Performance and flow characteristics of floor swirl diffuser under differ

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Performance and flow characteristics of floor swirl diffuser under differ

  1. 1. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 4, July - August (2013) © IAEME 154 PERFORMANCE AND FLOW CHARACTERISTICS OF FLOOR SWIRL DIFFUSER UNDER DIFFERENT OPERATING AND FLOW PARAMETERS 1 Suraj, 2 Dr. V.N. Bartaria 1 Suraj, ME Scholar, LNCT, Bhopal 2 Dr. V.N. Bartaria, Prof. & Head, LNCT, Bhopal ABSTRACT Floor swirl diffusers used in air-conditioning system can create better air mixing to enhance indoor air quality and help in achieving better human comfort. The variation in temperature in air conditioning system depends strongly on the flow characteristics produced by the diffuser outlet that vary considerably between different modeling set ups. In corporate sector it is very important to calculate the effect of variation in temperature of diffused air from floor swirl diffuser with and without heat load. In this experimental work, I have tried to reduce the variation in temperature of conditioned air and improvement in thermal human comfort by adopting different models of floor swirl diffuser designed on pro-E software. After that I have made prototype wooden model of the floor swirl diffuser to check its performance under different operating and flow conditions experimentally. The experiment has been performed inside an acrylic sheet wooden room of size 4ft x 4ft x 5ft with floor swirl diffuser models installed at the roof. The variation in temperature of diffused air form floor swirl diffuser at different altitude and the effect of heat load on temperature variation is determined. This experiment has been performed on three different models of floor swirl diffuser having different slot angles of 7⁰, 8⁰ and 9⁰. Keywords: ACE-Air Change Effectiveness, Heat Load Capacity, Swirl motion, 7⁰ Swirl Diffuser- Diffuser having slot with draft angle 7⁰, 8⁰ Swirl Diffuser- Diffuser having slot with draft angle 8⁰, 9⁰ Swirl Diffuser- Diffuser having slot with draft angle 9⁰,and Round and rectangular slots, Cross- section. INTERNATIONAL JOURNAL OF MECHANICAL ENGINEERING AND TECHNOLOGY (IJMET) ISSN 0976 – 6340 (Print) ISSN 0976 – 6359 (Online) Volume 4, Issue 4, July - August (2013), pp. 154-165 © IAEME: www.iaeme.com/ijmet.asp Journal Impact Factor (2013): 5.7731 (Calculated by GISI) www.jifactor.com IJMET © I A E M E
  2. 2. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 4, July - August (2013) © IAEME 155 INTRODUCTION Floor air diffusers are used widely in air-conditioning systems for distribution of conditioned air inside a room and the air diffusion is very much depends on the characteristics of different diffuser designs. For floor-level air supply systems, swirling diffusers are most widely used. Modeling of the diffuser plays an important role in predicting airflow pattern in the room. Swirl diffusers are generally mounted into the underfloor air handling space. This device delivers conditioned air at floor level to the space and allows the occupant to manually control both the volume and direction of the air flow. The diffuser is constructed of a durable, high impact, polycarbonate material. Delivering air from the floor has an advantage of supplying fresh, cool, clean air directly into the occupied zone of the space, so heat and pollutants are not continuously circulated within the space as it happens in an overhead air distribution system. It will results in dissipation of heat and less concentration of pollutants in the occupied space in the lower level than those at the upper levels of the space. Ventilation is done through displacement as opposed to dilution. The requirement of a good air distribution system is to supply clean and fresh air with less variation in temperature with height and different locations to provide thermal comfort and high air quality. In Asian and European