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  • 1.
    Ameen, Arman
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Cehlin, Mathias
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Larsson, Ulf
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Karimipanah, Taghi
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Experimental Investigation of Ventilation Performance of Different Air Distribution Systems in an Office Environment: Heating Mode2019In: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 12, no 10, article id 1835Article in journal (Refereed)
    Abstract [en]

    A vital requirement for all-air ventilation systems are their functionality to operate both in cooling and heating mode. This article experimentally investigates two newly designed air distribution systems, corner impinging jet (CIJV) and hybrid displacement ventilation (HDV) in comparison against a mixing type air distribution system. These three different systems are examined and compared to one another to evaluate their performance based on local thermal comfort and ventilation effectiveness when operating in heating mode. The evaluated test room is an office environment with two workstations. One of the office walls, which has three windows, faces a cold climate chamber. The results show that CIJV and HDV perform similar to a mixing ventilation in terms of ventilation effectiveness close to the workstations. As for local thermal comfort evaluation, the results show a small advantage for CIJV in the occupied zone. Comparing C2-CIJV to C2-CMV the average draught rate (DR) in the occupied zone is 0.3% for C2-CIJV and 5.3% for C2-CMV with the highest difference reaching as high as 10% at the height of 1.7 m. The results indicate that these systems can perform as well as mixing ventilation when used in offices that require moderate heating. The results also show that downdraught from the windows greatly impacts on the overall airflow and temperature pattern in the room.

  • 2.
    Ameen, Arman
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Cehlin, Mathias
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Larsson, Ulf
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Karimipanah, Taghi
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Experimental investigation of ventilation performance of different air distribution systems in an office environment – cooling mode2019In: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 12, no 7, article id 1354Article in journal (Refereed)
    Abstract [en]

    The performance of a newly designed corner impinging jet air distribution method with an equilateral triangle cross section was evaluated experimentally and compared to that of two more traditional methods (mixing and displacement ventilation). At nine evenly chosen positions with four standard vertical points, air velocity, turbulence intensity, temperature, and tracer gas decay measurements were conducted for all systems. The results show that the new method behaves as a displacement ventilation system, with high air change effectiveness and stratified flow pattern and temperature field. Both local air change effectiveness and air exchange effectiveness of the corner impinging jet showed high quality and promising results, which is a good indicator of ventilation effectiveness. The results also indicate that there is a possibility to slightly lower the airflow rates for the new air distribution system, while still meeting the requirements for thermal comfort and indoor air quality, thereby reducing fan energy usage. The draught rate was also lower for corner impinging jet compared to the other tested air distribution methods. The findings of this research show that the corner impinging jet method can be used for office ventilation.

  • 3.
    Arghand, Taha
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Karimipanah, Taghi
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Awbi, Hazim
    School of Construction Management and Engineering, University of Reading, United Kingdom.
    Cehlin, Mathias
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Larsson, Ulf
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Linden, Elisabet
    University of Gävle, Faculty of Engineering and Sustainable Development, BMG laboratory.
    An experimental investigation of the flow and comfort parameters for under-floor, confluent jets and mixing ventilation systems in an open-plan office2015In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 92, p. 48-60Article in journal (Refereed)
    Abstract [en]

    There is a new trend to convert the workplaces from individual office rooms to open offices for motivating money saving and better communication. With such a shift the ability of existing ventilation systems in meeting the new requirements is a challenging question for researchers. The available options could have an impact on workers' health in terms of providing acceptable levels of thermalcomfort and indoor air quality. Thus, this experimental investigation focuses on the performances of three different air distribution systems in an open-plan office space. The investigated systems were: mixing ventilation with ceiling-mounted inlets, confluent jets ventilation and underfloor air distribution with straight and curved vanes. Although this represents a small part of our more extensiveexperimental investigation, the results show that all the purposed stratified ventilation systems (CJV and UFAD) were more or less behaving as mixing systems with some tendency for displacement effects. Nevertheless, it is known that the mixing systems have a stable flow pattern but has the disadvantage of mixing contaminated air with the fresh supplied air which may produce lower performance and in worst cases occupants' illness. For the open-plan office we studied here, it will be shown that the new systems are capable of performing better than the conventional mixing systems. As expected, the higher air exchange efficiency in combination with lower local mean age of air for corner-mounted CJV and floor-mounted UFAD grills systems indicates that these systems are suitable for open-plan offices and are to be favored over conventional mixing systems.

