scholarly journals Temperature and Velocity Behaviour During Melting of a PCM in a Uniformly Heated Circular Cavity

2020 ◽  
Author(s):  
Kyle Teather ◽  
Kamran Siddiqui
Keyword(s):  
Heat Transfer ◽  
Particle Image ◽  
Heating Temperature ◽  
Temperature Fields ◽  
Velocity Magnitude ◽  
Image Velocimetry ◽  
Transient Velocity ◽  
Convective Cells ◽  
Temperature And Velocity Fields

Abstract This study is focused on the detailed characterization of the transient velocity and temperature fields of a PCM enclosed in a circular geometry subjected to uniform external heating. Temperature data was collected using a grid of thermocouples protruding through the transaxial wall into the PCM cavity. Particle image velocimetry (PIV) was used to collect velocity data within the melted PCM to study the buoyancy-driven convective heat transfer. Experiments were conducted at three heating conditions. The results show symmetric behaviour of temperature and velocity fields and show strong convective cells. The results also show that the velocity magnitude and its behaviour influenced the temperature field and hence the heat transfer rate.

Flow Dynamics Over Two Cylinders in Tandem Subjected to Different Heating Cases

2021 ◽  
Author(s):  
Rami Homsi ◽  
MD Islam ◽  
Yap Yit Fatt ◽  
Isam Janajreh
Keyword(s):  
Heat Transfer ◽  
Cross Flow ◽  
Temperature Fields ◽  
Circular Cylinders ◽  
Transfer Coefficients ◽  
Extended Body ◽  
Heat Transfer Coefficients ◽  
Velocity Magnitude ◽  
Fluid Properties ◽  
Limiting Case

Abstract Heated and unheated flows with forced convection over two fixed circular cylinders in tandem are studied numerically for 80 ≤ Re ≤ 250 and 1 ≤ T* ≤ 2.3. Three different spacing ratios (L/D) = [2, 4, 8] are considered under three heating conditions. The scenarios considered are (1) heated upstream and unheated downstream cylinders, (2) unheated upstream and heated downstream cylinders and (3) heated upstream and downstream cylinders. These scenarios represent the limiting case for a cross-flow heat exchanger, where the downstream tubes are at increasingly lower or higher temperature for cooling or heating, respectively. The global aerodynamic forces on the cylinder as vortices shed was investigated. The flow is visualized by plotting the streamlines, temperature fields, and velocity magnitude contours for the different spacing ratios and compared to the flow regimes in literature namely, Extended-body, Reattachment, and Co-shedding regimes. The drag and surface heat transfer coefficients are analyzed for different scenarios. The effect of heating on the fluid properties and the resulted wakes in the flow are found to be strongly influenced by Re and L/D. The scenario of heated upstream and unheated downstream cylinders was found to increase the mean drag coefficient Cd on the upstream cylinder for L/D = 2 & 4 but is not as evident for the downstream cylinder. The heat transfer coefficient h on the upstream cylinder remained approximately the same regardless of a heated or unheated downstream cylinder. In contrast, h of the downstream cylinder decreases for the scenario of heated upstream and downstream cylinder.

Particle Image Velocimetry in a High-Pressure Turbine Stage at Aerodynamically Engine Representative Conditions

2020 ◽  
Author(s):  
Daniel Inman ◽  
David Gonzalez Cuadrado ◽  
Valeria Andreoli ◽  
Jordan Fisher ◽  
Guillermo Paniagua ◽  
...  
Keyword(s):  
High Pressure ◽  
Particle Image Velocimetry ◽  
Vector Fields ◽  
Particle Image ◽  
Flow Direction ◽  
Operating Conditions ◽  
Velocity Magnitude ◽  
Resultant Velocity ◽  
Image Velocimetry ◽  
Annular Cascade

