• CFD and Wind Tunnel Study of the Performance of a Multi-Directional Wind Tower with Heat Transfer Devices

      Calautit, John Kaiser; Hughes, Ben; O'Connor, Dominic; Shahzad, Sally; University of Sheffield; University of Derby (2015)
      The aim of this work was to investigate the performance of a multi-directional wind tower integrated with heat transfer devices (HTD) using Computational Fluid Dynamics (CFD) and wind tunnel analysis. An experimental scale model was created using 3D printing. The scale model was tested in a closed-loop wind tunnel to validate the CFD data. Numerical results of the supply airflow were compared with experimental data. Good agreement was observed between both methods of analysis. Smoke visualisation test was conducted to analyse the air flow pattern in the test room attached underneath it. Results have indicated that the achieved indoor air speed was reduced by up to 17% following the integration of the cylindrical HTD. The effect of varying the number of HTD on the system's thermal performance were investigated. The work highlighted the potential of integrating HTD into wind towers in reducing the air temperature. The technology presented here is subject to a UK patent application (PCT/GB2014/052263).
    • CFD and wind tunnel study of the performance of a uni-directional wind catcher with heat transfer devices

      Calautit, John Kaiser; Hughes, Ben; Shahzad, Sally; University of Sheffield; University of Derby (2015-04-28)
      Computational Fluid Dynamics (CFD) and wind tunnel analysis were conducted to investigate the performance of a uni-directional wind catcher. A detailed experimental benchmark model was created using rapid prototyping and tested in a closed-loop subsonic wind tunnel. An accurate geometrical representation of the wind tunnel test set-up was recreated in the numerical modelling. Experimental results for the indoor and external airflow, supply rate, and pressure coefficients were compared with the numerical results. Smoke visualisation experiment was also conducted to further analyse the detailed airflow structure within the wind catcher and also inside the test room. Following the successful validation of the benchmark CFD model, cylindrical Heat Transfer Devices (HTD) were integrated into the uni-directional wind catcher model to reduce the temperature of air induced into the ventilated space. The findings of the CFD study displayed that the proposed wind catcher was capable of reducing the supply temperature by up to 12 K within the micro-climate depending on the outdoor air speed. However, the addition of the cylindrical HTD also reduced the air supply rates by up to 20–35%.
    • CFD study of effusion cooling

      Yang, Zhiyin; Walton, Matthew; University of Derby (2012-09)
      The desire to increase the efficiency, i.e., reduce the specific fuel consumption and raise the thrust-to-weight ratio, of gas turbines has led to an increase in pressure and temperature in the combustion chamber and turbine. The operational life of the combustion chamber walls decreases with increased temperature thus an effective method of cooling must be used to protect the wall. Effusion cooling provides a practical solution to this engineering problem. A fundamental understanding of the physical mechanisms involved in effusion flow fields is required to make significant advances in cooling technology. At the same time, designers need a predictive design tool that allows quick turnaround times without the current build and break approach. Computational Fluid Dynamics (CFD) presents the designer with the potential for an effective, fast and relatively accurate method of achieving this. This paper presents a computational study of effusion cooling applications using the Reynolds Averaged NavierStokes (RANS) approach. The need to evaluate the predictive capability of the Reynolds Stress Transport (RST) model when applied to Full Coverage Film-Cooling (FCFC) effusion scenarios is highlighted since two-equation Eddy-Viscosity (EV) models fail to predict turbulent anisotropy and therefore the complex flow mechanisms involved in effusion cooling flow fields. An isothermal and non-isothermal numerical study of effusion cooling flow is conducted. In the isothermal case the RST model is shown to be capable of predicting the injection, penetration, downstream decay and lateral mixing of the effusion jets reasonably well. In the non-isothermal case the laterally averaged cooling effectiveness across the plate is slightly under-predicted but still conforms to the general increasing trend.
    • A CFD study of twin Impinging jets in a cross-flow

      Ostheimer, Daniel; Yang, Zhiyin; University of Derby (Bentham Open, 2012-01-17)
      A very complicated three-dimensional (3D) flow field is generated beneath a Vertical/Short Take-Off and Landing (VSTOL) aircraft when it is operated near the ground. This flow field can be represented by the configuration of twin impinging jets along the spanwise direction in a cross-flow. This paper describes a Computational Fluid Dynamics (CFD) study of this flow using the Reynolds Averaged Navier-Stokes (RANS) approach with a Reynolds Stress Model (RSM). The use of an RSM potentially offers a compromise between the computational efficiency of a two equation turbulence model and accuracy closer to that of Large Eddy Simulation (LES) although it will not be as accurate as LES. The current numerical results are validated against experimental data and the mean velocity profiles are reasonably well predicted by both the standard k-ε model and the RSM with slightly better prediction by the RSM. However, the Reynolds stress prediction by the RSM is poor compared with the experimental data, indicating that to capture the detailed unsteady flow features an LES is needed.
    • Computational and field test analysis of thermal comfort performance of user-controlled thermal chair in an open plan office

