scholarly journals Experimental Investigation on Heat Transfer of Supercritical Water Flowing in the Subchannel with Grid Spacer in Supercritical Water-Cooled Reactor

Energies ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1016
Author(s):  
Weishu Wang ◽  
Lingwei Guo ◽  
Ge Zhu ◽  
Xiaojing Zhu ◽  
Qincheng Bi
Keyword(s):  
Heat Transfer ◽  
Mass Flow ◽  
Supercritical Water ◽  
Heat Transfer Performance ◽  
Heat Fluxes ◽  
Experimental Investigations ◽  
Grid Function ◽  
Transfer Performance ◽  
Supercritical Water Cooled Reactor ◽  
The Impact

Experimental investigations on the heat transfer performance of supercritical water flowing in the subchannel of supercritical water-cooled reactor (SCWR) simulated by a triangular channel were conducted at pressures of 23–28 MPa, mass flow rates of 700–1300 kg·m−2·s−1, and inner wall surface heat fluxes of 200–600 kW·m−2. An 8 mm diameter fuel rod with a 1.4 pitch to diameter ratio was used. The effects of pressure, mass flow rate, and heat flux on the heat transfer performance under the resistance of a standard grid spacer were analyzed. Experimental results showed the significant positive influence of the grid spacer on the supercritical water in the subchannel. Moreover, in the presence of the grid spacer, the parameters influenced the heat transfer with different degrees of strengthening reaction. In view of the phenomenon in the tests, the rule of the supercritical heat transfer was further revealed by the comparison between empirical formulas and experimental data. This paper mainly studied the positioning grid function and the fluid flow characteristics downstream of the subchannel under the influence of the standard grid spacer and the impact mechanism of each parameter on the whole heat transfer process coefficient.

Study of Impact of Gas Cooler Cooling Circuit on Heat Transfer Performance

2012 ◽  
Vol 236-237 ◽  
pp. 224-229
Author(s):  
Bing Qiang He ◽  
Chun Ling Liao
Keyword(s):  
Heat Transfer ◽  
Mass Flow ◽  
Heat Transfer Performance ◽  
Experimental Tests ◽  
Transfer Performance ◽  
Cell Type ◽  
Cooling Circuit ◽  
Transfer Processes ◽  
The Impact ◽  
Side Flow

Experimental study on the structure and characteristics of cooling circuit of full-aluminum parallel flow gas cooler. The experimental tests on the built cell-type and ternary GCMCPF are conducted. In the heat transfer processes of the cooler with different circuit structures, the impact of CO2 refrigerant side flow resistance and the mass flow on the heat transfer performance of gas cooler is measured. The results show that the ternary type GCMCPF structure can enhance the heat transfer for CO2 fluid at the weak heat transfer area in the cell-type GCMCPF. Within a certain range of mass flow, the former heat transfer is 1.5 times the later one, and the structural sizes of GCMCPF can be reduced in the same requirements for heat transfer.

scholarly journals Entropy Generation and Heat Transfer Performance in Microchannel Cooling

Entropy ◽  
2019 ◽  
Vol 21 (2) ◽  
pp. 191 ◽  
Author(s):  
Jundika Kurnia ◽  
Desmond Lim ◽  
Lianjun Chen ◽  
Lishuai Jiang ◽  
Agus Sasmito
Keyword(s):  
Heat Transfer ◽  
Entropy Generation ◽  
Heat Transfer Performance ◽  
Second Law Of Thermodynamics ◽  
High Heat ◽  
Heat Fluxes ◽  
Transfer Performance ◽  
Cooling Channel ◽  
High Heat Transfer ◽  
Microchannel Cooling

Owing to its relatively high heat transfer performance and simple configurations, liquid cooling remains the preferred choice for electronic cooling and other applications. In this cooling approach, channel design plays an important role in dictating the cooling performance of the heat sink. Most cooling channel studies evaluate the performance in view of the first thermodynamics aspect. This study is conducted to investigate flow behaviour and heat transfer performance of an incompressible fluid in a cooling channel with oblique fins with regards to first law and second law of thermodynamics. The effect of oblique fin angle and inlet Reynolds number are investigated. In addition, the performance of the cooling channels for different heat fluxes is evaluated. The results indicate that the oblique fin channel with 20° angle yields the highest figure of merit, especially at higher Re (250–1000). The entropy generation is found to be lowest for an oblique fin channel with 90° angle, which is about twice than that of a conventional parallel channel. Increasing Re decreases the entropy generation, while increasing heat flux increases the entropy generation.

