On Experimental and Computational Investigation of Heat Transfer Deterioration and Hydraulic Resistance in Annular Channel and SCWR 3-Rod Bundle

2018 ◽  
Author(s):  
Vladislav V. Filonov ◽  
Yuliia S. Filonova ◽  
Victor G. Razumovskiy ◽  
Evgeniy N. Pis'mennyi
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Pressure Drop ◽  
Thermal State ◽  
Annular Channel ◽  
Operating Conditions ◽  
Mass Rate ◽  
Heat Transfer Deterioration ◽  
Annular Channels ◽  
Vertical Annuli

The experiments on upward flow of supercritical water in a vertical annuli and 3-rod tight bundle simulator made of 485-mm heated-length tubes of 5.2-mm OD and 4.5-mm ID with four helical ribs of 0.6-mm height, 1-mm width, and axial 400-mm pitch are presented. Heat transfer and pressure drop under various operating conditions (inlet pressure and temperature, flow mass rate and heat flux) were investigated. Longitudinal wall temperature profiles made it possible to determine the place and flow thermal state of heat transfer deterioration (HTD) onset. Analysis of the obtained data (about 200 regimes) proved their good enough agreement with the correlations previously derived by the authors both for the heat flux rate (q/G)b of HTD beginning and for pressure drop in round tubes and annular channels. These correlations were updated to correct the results of their prediction. Computational fluid dynamics and its counterpart computational heat transfer were used for modeling the above-mentioned thermohydraulic processes studied in the first part of the work by finding the most adequate flow turbulence model and optimized domain meshing. The accepted model was benchmarked by some data on heat transfer and pressure drop in tubes and annular channels cooled by SCW.

Numerical Investigation on Heat Transfer to Supercritical CO2 in Vertical Annular Channel

2016 ◽  
Author(s):  
Zhenxing Zhao ◽  
Jun Wu ◽  
Fan Bai ◽  
Qi Xiao ◽  
Chunhui Dai ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Supercritical Fluid ◽  
Annular Channel ◽  
Outer Wall ◽  
Wall Heat Transfer ◽  
Heat Transfer Characteristics ◽  
Heat Transfer Deterioration ◽  
Flow And Heat Transfer ◽  
Wall Heating

The special fluid flow and heat transfer characteristics of supercritical CO2 in a vertical annular channel have been numerically investigated. The AKN k-ε model was selected to model the turbulent flow and heat transfer of supercritical fluid. The three heating types were individual outer-wall heating, simultaneous outer/inner walls heating and outer-wall heating (inner-wall cooling) separately. The local heat transfer coefficients were obtained to investigate the influence of inner-wall thermal boundary conditions, supercritical fluid mass flux, fluid temperature and flow direction on outer-wall heat transfer phenomenon. The mechanisms of abnormal heat transfer and primary influence factors were analyzed by the detailed information on the flow, turbulence and thermal fields. When the supercritical fluid is in the large-property-variation (LPV) region and flows upward, the inner-wall thermal boundary condition obviously affects the heat transfer characteristics of outer wall. When supercritical fluid flows downward, the inner-wall boundary condition hardly affects the heat transfer phenomena of outer wall. The increase of inner-wall heating heat flux will result in the larger deterioration region and heat transfer decline on outer wall when the other conditions remain unchanged. When the heat transfer deterioration also appears on the inner wall with the increase in the inner-wall heat flux, the outer-wall heat transfer no longer decreases, but the deterioration region abruptly increases. However, as inner-wall cooling heat flux increases, the heat transfer deterioration phenomenon on outer wall will weaken gradually.

scholarly journals Investigation of R134a Flow Boiling Heat Transfer and Pressure Drop in the Evaporator Test Section of Refrigeration System

2018 ◽  
Vol 25 (1) ◽  
pp. 13-31
Author(s):  
Ahmed J. Hamad ◽  
Zahraa Kareem Yasser
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Flow Boiling ◽  
Saturation Temperature ◽  
Operating Conditions ◽  
Refrigeration System ◽  
Test Conditions

This paper presents an experimental and theoretical analysis to investigate the two-phase flow boiling heat transfer coefficient and pressure drop of the refrigerant R-134a in the evaporator test section of the refrigeration system under different operating conditions. The test conditions considered are, for heat flux (13.7-36.6) kW/m2, mass flux (52-105) kg/m2.s, vapor quality (0.2-1) and saturation temperature (-15 to -3.7) ˚C. Experiments were carried out using a test rig for a 310W capacity refrigeration system, which is designed and constructed in the current work. Investigating of the experimental results has revealed that, the enhancement in local heat transfer coefficient for relatively higher heat flux 36.6 kW/m2 was about 38% compared to 13.7 kW/m2 at constant operating conditions. The enhancement in heat transfer coefficient was about 57% when the mass flux increased from 52 kg/m2.s to 105 kg/m2.s at constant test conditions. The enhancement in the heat transfer coefficient was about 64% when the saturation temperature increased from -8 to -3.7 at fixed refrigerant mass velocity and heat flux. The effect of mass velocity on pressure drop was relatively higher by about 27% than that for heat flux at specified test conditions. The comparison between the experimental and theoretical results has shown an acceptable agreement with an average deviation of 21%.  