      Shahzad, Sally; Calautit, John Kaiser; Hughes, Ben; Nasir, Diana S. N. M.; University of Derby; University of Sheffield (Applied Energy, 2016)
      In this study, a thermal chair prototype was developed that allowed individual control over the temperature settings of the backrest and the seat. Limited research is focused on different methods to provide individual user control over the thermal environment. This is particularly difficult to achieve in an open plan office setting, where changing the temperature in one area directly influences the comfort and satisfaction of other occupants seated nearby. In this study, the application of the thermal chair was analysed using Computational Fluid Dynamics (CFD) and field-test analysis in an open plan office in Leeds, UK during winter. The results of the CFD model indicated an improvement in local thermal comfort of the user,. The CFD analysis provided detailed analysis of the thermal distribution around a siting manikin and was used to design and construct the thermal chair. the results of the field data survey indicated a great improvement in users’ comfort (19%) and satisfaction (35%). This study concludes that local thermal control of the occupant improves their overall thermal comfort. It recommends further work to optimise the design of the thermal chair and also to improve the modelling for better predictions.
    • Computational and Wind Tunnel Study of the Performance of a Multi-Directional Wind Tower with Heat Transfer Devices. International Conference on Applied Energy

      Calautit, John Kaiser; O'Connor, Dominic; Hughes, Ben; Shahzad, Sally; University of Sheffield; University of Derby (2015)
      The aim of this work was to investigate the performance of a multi-directional wind tower integrated with heat transfer devices (HTD) using Computational Fluid Dynamics (CFD) and wind tunnel analysis. An experimental scale model was created using 3D printing. The scale model was tested in a closed-loop wind tunnel to validate the CFD data. Numerical results of the supply airflow were compared with experimental data. Good agreement was observed between both methods of analysis. Smoke visualisation test was conducted to analyse the air flow pattern in the test room attached underneath it. Results have indicated that the achieved indoor air speed was reduced by up to 17% following the integration of the cylindrical HTD. The effect of varying the number of HTD on the system's thermal performance were investigated. The work highlighted the potential of integrating HTD into wind towers in reducing the air temperature. The technology presented here is subject to a UK patent application (PCT/GB2014/052263).
    • An effective mesh strategy for CFD modelling of polymer electrolyte membrane fuel cells

      Choopanya, Pattarapong; Yang, Zhiyin; Unviersity of Derby, Department of Engineering (Elsevier, 2016-03-26)
      Computational fluid dynamics (CFD) is a major tool in PEM fuel cell research. Typical three-dimensional PEM fuel cell models involve more than 106 mesh elements. This makes the computation very intense and necessitates a methodology to mesh the computational domain that can keep the number of elements to a minimum while maintaining good accuracy. In this study, the effect of computational mesh in each direction on the accuracy of the solution is investigated in a systematic way. It is found that the mesh in different directions has a different degree of influence on the solution suggesting that the mesh in one direction can be coarser than the other. The proposed mesh strategy is capable of greatly reducing the number of mesh elements, hence computation time, while preserving the characteristics of important flow-field variables. Moreover, it is applicable to a wide range of cell sizes and flow-field configurations and should be used as a guideline for mesh generation.
    • Numerical Analysis of a Wind Catcher Assisted Passive Cooling Technology

      Calautit, John Kaiser; Hughes, Ben; Shahzad, Sally; Nasir, Diana S. N. M.; University of Sheffield; University of Derby (USES 2015 - The University of Sheffield Engineering Symposium, 2015)
      Buildings are responsible for almost 40% of the world energy usage. Heating Ventilation and Air-Conditioning (HVAC) systems consume more than 60% of the total energy use of buildings. Clearly any technology that reduces HVAC consumption will have a dramatic effect on the energy performance of the building. Natural ventilation offers the opportunity to eliminate the mechanical requirements of HVAC systems by using the natural driving forces of external wind and buoyancy effect. One technology, which incorporates both wind and buoyancy driven forces, is the wind catcher. Wind catchers are natural ventilation systems based on the design of traditional architecture. Though the movement of air caused by the wind catcher will lead to a cooling sensation for occupants, the high air temperature in hot climates will result in little cooling to occupants. In order to maximise the properties of cooling by wind catchers, heat transfer devices were incorporated into the design to reduce the supply air temperature. The aim of this work was to investigate the performance of a wind catcher integrated with heat transfer devices using numerical modelling and wind tunnel experiment. The wind catcher model was incorporated to a building, representing a small room of 15 people. Care was taken to generate a high-quality CFD grid and specify consistent boundary conditions. An experimental model was created using 3D printing and tested in a wind tunnel. Qualitative and quantitative wind tunnel measurements were compared with the CFD data and good correlation was observed. The study highlighted the potential of the proposed wind catcher in reducing the air temperature by up to 12 K and supplying the required fresh air rates.
    • Numerical Analysis of a Wind Catcher Assisted Passive Cooling Technology.

