Evaluation of Condenser Transient Heat Transfer Behavior of the Small Scale Capillary-Pumped Loop

2007 ◽  
Author(s):  
Hung-Wen Lin ◽  
Yu-An Lin ◽  
Wei-Keng Lin
Keyword(s):  
Flow Characteristics ◽  
Infrared Camera ◽  
Small Scale ◽  
Outlet Temperature ◽  
Capillary Pumped Loop ◽  
Power Load ◽  
Scale Down ◽  
Condenser Temperature ◽  
Transfer Behavior ◽  
Experimental Values

A general method was developed to predict the condenser temperature at each power load. And a simulation program and infrared camera was used to study the flow characteristics. High density polyethylene porous material was added in the evaporator to CPL, the loop was designed on the ground with a horizontal position and scale down the whole device to the miniature size. From the experimental results, the CPL could remove heat 110W in steady state and keep the heat source temperature about 80°C. Finally, a good agreement between the simulation and experimental values has been achieved. Comparing with experiment and simulation results, the deviation values of the distributions of the condenser outlet temperature are less than 5%.

scholarly journals 3D Modeling of the Thermal Transfer through Precast Buildings Envelopes

Energies ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3751
Author(s):  
Soukayna Berrabah ◽  
Mohamed Ould Moussa ◽  
Mohamed Bakhouya
Keyword(s):  
Infrared Camera ◽  
Functional Materials ◽  
Building Envelope ◽  
Small Scale ◽  
Test Bed ◽  
Proposed Model ◽  
Precast Buildings ◽  
Mechanical Study ◽  
Experimental Values ◽  
Thermal Phenomena

In this paper, a finite-element-based model is being introduced and developed, using the Cast3m (CEA, Paris, France) simulation tool, to evaluate the thermo-mechanical behavior of a small-scale test bed. In fact, many studies on thermal behavior of cavities have been carried out in literature. However, none of them took into account the co-existence of all thermal phenomena (conduction, convection, internal/external radiation). The work presented in this paper presents a thermo-mechanical model, which aims to combine, in a holistic way, these phenomena. An experimental validation of the thermal model has been first carried out using an infrared camera and DS18B20 (Maxim Integrated Products, Dallas, TX, USA) numerical sensors. Results are reported and show the accuracy of the proposed model since both numerical and experimental values of heat transmittance fit together. The main objective is to evaluate heat losses through the walls, by means of heat transmittance calculation, and proposing new functional materials that will help in energy harvesting, as a perspective of this work. As for the mechanical study, it was meant to investigate the distribution of the mechanical stress towards the building envelope submitted to its own weight. Results showed that the stress is uniformly distributed on the lateral walls of the structure as well as on the floor.

Experiments on wind-driven heat exchange processes over melting snow

2021 ◽  
Author(s):  
Michael Haugeneder ◽  
Tobias Jonas ◽  
Dylan Reynolds ◽  
Michael Lehning ◽  
Rebecca Mott
Keyword(s):  
Snow Cover ◽  
Surface Wind ◽  
Infrared Camera ◽  
Snow Accumulation ◽  
Internal Boundary ◽  
Small Scale ◽  
Snow Melt ◽  
Two Dimensional ◽  
Atmospheric Conditions ◽  
Near Surface

<p>Snowmelt runoff predictions in alpine catchments are challenging because of the high spatial variability of t<span>he snow cover driven by </span>various snow accumulation and ablation processes. In spring, the coexistence of bare and snow-covered ground engages a number of processes such as the enhanced lateral advection of heat over partial snow cover, the development of internal boundary layers, and atmospheric decoupling effects due to increasing stability at the snow cover. The interdependency of atmospheric conditions, topographic settings and snow coverage remains a challenge to accurately account for these processes in snow melt models.<br>In this experimental study, we used an Infrared Camera (VarioCam) pointing at thin synthetic projection screens with negligible heat capacity. Using the surface temperature of the screen as a proxy for the air temperature, we obtained a two-dimensional instantaneous measurement. Screens were installed across the transition between snow-free and snow-covered areas. With IR-measurements taken at 10Hz, we capture<span> the dynamics of turbulent temperature fluctuations</span><span> </span>over the patchy snow cover at high spatial and temporal resolution. From this data we were able to obtain high-frequency, two-dimensional windfield estimations adjacent to the surface.</p><p>Preliminary results show the formation of a stable internal boundary layer (SIBL), which was temporally highly variable. Our data suggest that the SIBL height is very shallow and strongly sensitive to the mean near-surface wind speed. Only strong gusts were capable of penetrating through this SIBL leading to an enhanced energy input to the snow surface.</p><p>With these type of results from our experiments and further measurements this spring we aim to better understand small scale energy transfer processes over patch snow cover and it’s dependency on the atmospheric conditions, enabling to improve parameterizations of these processes in coarser-resolution snow melt models.</p>