  • 4.
    Cehlin, Mathias
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Karimipanah, Taghi
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Prediction of indoor airflow close to a supply device using SST-SAS Model2015In: Ventilation 2015 - Proceedings of the 11th International Conference on Industrial Ventilation / [ed] Taipale A., Li Z., Li X., and Zhang X, International Conference on Industrial Ventilation , 2015, Vol. 2, p. 681-688Conference paper (Refereed)
    Abstract [en]

    Modern diffusers applied in the field of ventilation of rooms are often complex in terms of geometry, including perforated plates, dampers, guide rails, curved surfaces and other components inside the diffuser, with the intention to create satisfying thermal comfort for the occupants. Also connecting ducts can be different for the same diffuser in different situations, affecting the supply velocity profile. It is obvious that simulation of airflow and air temperature particularly in rooms with displacement ventilation is very troublesome, particularly if the near-zone of the diffuser is of interest. Experiments commonly indicate very high turbulence intensities in the near-zone of displacement ventilation supply devices, especially close to the floor where high mean flow gradient occurs. This indicates that the air flow from inlet devices designed for displacement ventilation might be very unsteady; the position of the stream leaving the diffuser and entering the room is changing with time, hence diffusion of momentum and temperature are increased. Also Kelvin-Helmholtz instabilities occurs, resulting in mixing and entrainment of surrounding air into the gravity current. These effects are not captured correctly in RANS simulations, since it is performed with the assumption of time-independent conditions. In this paper URANS simulations were performed for prediction of velocity and temperature distribution close to a complex air supply device in a room with displacement ventilation. The presented study show that URANS with the SST-SAS ᅵᅵ - ᅵᅵ turbulence model predicts the air velocities and air temperatures very well close to the air supply device. The URANS computation using the SST-SAS model seems to successfully contribute to the reproduction of large-scale unsteady flow patterns in the near-zone of the supply device, and therefore enable more accurate prediction of the velocity and temperature distributions compared to the steady-RANS computation and dissipative URANS models.

  • 5.
    Cehlin, Mathias
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Karimipanah, Taghi
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Larsson, Ulf
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Unsteady CFD simulations for prediction of airflow close to a supply device for displacement ventilation2014In: Indoor Air 2014 - 13th International Conference on Indoor Air Quality and Climate, 2014, p. 47-54Conference paper (Refereed)
    Abstract [en]

    Modern diffusers applied in the field of ventilation of rooms are often complex in terms of geometry, including perforated plates, dampers, guide rails, curved surfaces and other components inside the diffuser, with the intention to create satisfying thermal comfort for the occupants. Also connecting ducts can be different for the same diffuser in different situations, affecting the supply velocity profile. It is obvious that simulation of airflow and air temperature particularly in rooms with displacement ventilation is very troublesome, particularly if the near-zone of the diffuser is of interest. Experiments commonly indicate very high turbulence intensities in the near-zone of displacement ventilation supply devices, especially close to the floor where high mean flow gradient occurs. This indicates that the air flow from inlet devices designed for displacement ventilation might be very unstable; the position of the stream leaving the diffuser and entering the room is changing with time, hence diffusion of momentum and temperature are increased. This effect is not captured in RANS simulations, since it is performed with the assumption of time-independent conditions. In this paper URANS simulations were performed for prediction of velocity and temperature distribution close to a complex air supply device in a room with displacement ventilation. The presented study show that unsteady simulations with the realizable turbulence k-ε model generates too high eddy viscosity and therefore damps out the unsteadiness of the flow especially inside the diffuser.

  • 6.
    Cehlin, Mathias
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Karimipanah, Taghi
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Larsson, Ulf
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Ameen, Arman
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Comparing thermal comfort and air quality performance of two active chilled beam systems in an open-plan office2019In: Journal of Building Engineering, E-ISSN 2352-7102, Vol. 22, p. 56-65Article in journal (Refereed)
    Abstract [en]

    The traditional air distribution and supply devices in ventilated rooms are not always able to effectively remove excess heat from the space. Therefore, chilled beams, especially the active systems, are used to achieve the desired cooling demand. The focus of this paper was the potential benefit of a newly designed active chilled beam (ACB) system, to improve heat removal effectiveness local thermal condition and indoor air quality in the occupants’ breathing zone. The system based on 1-way flow design (1W-ACB) was installed in an open-plan office and its performance was studied by analysing the temperatures, velocities and tracer gas concentrations in predetermined risky zones. The system was compared against a traditional 4-way flow design (4W-ACB).

    The obtained results showed that heat removal effectiveness was slightly higher for the 1W-ACB system compared to the 4W-ACB system. The local thermal condition was very good close to the workstations when using 1W-ACB. The benefits of the new system were also shown in the occupied zone by analysing the mean age of air and air-change effectiveness (ACE) in the breathing level at the workstation locations. The 1W-ACB system provided air with lower mean age (fresher air), and therefore higher ACE, near the breathing zone at the workstations compared to the 4W-ACB. On the other hand, the 4W-ACB system had the advantage of providing high thermal and mean age of air uniformity throughout the room.

