Multiscale thermo-hydraulic modeling of cryogenic heat exchangers
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The cryogenic industry has experienced a continuous growth in the last decades, partially sustained by the worldwide development of Liquefaction of Natural Gas (LNG) projects. LNG technology provides an economically feasible way of transporting natural gas over long distances, and currently accounts for nearly 30% of the international trade of this resource. The economic feasibility of these projects, in terms of both capital and operating costs, is to a large extent controlled by the performance of the main cryogenic two-phase flow heat exchanger. This industrial scenario provides then the motivation for a detailed study of the heat exchanger from a design perspective. On the one hand, it is widely accepted that a highly detailed analysis is required at a micro scale to properly take account of the two phase heat transfer process. On the other hand, a process-level description corresponds to larger time and space scales. In general, determining the proper methodology for considering these scales and their interaction remains a challenging problem. For this reason, current techniques focus in only one particular scale. The main objective of this project is then to develop a multiscale model applicable for two-phase flow heat exchangers. In this context, a three-scale framework is postulated. This thesis was divided into macro, meso (medium) and micro scale analysis. First, a macroscopic analysis provides a broad description in terms of overall heat transfer and pressure drop, using simple models without taking into account the details of physical phenomena at lower scales. Second, at mesoscale level, flow in parallel channels is considered following a homogenization approach, thus including the effects of flow maldistribution and partial mixing. Third, the microscopic description conceives a phenomenological representation of boiling flows, following multifluid formulations, for two specific flow patterns: annular-mist and post-dryout regimes. Finally, a multiscale design algorithm is proposed.
Består avPacio, Julio Cesar; Dorao, Carlos Alberto. Application of high order methods for the simulation of heat exchanger models. Proceedings of the Fifth national conference on Computational Mechanics: 341-351, 2009.
Pacio, Julio Cesar; Dorao, Carlos Alberto; Fernandino, Maria. Sensitivity Analysis of Heat Exchangers Using Perturbative Methods. Spectral and High Order Methods for Partial Differential Equations: 275-282, 2011. 10.1007/978-3-642-15337-2_25.
Pacio, Julio Cesar; Dorao, Carlos Alberto. Numerical analysis of the effect of two phase flow maldistribution on heat transfer performance. In Transactions of the American Nuclear Society: Vol. 102-599 - 600, 2010.
Pacio, Julio C.; Dorao, Carlos A.. A study of the effect of flow maldistribution on heat transfer performance in evaporators. Nuclear Engineering and Design. (ISSN 0029-5493). 240(11): 3868-3877, 2010. 10.1016/j.nucengdes.2010.09.004.
Pacio, Julio Cesar; Dorao, Carlos Alberto. A homogenization approach for studying two phase heat exchanger performance. In Proceedings of the 8 th International Topical Meeting on Nuclear Thermal-Hydraulics, Operation and Safety: Paper ID:-N8P0131., 2010.
Pacio, J.C.; Dorao, C.A.. A comparative analysis of computational models for solving one-dimensional heat exchangers problems. .
Pacio, Julio Cesar; Dorao, Carlos Alberto. A review on heat exchanger thermal hydraulic models for cryogenic applications. Cryogenics (Guildford). (ISSN 0011-2275). 51(7): 366-379, 2011. 10.1016/j.cryogenics.2011.04.005.
Pacio, Julio Cesar; Dorao, Carlos Alberto. Modeling two phase heat exchanger in the annular mist flow regime considering entrainment and deposition phenomena. In Proceedings of ASME-JSME-KSME Joint Fluids Engineering Conference 2011, 2011.
Pacio, Julio Cesar; Dorao, Carlos Alberto. Design considerations for the sizing of high-effectiveness two-phase flow heat exchangers. In Proceedings of the 23 rd IIR International Congress of Refrigeration, 2011.