Steady-State Energetic and Exergetic Performances of Single-Phase Natural Circulation Loop With Hybrid Nanofluids

2019 ◽  
Vol 141 (8) ◽  
Author(s):  
Mayaram Sahu ◽  
Jahar Sarkar
Keyword(s):  
Steady State ◽  
Mass Flow Rate ◽  
Entropy Generation ◽  
Mass Flow ◽  
Flow Rate ◽  
Natural Circulation ◽  
Circulation Loop ◽  
Hybrid Nanofluid ◽  
Natural Circulation Loop ◽  
Hybrid Nanofluids

Energy and exergy performances of natural circulation loop (NCL) with various water-based hybrid nanofluids (Al2O3 + TiO2, Al2O3 + CNT, Al2O3 + Ag, Al2O3 + Cu, Al2O3 + CuO, Al2O3 + graphene) with 1% volumetric concentration are compared in this study. New thermophysical property models have been proposed for hybrid nanofluids with different particle shapes and mixture ratio. Effects of power input, loop diameter, loop height, loop inclination and heater/cooler inclination on steady-state mass flow rate, effectiveness, and entropy generation are discussed as well. Results show that both the steady-state mass flow rate and energy–exergy performance are enhanced by using the hybrid nanofluids, except Al2O3 + graphene, which shows the performance decrement within the studied power range. Al2O3 + Ag hybrid nanofluid shows highest enhancement in mass flow rate of 4.8% compared to water. The shape of nanoparticle has shown a significant effect on steady-state performance; hybrid nanofluid having cylindrical and platelet shape nanoparticles yields lower mass flow rate than that of spherical shape. Mass flow rate increases with the increasing loop diameter and height, whereas decreases with the increasing loop and heater/cooler inclinations. Both effectiveness and entropy generation increase with the decreasing loop diameter and height, whereas increasing the loop and heater/cooler inclinations. This study reveals that the particle shape has a significant effect on the performance of hybrid nanofluids in NCL, and the use of hybrid nanofluid is more effective for higher power.

Single-phase natural circulation loop using oils and ternary hybrid nanofluids: Steady-state and transient thermo-hydraulics

2020 ◽  
pp. 1-32
Author(s):  
Mayaram Sahu ◽  
Jahar Sarkar ◽  
Laltu Chandra
Keyword(s):  
Steady State ◽  
Mass Flow Rate ◽  
Entropy Generation ◽  
Mass Flow ◽  
Flow Rate ◽  
Generation Rate ◽  
Entropy Generation Rate ◽  
Width Ratio ◽  
Total Entropy ◽  
Hybrid Nanofluids

Abstract Steady-state and transient behaviours of single-phase natural circulation loop (SPNCL) are investigated using four thermal oils (Therminol VP1, Paratherm CR, Dowtherm A and Dowtherm Q) and water-based ternary hybrid (various combinations of different nature and shaped nanoparticles: Al2O3, Cu, CNT and Graphene) nanofluids as loop fluid. The influences of nanoparticle volume concentration and loop height to width ratio on the mass flow rate and total entropy generation rate of SPNCL are investigated. Results disclose that ternary hybrid nanofluids enhance flow initiation, reduce fluctuation and are expected to attain a steady-state faster than water. Steady-state mass flow rate increases/decreases for ternary hybrid nanofluid depending on the shape of the nanoparticle and total entropy generation rate decreases as compared to water. Thermal oil shows a higher mass flow rate and total entropy generation rate as compared to water. Al2O3-Cu-CNT-water and paratherm CR show the best result among all ternary hybrid nanofluids and thermal oils, respectively. The nanoparticle shape decides the optimum nanoparticle volume fraction. Increasing the height to width ratio decreases the total entropy generation and upsurges the mass flow rate at specified input power. The optimum height to width ratio depends on fluid.