  • 7.
    Cho, Y J
    et al.
    The University of Reading, UK.
    Awbi, Hazim B.
    University of Reading, UK.
    Karimipanah, Taghi
    Fresh AB, Sweden.
    The characteristics of wall confluent jets for ventilated enclosures2004Conference paper (Refereed)
  • 8.
    Cho, Y-J
    et al.
    University of Reading.
    Awbi, Hazim
    University of Reading.
    Karimipanah, Taghi
    Fresh AB, Sweden.
    Theoretical and experimental investigation of wall confluent jets ventilation and comparison with wall displacement ventilation2008In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 43, no 6, p. 1091-1100Article in journal (Refereed)
    Abstract [en]

    This paper reports CFD and experimental results of the characteristics of wall confluent jets in a room. The results presented show the behaviour of wall confluent jets in the form of velocity profiles, the spreading rate of jets on the surface, jets decay, etc. The empirical equations derived are compared with other types of air jets. In addition, the flow in wall confluent jets is compared with the flow in displacement ventilation supply, with regards to the vertical and horizontal spreading on the floor. It is concluded that the jet momentum of wall confluent jets can be more conserved than other jets. Thus, wall confluent jets have a greater spread over the floor than displacement flow. (C) 2007 Elsevier Ltd. All rights reserved.

  • 9. Cho, Youngjun
    et al.
    Awbi, Hazim B.
    University of Reading, UK.
    Karimipanah, Taghi
    Comparison between wall confluent jets and displacement ventilation in aspect of the spreading rate on the floor2005In: Indoor Air 2005 : proceedings of the 10th International Conference on Indoor Air Quality and Climate, 2005Conference paper (Refereed)
  • 10.
    Karimipanah, Taghi
    Centre for Built Environment, Royal Institute of Technology, Gävle, Sweden .
    Deflection of wall-jets in ventilated enclosures described by pressure distribution1998In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 34, no 3, p. 329-333Article in journal (Refereed)
    Abstract [en]

    The pressure field in fluid systems reflects the flow configuration. Measurements of the pressure along the perimeter of a slot ventilated room have been conducted for different room sizes. The momentum of the jet at the end of the room is decreased with increasing room length. The impingement region (region where the influence of the opposing wall is present) starts, independent of room size, when the distance from the supply device is about 70% of the room length. Corner flows could not be predicted by CFD using the linear eddy viscosity or standard stress models. However, these effects may be captured by using a second moment closure turbulence model with a new near wall approach now available in literature.

  • 11.
    Karimipanah, Taghi
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering. Faculty of Engineering and Sustainable Development.
    Environmental analysis of cars1988Report (Other academic)
  • 12.
    Karimipanah, Taghi
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering.
    Jet momentum flux: Determination based on the weighing of air issuing from a supply device2000Report (Refereed)
  • 13.
    Karimipanah, Taghi
    University of Gävle, Department of Technology and Built Environment.
    Jet momentum flux: Determination based on the weighing of air issuing from a supply device2000Report (Refereed)
  • 14.
    Karimipanah, Taghi
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering.
    Turbulent jets in confined spaces: application in mixing ventilation: experimental and numerical studies1996Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The basis of mixing ventilation is the airflow supply to the room by means of jets initiatedfrom the ventilation diffusers. To avoid the draught problem, the design of mixing ventilationmakes uses the throw term, which is defined as the distance to the supply air terminal inwhich the jet centreline mean velocity is decreased to a given value. Traditionally, the throw ismeasured by the supply air device manufacturer. The throw is applied by designers to estimatethe velocity levels in the occupied zone. A standard for determining the throw is the CENstandard CEN/TC156/WG4 N86 "Draft Standard. Air terminal Devices. AerodynamicsTesting And Rating For Mixed Flow Application".The measurement of the throw is very time consuming even with the free jets and theinfluence of the room (the effect of confinement) is not considered. The objective of thepresent study is to give a basis for modifying the existing design and testing method used topredict the velocities in the occupied zone during the design process. A new method whichmay probably be more easier than the existing methods and at the same time give a betterprecision by including the confinement effect.In this thesis two methodological systems of experiment and numerical simulations have beenused. The numerical predictions are used in comparison with the measurements. Thereasonable agreement of the above mentioned methods is implemented to numerical study ofthe other room configurations which are not experimentally studied. This examining methodallows the possibility of studying a lot of configurations and in this manner generalising of theresults. Although the experimental part was made for both model-scale and full-scale testrooms, a large amount of data was obtained for a new test room whose dimension aresystematically varied. All of studies have been made for the isothermal case and themeasurements of velocities and pressures conducted along the room perimeters. The effect ofshort and deep rooms on the properties of the jet ( velocities, pressure, integral scale, jetmomentum, the rate of spreading of jet and turbulence intensities) have been carried out.Some old and recent investigations have been examined. Specially the concept of correlationsfrom open to closed rooms is criticised. It is also shown that the flow field in a confined roomis affected by many other factors than the Reynolds number. The surface pressure on theperimeters was used to calculate the reaction forces at the corners which causes recirculatingbubbles at corners. A study of the turbulent axisymmetric jet which is the basic element inturbulent shear flows and some restrictions of the traditional measurement techniques at theregion of interest in ventilation applications are discussed. The jet momentum is measured byweighing on a balance. Also a study of jets which collide with a wall , that is impinging jet,the effect of walls and confinement on the jet momentum have experimentally andnumerically been carried out. A new momentum balance model was developed for both thefree jet and confined one. An empirical relation has been found for estimation of the room’srotation centre which is used for validation of CFD results.Finally, it is found that the jets in a ventilated room which are a combination of free jet, walljet and impinging jet differ from the traditional wall jets. The rate of spreading of the jet andthe maximum velocity decay in a ventilated room are also different depending on the roomsize and its confinement.

