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    <title>Transport Research International Documentation (TRID)</title>
    <link>https://trid.trb.org/</link>
    <atom:link href="https://trid.trb.org/Record/RSS?s=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" rel="self" type="application/rss+xml" />
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    <language>en-us</language>
    <copyright>Copyright © 2026. National Academy of Sciences. All rights reserved.</copyright>
    <docs>http://blogs.law.harvard.edu/tech/rss</docs>
    <managingEditor>tris-trb@nas.edu (Bill McLeod)</managingEditor>
    <webMaster>tris-trb@nas.edu (Bill McLeod)</webMaster>
    <image>
      <title>Transport Research International Documentation (TRID)</title>
      <url>https://trid.trb.org/Images/PageHeader-wTitle.jpg</url>
      <link>https://trid.trb.org/</link>
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    <item>
      <title>Vehicle Defroster System Evaluation</title>
      <link>https://trid.trb.org/View/1787435</link>
      <description><![CDATA[Vehicle defrost systems are required to defrost the windshield and side windows in a short period. This portion of the HVAC system is not only required to work without interfering with operator comfort relating to high temperatures being felt by the drivers face, but also relating to noise. Add to these restrictions the requirement that the defrost outlets used must be esthetically pleasing, and one can see how much development time is required to design an effective defrost system. Once a design is established, it must be tested. The methods currently used to test defrost performance leaves much to be desired, due to the time required to transpose actual test results into usable data. This transposition includes removing marked tracing from the windows in a cold chamber to trace paper, and then the trace paper needs to be reduced into manageable sizes of paper. It is for these reasons that a more cost effective, accurate, consistent, and time efficient method using digital photography was created.]]></description>
      <pubDate>Mon, 13 Jan 2025 11:12:03 GMT</pubDate>
      <guid>https://trid.trb.org/View/1787435</guid>
    </item>
    <item>
      <title>LC³ cementitious binder incorporating microencapsulated phase change materials for self-defrosting traffic surfaces</title>
      <link>https://trid.trb.org/View/2444531</link>
      <description><![CDATA[Exposed surfaces of bridge decks, viaducts and pavements incur ice formation and accumulation of snow in cold seasons, which threatens traffic safety. Mitigating this problem using traditional methods such as deicing salts have caused ecosystem damage and inflicted substantial reinforcement corrosion and surface scaling to bridge decks and pavements, thus compromising their service life and causing colossal economic loss. This paper presents an alternative solution to overcome this problem through the development of a sustainable LC³ cementitious material incorporating micro-encapsulated phase change material (MEPCM) with low phase transition temperature to delay the surface temperature drop and mitigate snow accumulation and ice formation. MEPCM was incorporated in the cementitious matrix at 0 %, 10 % and 20 % by binder mass. Paste and mortar mixtures were prepared to investigate the microstructural, mechanical, physical, and thermal properties. Test results showed that incorporating MEPCM in the LC³ matrix achieved adequate compressive strength. Thermal simulations and visual observations conducted on mortar samples in the laboratory and outdoor exposure showed that MEPCM can effectively regulate the surface temperature of the LC³ matrix and mitigate temperature drops as well as snow accumulation. Analysis of temperature data in the 2023–2024 winter season of Hamilton, Ontario, Canada indicated that the MEPCM incorporated in mortar samples could effectively regulate 40 % of the total days considered and mitigate surface ice formation and snow accumulation, which provides both economic and environmental benefits.]]></description>
      <pubDate>Fri, 15 Nov 2024 09:47:32 GMT</pubDate>
      <guid>https://trid.trb.org/View/2444531</guid>
    </item>
    <item>
      <title>Investigations of Automotive Defroster and Windshield Flow</title>
      <link>https://trid.trb.org/View/1792106</link>
      <description><![CDATA[The specification of automotive ventilation / defrosting systems has often utilized “trial-and-error” and “prior experience” techniques. But design development and production efficiency has generated a strong interest in using more sophisticated design tools such as computational fluid dynamics. For this purpose a joint experimental and numerical study was undertaken. This comprehensive investigation was divided into two parts. First, the three dimensional defroster flow field was measured using LDA in an actual automobile. Second, LDA and infrared thermography was used to map the flow and temperature fields for a two dimensional jet impinging upon a slanted plate -- a simplified representation of a car defroster geometry.]]></description>
      <pubDate>Mon, 11 Mar 2024 09:08:58 GMT</pubDate>
      <guid>https://trid.trb.org/View/1792106</guid>
    </item>
    <item>