Optimization of a U-Bend for Minimal Pressure Loss in Internal Cooling Channels—Part II: Experimental Validation

2013 ◽  
Vol 135 (5) ◽  
Author(s):  
Filippo Coletti ◽  
Tom Verstraete ◽  
Jérémy Bulle ◽  
Timothée Van der Wielen ◽  
Nicolas Van den Berge ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Pressure Loss ◽  
Heat Transfer Performance ◽  
Internal Cooling ◽  
Transfer Performance ◽  
Cooling Channel ◽  
Piv Measurements ◽  
Cooling Channels ◽  
Numerical Predictions ◽  
The Impact

This two-part paper addresses the design of a U-bend for serpentine internal cooling channels optimized for minimal pressure loss. The total pressure loss for the flow in a U-bend is a critical design parameter, as it augments the pressure required at the inlet of the cooling system, resulting in a lower global efficiency. In the first part of the paper, the design methodology of the cooling channel was presented. In this second part, the optimized design is validated. The results obtained with the numerical methodology described in Part I are checked against pressure measurements and particle image velocimetry (PIV) measurements. The experimental campaign is carried out on a magnified model of a two-legged cooling channel that reproduces the geometrical and aerodynamical features of its numerical counterpart. Both the original profile and the optimized profile are tested. The latter proves to outperform the original geometry by about 36%, in good agreement with the numerical predictions. Two-dimensional PIV measurements performed in planes parallel to the plane of the bend highlight merits and limits of the computational model. Despite the well-known limits of the employed eddy viscosity model, the overall trends are captured. To assess the impact of the aerodynamic optimization on the heat transfer performance, detailed heat transfer measurements are carried out by means of liquid crystals thermography. The optimized geometry presents overall Nusselt number levels only 6% lower with respect to the standard U-bend. The study demonstrates that the proposed optimization method based on an evolutionary algorithm, a Navier–Stokes solver, and a metamodel of it is a valid design tool to minimize the pressure loss across a U-bend in internal cooling channels without leading to a substantial loss in heat transfer performance.

Numerical Modeling of Turbulent Flow and Heat Transfer Within a Bayonet Tube

2007 ◽  
Author(s):  
Feng Sun ◽  
G.-X. Wang
Keyword(s):  
Heat Transfer ◽  
Turbulent Flow ◽  
Heat Transfer Performance ◽  
Numerical Study ◽  
Experimental Result ◽  
Working Fluid ◽  
Transfer Performance ◽  
Flow And Heat Transfer ◽  
Air Jet ◽  
The Impact

This paper presents a numerical study of turbulent flow and heat transfer in a bayonet tube under steady state. First, various turbulent models and wall treatment methods have been tested and validated against the experimental result from a turbulent air jet. The proper combination of turbulent model and wall treatment is then recommended for the turbulent flow within a bayonet tube. The study focuses on the heat transfer performance at the interface of working fluid and the outer tube wall under different Reynolds numbers. Various geometry parameters are considered in this work and the impact of geometry on the heat transfer performance is investigated. Results indicate that the heat transfer at the bottom of the bayonet tube is enhanced compared with that at the straight part. At low Re (< 8000), the maximum Nu occurs at the stagnation point, while the position of the maximum Nu moves away from the stagnant point as Re exceeds 8000. The results are believed to be helpful for the optimized design of a bayonet tube with fully turbulent flows.

Experimental Investigation of Area Ratio on Microjet Array Heat Transfer

2009 ◽  
Author(s):  
Gregory J. Michna ◽  
Eric A. Browne ◽  
Yoav Peles ◽  
Michael K. Jensen
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Performance ◽  
Electronics Cooling ◽  
Jet Impingement ◽  
Area Ratio ◽  
Heat Fluxes ◽  
Working Fluid ◽  
Transfer Performance ◽  
Transfer Coefficients ◽  
High Heat Transfer

Electronics cooling is becoming increasingly difficult due to increasing power consumption and decreasing size of processor chips. Heat fluxes in processors and power electronics are quickly approaching levels that cannot be easily addressed by forced air convection over finned heat sinks. Jet impingement cooling offers high heat transfer coefficients and has been used effectively in conventional-scale applications such as turbine blade cooling and the quenching of metals. However, literature in the area of microjet arrays is scarce and has not studied arrays of large area ratios. Hence, the objective of this study is to experimentally assess the heat transfer performance of arrays of microjets. The microjet arrays were fabricated using MEMS processes in a clean room environment. The heat transfer performance of several arrays using deionized water as the working fluid was investigated. Inline and staggered array arrangements were investigated, and the area ratio (total area of the jets divided by the surface area) was varied between 0.036 and 0.35. Reynolds numbers defined by the jet diameter were in the range of 50 to 3,500. Heat fluxes greater than 1,000 W/cm2 were obtained at fluid inlet-to-surface temperature differences of less than 30 °C. Heat transfer performance improved as the area ratio was increased.

