scholarly journals Influence of air layer on temperature and humidity characteristics of outer envelope structure with internal heat insulation

2021 ◽  
Vol 48 (2) ◽  
pp. 81-91
Author(s):  
S. S. Dobrosmyslov ◽  
N. N. Rozhkova ◽  
A. F. Rozhkova ◽  
M. A. Perkova ◽  
S. A. Aliev
Keyword(s):  
Mass Transfer ◽  
Thermal Resistance ◽  
Heat And Mass Transfer ◽  
Heat Insulation ◽  
Internal Heat ◽  
Wall Structure ◽  
Airflow Rate ◽  
Outer Envelope ◽  
Air Movement ◽  
Condensate Formation

Objective. The article addresses the process of heat and mass transfer in outer envelope structure with internal heat insulation. To prevent condensate formation, it is proposed to use a ventilated air duct inside the wall structure. Methods. The study was carried out using numerical simulation methods. Air movement in the duct was described by solving the Navier-Stokes equation in k-ε approximation. Condensate formation was analysed via joint resolution of heat conduction and diffusion equations. The problem of heat and mass transfer was addressed for a structure with internal heat insulation, behind the layer of which an air duct was located with air movement occurring due to natural or forced convection. Results. As part of the work, it was shown that the use of an air duct significantly reduces the thermal resistance of the structure, and an increase in the airflow rate leads to a decrease in thermal resistance and the likelihood of condensate formation. A decrease in thermal resistance with an increase in air flow rate into interlayers occurs faster than an increase in the amount of air-entrained moisture. Conclusion. Results of the work have shown that the use of an air duct throughout the entire period of operation of a building is not effective, but it is proposed to use this duct periodically in winter to dry the condensate.

Heat Transfer on Nanofluid Flow With Homogeneous–Heterogeneous Reactions and Internal Heat Generation

2014 ◽  
Vol 136 (12) ◽  
Author(s):  
Raj Nandkeolyar ◽  
Peri K. Kameswaran ◽  
Sachin Shaw ◽  
Precious Sibanda
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Heat Generation ◽  
Internal Heat ◽  
Internal Heat Generation ◽  
Heterogeneous Reactions ◽  
Transfer Coefficients ◽  
Transfer Characteristics ◽  
Fluid Properties

We investigated heat and mass transfer on water based nanofluid due to the combined effects of homogeneous–heterogeneous reactions, an external magnetic field and internal heat generation. The flow is generated by the movement of a linearly stretched surface, and the nanofluid contains nanoparticles of copper and gold. Exact solutions of the transformed model equations were obtained in terms of hypergeometric functions. To gain more insights regarding subtle impact of fluid and material parameters on the heat and mass transfer characteristics, and the fluid properties, the equations were further solved numerically using the matlab bvp4c solver. The similarities and differences in the behavior, including the heat and mass transfer characteristics, of the copper–water and gold–water nanofluids with respect to changes in the flow parameters were investigated. Finally, we obtained the numerical values of the skin friction and heat transfer coefficients.

scholarly journals NUMERICAL CALCULATION OF VELOCITY FIELDS FOR VISCO-ELASTIC MATERIALS IN CYLINDRICAL CHANNELS

2019 ◽  
pp. 19-28
Author(s):  
Ekaterina Valer'evna Fomenko ◽  
Albert Hamed-Harisovich Nugmanov ◽  
Thi Sen Nguyen ◽  
Aleksanyan Igor Yuryevich Aleksanyan
Keyword(s):  
Mass Transfer ◽  
Heat And Mass Transfer ◽  
Stokes Equations ◽  
Radiation Power ◽  
Wheat Gluten ◽  
Internal Heat ◽  
Velocity Fields ◽  
Navier Stokes ◽  
Navier Stokes Equation ◽  
Suggested Approach

The article touches upon the application of the numerical finite difference method for solving Navier-Stokes equation in case of one-dimensional problem of passing a cooled viscoelastic material inside circular nozzles. There have been analyzed the specific features of using the method and presented the results of its application. The object of study was not chosen at random, because viscous properties of raw gluten are variable and depend on the temperature, chemical composition and properties of the feedstock. Working not properly with the object of research (phenomenon, process), but with its model helps to characterize its properties and behavior in various situations relatively quickly and without significant costs. The need to identify patterns of internal heat and mass transfer, which is based on studying the kinetics of the process, is obvious for physic-mathematical modeling of heat and mass transfer processes of wheat gluten granulation, in particular, analyzing the mechanism of moisture removal during its drying under radiation power supply. The results of the conducted research are consistent with the available data on the subject, and the suggested approach to solving the problem of choosing rational hydrodynamic regimes has been applied due to the difficulty of experimental determining the velocity fields and problematic analyzing the system of hydrodynamic differential Navier-Stokes equations with variable proportionality ratios.