Flume investigation of cylindrical baffles for dissipation of debris flow energy

2021 ◽  
Author(s):  
Chan-Young Yune ◽  
Beom-Jun Kim
Keyword(s):  
Energy Dissipation ◽  
Debris Flow ◽  
Debris Flows ◽  
High Speed ◽  
Flow Characteristics ◽  
Digital Camera ◽  
Major Effect ◽  
Small Scale ◽  
Design Guideline ◽  
Flow Energy

<p>A debris flow with a high speed along valleys has been reported to cause serious damages to urban area or infrastructure. To prevent debris flow disaster, countermeasures for flow-impeding structures are installed on the flow path of debris flows. Recently, an installation of cylindrical baffles which are open-type countermeasures has increased because of a low construction cost, filtering out rocks, and an increased hydraulic continuity. However, a comprehensive design guideline for specification and arrangement on cylindrical baffles has not yet been suggested. Moreover, the design of baffle installation is mainly based on empirical approaches as the influence of baffle array on debris mobility is not well understood. In this study, to investigate the effect of cylindrical baffles on the flow characteristics of debris flow, a series of small-scale flume tests were performed according to the varying baffle height and row numbers of installed baffles. High-speed cameras and digital camera to record the flow interaction with baffles were installed at the top and side of the channel. To reproduce the viscosity of debris flows caused by fine-grained soil in the flume, glycerin was mixed with debris materials (sand and gravel). After the test, the velocity and energy dissipation according to various baffle arrays were estimated. Test results showed that the installation of baffles reduced the frontal velocity of debris flows. Furthermore, taller baffles also increased the effect of the energy dissipation in debris flows, but additional rows of the baffle did not have a major effect on the energy dissipation. Thus, increasing the height of baffle led to an increased efficiency of energy dissipation of debris flows.</p>

FULL SCALE EXPERIMENT AND NUMERICAL ANALYSIS FOR THE PERFORMANCE OF HEAT EXCHANGER IN MOLTEN CARBONATE FUEL CELLS

2016 ◽  
Vol 40 (5) ◽  
pp. 799-810
Author(s):  
Seon-Hwa Kim ◽  
Byeong-Keun Choi ◽  
Young-Su An
Keyword(s):  
Heat Exchanger ◽  
Fuel Cell ◽  
Flow Characteristics ◽  
Cell System ◽  
Molten Carbonate Fuel Cell ◽  
Molten Carbonate ◽  
Fuel Gas ◽  
Operation Conditions ◽  
Scale Down ◽  
Scale Experiment

This study presents a numerical simulation of heat transfer and flow characteristics of the heat exchanger in molten carbonate fuel cell system. In this study, the actual size of the heat exchanger was simulated in order to avoid errors that can occur from the scale-down test, also the simulation gas (air) was verified with the heat duty of 800,000 kcal/hr. It is analyzed by using a commercial heat exchanger calculation code based upon the test condition. It is found that a reasonable agreement is obtained from comparison between the predicted results and the measured data. Furthermore, the verified similarity was presented in this analysis. In particular, the simulation gas used for the shell side service for the heat exchanger is obtained through the combustion calculation, i.e. by using a flow rate of the fuel gas. In addition, the performance of the heat exchanger is predicted under various conditions in the fuel cell operation conditions by the numerical model.

scholarly journals The relationship between small-scale and large-scale ionospheric electron density irregularities generated by powerful HF electromagnetic waves at high latitudes

