Friction Factor Correlations Research Articles

Exploring nusselt number and friction factor correlations for sphere-shaped roughness elements on the absorber to enhance solar air heater efficiency

ABSTRACT This investigation is conducted to analyze the artificial surface roughness influence on the heat flow and friction characteristics within the ducts of solar air heaters (SAHs). This research aims to investigate the consequences of applying spherical-shaped surface roughness to the absorber in a linear and staggered manner with the intention of enhancing the heat transfer efficiency. The utilization of roughness elements in the shape of spheres is aimed at augmenting the heat transfer characteristics; however, it is crucial to acknowledge that this enhancement is concomitant with an elevation in pumping power due to heightened friction. An experimental campaign encom- passes a diverse set of operational and device parameters. These parameters include the Reynolds number (Re), which varies from 3,000 to 8,000. Additionally, the roughness pitch-to-height ratio (p/h) ranges from 10 to 20, while the roughness gap-to-height ratio (w/h) ranges from 4 to 8. Throughout the trials, a constant value of 0.06 is maintained for the roughness height-to-hydraulic diameter ratio (h/D) and an amount of 5 is maintained for the duct width-to-height ratio (W/H). The outcomes of this study indicate a considerable increase in the Nusselt number, ranging from 50.47% to 69.51%, concurrently with a substantial rise in the friction factor, ranging from 27.76% to 144.75%, when compared to designs using a smooth absorber surface in the context of SAHs. By utilizing the experimental data, relationships between the friction factor and the Nusselt number are established based on the artificial roughness parameters and the operating conditions. The current study’s findings significantly advance our knowledge of and ability to improve SAH systems’ heat transfer and friction characteristics. Thus, this investigation improves our understanding of these systems operational behavior in many situations.

Development of Model and Graphical User Interface for Leak Localization in Crude Oil Pipeline

Pipelines provide the most efficient and cost-effective means for fluid transport but the challenge posed by leaks has substantially increased the risks and hazards in pipeline fluid transportation. The development of efficient leak detection system pays off in quicker leak detection and localization, leading to quicker responses and remediation works by the pipeline emergency response team. This would ultimately bring about less severity of the pipeline leak in terms of financial losses, human and environmental consequences. Steady state modeling of crude oil pipeline flow with attempt to determine and localize leak has been achieved in this study. Mathematical models have been developed to detect and localize leaks in crude oil pipeline during leak occurrence. Leak detection was modeled using the conservation of mass equation while leak localization was modeled by modifying the Darcy-Weisbach pipeline liquid flow equations and utilizing the Swamee-Jain friction factor correlation. Equations for flowrate and pressure drop along the pipeline were developed for two cases: a case where there is no leak in the pipeline and a case where there is leak in the pipeline. Leak localization equation was determined by equating the fluid flow equation when there is no leak and when there is leak. The model was structured and simulated in Matlab software with the model tested for four field cases. The results from the simulation revealed swift leak detection, accurate localization of the leak, and determination of the pressure at the point of leak. Experimentally determined results from actual field measurements of leak incidences were used to validate the results. The result determined from the model developed proved accurate with only an average error of 0.216 miles.

