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Effect of humanoid shaped obstacle on the velocity
Effect of humanoid shaped obstacle on the velocity
Effect of humanoid shaped obstacle on the velocity
Effect of humanoid shaped obstacle on the velocity
Effect of humanoid shaped obstacle on the velocity
Effect of humanoid shaped obstacle on the velocity
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Effect of humanoid shaped obstacle on the velocity

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  • 1. INTERNATIONAL Mechanical Engineering and Technology (IJMET), ISSN 0976 – International Journal of JOURNAL OF MECHANICAL ENGINEERING 6340(Print), ISSN 0976 – 6359(Online) Volume 3, Issue 3, Sep- Dec (2012) © IAEME AND TECHNOLOGY (IJMET)ISSN 0976 – 6340 (Print)ISSN 0976 – 6359 (Online) IJMETVolume 3, Issue 3, September - December (2012), pp. 511-516© IAEME: www.iaeme.com/ijmet.aspJournal Impact Factor (2012): 3.8071 (Calculated by GISI) ©IAEMEwww.jifactor.com EFFECT OF HUMANOID SHAPED OBSTACLE ON THE VELOCITY PROFILES OF FLOW OF AIR CURTAIN Mr Nitin Kardekar, Research Scholar, Singhania University Principal JSPM’s Jayawantrao Sawant Polytechnic. Pune. Dr Sane N K, Research Supervisor, Singhania University Professor Emeritus, JSPM’s JSCOE, Pune ABSTRACT A prototype is developed in the laboratory in order to simulate the conditions of the entrance of the doorway. The air curtain device is mounted above the doorway. An obstacle of human shape is placed in the doorway to simulate the real time situation. The air curtain blows the air in downward direction. The flow within the air curtain is simulated with commercial Computational Fluid Dynamics (CFD) solver, where the momentum equation is modelled with Reynolds-Average Navier-Stokes (RANS), K- ε turbulence model. The boundary condition set up is similar to the experimental conditions. The CFD results are compared and validated against experimental results, after the validation stage and the air curtain velocity profiles are compared for with obstacle situations. The results are obtained in the form of contours for velocity profile at different planes. The contour plots of velocity profile are analysed and are discussed for the two cases are reported and discussed in this paper. This paper also highlights the gray areas in the flow domain where effect of air curtain is weak. Key words: Air curtain, Reynolds-averaged Navier – Stokes equation, K- ε turbulence model, turbulent kinetic energy INTRODUCTION Air curtains are the devices that provide a dynamic barrier instead of physical barrier between two adjoining areas thereby allowing easy physical access between them. The air curtain consist of fan unit that produces the jet forming barrier to heat, moisture, dust, odours etc. The Air curtains are extensively used in cold rooms, display cabinets, entrance of retail store, banks and similar frequently used entrances. Study found that air curtains are also finding applications in avoiding smoke propagation, biological controls and explosive detection portals. According to research by US department of energy1875MW energy will be saved per year if super market display cabinet air curtain will be operated at optimised performance. In 2002 the UK food and drinks industry used equivalent of 285 tonnes of oil to power its refrigeration industry, with most being used in cold storage. In developing countries like India; the rise in cold storages, super markets, retail stores, banks are not only limited to 511
  • 2. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –6340(Print), ISSN 0976 – 6359(Online) Volume 3, Issue 3, Sep- Dec (2012) © IAEMEmega cities but they are the integral part of suburban’s and small towns as well. The effectsof globalisation are inevitable. The air curtains are no more luxury but they are the necessarypart of business development and the economy. Hence the study of air curtain with respect toIndian climate is upmost necessary to ensure optimised performance of air curtains whichleads to energy conservation. The saving of energy (Electrical energy) will be always boonfor energy starving country like India.METHODOLOGYThe air flow analysis was carried out using commercial software package ANSYS V13.0Workbench platform. As shown in Figure 1 the air curtain is mounted on the top of theframe. The doorway frame chosen is 2270 mm in height and 900 mm in width, the breadth ofthe frame is 290 mm. There are two slits opens in the domain; the flow jet is pushed by theblower in the domain through these slits. The slits are 84 mm away as shown in the Figure 9.This area is referred as midsection. The entire experiment is carried out at isothermalconditions; air at 240C ( + 