      <title>Temperature Measurement of a Vehicle's Windshield Using Liquid Crystals</title>
      <link>https://trid.trb.org/View/2307223</link>
      <description><![CDATA[The impingement of air jets on a vehicle's windshield is one parameter that determines the effectiveness of the defroster's system in freeing the windshield of frost and fog. Incompressible air jets impinge upon the inner surface of the windshield and create hydrodynamic and thermal boundary layers which in turn control convective heat transfer. Therefore, understanding the heat transfer interaction between impinging air jets and an inclined windshield is of practical relevance. Experimental investigations on the temperature distribution are performed on the inner surface of the windshield for the purpose of obtaining local and average heat transfer coefficients. In this paper, the temperature distribution of a vehicle's windshield is investigated using liquid crystals. As a result, a temperature contour map is generated displaying local temperature values on the inner surface of the windshield. The strongly non-uniform air velocities at the defroster's nozzles are also measured for both the driver's and the passenger's sides.]]></description>
      <pubDate>Wed, 17 Jan 2024 16:40:42 GMT</pubDate>
      <guid>https://trid.trb.org/View/2307223</guid>
    </item>
    <item>
      <title>Development of a Novel Methodology in Predicting Transient Deicing Simulation of an Automotive Windshield</title>
      <link>https://trid.trb.org/View/2061015</link>
      <description><![CDATA[With the growing demand in passenger comfort and enhanced safety and high competitiveness in the automotive segment, automotive manufacturers are keen to launch the product flawlessly within short period of time. In that regard one of the areas related to safety of passengers which is windshield deicing, requires lot of attention and to be developed and certified well before the product launch. Computational fluid dynamics (CFD) helps in this regard to come up quickly with a feasible design solution. But with the conventional method of doing deicing requires lot of time and high cell count. Hence there is a requirement of developing a methodology which will shorten the simulation time and thus leading to shorter development time. One such development took place is in the multiphase models in CFD.The present study focuses in introducing a novel methodology for predicting the transient deicing pattern in an automotive windshield. Simcenter STAR-CCM+ version 2021.2.1 was used for the analysis. The new method integrated two multiphase models ‘Fluid Film Melting and Solidification’ and ‘Volume of Fluid (VOF)’. The ice-water region on the windshield, taken as 3D shell, was modeled as a Fluid Film model whereas the ambient air region outside the vehicle in-contact with the ice-water layer was modeled as Volume of Fluid. A multiphase interaction was created between them. The primary application of this phase interaction model was to ensure when a fluid film can accumulate in particular areas of the geometry to form pools. In those areas, the accumulated fluid was modeled as a VOF phase rather than as a fluid film. The new methodology was correlated with the conventional methodology where the ice-water layer was modeled as 3D solid under the multiphase model of ‘Volume of Fluid’. The new methodology was found to reduce the mesh count by 45% of the original, leading to a reduction of computational time to a near 30%. The simulation results also found to be a near exact with transient ice pattern observed from wind-tunnel test result.]]></description>
      <pubDate>Mon, 21 Nov 2022 16:19:21 GMT</pubDate>
      <guid>https://trid.trb.org/View/2061015</guid>
    </item>
    <item>
      <title>Improving Defrost Performance through Design Change in Simulation and Validating through Experimental Analysis</title>
      <link>https://trid.trb.org/View/2061052</link>
      <description><![CDATA[Vehicles wind shield are designed to provide a clear visibility in winter as it is one of the most important requirement for the comfortable and safe journey. In extreme winters, wind shield of vehicle is covered with layer of ice and if frosted happened, results in reduces the visibility distance. To increase the visibility and providing the comfort to driving the vehicle, heater is used in vehicle as an integrated part of vehicle HVAC System. When the blower air passes through heater, air temperature gets increased. When the hot air is injected through grill at designed angle of injection and at selected air velocity on wind shield surface, ice on wind shield melting due to convection heat transfer phenomenon and thus achieved a clear windshield glass and clear visibility at driver and at co-driver area. The objective of this paper is to optimize the design of Vehicle DUCT to improve the visibility within required timeline at driver and co-driver area under required environment conditions. Computational fluid dynamics have been carried to get the optimum design under road load and environment conditions. To verify the improvement in design, experimental testing has been carried out under same environment load conditions. CFD analysis has been done for airflow distribution and from CFD results HVAC duct vent location has been changed During the experimental test, recorded the impact of hot air injection on wind shield, defrost performance, climate control chamber condition and vehicle cabin area. Experimental studies were carried out under ambient temperature of -10°C and 800gms of water was used to frosting of windshield. Post analysis, numerical results were compared with experimental results and found good correlations between CFD and Testing results.]]></description>