      Calautit, John Kaiser; Hughes, Ben; Shahzad, Sally; Nasir, Diana S. N. M.; University of Sheffield; University of Derby (USES 2015 - The University of Sheffield Engineering Symposium, 2015)
      Buildings are responsible for almost 40% of the world energy usage. Heating Ventilation and Air-Conditioning (HVAC) systems consume more than 60% of the total energy use of buildings. Clearly any technology that reduces HVAC consumption will have a dramatic effect on the energy performance of the building. Natural ventilation offers the opportunity to eliminate the mechanical requirements of HVAC systems by using the natural driving forces of external wind and buoyancy effect. One technology, which incorporates both wind and buoyancy driven forces, is the wind catcher. Wind catchers are natural ventilation systems based on the design of traditional architecture. Though the movement of air caused by the wind catcher will lead to a cooling sensation for occupants, the high air temperature in hot climates will result in little cooling to occupants. In order to maximise the properties of cooling by wind catchers, heat transfer devices were incorporated into the design to reduce the supply air temperature. The aim of this work was to investigate the performance of a wind catcher integrated with heat transfer devices using numerical modelling and wind tunnel experiment. The wind catcher model was incorporated to a building, representing a small room of 15 people. Care was taken to generate a high-quality CFD grid and specify consistent boundary conditions. An experimental model was created using 3D printing and tested in a wind tunnel. Qualitative and quantitative wind tunnel measurements were compared with the CFD data and good correlation was observed. The study highlighted the potential of the proposed wind catcher in reducing the air temperature by up to 12 K and supplying the required fresh air rates.
    • Numerical and Experimental Analysis of a Multi-Directional Wind Tower Integrated with Vertically-Arranged Heat Transfer Devices (VHTD).

      Calautit, John Kaiser; Hughes, Ben; O'Connor, Dominic; Shahzad, Sally; University of Sheffield; University of Derby (2016)
      The aim of this work was to investigate the performance of a multi-directional wind tower integrated with vertically-arranged heat transfer devices (VHTD) using Computational Fluid Dynamics (CFD) and wind tunnel analysis. An experimental scale model was created using 3D printing. The scale model was tested in a uniform flow closed-loop wind tunnel to validate the CFD data. Numerical results of the supply airflow were compared with experimental data. Good agreement was observed between both methods of analysis. The Grid Convergence Method (GCI) method was used to estimate the uncertainty due to discretisation. Results have indicated that the achieved indoor air speed was reduced by 8–17% following the integration of the VHTD. The integration of VHTD had a positive effect on cooling performance of the wind tower, it reduced the incoming fresh air by up to 12 K. The effect of varying the number of VHTD rows (1–3 rows) on the system’s performance were also investigated. Additional simulations were also conducted to investigate the effect of atmospheric boundary layer (ABL) flows on the wind tower ventilation performance and also compare it with the results of uniform flow wind tunnel study.
    • Performance Investigation of a Commercial Wind Catcher with Horizontally-Arranged Heat Transfer Devices (HHTD).

      Calautit, John Kaiser; O'Connor, Dominic; Hughes, Ben; Shahzad, Sally; University of Sheffield; University of Derby (2015)
      The aim of this study was to conduct numerical Computational Fluid Dynamics (CFD) and experimental analysis of the performance of a wind catcher with Horizontally-arranged Heat Transfer Devices (HHTD) for hot climate conditions. A detailed experimental prototype was created using 3D printing and tested in a closed-loop low speed wind tunnel. An accurate geometrical representation of the wind tunnel test setup was recreated in the numerical modeling. The airflow supply velocity was measured and compared with the numerical data and good correlation was observed. Flow visualisation testing was conducted to analyse the airflow within the device and also inside the ventilated space. The results of the numerical analysis showed that the wind catcher with HHTD was capable of reducing the air temperature by up to 12 K within the micro-climate depending on the outdoor conditions. The technology presented here is subject to a UK patent application (1321709.6).
    • Performance Investigation of a Commercial Wind Catcher with Horizontally-arranged Heat Transfer Devices (HHTD). 

