A computational study of flow mal-distribution on the thermal hydraulic performance of an intermediate heat exchanger in LMFBR
15 Apr 2014-Journal of Nuclear Science and Technology (Taylor & Francis)-Vol. 51, Iss: 6, pp 845-857
TL;DR: In this article, the flow and thermal non-uniformities occurring in the intermediate heat exchanger (IHX) of a liquid metal-cooled fast breeder reactor have been characterized through numerical simulations.
Abstract: The flow and thermal non-uniformities occurring in the intermediate heat exchanger (IHX) of a liquid metal-cooled fast breeder reactor have been characterized through numerical simulations. For modeling the primary and secondary sodium flow through the IHX, an equivalent anisotropic porous medium approach has been used. The pressure drop in the equivalent porous medium is accounted through the inclusion of additional pressure drop terms in the Navier–Stokes equations, with the help of standard correlations for cross flow or parallel flow over tubes. For secondary sodium flow, the effects of a flow distributor device with orifices and baffles at the inlet have also been included, in addition to axial flow through the tubes. The heat exchange between primary and secondary streams is incorporated in the form of a volumetric heat source or sink term, which is corrected iteratively. The resulting flow distributions are in reasonable agreement with available experimental results. The study shows that the temper...
Citations
More filters
TL;DR: In this article, a three-dimensional computational fluid dynamics (CFD)-based simulation for the intermediate heat exchanger (IHX) of a pool-type sodium-cooled fast neutron reactor has been performed, which investigates the flow-field and temperature distributions of liquid sodium on both primary and secondary sides at full power conditions.
Abstract: A three-dimensional computational fluid dynamics (CFD)-based simulation for the Intermediate Heat Exchanger (IHX) of a pool-type sodium-cooled fast neutron reactor has been performed in this paper, which investigates the flow-field and temperature distributions of liquid sodium on both primary and secondary sides at full power conditions. Typically, some simplifications are applied to reduce the difficulty of computation and render the problem more tractable. A proposed method is that treat a number of tubes as porous media that replicates the pressure loss and heat transfer characteristics of the detailed model. The heat exchanger model of the ANSYS FLUENT code is used to analyze the heat transfer phenomena inside of the IHX and the resistance coefficients of porous media have been predicted by empirical relationships which vary with height and flow directions. Two separate models, with different size of inlet and outlet area for shell-side sodium, have been developed in this paper. By comparing the results from the different simulations, the model with larger inlet area for primary and non-uniform inlet velocity distribution of secondary sodium satisfies the design requirements with respect to the permissible upper limit of temperature difference and local radial velocity.
29 citations
TL;DR: In this paper, the authors investigated the influence of tube specification on the performance of a 6-m long, 290-MW IHX and found that the tube specification mainly affects the flow uniformity in the inlet region but has little effects on outlet region flow distribution.
Abstract: The intermediate heat exchanger (IHX) is a type of shell-and-tube heat exchanger. It is assembled with thousands of straight or expansion bend tubes in concentric circles and extremely huge and complex in geometry which leads to the non-uniform flow in the shell-side. The motivation of this work is to design a 6 m long, 290 MW IHX and clarify the influence of the tube specification on its performance. Traditional thermal design method is employed here for the design process, while 2-D porous medium model with anisotropic properties is adopted for simulation to support the design process adjusting the tube specification. The results show that the tube specification mainly affects the flow uniformity in the inlet region but has little effects on outlet region flow distribution. Comparing the IHX thermal-hydraulic performance under different tube specifications, it is found that the specification with 19 mm outer diameter, 25 mm radial pitch and 0.8 mm wall thickness is the best choice.
3 citations
TL;DR: In this article, both of the 3D detail simulation method and the distributed parameter method are employed to study the thermal hydraulic characteristics and figure out the influence of the coaxial bends on its performance.
Abstract: The intermediate heat exchanger (IHX), which consists of thousands of tubes assembled along concentric circles, has a complex geometry that makes it extremely difficult to analyze through the 3-D CFD approach, especially when there exists coaxial expansion bends. The motivation of this work is to study its thermal hydraulic characteristics and figure out the influence of the coaxial bends on its performance. In addition, both of the 3-D detail simulation method and the distributed parameter method are employed in this research. And the respective results by these two methods show that the shell-side main flow direction is generally consistent with the tube direction and the rear straight tube section is the main working section with the heat transfer rate of nearly 45% of the total heat transfer rate, and that the bending section plays an important role in controlling the non-uniformity of temperature field.
