark colours in order to facilitate visualization of airflow patterns with illuminated smoke. An adjustable flap wall inlet was installed in one side wall beneath the ceiling and the room air was exhaust via an opening at the middle of the side wall. The deflector was installed at the Emission surface Deflector Outlet Inlet 112 2 3 3 4455 3side wall opposed to the inlet wall 0.8 m above the slatted floor. Four angles of the deflector, namely 0° (parallel to the side wall or without deflector), 30°, 45° and 90°, were used in the investigations. 2.2 Experiment set up and Measurement The ventilation rates used in the experiments were 100 and 200 m3/h. A constant CO2 tracer gas flux of 50 ml/min was supplied in a conditioning space under the emission surface, given a height of the pit headspace was 280 mm. A reference point, which is at 20 mm beneath the emission surface, in the conditioning space was used to monitor the CO2 concentration in the air before it defused via the emission surface to the slurry channel. Besides the concentration measurements for the inlet air and exhaust air, the CO2 concentrations were also measured at five sampling positions 150 mm above the slatted floor upper surface and five sampling positions 150 mm under the slatted floor lower surface (Fig.1). The inlet velocities were measured by a single-dimensional Laser Doppler anemometer (DANTEC measurement technology, Denmark). Air Flow Tester (Dräger Sicherheitstechnik GmbH, Germany) was used to generate smoke and indicate the direction of local airflow to provide a quick visualization of the path of the airstreams and pressure differentials. The CO2 concentration at the reference point was monitored by Testo 400 (Testo GmbH & Co., Germany). CO2 concentration at outlet was measured by an infrared gas analyzer, while CO2 concentrations at five points above /under the slatted floor and at inlet were measured by INNOVA 1312 Photoacoustic Multi-gas Monitor (Innova Air Tech Instruments A/S, Denmark) with a dynamic range of five orders of magnitude and a range drift of ±2.5% of measured value per 3 months (measurement at 20oC, 1013 mbar, and relative humidity 60%). The sampling period for a recorded data was 20 s. During the experiment, CO2 concentrations at the five sampling points under the slatted floor were measured till at the stable constant concentration, and then changed to measure the five sampling points above the slatted floor, where the data recording was also continued till the stable constant concentration condition. 2.3 Evaluation method In order to describe the air exchange rates in the slurry channel under different experimental conditions, the ratio between air exchange rate in the pit and room ventilation rate was applied to evaluate the effects of the deflectors. This air exchange ratio is expressed as  4roompitinletoutletoutpitpr CCCCQQR−−==                                                                                                                 (1) where, Qpit is the pit ventilation airflow rate; Qout is the design airflow rate, 100m3/h and 200 m3/h; Coutlet, Cinlet, Cpit and Croom are average CO2 concentration at outlet, inlet and under the slatted floor and above the slatted floor.       The less the value of the Rpr, the more effective the deflector positions is for contaminant control.    To evaluate local ventilation effectiveness affected by the deflector, the local ventilation effectiveness factors (VEF) defined by Zhang et al. (2001) was used,       inletiinletoutletEFi CCCCV−−=                                                                                                                         (2) where, iC is the average CO2 concentration at ith sampling positions above/below the slatted floor. The dimensionless factor VEF used in this study is to interpret the local concentration distribution above/below slatted floor compared with that at outlet for different deflector positions. The more the value of the VEF above the slatted floor near the outlet side, the deflector position is more effective; the less the value of the VEF below the slatted floor near the outlet side, the deflector position is more effective. Figure 2. CO2 concentration at the reference position of the mixing space with deflector position of 90°, where, ×, room ventilation rate of 200m3/h, and ◊, 100m3/h   3. Results and discussion 0200040006000800010000120001400016000180000 50 100 150 200 250Time, minCO2 concentration, mg/m3 53.1 Averaging period of constant concentration The average period of constant concentration at the reference point and at sampling points took place after the CO2 releasing about 40 min for 200 m3/h set-up and about 70 min for 100 m3/h set-up. CO2 concentration profile at the reference point was shown in Fig.2. The CO2 concentration during averaging period at the reference position for 100m3/h varied from a minimum of 14832.2 mg/m3 to a maximum of 15353.7 mg/m3 with percentage variations from 1.6% to 1.8% relative to the average concentration; during the averaging period for 200m3/h varied from a minimum of 5588.8 mg/m3 to a maximum of 5982.3 mg/m3 with percentage variations from 2.6% to 4.2% relative to the average concentration. It is also found that the CO2 concentration during averaging period at the reference position for 100m3/h is nearly three times of that for 200 m3/h. 3.2 Pit ventilation ratio Pit ventilation ratios at different deflector positions based on Eq.1 for different room ventilation rates were shown in Fig.3.          