scholarly journals Modelling investigation of water droplet evaporative freezing in artificial snowmaking

2019 ◽  
Vol 128 ◽  
pp. 06013
Author(s):  
Georges El Achkar ◽  
Aiqiang Chen ◽  
Rachid Bennacer ◽  
Bin Liu
Keyword(s):  
Heat Transfer ◽  
Numerical Model ◽  
Relative Humidity ◽  
Air Temperature ◽  
Water Droplet ◽  
Theoretical Models ◽  
Comsol Multiphysics ◽  
Initial Diameter ◽  
Air Space ◽  
Mass And Heat Transfer

In this paper, a modelling investigation of water droplet evaporative freezing was conducted in order to better understand the snowmaking process and hence to optimise the design of the artificial snowmaking device. To this end, mass and heat transfer theoretical models of a single water droplet cooling in an air space were established and implemented in a numerical model developed using the software COMSOL Multiphysics. The effects of the air temperature, relative humidity and velocity and the water droplet initial diameter and temperature on this process were identified and analysed, and their appropriate ranges for the snowmaking were determined.

The Catalytic Hydrogenation of Aromatic Nitro Ketone in a Microreactor: Reactor Performance and Kinetic Studies

2009 ◽  
Vol 6 (1) ◽  
Author(s):  
Sunitha Tadepalli ◽  
Adeniyi Lawal
Keyword(s):  
Heat Transfer ◽  
Catalytic Hydrogenation ◽  
Kinetic Studies ◽  
Theoretical Models ◽  
Packed Bed ◽  
Rate Equations ◽  
Batch Reactors ◽  
Reactor Performance ◽  
Mass And Heat Transfer ◽  
Aromatic Nitro

Catalytic hydrogenation of nitro aromatics is an important class of reactions in the pharmaceutical and fine chemical industries. These reactions are extremely fast and highly exothermic in nature; hence, mass and heat transfer limitations play an important role when these reactions are conducted in conventional batch reactors. The use of a micro-channel reactor for such reactions provides improved mass transfer rates which may ensure that the reaction operates close to intrinsic kinetics. In the present study, the hydrogenation of a model aromatic nitro ketone was conducted in a packed-bed microreactor. The effects of different processing conditions were studied using 5%Pd/Alumina catalyst, viz.: hydrogen pressure, substrate concentration, temperature, and residence time on the conversion of substrate, Space Time Yield (STY), and selectivity of product. Internal and external mass and heat transfer limitations in the microreactor were examined. The kinetic study was undertaken in a differential reactor mode, keeping the conversion of the reactant at less than 10%. The overall reaction was treated as comprising two separate reactions: first, the reduction of the nitro compound to hydroxylamine and then, the reduction of the hydroxylamine to amine. Two rate equations for the two consecutive reactions assuming the Langmuir-Hinshelwood mechanism provided the best fit to the experimental data. These two rate equations predicted the experimental rates satisfactorily and the differences were within 10% error. Experiments were also carried out in an integral reactor, and the reactor performance data were found to be in agreement with the predictions of the theoretical models.

scholarly journals Agglomeration process in the fluidized bed, the effecting parameters and some applications

2018 ◽  
Vol 13 (3-4) ◽  
pp. 159-163
Author(s):  
Hira Yuksel ◽  
Nur Dirim
Keyword(s):  
Heat Transfer ◽  
Fluidized Bed ◽  
Air Temperature ◽  
Mechanical Resistance ◽  
High Porosity ◽  
Air Velocity ◽  
Mixing Rate ◽  
Agglomeration Process ◽  
Mass And Heat Transfer ◽  
Bed Agglomeration