  • 15.
    Karimipanah, Taghi
    et al.
    Air Innovation AB, Sweden .
    Awbi, Hazim
    Indoor Environment and Energy Research Group, Department of Construction Management and Engineering, University of Reading, Reading RG6 6AW, United Kingdom .
    Theoretical and experimental investigation of impinging jet ventilation and comparison with wall displacement ventilation2002In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 37, no 12, p. 1329-1342Article in journal (Refereed)
    Abstract [en]

    This paper focuses on evaluating the performance of a new impinging jet ventilation system and compares its performance with a wall displacement ventilation system. Experimental data for an impinging jet in a room are presented and non-dimensional expressions for the decay of maximum velocity over the floor are derived. In addition, the ventilation efficiency, local mean age of air and other characteristic parameters were experimentally and numerically obtained for a mock-up classroom ventilated with the two systems. The internal heat loads from 25 person-simulators and lighting were used in the measurements and simulations to provide a severe test for the two types of ventilation systems. In addition to a large number of experimental data CFD simulations were used to study certain parameters in more detail. The results presented here are part of a larger research programme to develop alternative and efficient systems for room ventilation.

  • 16.
    Karimipanah, Taghi
    et al.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för energi- och maskinteknik. Faculty of Engineering and Sustainable Development.
    Awbi, Hazim B.
    University of Reading, UK.
    Performance evaluation of two air distribution systems2001In: Proceedings of 5th International Conference Ventilation for Automotive Industry, 2001Conference paper (Refereed)
    Abstract [en]

    This paper focuses on evaluating the performance of a wall displacement ventilation system and a new impinging jet ventilation system. Ventilation efficiency, local mean age of air and other characteristic parameters were experimentally and numerically obtained for a mock-up classroom. The internal heat load of 25 person-simulators were set to represent a crowded classroom in order to investigate any indoor climate problems caused by increased cooling loads. Four ventilation strategies were compared in a previous paper [1] but here we have chosen only the two systems mentioned. In addition to a large number of costly experiments we used CFD simulations to study certain parameters in more detail and explore the results for other situations such as industrial ventilation. The results presented here are part of a larger search programme to develop alternative and efficient systems for new challenging situations of room airflow distribution.

  • 17.
    Karimipanah, Taghi
    et al.
    University of Gävle, Department of Technology and Built Environment.
    Awbi, Hazim B.
    University of Reading, UK.
    Moshfegh, Bahram
    University of Gävle, Department of Technology and Built Environment.
    On the Energy consumption of high-and low-level Air supplies2006Conference paper (Refereed)
  • 18.
    Karimipanah, Taghi
    et al.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för energi- och maskinteknik.
    Awbi, Hazim
    University of Reading, UK.
    Bahram, Moshfegh
    Linköping University.
    The Air Distribution Index as an Indicator for Energy Consumption and Performance of Ventilation Systems2008In: Journal of the Human-Environment System, ISSN 1349-7723, Vol. 11, no 2, p. 77-84Article in journal (Other academic)
    Abstract [en]

    This paper deals with the energy consumption and the evaluation of the performance of air supply systems for a ventilated room involving high- and low-level supplies. The energy performance assessment is based on the airflow rate, which is related to the fan power consumption by achieving the same environmental quality performance for each case. Four different ventilation systems are considered: wall displacement ventilation, confluent jets ventilation, impinging jet ventilation and a high level mixing ventilation system. The ventilation performance of these systems will be examined by means of achieving the same Air Distribution Index (ADI) for different cases.The widely used high-level supplies require much more fan power than those for low-level supplies for achieving the same value of ADI. In addition, the supply velocity, hence the supply dynamic pressure, for a high-level supply is much larger than for low-level supplies. This further increases the power consumption for high-level supply systems.The paper considers these factors and attempts to provide some guidelines on the difference in the energy consumption associated with high and low level air supply systems. This will be useful information for designers and to the authors' knowledge there is a lack of information available in the literature on this area of room air distribution.The energy performance of the above-mentioned ventilation systems has been evaluated on the basis of the fan power consumed which is related to the airflow rate required to provide equivalent indoor environment. The Air Distribution Index (ADI) is used to evaluate the indoor environment produced in the room by the ventilation strategy being used. The results reveal that mixing ventilation requires the highest fan power and the confluent jets ventilation needs the lowest fan power in order to achieve nearly the same value of ADI.

