The effect of turbulent velocity fluctuations on the convective heat transfer to droplets subjected to evaporation and thermolysis

Guo, Ning; Finnerman, Oskar; Ström, Henrik

doi:10.1063/1.4951763

Cited by 3 publications

(3 citation statements)

References 8 publications

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“…T A is the external fluid temperature and T S is the solid surface temperature. In the actual convection heat transfer process in the fabric surface, there will be a great effect 29 : the temperature, humility and velocity of air near the fabric surface are changing all the time, especially in the stable drying period, and the drying rate reaches the maximum. 30,31 In this model, the effects of water evaporation are further considered; the temperature of the first layer grid in the fabric surface is adopted as the external fluid temperature and then this temperature is updated with time iteration, which further enhances the accuracy of the computing method of the convective heat transfer in the fabric surface…”

Section: Fabric Heat Transfer Modelmentioning

confidence: 99%

A numerical model of the open-width coupling drying process for cotton fabrics based on the theory of heat and mass transfer in porous media

Wang

Zhang

Chen

et al. 2019

Textile Research Journal

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In order to reveal the physical drying characteristics of various kinds of cotton fabrics and further provide theoretical guides for designing drying equipment and improving drying technologies, a finite element model is built that is able to describe coupling of the drying process between fabrics and environment. Specifically, three kinds of cotton fabrics mesoscopic structures parameters and mechanical properties are firstly measured and then these fabrics are equivalent to porous media, and the equivalent media can characterize the fabrics precisely. Then, the formulas for calculating the convection heat transfer and thermodynamic properties of fabrics are also improved and verified by corresponding experiments. The results shows that the improved formulas can calculate the properties more accurately. Next, we apply this model to analyze the regular change of surface temperature and water content with time during the drying process of three kinds of fabrics under different technologies. The results indicates that the coupled heat and mass transfer of drying processes are obviously affected by liquid phase transition. In addition, with higher wind temperature, the velocity of water evaporation inside fabrics is faster and, when water content inside fabric becomes lower in the drying process, the velocity of water evaporation decreases. The numerical values agrees well with the corresponding experimental values: The mean absolute error of water content inside fabric in the drying process is less than 1.51 g, while the average absolute error of fabric surface temperature is about 1.63℃, which means this model can precisely capture the coupling drying process of various kinds of cotton fabrics inside the oven. It is expected that the model can be applied for providing theoretical guidance for designing structures of drying equipment and improving drying technologies.

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Section: Fabric Heat Transfer Modelmentioning

confidence: 99%

A numerical model of the open-width coupling drying process for cotton fabrics based on the theory of heat and mass transfer in porous media

Wang

Zhang

Chen

et al. 2019

Textile Research Journal

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“…Guo et al (2015) performed numerical investigations of a urea-spray and found that failure to resolve the turbulent velocity fluctuations of the droplet phase may have significant effects on the rate of urea thermolysis and the temperature at which it occurs. Given the importance of turbulent fluctuations on the development of the urea spray (Berlemont et al , 1995; Ström et al , 2009), also the effects of the fluctuations on the turbulence-chemistry interaction could be expected to be significant.…”

Section: Introductionmentioning

confidence: 99%

Reactor modelling assessment for urea-SNCR applications

Finnerman

Razmjoo

Guo

et al. 2017

HFF

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Purpose-The work investigates the effects of neglecting, modeling or partly resolving turbulent fluctuations of velocity, temperature and concentrations on the predicted turbulencechemistry interaction in urea-SNCR systems. Design/methodology/approach-Numerical predictions of the NO conversion efficiency in an industrial urea-SNCR system are compared to experimental data. Reactor models of varying complexity are assessed, ranging from one-dimensional ideal reactor models to stateof-the-art CFD simulations based on the DES approach. The models employ the same reaction mechanism, but differ in the degree to which they resolve the turbulent fluctuations of the gas phase. A methodology for handling of unknown experimental data with regard to providing adequate boundary conditions is also proposed. Findings-One-dimensional reactor models may be useful for a first quick assessment of urea-SNCR system performance. It is critical to account for heat losses, if present, due to the significant sensitivity of the overall process to temperature. The most comprehensive DES setup evaluated is associated with approximately two orders of magnitude higher computational cost than the conventional RANS-based simulations. For studies that require a large number of simulations (e.g. optimizations or handling of incomplete experimental data), the less costly approaches may be favored with a tolerable loss of accuracy. Originality/value-Novel numerical and experimental results are presented to elucidate the role of turbulent fluctuations on the performance of a complex, turbulent, reacting multiphase flow.

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“…4 The authors investigate the effects of turbulent flows and flow velocities on convective heat transfer at individual droplets in a turbulent channel flow. 4 Numerical analysis 6 has shown that air parameters (velocity and temperature), as well as in Guo et al 7 fabric velocity, are the most influential parameters on the drying rate and fabric surface temperature in the continuous drying process. It is shown that optimal values of parameters can decrease energy usage by 27.8%.…”

mentioning

confidence: 99%

Temperature and density distribution in an industrial stenter frame based on three-dimensional numerical simulation

Ramić¹,

Dzaferovic

Kadric

et al. 2022

Textile Research Journal

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Drying of textiles in industrial facilities represents an energy-intensive process where a large number of measures for energy and production cost savings can be introduced. Typical measures include the introduction of energy management, waste-heat recovery, process optimization and so on. Drying is a complex process with coupled heat and mass transfer between the heated air and humid textile, where parameters such as the air flow rate, air velocity and its flow regime and textile velocity and water content represent significant influential factors. The distribution of air temperature and density inside the drying section of an industrial stenter frame is analyzed in detail using three-dimensional numerical simulation, where the textile is modeled as a porous medium to analyze moisture diffusion within the textile. Heated air is introduced into a chamber by inlet nozzles and removed by exit nozzles, the distribution of which is based on actual machine configuration. A humid textile is introduced into a section, where temperature and density distribution within the textile are calculated for selected time periods. During the simulation in the Fluent program, models of specific component transport, multiphase air flow, turbulent flow, porosity and evaporation were used. The results represent a valuable data set that provides an in-depth insight into the drying process in the industrial stenter machine.

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The effect of turbulent velocity fluctuations on the convective heat transfer to droplets subjected to evaporation and thermolysis

Cited by 3 publications

References 8 publications

A numerical model of the open-width coupling drying process for cotton fabrics based on the theory of heat and mass transfer in porous media

A numerical model of the open-width coupling drying process for cotton fabrics based on the theory of heat and mass transfer in porous media

Reactor modelling assessment for urea-SNCR applications

Temperature and density distribution in an industrial stenter frame based on three-dimensional numerical simulation

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