countries, 30-50% of occupants have health problem because of bad air distribution system. Almost 30-40% of the energy produced has been spent on air distribution system in most of the developing countries. Swirl diffusers are designed to provide effective indoor air diffusion through specially designed swirl deflection blades to produce a highly turbulent radial air flow pattern that will induce better mixing of room air. This also results in rapid temperature equalization to give stable room conditions with minimum temperature gradients. The excellent high qualities of air from swirl diffusers enable designers to aim for a high value of Air Change Effectiveness (ACE). Swirl diffusers have recently become very popular because they generate radially high induction swirl air flow by drawing room air up into the supply air pattern to induce superior air mixing. Better mixing means better ACE. It is therefore required to study the characteristics of air distribution system with floor swirl diffuser under different operating and flow conditions with high thermal load. EXPERIMENTAL SET-UP It consists of an acrylic sheet wooden room of size 4ft x 4ft x 5ft with different models of swirl diffuser installed at the floor level. The conditioned air from air conditioner is supplied from the bottom through a duct of reducing cross-section to increase the air flow velocity through the diffuser. A heater of 1500W is placed inside the room to provide a heat load. Heater is placed near the location Y2. A temperature sensing instrument with six thermocouple wires is placed inside the room to measure the temperature at six locations vertically at a distance of 0.7 feet. There are four exhaust vents at the top surface of the wooden block through which ventilation is carried out inside the room. There are six locations at the floor inside the room where readings of temperature have to be noted and the variation in temperature of air is to be studied. 3-D view of the experimental set-up and actual front view of the experimental set-up is shown in Fig.1 and Fig.2 respectively.
  3. 3. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 4, July - August (2013) © IAEME 156 Fig.1 3-D view of the experimental set-up Fig.2 Front view of the experimental set-up DIFFERENT MODELS OF DIFFUSER 1. 7⁰ Swirl Diffuser It has a circular cross-section of 280mm diameter and height 280mm. Round slots are cut on the top surface. Round slots are drafted through an angle of 7⁰ for producing swirl action. Width of the top surface is 10mm. Vertical surface of the diffuser is cylindrical with rectangular slots of size 10mm x 200 mm are cut on its surface. Fig.3 Top view of 7⁰ Swirl Diffuser Fig.4 Front view of 7⁰ Swirl Diffuser
  4. 4. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 4, July - August (2013) © IAEME 157 2. 8⁰ Swirl Diffuser It has a circular cross-section of 280mm diameter and height 280mm. Round slots are cut on the top surface. Round slots are drafted through an angle of 8⁰ for producing swirl action. Width of the top surface is 10mm. Vertical surface of the diffuser is cylindrical with rectangular slots of size 10mm x 200 mm are cut on its surface. Fig.5 Top view of 8⁰ Swirl Diffuser Fig.6 Front view of 7⁰ Swirl Diffuser 3. 9⁰ Swirl Diffuser It has a circular cross-section of 280mm diameter and height 280mm. Round slots are cut on the top surface. Round slots are drafted through an angle of 9⁰ for producing swirl action. Width of the top surface is 10mm. Vertical surface of the diffuser is cylindrical with rectangular slots of size 10mm x 200 mm are cut on its surface. Fig.7 Top view of 9⁰ Swirl Diffuser Fig.8 Front view of 9⁰ Swirl Diffuser FLOW PATTERN OF AIR THROUGH DIFFERENT DIFFUSER The flow pattern of air through different diffusers can be visualized with the help of smoke. The smoke is created inside the diffuser chamber and it is accelerated through the diffuser by the conditioned air coming from the air- conditioner.