  • 19.
    Karimipanah, Taghi
    et al.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för energi- och maskinteknik. School of Construction Management and Engineering, University of Reading, United Kingdom.
    Awbi, Hazim
    School of Construction Management and Engineering, University of Reading.
    Moshfegh, Bahram
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för energi- och maskinteknik. Division of Energy Systems, Department of Management and Engineering, Linköping University .
    The air distribution as an indicator for energy consumption and performance of ventilation systems2008In: Journal of the Human-Environment System, ISSN 1345-1324, Vol. 11, no 2, p. 77-84Article in journal (Refereed)
    Abstract [en]

    This paper deals with the energy consumption and the evaluation of the performance of air supply systems for a ventilated room involving high- and low-level supplies. The energy performance assessment is based on the airflow rate, which is related to the fan power consumption by achieving the same environmental quality performance for each case. Four different ventilation systems are considered: wall displacement ventilation, confluent jets ventilation, impinging jet ventilation and a high level mixing ventilation system. The ventilation performance of these systems will be examined by means of achieving the same Air Distribution Index (ADI) for different cases.The widely used high-level supplies require much more fan power than those for low-level supplies for achieving the same value of ADI. In addition, the supply velocity, hence the supply dynamic pressure, for a high-level supply is much larger than for low-level supplies. This further increases the power consumption for high-level supply systems.The paper considers these factors and attempts to provide some guidelines on the difference in the energy consumption associated with high and low level air supply systems. This will be useful information for designers and to the authors' knowledge there is a lack of information available in the literature on this area of room air distribution.The energy performance of the above-mentioned ventilation systems has been evaluated on the basis of the fan power consumed which is related to the airflow rate required to provide equivalent indoor environment. The Air Distribution Index (ADI) is used to evaluate the indoor environment produced in the room by the ventilation strategy being used. The results reveal that mixing ventilation requires the highest fan power and the confluent jets ventilation needs the lowest fan power in order to achieve nearly the same value of ADI.

  • 20.
    Karimipanah, Taghi
    et al.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö. Fresh AB, Sweden; University of Reading, UK.
    Awbi, Hazim
    University of Reading, United Kingdom .
    Sandberg, Mats
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Blomqvist, Claes
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Investigation of air quality, comfort parameters and effectiveness for two floor-level air supply systems in classrooms2007In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 42, no 2, p. 647-655Article in journal (Refereed)
    Abstract [en]

    The method of distributing the outdoor air in classrooms has a major impact on indoor air quality and thermal comfort of pupils. In a previous study, ([11] Karimipanah T, Sandberg M, Awbi HB. A comparative study of different air distribution systems in a classroom. In: Proceedings of Roomvent 2000, vol. II, Reading, UK, 2000. p. 1013-18; [13] Karimipanah T, Sandberg M, Awbi HB, Blomqvist C. Effectiveness of confluent jets ventilation system for classrooms. In: Idoor Air 2005, Beijing, China, 2005 (to be presented).) presented results for four and two types of air distribution systems tested in a purpose built classroom with simulated occupancy as well as computational fluid dynamics (CFD) modelling. In this paper, the same experimental setup has been used to investigate the indoor environment in the classroom using confluent jet ventilation, see also ([12] Cho YJ, Awbi HB, Karimipanah T. The characteristics of wall confluent jets for ventilated enclosures. In: Proceedings of Roomvent 2004, Coimbra, Portugal, 2004.) Measurements of air speed, air temperature and tracer gas concentrations have been carried out for different thermal conditions. In addition, 56 cases of CFD simulations have been carried to provide additional information on the indoor air quality and comfort conditions throughout the classroom, such as ventilation effectiveness, air exchange effectiveness, effect of flow rate, effect of radiation, effect of supply temperature, etc., and these are compared with measured data.

  • 21.
    Karimipanah, Taghi
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy engineering.
    Cehlin, Mathias
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy engineering.
    Comparing the efficiency of three turbulence models with experiments conducted for a two-dimensional wall jet in a ventilated room: 2011In: Proceedings of Roomvent 2011, 11th International Conference on Air Distribution in Rooms 19 - 22 June 2011 Torendheim, Norway, 2011, p. 8-Conference paper (Refereed)
  • 22.
    Karimipanah, Taghi
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Larsson, Ulf
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Cehlin, Mathias
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Investigation of flow pattern for a confluent-jets system on a workbench of an industrial space2014In: Indoor Air 2014: 13th International Conference on Indoor Air Quality and Climate, 2014, p. 192-199Conference paper (Refereed)
    Abstract [en]

    A new air supply terminal based on confluent jets was installed on a workbench, in vicinity of a CNC machine, of an industrial space. The flow pattern and temperature field was carried out by CFD calculations and infrared camera imaging technique. A main goal of this technique is to save energy therefore the jet should distribute the air where it is desired. This is possible because the confluent jets system uses the benefits of both mixing (high momentum for better spreading of the air jet) and displacement (cleaner air in occupied zone). The results show that thermal comfort and air quality analysis relies on consistent facts and is in good agreements with the existed standards. It was shown that the supply terminal is able to spread the fresh air to the needed work area. This is an advantage of the high momentum air distribution system used in this investigation.