10C) at one atmosphere, the velocity of leaving air from slits is 9m/s. Similar conditions are used for analysis, this velocity is representative of air curtainflow velocity. The domain is extended to capture the flow of air leaving frame boundaries indirections of frame openings. The frame walls are treated as impermeable walls, and are ‘noslip’ walls. It is ensured while choosing the length of extended domain that the directtransverse flow of air curtain will not cross the boundaries of the domain. Ones theconfiguration is modelled, the mesh is generated in the workbench. The structured mesh(hexahedron mesh) is used to build the extended domain and flow straightener. The frameportion is meshed with unstructured tetra mesh. The effort was made to mesh the entiredomain with structured mesh but due to complex geometry at the flow straightener the frameportion has unstructured mesh. The total mesh count is 385443, within which 59589 aretetrahedral cells and 325854 hexahedral cells. The minimum mesh quality is 0.3, total 708cells falls within this range, as per the CFD Practices this is a good quality mesh. The meshwhich is created in the Workbench is internally transferred to CFX-Pre, a CFD solveravailable with workbench platform. The flow within the air curtain is simulated withincommercial Computational Fluid Dynamics (CFD) solver, where the momentum equation ismodelled with Reynolds-Average Navier-Stokes (RANS), K- ε turbulence model. Thedefault domain is air at 240C. The inlet boundary condition used is ‘normal speed’ at 9 m/s,since the actual turbulence data at inlet is currently unavailable, for the present simulation theuniform turbulence intensity of 5% (medium intensity) is used to model the inlet turbulence.The outlet condition is assigned to the extended domain walls as average static pressure of 0gauge magnitude. The computational platform is HP- Pavilion dv6, with Intel CORE i32.4GHz processor, 8GB of RAM. The convergence target set at 1e-4 RMS; with continuitytarget error is 1e-4 kg/s. The convergence target achieved after 167 iterations.RESULTS AND DISCUSSIONFigure 5 shows the velocity profile at the plane when a person is passing through the aircurtain. The image of humanoid is clearly distinguishable in the door way. From the Figure 7it is clear that the smooth flow of air curtain is totally disturbed because of presence of theobstacle. The smooth layers of velocities are no more seen as observed in the velocity profilewithout obstacle. In the range 0.3 m from the top the velocity changes from 9 m/s to 6.3 m/swithout any pattern. The effect of midsection is also clearly visible in the Figure 7. Thevelocities in this area are slightly improved to the range 4.50 m/s to 5.40 m/s. The no velocityor low velocity (0 m/s to 0.76 m/s) zone which was observed up to 0.3 m is reduced to 0.1 m 512
  • 3. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –6340(Print), ISSN 0976 – 6359(Online) Volume 3, Issue 3, Sep- Dec (2012) © IAEMEbecause of presence of the obstacle which is positive effect on air curtain performance. Theflow in the range of 3.65 m/s to 6.38 m/s is observed around the humanoid. The flow of 6.38m/s to 8.21 m/s is also noticed on the side of the ‘head’ and ‘shoulder’ of the humanoid. Thebottom velocities are found improved with presence of obstacle. The velocities near groundare now in the range of 2.70 m/s to 3.65 m/s against the range observed of 0.9 m/s to 1.8 m/swithout obstacle. The stagnation effect is observed at the top of obstacle in very small area.The areas of concern with regards to flow of air curtain with obstacle are the areas below thehand and legs of the obstacle. The velocity in the 0.0 m/s to 0.9 m/s range is observed in thissection. This shows no air curtain or very weak air curtain. Every time a person passesthrough the air curtain the air curtain will become weak in this section and will lose itspurpose. The infiltration between inside and outside environments will not be effectivelyblocked by these low velocity sections resulting in reduction in effectiveness of air curtain.Figure 1 Experimental set up (Photograph) Figure 3 meshing Details Figure 2 Geometry Model with obstacle Figure 4 Validation of the model 513
  • 4. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –6340(Print), ISSN 0976 – 6359(Online) Volume 3, Issue 3, Sep- Dec (2012) © IAEME Figure 5 Velocity Profile at plane 1 with obstacle Figure 7 Velocity Profile at plane 3 with obstacle Figure 6 Velocity Profile at plane 2 with Figure 8 Velocity Profile at plane 2 and plane 3 above obstacle obstacle Figure 9 Location of midsection. 514
