Computational fluid dynamics and analytical modeling for predicting effects of airflow temperature and relative humidity on the terminal velocity of agricultural granular materials

2021 ◽  
Author(s):  
Mohammad Hadi Dousthaghi ◽  
Saeid Minaei ◽  
Mohammad Hadi Khoshtaghaza
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Relative Humidity ◽  
Granular Materials ◽  
Analytical Modeling ◽  
Terminal Velocity

scholarly journals Back protection of canvas paintings

2020 ◽  
Vol 8 (1) ◽  
Author(s):  
Tim Padfield ◽  
Nicolas Padfield ◽  
Daniel Sang-Hoon Lee ◽  
Anne Thøgersen ◽  
Astrid Valbjørn Nielsen ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Relative Humidity ◽  
Temperature Variation ◽  
Room Temperature ◽  
Single Point ◽  
Confined Space ◽  
Constant Wall Temperature ◽  
Back Plate ◽  
Inner Surface

Abstract In this paper different scenarios for back protection of a canvas painting and their effect on the stability of the relative humidity behind the painting are tested. A painting on canvas, stretched on a wooden frame, was fitted with various styles of back protection and then exposed to a cycle of temperature variation at the back, with the front exposed to a constant room temperature. The painting was also exposed to a constant wall temperature and varying room temperature. The space between the canvas and the back board was fitted with temperature and relative humidity (RH) sensors. The sensors were used to provide the essential single-point data of temperature and RH at the given locations. For more comprehensive understanding of the rather confined space, further numerical simulation (computational fluid dynamics) was adopted as part of the investigation. The computational fluid dynamics was used to understand the natural convection within the microclimate through the depictions of temperature distribution, as well as the corresponding airflow. The unprotected painting suffered a large RH variation at its back, because of the varying canvas temperature interacting with the constant room air moisture content. Effective stabilisation of the RH behind the canvas against temperature variation was provided by a shiny aluminium alloy sheet sealed against the frame. The non-absorbent back board experienced a strong variation in RH, because of humidity buffering of the space by the painting canvas at a different temperature. Either a space or insulation between this back plate and the wall reduced the risk of condensation on the inner surface of the back plate. Insulation will however increase the risk of condensation on the wall surface behind the painting. An absorbent back board de-stabilised the RH at the painting canvas surface by providing a competing humidity buffer at a different temperature. To provide protection against moisture exchange with an unsuitable room RH, extra humidity buffer was placed 3 mm behind the painting canvas, kept close to the painting temperature by insulation between this buffer and the back board. This stabilised RH at the canvas surface but increased both the temperature and the RH variation at the back board and thus increased the risk of condensation on the inner surface of the back board. The RH and the temperature in the narrow spaces between the painting canvas and the wooden stretcher frame were always more nearly constant than in the open canvas area, which suggests an explanation for the widely observed better condition of the areas of canvas paintings which lie close over the support structure. Our conclusion is that a non-absorbent, impermeable back plate gives good RH stability against a changing temperature gradient between wall and canvas painting surface.

Numerical Modeling of Proton Exchange Membrane Fuel Cell With Considering Thermal and Relative Humidity Effects on the Cell Performance

2006 ◽  
Vol 3 (3) ◽  
pp. 292-302 ◽  
Author(s):  
Pei-Hung Chi ◽  
Fang-Bor Weng ◽  
Ay Su ◽  
Shih-Hung Chan
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Fuel Cell ◽  
Relative Humidity ◽  
Proton Exchange Membrane ◽  
Thermal Field ◽  
Proton Exchange ◽  
Cell Performance ◽  
Water Flooding ◽  
Exchange Membrane

A three-dimensional (3D) model has been developed to simulate proton exchange membrane fuel cells. The model accounts simultaneously for electrochemical kinetics, current distribution, hydrodynamics, and multi-components transport. A single set of conservation equations of mass, momentum, energy, species, and electric current are developed and numerically solved using a finite-volume-based computational fluid dynamics technique (by computational fluid dynamics ACE+ commercial code). The physical model is presented for a 5cm×4.92cm×0.4479cm 3D geometry test cell with serpentine channels and counter flow. Subsequently, the model is applied to explore cell temperature effects in the cell environment with different relative humidity of inlet. The numerical model is validated and agreed well with the experimental data. The nonuniformity of thermal and water-saturation distributions is calculated and analyzed as well as its influence on the cell performance. As the cell is operated at low voltages (or high current densities), the thermal field of fuel cell tends to be nonuniform and exists locally in hot spots. The mechanism of thermal field and water content interacted with membrane dehydration and cathode water flooding will be discussed and revealed their influences on the cell performance, stability and degradation will be revealed.