  • 23.
    Karimipanah, Taghi
    et al.
    Faculty of Engineering and Sustainable Development.
    Moshfegh, Bahram
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för energi- och maskinteknik.
    On the performance of confluent jets ventilation system in office space2007In: In Proc. of Roomvent 2007, 10th International Conference on Air Distribution in Rooms, 13-15 June Helsinki, Finland (2007), 2007Conference paper (Refereed)
  • 24.
    Karimipanah, Taghi
    et al.
    Faculty of Engineering and Sustainable Development.
    Moshfegh, Bahram
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för energi- och maskinteknik.
    Awbi, Hazim
    University of Reading, UK.
    On the energy consumption of high and low-level air suppliers2006Conference paper (Refereed)
  • 25.
    Karimipanah, Taghi
    et al.
    Department of Thermo- and Fluid Dynamics, Chalmers University of Technology, 412 96 Göteborg, Sweden.
    Olsson, Erik
    Department of Thermo- and Fluid Dynamics, Chalmers University of Technology, 412 96 Göteborg, Sweden.
    Calculation of three-dimensional boundary layers on rotor blades using integral methods1993In: Journal of turbomachinery, Vol. 115, no 2, p. 342-353Article in journal (Refereed)
    Abstract [en]

    The important effects of rotation and compressibility on rotor blade boundary layers are theoretically investigated. The calculations are based on the momentum integral method and results from calculations of a transonic compressor rotor are presented. Influence of rotation is shown by comparing the incompressible rotating flow with the stationary one. Influence of compressibility is shown by comparing the compressible rotating flow with the incompressible rotating one. Two computer codes for three-dimensional laminar and turbulent boundary layers, originally developed by SSPA Maritime Consulting AB, have been further developed by introducing rotation and compressibility terms into the boundary layer equations. The effect of rotation and compressibility on the transition have been studied. The Coriolis and centrifugal forces that contribute to the development of the boundary layers and influence its behavior generate crosswise flow inside the blade boundary layers, the magnitude of which depends upon the angular velocity of the rotor and the rotor geometry. The calculations show the influence of rotation and compressibility on the boundary layer parameters. Momentum thickness and shape factor increase with increasing rotation and decrease when compressible flow is taken into account. For skin friction such effects have inverse influences. The different boundary layer parameters behave similarly on the suction and pressure sides with the exception of the crossflow angle, the crosswise momentum thickness, and the skin friction factor. The codes use a nearly orthogonal streamline coordinate system, which is fixed to the blade surface and rotates with the blade.

  • 26. Karimipanah, Taghi
    et al.
    Sandberg, Mats
    Maximum velocity of return flow close to the floor in a ventilated room - experimental and numerical results1996Conference paper (Refereed)
    Abstract [en]

    The problem of sensation of draught in ventilated spaces is connected to inappropriate velocities in the occupied zone. In Scandinavia, velocities higher than 0.15 m/s are said to be an indicator of that occupants are likely to feel discomfort. Therefore knowledge of the flow field (both mean velocities and fluctuations) is necessary. Both experimental and numerical analysis of the flow field in a full scale room ventilated by a slot inlet, with two inlet Reynolds numbers 2440 and 7110, have been carried out . Results from both approaches show that the location of the maximum velocity near the floor is nearly independent of the Reynolds number. For a two-dimensional room, the maximum velocity at the floor level occurred at about 213 room length from the supply. The distance from the floor level is dependent on the inlet Reynolds number. The velocity profiles far away from the wall opposite to the inlet device have the same character as a wall jet profile. However, close to the corners they are transformed. The relative turbulence intensities measured in the return flow region are questionable, because of a hot wire's inability to record large fluctuations at low mean velocities. These turbulence intensities close to floor level vary from 15 to 80 % and as the authors have pointed out previously hot wires do not indicate the real value of the turbulence intensities beyond 20%. Difficulties appear in numerical predictions of return flow properties. Comparison between predicted values and experimentally obtained values show a reasonable agreement. This is promising for future CFD-predictions. However, there is a need for an appropriate measurement technique that can cope with reversing flow.