The agglomeration process has been commonly used to improve the functional properties of powder products to form larger agglomerates. Agglomeration provides a granular structure to powders, reduce the dusting and improving their characteristics, such as storage stability, wettability, dispersibility, and solubility. This process can be performed by different methods, one of which is fluidized bed agglomeration widely used in food processing since the agglomerates produced by this technique have high porosity, low density, and good mechanical resistance. At the same time, this process is influenced by many factors; e.g., inlet air temperature, air velocity, mixing rate, and properties of the binder agents. Inlet air temperature affects the mass and heat transfer; air velocity prevents caking and accelerates mass and heat transfer; mixing rate allows mixing the binder agent uniformly over the particles; and the properties of the binder agent, such as concentration and viscosity have an impact on the properties of the final product. These four factors should be well known and controlled so that the agglomerates produced have the desired properties. Furthermore, the use of fluidized bed agglomeration results in products that can be used in widespread areas and in high quantities, and this method also creates the opportunity to utilize excess foods not consumed.

scholarly journals Climatic Issue in an Advanced Numerical Modeling of Concrete Carbonation

2021 ◽  
Vol 13 (11) ◽  
pp. 5994
Author(s):  
Viet Duc Ngo ◽  
Ngoc Tan Nguyen ◽  
Frédéric Duprat ◽  
Ngoc Tru Vu ◽  
Viet Phuong Nguyen
Keyword(s):  
Heat Transfer ◽  
Carbon Dioxide ◽  
Numerical Model ◽  
Relative Humidity ◽  
Research Work ◽  
Mass Conservation ◽  
Climatic Variables ◽  
Experimental Investigations ◽  
Concrete Carbonation ◽  
Wide Range

Damage in reinforced concrete structures is frequently caused by reinforcement corrosion due to carbonation. Although a wide range of literature contributed to the concrete carbonation consisting of experimental investigations and numerical simulations, research work on a complete numerical model for concrete carbonation prediction with integrated climatic variables (e.g., temperature, relative humidity) is still a challenge. The present paper aims to propose an advanced numerical model to simulate the penetration of carbon dioxide and moisture, diffusion of calcium ions, heat transfer, and porosity modification in concrete material using COMSOL Multiphysics software. Three coupled mass conservation equations of calcium, water, and carbon dioxide are solved together with additional equations regarding the heat transfer, variation of porosity, and content of portlandite and other hydrates and calcites. In this study, the actual temporal variabilities of temperature and relative humidity in Toulouse, France, are used as a case study. The predicted results of portlandite profiles and carbonation depth are compared with the experimental data and discussed to identify the effect of climatic variables on the concrete carbonation.

scholarly journals Avaliação do BRAMS na Previsão Numérica de Temperatura e Umidade Relativa do Ar para o Estado da Paraíba (Evaluation of BRAMS in Numerical Prediction of Temperature and Relative Humidity in State of Paraiba)

2011 ◽  
Vol 4 (3) ◽  
pp. 463
Author(s):  
Everson Batista Mariano ◽  
Enilson Palmeira Calvacanti ◽  
Herika Pereira Rodrigues
Keyword(s):  
Numerical Model ◽  
Relative Humidity ◽  
Air Temperature ◽  
Atmospheric Model ◽  
Model System ◽  
Numerical Prediction ◽  
Regional Atmospheric Model ◽  
Regional Atmospheric Model System ◽  
Weather Stations ◽  
Almost All

Neste trabalho foram avaliadas as previsões numéricas feitas pelo modelo numérico Brazilian Developments on the Regional Atmospheric Model System – BRAMS conforme execução em produção na UFCG. Foram analisadas as variáveis meteorológicas: temperatura do ar e umidade relativa do ar em superfície. A comparação foi feita com dados coletados em 19 estações meteorológicas automáticas, espalhadas pelos estados da Paraíba, Pernambuco e alagoas, pertencentes ao Instituto Nacional de Meteorologia - INMET. Os resultados mostram que os valores de temperatura do ar observados e estimados pelo modelo BRAMS mostram-se satisfatórios para até 5 dias em quase todas as localidades. As diferenças entre o observado e o estimado pelo modelo BRAMS, para a umidade relativa do ar, foram menos evidentes em comparação com a temperatura do ar. Palavras-Chaves: BRAMS, Dados Observados, Temperatura, Umidade Relativa.    Evaluation of BRAMS in Numerical Prediction of Temperature and Relative Humidity in State of Paraiba    ABSTRACT In this work we evaluate the predictions made by numerical model Developments on the Brazilian Regional Atmospheric Model System - BRAMS as implemented in production at the UFCG. We analyzed the meteorological variables: air temperature and relative humidity at the surface. The comparison was made with data collected from 19 automatic weather stations, scattered over the states of Paraiba, Pernambuco and Alagoas, belonging to the National Institute of Meteorology - INMET. The results show that the values of air temperature observed and predicted by the model BRAMS was satisfactory for up to 5 days in almost all locations. The differences between the observed and estimated by the model BRAMS, for relative humidity were less evident in comparison with the air temperature.  Keywords: BRAMS, Observed Data, Temperature, Relative Humidity.