AN ITERATIVE NONUNIFORMLY SPACED FINITE DIFFERENCE SCHEME FOR COMPUTATIONAL FLUID DYNAMICS

2001 ◽  
Vol 12 (07) ◽  
pp. 1023-1033
Author(s):  
ANDREAS HORRAS ◽  
GERALD H. RISTOW
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Finite Difference ◽  
Difference Scheme ◽  
Newtonian Fluid ◽  
Finite Difference Scheme ◽  
Infinite System ◽  
System Size ◽  
Terminal Velocity ◽  
Staggered Grid

The settling dynamics of cylinders in a viscous Newtonian fluid are investigated numerically using an iterative finite difference scheme, which uses a nonuniformly spaced staggered grid. Special attention is given to the details of the spatial discretization and how they influence the physical results. The terminal velocity is calculated for different system sizes and cylinder diameters and the extrapolated values for an infinite system size are compared with the Oseen approximation.

scholarly journals Back protection of canvas paintings

2020 ◽  
Author(s):  
Tim Padfield ◽  
Nicolas Padfield ◽  
Daniel Sang-Hoon Lee ◽  
Anne Thøgersen ◽  
Astrid Valbjørn Nielsen ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Relative Humidity ◽  
Temperature Variation ◽  
Room Temperature ◽  
Single Point ◽  
Confined Space ◽  
Constant Wall Temperature ◽  
Back Plate ◽  
Inner Surface

Abstract In this paper different scenarios for back protection of a canvas painting and their effect on the stability of the relative humidity behind the painting are tested. A painting on canvas, stretched on a wooden frame, was fitted with various styles of back protection and then exposed to a cycle of temperature variation at the back, with the front exposed to a constant room temperature. The painting was also exposed to a constant wall temperature and varying room temperature. The space between the canvas and the back board was fitted with temperature and relative humidity (RH) sensors. The sensors were used to provide the essential single-point data of temperature and RH at the given locations. For more comprehensive understanding of the rather confined space, further numerical simulation (computational fluid dynamics) was adopted as part of the investigation. The computational fluid dynamics was used to understand the natural convection within the microclimate through the depictions of temperature distribution, as well as the corresponding air flow. The unprotected painting sffered a large RH variation at its back, because of the varying canvas temperature interacting with the constant room air moisture content. Effective stabilisation of the RH behind the canvas against temperature variation was provided by a shiny aluminium alloy sheet sealed against the frame. The non-absorbent back board experienced a strong variation in RH, because of humidity bu ering of the space by the painting canvas at a different temperature. Either a space or insulation between this back plate and the wall reduced the risk of condensation on the inner surface of the back plate. Insulation will however increase the risk of condensation on the wall surface behind the painting. An absorbent back board de-stabilised the RH at the painting canvas surface by providing a competing humidity bu er at a different temperature. To provide protection against moisture exchange with an unsuitable room RH, extra humidity bu er was placed 3 mm behind the painting canvas, kept close to the painting temperature by insulation between this bu er and the back board. This stabilised RH at the canvas surface but increased both the temperature and the RH variation at the back board and thus increased the risk of condensation on the inner surface of the back board. The RH and the temperature in the narrow spaces between the painting canvas and the wooden stretcher frame were always more nearly constant than in the open canvas area, which suggests an explanation for the widely observed better condition of the areas of canvas paintings which lie close over the support structure. Our conclusion is that a non-absorbent, impermeable back plate gives good RH stability against a changing temperature gradient between wall and canvas painting surface.

scholarly journals Three-dimensional air distribution analysis of different outflow typed operating rooms at different inlet velocities and room temperatures

2017 ◽  
Vol 9 (7) ◽  
pp. 168781401770741 ◽  
Author(s):  
Hande Ufat ◽  
Omer Kaynakli ◽  
Nurettin Yamankaradeniz ◽  
Recep Yamankaradeniz
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Relative Humidity ◽  
Operating Room ◽  
Three Dimensional ◽  
Operating Rooms ◽  
Air Distribution ◽  
Distribution Analysis ◽  
Laminar Air Flow ◽  
The One

It is important to provide a regular unidirectional air distribution in an operating room to reduce the number of particles. Measurements were taken in the one of the operating rooms at Uludag University Medical School, with laminar air flow unit and two-cornered outlet which was thought to have some airflow problems. Moreover, a three-dimensional computational fluid dynamics model has been developed where the measurements were taken in. The distributions of air velocity, temperature, and relative humidity have been examined and compared with the measurements to validate the computational fluid dynamics analyses. In addition to present model, four-cornered outlet operating room has been analyzed and compared with the results of two-cornered one. It is concluded that the case of four-cornered outlet provides more suitable thermal distribution, which results in a reduction of the particle numbers in the interior. Although there is no significant change in temperature and relative humidity in the operating room, air distribution changes dramatically.

Sign in / Sign up

Export Citation Format

Share Document