      <pubDate>Mon, 21 Nov 2022 16:19:21 GMT</pubDate>
      <guid>https://trid.trb.org/View/2061052</guid>
    </item>
    <item>
      <title>Computational Investigation for Flow and Heat Transfer Characteristics of Automobile Windshield with Impinging Slot Jets</title>
      <link>https://trid.trb.org/View/1826100</link>
      <description><![CDATA[A computational study is reported on flow and heat transfer from single row of slot air jets impinging on an automobile windshield surface. The effects of jet-to-jet spacing and jet exit to windshield spacing are computationally analyzed for a three values of Reynolds number. There is a significant variation in pressure and heat transfer along the stagnation zone and the entire windshield surface for all the configurations tested. It is observed that the average heat transfer in the stagnation zone reduces by about 9 % when c/d is increased from 2 to 4. However the average heat transfer for the entire windshield increases with c/d as well as h/d. The maximum increase is average heat transfer for the entire windshield is found to be 33% for the case with c/d=4, h/d=5.6 than that of the case with c/d=2, h/d=3.6.]]></description>
      <pubDate>Fri, 17 Jun 2022 09:04:22 GMT</pubDate>
      <guid>https://trid.trb.org/View/1826100</guid>
    </item>
    <item>
      <title>An Inverse Design Method for Windshield Defrosting-Demisting Performance Using Machine Learning Techniques.</title>
      <link>https://trid.trb.org/View/1765345</link>
      <description><![CDATA[As vehicle electrification progresses, physical spaces inside instrumental panel for a defroster nozzle become narrower and nozzle sizes are required to reduced. Under such constraint conditions, it is important to design a defroster nozzle, satisfying requirements of windshield defrosting-demisting performance with low costs. In this paper, a reduced order model (ROM) is developed to predict instantly windshield velocity distribution, namely windshield defrosting-demisting performance. An inverse design method utilizing decision tree algorithm and ROM is established to find out instantly design conditions of defroster nozzle that fulfill performance requirements. Effectiveness of the method is validated by CFD performance results of a small defroster nozzle derived from the method results.]]></description>
      <pubDate>Sun, 28 Feb 2021 16:51:05 GMT</pubDate>
      <guid>https://trid.trb.org/View/1765345</guid>
    </item>
    <item>
      <title>Parametric Modelling and Performance Analysis of HVAC Defroster Duct Using Robust Optimization Methodology</title>
      <link>https://trid.trb.org/View/1702245</link>
      <description><![CDATA[Nowadays development of automotive HVAC is a challenging task wherein thermal comfort and safety are very critical factors to be met. HVAC system is responsible for the demisting and defrosting of the vehicle’s windshield and for creating/maintaining a pleasing environment inside the cabin by controlling airflow, velocity, temperature and purity of air. Fog or ice which forms on the windshield is the main reason for invisibility and leads to major safety issues to the customers while driving. It has been shown that proper clear visibility for the windshield could be obtained with a better flow pattern and uniform flow distribution in the defrost mode of the HVAC system and defrost duct. Defroster performance has received significant attention from OEMs to meet the specific global performance standards of FMVSS103 and SAE J902. Therefore, defroster performance is seriously taken into consideration during the design of HVAC system and defroster duct.         The HVAC unit provides hot air to the defroster duct which is blowing high velocity air to the windscreen to clear the frosting. Currently as a traditional defrost duct design process, multiple flow simulation needs to be carried out for various design configurations of defrost duct through CFD analysis until the performance targets are achieved during the design cycle and it is very time consuming. In this paper, the focus is to develop defrost duct modelling using parameterization technique and optimize the defrost duct system to meet the performance requirements through robust optimization Design for Six Sigma (DFSS) methodology to reduce the design time, cost, size and weight of the system. Parametric modelling technique is used for designing the defrost duct through design software to reduce the design time for simulation. A 3-dimensional model (3D) of a car cabin with full a HVAC system was developed using Star-CCM+® to predict the performance of the system in the windshield. DFSS methodology helps in finding out the optimized design factors of defrost duct to meet the performance targets such as pressure drop, airflow and velocity at windshield aim points simultaneously. The optimized defrost duct design results were compared with the baseline defrost duct design results and the improvement in performance results is achieved by more than 60%.       ]]></description>