Figure 3. Pit ventilation ratio at different deflector positions and room ventilation rates, where, positions 1=0°, 2=30°, 3=45° and 4=90°; ×, 100m3/h, and ◊, 200m3/h The pit ventilation ratios varied dramatically with deflector positions for the ventilation rate of 200 m3/h and got higher value at deflector position of 30°and lower value at 45°. Compared with the 200 m3/h condition, the pit ventilation ratios were consistently lower for 100m3/h with the largest deviation among deflector positions was below 1%.  The Fig. 3 indicated that the deflector position of 45° gave the lower pit ventilation ratio when the two room ventilation rates were concerned. 0%10%20%30%40%50%60%0 1 2 3 4 5Deflactor positionsPit ventilation ratio, % 63.3 Local ventilation effectiveness factor When the specific locations above/below the slatted floor became the concerned positions, the ventilation effectiveness for different deflector positions was evaluated by local ventilation effectiveness factors shown in Fig.4.                (a)                                                                                            (b) Figure 4. Local ventilation effectiveness factors above the slatted floor (up) and below the slatted floor (bottom) for room ventilation rate of 100m3/h (a) and 200m3/h (b), (○) stands for deflector position of 0°; (×) stands for 30°; ( Δ ) stands for 45°and (+) stands for 90°. The results showed that using the deflector positions of 30°, 45° and 90° the ventilation effectiveness factors were obviously varied in the room space near the slatted floor and in the head space of the pit compared with the setup of 0°(without deflector). The ventilation effectiveness factors for the two ventilation rates were substantially different with the values lower for 100 m3/h and higher for 200 m3/h (Fig. 4), however, this conclusion is different against the conclusion drawn from Zhang et al. (2001), which suggested that ventilation effectiveness was less affected by ventilation rate. In Fig. 4a, the average effectiveness factor for 45° at the position above the slatted floor was larger and below the slatted floor was smaller than for other deflector positions, 00.20.40.60.811.20 0.5 1 1.5 2x,mVEF00.10.20.30.40.50.60.70.80.90 0.5 1 1.5 2x,mVEF01234560 0.5 1 1.5 2x,mVEF00.20.40.60.811.20 0.5 1 1.5 2x,mVEF 7respectively. In Fig. 4b, the average effectiveness factor for 45° at the position below the slatted floor was smaller than that for other deflector positions. Hence, deflector position of 45° is more effective. However, the value at the position above the slatted floor was somewhat lower than the positions of 0°and 30° and deserves further investigation. 4. Conclusions   (1) Deflector can adjust the air motion in the room space near the slatted floor and in the head space of the pit.  (2) Deflector position of 0° (parallel to the side wall or without deflector), 30°, 45° and 90° were used in the investigation, 45°among them in two airflow rates cases behaved better with the lowest pit ventilation and the highest concentration in the head space. (3) Ventilation rates have obvious influence on pit ventilation and local ventilation effectiveness factor. References Arogo J., Zhang R.H., Riskowski G.L., Christianson L.L., Day D.L.. Mass transfer coefficient of ammonia in liquid swine manure and aqueous solutions. Journal of Agricultural Engineering Research. 1997, 73, 77-86. Bjerg B., Svidt K., Zhang G., Morsing S.. The effects of pen partitions and thermal pig simulators on airflow in a livestock test room. Journal of Agricultural Engineering Research. 2000, 77 (3), 317-326. Buiter J.J., Hoff S.J.. Ammonia distribution in a pit-ventilated confinement building: one-half scale model study. Transactions of the ASAE. 1998, 41(6), 1817-1827. Chung K., Hsu S.. Effect of ventilation pattern on room air and contaminant distribution. Building and Environment. 2001, 36, 989–998. Demmers T.G.M., Burgess L.R., Phillips V.R., Clark J.A., Wathes C.M.. Assessment of techniques for measuring the ventilation rate, using an experimental building section. Journal of Agricultural Engineering Research. 2000, 76, 71-81. Morsing S; Strøm J S; Zhang G; Kai P (2008). Scale model experiments to determine the effects of internal air-flow and floor design on gaseous emissions from animal houses. Biosystems Engineering, 99(1), 99-104 Yang X., Srebric J., Li X., He G.. Performance of three air distribution systems in VOC removal from an area source. Building and Environment. 2004, 39, 1289 – 1299. Zhang G., Strøm J.S.. Jet drop models for control of non-isothermal free jets in a side-wall multi-lint ventilation system. Transactions of the ASAE. 1999, 42(4), 1121-1126 Zhang, R., Day D. L., Christianson L. L., Jepson W. P.. A computer model for predicting ammonia release rates from swine manure pits. Journal of Agricultural Engineering Research, 1994, 58(4), 223-229. Zhang Y., Wang X., Riskowski G. L., Christianson L. L.. Quantifying ventilation effectiveness for air quality control. Transactions of the ASAE. 2001, 44(2), 385–390. Formateret: Dansk (Danmark)

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Effect of Environmental Deflector on Air Exchange in Slurry Pit and Concentration Distribution in a Two-dimensional Ventilation Chamber

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