Novel Arrangement of Rough Tubes for Heat Flux Improvement

2012 ◽  
Vol 326-328 ◽  
pp. 81-86
Author(s):  
Farshad Farahbod ◽  
Sara Farahmand ◽  
Farzaneh Farahbod
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Crude Oil ◽  
Transfer Coefficient ◽  
Three Dimensional ◽  
Operating Conditions ◽  
Set Up ◽  
The Heat Transfer Coefficient

The objective of the research is to represent a novel arrangement of conical three dimensional rough tubes (FS3D) for heat transfer coefficient enhancement. Experiments were performed with 316 stainless steel tubes of FS3D roughness and hot crude oil was circulated in constant heat flux condition in the related set up. The pressure drop is measured in this set up and compared with the pressure drop in a smooth tube with the same operating conditions. The heat transfer coefficient is one of essential parameters for design of heat transfer equipments and in this experimental work this is investigated for an Iranian crude oil in the FS3D rough tube. The heat transfer coefficient in FS3D rough tubes is higher than in other commercial enhanced tubes. FS3D rough tubes improve the performance of heat transfer equipments and also optimize the size of the mentioned devices. Consequently this type, the FS3D rough tube, is advantageous in energy and cost saving.

scholarly journals Investigation of the influence of Taylor-Gortler vortexes on heat transfer of annular channel

2021 ◽  
Vol 2039 (1) ◽  
pp. 012026
Author(s):  
E V Pankratov
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Radial Velocity ◽  
Heat Flux Density ◽  
Annular Channel ◽  
Swirling Flows ◽  
Velocity Fluctuations ◽  
Annular Channels ◽  
Channel Surface ◽  
Flux Density Distribution

Abstract This article is about the influence of Taylor-Gortler vortices on heat transfer in concentric annular channels with turbulent decaying swirling flows. The study shows that the occurrence and transformation of secondary vortex structures has a significant effect on the distribution of heat flux over the annular channel surface. An explicit is relationship between the radial velocity fluctuations and the heat flux density distribution. The highest intensity of heat transfer on the outer surface is observed in the areas of positive radial velocity values, while on the inner surface it is observed in the areas of negative radial velocity values.

Heat Transfer to Supercritical Water in Vertical Annular Channel and 3-Rod Bundle

2009 ◽  
Author(s):  
V. G. Razumovskiy ◽  
Eu. N. Pis’mennyy ◽  
A. Eu. Koloskov ◽  
I. L. Pioro
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Supercritical Water ◽  
Annular Channel ◽  
Heat Fluxes ◽  
Inlet Temperature ◽  
Outlet Temperature ◽  
Rod Bundle ◽  
Temperature Regimes ◽  
Outside Diameter

The results of heat transfer to supercritical water flowing upward in a vertical annular channel (1-rod channel) and tight 3-rod bundle consisting of the tubes of 5.2-mm outside diameter and 485-mm heated length are presented. The heat-transfer data were obtained at pressures of 22.5, 24.5, and 27.5 MPa, mass flux within the range from 800 to 3000 kg/m2·s, inlet temperature from 125 to 352°C, outlet temperature up to 372°C and heat flux up to 4.6 MW/m2 (heat flux rate up to 2.5 kJ/kg). Temperature regimes of the annular channel and 3-rod bundle were stable and easily reproducible within the whole range of the mass and heat fluxes, even when a deteriorated heat transfer took place. The data resulted from the study could be applicable for a reference estimation of heat transfer in future designs of fuel bundles.

Embedded Two-Phase Cooling of High Flux Electronics via Micro-Enabled Surfaces and Fluid Delivery Systems (FEEDS)

2015 ◽  
Author(s):  
Raphael Mandel ◽  
Serguei Dessiatoun ◽  
Patrick McCluskey ◽  
Michael Ohadi
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Pressure Drop ◽  
Saturation Temperature ◽  
Absolute Pressure ◽  
High Flux ◽  
Vapor Quality ◽  
Two Phase ◽  
Fluid Delivery ◽  
Future Work

This work presents the experimental design and testing of a two-phase, embedded manifold-microchannel cooler for cooling of high flux electronics. The ultimate goal of this work is to achieve 0.025 cm2-K/W thermal resistance at 1 kW/cm2 heat flux and evaporator exit vapor qualities at or exceeding 90% at less than 10% absolute pressure drop. While the ultimate goal is to obtain a working two-phase embedded cooler, the system was first tested in single-phase mode to validate system performance via comparison of experimentally measured heat transfer coefficient and pressure drop to the values predicted by CFD simulations. Upon validation, the system was tested in two phase mode using R245fa at 30°C saturation temperature and achieved in excess of 1 kW/cm2 heat flux at 45% vapor quality. Future work will focus on increasing the exit vapor quality as well as use of SiC for the heat transfer surface upon completion of current experiments with Si.