  • 5. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –6340(Print), ISSN 0976 – 6359(Online) Volume 3, Issue 3, Sep- Dec (2012) © IAEMEFigure 8 reveals the details of the velocity profile at plane 2 and plane 3. As plane 2 and plane3 passes through the midsection where there is no input of air and slit where direct air entersin the door way respectively. The velocities are accordingly found to be lowest and highest inthe region respectively. The red area represents the highest velocity at plane 3 over the top ofobstacle whereas maximum velocity recorded over the top of obstacle at plane passingthrough midsection ( plane 2) is found in the range 3.21 m/s to 3.81 m/s as compare tomaximum velocity (input velocity) of 9 m/s.Figure 6 and Figure 6 shows the velocity profile at the door way when obstacle is introducedin the door way. As shown in figure the smooth profile obtained is clearly disturbed. TheVelocity profile at plane 2 shows much distorted pattern as compared to plane 3 because ofindirect flow. The velocities are found increasing at distance of 1.3 m from the top because offlow movement of the air but at plane 3 very little effect was found at the back of obstaclenear the waist height region. As found at plane 1 no high velocity region was found near theobstacle at plane 2 and plane 3. The velocity near the obstacle was found decreasing ascompared to the surrounding in the range of 0 m/s to 0.6 m/s because of boundary layereffect. This is because the air curtain is perpendicular to plane 2 and plane 3, and width of aircurtain is small as compare to width of the obstacle.CONCLUSIONA numerical study of flow of air curtain over door way with and without insertion of humanshape obstacle was performed using CFD code Ansys CFX 13.0. The study found the modelis in good agreement with the experimental results. The flow over the air curtain wasobserved continuous, straight and without break, as per requirement of the air curtain. Thestudy reveals that the midsection area has large influence over velocity profile of the aircurtain. A good high velocity flow was observed below midsection when obstacle isintroduced. But when obstacle is introduced the low velocity regions were observed belowhands and between legs of the human shape obstacle which leads to mixing of air betweentwo environments thereby weakening air curtain effect.REFERENCE[1] Zhikun Cao Hua Han, Bo Gu, ‘A novel optimization strategy for the design of air curtains for open vertical refrigerated display cases.’ Applied Thermal Science Engineering, Volume 31, issue 16, November 2011 pp. 3098[2] Tassou, S. A. and Pappas, T. C., “Numerical Investigations into the Performance of Doorway Vertical Air Curtains in Air-Conditioned Spaces”, ASHRAE Transactions, Vol. 109, No. 1, 2003, pp. 273–279.[3] Homayun K Navaz, Dabiri, D. & R. Faramarzi, M Gharib, D Modarress,’The application of Advanced methods in analysing the performance of the air curtain in a refrigerated display case’, Journal of fluid Engineering, September 2002,Vol. 124, pp. 756.[4] Julian E Jaramillo, Carles D Perez-Segarra, Orial Lehmkuhl, Assensi Oliva, ‘Detail Numerical study of Turbulent flows in air curtain’, V European Conference on Computational Fluid Dynamics, ECCOMAS CFD 2010, Lisbon Portugal,[5] Enrico Nino, Rocco Fasanella, Rocco. Mario Di Tommaso, ‘Characterisation of a two dimensional air curtain’, Journal of Engineering and Technology,2010. Pp 902 515
  • 6. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 –6340(Print), ISSN 0976 – 6359(Online) Volume 3, Issue 3, Sep- Dec (2012) © IAEME[6] Brandon S Field and Erich Loth, ‘An air curtain along a wall with high inlet turbulence’, Journal of Fluid Engineering, May 2004 pp 126.[7] Frank K. Lu, Vijay A. Chauhan, Adam J Pierce, Takayuki Yajin and J Craig Dutton, ‘Numerical model of doorway flow induced by an air curtain’, Vol 35, 2009, pp 9, American Institute of Aeronautics and Astronautics.[8] Dr. Homayun K. Nawaz, Dr. Dana Dabiri Mazyar Amin and Ramin Faramarzi, ‘Past, Present and future Research towards air curtain performance optimisation’, OR-05- 16-4.[9] Durbin, P.A. and Pittersson Reif, B.A, Stastistical Theory and modelling for Turbulent flows, Wiley, New York 2001.[10] Samir R Traboulsi, Ali Hammoud, M Farid Khalil, ‘Air cirtain Integrity when Misusing the Refrigerated Display Cabinets’, ISSN 1790-5087 issue 2, Volume 4, April 2009[11] Pedro Dinis Gaspar, L.C. Carriho Goncalves and R A Pitarma, ’Three dimensional CFD modelling and analysis of the thermal entrainment in the open refrigerated display cabinets’, ASME Journal 2008.[12] ‘Appropriate indoor climate for environmentally sustainable Supermarket, measurements and Questionnaires Air curtain manual’, Thermozone Technology,2003. 516

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