References
More filters
TL;DR: In this article, a generalised non-Darcian porous medium model for natural convective flow has been developed taking into account linear and non-linear matrix drag components as well as the inertial and viscous forces within the fluid.
Abstract: A generalised non-Darcian porous medium model for natural convective flow has been developed taking into account linear and non-linear matrix drag components as well as the inertial and viscous forces within the fluid. The results of the general model have been validated with the help of experimental data and compared with the various non-Darcy porous media model predictions reported in literature. It has been observed that the wall Nusselt number is significantly affected by the combination of dimensionless parameters such as Rayleigh number, Darcy number and porosity in the non-Darcy flow regime. A detailed parametric study has been presented for natural convective flow inside a rectangular enclosure filled with saturated porous medium of constant or variable porosity. It is observed that the thickness of the porous layer and the nature of variation in porosity significantly affect the natural convective flow pattern as well as the heat transfer features. The present model is also able to predict the channeling effect and associated heat transfer in forced flow through packed beds.
498 citations
"A computational study of flow mal-d..." refers background in this paper
...[8] have shown the occurrence of flow channeling in a variable porosity medium, which is similar to the short circuiting of flow in the shell side of IHX in the present problem....
[...]
TL;DR: In this article, a non-thermal equilibrium, two-equation model is used to represent the fluid and solid energy transport in a forced convection flow through a channel filled with a porous medium.
Abstract: Forced convection flow through a channel filled with a porous medium is investigated analytically. A non-thermal equilibrium, two-equation model is utilized to represent the fluid and solid energy transport. The Darcy–Forchheimer–Brinkman model is used to represent the fluid transport within the porous medium. Analytical solutions are obtained for both fluid and solid temperature fields incorporating the effects of various pertinent parameters such as the Biot number, the thermal conductivity ratio, the Darcy number and the inertial parameter. The present analytical solution for the two-equation model is validated against the exact solution for the one-equation model available in the literature as well as the analytical solution for the non-thermal equilibrium case based on a Darcian flow field. Error maps for the validity of one-equation model are established for various physical conditions taking into account the Darcy and inertial parameters as well as the Biot and the thermal conductivity ratio of fluid to solid phases. It is shown that the Darcy number and the inertial parameter have a lesser influence in establishing the validity of the local thermal equilibrium assumption.
98 citations
"A computational study of flow mal-d..." refers background in this paper
...The equivalent flow resistance for the array of tubes has been prescribed appropriately for the cross flow and parallel flow external to the tubes as well as the flow inside the tubes, from the correlations available in the literature [2,3,9]....
[...]
TL;DR: A theoretical model for heat transfer and fluid flow during alloy solidification is presented in this paper, where a detailed accounting has been made for the property variations in the dendritic phase-change region.
Abstract: A theoretical model for heat transfer and fluid flow during alloy solidification is presented. A detailed accounting has been made for the property variations in the dendritic phase-change region. A generalized porous medium approach has been adopted, with the variation of permeability being anisotropic. The effects of anisotropy are observed to be significant if the extent of the mushy zone is large or if the Rayleigh number is high.
49 citations
TL;DR: In this article, a study of flow mal-distribution in U-type micro-channel configuration is presented, where numerical simulations indicate that flow deceleration and associated pressure recovery in the inlet header lead to flow separation and recirculation which cause oscillations in channel-wise mass flow distribution.
Abstract: A study of flow mal-distribution in U-type micro-channel configuration is presented. Numerical simulations indicate that flow deceleration and associated pressure recovery in the inlet header lead to flow separation and recirculation which cause oscillations in channel-wise mass flow distribution. Increase in flow resistance by decrease in channel depth, width or number of channels or increase in channel length, results in a more uniform distribution. Mal-distribution increases at high flow rate or low viscosity due to the dominance of inertial phenomena. Experiments performed on a 25-channel setup illustrate that small manufacturing variations in channel dimensions introduce random fluctuations in flow distribution.
46 citations
"A computational study of flow mal-d..." refers background in this paper
...[12], in the context of micro-channel heat sinks....
[...]
45 citations
"A computational study of flow mal-d..." refers methods or result in this paper
...The predicted results in this range agree excellently with the experimental results of Prasad andKulacki [15], as shown in Figure 12....
[...]
...The natural convective flow and heat transfer in a differentially heated cylindrical annulus has been experimentally studied by Prasad and Kulacki [15]....
[...]
...The Rayleigh number Ra is based on the annular gap as the length scale, involving the permeability of the porous medium and the temperature difference between the hot and cold walls, similar to the work of Prasad and Kulacki [15]....
[...]