A new mechanistic model to predict liquid loading in inclined natural gas wells

Accurately predicting the critical gas velocity and inclination angle is crucial for gas field development. However, the mechanism of liquid loading remains elusive due to insufficient attention given to the multivaluedness of flow structures and phase non-uniformity. This paper theoretically studied the flow pattern and gas-liquid configuration in wellbore based on the minimum energy principle. The Kelvin-Helmholtz instability of liquid film was analyzed, and a new correlation for the interfacial friction factor was proposed based on wave properties. The results indicated that the flow pattern transitioned from stratified to annular flow as the inclination angle increased. The gas-liquid interface presented a curved shape, with the interface curvature being influenced by various factors such as fluid properties, tube diameter, inclination angle, and gas and liquid velocities. As the inclination angle increases, the critical gas velocity first increases and then decreases, reaching a peak between 44° and 59°, aligning well with experimental and conventional results. Larger tube diameter, higher liquid density, and viscosity result in a higher critical gas velocity. Waves are more prone to develop in inclined pipes, and capillary waves can break up liquid film due to instability, leading to a discontinuous flow in inclined tubes. Film instability is exacerbated by a smaller diameter, higher liquid holdup, or greater inclination angle. Finally, a new model was devised to predict liquid loading in inclined natural gas wells, demonstrating better performance than existing models. In practice, the present model can achieve real-time prediction of critical gas velocity and continuously monitor the location of liquid accumulation in gas wells over the lifespan.

Investigations on cooling heat transfer of CO2-based mixtures in a novel airfoil fin mini-channel at supercritical pressure

Thermal-hydraulic characteristics of three supercritical CO2-based mixtures (CO2/H2S, CO2/Xe and CO2/propane) in an airfoil fin (AFF) mini-channel adopted in the printed circuit heat exchanger (PCHE) under cooling conditions are comprehensively investigated through numerical simulations. The results show that the CO2/H2S mixture, which has higher critical temperature and larger critical pressure than the pure CO2, exhibits the greatest heat transfer performance among three mixtures. This advantage is particularly pronounced at relatively large Reynolds number, with small mass fraction of the H2S and under near-critical conditions. The overall friction loss of mixtures with the additive mass fraction smaller than 0.3 is comparable to that of the pure CO2. The heat transfer coefficient of the mixtures presents fluctuations during the cooling processes, and this goes against the stable and safe operation of the PCHEs. These fluctuations could be mitigated at relatively small mass flow rate and with small mass fraction of the additive. Three widely-recognized buoyancy criteria are employed to predict the onset of the buoyancy effects in the AFF channel, and the superior heat transfer of the CO2/H2S mixture could be attributed to the fiercer buoyancy effects. Considering the buoyancy effects, modified correlations for the flow and heat transfer of pure CO2 and the CO2-based mixtures in the novel mini-channel are proposed. The maximum deviations of the modified Nusselt number and fanning friction factor correlations are ± 25 % and ± 20 %, respectively.

Comparisons of two-phase condensation and single-phase heat transfer and frictional pressure drop characteristics and energy-saving performance analysis of R-32 and R-410A in plate heat exchanger

In this study, the heat transfer and frictional pressure drop characteristics of R-32 and R-410A in a plate heat exchanger are experimentally evaluated. The study comprises two-phase condensation, single-phase vapor, and liquid cooling experiments of R-32 and R-410A, as well as an independent single-phase water heat transfer experiment. The effects of heat flux, mass flux, condensing pressure, mean vapor quality, and refrigerant Reynolds number on heat transfer and pressure drop are assessed for comparisons of R32 and R410A. The results demonstrate that the heat transfer performance and frictional pressure drop increase with rising mass flux and mean vapor quality and decrease with declining condensing pressure in the two-phase condensation experiments. Furthermore, increasing the heat flux enhances the heat transfer performance while having negligible impact on the frictional pressure drop. In the single-phase cooling experiments, both heat transfer performance and frictional pressure drop rise with increasing refrigerant flow rate. Based on the experimental results, Nusselt number and friction factor correlations for two- and single-phase flows of R-32 and R-410A are developed and compared with the correlations from other studies. Finally, energy-saving performance is evaluated and compared between the refrigerants.

