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Karimipanah, Taghi, ProfessorORCID iD iconorcid.org/0000-0002-9392-424x
Publications (10 of 32) Show all publications
Cehlin, M., Karimipanah, T., Larsson, U. & Ameen, A. (2019). Comparing thermal comfort and air quality performance of two active chilled beam systems in an open-plan office. Journal of Building Engineering, 22, 56-65
Open this publication in new window or tab >>Comparing thermal comfort and air quality performance of two active chilled beam systems in an open-plan office
2019 (English)In: Journal of Building Engineering, E-ISSN 2352-7102, Vol. 22, p. 56-65Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Active Chilled Beam, Air Change Effectiveness, Heat Removal Effectiveness
National Category
Energy Engineering
Identifiers
urn:nbn:se:hig:diva-28583 (URN)10.1016/j.jobe.2018.11.013 (DOI)000457639900006 ()2-s2.0-85057839765 (Scopus ID)
Funder
Vinnova, 2013-03772
Available from: 2018-11-22 Created: 2018-11-22 Last updated: 2019-08-09Bibliographically approved
Ameen, A., Cehlin, M., Larsson, U. & Karimipanah, T. (2019). Experimental Investigation of Ventilation Performance of Different Air Distribution Systems in an Office Environment: Heating Mode. Energies, 12(10), Article ID 1835.
Open this publication in new window or tab >>Experimental Investigation of Ventilation Performance of Different Air Distribution Systems in an Office Environment: Heating Mode
2019 (English)In: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 12, no 10, article id 1835Article in journal (Refereed) Published
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.

Keywords
Corner impinging jet, mixing ventilation, displacement ventilation, tracer gas, air exchange effectiveness, air change effectiveness, draught rate
National Category
Energy Systems
Identifiers
urn:nbn:se:hig:diva-29582 (URN)10.3390/en12101835 (DOI)2-s2.0-85066877057 (Scopus ID)
Available from: 2019-05-21 Created: 2019-05-21 Last updated: 2019-08-22Bibliographically approved
Ameen, A., Cehlin, M., Larsson, U. & Karimipanah, T. (2019). Experimental investigation of ventilation performance of different air distribution systems in an office environment – cooling mode. Energies, 12(7), Article ID 1354.
Open this publication in new window or tab >>Experimental investigation of ventilation performance of different air distribution systems in an office environment – cooling mode
2019 (English)In: Energies, ISSN 1996-1073, E-ISSN 1996-1073, Vol. 12, no 7, article id 1354Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
MDPI, 2019
Keywords
Corner impinging jet, mixing ventilation, displacement ventilation, tracer gas, air exchange effectiveness, air change effectiveness, draught rate
National Category
Energy Engineering
Identifiers
urn:nbn:se:hig:diva-29443 (URN)10.3390/en12071354 (DOI)000465561400171 ()2-s2.0-85065464428 (Scopus ID)
Available from: 2019-04-05 Created: 2019-04-05 Last updated: 2019-08-16Bibliographically approved
Vachaparambil, K. J., Cehlin, M. & Karimipanah, T. (2018). Comparative Numerical Study of the Indoor Climate for Mixing and Confluent Jet Ventilation Systems in an Open-plan Office. In: Proceedings of the 4th international Conference on Building Energy & Environment: . Paper presented at COBEE2018, 4th international Conference on Building Energy & Environment, 5-9 February 2018, Melbourne, Australia (pp. 73-78). Melbourne: Conference On Building Energy & Environment - COBEE2018, Melbourne Australia
Open this publication in new window or tab >>Comparative Numerical Study of the Indoor Climate for Mixing and Confluent Jet Ventilation Systems in an Open-plan Office
2018 (English)In: Proceedings of the 4th international Conference on Building Energy & Environment, Melbourne: Conference On Building Energy & Environment - COBEE2018, Melbourne Australia , 2018, p. 73-78Conference paper, Published paper (Refereed)
Place, publisher, year, edition, pages
Melbourne: Conference On Building Energy & Environment - COBEE2018, Melbourne Australia, 2018
Keywords
Confluent jet ventilation
National Category
Energy Engineering
Identifiers
urn:nbn:se:hig:diva-26568 (URN)978-0-646-98213-7 (ISBN)
Conference
COBEE2018, 4th international Conference on Building Energy & Environment, 5-9 February 2018, Melbourne, Australia
Available from: 2018-05-15 Created: 2018-05-15 Last updated: 2018-05-21Bibliographically approved
Sadrizadeh, S., Afshari, A., Karimipanah, T., Håkansson, U. & Nielsen, P. (2016). Numerical simulation of the impact of surgeon posture on airborne particle distribution in a turbulent mixing operating theatre. Building and Environment, 110, 140-147
Open this publication in new window or tab >>Numerical simulation of the impact of surgeon posture on airborne particle distribution in a turbulent mixing operating theatre
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2016 (English)In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 110, p. 140-147Article in journal (Refereed) Published
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.

Keywords
Bacteria-carrying particles; CFD simulation; Clothing system; Colony-forming unit; Mobile ultraclean zonal-laminar airflow screen; Operating theatre; Ventilation system
National Category
Mechanical Engineering Medical Engineering
Identifiers
urn:nbn:se:hig:diva-22648 (URN)10.1016/j.buildenv.2016.10.005 (DOI)000388052500013 ()2-s2.0-84992209616 (Scopus ID)
Funder
Swedish Research Council Formas, 2014-1492-28222-29
Available from: 2016-10-22 Created: 2016-10-22 Last updated: 2018-03-22Bibliographically approved
Arghand, T., Karimipanah, T., Awbi, H., Cehlin, M., Larsson, U. & Linden, E. (2015). An experimental investigation of the flow and comfort parameters for under-floor, confluent jets and mixing ventilation systems in an open-plan office. Building and Environment, 92, 48-60
Open this publication in new window or tab >>An experimental investigation of the flow and comfort parameters for under-floor, confluent jets and mixing ventilation systems in an open-plan office
Show others...
2015 (English)In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 92, p. 48-60Article in journal (Refereed) Published
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.

