The Influence of Heat Source Orientation on PCM Flow Behavior During Phase Transition

2018 ◽  
Author(s):  
Steven Jevnikar ◽  
Kamran Siddiqui
Keyword(s):  
Fluid Flow ◽  
Heat Source ◽  
Tilt Angle ◽  
Recirculation Zone ◽  
Transient Flow ◽  
Flow Behavior ◽  
Melting Process ◽  
Melting Rate ◽  
Bulk Fluid ◽  
Stagnant Region

The present study reports the characterization of the transient flow behavior in the liquid PCM domain during the melting process, initiated by a planer heat source. Experiments were conducted at three angles of inclination of the heat source (0, 8 and 18-degrees) from the vertical. Paraffin wax was used as the PCM and was enclosed in an insulated, optically clear, thin rectangular chamber. Particle image velocimetry (PIV) was used during the melting process to measure the instantaneous velocity of the PCM and obtain two-dimensional velocity fields within the liquid domain. Results clearly show the presence of a dominant recirculation zone occurring at all angles. This recirculation zone was enhanced by an increase in the inclination of the heat source, supporting a direct correlation between the tilt angle and the bulk fluid flow in the melted region. The melting rate decreased with the progression of time for all investigated cases. A growing region of stagnant fluid flow within the center of the recirculation zone contributed to the reduction in the melt rate. The size of this stagnant region decreased with increases in the tilt angle due to the enhancement of natural convection. The data demonstrates significant changes in transient flow behavior with orientation in the liquid PCM domain. These results further our understanding of the phase change and associated heat transfer processes in PCM and have wide applicability to PCM-based thermal energy storage.

Pressure-Transient Behavior of Partially Penetrating Inclined Fractures With a Finite Conductivity

SPE Journal ◽  
2018 ◽  
Vol 24 (02) ◽  
pp. 811-833 ◽  
Author(s):  
Bailu Teng ◽  
Huazhou Andy Li
Keyword(s):  
Fluid Flow ◽  
Transient Flow ◽  
Flow Behavior ◽  
Transient Behavior ◽  
Finite Conductivity ◽  
Linear Flow ◽  
Pressure Transient ◽  
Proposed Model ◽  
Elliptical Flow ◽  
The Matrix

Summary Field studies have shown that, if an inclined fracture has a significant inclination angle from the vertical direction or the fracture has a poor growth along the inclined direction, this fracture probably cannot fully penetrate the formation, resulting in a partially penetrating inclined fracture (PPIF) in these formations. It is necessary for the petroleum industry to conduct a pressure-transient analysis on such fractures to properly understand the major mechanisms governing the oil production from them. In this work, we develop a semianalytical model to characterize the pressure-transient behavior of a finite-conductivity PPIF. We discretize the fracture into small panels, and each of these panels is treated as a plane source. The fluid flow in the fracture system is numerically characterized with a finite-difference method, whereas the fluid flow in the matrix system is analytically characterized on the basis of the Green's-function method. As such, a semianalytical model for characterizing the transient-flow behavior of a PPIF can be readily constructed by coupling the transient flow in the fracture and that in the matrix. With the aid of the proposed model, we conduct a detailed study on the transient-flow behavior of the PPIFs. Our calculation results show that a PPIF with a finite conductivity in a bounded reservoir can exhibit the following flow regimes: wellbore afterflow, fracture radial flow, bilinear flow, inclined-formation linear flow, vertical elliptical flow, vertical pseudoradial flow, inclined pseudoradial flow, horizontal-formation linear flow, horizontal elliptical flow, horizontal pseudoradial flow, and boundary-dominated flow. A negative-slope period can appear on the pressure-derivative curve, which is attributed to a converging flow near the wellbore. Even with a small dimensionless fracture conductivity, a PPIF can exhibit a horizontal-formation linear flow. In addition to PPIFs, the proposed model also can be used to simulate the pressure-transient behavior of fully penetrating vertical fractures (FPVFs), partially penetrating vertical fractures (PPVFs), fully penetrating inclined fractures (FPIFs), and horizontal fractures (HFs).

Effect of Heat Source Geometry on the Transient Heat Transfer During Melting Process of a PCM

2016 ◽  
Author(s):  
Mohammad Bashar ◽  
Kamran Siddiqui
Keyword(s):  
Heat Transfer ◽  
Heat Source ◽  
Convective Heat Transfer Coefficient ◽  
Outer Region ◽  
Melting Process ◽  
Melting Rate ◽  
Transfer Coefficients ◽  
Heat Transfer Behavior ◽  
Transfer Behavior ◽  
Inner Region

Thermal energy storage (TES) systems using phase change materials (PCMs) are used in various engineering applications. TES is a means by which heat is ‘hold’ for a certain period of time for use at a later time. We report an experimental study which was conducted to investigate the melting process and associated heat transfer in a rectangular chamber with a cylindrical u-shaped heat source imbedded inside the PCM. The results showed that geometry and orientation of the heat source immensely influenced the heat transfer behavior during solid-liquid phase transition. The heat transfer behavior, interface movement and the heat transfer coefficients differed both axially and vertically inside the chamber as well as with the melting rate. The local convective heat transfer coefficient, hlocal in the inner region, enclosed by the U-tube, was observed to increase at a higher rate than the outer region. Stronger convective flow and a lower viscosity owing to higher temperature in the inner region is believed to have caused faster melting in this region. The melting rate was also found comparatively higher until approximately two-third of the PCM volume was melted before the rate declined.

