Gonzalez, I.; Naseri, A.; Rigola, J.; Perez, C.; Oliva, A. International Conference on Compressors and their Systems p. 012032-1-012032-10 DOI: 10.1088/1757-899X/232/1/012032 Data de presentació: 2017-09-11 Presentació treball a congrés
Suction and discharge processes with self actuated valves have a major influence in efficiency and reliability of hermetic reciprocating compressors. Understanding the operation completely in order to enhance compressor's design needs precise prediction of the fluid-structure interaction complexities involved in these processes. This paper presents a comprehensive description of a numerical methodology to account for the coupled behaviour of a reed valve and a turbulent flow. The method is based on a partitioned semi-implicit scheme that only strongly couples the fluid pressure term to the structural solver. A three-dimensional CFD analysis with LES turbulence modelling is used for the flow while a combination of plate theory and mode summation method is used for the solid. The dynamically changing domains are tackled by means of lagrangian and arbitrary lagrangian-eulerian approaches for the solid and the fluid, respectively. The whole model is compared with experimental data at Reynolds number 10, 000, showing good agreement in lift amplitude and deformation fluctuations. Finally, as an illustrative case, results regarding lift, pressures, force and effective areas are compared with those of a valve with wider gland.
A packed-bed thermocline tank represents a proved cheaper thermal energy storage for concentrated solar power plants compared with the commonly-built two-tank system. However, its implementation has been stopped mainly due to the vessel’s thermal ratcheting concern, which would compromise its structural integrity. In order to have a better understanding of the commercial viability of thermocline approach, regarding energetic effectiveness and structural reliability, a new numerical simulation platform has been developed. The model dynamically solves and couples all the significant components of the subsystem, being able to evaluate its thermal and mechanical response over plant normal operation. The filler material is considered as a cohesionless bulk solid with thermal expansion. For the stresses on the tank wall the general thermoelastic theory is used. First, the numerical model is validated with the Solar One thermocline case, and then a parametric analysis is carried out by settling this storage technology in two real plants with a temperature rise of 100 °C and 275 °C. The numerical results show a better storage performance together with the lowest temperature difference, but both options achieve suitable structural factors of safety with a proper design.
This paper presents a complete numerical procedure to study the fluid-structure interaction problem of incompressible flow through reed valves, typically employed in hermetic reciprocating compressors. A partitioned semi-implicit coupling scheme is implemented, which only strongly couples the added-mass-effect (pressure term) of the fluid to the structure hence, assuring numerical stability and avoiding excessive computational cost. The fluid is solved by a three-dimensional CFD solver using large eddy simulation closures to model the turbulent flow, while the reed valve is described with the classical plate theory and the normal mode summation method. To showcase the potentiality of the proposed methodology, a sensitivity analysis regarding valve thickness is carried out for a given velocity in the feeding channel. Considerable differences, mainly in valve lift and pressure drop, are appreciated between the considered configurations.
This paper represents numerical simulation of fluid-structure interaction (FSI) system involving an
incompressible viscous fluid and a lightweight elastic structure. We follow a semi-implicit approach in which we
implicitly couple the added-mass term (pressure stress) of the fluid to the structure, while other terms are coupled
explicitly. This significantly reduces the computational cost of the simulations while showing adequate stability.
Several coupling schemes are tested including fixed-point method with different static and dynamic relaxation,
as well as Newton-Krylov method with approximated Jacobian. Numerical tests are conducted in the context of a
biomechanical problem. Results indicate that the Newton-Krylov solver outperforms fixed point ones while introducing
more complexity to the problem due to the evaluation of the Jacobian. Fixed-point solver with Aitken's relaxation
method also proved to be a simple, yet efficient method for FSI simulations.
This article is published under a CC BY licence. The Version of Record is available online at: http://dx.doi.org/10.1088/1742-6596/745/3/032020.
Thermocline storage system is considered as a cheaper alternative to the common two-tank molten salt approach. However, its configuration and performance might lead to a catastrophic structural failure known as thermal ratcheting. It may occur when a tank filled with particulate solids is cyclically heated and cooled. This paper aims at studying the transient evolution of thermocline tank wall stresses, taking into account both thermal and mechanical loads. A complete numerical methodology to deal with the fluid-structure interaction problem, based on a thermoelastic model for the shell, is used. For validation purposes and getting better understanding of the stress-strain response of the structure, Solar One Pilot Plant thermocline case is reproduced. Although some experimental data obtained from the literature suffers of large uncertainty, the numerical results show consistent good agreement.
Guadamud, E.; Oliva, A.; Lehmkuhl, O.; Rodriguez, I.; Gonzalez, I. Solar Power and Chemical Energy Systems p. 405-414 DOI: 10.1016/j.egypro.2015.03.047 Data de presentació: 2014-09 Presentació treball a congrés
This paper presents an advanced methodology for the detailed modeling of the heat transfer and dynamics phenomena in Linear Fresnel receivers. The present work aims at modeling Linear Fresnel receiver by proposing a parallel modular object-oriented methodology which considers the different elements of the receiver (e.g. Insulation material, glass cover, tube, pipe, etc.). The global model is composed of 4 sub models (heat conduction, two/single-phase flow, thermal radiation and natural convection) which are described. Results of the numerical model obtained so far are also presented and discussed.