Evaluation of plate heat exchangers comprising sections with different chevron angle arrangements

Gasketed Plate Heat Exchangers (GPHEs) are essential equipment for thermal control of oil facilities owing to their compactness and well-organized assembly concept. In order to satisfy heat loads of several megawatts, numerous and large plates are necessary. The application of GPHEs with plentiful plates yields flow maldistribution which affects GPHE thermal–hydraulic performance. With the purpose of matching different heat loads and processing conditions or as an alternative to reduce maldistribution effects, GPHEs with mixed arrangements, comprising sections where channels contain different geometrical features, may be selected. This works addresses the evaluation of flow and pressure distributions in GPHEs with mixed arrangements. The pressure drop in each GPHE section is initially approximated by the pressure drop in parallel pipes, neglecting the pressure drop in the ports. With this assumption, the inlet flow rate is divided into two different parts. The pressure distributions in each section are assumed to maintain flow features of m2-model for U-type arrangement. The friction factor for each GPHE segment was determined with independent experiments including only one section type and with a small number of channels as to avoid flow maldistribution. Friction factor correlations were determined for single section GPHEs where each channel can be formed with plates containing different chevron angles: 30°/30°, 60°/60°, 66°/66°, 30°/60° and 30°/66°, with channel Reynolds number ranging from 260 to 3,080. Subsequently, experiments with GPHEs containing mixed sections with high and low pressure drop channels were performed: 60°/60° and 30°/30°, 30°/30° and 66°/66°; with total number of channels up to 180. The channel pressure drop was measured in regularly spaced locations. The pressure drop in each GPHE segment has been predicted with the fractional RMS deviation equal to 2.2%. Although the mass flow rate per channel has not been measured, it is expected that the predicted flow rate distribution can reasonably stand for the real one and, therefore, assisting in proper thermal performance evaluation.

Thermohydraulic performance augmentation of triangular duct solar air heater using semi‐conical vortex generators: Numerical and experimental study

AbstractThermohydraulic performance augmentation using turbulence promotors is a commonly adopted technique in solar air heater (SAH) applications. This article presents the thermohydraulic performance augmentation of triangular duct SAH using semi‐conical vortex generators (SCVG) using computational fluid dynamics and experimental methodology for various flow Reynolds numbers ranging from 6000 to 21,000. An in‐depth parametric analysis is undertaken to establish the influence of flow attack angle, relative longitudinal pitch, relative transverse pitch and cone diameter of SCVG on the thermohydraulic performance as indicated by the thermohydraulic performance parameter (THPP). The results reveal that the SCVG generates longitudinal vortices and introduces flow impingement zones which significantly affects the flow and heat transfer characteristics of air heaters. Correlations for Nusselt number and friction factor are established, which predicts the performance outcomes with an average error of 6.74% and 4.46%, respectively. The optimal THPP is determined to be 1.74 using artificial neural network model and Bonobo Optimization algorithm. The SCVG produces THPP values well above unity for the entire flow Reynolds number range of 6000–21,000.

Experiments On Gasketed Plate Heat Exchangers with Segmented Corrugation Pattern

Abstract Gasket plate heat exchanger (GPHE) is among the most used heat exchanger types, known for its high effectiveness and compact design. Its remarkable feature is the corrugated plate geometry, typically a Chevron pattern. This work aims to analyze another corrugation pattern, which has segments with different angles to the vertical. The strengths and weaknesses of the segmented plate are still unclear, as the studies on this pattern are scarce. To fill this gap, we experimentally assess the pressure drop and heat transfer in a GPHE composed of 31 segmented plates. The plates have four quadrants, and the combination of low-angle and high-angle plates can form up to six channel types. Pressure and temperature data are acquired in 144 sets of experiments. In the pressure drop results, we observe a considerable discrepancy between the two streams, which leads to a discussion of a relevant phenomenon: the elastic deformation of the plates. If the inner pressure of the streams is not equal, the pressure gradient causes the plates to deform and change the channel geometry. The stream with the higher pressure has its channels expanded, while the lower pressure channels will be strangled. This phenomenon is rarely reported in the literature and strongly affects the pressure drop. Moreover, we present friction factor correlations for six channel types using flow data. Based on the generalized Lévêque analogy in the heat transfer experiments, we argue that the plates' deformation also affects the heat transfer.

