Turbulent convective heat transfer of CO 2 in a helical tube at near-critical pressure

Xu, Jinliang; Yang, Chuanyong; Zhang, Wei; Sun, Defeng

doi:10.1016/j.ijheatmasstransfer.2014.09.066

Cited by 92 publications

(18 citation statements)

References 17 publications

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“…As mentioned above, the difference of heat transfer feature between the horizontal tube and vertical upward tube is remarkable, especially in the DHT mode. Some previous studies [41,46,47] pointed out that acceleration and buoyancy effect are significantly important for HTD, turbulent convective heat transfer changes with above effects. In order to obtain these effects on heat transfer of supercritical pressure fluids, a few common dimensionless numbers have been introduced, such as Bo+ number (Eq.…”

Section: Analysis Of Heat Transfer Mechanism Between Horizontal and Vmentioning

confidence: 98%

Experimental study on the difference of heat transfer characteristics between vertical and horizontal flows of supercritical pressure water

Lei

Zhang

et al. 2017

Applied Thermal Engineering

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The present paper is devoted to investigating the difference of heat transfer characteristics between horizontal and vertical upward flows of supercritical pressure water. Experimental study is conducted with both horizontal and vertical upward tubes (32 mm3 mm), covering a range of mass fluxes (G) from 200 to 600 kg·m -2 ·s -1 , heat fluxes (q) up to 400 kW·m -2 , and pressure (P) from 23 to 28 MPa.Heat transfer characteristics are analyzed in detail for selected parameters. The results show at low q/G, an apparent heat transfer enhancement and insignificant difference in the two arrangements. However, when the q/G increases to a higher value (i.e. q/G>0.5), heat transfer deterioration occurs and a noticeable heat transfer discrepancy is detected, where the inner-wall temperature of vertical flow far exceeds that of horizontal flow. Dimensionless parameters, Bo + , K, and BTH are adopted to analyze the effects of buoyancy force and thermal acceleration for both flows. The analysis suggests that mechanisms governing horizontal and vertical flows of supercritical © 2016. This manuscript version is made available under the Elsevier user license http://www.elsevier.com/open-access/userlicense/1.0/ pressure water are different at high q/G or in deteriorated heat transfer mode. For the vertical flow, thermal acceleration play a leading role, while for the horizontal flow, the effect of buoyancy plays a larger effect than that for vertical flow.  dynamic viscosity, Pa s λ Thermal conductivity, W/K/m  density, kg/m 3 Non-dimensional Numbers Bo Bo number BTH Combined effect of buoyancy and thermal acceleration Gr Grashoft number J Acceleration effect Kv Flow-acceleration parameter Pr Prandtl number; ( ) Re Reynolds number; ( )

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Section: Analysis Of Heat Transfer Mechanism Between Horizontal and Vmentioning

confidence: 98%

Experimental study on the difference of heat transfer characteristics between vertical and horizontal flows of supercritical pressure water

Lei

Zhang

et al. 2017

Applied Thermal Engineering

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“…J. et.al. [12]. The material used for the helical coiled tube is stainless steel as this material is used by previous researchers in their experimental studies.…”

Section: Computational Domain and Boundary Conditionsmentioning

confidence: 99%

Investigation on Flow and Heat Transfer of Supercritical CO2 in Helical Coiled Tubes at Various Supercritical Pressures