  5. 5. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 4, July - August (2013) © IAEME 158 Fig.9 Air flow pattern through 7⁰ Fig.10 Air flow pattern through 8⁰ Swirl Diffuser Swirl Diffuser Fig.11 Air flow pattern through 9⁰ Swirl Diffuser EXPERIMENTAL RESULTS The main results of the experiment are tabulated at six locations inside the room with and without heat load. Locations are taken along X-axis and Y-axis on the floor. These locations are equally spaced and are at a distance of 1 foot from each other. The supply air temperature from the air-conditioner is 18.4⁰C at a flow rate of 0.2m3 /s. The heat load is applied inside the room with the help of heater of load capacity 1500W. Various temperature readings are noted at location Y1, Y2, Y3, X1, X2 and X3 with load and without load. The experiment has been performed with all three models of diffuser. These experimental results will help us in comparing the performance of three different models of floor swirl diffuser under different operating and flow conditions. These results have been plotted graphically between temperature and height from the floor level. It will also provide the designers a guideline in achieving better human comfort and best performance with floor swirl diffuser used in air conditioning system. The graphs plotted between temperature and height at various locations indicates that variation in temperature with height is less with 8⁰ swirl diffuser. The result also shows that variation in temperature reduces as we move away from the heat source. Due to swirl action produced by the
  6. 6. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 4, July - August (2013) © IAEME 159 diffuser temperature equalization is almost achieved inside the room at different locations with and without heat load. During the experiment performance only one exhaust vent is opened out of the four. We can also perform the same experiment with all the four vents are opened. The variation in temperature at location Y1, Y2 and Y3 is comparatively more than at location X1, X2 and X3 during presence of heat load. This happens due to presence of heat source at location Y2. AIR TEMPERATURE MEASUREMENT Air temperature is measured spontaneously at each location under different operating conditions. Inlet and return air temperature are 18.4⁰C and 23.6⁰C for 7⁰ swirl diffuser, 18.4⁰C and 22.4⁰C for 8⁰ swirl diffuser and 18.4⁰C and 23.8⁰C in case of 9⁰ swirl diffuser respectively. A uniform temperature distribution is observed. The highest temperature gradient is found at location Y2. In the upper occupied zone there is small temperature gradient due to good mixing of air in the upper region. The temperature at various locations is tabulated and the graphical results are shown below. Condition1: When exhaust vent 1 is opened Initial Room Temperature= 32⁰C Room Temperature at load 1500W without switching air-conditioner= 38⁰C At location Y1 Load= No load with a.c. S. No. Height (ft.) Temperature (⁰⁰⁰⁰C) 7⁰⁰⁰⁰ 8⁰⁰⁰⁰ 9⁰⁰⁰⁰ 1 0.7 24 23 25 2 1.4 24 23 23 3 2.1 23 21 21 4 2.8 24 22 23 5 3.5 23 21 24 6 4.2 22 20 22 At location Y1 Load= 1500W load with a.c. S. No. Height (ft.) Temperature (⁰⁰⁰⁰C ) 7⁰⁰⁰⁰ 8⁰⁰⁰⁰ 9⁰⁰⁰⁰ 1 0.7 26 25 24 2 1.4 25 25 23 3 2.1 25 24 23 4 2.8 25 25 25 5 3.5 23 25 25 6 4.2 22 22 23