Abstract Particle Image Velocimetry (PIV) is a well-established technique for determining the flow direction and velocity magnitude of complex flows. This paper presents a methodology for executing this non-intrusive measurement technique to study a scaled-up turbine vane geometry within an annular cascade at engine-relevant conditions. Custom optical tools such as laser delivery probes and imaging inserts were manufactured to mitigate the difficult optical access of the test section and perform planar PIV. With the use of a burst-mode Nd: YAG laser and Photron FASTCAM camera, the frame straddling technique is implemented to enable short time intervals for the collection of image pairs and velocity fields at 10 kHz. Furthermore, custom image processing tools were developed to optimize the contrast and intensity balance of each image pair to maximize particle number and uniformity, while removing scattering and background noise. The pre-processing strategies significantly improve the vector yield under challenging alignment, seeding, and illumination conditions. With the optical and software tools developed, planar PIV was conducted in the passage of a high-pressure stator row, at mid-span, in an annular cascade. Different Mach and Reynolds number operating conditions were achieved by modifying the temperature and mass flow. With careful spatial calibration, the resultant velocity vector fields are compared with Reynolds Averaged Navier Stokes (RANS) simulations of the vane passage with the same geometry and flow conditions. Uncertainty analysis of the experimental results is also presented and discussed, along with prospects for further improvements.

Investigation of Combustion Oscillations in a Lean Gas Turbine Model Combustor

2007 ◽  
Author(s):  
Olaf Diers ◽  
Denis Schneider ◽  
Melanie Voges ◽  
Peter Weigand ◽  
Christoph Hassa
Keyword(s):  
Atmospheric Pressure ◽  
Acoustic Pressure ◽  
Particle Image ◽  
Operating Conditions ◽  
Operating Point ◽  
Image Velocimetry ◽  
Different Types ◽  
Mass Flows ◽  
Combined Data

This contribution is a continuation of ASME-GT2006-90300. While still working at atmospheric pressure, the range of operating conditions was extended to more realistic reduced mass flows to reproduce the engine pressure loss and air preheat up to 700K. The thermoacoustic behaviour of the burner was mapped over that operating range. Two different types of oscillations were observed for flames anchored at the nozzle or lifted from it. Both exhibited a frequency dependence on the Strouhal number for constant reduced mass flows. For a selected operating point with the lifted flame at a preheat temperature of 600K and a reduced mass flow of 0.3kg K0.5/(s bar), the thermoacoustic behaviour of the burner was characterised by phase locked Particle Image Velocimetry as well as phase locked OH- and OH-T- LIF measurements and correlated to the acoustic pressure signal obtained by microphones. The combined data showed pulsating combustion being supported through periodic reignition of the main flame zone by a recirculating volume of hot, OH-rich gas, the cycle time being connected to the observed frequency. The characterization of the preheated operating point was completed with a heat balance investigation quantifying the non-adiabatic combustion conditions of the uncooled combustor.

scholarly journals Experimental Study of Heat Convection From Stationary and Oscillating Circular Cylinder in Cross Flow

2000 ◽  
Vol 123 (1) ◽  
pp. 51-62 ◽  
Author(s):  
H. G. Park ◽  
Morteza Gharib
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Particle Image ◽  
Forced Oscillation ◽  
Oscillation Amplitude ◽  
Cross Flow ◽  
Digital Particle Image Velocimetry ◽  
Image Velocimetry ◽  
Vortex Shedding Frequency ◽  
Shedding Frequency

An experimental study is made on the processes of heat transfer from the surface of a forced oscillating cylinder in a crossflow. A range of oscillation amplitude A/D=0.1,0.2, forced oscillation frequency 0<Stc<1, and Reynolds number (Re=550, 1100, 3500) is covered in water Pr=6. Besides the increase at the natural vortex shedding frequency, large increases in the heat transfer are found at certain superharmonics. By using Digital Particle Image Velocimetry/Thermometry (DPIV/T), the increase in the heat transfer rate is found to correlate inversely with the distance at which vortices roll-up behind the cylinder, i.e., the distance decreases when the heat transfer increases. The cause of the increase is found to be the removal of the stagnant and low heat convecting fluid at the base of the cylinder during the roll-up of the vortices.

Sign in / Sign up

Export Citation Format

Share Document