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.

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.

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.

The Performance of a Novel Solar Cooling and Power System with Different Working Fluids

2014 ◽  
Vol 672-674 ◽  
pp. 86-93 ◽  
Author(s):  
Huan Lei ◽  
Jin Fu Yang ◽  
Dong Jiang Han
Keyword(s):  
Power System ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Thermal Performance ◽  
Supply And Demand ◽  
Heat Transfer Fluid ◽  
Working Fluid ◽  
Cooling Power ◽  
Working Fluids

Due to serious environmental problems and energy supply and demand issues, solar energy as a clean and abundant energy gets more and more attention. This paper presented a novel cooling and power system combined with PTCs. The system performance analysis was conducted with four different organic working fluids. The impacts of organic Rankine cycle (ORC) evaporation temperature, ORC condensing temperature and heat transfer fluid (HTF) mass flow rate in evaporator on system thermal performance were analyzed. The results show that system with toluene as working fluid has the highest thermal and exergy efficiency, and D4 and MDM have the lowest. Different working fluids have different cooling power to electricity ratios. The HTF mass flow rate in evaporator has a significant effect on system thermal performance.

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.

Heat Transfer and Flow Friction Characteristics for Compact Cold Plates

2003 ◽  
Vol 125 (1) ◽  
pp. 104-113 ◽  
Author(s):  
Chang-Yuan Liu ◽  
Ying-Huei Hung
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Nusselt Number ◽  
Thermal Resistance ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Average Nusselt Number ◽  
Cold Plate ◽  
Air Mass

Both experimental and theoretical investigations on the heat transfer and flow friction characteristics of compact cold plates have been performed. From the results, the local and average temperature rises on the cold plate surface increase with increasing chip heat flux or decreasing air mass flow rate. Besides, the effect of chip heat flux on the thermal resistance of cold plate is insignificant; while the thermal resistance of cold plate decreases with increasing air mass flow rate. Three empirical correlations of thermal resistance in terms of air mass flow rate with a power of −0.228 are presented. As for average Nusselt number, the effect of chip heat flux on the average Nusselt number is insignificant; while the average Nusselt number of the cold plate increases with increasing Reynolds number. An empirical relationship between Nu¯cp and Re can be correlated. In the flow frictional aspect, the overall pressure drop of the cold plate increases with increasing air mass flow rate; while it is insignificantly affected by chip heat flux. An empirical correlation of the overall pressure drop in terms of air mass flow rate with a power of 1.265 is presented. Finally, both heat transfer performance factor “j” and pumping power factor “f” decrease with increasing Reynolds number in a power of 0.805; while they are independent of chip heat flux. The Colburn analogy can be adequately employed in the study.

scholarly journals An experimental study of the thermal performance of the square and rhombic solar collectors

2018 ◽  
Vol 22 (1 Part B) ◽  
pp. 487-494 ◽  
Author(s):  
Aminreza Noghrehabadi ◽  
Ebrahim Hajidavaloo ◽  
Mojtaba Moravej ◽  
Ali Esmailinasab
Keyword(s):  
Experimental Study ◽  
Flat Plate ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Thermal Performance ◽  
Thermal Efficiency ◽  
Solar Collectors ◽  
Heating Systems ◽  
Solar Water Heating

Solar collectors are the key part of solar water heating systems. The most widely produced solar collectors are flat plate solar collectors. In the present study, two types of flat plate collectors, namely square and rhombic collectors are experi?mentally tested and compared and the thermal performance of both collectors is investigated. The results show both collectors have the same performance around noon (?61%), but the rhombic collector has better performance in the morning and afternoon. The values for rhombic and square collectors are approximately 56.2% and 53.5% in the morning and 56.1% and 54% in the afternoon, respectively. The effect of flow rate is also studied. The thermal efficiency of rhombic and square flat plate collectors increases in proportion to the flow rate. The results indicated the rhombic collector had better performance in comparison with the square collector with respect to the mass-flow rate.

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