Particle image velocimetry measurements of a thermally convective supercritical fluid

Valori, Valentina; Elsinga, Gerrit E.; Rohde, M.; Westerweel, J.; Hagen, T.H.J.J. van der

doi:10.1007/s00348-019-2789-z

Cited by 18 publications

(10 citation statements)

References 29 publications

(44 reference statements)

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“…(i) The characteristic velocity becomes asymmetric, as found in previous numerical [13,16,17] and experimental studies [25,26], and (ii) the shape of the velocity and temperature profiles inside the boundary layers changes due to temperature-dependent fluid properties.…”

Section: A Derivationmentioning

confidence: 56%

“…This is nontrivial and has so far not been done experimentally because Pr m andX are both intrinsic properties of a fluid. Previous experiments and simulations have been conducted at fixed T m with varyingX by changing and P m , thus causing also changes in Ra m and Pr m [11,14,17,19,25,26]. Manipulating the degree of the NOB effect in such a way always results also in a change of Ra m , which also changes the heat flux.…”

Section: Experimental Program and The Description Of The Setupmentioning

confidence: 99%

“…Nu m = c 3 Re (26) with the coefficients c 1 = 8.05, c 2 = 1.38, c 3 = 0.487, c 4 = 0.0252, and a = 0.922 obtained from Stevens et al [31]. These coefficients were obtained by fitting the GL model to available data from experiments in cylinders with aspect ratio = 1.…”

Section: A Derivationmentioning

confidence: 99%

“…To solve the set of Eqs. (25) and (26), one needs to evaluate the fluid properties at T c and hence one needs to know T c . This can either be done from direct measurements or from a model such as the extended boundary-layer model ( [19]).…”

Section: A Derivationmentioning

confidence: 99%

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Turbulent Rayleigh-Bénard convection under strong non-Oberbeck-Boussinesq conditions

2020

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We report on Rayleigh-Bénard convection with strongly varying fluid properties experimentally and theoretically. Using pressurized sulfur-hexafluoride (SF 6) above its critical point, we are able to make measurements at mean temperatures (T m) and pressures (P m) along Prandtl-number isolines in the (T, P) parameter space. This allows us to keep the mean Rayleigh-(Ra m) and Prandtl number (Pr m) constant while changing the temperature dependences of the fluid properties independently, e.g., probing the liquidlike or gaslike region that are left and right of the supercritical isochore. Hence, non-Oberbeck-Boussinesq (NOB) effects can be measured and analyzed cleanly. We measure the temperature at midheight (T c) as well as the global vertical heat flux. We observe a significant heat transport enhancement of up to 112% under strong NOB conditions. Furthermore, we develop a theoretical model for the global vertical heat flux based on ideas of Grossmann and Lohse (GL) in OB systems, adjusted for nonconstant fluid properties. In this model, the NOB effects influence the boundary layer and hence T c , but the change of the heat flux is predominantly due to a change of the fluid properties in the bulk, in particular the heat capacity c p and density ρ. Predictions from our model are consistent with our experimental results as well as with previous measurements carried out in pressurized ethane and cryogenic helium.

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Section: A Derivationmentioning

confidence: 56%

Section: Experimental Program and The Description Of The Setupmentioning

confidence: 99%

Section: A Derivationmentioning

confidence: 99%

Section: A Derivationmentioning

confidence: 99%

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Turbulent Rayleigh-Bénard convection under strong non-Oberbeck-Boussinesq conditions

2020

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“…To the authors' knowledge, no experimental studies about direct velocity measurements in high speed non-ideal flows were found in the literature up to date. A recent research (Valori et al 2019) applied PIV to an unconventional vapor in highly non-ideal state. However, the analyzed conditions were low temperature and high pressure, and the study dealt with natural convection, thus the flow field featured extremely low velocity.…”

Section: Introductionmentioning

confidence: 99%

Direct velocity measurements in high-temperature non-ideal vapor flows

et al. 2021

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Direct velocity measurements in a non-ideal expanding flow of a high temperature organic vapor were performed for the first time using the laser Doppler velocimetry technique. To this purpose, a novel seeding system for insemination of high-temperature vapors was specifically conceived, designed, and implemented. Comparisons with indirectly measured velocity, namely inferred from pressure and temperature measurements, are also provided. Nozzle flows of hexamethyldisiloxane (MM, C$$_6$$ 6 H$$_{18}$$ 18 OSi$$_2$$ 2 ) at temperature up to $$220\,^\circ \mathrm {C}$$ 220 ∘ C and pressure up to 10 bar were taken as representative of non-ideal compressible-fluid flows. The relative high temperature, high pressure and the need of avoiding contamination pose strong constraints on the choice of both seeding system design and tracer particle, which is solid. A liquid suspension of tracer particles in hexamethyldisiloxane is injected through an atomizing nozzle in a high-temperature settling chamber ahead of the test section. The spray droplets evaporate, while the particles are entrained in the flow to be traced. Three different test cases are presented: a subsonic compressible nozzle flow with a large uniform region at Mach number 0.7, a high velocity gradient supersonic flow at Mach number 1.4 and a near-zero velocity gradient flow at Mach number 1.7. Temperature, pressure and direct velocity measurements are performed to characterize the flow. Measured velocity is compared with both computational fluid dynamics (CFD) calculations and velocity computed from pressure and temperature measurements. In both cases, the thermodynamic model applied was a state-of-the-art Helmoltz energy equation of state. A maximum velocity deviation of 6.6% was found for both CFD simulations and computed velocity. Graphical abstract

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Introduction to Binary Mixtures at Supercritical Pressures and Coupled Heat and Mass Transfer

2022

Coupled Heat and Mass Transfer in Binary Mixtures at Supercritical Pressures

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Particle image velocimetry measurements of a thermally convective supercritical fluid

Abstract: Important note To cite this publication, please use the final published version (if applicable). Please check the document version above.

Cited by 18 publications

References 29 publications

Turbulent Rayleigh-Bénard convection under strong non-Oberbeck-Boussinesq conditions

Turbulent Rayleigh-Bénard convection under strong non-Oberbeck-Boussinesq conditions

Direct velocity measurements in high-temperature non-ideal vapor flows

Introduction to Binary Mixtures at Supercritical Pressures and Coupled Heat and Mass Transfer

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