Numerical Simulation of Subcooled Flow Boiling Heat Transfer in Helical Tubes

Abstract

This paper addresses the numerical simulation of two-phase flow heat transfer in the helically coiled tubes of an integral type pressurized water reactor steam generator under normal operation using a computational fluid dynamics code. The shell-side flow field where a single-phase fluid flows in the downward direction is also calculated in conjunction with the tube-side two-phase flow characteristics. For the calculation of tube-side two-phase flow, the inhomogeneous two-fluid model is used. Both the Rensselaer Polytechnic Institute wall boiling model and the bulk boiling model are implemented for the numerical simulations of boiling-induced two-phase flow in a vertical straight pipe and channel, and the computed results are compared with the available measured data. The conjugate heat transfer analysis method is employed to calculate the conduction in the tube wall with finite thickness and the convections in the internal and external fluids simultaneously so as to match the fluid-wall-fluid interface conditions properly. Both the internal and external turbulent flows are simulated using the standard k-ε model. From the results of the present numerical simulation, it is shown that the bulk boiling model can be applied to the simulation of two-phase flow in the helically coiled steam generator tubes. In addition, the present simulation method is considered to be physically plausible in the light of discussions on the computed results.

Modeling and design guidelines for direct steam generation solar receivers

“…The wall boiling model partitioned the heat flux between the tube wall and the fluid into three parts: liquid phase convective heat flux, quenching heat flux, and evaporation heat flux (wall boiling phenomena), predicting each heat flux by empirical and mechanistic correlations. Due to the numerical instability and large computational cost of the wall boiling model, a bulk boiling model was used instead and coupled with an Euler-Euler two-phase flow model in the modeling of a PWR nuclear steam generator [21]. The bulk boiling model agreed well with the experimental data.…”

“…When steam is used as the working fluid (CSP application) or as the reactant in high-temperature systems (STEP and SHTE applications), the understanding of the complex two-phase flow boiling process inside the absorber tubes of the direct steam generation receiver is important for identifying local hot spots, and designing and predicting receiver performance. The modeling approach for the coupled heat transfer and fluid flow problem in direct steam generation solar receivers can be inspired by the design of conventional steam generators or evaporators in coal-fired boiler power plants [19,20], pressurized water reactors (PWR) in nuclear power plants [21][22][23], and vapor-compression refrigeration system [24,25]. The development of a full 3D mechanistic model of the flow boiling process is challenging [26] due to the complex nature of the processes involved (activation of nucleation sites, bubble dynamics, and interfacial heat transfers) and the computational needs required for the solution of the direct numerical problem, which incorporates a large number of bubbles and surfaces with complex geometries [27,28].…”

A numerical study of flow characteristics in a helical pipe

“…Jo et al 16 addressed the numerical calculation of two-phase flow heat transfer in the helical steam generator pipes. Detailed analyses had been performed for flow fields in terms of volume fractions, temperatures, and heat transfer coefficients.…”

Thermo-fluid-solid Coupling Analysis for Helical Transferring Tube of SG in SMART Reactor by Using Finite Element Method

“…SMART reactor is designed by Korea, it has eight helical tube type-steam generators and four reactor coolant pumps, and pressurizer. All of these devices are located in the internal of pressure vessel [2][3].The integrated design can deduce greatly the possibility of mass crack in a primary circuit pipeline, and improve the inherent safety of the reactor. Jo [2] used ANSYS software to perform a modal analysis for the helical tube of the SMART reactor.…”

“…All of these devices are located in the internal of pressure vessel [2][3].The integrated design can deduce greatly the possibility of mass crack in a primary circuit pipeline, and improve the inherent safety of the reactor. Jo [2] used ANSYS software to perform a modal analysis for the helical tube of the SMART reactor. In their works they only simulate the distribution of velocity and temperature of fluent field in the SG under normal operation.…”