Experimental Studies on Nanofluid-Based Rectangular Natural Circulation Loop

2019 ◽  
Vol 11 (4) ◽  
Author(s):  
Ramesh Babu Bejjam ◽  
K. Kiran Kumar ◽  
Karthik Balasubramanian
Keyword(s):  
Nusselt Number ◽  
Steady State ◽  
Rayleigh Number ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Thermal Performance ◽  
Natural Circulation ◽  
Working Fluids ◽  
Natural Circulation Loop

The main objective of the present study is to carry out experimental investigation on thermal performance of the nanofluid-based rectangular natural circulation loop (NCL). For this study, an experimental test rig is fabricated with heater as heat source, and tube in tube heat exchanger as heat sink. For the experimentation, three different nanofluids are used as working fluids. The nanometer-sized particles of silicon dioxide (SiO2), copper oxide (CuO), and alumina (Al2O3) are dispersed in distilled water to produce the nanofluids at different volume concentrations ranging from 0.5% to 1.5%. Experiments are carried out at different power inputs and different cold fluid inlet temperatures. The results indicate that NCL operating with nanofluid reaches steady-state condition quickly, when compared to water due to its increased thermal conductivity. The steady-state reaching time is reduced by 12–27% by using different nanofluids as working fluids in the loop when compared to water. The thermal performance parameters like mass flow rate, Rayleigh number, and average Nusselt number of the nanofluid-based NCL are improved by 10.95%, 16.64%, and 8.10%, respectively, when compared with water-based NCL. At a given power input, CuO–water nanofluid possess higher mass flow rate, Rayleigh number and Nusselt number than SiO2–water and Al2O3–water nanofluids due to better thermo-rheological properties.

Two-phase natural circulation loop behaviour at atmospheric and subatmospheric conditions

2018 ◽  
Vol 233 (4) ◽  
pp. 687-700
Author(s):  
S Venkata Sai Sudheer ◽  
K Kiran Kumar ◽  
Karthik Balasubramanian
Keyword(s):  
Heat Flux ◽  
Physical Properties ◽  
Spatial Variation ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Natural Circulation ◽  
Two Phase ◽  
Natural Circulation Loop ◽  
Thermo Physical Properties

This paper aims to present the steady-state behaviour of two-phase natural circulation loop at atmospheric and sub-atmospheric conditions. One-dimensional numerical approach is adopted to evaluate various system parameters, with special emphasis on spatial variation of thermo-physical properties and flashing. Homogeneous equilibrium model is applied for two-phase flows. An in-house code is developed in MATLAB to solve numerical model iteratively. It is observed that consideration of spatial variation of thermo-physical properties can precisely predict the loop behaviour. The evaluated results are validated with the open literature and reasonably good agreement is observed. The heater inlet temperature, inlet pressure and heat flux are found to have significant influence on spatial variation of pressure, temperature and enthalpy. As system pressure decreases from atmospheric to sub-atmospheric (1–0.8 atm), it is observed that the sub-atmospheric loop gives a higher mass flow rate compared to atmospheric loop at lower heat fluxes. However, as the heat flux increases in the sub-atmospheric loop, the mass flow rate is reduced due to increased drag force in the loop.

Experimental Observation of the General Trends of the Steady State and Instability Behavior of Supercritical Water Natural Circulation

2013 ◽  
Author(s):  
Fa Lv ◽  
Yan-ping Huang ◽  
Yan-lin Wang ◽  
Xiao Yan
Keyword(s):  
Steady State ◽  
Water Temperature ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Supercritical Water ◽  
Natural Circulation ◽  
Water Pressure ◽  
Heating Power ◽  
Heated Zone