scholarly journals Fast Heating Model for the Aircraft Cabin Air

Energies ◽  
2019 ◽  
Vol 12 (18) ◽  
pp. 3565 ◽  
Author(s):  
Zhi Yang ◽  
Zhengwei Long ◽  
Guangwen Wang
Keyword(s):  
Heat Transfer ◽  
Numerical Model ◽  
Temperature Gradient ◽  
Air Temperature ◽  
Environmental Control ◽  
Thermal Environment ◽  
Heating Process ◽  
Fast Heating ◽  
Aircraft Cabin ◽  
Heating Model

Maintaining a suitable cabin air temperature distribution is essential for providing an acceptable thermal environment for passengers and crew. However, cabin air may be very cold for the first flight in winter morning. It could be difficult to heat quickly the cabin air and to maintain an acceptable temperature gradient before boarding with the existing environmental control system. This study developed numerical model for predicting the heating process that coupled airflow and heat transfer in a cabin. The model was validated by using the experimental data obtained from an MD-82 airliner. With the validated numerical model, this investigation proposed to use an electric blanket to heat cabin air quickly and to reduce the air temperature gradient.

scholarly journals Effect of relative humidity on heat transfer across the surface of an evaporating water droplet in air flow

2009 ◽  
Vol 624 ◽  
pp. 57-67 ◽  
Author(s):  
RYOICHI KUROSE ◽  
AKITOSHI FUJITA ◽  
SATORU KOMORI
Keyword(s):  
Heat Transfer ◽  
Relative Humidity ◽  
Heat Loss ◽  
Water Droplet ◽  
Rear Surface ◽  
Ambient Air ◽  
Droplet Surface ◽  
Droplet Temperature ◽  
Humidity Condition ◽  
Evaporation Heat

A three-dimensional direct numerical simulation (DNS) is applied to flows inside and outside an evaporating spherical water droplet in air, and the effect of relative humidity on the heat transfer between the droplet and ambient air is investigated. The initial air temperature is set to be 15 K higher than the initial droplet temperature. The results show that the local evaporation heat loss indicates the maximum on the front of the droplet and decreases on going from the front to the rear, and the reduction on the rear becomes marked for high-droplet Reynolds numbers. This is because the evaporation rate is suppressed on the rear surface by the presence of flow separations behind the droplet. The droplet temperature decreases in the low-humidity condition, whereas it increases in the high-humidity condition. This difference is caused by the heat balance of evaporation heat loss and convective heat gain from ambient air at the droplet surface.

scholarly journals Simulation of Thermal Transfer Through the Polyamide Intake Manifold

2019 ◽  
Vol 56 (1) ◽  
pp. 190-193
Author(s):  
Corneliu Birtok-Baneasa ◽  
Adina Budiul-Berghian ◽  
Virginia Ana Socalici ◽  
Robert Bucevschi
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Boundary Layer ◽  
Numerical Model ◽  
Air Temperature ◽  
Wall Temperature ◽  
Thermal Boundary Layer ◽  
Intake Manifold ◽  
Thermal Transfer ◽  
Steady Heat

The aim of the present study is to model the steady heat transfer of the engine polyamide intake manifold. Under the condition of a steady flow, the intake manifold wall temperature and the intake air temperature were measured to examine the effect of the thermal boundary layer on the heat transfer. Experimental data is used to generate the numerical model of airflow simulation through the intake manifold.

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