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Heschl, Christian
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Official Name
Heschl, Christian
Alternative Name
Heschl, C
Main Affiliation
Akademische Titel
Prof.(FH) Dipl.-Ing. (FH) Dr.
Email
christian.heschl@fh-burgenland.at
Scopus Author ID
50161591800
Status
staff
Research Outputs
Now showing 1 - 10 of 13
- Publication
20 2Scopus© Citations 1 - PublicationImproving predictions of heat transfer in indoor environments with eddy viscosity turbulence modelsHeat transfer modelling in indoor environments requires an accurate prediction of the convective heat transfer phenomenon. Because of the lower computational cost and numerical stability, eddy viscosity turbulence models are often used. These models allow modification to turbulent Prandtl number, and near wall correction which influences stagnation points, entrainment, and velocity and time scales. A modified v 2–f model was made to correct the entrainment behaviour in the near wall and at the stagnation point. This new model was evaluated on six cases involving free and forced convection and room airflow scenarios and compared with the standard k–ε, and k–ω–SST models. The results showed that the modification to the v 2–f model provided better predictions of the buoyant heat transfer flows while the standard k–ε failed to reproduce and underestimate the convective heat transfer. The k–ω–SST model was able to predict the flow field well only for a 2D square cavity room, and 3D partitioned room case, while it was poor for the other four cases.
156 1Scopus© Citations 2 - PublicationNonlinear eddy viscosity modeling and experimental study of jet spreading ratesIndoor airflow pattern is strongly influenced by turbulent shear and turbulent normal stresses that are responsible for entrainment effects and turbulence-driven secondary motion. Therefore, an accurate prediction of room airflows requires reliable modeling of these turbulent quantities. The most widely used turbulence models include RANS-based models that provide quick solutions but are known to fail in turbulent free shear and wall-affected flows. In order to cope with this deficiency, this study presents a nonlinear k-ε turbulence model and evaluates it along with linear k-ε models for an indoor isothermal linear diffuser jet flow measured in two model rooms using PIV. The results show that the flow contains a free jet near the inlet region and a wall-affected region downstream where the jet is pushed toward the ceiling by entrainment through the well-known Coanda effect. The CFD results show that an accurate prediction of the entrainment process is very important and that the nonlinear eddy viscosity model is able to predict the turbulence-driven secondary motions. Furthermore, turbulence models that are calibrated for high Reynolds free shear layer flows were not able to reproduce the measured velocity distributions, and it is suggested that the model constants of turbulence models should be adjusted before they are used for room airflow simulations.
129 1Scopus© Citations 10 - PublicationTowards distributed enthalpy measurement in large-scale air conditioning systems(IEEE, 2015)
; Air conditioning systems are among the major energy consumers in buildings. Energy-efficient operation of AC systems is an important step towards better energy management in building automation, but requires efficient monitoring of the energy or enthalpy flows within the AC installation, which is currently still difficult because of the lack of appropriate equipment. This paper introduces a distributed data acquisition system for large-scale AC systems based on low-cost flow sensors implemented by means of standard printed circuit board technology and interconnected via a wireless sensor network. A critical issue for the system installation is the placement of the sensors in the air ducts to obtain representative measurements of the air flow. To this end, extensive aerodynamical simulations are carried out to analyze the flow distributions in typical building blocks for air ducts, particularly with respect to turbulences. The simulation results are compared with experimental data from the literature and are shown to be reliable.145 1Scopus© Citations 7 - PublicationModeling of solar radiation transmission through triple glazing based only on on-site measurements(2020)
; A model is developed which can calculate the irradiance behind a glazed façade, based on measured incident solar radiation. Data from a real office building is used to establish and test the model. Onsite irradiance measurements on both sides of the facades are exploited to calibrate the model. The main parameters are the average diffuse transmittance and a correlation for the direct transmittance, as a function of the incidence angle. Correction of the measurements, including the frame reflection, are taken into account. Hence, the model contributes to the solar heat flux identification, in the perspective of model predictive control application.25 154 - Publication
223 30703Scopus© Citations 8 - PublicationEvaluation and improvements of RANS turbulence models for linear diffuser flowsFlow patterns produced by linear diffusers are highly dependent on the turbulent momentum exchange process. Hence a realistic computation of indoor room airflows that are produced from plane wall and free jets requires an accurate prediction of the anisotropic turbulent stresses. This is particularly the case in regions near the wall and entrainment effects which are caused by the turbulent shear stresses. For this reason a non-linear eddy viscosity assumption is presented which can be adjusted to account for the turbulent mixing process in the free shear flow region, and to reproduce the redistribution of the turbulent normal stresses near the wall. Based on several test cases such as a free and plane wall jet, IEA (International Energy Agency) Annex 20 room airflow, and a 3D room with a partition, the essential characteristics of the linear and non-linear k-epsilon, k-omega and v(2)-f turbulence models are analysed. Thereby it is shown that the proposed non-linear assumption can improve the prediction of linear diffuser airflows.
138 1Scopus© Citations 33 - PublicationMicron particle deposition in the nasal cavity using the v2–f modelCommercial CFD codes are commonly used to simulate models that involve complicated geometries such as the human nasal cavity. This means that the user has to work within the limitations of the available models of the CFD code. One such issue is the turbulent dispersion of particles in the Lagrangian reference, namely the Discrete Random Walk (DRW) model which overpredicts the deposition of smaller inertial particles, due to its inherent isotropic treatment of the normal to the wall fluctuation, v′ , in the near wall region. DNS data for channel flows has been used to create a function that reduces the turbulent kinetic energy (TKE) to match the v′ profile which has delivered improved particle deposition efficiency results. This paper presents an alternative approach to reduce the TKE to match v′ , by directly taking the profile from the v2–f turbulence model. The approach is validated against experimental pipe flow for a 90° bend and then applied to particle dispersion in a human nasal cavity using Ansys-Fluent which showed improved results compared to no modification.
137 1Scopus© Citations 34 - Publication
42 1286Scopus© Citations 2