  • 27.
    Karimipanah, Taghi
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy engineering.
    Sandberg, Mats
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Building science - installation technology.
    Some observations of interaction between the ambient and an axisymmetric jet impinging on a surface: 2011In: Proceedings of Roomvent 2011, 11th International Conference on Air Distribution in Rooms 19 - 22 June 2011 Torendheim, Norway., 2011, , p. 8Conference paper (Refereed)
  • 28.
    Karimipanah, Taghi
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering. Faculty of Engineering and Sustainable Development.
    Sandberg, Mats
    Awbi, Hazim B.
    University of Reading, UK.
    A comparative study of different air distribution systems in a classroom2000In: Air distributions in rooms: Ventilation for Health and Sustainable Environment / [ed] Hazim B. Awbi, Elsevier, 2000, Vol. 2, p. 1013-1018Conference paper (Refereed)
  • 29.
    Sadrizadeh, Sasan
    et al.
    Division of Fluid and Climate Technology, School of Architecture and the Built Environment, KTH Royal Institute of Technology, Stockholm, Sweden; Department of Energy Performance, Indoor Environment and Sustainability of Buildings, Danish Building Research Institute, Aalborg University, Copenhagen, Denmark.
    Afshari, Alireza
    Department of Energy Performance, Indoor Environment and Sustainability of Buildings, Danish Building Research Institute, Aalborg University, Copenhagen, Denmark.
    Karimipanah, Taghi
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Håkansson, Ulf
    Skanska AB, Stockholm, Sweden.
    Nielsen, Peter
    Department of Civil Engineering, Aalborg University, Aalborg, Denmark.
    Numerical simulation of the impact of surgeon posture on airborne particle distribution in a turbulent mixing operating theatre2016In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 110, p. 140-147Article in journal (Refereed)
    Abstract [en]

    Airborne particles released from surgical team members are major sources of surgical site infections. To reduce the risk of such infections, ultraclean-zoned ventilation systems have been widely applied, as a complement to the ventilation of the main operating theatre. The function of ventilation in an operating theatre is usually determined without considering the influence of the staff members’ posture and movements. The question of whether the surgeon's posture during an on-going operation will influence particle distribution within the surgical area has not yet been explored in depth or well documented. In the present study we analysed data from investigation of two positions (bending and straightened up), which represent the most common surgeon and staff-member postures. The investigation was performed by applying the computational fluid dynamics methodology to solve the governing equations for airflow and airborne particle dispersion. Ultraclean-zoned ventilation systems were examined as an addition to the conventional operating theatre. We examined three distinct source strengths (mean value of pathogens emitted from one person per second) due to the variety of staff clothing systems. In the upright posture, the screen units reduced the mean air counts of bacteria and the mean counts of sedimenting bacteria to a standard level for infection-prone surgeries in the surgical area. However, the performance of this system could be reduced drastically by improper work experience. Surgical garments with a high protective capacity result in lower source strength and thus reduces the particle concentration within the surgical area. These results are useful for developing best practices to prevent or at least reduce the infection rate during a surgical intervention.

  • 30.
    Shakeri, Amid
    et al.
    Department of Mechanical and Industrial Engineering, Concordia University, Montreal, QC, Canada .
    Dolatabadi, Ali
    Department of Mechanical and Industrial Engineering, Concordia University, Montreal, QC, Canada .
    Haghighat, Fariborz
    Department of Building, Civil and Environmental Engineering, Concordia University, Montreal, QC, Canada .
    Karimipanah, Taghi
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för inomhusmiljö.
    Impact of occupant modelling on the prediction of airflow around occupants in a ventilated room2007In: The International Journal of Ventilation, ISSN 1473-3315, E-ISSN 2044-4044, Vol. 6, no 2, p. 129-144Article in journal (Refereed)
    Abstract [en]

    Localized ventilation systems typically create highly asymmetric or non-isothermal environments around occupants with significant vertical temperature gradient and highly non-uniform airflow regimes that could be directed toward a segment of the body. These effects may have pronounced impact on occupant's thermal comfort. The airflow field and temperature distribution near the occupant can be determined either by performing full-scale measurements or by simulation methods. Usually, human subjects or manikins are used in field studies involving measurement techniques. However, as an alternative to full-scale measurement, Computational Fluid Dynamics (CFD) has been proven to be a practical and valuable tool for predicting the airflow field. At the same time, the accuracy of the predictions of the local airflow within the microclimate of the occupant is highly dependent on the proper modelling of the occupant itself. The human body not only has a complicated physical shape, but also has complex thermo-physiological properties. Modelling of all these aspects is a formidable challenge and an extremely time-consuming task. Therefore, various simplifications have been made in order to decrease the level of complexity so that the computation may be performed with the available computer resources. This paper reports the results of a detail numerical simulation to study the impact of occupant modelling on the airflow and temperature distribution and their influences on the occupant's thermal comfort. First, the predictions made by the CFD model were compared with experimental data that were measured in a specially designed experimental chamber. Good agreement was observed. Four type of configuration were used to model the occupant: a conventional block form, three-node, six-node and finally eight-node configurations. Further simulations were carried out to investigate the assumption of uniform heat distribution. An assessment of uniform and non-uniform heat distribution scenarios for various occupant configurations and ventilation systems showed that the assumption of uniform heat distribution is valid for a wide range of operating conditions.