  7. 7. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 4, July - August (2013) © IAEME 160 At location Y2 Load= No load with a.c. S. No. Height (ft.) Temperature (⁰⁰⁰⁰C) 7⁰⁰⁰⁰ 8⁰⁰⁰⁰ 9⁰⁰⁰⁰ 1 0.7 26 24 26 2 1.4 24 23 23 3 2.1 23 22 22 4 2.8 24 23 24 5 3.5 23 22 24 6 4.2 21 21 22 At location Y2 Load= 1500W load with a.c. S. No. Height (ft.) Temperature (⁰⁰⁰⁰C) 7⁰⁰⁰⁰ 8⁰⁰⁰⁰ 9⁰⁰⁰⁰ 1 0.7 30 28 31 2 1.4 28 28 29 3 2.1 26 26 25 4 2.8 25 26 26 5 3.5 24 25 25 6 4.2 22 22 22 At location Y3 Load= No load with a.c. S. No. Height (ft.) Temperature (⁰⁰⁰⁰C) 7⁰⁰⁰⁰ 8⁰⁰⁰⁰ 9⁰⁰⁰⁰ 1 0.7 24 23 26 2 1.4 23 23 22 3 2.1 22 22 20 4 2.8 23 23 23 5 3.5 23 23 23 6 4.2 21 22 21 At location Y3 Load= 1500W load with a.c. S. No. Height (ft.) Temperature (⁰⁰⁰⁰C) 7⁰⁰⁰⁰ 8⁰⁰⁰⁰ 9⁰⁰⁰⁰ 1 0.7 30 25 28 2 1.4 28 26 26 3 2.1 26 23 24 4 2.8 26 25 25 5 3.5 25 25 25 6 4.2 23 22 22
  8. 8. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 4, July - August (2013) © IAEME 161 At location X1 Load= No load with a.c. S. No. Height (ft.) Temperature (⁰⁰⁰⁰C) 7⁰⁰⁰⁰ 8⁰⁰⁰⁰ 9⁰⁰⁰⁰ 1 0.7 24 23 27 2 1.4 24 23 23 3 2.1 22 22 20 4 2.8 23 23 24 5 3.5 22 23 23 6 4.2 21 21 22 At location X1 Load= 1500W load with a.c. S. No. Height (ft.) Temperature (⁰⁰⁰⁰C) 7⁰⁰⁰⁰ 8⁰⁰⁰⁰ 9⁰⁰⁰⁰ 1 0.7 25 24 25 2 1.4 23 24 23 3 2.1 23 22 23 4 2.8 25 25 25 5 3.5 24 24 24 6 4.2 22 21 21 At location X2 Load= No load with a.c. S. No. Height (ft.) Temperature (⁰⁰⁰⁰C) 7⁰⁰⁰⁰ 8⁰⁰⁰⁰ 9⁰⁰⁰⁰ 1 0.7 24 23 26 2 1.4 22 23 22 3 2.1 21 22 20 4 2.8 23 22 24 5 3.5 22 22 24 6 4.2 19 20 21 At location X2 Load= 1500W load with a.c. S. No. Height (ft.) Temperature (⁰⁰⁰⁰C) 7⁰⁰⁰⁰ 8⁰⁰⁰⁰ 9⁰⁰⁰⁰ 1 0.7 24 25 25 2 1.4 23 25 23 3 2.1 22 23 23 4 2.8 23 25 24 5 3.5 22 24 24 6 4.2 20 21 21
  9. 9. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 4, July - August (2013) © IAEME 162 At location X3 Load= No load with a.c. S. No. Height (ft.) Temperature (⁰⁰⁰⁰C) 7⁰⁰⁰⁰ 8⁰⁰⁰⁰ 9⁰⁰⁰⁰ 1 0.7 24 22 24 2 1.4 22 22 23 3 2.1 22 21 22 4 2.8 22 21 24 5 3.5 23 22 24 6 4.2 21 21 22 At location X3 Load= 1500W load with a.c. S. No. Height (ft.) Temperature (⁰⁰⁰⁰C) 7⁰⁰⁰⁰ 8⁰⁰⁰⁰ 9⁰⁰⁰⁰ 1 0.7 24 24 24 2 1.4 24 24 23 3 2.1 23 24 23 4 2.8 23 23 24 5 3.5 24 24 24 6 4.2 22 23 23 GRAPHICAL REPRESENTATION OF RESULTS The following graph shows the variation in temperature with height at different locations in experimental set-up. Fig.12 Variation in temperature vs. height at Fig.13 Variation in temperature vs. height at location Y1 in condition 1 without load location Y1 in condition 1 with load 1500W
  10. 10. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 4, July - August (2013) © IAEME 163 Fig.14 Variation in temperature vs. height at Fig.15 Variation in temperature vs. height at location Y2 in condition 1 without load location Y2 in condition 1 with load 1500W Fig.16 Variation in temperature vs. height at Fig.17 Variation in temperature vs. height at location Y3 in condition 1 without load location Y3 in condition 1 with load 1500W Fig.18 Variation in temperature vs. height Fig.19 Variation in temperature vs. height at at location X1 in condition 1 without load location X1 in condition 1 with load 1500W