et al. 2018

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Supercritical carbon dioxide (scCO2) has unique thermal properties with better flow and heat transfer behavior. However, the flow and heat transfer behavior of scCO2 using helical coil geometries have not fully documented yet. Therefore, the main purpose of this study is to investigate the flow and heat transfer characteristics of scCO2 in helical coiled tubes for heating process using computational fluid dynamics (CFD) method. For the simulation, commercial CFD software called ANSYS FLUENT is used. Helical coiled tube of inner and outer diameter 9.0 mm and 12.0 mm, respectively, with total length of 5500 mm, pitch distance of 32.0 mm and 6 turns of coils is considered. The model is intended to analyze the pressure drops, friction factor, Nusselt number, and goodness factor of scCO2. Three different inlet pressures (8.00 MPa, 9.03 MPa and 10.05 MPa) with three different uniform heat fluxes (20.5 kW/m2, 50.5 kW/m2 and 80.5 kW/m2) at constant inlet temperature of 27°C are considered. The numerical results are compared with experiment results from previous study to validate the developed model. The wall temperature results from the numerical analysis are in good agreement with the experimental data. From the numerical analysis, the Nusselt number increased significantly when the inlet mass flow rate and heat flux increased. Moreover, it was observed from the simulation results that an increment of average pressure drop by 900 Pa (19.57%) and average friction factor coefficient by 0.1536 (33.85%) when the pressure inlet increased from 9.03 MPa to 10.05 MPa. Hence, the results obtained from this study can provide information for further investigation of scCO2 for industrial applications

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“…Bae and Kim [5,6] conducted extensive experiments on heat transfer of vertically upward flowing CO2 under supercritical pressure in tubes (internal diameters (ID) of 4.4 mm and 9.0 mm), and proposed a new correlation for heat transfer by CO2. Xu et al [7,8] experimentally analyzed the turbulent convective heat transfer of CO2 flowing in a helical pipe at near-critical pressure with a constant heat flux boundary condition, and discussed the effect of inclination angles on the heat transfer of supercritical CO2 in a 0.5 mm diameter tube. Bae et al [9,10] investigated the turbulent heat transfer of CO2 at supercritical pressure flowing in heated vertical tubes using direct numerical simulation (DNS) at the inlet Reynolds numbers of 5400 and 8900.…”

Section: Introductionmentioning

confidence: 99%

Experimental and Numerical Investigation of Convective Heat Transfer of Supercritical Carbon Dioxide at Low Mass Fluxes

Lei

Zhang

et al. 2017

Applied Sciences

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Featured Application: Supercritical carbon dioxide Brayton cycle, geothermal system, nuclear reactor.Abstract: Significant differences in the heat transfer behaviors of supercritical carbon dioxide in a heated channel have been observed at different mass fluxes. At low mass fluxes, a unique heat transfer characteristic is accompanied by a monotonously smooth temperature variation without any temperature peak, even though the ratio of heat flux to mass flux (q/G) is high. In this study, experimental and numerical investigations explore the hidden mechanism of the peculiar heat transfer characteristics of supercritical carbon dioxide at low mass fluxes in vertically upward tubes with inside diameters (ID) of 5 mm. The range of operating conditions examined within the study include a mass flux (G) between 0-200 kg/m 2 s, and a heat flux (q) of up to 120 kW/m 2 . The parametric effects within these experimental conditions were analyzed on the basis of the obtained heat transfer data. Furthermore, a qualitative modeling force analysis and quantitative numerical simulation of vertical flow at low mass flux reveal the heat transfer mechanism for these temperature profiles. In addition, the distribution of flow parameters and thermo-physical properties (such as shear stress, density, and specific heat) in the near-wall region were also studied. It is found that the heat transfer behavior of supercritical CO 2 at low mass flux is similar to "film boiling" at subcritical pressure, where "vapor-like" fluid occupies the sublayer region. Due to reduced buoyancy, the fluid does not cause enough mixing/instability to bring it to the bulk flow.

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Turbulent convective heat transfer of CO 2 in a helical tube at near-critical pressure

Cited by 92 publications

References 17 publications

Experimental study on the difference of heat transfer characteristics between vertical and horizontal flows of supercritical pressure water

Experimental study on the difference of heat transfer characteristics between vertical and horizontal flows of supercritical pressure water

Investigation on Flow and Heat Transfer of Supercritical CO2 in Helical Coiled Tubes at Various Supercritical Pressures

Experimental and Numerical Investigation of Convective Heat Transfer of Supercritical Carbon Dioxide at Low Mass Fluxes

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