      Calautit, John Kaiser; O'Connor, Dominic; Hughes, Ben; Shahzad, Sally; University of Sheffield; University of Derby (2015)
      The aim of this study was to conduct numerical Computational Fluid Dynamics (CFD) and experimental analysis of the performance of a wind catcher with Horizontally-arranged Heat Transfer Devices (HHTD) for hot climate conditions. A detailed experimental prototype was created using 3D printing and tested in a closed-loop low speed wind tunnel. An accurate geometrical representation of the wind tunnel test setup was recreated in the numerical modeling. The airflow supply velocity was measured and compared with the numerical data and good correlation was observed. Flow visualisation testing was conducted to analyse the airflow within the device and also inside the ventilated space. The results of the numerical analysis showed that the wind catcher with HHTD was capable of reducing the air temperature by up to 12 K within the micro-climate depending on the outdoor conditions. The technology presented here is subject to a UK patent application (1321709.6).
    • Thermal Comfort and Energy: CFD, BES and Field Study in a British Open Plan Office with Displacement Ventilation

      Shahzad, Sally; Calautit, John Kaiser; Hughes, Ben; Brennan, John; Theodossopoulos, Dimitris; University of Derby; University of Sheffield; University of Edinburgh (2016)
      Energy efficiency and thermal comfort are necessary in designing the workplace. Accurate computational modelling and analysis methods are useful to improve the design, energy consumption and user’s comfort. This study compared the results of combined Computational Fluid Dynamics (CFD) and Building Energy Simulation (BES) with the contextual data collected through a Filed Study of Thermal Comfort (FSTC) regarding user comfort and energy in a workplace. The building was a six storey open plan office in Aberdeen, built in 2011, with displacement ventilation, “very good” BREEAM and “B” energy ratings. Each floor had 175 workstations, 1680m2 office area and approximately 3.5m2 per workstation. Thermal comfort surveys and environmental measurements were applied. The results were compared with the CFD modelling of the ventilation and thermal performance, PMV and BES energy predictions. The simulation results were in good agreement to that of the field data, indicating over 70% slightly cool and 25% neutral. The combination of CFD and BES improved the accuracy of the simulation and provided important information on optimising energy and the thermal environment. This combined simulation is useful and recommended in the design phase to achieve the balance of energy and comfort in the workplace.
    • Thermal comfort and indoor air quality analysis of a low-energy cooling windcatcher.

      Calautit, John Kaiser; Aquino, Angelo I.; Shahzad, Sally; Nasir, Diana S. N. M; Hughes, Ben Richard; University of Sheffield; University of Derby (Applied Energy, 2016)
      The aim of this work was to investigate the performance of a roof-mounted cooling windcatcher integrated with heat pipes using Computational Fluid Dynamics (CFD) and field test analysis. The windcatcher model was incorporated to a 5m x 5m x3 m test room model. The study employed the CFD code FLUENT 15 with the standard k-ɛ model to conduct the steady-state RANS simulation. The numerical model provided detailed analysis of the airflow and temperature distribution inside the test room. The CO2 concentration analysis showed that the system was capable of delivering fresh air inside the space and lowering the CO2 levels. The thermal comfort was calculated using the Predicted Mean Vote (PMV) method. The PMV values ranged between +0.48 to +0.99 and the average was +0.85 (slightly warm). Field test measurements were carried out in the Ras-Al-Khaimah (RAK), UAE during the month of September. Numerical model was validated using experimental data and good agreement was observed between both methods of analysis.
    • Transient performance investigation of different flow-field designs of automotive polymer electrolyte membrane fuel cell (PEMFC) using computational fluid dynamics (CFD)

      Choopanya, Pattarapong; Yang, Zhiyin; University of Derby, UK (International Centre for Heat and Mass Transfer (ICHMT)., 2014-07-14)
      Transient performance of a polymer electrolyte membrane (PEM) fuel cell in terms of the time-dependent current density profile that responds to the varying cell potential is of critical importance for an automotive PEM fuel cell. A step change in cell potential is applied to the cell terminals to simulate a sudden change in load demand due to an engine startup or very high acceleration. The transient responses of the three most commonly used flow-fields, namely, parallel, single-serpentine, and interdigitated designs in terms of the magnitude of current overshoot and time taken to adjust to the new equilibrium state are compared. The results suggest the serpentine flow-field outperforms its two counterparts as it balances the satisfactory transient performance with an expense of acceptable pressure drop across the cell and hence it is the most appropriate design to be used in automotive PEM fuel cells.