Numerical Study of Deteriorated Convection Heat Transfer of Supercritical Fluid Flowing Through Vertical Mini Tube at Relatively Low Reynolds Numbers

2018 ◽  
Author(s):  
Chen-Ru Zhao ◽  
Zhen Zhang ◽  
Qian-Feng Liu ◽  
Han-Liang Bo ◽  
Pei-Xue Jiang
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Reynolds Number ◽  
Low Reynolds Number ◽  
Convection Heat Transfer ◽  
Turbulence Models ◽  
Convection Heat ◽  
Flow Acceleration ◽  
Heat Transfer Deterioration ◽  
Low Reynolds

Numerical investigations are performed on the convection heat transfer of supercritical pressure fluid flowing through vertical mini tube with inner diameter of 0.27 mm and inlet Reynolds number of 1900 under various heat fluxes conditions using low Reynolds number k-ε turbulence models due to LB (Lam and Bremhorst), LS (Launder and Sharma) and V2F (v2-f). The predictions are compared with the corresponding experimentally measured values. The prediction ability of various low Reynolds number k-ε turbulence models under deteriorated heat transfer conditions induced by combinations of buoyancy and flow acceleration effects are evaluated. Results show that all the three models give fairly good predictions of local wall temperature variations in conditions with relatively high inlet Reynolds number. For cases with relatively low inlet Reynolds number, V2F model is able to capture the general trends of deteriorated heat transfer when the heat flux is relatively low. However, the LS and V2F models exaggerate the flow acceleration effect when the heat flux increases, while the LB model produces qualitative predictions, but further improvements are still needed for quantitative prediction. Based on the detailed flow and heat transfer information generated by simulation, a better understanding of the mechanism of heat transfer deterioration is obtained. Results show that the redistribution of flow field induced by the buoyancy and flow acceleration effects are main factors leading to the heat transfer deterioration.

A Study on Flow Boiling in Microchannel With Piranha Pin Fin

2015 ◽  
Author(s):  
X. Yu ◽  
C. Woodcock ◽  
Y. Wang ◽  
J. Plawsky ◽  
Y. Peles
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Fluid Flow ◽  
Pressure Drop ◽  
Heat Transfer Performance ◽  
Flow Boiling ◽  
Transfer Performance ◽  
Flow Conditions ◽  
Pin Fin ◽  
Flow And Heat Transfer

In this paper we reported an advanced structure, the Piranha Pin Fin (PPF), for microchannel flow boiling. Fluid flow and heat transfer performance were evaluated in detail with HFE7000 as working fluid. Surface temperature, pressure drop, heat transfer coefficient and critical heat flux (CHF) were experimentally obtained and discussed. Furthermore, microchannels with different PPF geometrical configurations were investigated. At the same time, tests for different flow conditions were conducted and analyzed. It turned out that microchannel with PPF can realize high-heat flux dissipation with reasonable pressure drop. Both flow conditions and PPF configuration played important roles for both fluid flow and heat transfer performance. This study provided useful reference for further PPF design in microchannel for flow boiling.

Experimental Study of Heat Transfer to Supercritical Pressure Water Flowing in a 2×2 Rod Bundle

2014 ◽  
Author(s):  
Han Wang ◽  
Qincheng Bi ◽  
Linchuan Wang ◽  
Haicai Lv ◽  
Laurence K. H. Leung
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Heat Flux ◽  
Pressure Drop ◽  
Wall Temperature ◽  
Mass Flux ◽  
Heat Fluxes ◽  
Outer Diameter ◽  
Square Channel ◽  
Rod Bundle

An experiment has recently been performed at Xi’an Jiaotong University to study the wall temperature and pressure drop at supercritical pressures with upward flow of water inside a 2×2 rod bundle. A fuel-assembly simulator with four heated rods was installed inside a square channel with rounded corner. The outer diameter of each heated rod is 8 mm with an effective heated length of 600 mm. Experimental parameters covered the pressure of 23–28 MPa, mass flux of 350–1000 kg/m2s and heat flux on the rod surface of 200–1000 kW/m2. According to the experimental data, it was found that the circumferential wall temperature distribution of a heated rod is not uniform. The temperature difference between the maximum and the minimum varies with heat flux and/or mass flux. Heat transfer characteristics of supercritical water in bundle were discussed with respect to various heat fluxes. The effect of heat flux on heat transfer in rod bundles is similar with that in tubes or annuli. In addition, flow resistance reflected in the form of pressure loss has also been studied. Experimental results showed that the total pressure drop increases with bulk enthalpy and mass flux. Four heat transfer correlations developed for supercritical pressures water were compared with the present test data. Predictions of Jackson correlation agrees closely with the experimental data.

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