• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.4
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• pp.88-96
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• 2008

Effects of the duct inlet guide vane on the flowrate distribution characteristics of the defroster nozzle exit in a defrost duct system were investigated experimentally to design the optimum heating, ventilation and air conditioning (HVAC) system applied in an automotive compartment. A 3-dimensional hot-wire anemometer system was used to measure the velocity field in the vicinity of the defroster nozzle jet flow and the velocity distributions near the windshield interior surface. At first, two cases of with- and without-duct inlet guide vanes were considered as the test condition, and then three cases of the duct inlet guide vane were tested to determine the optimum guide vane shape and their positions. The arrangement of the duct inlet guide vanes has an effect on the improved flowrate distribution at the defroster nozzle exit and near the windshield interior surface. However, the application of the lots of guide vane to control the flow direction leads to increase the flow resistance, resulting in the decreased flowrate issuing from the defroster nozzle. The shape of the duct inlet guide vane affects not only the flowrate distribution between the driver side and the assistant driver side but also the reduction of the flow resistance in the defrost duct system.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.12
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• pp.789-794
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• 2008

Recently, much attention has been paid in the field of defrosting because clear windshield in vehicle without effecting the thermal comfort is realized essentially. Then in winter, defrosting performance is one of the important factors in vehicle design to make certain driver's view. In this study, the velocity profile, temperature distribution and frost melting pattern on the windshield screen have been predicted in three dimensional geometry of an automobile interior. Numerical analyses predict a detailed description of fluid flow and temperature patterns on the inside windshield screen, utilizing the flow through defroster nozzle. Numerical prediction established a good defrosting performance with the standard distance ratio and the defroster nozzle angle ranging from $30^{\circ}$ to $40^{\circ}$, which satisfy the condition of National Highway Traffic Safety Administration (NHTSA) completely.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.5
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• pp.1-8
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• 2007

The present research is based upon the numerical analysis of a car windshield in order to represent the optimum design guide to improve the overall defrosting performance of the system. First, the control factors that highly affect the defrosting performance of a car windshield are chosen and afterwards, the optimum variables of each control factor are extracted out to analyze its performance. The main control factors for this research are respectively, the air injection angle of a defroster nozzle, the height of a nozzle outlet, and the ratio of the width to the height of a nozzle outlet. For such case when the air inlet angle is relatively small, the flow near the vicinity of the inner face of a windshield tends to expand. As a consequence, the heat transfer rate through the windshield decreases. Also, the height of a nozzle outlet is recommended to maintain its size to minimum. However, when the ratio mentioned before is designed less than unity, the defrosting performance decreases.

• Journal of Energy Engineering
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• v.19 no.3
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• pp.151-155
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• 2010

Adequate visibility through a vehicle windshield and frost melting period are critical aspects of major design parameters. To make progress in this area, a good understanding of the flow behavior and heat transfer characteristics produced by the HVAC module is required. The computational study was used to perform the parametric investigation into the defroster nozzle's performance with a full-scale model. The study highlights the drawbacks of current designs and points the way to improve passive defrosting mechanism. The results show that the current design of the defroster nozzles deliver the maximum airflow in the vicinity of the lower part of the windshield, which yields unsatisfactory visibility. Defrosting performance was excellent when the injection angle of the defrost nozzle was 45 degree. The numerical analysis satisfies the criteria provided by NHTSA.

• 한국전산유체공학회:학술대회논문집
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• 2005.10a
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• pp.75-80
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• 2005

The present work was undertaken to numerically analyze the defrosting phenomena of windshield glass. In order to analysis the phase change from frost to water on windshield glass by discharging hot air from a defroster nozzle, the flow and the temperature field of the cabin interior, the heat transfer through the windshield glass, and the phase change of frost should be solve simultaneously. In the present work, the flow field was obtained by solving 3-D incompressible Navier-Stokes equations, and the temperature field was computed from the incompressible energy equation. The phase change process was solved by the enthalpy method. For the code validation, the temperature and the phase change of the driven cavity were calculated. The calculation showed a good agreement with other numerical results. Then, the present code was applied to the defrosting problem of a real automobile, and a good agreement with the experimental data was also obtained.