Thermal and hydraulic performance of volumetrically heated triply periodic minimal surface heaters

Advanced heat transfer surfaces, mainly Triply Periodic Minimal Surfaces (TPMSs) have great potential to increase heat transfer performance over traditional heat transfer surfaces due to their tortuous flow path and higher surface area-volume ratio. The emergence of additive manufacturing of nuclear fuel motivates experimental investigation of such advanced geometries in the context of a nuclear reactor core. This study employed a novel method to explore the performance of gyroid and diamond TPMS geometries. Volumetrically heated heaters were additively manufactured from conductive polymer filament, and airflow was used to simulate the convective heat transfer from the core within a nuclear reactor. The mass flow and volumetric generation rates were varied, local Nusselt number correlations were obtained using embedded thermocouples to measure the solid and fluid temperature, and friction factor correlations were developed using differential pressure measurements. The gyroid TPMS presented a friction factor 1.5 times higher than the diamond TPMS and 90 times that of the rod bundle. TPMS geometries showed Nusselt numbers 8–10 times higher than that of the rod bundle, also maintaining colder internal temperatures, which suggested that they could sustain 250–275 % higher power density than the rod bundle for a given centerline temperature. Hence, having the potential to greatly increase the safety margins and power output of a nuclear reactor core with similar volume.

Development of correlations of Nusselt number and friction factor of solar thermal collector equipped with hybrid rib roughness

In this advanced and comprehensive research, a pioneering hybrid rib configuration, amalgamating arc and V-shaped ribs, is precisely engineered to delve into the complex synergistic effects between this cutting-edge rib design and the heat transfer and fluid flow behavior within a solar thermal collector (STC) specifically utilized for direct air heating. The focal point of this investigation is the impact of the rib pattern on pivotal performance indicators, notably the Nusselt number (Nu) and the friction factor (f). This specific rib roughness design emanates from an exhaustive analysis of a spectrum of non-dimensional roughness parameters: the arc angle (α), the attack angle (β), the relative positioning of the V ribs (D/w), the relative spacing of the ribs (p/e), and the rib height (e/D). These parameters are studied within defined ranges: 30̊‐60̊, 30̊‐60̊, 0.2–1, 8–12, and 0.023–0.043, respectively. The results of highlight a significant improvement in heat transport, as indicated by a significant increase in the Nusselt number (Nu), which has risen impressively by a factor of 3.08. Furthermore, this paper presents development of correlations for Nu and f, taking into account the roughness parameters of the hybrid ribs and the flow Reynolds number, in order to precisely forecast these key performance measurements.

Development of a friction factor correlation applicable to both wet and dry foam flow in circular vertical pipes

BackgroundFoam flow, distinguished by its low density and extensive specific surface area, is employed for the cleaning of plant systems. However, its dual nature as a gas-liquid mixture and a non-Newtonian fluid complicates the prediction of the frictional pressure drop. MethodsThis study constructed a laboratory-scale experimental setup to illustrate the upward flow behavior of aqueous foam in a vertical circular pipe, capturing the foam flow using a high-speed camera. Utilizing the collected data and images, a model was developed for the friction factor to predict the frictional pressure drop of the foam flow, under the assumption that the foam flow is a non-Newtonian, quasi-homogeneous, steady, and fully developed laminar flow. Significant findingsWet foam, characterized by small, uniformly distributed spherical bubbles, is observed at lower foam quality levels. In contrast, dry foam, marked by a larger mean bubble diameter, non-uniform bubble distributions, and slugs, is observed at higher foam quality levels. A notable inflection point in the frictional pressure drop is observed during the transition from wet to dry foam within a vertical pipe. The foam regime and frictional pressure drop characteristics of the foam flow show limited sensitivity to surfactant concentration within the experimental range. A correlation for friction factors, applicable to both wet and dry foam flows in vertical circular pipes, was developed based on the Reynolds number, exhibiting a prediction error of 23.6 %.

