@inproceedings{AlsaadVoelker,
  author    = {Alsaad, Hayder and V{\"o}lker, Conrad},
  title     = {Measuring and visualizing the flow supplied by personalized ventilation},
  series = {Proceedings Book Roomvent 2020},
  booktitle = {Proceedings Book Roomvent 2020},
  address   = {Turin, Italy},
  doi       = {10.25643/bauhaus-universitaet.4657},
  url       = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20220622-46573},
  abstract  = {This study investigates the flow supplied by personalized ventilation (PV) by means of anemometer measurements and schlieren visualization. The study was conducted using a thermal manikin to simulate a seated occupant facing a PV outlet. Air velocity was measured at multiple points in the flow field; the collected velocity values were used to calculate the turbulence intensity. Results indicated that PV was supplying air with low turbulence intensity that was able to penetrate the convective boundary layer of the manikin to supply clean air for inhalation. The convective boundary layer, however, obstructed the supplied flow and reduced its velocity by a total of 0.26 m/s. The PV flow preserved its value until about 10 cm from the face where velocity started to drop. Further investigations were conducted to test a PV diffuser with a relatively large outlet diameter (18 cm). This diffuser was developed using 3d-modelling and 3d-printing. The diffuser successfully distributed the flow over the larger outlet area. However, the supplied velocity and turbulence fields were not uniform across the section.},
  subject      = {Bel{\"u}ftung},
  language  = {en}
}
@article{AlsaadVoelker,
  author    = {Alsaad, Hayder and V{\"o}lker, Conrad},
  title     = {Qualitative evaluation of the flow supplied by personalized ventilation using schlieren imaging and thermography},
  series = {Building and Environment},
  volume    = {2020},
  journal   = {Building and Environment},
  number    = {Volume 167, article 106450},
  publisher = {Elsevier},
  address   = {New York},
  doi       = {10.25643/bauhaus-universitaet.4511},
  url       = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20211008-45117},
  pages     = {11},
  abstract  = {Personalized ventilation (PV) is a mean of delivering conditioned outdoor air into the breathing zone of the occupants. This study aims to qualitatively investigate the personalized flows using two methods of visualization: (1) schlieren imaging using a large schlieren mirror and (2) thermography using an infrared camera. While the schlieren imaging was used to render the velocity and mass transport of the supplied flow, thermography was implemented to visualize the air temperature distribution induced by the PV. Both studies were conducted using a thermal manikin to simulate an occupant facing a PV outlet. As a reference, the flow supplied by an axial fan and a cased axial fan was visualized with the schlieren system as well and compared to the flow supplied by PV. Schlieren visualization results indicate that the steady, low-turbulence flow supplied by PV was able to penetrate the thermal convective boundary layer encasing the manikin's body, providing clean air for inhalation. Contrarily, the axial fan diffused the supplied air over a large target area with high turbulence intensity; it only disturbed the convective boundary layer rather than destroying it. The cased fan supplied a flow with a reduced target area which allowed supplying more air into the breathing zone compared to the fan. The results of thermography visualization showed that the supplied cool air from PV penetrated the corona-shaped thermal boundary layer. Furthermore, the supplied air cooled the surface temperature of the face, which indicates the large impact of PV on local thermal sensation and comfort.},
  subject      = {Bildverarbeitung},
  language  = {en}
}
@inproceedings{Dokhanchi,
  author    = {Dokhanchi, Najmeh Sadat},
  title     = {Reconstruction of the indoor air temperature distribution using acoustic travel-time tomography},
  editor    = {Arnold, J{\"o}rg},
  doi       = {10.25643/bauhaus-universitaet.4659},
  url       = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20220622-46593},