      <pubDate>Fri, 29 May 2020 09:47:16 GMT</pubDate>
      <guid>https://trid.trb.org/View/1702245</guid>
    </item>
    <item>
      <title>Development of the Defrost Performance Evaluation Technology in Automotive Using Design Optimization Analysis Method</title>
      <link>https://trid.trb.org/View/1701242</link>
      <description><![CDATA[In this study, we developed the defrost performance evaluation technology using the multi-objective optimization method based on the CFD. The defrosting is one of the key factors to ensure the drivers’ safety using the forced flow having proper temperature from HVAC during drive. There are many factors affecting the defrost performance, but the configurations of guide-vane and discharge angles in the center DEF(defrosting) duct section which are main design factors of the defrost performance in automotive, so these were set to the design parameters for this study. For the shape-optimization study, the discharge mass flow rate from the HVAC which is transferred to the windshield and the discharge areas in the center defrost duct were set to the response parameters. And then, the standard deviation value of mass flow rate on the selected discharge areas checking the uniformity of discharge flow was set to the objective function to find the optimal design. The results on the windshield from optimization analysis were quantified from some kind of standards to evaluate the defrost performance, in particular, the important parts on it to secure the drivers’ safety as specified FMVSS103, to which the weighted value has been assigned. From this process, it is possible to quantify the defrost performance with various automotive models, and to find the optimized design. In case of using these methods, it is possible to reduce the calculation time, and to effectively analyze the results by controlling the design parameters systematically. These methods also make it possible to check the performance rapidly, and to propose the optimal design through the analytical verifications at the initial design stage.       ]]></description>
      <pubDate>Thu, 30 Apr 2020 17:26:25 GMT</pubDate>
      <guid>https://trid.trb.org/View/1701242</guid>
    </item>
    <item>
      <title>Development of CFD Program for Automotive Ventilation and Defrost Simulation Using OpenFOAM</title>
      <link>https://trid.trb.org/View/1701241</link>
      <description><![CDATA[Numerical simulations are widely used to predict the performance of products in the automotive development process. In particular, ventilation and defrost performances of automotive HVAC system are developed according to design variables and environmental conditions based on CFD (Computational Fluid Dynamics). Recently, as improvement on both computer hardware performance and analysis technology continues, the usage of simulation has been increasing accordingly. However, the cost of software license also increases in such development environments. In this paper, we introduce our CFD program with OpenFOAM, which is the free, open source CFD software, to simulate flow characteristics of ventilation and defrost in automobile. This program includes self-developed GUI similar to commercial CFD code, two-layer realizable ?-e turbulence model to secure numerical stability, and fluid film model to check the defrost phenomena with time dependence from OpenFOAM libraries.       ]]></description>
      <pubDate>Thu, 30 Apr 2020 17:26:25 GMT</pubDate>
      <guid>https://trid.trb.org/View/1701241</guid>
    </item>
    <item>
      <title>Implementation of Reinforcement Learning on Air Source Heat Pump Defrost Control for Full Electric Vehicles</title>
      <link>https://trid.trb.org/View/1561498</link>
      <description><![CDATA[Air source heat pumps as the heating system for full electric vehicles are drawing more and more attention in recent years. Despite the high energy efficiency, frost accumulation on the heat pump evaporator is one of the major challenges associated with air source heat pumps. The evaporator needs to be actively defrosted periodically and heat pump heating will be interrupted during defrosting process. Proper defrost control is needed to obtain high average heat pump energy efficiency. In this paper, a new method for generating air source heat pump defrost control policy using reinforcement learning is introduced. This model-free method has several advantages. It can automatically generate optimal defrost control policy instead of requiring manually determination of the control policy parameters and logics. More measurement results can be incorporated into the defrost control policy without too many changes in the reinforcement learning algorithm so that the control policy can be better optimized under wider range of working conditions. The learning features also enable the controller to adapt to the system differences and changes which are impossible to predict a priori when designing defrost control policy. The algorithm was validated using experimentally obtained heating capacity and COP data in frost growth cycle of a heat pump under different conditions. The results showed that reinforcement learning can be used to generate defrost control policy that optimizes energy consumption for various working conditions.       ]]></description>