SECOND‐GRADE FLUID FLOW WITH POWER‐LAW HEAT FLUX AND A HEAT SOURCE

2013 ◽  
Vol 44 (8) ◽  
pp. 687-702 ◽  
Author(s):  
Tasawar Hayat ◽  
Sabir A. Shehzad ◽  
Muhammad Qasim ◽  
F. Alsaadi ◽  
Ahmed Alsaedi
Keyword(s):  
Heat Flux ◽  
Fluid Flow ◽  
Heat Source ◽  
Power Law ◽  
Second Grade ◽  
Second Grade Fluid ◽  
Grade Fluid ◽  
Power Law Heat Flux

Solving the Problem of Silicon Dioxide Melting Based on Deviation Model

2020 ◽  
Vol 2 (1) ◽  
Author(s):  
Yuhan Sun
Keyword(s):  
Silicon Dioxide ◽  
Blast Furnace Slag ◽  
Melting Process ◽  
Melting Rate ◽  
Dissolution Behavior ◽  
Characteristic Parameters ◽  
Contour Feature ◽  
Time Periods ◽  
Main Component ◽  
Furnace Slag

Abstract: In order to reveal the dissolution behavior of iron tailings in blast furnace slag, we studied the main component of silica in iron tailings. First, edge contour features need to be established to represent the melting process of silica. We choose shape, perimeter, area and generalized radius as objects. By independently analyzing the influence of these four indexes on the melting rate, the area and shape were selected as the characteristic parameters of the edge contour of the silica particles. Then, the actual melting rate of the silica is estimated by the edge contour feature index. Finally, we can calculate the melting rate of the first second of three time periods of 0.00010312mm3/s，0.0002399mm3/s，0.0000538mm3/s.

New benchmark solutions for transient natural convection in partially porous annuli

2016 ◽  
Vol 26 (3/4) ◽  
pp. 1187-1225 ◽  
Author(s):  
Nicola Massarotti ◽  
Michela Ciccolella ◽  
Gino Cortellessa ◽  
Alessandro Mauro
Keyword(s):  
Natural Convection ◽  
Free Convection ◽  
Transient Flow ◽  
Flow Behavior ◽  
Outer Radius ◽  
Temperature Fields ◽  
Content Type ◽  
Transient Natural Convection ◽  
Velocity And Temperature Fields ◽  
Benchmark Solutions

Purpose – The purpose of this paper is to focus on the numerical analysis of transient free convection heat transfer in partially porous cylindrical domains. The authors analyze the dependence of velocity and temperature fields on the geometry, by analyzing transient flow behavior for different values of cavity aspect ratio and radii ratio; both inner and outer radius are assumed variable in order to not change the difference ro-ri. Moreover, several Darcy numbers have been considered. Design/methodology/approach – A dual time-stepping procedure based on the transient artificial compressibility version of the characteristic-based split algorithm has been adopted in order to solve the transient equations of the generalized model for heat and fluid flow through porous media. The present model has been validated against experimental data available in the scientific literature for two different problems, steady-state free convection in a porous annulus and transient natural convection in a porous cylinder, showing an excellent agreement. Findings – For vertically divided half porous cavities, with Rayleigh numbers equal to 3.4×106 for the 4:1 cavity and 3.4×105 for the 8:1 cavity, the numerical results show that transient oscillations tend to disappear in presence of cylindrical geometry, differently from what happens for rectangular one. The magnitude of this phenomenon increases with radii ratio; the porous layer also affects the stability of velocity and temperature fields, as oscillations tend to decrease in presence of a porous matrix with lower value of the Darcy number. Research limitations/implications – A proper analysis of partially porous annular cavities is fundamental for the correct estimation of Nusselt numbers, as the formulas provided for rectangular domains are not able to describe these problems. Practical implications – The proposed model represents a useful tool for the study of transient natural convection problems in porous and partially porous cylindrical and annular cavities, typical of many engineering applications. Moreover, a fully explicit scheme reduces the computational costs and ensures flexibility. Originality/value – This is the first time that a fully explicit finite element scheme is employed for the solution of transient natural convection in partially porous tall annular cavities.

scholarly journals Computational investigation of thermal behavior and molten metal flow with moving laser heat source for selective laser melting process

2021 ◽  
Vol 24 ◽  
pp. 100860
Author(s):  
Patiparn Ninpetch ◽  
Pruet Kowitwarangkul ◽  
Sitthipong Mahathanabodee ◽  
Prasert Chalermkarnnon ◽  
Phadungsak Rattanadecho
Keyword(s):  
Heat Source ◽  
Thermal Behavior ◽  
Selective Laser Melting ◽  
Molten Metal ◽  
Metal Flow ◽  
Melting Process ◽  
Computational Investigation ◽  
Laser Melting ◽  
Laser Heat Source ◽  
Molten Metal Flow
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