Keywords
Open office, Mixing ventilation (MV), Underfloor air distribution (UFAD), Confluent jets ventilation (CJV)
National Category
Building Technologies
Identifiers
urn:nbn:se:hig:diva-19327 (URN)10.1016/j.buildenv.2015.04.019 (DOI)000358807800006 ()2-s2.0-84929492281 (Scopus ID)
Funder
VINNOVA
Available from: 2015-05-16 Created: 2015-05-16 Last updated: 2019-05-22Bibliographically approved
Cehlin, M. & Karimipanah, T. (2015). Prediction of indoor airflow close to a supply device using SST-SAS Model. In: Taipale A., Li Z., Li X., and Zhang X (Ed.), Ventilation 2015 - Proceedings of the 11th International Conference on Industrial Ventilation: . Paper presented at 11th International Conference on Industrial Ventilation, Ventilation 2015, 26-28 October 2015, Shanghai, China (pp. 681-688). International Conference on Industrial Ventilation, 2
Open this publication in new window or tab >>Prediction of indoor airflow close to a supply device using SST-SAS Model
2015 (English)In: 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, Published 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.

Place, publisher, year, edition, pages
International Conference on Industrial Ventilation, 2015
Keywords
Air entrainment; Atmospheric temperature; Computational fluid dynamics; Forecasting; Navier Stokes equations; Oceanography; Perforated plates; Temperature distribution; Turbulence models; Velocity; Ventilation, Accurate prediction; Displacement ventilation; Kelvin- helmholtz instabilities; Mean flow gradients; SST-SAS; Turbulence intensity; Unsteady cfd; URANS, Air
National Category
Energy Systems
Identifiers
urn:nbn:se:hig:diva-22742 (URN)2-s2.0-84987933806 (Scopus ID)
Conference
11th International Conference on Industrial Ventilation, Ventilation 2015, 26-28 October 2015, Shanghai, China
Available from: 2016-11-11 Created: 2016-11-11 Last updated: 2018-03-13Bibliographically approved
Karimipanah, T., Larsson, U. & Cehlin, M. (2014). Investigation of flow pattern for a confluent-jets system on a workbench of an industrial space. In: Indoor Air 2014: 13th International Conference on Indoor Air Quality and Climate. Paper presented at 13th International Conference on Indoor Air Quality and Climate, July 7-12, 2014, Hong Kong (pp. 192-199).
Open this publication in new window or tab >>Investigation of flow pattern for a confluent-jets system on a workbench of an industrial space
2014 (English)In: Indoor Air 2014: 13th International Conference on Indoor Air Quality and Climate, 2014, p. 192-199Conference paper, Published 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.

Keywords
Workbench, Ventilation, Thermal comfort, Confluent Jets, CFD
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:hig:diva-17859 (URN)2-s2.0-84924711434 (Scopus ID)
Conference
13th International Conference on Indoor Air Quality and Climate, July 7-12, 2014, Hong Kong
Available from: 2014-11-09 Created: 2014-11-09 Last updated: 2019-05-22Bibliographically approved
Taghi, K. & Sandberg, M. (2014). The confinement effects on jet kinetic momentum flux quantified by measuring the reaction force. The International Journal of Ventilation, 13(3), 285-298
Open this publication in new window or tab >>The confinement effects on jet kinetic momentum flux quantified by measuring the reaction force
2014 (English)In: The International Journal of Ventilation, ISSN 1473-3315, E-ISSN 2044-4044, Vol. 13, no 3, p. 285-298Article in journal (Refereed) Published
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.

Keywords
kinetic momentum flux, impinging jet, reaction force, digital balance
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:hig:diva-17861 (URN)000348585900007 ()2-s2.0-84912082575 (Scopus ID)
External cooperation:
Available from: 2014-11-09 Created: 2014-11-09 Last updated: 2018-03-13Bibliographically approved
Cehlin, M., Karimipanah, T. & Larsson, U. (2014). Unsteady CFD simulations for prediction of airflow close to a supply device for displacement ventilation. In: Indoor Air 2014 - 13th International Conference on Indoor Air Quality and Climate: . Paper presented at 13th International Conference on Indoor Air Quality and Climate, Indoor Air 2014, 7-12 July 2014, Hong Kong (pp. 47-54).
Open this publication in new window or tab >>Unsteady CFD simulations for prediction of airflow close to a supply device for displacement ventilation
2014 (English)In: Indoor Air 2014 - 13th International Conference on Indoor Air Quality and Climate, 2014, p. 47-54Conference paper, Published 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.

Keywords
Displacement ventilation, Unsteady CFD, URANS, Air, Air quality, Computational fluid dynamics, Indoor air pollution, Inlet flow, Perforated plates, Turbulence, Mean flow gradients, Turbulence intensity, Unsteady cfd simulations, Unsteady simulations, Velocity profiles, Ventilation
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:hig:diva-19218 (URN)2-s2.0-84924672267 (Scopus ID)
Conference
13th International Conference on Indoor Air Quality and Climate, Indoor Air 2014, 7-12 July 2014, Hong Kong
Available from: 2015-04-17 Created: 2015-04-17 Last updated: 2019-05-22Bibliographically approved
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Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-9392-424x

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