@article{AlsaadVoelker,
  author    = {Alsaad, Hayder and V{\"o}lker, Conrad},
  title     = {Could the ductless personalized ventilation be an alternative to the regular ducted personalized ventilation?},
  series = {Indoor Air},
  volume    = {2020},
  journal   = {Indoor Air},
  publisher = {John Wiley \& Sons Ltd},
  doi       = {10.1111/ina.12720},
  url       = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20200805-42072},
  pages     = {13},
  abstract  = {This study investigates the performance of two systems: personalized ventilation (PV) and ductless personalized ventilation (DPV). Even though the literature indicates a compelling performance of PV, it is not often used in practice due to its impracticality. Therefore, the present study assesses the possibility of replacing the inflexible PV with DPV in office rooms equipped with displacement ventilation (DV) in the summer season. Numerical simulations were utilized to evaluate the inhaled concentration of pollutants when PV and DPV are used. The systems were compared in a simulated office with two occupants: a susceptible occupant and a source occupant. Three types of pollution were simulated: exhaled infectious air, dermally emitted contamination, and room contamination from a passive source. Results indicated that PV improved the inhaled air quality regardless of the location of the pollution source; a higher PV supply flow rate positively impacted the inhaled air quality. Contrarily, the performance of DPV was highly sensitive to the source location and the personalized flow rate. A higher DPV flow rate tends to decrease the inhaled air quality due to increased mixing of pollutants in the room. Moreover, both systems achieved better results when the personalized system of the source occupant was switched off.},
  subject      = {Str{\"o}mungsmechanik},
  language  = {en}
}
@article{VoelkerMaempelKornadt,
  author    = {V{\"o}lker, Conrad and M{\"a}mpel, Silvio and Kornadt, Oliver},
  title     = {Measuring the human body's micro-climate using a thermal manikin},
  series = {Indoor Air},
  journal   = {Indoor Air},
  number    = {24, 6},
  doi       = {10.25643/bauhaus-universitaet.3815},
  url       = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20181025-38153},
  pages     = {567 -- 579},
  abstract  = {The human body is surrounded by a micro-climate which results from its convective release of heat. In this study, the air temperature and flow velocity of this micro-climate were measured in a climate chamber at various room temperatures, using a thermal manikin simulating the heat release of the human being. Different techniques (Particle Streak Tracking, thermography, anemometry, and thermistors) were used for measurement and visualization. The manikin surface temperature was adjusted to the particular indoor climate based on simulations with a thermoregulation model (UCBerkeley Thermal Comfort Model). We found that generally, the micro-climate is thinner at the lower part of the torso, but expands going up. At the head, there is a relatively thick thermal layer, which results in an ascending plume above the head. However, the micro-climate shape strongly depends not only on the body segment, but also on boundary conditions: the higher the temperature difference between the surface temperature of the manikin and the air temperature, the faster the air flow in the micro-climate. Finally, convective heat transfer coefficients strongly increase with falling room temperature, while radiative heat transfer coefficients decrease. The type of body segment strongly influences the convective heat transfer coefficient, while only minimally influencing the radiative heat transfer coefficient.},
  subject      = {Raumklima},
  language  = {en}
}
@article{AlsaadVoelker,
  author    = {Alsaad, Hayder and V{\"o}lker, Conrad},
  title     = {Performance assessment of a ductless personalized ventilation system using a validated CFD model},
  series = {Journal of Building Performance Simulation},
  volume    = {2018},
  journal   = {Journal of Building Performance Simulation},
  number    = {11, Heft 6},
  doi       = {10.25643/bauhaus-universitaet.3850},
  url       = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20190218-38500},
  pages     = {689 -- 704},
  abstract  = {The aim of this study is twofold: to validate a computational fluid dynamics (CFD) model, and then to use the validated model to evaluate the performance of a ductless personalized ventilation (DPV) system. To validate the numerical model, a series of measurements was conducted in a climate chamber equipped with a thermal manikin. Various turbulence models, settings, and options were tested; simulation results were compared to the measured data to determine the turbulence model and solver settings that achieve the best agreement between the measured and simulated values. Subsequently, the validated CFD model was then used to evaluate the thermal environment and indoor air quality in a room equipped with a DPV system combined with displacement ventilation. Results from the numerical model were then used to quantify thermal sensation and comfort using the UC Berkeley thermal comfort model.},
  subject      = {Ventilation},
  language  = {en}
}
@article{AlsaadVoelker,
  author    = {Alsaad, Hayder and V{\"o}lker, Conrad},
  title     = {Performance evaluation of ductless personalized ventilation in comparison with desk fans using numerical simulations},
  series = {Indoor Air},
  volume    = {2020},
  journal   = {Indoor Air},
  publisher = {John Wiley \& Sons Ltd},
  doi       = {10.1111/ina.12672},
  url       = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20200422-41407},
  pages     = {14},
  abstract  = {The performance of ductless personalized ventilation (DPV) was compared to the performance of a typical desk fan since they are both stand-alone systems that allow the users to personalize their indoor environment. The two systems were evaluated using a validated computational fluid dynamics (CFD) model of an office room occupied by two users. To investigate the impact of DPV and the fan on the inhaled air quality, two types of contamination sources were modelled in the domain: an active source and a passive source. Additionally, the influence of the compared systems on thermal comfort was assessed using the coupling of CFD with the comfort model developed by the University of California, Berkeley (UCB model). Results indicated that DPV performed generally better than the desk fan. It provided better thermal comfort and showed a superior performance in removing the exhaled contaminants. However, the desk fan performed better in removing the contaminants emitted from a passive source near the floor level. This indicates that the performance of DPV and desk fans depends highly on the location of the contamination source. Moreover, the simulations showed that both systems increased the spread of exhaled contamination when used by the source occupant.},
  subject      = {Behaglichkeit},
  language  = {en}
}