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Measurements on Confluent Jets V entilation System Professor Bahram Moshfegh

Measurements on Confluent Jets V entilation System Professor Bahram Moshfegh Tech. lic Ulf Larsson Master students Julio J. Peña Malo and Igor Panjkov bahram.moshfegh@hig.se. Layout of the room.

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Measurements on Confluent Jets V entilation System Professor Bahram Moshfegh

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  1. Measurements on Confluent Jets Ventilation System Professor Bahram Moshfegh Tech. lic Ulf Larsson Master students Julio J. PeñaMalo and Igor Panjkov bahram.moshfegh@hig.se

  2. Layout of the room Cyan zone is the studied zone divided in 6 subzones. The representative points of each subzone are shown with a small circle.In purple, the equipment inside the room.In red and blue, flow air directions. Yellow point is the temperature measure points at two different positions. The temperatures have been measured starting at 0.1 m from the floor. After the first point, each 20 cm for 10 times.

  3. Case studies

  4. Local mean age and Air change efficiencyConfluent jets ventilation system (device at 2.2 m height)

  5. Local mean age and Air change efficiencyConfluent jets ventilation system (device at 1.7 m height)

  6. Local mean age and Air change efficiencyDisplacement ventilation system

  7. Local mean age and Air change efficiencyMixing ventilation system

  8. Analysis of the local mean age and air change efficiency Air change efficiency: Confluent jets ventilation system with the device at 2.2 m gets the best results (50-52%) followed by displacement (50%) and the last one mixing ventilation system (47%). Confluent system with the device at 1.7 m obtains similar results than mixing ventilation system in terms of air change efficiency. Local mean age: the system which more approximate to the theory values are confluent ventilation in any of the two heights (better at 2.2 m height). After confluent, the second best results come from displacement, and mixing is the system which obtains the farthest results in comparison with the theory results.

  9. Temperature gradient Confluent jets ventilation system Device at 1.7 m height Device at 2.2 m height

  10. Temperature gradient Displacement and Mixing ventilation system Displacement Mixing

  11. Analysis of the temperature gradient Mixing ventilation system: the temperature diagram looks like a vertical line. This is due to the homogeneous mix that are inside the office room for the mixing ventilation system. Displacement ventilation system: at the low level the temperature is lower than in the middle and in the top level. This is due to the displacement ventilation system performance which makes supply air pass through the floor firstly and then the air goes up towards the top part of the room. Confluent jets ventilation system: with the device at 1.7 m and 2.2 m, the temperature gradient is like a mix between displacement ventilation and mixing ventilation.

  12. Temperature gradient Comparison between CJV, DV and MV Average air temperature in the occupied zone: Table above shows the influence of the supply air device on the mean air temperature in the occupied zone. Confluent jets ventilation system provides 0.2oC lower air temperature in the occupied zone compared to the displacement ventilation. Comparison between confluent jets ventilation system and the mixing ventilation shows quite considerable difference. The differences varies between 0.5oC to 2.4oC. Thus, the Confluent jets ventilation systems provides better cooling in the room at the same supply air temperature and flow rate.

  13. Cooling PerformanceComparison between CJV and MV Texhaust = Measured exhaust temperature (C) DT = Texhaust–Tsupply Pcooling = Measured exhaust temperature (C) Cooling Performance: CF = (Pcooling)MV/(Pcooling)CVJ Cooling Performance (CP):Table above shows the cooling performance of the Confluent jets ventilation system (CJV) and the Mixing ventilation (MV). The results reveal that for the studied cases the CJV has a higher cooling performance which varies between 105% to 142%. In other words the CJV has a higher cooling capacity compared to the MV.

  14. Thermal comfort (PMV)Confluent jets ventilation system (device at 1.7 m height) Case 1 Case 4 Case 7

  15. Thermal comfort (PMV)Confluent jets ventilation system (device at 1.7 m height) Height 0.1 m Height 1.1 m Height 1.7 m

  16. Thermal comfort (PPD)Confluent jets ventilation system (device at 1.7 m height) Case 1 Case 4 Case 7

  17. Thermal comfort (PPD)Confluent jets ventilation system (device at 1.7 m height) Height 0.1 m Height 1.1 m Height 1.7 m

  18. Thermal comfort (PMV)Confluent jets ventilation system (device at 2.2 m height) Case 1 Case 2 Case 3

  19. Thermal comfort (PMV)Confluent jets ventilation system (device at 2.2 m height) Case 4 Case 6 Case 7

  20. Thermal comfort (PMV)Confluent jets ventilation system (device at 2.2 m height) Height 0.1 m Height 1.1 m Height 1.7 m

  21. Thermal comfort (PPD)Confluent jets ventilation system (device at 2.2 m height) Case 1 Case 2 Case 3

  22. Thermal comfort (PPD)Confluent jets ventilation system (device at 2.2 m height) Case 4 Case 6 Case 7

  23. Thermal comfort (PPD)Confluent jets ventilation system (device at 2.2 m height) Height 0.1 m Height 1.1 m Height 1.7 m

  24. Thermal comfort (PMV)Displacement ventilation system Case 8 Case 9 Case 10

  25. Thermal comfort (PMV)Displacement ventilation system Height 0.1 m Height 1.1 m Height 1.7 m

  26. Thermal comfort (PPD)Displacement ventilation system Case 8 Case 9 Case 10

  27. Thermal comfort (PPD)Displacement ventilation system Height 0.1 m Height 1.1 m Height 1.7 m

  28. Thermal comfort (PMV)Mixing ventilation system Case 11 Case 12 Case 13

  29. Thermal comfort (PMV)Mixing ventilation system Height 0.1 m Height 1.1 m Height 1.7 m

  30. Thermal comfort (PPD)Mixing ventilation system Case 11 Case 12 Case 13

  31. Thermal comfort (PPD)Mixing ventilation system Height 0.1 m Height 1.1 m Height 1.7 m

  32. Analysis of the thermal comfort PMV and PPD • Confluent jets ventilation system with the device at 2.2 m gets better PMV value for Case 1 and Case 4 compared with the device at 1.7 m. • However, for the Case 7 the device at 1.7 m has better PMC value compared to the device at 2.2 m. • Confluent jets ventilation system has better PMV value for the studied cases followed by displacement and the last one is the mixing ventilation system. People would be more satisfied with the Confluent jets ventilation system • Confluent jets ventilation system with the device at 2.2 m has better PMV value with the height 0.1 m from the floor compared with the device at 1.7 m. For the other heights the results are quite similar. • Confluent jets ventilation system has better PMV value for all heights i.e. 0.1 m, 1.1 m and 1.7 m followed by the displacement and the last one is the mixing ventilation system. • The same conclusions could be drawn for the PPD value. Confluent jets ventilation system has the best values for the PPD value for all cases as well as at the different heights.

  33. Final Conclusions • CJV provides the most comfortable air temperature in the occupied zone compared to the DV and MV. • CJV has a higher cooling performance compared to the MV, which varies between 105% to 142% for the studied cases. • CJV gets the best air change efficiency (52%) followed by the DV (50%) and the last one MV (47%). • CJV has better PMV and PPD values for the studied cases followed by the DV and the last one is the MV system. People would be more satisfied with the CJV. • CJV has better PMV and PPD values for all heights i.e. 0.1 m, 1.1 m and 1.7 m followed by the DV and the last one is the MV.

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