2006 ◽  
Vol 24 (11) ◽  
pp. 2901-2909 ◽  
Author(s):  
E. D. Tereshchenko ◽  
B. Z. Khudukon ◽  
M. T. Rietveld ◽  
B. Isham ◽  
T. Hagfors ◽  
...  
Keyword(s):  
Geomagnetic Field ◽  
Electromagnetic Waves ◽  
Large Scale ◽  
Small Scale ◽  
Direction Parallel ◽  
Model Calculations ◽  
Amplitude Fluctuations ◽  
Field Lines ◽  
Experimental Values ◽  
Magnetic Zenith

Abstract. Satellite radio beacons were used in June 2001 to probe the ionosphere modified by a radio beam produced by the EISCAT high-power, high-frequency (HF) transmitter located near Tromsø (Norway). Amplitude scintillations and variations of the phase of 150- and 400-MHz signals from Russian navigational satellites passing over the modified region were observed at three receiver sites. In several papers it has been stressed that in the polar ionosphere the thermal self-focusing on striations during ionospheric modification is the main mechanism resulting in the formation of large-scale (hundreds of meters to kilometers) nonlinear structures aligned along the geomagnetic field (magnetic zenith effect). It has also been claimed that the maximum effects caused by small-scale (tens of meters) irregularities detected in satellite signals are also observed in the direction parallel to the magnetic field. Contrary to those studies, the present paper shows that the maximum in amplitude scintillations does not correspond strictly to the magnetic zenith direction because high latitude drifts typically cause a considerable anisotropy of small-scale irregularities in a plane perpendicular to the geomagnetic field resulting in a deviation of the amplitude-scintillation peak relative to the minimum angle between the line-of-sight to the satellite and direction of the geomagnetic field lines. The variance of the logarithmic relative amplitude fluctuations is considered here, which is a useful quantity in such studies. The experimental values of the variance are compared with model calculations and good agreement has been found. It is also shown from the experimental data that in most of the satellite passes a variance maximum occurs at a minimum in the phase fluctuations indicating that the artificial excitation of large-scale irregularities is minimum when the excitation of small-scale irregularities is maximum.

scholarly journals Numerical and Experimental Estimation of the Efficiency of a Quadcopter Rotor Operating at Hover

Energies ◽  
2019 ◽  
Vol 12 (2) ◽  
pp. 261 ◽  
Author(s):  
Andres G. ◽  
Juan S. ◽  
Omar López ◽  
Laura Suárez C, ◽  
Jaime A. Escobar
Keyword(s):  
Pressure Coefficient ◽  
Tip Vortex ◽  
Small Scale ◽  
Viscous Effects ◽  
Lattice Method ◽  
Vortex Lattice Method ◽  
Computational Fluid Dynamics Cfd ◽  
Experimental Values ◽  
Thrust And Torque

Globalization has led to an increase in the use of small copters for different activities such as geo-referencing, agricultural fields monitoring, survillance, among others. This is the main reason why there is a strong interest in the performance of small-scale propellers used in unmanned aerial vehicles. The flow developed by rotors is complex and the estimation of its aerodynamic performance is not a trivial process. In addition, viscous effects, when the rotor operates at low Reynolds, affect its performance. In the present paper, two different computational methods, Computational Fluid Dynamics (CFD) and the Unsteady Vortex Lattice Method (UVLM) with a viscous correction, were used to study the performance of an isolated rotor of a quadcopter flying at hover. The Multi Reference Frame model and transition S S T κ - ω turbulence model were used in the CFD simulations. The tip vortex core growth was used to account for the viscous effects in the UVLM. The wake structure, pressure coefficient, thrust and torque predictions from both methods are compared. Thrust and torque results from simulations were validated by means of experimental results of a characterization of a single rotor. Finally, figure of merit of the rotor is evaluated showing that UVLM overestimates the efficiency of the rotor; meanwhile, CFD predictions are close to experimental values.