Thermodynamic Theory of Convective Drying Process of Porous Media

2002 ◽  
Author(s):  
You-Rong Li ◽  
Dan-Ling Zeng
Keyword(s):  
Mass Transfer ◽  
Heat Source ◽  
Heat And Mass Transfer ◽  
Internal Heat ◽  
Internal Heat Source ◽  
Thermodynamic Theory ◽  
Convective Drying ◽  
Internal Mass ◽  
Drying Process ◽  
Mass Source

Based on non-equilibrium thermodynamic theory and combined with the conservation laws, a comprehensive theoretical model was established to describe heat and mass transfer during convective drying process, and numerical calculation was performed. The results show that: (a) the external convective heat and mass transfer may be treated as the conductive heat transfer with internal heat source and the molecular mass diffusion with internal mass source, respectively, and the ability of heat and mass transfer mainly depends on the strength of the heat source and mass source; the higher the temperature of the drying media, the lower the strength of the internal heat source, but the higher that of the internal mass sources; (b) the evaporation of internal water takes place inside the whole material, and the molecular mass diffusion of the internal vapor is in the direction of decreasing mass transfer potential, not along the decreasing partial pressure of vapor.

scholarly journals A novel internal heat recycling concept for reducing energy consumption and increasing flux through three-stage air-gap–water-gap membrane distillation system

2020 ◽  
Vol 20 (7) ◽  
pp. 2858-2874
Author(s):  
Mostafa Abd El-Rady Abu-Zeid ◽  
Xiaolong Lu ◽  
Shaozhe Zhang
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Energy Consumption ◽  
Heat And Mass Transfer ◽  
Waste Heat ◽  
Internal Heat ◽  
High Energy ◽  
Membrane Distillation ◽  
Air Gap ◽  
Air Gap Membrane Distillation

Abstract The low flux and high energy consumption problems of the conventional three-stage air-gap membrane distillation (AG-AG-AG)MD system caused by the low temperature difference between hot and cold feed at both sides of the membrane and high boundary layer thickness were solved successfully by replacing one of the three stages of air gaps by a water gap. The novel three-stage air-gap–water-gap membrane distillation (AG-AG-WG)MD system reduced energy consumption and increased flux due to efficient internal heat recycling by virtue of a water-gap module. Heat and mass transfer in novel and conventional three-stage systems were analyzed theoretically. Under a feed temperature of 45 °C, flow rate of 20 l/h, cooling temperature of 20 °C, and concentration of 340 ppm, the (AG-AG-WG)MD promoted flux by 17.59% and 211.69%, and gained output ratio (GOR) by 60.57% and 204.33% compared with two-stage (AG-WG)MD and one-stage AGMD, respectively. This work demonstrated the important role of a water gap in changing the heat and mass transfer where convection heat transfer across the water gap is faster by 24.17 times than conduction heat transfer through the air gap. The increase in flux and GOR economized the heating energy and decreased waste heat input into the system. Additionally, the number of MD stages could increase the achieving of a high flux with operation stability.

scholarly journals Analysis of Magnetic and Non Magnetic Nanoparticles With Newtonian/non-newtonian Base Fluids Over a Nonlinear Stretching Sheet

2020 ◽  
Author(s):  
kanwal Jabeen ◽  
Muhamad Mushtaq ◽  
Rana MUhammad Akram
Keyword(s):  
Mass Transfer ◽  
Magnetic Nanoparticles ◽  
Heat And Mass Transfer ◽  
Sodium Alginate ◽  
Stretching Sheet ◽  
Internal Heat ◽  
Al2o3 Nanoparticles ◽  
Ohmic Dissipation ◽  
Nonlinear Stretching ◽  
The Impact

Abstract Unsteady mixed convectional boundary layer flow of Casson nanofluid having magnetic( Fe3O4) and nonmagnetic( Al2O3) nanoparticles suspension within two different types of base fluids, water(Newtonian) and Sodium Alginate(non-Newtonian), which incorporates viscous and ohmic dissipation effects over a permeable nonlinear stretching sheet with magnetic field effects. Some suitable non-dimensional similarity transformations are applied to convert the governing PDEs into a system of nonlinear coupled ODEs and then solved by differential transformation method(DTM) association with Pade-approximation. To validate the present results for limited cases, a comparison was made with previously existing literature and found to be in well agreement. The impact of radiation, internal heat sink/ source, viscous and ohmic dissipation was discussed for magnetic and non-magnetic nanofluid categories by tabular and graphical demonstrations. We have presented the tabular results of various emerging parameters to discuss the nature of skin friction, Nusselt and Sherwood numbers. It was also observed that performance of non-Newtonian(Sodium Alginate) fluid in heat and mass transfer is better than Newtonian(water) based fluid but no major difference was seen in heat and mass transfer when comparison was made with Magnetic and Non-magnetic nanoparticles

Sign in / Sign up

Export Citation Format

Share Document