Experimental study on steady state and instability behavior of subcritical and supercritical water natural circulation was performed in a rectangular loop (NPIC-SCNCL) in NPIC, with the pressure of 10 and 21.1∼24.8MPa. According to the experimental results, in steady state the natural circulation displayed higher mass flow rate, heating power and outlet water temperature of the heated zone under supercritical pressure (22.2∼24.8Mpa) than those under subcritical pressure (10MPa). The effects of heating power and water pressure on the steady state behavior of supercritical water natural circulation were also carried out. In the experiments, natural circulation showed instability both in supercritical and subcritical conditions. The results showed that the natural circulation instability appeared when the outlet water temperature of the heated zone got close to the critical temperature under supercritcial pressure. In comparion, the natural circulation instability appeared when the outlet water temperature of the heated zone got close to the saturated temperature in subcritical condition. The instability behavior of supercritical water natural circulation showed the fluctuations of the mass flow rate, water temperature and pressure et al. In the experiments, we also observed that the fluctuations of the parameters mentioned above for supercritical water natural circulation instability could disappear when the heating power is big enough which seemed that the natural circulation returned to a new steady state.

Steady-State and Transient Analysis in Single-Phase Natural Circulation of ABV-6M

2010 ◽  
Author(s):  
Fangnian Wang ◽  
Zhaofei Tian ◽  
Jiange Liu
Keyword(s):  
Steady State ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Nuclear Power ◽  
Transient Analysis ◽  
Natural Circulation ◽  
Reactor Power ◽  
Secondary Circuit ◽  
Small Perturbations

This paper discusses the results of the thermal-hydraulic investigations of natural circulation. The RELAP5/MOD3.4 computer code has been used to simulate the natural circulation in an ABV-6M Nuclear Power Plant (NPP), and steady-state and transient operational characteristics are researched. Some results can be listed as follows. In the steady-state analysis, the relationship between the reactor power and the mass flow rate of primary loop, and the temperature difference of core inlet and outlet are obtained. The comparisons between the RELAP5 results and the theoretic calculation data indicate good general agreement. Besides, the mass flow rate of natural circulation will increase and the flow will become stable more quickly when the reactor power increases on the condition of the system with a fixed construction. The trends of the thermal parameters are obtained and the temperature envelope curve of secondary circuit fluid is ascertained. In the transient analysis, some perturbations, such as the fluctuations of feedwater temperature and feedwater mass flow rate, have influence on the system performance. Then, the comparisons between taking an action and not taking an action on Nitrogen Pressurizer are obtained when these small perturbations occur. It is turn out that the safety of natural circulation loop is sensitive to some small perturbations.

Pitfalls for Accurate Steady-State Port Flow Simulations

2012 ◽  
Author(s):  
Xiaofeng Yang ◽  
Zhaohui Chen ◽  
Tang-Wei Kuo
Keyword(s):  
Steady State ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Measured Data ◽  
Steady State Flow ◽  
Bench Tests ◽  
Flow Simulations ◽  
Mesh Topology ◽  
State Flow

Steady-state port flow simulations were carried out with a commercial three dimensional (3D) Computational Fluid Dynamics (CFD) code using Cartesian mesh with cut cells to study the prediction accuracy. The accuracy is assessed by comparing predicted and measured mass-flow rate and swirl and tumble torques at various valve lifts using different boundary condition setup and mesh topology relative to port orientation. The measured data is taken from standard steady-state flow bench tests of a production intake port. The predicted mass-flow rates agree to within 1% with the measured data between the intermediate and high valve lifts. At low valve lifts, slight over prediction in mass-flow rate can be observed. The predicted swirl and tumble torques are within 25% of the flow bench measurements. Several meshing parameters were examined in this study. These include: inlet plenum shape and outlet plenum/extension size, embedded sphere with varying minimum mesh size, finer meshes on port and valve surface, orientation of valve and port centerline relative to the mesh lines. For all model orientations examined, only the mesh topology with the valve axis aligned closely with the mesh lines can capture the mass-flow rate drop for very high valve lifts due to flow separation. This study further demonstrated that it is possible to perform 3D CFD flow analyses to adequately simulate steady-state flow bench tests.

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