  11. 11. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 4, July - August (2013) © IAEME 164 Fig.20 Variation in temp. vs. height at Fig.21 Variation in temperature vs. height at location X2 in condition 1 without load location X2 in condition 1 with load 1500W Fig.22 Variation in temp. vs. height at Fig.23 Variation in temperature vs. height at location X3 in condition 1 without load location X3 in condition 1 with load 1500W CONCLUSIONS The results from this study show that a workshop with floor-supply displacement ventilation using swirl diffuser can improve indoor air quality because the contaminant concentration in the breathing zone is lower than that of mixing system. It helps us in comparing the performance of three different types of swirl diffuser under different operating and flow conditions. Due to swirl action produced more unidirectional flow was created, the slow recirculation at the occupant zone was eliminated for the floor-supply ventilation and the risk of cross contamination can be effectively reduced. The system with the swirl diffusers can provide a better comfort level than that with the perforated panels due to the mixing by the diffusers. This study helps in selecting optimum models for floor swirl diffuser under different operating conditions. We can improve the Air Change Effectiveness and human comfort by varying the slot design angle of diffuser. It will results in better mixing of air inside the room and the variation in temperature of air from floor height will be reduced. We can achieve better human comfort and proper ventilation by using floor swirl diffuser.
  12. 12. International Journal of Mechanical Engineering and Technology (IJMET), ISSN 0976 – 6340(Print), ISSN 0976 – 6359(Online) Volume 4, Issue 4, July - August (2013) © IAEME 165 REFERENCES [1] Xue, G., Lee, K., Jiang, Z. and Chen, Q. 2012. Thermal environment in indoor spaces with under-floor air distribution systems: 2. Determination of design parameters (RP-1522). Submitted to HVAC&R Research. [2] Allison, C. and North, B. 2011. Achieving Air- Change Effectiveness for Green Star IEQ-2 Office Design with CFD Simulations: Diffuser Performance, Ecolibrium, February 2011, pp. 28-34. [3] Lee, K.S., Zhang, T., Jiang, J., and Chen, Q. 2009. Comparison of airflow and contaminant distributions in rooms with traditional displacement ventilation and under-floor air distribution systems – RP-1373. ASHRAE Transactions 115 (2). [4] Bauman, F., Webster, T., and Benedict, C. 2007. Cooling airflow design calculations for UFAD. ASHRAE Journal 49(10): 36-44. [5] D.-W. Kim, H.-S. Kim, S.-K. Park and Y.-J. Kim, Analyses on Flow Fields and Performance of a Cross-Flow Fan with various Setting Angles of a Stabilizer (in Korean), J. of Comp. Fluids Engg., 10(1) (2005) 107-112. [6] Bauman FS. Designing and specifying underfloor systems: Shedding light on common myths. HPAC Heating, Piping, Air Conditioning Engineering 2003; 75(12):26–39. [7] Akimoto T. Research on floor-supply displacement air-conditioning system. PhD thesis, 1998, Waseda University, Japan [8] Chae Y, Moon H, Ahn B, Sohn J. Experimental comparison of characteristics between ceiling-based system and floor-based system using CAV HVAC system in cooling period. Proceedings of Indoor Air 2002:3–288. [9] Syed Moazzam Ali and Dr.Balu Naik Banoth, “Low Energy Consumption HVAC Systems for Green Buildings using Chilled Beam Technology”, International Journal of Advanced Research in Engineering & Technology (IJARET), Volume 4, Issue 3, 2013, pp. 316 - 324, ISSN Print: 0976-6480, ISSN Online: 0976-6499. [10] P. K. Sinha, A.K.das and B. Majumdar, “Numerical Investigation of Flow through Annular Curved Diffuser”, International Journal of Mechanical Engineering & Technology (IJMET), Volume 2, Issue 2, 2011, pp. 1 - 13, ISSN Print: 0976 – 6340, ISSN Online: 0976 – 6359.

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