Heat Transfer Enhancement in Micro-Domains Using Gas-Driven Liquid Film

2012 ◽  
Author(s):  
Farzad Houshmand ◽  
Yoav Peles ◽  
Michael Amitay
Keyword(s):  
Heat Transfer ◽  
Liquid Film ◽  
Gas Flow ◽  
Single Phase ◽  
Heat Transfer Performance ◽  
Main Stream ◽  
Transfer Performance ◽  
Rectangular Microchannel ◽  
Heated Area ◽  
The Impact

A liquid film has been introduced upstream of a heater in a microchannel with gas flow, and the impact on the heat transfer performance has been investigated. The shear force exerted by the gas flow on the gas-liquid interface drives the film and drags it downstream, onto the heated area. Distilled water was injected through a 350 μm circular hole in a main stream of Nitrogen in a 220 μm deep and 1.5 mm wide rectangular microchannel to enhance the heat transfer from a 1 mm × 1 mm heater. Average heat transfer coefficient was studied for different gas and liquid flow rates and compared with single-phase flow. Significant improvement in heat transfer performance was observed while the pressure drop in the channel was not increased dramatically.

The Technical Derivation of Heat Transfer Performance of the Airside of a Novel Pin Design Heat Exchanger Using Computational Fluid Dynamics

2012 ◽  
Author(s):  
Tosha Churitter
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Heat Exchanger ◽  
Mass Flow ◽  
Heat Exchangers ◽  
Heat Transfer Performance ◽  
Diameter Ratio ◽  
Transfer Performance ◽  
Extended Surface

Pins are a common type of extended surface used in the field of heat transfer; their main application being in the electronics field. Historically, pins used in heat exchangers have diameters that are considered negligible in comparison to their lengths and are therefore termed as tubes. In this report, the use of pins as an extended surface is investigated for the heat transfer on the airside (cold) of the Compact Advanced Pin Surface Heat Exchanger. The pins are circular in cross section and follow a staggered arrangement. The uniqueness of the pin design is such that they cannot be treated as tubes. Key Pin Design features are as follows: • Pins have a maximum Length: Diameter ratio of 3. • Pin Spacing to Pin Diameter ratio is greater than in traditional arrangements. • Pins function as a primary as well as secondary surface. The heat transfer performance of extended surfaces possessing the above features has not been characterized, using commercially available Computational Fluid Dynamics (CFD) software, in any research specifically focused on applications for the aerospace industry. Based on actual test results, this study specially develops a unique approach that can predict the outlet temperature of the heat exchanger to within 1% accuracy. This ‘developed’ approach is applied over cold-side mass flow rates ranging from 0.05 kg/s to 0.23 kg/s, while keeping the hot side mass flow rate constant at 0.05 kg/s. At worst, the simulation results lie within 5% accuracy and at best the simulation accuracy is 1%, a significant improvement on traditional derivations. This article specifically discusses the methodology developed to analyse the heat transfer performance of the novel pin design using Fluent 6.2. It highlights the current limitations of existing equations as well as the theoretical knowledge gap that currently exists in the analysis of pins as extended heat transfer surfaces in heat exchangers.

Nucleate Pool Boiling on Tubes With Subsurface Mini and Micro Channels

2008 ◽  
Author(s):  
Peter Stephan ◽  
Frank Wondra
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Performance ◽  
Standard Procedure ◽  
Model Development ◽  
Heat Fluxes ◽  
Optical Measurements ◽  
Transfer Performance ◽  
Performance Measurements ◽  
Micro Channels ◽  
Physically Based

Tubes with subsurface mini- and micro channels are widely used in boiling devices. Today, the design of these tubes is based on empirical investigations because reliable theoretical or numerical design methods are not available, and the heat transfer performance characteristics vary strongly e.g. for different fluids, system pressures and heat fluxes. The presented study approaches the subject of interest from 3 different paths: (i) macroscopic heat transfer performance measurements; (ii) optical measurements of the thermal and hydrodynamic phenomena inside the subsurface channels with very high spatial and temporal resolution; (iii) development of a computational model. While path (i) is a standard procedure in the scientific community, path (ii) is a completely new approach, and only the combination of (i) and (ii) is a solid basis for the physically based model development in path (iii). Tubes with different subsurface channels and micro pin-fins are used in combination with different fluids at different system pressures. The results are presented and discussed.

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