Heat transfer and friction factor correlation for rhombus-shaped roughness geometry on the absorber plate of solar air collector

Heat transfer and friction factor correlation for rhombus-shaped roughness geometry on the absorber plate of solar air collector

Numerical investigation on mixed convection for laminar molten salt in horizontal square tubes

Molten salts are the key working media in nuclear and new energy fields. However, the mixed convection of molten salt is rarely investigated. The mixed convection of laminar flow in horizontal square tubes with constant heat flux is analyzed using Fluent software for the first time. The effects of heat flux, inlet temperature and Reynolds number on the flow and heat transfer performances are evaluated. It is found that as the buoyancy force increases, the friction factor, flow entropy generation rate, Nusselt number, and exergy efficiency increase, while the heat transfer entropy generation rate and exergy loss decrease. Compared to the forced convection, the maximum local friction factor, flow entropy generation rate, mean Nusselt number and mean exergy efficiency for mixed convection increase by 25.8%, 50.5%, 109.0% and 7.6%, respectively. Moreover, the maximum mean heat transfer entropy generation rate and exergy loss decrease by 56.1% and 57.3%, respectively. In addition, approximately 42% of the friction factor predicted by Fluent and 30% of the heat transfer predicted by Fluent exceed 20.0% uncertainties of conventional correlations. Therefore, an accurate friction factor correlation with 12.9% uncertainty and an accurate heat transfer correlation with 9.1% uncertainty are proposed.

Thermal−hydraulic characteristics of R32 and R410A condensation in plate heat exchangers with 1 mm chevron depth

Compact brazed plate heat exchangers (BPHEs) with low chevron depths are widely used in new heat pumps and air-conditioners for reducing inventory and improving efficiency. This study analyses the complete condensation of R410A and R32 inside BPHEs with a chevron depth of 1 mm. The effects of the mass flux and chevron patterns (V-shaped and W-shaped) on the heat transfer coefficient (HTC) and frictional pressure drop are investigated. The HTC of R32 is 30–50 % higher than that of R410A, which has a 10–20 % higher friction factor at high mass fluxes and vice versa at low mass fluxes. The HTC of R410A monotonically increases with the mass flux, whereas that of R32 does not. The W-shaped pattern results in 30 % and 15 % higher pressure drops compared with the V-shaped pattern for R410A and R32, respectively. The friction factor of R32 decreases more sharply than that of R410A as the mass flux increases, particularly at low mass fluxes. The correlations developed by Longo et al. and Zhang et al. show the best agreement with the experimental data for the HTCs of R32 and R410A, respectively, with mean absolute percentage deviations (MAPDs) of 15 %. The friction factor correlation of Zhang et al. accurately predicts the pressure drop of R32 for the W-shaped and V-shaped patterns. In addition, it accurately predicts the pressure drop of R410A for the W-shaped pattern, with an MAPD of less than 10 %, but over-estimates it by 37 % for the V-shaped pattern.

Experimental investigation on heat transfer and friction factor characteristics for novel hybrid roughness used in solar air heater

ABSTRACT The influence of heat transfer and frictional characteristics of air that is turbulent and transitting rectangular channel textured by novel hybrid roughness (multi-V shaped ribs combined with hemispherical protrusion in V-fashion) has been studied experimentally. A uniform solar intensity of 1000 W/m2 is incident over the opposite side of the roughened plate. The relative roughness pitch, angle of attack, Reynolds number, hydraulic diameter, relative protrusion pitch, and relative gap width majorly influence the thermal and frictional characteristics of solar air heater. In this research paper, the effect of Reynolds number from 4281 to 18,250, relative protrusion pitch from 0.375 to 0.625 and relative gap width from 2 to 4 on heat transfer and friction factor on hybrid roughness geometry have been studied. The highest value of Nusselt number is 4.15 obtained at a relative protrusion pitch of 0.5, relative gap width of 2 compared to smooth duct and Reynolds number value of 18,250. By increasing the Reynolds number, the value of friction factor keeps on decreasing and highest value of friction factor of about 3.8 is obtained at a relative protrusion pitch of 0.375, Reynolds number value of 4,281 and relative gap width of 4 as compared to smooth duct. The results of the experiment shows that hybrid roughness performs thermally better than their solitary roughness geometries. Further, Nusselt number and friction factor correlations were also developed and show a very good match with the experimental results.