  abstract  = {Acoustic travel-time tomography (ATOM) is being increasingly considered recently as a remote sensing methodology to determine the indoor air temperatures distribution. It employs the relationship between the sound velocities along sound-paths and their related travel-times through measured room-impulse-response (RIR). Thus, the precise travel-time estimation is of critical importance which can be performed by applying an analysis time-window method. In this study, multiple analysis time-windows with different lengths are proposed to overcome the challenge of accurate detection of the travel-times at RIR. Hence, the ATOM-temperatures distribution has been measured at the climate chamber lab of the Bauhaus-University Weimar. As a benchmark, the temperatures of NTC thermistors are compared to the reconstructed temperatures derived from the ATOM technique illustrating this technique can be a reliable substitute for traditional thermal sensors. The numerical results indicate that the selection of an appropriate analysis time-window significantly enhances the accuracy of the reconstructed temperatures distribution.},
  subject      = {Bauphysik},
  language  = {en}
}
@article{AlsaadHartmannVoelker,
  author    = {Alsaad, Hayder and Hartmann, Maria and Voelker, Conrad},
  title     = {The effect of a living wall system designated for greywater treatment on the hygrothermal performance of the facade},
  series = {Energy and Buildings},
  volume    = {2022},
  journal   = {Energy and Buildings},
  number    = {volume 255, article 111711},
  doi       = {10.1016/j.enbuild.2021.111711},
  url       = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20240116-65299},
  pages     = {17},
  abstract  = {Besides their multiple known benefits regarding urban microclimate, living walls can be used as decentralized stand-alone systems to treat greywater locally at the buildings. While this offers numerous environmental advantages, it can have a considerable impact on the hygrothermal performance of the facade as such systems involve bringing large quantities of water onto the facade. As it is difficult to represent complex entities such as plants in the typical simulation tools used for heat and moisture transport, this study suggests a new approach to tackle this challenge by coupling two tools: ENVI-Met and Delphin. ENVI-Met was used to simulate the impact of the plants to determine the local environmental parameters at the living wall. Delphin, on the other hand, was used to conduct the hygrothermal simulations using the local parameters calculated by ENVI-Met. Four wall constructions were investigated in this study: an uninsulated brick wall, a precast concrete plate, a sandy limestone wall, and a double-shell wall. The results showed that the living wall improved the U-value, the exterior surface temperature, and the heat flux through the wall. Moreover, the living wall did not increase the risk of moisture in the wall during winter and eliminated the risk of condensation.},
  subject      = {Feuchteleitung},
  language  = {en}
}
@article{BecherGenaAlsaadetal.,
  author    = {Becher, Lia and Gena, Amayu Wakoya and Alsaad, Hayder and Richter, Bernhard and Spahn, Claudia and V{\"o}lker, Conrad},
  title     = {The spread of breathing air from wind instruments and singers using schlieren techniques},
  series = {Indoor Air},
  volume    = {2021},
  journal   = {Indoor Air},
  number    = {volume 31, issue 6},
  publisher = {Wiley Blackwell},
  address   = {Oxford},
  doi       = {10.1111/ina.12869},
  url       = {http://nbn-resolving.de/urn:nbn:de:gbv:wim2-20220209-45817},
  pages     = {1798 -- 1814},
  abstract  = {The spread of breathing air when playing wind instruments and singing was investigated and visualized using two methods: (1) schlieren imaging with a schlieren mirror and (2) background-oriented schlieren (BOS). These methods visualize airflow by visualizing density gradients in transparent media. The playing of professional woodwind and brass instrument players, as well as professional classical trained singers were investigated to estimate the spread distances of the breathing air. For a better comparison and consistent measurement series, a single high note, a single low note, and an extract of a musical piece were investigated. Additionally, anemometry was used to determine the velocity of the spreading breathing air and the extent to which it was quantifiable. The results showed that the ejected airflow from the examined instruments and singers did not exceed a spreading range of 1.2 m into the room. However, differences in the various instruments have to be considered to assess properly the spread of the breathing air. The findings discussed below help to estimate the risk of cross-infection for wind instrument players and singers and to develop efficacious safety precautions, which is essential during critical health periods such as the current COVID-19 pandemic.},
  subject      = {Covid-19},
  language  = {en}
}