Axisymmetric Flow in a Motored Reciprocating Engine

1978 ◽  
Vol 192 (1) ◽  
pp. 213-223 ◽  
Author(s):  
A. D. Gosman ◽  
A. Melling ◽  
J. H. Whitelaw ◽  
P. Watkins
Keyword(s):  
Laser Doppler Anemometry ◽  
Axisymmetric Flow ◽  
Flow Characteristics ◽  
Small Scale ◽  
Mean Velocity ◽  
Inlet Velocity ◽  
Reciprocating Engine ◽  
Laminar And Turbulent Flow ◽  
Flow Through ◽  
The Mean

A study was made of axisymmetric, laminar and turbulent flow in a motored reciprocating engine with flow through a cylinder head port. Measurements were obtained by laser-Doppler anemometry and predictions for the laminar case were generated by finite-difference means. Agreement between calculated and measured results is good for the main features of the flow field, but significant small scale differences exist, due partly to uncertainties in the inlet velocity distribution. The measurements show, for example, that the mean velocity field is influenced more strongly by the engine geometry than by the speed. In general, the results confirm that the calculation method can be used to represent the flow characteristics of motored reciprocating engines without compression and suggest that extensions to include compression and combustion are within reach.

Development of a Ceramic Pressurized Volumetric Solar Receiver for Supercritical CO2 Brayton Cycle

2014 ◽  
Author(s):  
S. D. Khivsara ◽  
Rathindra Nath Das ◽  
T. L. Thyagaraj ◽  
Shriya Dhar ◽  
V. Srinivasan ◽  
...  
Keyword(s):  
Thermal Efficiency ◽  
Supercritical Co2 ◽  
Material Selection ◽  
Radiation Heat Transfer ◽  
Small Scale ◽  
Attractive Alternative ◽  
Transfer Model ◽  
Outlet Temperature ◽  
Brayton Cycle ◽  
Solar Thermal Energy

Recently, the supercritical CO2 (s-CO2) Brayton cycle has been identified as a promising candidate for solar-thermal energy conversion due to its potentially high thermal efficiency (50%, for turbine inlet temperatures of ∼ 1000K). Realization of such a system requires development of solar receivers which can raise the temperature of s-CO2 by over 200K, to a receiver outlet temperature of 1000K. Volumetric receivers are an attractive alternative to tubular receivers due to their geometry, functionality and reduced thermal losses. A concept of a ceramic pressurized volumetric receiver for s-CO2 has been developed in this work. Computational Fluid Dynamics (CFD) analysis along with a Discrete Ordinate Method (DOM) radiation heat transfer model has been carried out, and the results for temperature distribution in the receiver and the resulting thermal efficiency are presented. We address issues regarding material selection for the absorber structure, window, coating, receiver body and insulation. A modular small scale prototype with 0.5 kWth solar heat input has been designed. The design of a s-CO2 loop for testing this receiver module is also presented in this work.

Sustainability Metrics of a Small Scale Turbojet Engine

2018 ◽  
Vol 35 (2) ◽  
pp. 113-119 ◽  
Author(s):  
Selcuk Ekici ◽  
Yasin Sohret ◽  
Kahraman Coban ◽  
Onder Altuntas ◽  
T. Hikmet Karakoc
Keyword(s):  
Exergy Efficiency ◽  
Sustainability Indicators ◽  
Aviation Industry ◽  
Small Scale ◽  
Exergy Destruction ◽  
The Sustainable Development ◽  
Effect Factor ◽  
Sustainability Index ◽  
Turbojet Engine ◽  
Power Load

Abstract Over the last decade, sustainable energy consumption has attracted the attention of scientists and researchers. The current paper presents sustainability indicators of a small scale turbojet engine, operated on micro-aerial vehicles, for discussion of the sustainable development of the aviation industry from a different perspective. Experimental data was obtained from an engine at full power load and utilized to conduct an exergy-based sustainability analysis. Exergy efficiency, waste exergy ratio, recoverable exergy ratio, environmental effect factor, exergy destruction factor and exergetic sustainability index are evaluated as exergetic sustainability indicators of the turbojet engine under investigation in the current study. The exergy efficiency of the small scale turbojet engine is calculated as 27.25 % whereas the waste exergy ratio, the exergy destruction factor and the sustainability index of the engine are found to be 0.9756, 0.5466 and 0.2793, respectively.

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