  • 31.
    Taghi, Karimipanah
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Sandberg, Mats
    The confinement effects on jet kinetic momentum flux quantified by measuring the reaction force2014In: The International Journal of Ventilation, ISSN 1473-3315, E-ISSN 2044-4044, Vol. 13, no 3, p. 285-298Article in journal (Refereed)
    Abstract [en]

    A turbulent jet is the most important flow element in mechanical ventilation. Mixing ventilation is basedon the properties of turbulent jets. By entrainment into the jet the ambient air is set into motion. For ajet supplied within a room the enclosure may affect the jet in several ways, through: a) Coanda effect which is the tendency of a fluid to be attracted to a nearby surface. A free jet is turned into a wall jet and the momentum flux of the jet decreases by friction against the room surfaces.b) The jet collides with the opposing wall and the jet is transformed into a wall jet. c) The size of the cross sectional area relative to the supply opening will affect the flow pattern withinthe enclosure. One can expect the direction of the inflow (entrainment) to the jet to be affected. d) Location of supply and extract. The location of the supply is a factor that influences the pressure gradient within the room. This paper considers the items b), c) and d). The main characteristic of a jet is its momentum flux, but determining the momentum flux is not an easy task and has lead to contradicting results. Standard methods require velocity field measurements which have their restrictions and uncertainties. To overcome these problems a direct and more reliable method was used by recording the flow force, caused by an impinging jet, with a digital balance. Thetests were carried out both for unenclosed (free jet) and enclosed cases. In the latter case tests were conducted with supply and extract both located on the same wall and located on opposite walls. Detailed pressure measurements were conducted to describe the details of the reaction force. There was a clear effect of the confinement on the reaction force and a Reynolds number dependence.

  • 32.
    Vachaparambil, Kurian Jory
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Cehlin, Mathias
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Karimipanah, Taghi
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building, Energy and Environmental Engineering, Energy system.
    Comparative Numerical Study of the Indoor Climate for Mixing and Confluent Jet Ventilation Systems in an Open-plan Office2018In: Proceedings of the 4th international Conference on Building Energy & Environment, Melbourne: Conference On Building Energy & Environment - COBEE2018, Melbourne Australia , 2018, p. 73-78Conference paper (Refereed)
  • 33.
    Yang, Bin
    et al.
    Department of Applied Physics and Electronics, Umeå University, Umeå, Sweden.
    Melikov, A.K.
    International Centre for Indoor Environment and Energy, Department of Civil Engineering, Technical University of Denmark, Denmark.
    Kabanshi, Alan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Zhang, C.
    Department of Civil Engineering, Aalborg University, Aalborg, Denmark.
    Bauman, F. S.
    Center for the Built Environment, University of California, Berkeley, CA, United States.
    Cao, G.
    Department of Energy and Process, Norwegian University of Science and Technology, KolbjørnHejesVei 1B, Trondheim, Norway.
    Awbi, H.
    School of Construction Management and Engineering, University of Reading, United Kingdom.
    Wigö, Hans
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Niu, J.
    School of Architecture, Design and Planning, The University of Sydney, Australia.
    Cheong, K. W. D.
    Department of Building, School of Design and Environment, National University of Singapore, Singapore.
    Tham, K. W.
    Department of Building, School of Design and Environment, National University of Singapore, Singapore.
    Sandberg, Mats
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Nielsen, P. V.
    Department of Civil Engineering, Aalborg University, Aalborg, Denmark.
    Kosonen, R.
    Department of Mechanical Engineering, School of Engineering, Aalto University, Espoo, Finland; College of Urban Construction, Nanjing Tech University, Nanjing, China.
    Yao, R.
    School of Construction Management and Engineering, University of Reading, United Kingdom.
    Kato, S.
    Institute of Industrial Science, The University of Tokyo, Tokyo, Japan.
    Sekhar, S. C.
    Department of Building, School of Design and Environment, National University of Singapore, Singapore.
    Schiavon, Stefano
    Center for the Built Environment, University of California, Berkeley, CA, United States.
    Karimipanah, Taghi
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Building Engineering, Energy Systems and Sustainability Science, Energy Systems and Building Technology.
    Li, X.
    Department of Building Science, School of Architecture, Tsinghua University, Beijing, China.
    Lin, Z.
    Division of Building Science and Technology, City University of Hong Kong, Hong Kong, Hong Kong.
    A review of advanced air distribution methods - theory, practice, limitations and solutions2019In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 202, article id 109359Article in journal (Refereed)
    Abstract [en]

    Ventilation and air distribution methods are important for indoor thermal environments and air quality. Effective distribution of airflow for indoor built environments with the aim of simultaneously offsetting thermal and ventilation loads in an energy efficient manner has been the research focus in the past several decades. Based on airflow characteristics, ventilation methods can be categorized as fully mixed or non-uniform. Non-uniform methods can be further divided into piston, stratified and task zone ventilation. In this paper, the theory, performance, practical applications, limitations and solutions pertaining to ventilation and air distribution methods are critically reviewed. Since many ventilation methods are buoyancy driving that confines their use for heating mode, some methods suitable for heating are discussed. Furthermore, measuring and evaluating methods for ventilation and air distribution are also discussed to give a comprehensive framework of the review.

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