Multiscale Modeling of Flow in Rod Bundles: From Direct Numerical Simulation and Subchannel to Coarse-Mesh CFD

Fast and accurate evaluation of flow and heat transfer phenomena in rod bundles is a problem of long-standing interest in nuclear engineering. Computational fluid dynamics (CFD) can provide accurate but relatively time-intensive estimates, such that simulations of very long transients with high spatial detail are infeasible. On the other hand, subchannel codes require relatively low computational time and can provide pin-level estimates, but have substantial empiricism in evaluating aspects such as crossflows and turbulent mixing coefficients. A multiscale method (SC+) for bridging this accuracy/speed gap, based on the Subchannel CFD (SubChCFD) method of Liu et al. [Nucl. Eng. Design, Vol. 355, paper 110318 (2019)], is demonstrated and developed here with a focus on a 5 × 5 square rod bundle geometry. The method has been newly implemented into the commercial code STAR-CCM+ and benchmarked against Liu et al.’s data. The 5 × 5 geometry was chosen in part due to the availability of direct numerical simulation (DNS) data at a relevant Reynolds number of a similar configuration for comparison. The SC+ results are variously compared against results from DNS, large eddy simulation, wall-resolved Reynolds-averaged Navier-Stokes, and coarse-mesh CFD methods. As an expansion to the original SubChCFD approach, a simple Hi2Lo approach is demonstrated using the DNS data as a correction to the original friction factor correlations employed. This is verified to improve the predictions. Additional test cases with geometric perturbations are pursued, illustrating the flexibility of SC+. The potential of this method for modeling the narrow gap vortex instability, which would represent an advancement over standard subchannel approaches, is also assessed. The method is expanded to include transverse flow losses, which was found to improve the results for modeling the gap instability. Initial extensions of SC+ for hexagonal rod bundles are also presented; some inaccuracies for the coarsest meshes prompted a detailed investigation of the mesh convergence behavior of the method. Geometric correction factors were devised that provided substantial improvement on these very coarse meshes, improving the prospects of SC+ for wider usage. Future work plans are to expand the methodology to wire-wrapped rod bundles and to implement the method into Pronghorn, with a unified pipeline via the Cardinal wrapper between the codes NekRS, Pronghorn, and BISON, to solve fuel performance problems of direct interest to industry.

Thermo-hydraulic performance of solar air heater with built-in one-eighth sphere vortex generators

The primary objective of optimizing solar air heaters is to enhance their thermal efficiency, and the incorporation of perturbing elements into the absorber plate has proven to be an effective approach. The present study employed an electric heating plate to simulate solar heating and proposed a novel one-eighth sphere vortex generator to create strong longitudinal vortices and weak transverse vortices, thereby achieving enhanced overall performance. The experimental investigation focused on examining the impact of parameters, including deflection angle (α), relative transverse pitch (S/H), relative longitudinal pitch (L/H), relative height (e/H), and Reynolds number (Re), on both heat transfer and flow characteristics. The results show that new vortex generator performs best at deflection angles of 180°. The maximum thermo-hydraulic performance parameter of 2.03 was observed in this study. Additionally, it was found that the maximum Nusselt number (Nu) and friction factor (f) were 2.45 and 1.96 times higher than those obtained for a smooth duct, respectively. New correlations of Nusselt number (Nu) and friction factor (f) were developed to predict the heat transfer and flow resistance characteristics of solar air heater with built-in one-eighth sphere vortex generators. This study proposes a new idea to enhance the performance of solar air heaters.