      <pubDate>Fri, 20 Mar 2020 16:26:12 GMT</pubDate>
      <guid>https://trid.trb.org/View/1561498</guid>
    </item>
    <item>
      <title>Windshield Defrosting Analysis: A Numerical and Experimental Approach</title>
      <link>https://trid.trb.org/View/1660475</link>
      <description><![CDATA[The outside visibility through the windshield and ORVM visibility through the side glasses are critical for safe driving. The frost deposition on the Windshield and side glasses in the cold climatic condition impairs the outside and ORVM visibility during driving and hence leads to an unsafe driving condition. In India, the regulation AIS-084 governs the defrosting standard. The defrosting performance evaluation by testing cannot be performed at concept stage when the vehicle prototype is not available. It also increases the cost of vehicle development due to increase in the number of prototype used for testing.         This paper explains about the in-house developed CFD methodology to evaluate the windshield defrosting performance of the vehicle in the concept stage when no vehicle proto is available and cost of countermeasure for defrosting performance improvent is very less. This methodology is implemented for some of the existing models. The results of CFD simulations are compared to the experimental data using a correlation study and the correlation coefficient of numerical and experimental measurements were reported. CFD simulation was in good agreement with the experimental study and the so development CFD methodology is further used for design parameter studies.       ]]></description>
      <pubDate>Fri, 21 Feb 2020 10:24:25 GMT</pubDate>
      <guid>https://trid.trb.org/View/1660475</guid>
    </item>
    <item>
      <title>HVAC Defrost System Assessment through 1D and 3D Simulation during Concept Development</title>
      <link>https://trid.trb.org/View/1598817</link>
      <description><![CDATA[The windshield defrosting performance is a very important requirement for the vehicle safety because it affects directly the driver’s visibility during driving. The defrosting process in the vehicle is carried out by blowing hot air from the HVAC (Heating Ventilation and Air conditioning) through the defrost duct system. Computational Fluid Dynamics (CFD) is used to numerically simulate the vehicle defroster performance with the available defrost duct outlet temperature and coolant temperature data from the vehicle testing. This paper describes the 1D modelling of complete HVAC system configuration to find out the defrost duct outlet temperature and through the CFD, transient defrost simulation was carried out to simulate the ice melting process over the windshield at various time step. In the CFD simulation, shell modelling analysis method is followed to predict the de-icing phenomenon over the vehicle windshield. The validation results are presented by comparing the CFD predicted windshield de-icing patterns with the windshield de-icing tunnel test. The present CFD windshield de-icing simulations demonstrated reasonable agreement with available test data within the error of 10%. The prediction of defrost duct outlet temperature through 1D simulation numerical method will aid in getting the results quickly without carrying out the vehicle testing during early design cycle. By employing this methodology, CFD simulation results could be analyzed and it helps to optimize the defrost duct in a robust way during the early design stages of the program.       ]]></description>
      <pubDate>Tue, 20 Aug 2019 11:44:39 GMT</pubDate>
      <guid>https://trid.trb.org/View/1598817</guid>
    </item>
    <item>
      <title>Sensitivity Analysis of Windshield Defrost Characteristics Impact on Occupant Thermal Comfort</title>
      <link>https://trid.trb.org/View/1461914</link>
      <description><![CDATA[During cabin warm-up, effective air distribution by vehicle climate control systems plays a vital role. For adequate visibility to the driver, major portion of the air is required to be delivered through the defrost center ducts to clear the windshield. HVAC unit deliver hot air with help of cabin heater and PTC heater. When hot air interacts with cold windshield it causes thermal losses, and windshield act as sink. This process may causes in delay of cabin warming during consecutive cabin warming process. Thus it becomes essential to predict the effect of different windscreen defrost characteristics. In this paper, sensitivity analysis is carried for different windscreen defrosts characteristics like ambient conditions, modes of operation; change in material properties along with occupant thermal comfort is predicted. An integrated 1D/3D CFD approach is proposed to evaluate these conditions. Detailed thermal boundary conditions are considered in 1D heat transfer method and coupled with 3D convection human comfort model.       ]]></description>
      <pubDate>Mon, 25 Sep 2017 14:09:18 GMT</pubDate>
      <guid>https://trid.trb.org/View/1461914</guid>
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