New Friction Factor Correlation for Phase-Change Flow in Plate Heat Exchangers

This article reports a new two-phase friction factor correlation for condensing and evaporating flows in plate heat exchangers. Over a thousand condensation pressure drop data compiled from seventeen articles were reduced to a two-phase friction factor correlation and successfully evaluated with data not used for correlation development. Similarly, over two thousand evaporation pressure drop data were collected from twenty-four articles and were empirically modeled to yield a two-phase friction factor, which was also successfully validated with independent data. The condensation friction factor correlation fit 72% of the data within ±50% and modeled 92% of the evaluation data within ±50%. Similarly, the evaporation friction factor correlation fit 64.9% of the data within ±50 and 89.8% of the evaluation data within ±50%. Pressure drop in condensers was predominantly due to convective condensation and buoyancy forces. Inertial forces and convective boiling were mainly responsible for the pressure drop in evaporators. As the Weber number was much <1, drop condensation and nucleate boiling were insignificant. Meta-analysis strongly recommended deploying plate heat exchangers as condensers for lowering the pressure drop and was inconclusive for evaporators.

Experimentally determining the thermophysical properties, heat transfer and friction factor Fe3O4-TiO2 magnetic hybrid nanofluids in a mini-heat sink under magnetic field: Proposing new correlations

The heat transfer and friction factor for the Fe3O4-TiO2/water nanofluids circulating in a mini-heat sink of comparable magnitude to personal computer or electronic gadgets with and without a magnetic field have been estimated experimentally. The Fe3O4-TiO2 nanomaterial was prepared using chemical coprecipitation and sol–gel technique. Synthesized Fe3O4-TiO2 nanoparticles were characterized by X-ray diffraction, and vibrating sample magnetometer. The water-based hybrid nanofluids were then used in a series of experiments for assessing heat transfer, and friction factor of a mini-heat sink assembly of five circular channels with 4 mm in diameter and 50 mm in length. The experiments were performed in the operating range: 238.66 < Re < 1873.36; 0 <ϕ < 2 %; and 0 < Gauss < 1000, respectively. Constant heat flux boundary condition was maintained at the bottom surface of the heat sink and an external magnetic field was provided with an electromagnet. Results indicate that, by using the Fe3O4-TiO2 hybrid nanofluid of 2 % vol. the Nusselt number, with no magnetic field, is enhanced over that of water by 38.16 %, and by 88.93 % when the magnetic field of 1000 gauss is applied. However, the hybrid nanofluid of 2 vol% imposed a penalty in increase in friction factor of 25.87 % without magnetic field, and 67.64 % when magnetic field of 1000 G is applied at a Reynolds number of 1873.33 over water data. The experimental data were used to develop generalized Nusselt number and friction factor correlations for a mini-heat sink subjected to an external magnetic field.

Investigation on the pressure drop characteristics of ITER thermal shield cooling pipes

This paper presents the experimental results of the pressure drop through the cooling pipes of the ITER Thermal Shield (TS) panels. High pressure and room temperature nitrogen gas is selected for the experiment, which is equivalent operating condition with the 80 K helium gas from fluid mechanics point of view. Flow rate is set by a mass flow controller and pressure difference between the inlet and the outlet of the cooling pipe is measured by a differential pressure gauge. The experimental set-up is open loop type, which is connected to high pressure gas bottle. Flexible corrugated pipes are used to connect the TS cooling pipes with the measurement system line. The effect of the corrugated pipe is evaluated separately and excluded from the measurement results of the TS pipes. Test results of several TS panels are shown in this paper and are compared with the calculation using existing friction factor correlation and local loss coefficient of the pipe bends. The limitation of the calculation is discussed considering the hydrodynamic developing flow in the pipe routing.