The Experts below are selected from a list of 5520 Experts worldwide ranked by ideXlab platform
Qihong Zhang - One of the best experts on this subject based on the ideXlab platform.
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computational fluid dynamic techniques for validating geothermal Separator sizing
2009Co-Authors: Alan R Pointon, Tracy D Mills, Gregory J Seil, Qihong ZhangAbstract:Geothermal turbine unit Sizes of 100 MW or more are increasingly common because they offer economies of scale that result in lower installed cost. Concurrently, SKM’s designs for fluid collection and separation systems for large power plant have progressively moved to more centralised Separator stations located relatively close to the power plant. Consequently, clients have been expecting individual Separators to handle increasing large fluid flows. While SKM achieves exceptionally good steam dryness and purity from its Separators using empirical formulae to progressively improve base designs over several decades, such methods have limitations with the larger unit Sizes now being routinely specified. To address this, SKM has employed Computational Fluid Dynamic (CFD) analysis techniques to model the separation process and validate the sizing for very large Separators and a wide range of fluid conditions, including multiple stages of flash. Increasing Separator Size also increases the modes of vibration within the vessels. The CFD modelling outputs have therefore been applied to a Finite Element Analysis model to validate the mechanical design and check for potential vibration problems. The benefit for plant owners/operators is the realisation of economies of scale and avoidance of resonant vibrations while maintaining high steam purity that enables extended periods between routine maintenance of their large single unit turbines.
Alan R Pointon - One of the best experts on this subject based on the ideXlab platform.
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computational fluid dynamic techniques for validating geothermal Separator sizing
2009Co-Authors: Alan R Pointon, Tracy D Mills, Gregory J Seil, Qihong ZhangAbstract:Geothermal turbine unit Sizes of 100 MW or more are increasingly common because they offer economies of scale that result in lower installed cost. Concurrently, SKM’s designs for fluid collection and separation systems for large power plant have progressively moved to more centralised Separator stations located relatively close to the power plant. Consequently, clients have been expecting individual Separators to handle increasing large fluid flows. While SKM achieves exceptionally good steam dryness and purity from its Separators using empirical formulae to progressively improve base designs over several decades, such methods have limitations with the larger unit Sizes now being routinely specified. To address this, SKM has employed Computational Fluid Dynamic (CFD) analysis techniques to model the separation process and validate the sizing for very large Separators and a wide range of fluid conditions, including multiple stages of flash. Increasing Separator Size also increases the modes of vibration within the vessels. The CFD modelling outputs have therefore been applied to a Finite Element Analysis model to validate the mechanical design and check for potential vibration problems. The benefit for plant owners/operators is the realisation of economies of scale and avoidance of resonant vibrations while maintaining high steam purity that enables extended periods between routine maintenance of their large single unit turbines.
Tracy D Mills - One of the best experts on this subject based on the ideXlab platform.
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computational fluid dynamic techniques for validating geothermal Separator sizing
2009Co-Authors: Alan R Pointon, Tracy D Mills, Gregory J Seil, Qihong ZhangAbstract:Geothermal turbine unit Sizes of 100 MW or more are increasingly common because they offer economies of scale that result in lower installed cost. Concurrently, SKM’s designs for fluid collection and separation systems for large power plant have progressively moved to more centralised Separator stations located relatively close to the power plant. Consequently, clients have been expecting individual Separators to handle increasing large fluid flows. While SKM achieves exceptionally good steam dryness and purity from its Separators using empirical formulae to progressively improve base designs over several decades, such methods have limitations with the larger unit Sizes now being routinely specified. To address this, SKM has employed Computational Fluid Dynamic (CFD) analysis techniques to model the separation process and validate the sizing for very large Separators and a wide range of fluid conditions, including multiple stages of flash. Increasing Separator Size also increases the modes of vibration within the vessels. The CFD modelling outputs have therefore been applied to a Finite Element Analysis model to validate the mechanical design and check for potential vibration problems. The benefit for plant owners/operators is the realisation of economies of scale and avoidance of resonant vibrations while maintaining high steam purity that enables extended periods between routine maintenance of their large single unit turbines.
Gregory J Seil - One of the best experts on this subject based on the ideXlab platform.
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computational fluid dynamic techniques for validating geothermal Separator sizing
2009Co-Authors: Alan R Pointon, Tracy D Mills, Gregory J Seil, Qihong ZhangAbstract:Geothermal turbine unit Sizes of 100 MW or more are increasingly common because they offer economies of scale that result in lower installed cost. Concurrently, SKM’s designs for fluid collection and separation systems for large power plant have progressively moved to more centralised Separator stations located relatively close to the power plant. Consequently, clients have been expecting individual Separators to handle increasing large fluid flows. While SKM achieves exceptionally good steam dryness and purity from its Separators using empirical formulae to progressively improve base designs over several decades, such methods have limitations with the larger unit Sizes now being routinely specified. To address this, SKM has employed Computational Fluid Dynamic (CFD) analysis techniques to model the separation process and validate the sizing for very large Separators and a wide range of fluid conditions, including multiple stages of flash. Increasing Separator Size also increases the modes of vibration within the vessels. The CFD modelling outputs have therefore been applied to a Finite Element Analysis model to validate the mechanical design and check for potential vibration problems. The benefit for plant owners/operators is the realisation of economies of scale and avoidance of resonant vibrations while maintaining high steam purity that enables extended periods between routine maintenance of their large single unit turbines.
John H Reif - One of the best experts on this subject based on the ideXlab platform.
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efficient parallel computation of the characteristic polynomial of a sparse separable matrix
Algorithmica, 2001Co-Authors: John H ReifAbstract:{This paper is concerned with the problem of computing the characteristic polynomial of a matrix. In a large number of applications, the matrices are symmetric and sparse : with O(n) non-zero entries. The problem has an efficient sequential solution in this case, requiring O(n 2 ) work by use of the sparse Lanczos method. A major remaining open question is: to find a polylog time parallel algorithm with matching work bounds. Unfortunately, the sparse Lanczos method cannot be parallelized to faster than time Ω (n) using n processors. Let M(n) be the processor bound to multiply two n \times n matrices in O(log n) parallel time. Giesbrecht [G2] gave the best previous polylog time parallel algorithms for the characteristic polynomial of a dense matrix with O (M(n)) processors. There is no known improvement to this processor bound in the case where the matrix is sparse. Often, in addition to being symmetric and sparse, the matrix has a sparsity graph (which has edges between indices of the matrix with non-zero entries) that has small Separators. This paper gives a new algorithm for computing the characteristic polynomial of a sparse symmetric matrix, assuming that the sparsity graph is s(n) -separable and has a Separator of Size s(n)=O(n γ ) , for some γ , 0 < γ < 1 , that when deleted results in connected components of ≤α n vertices, for some 0 < α < 1 , with the same property. We derive an interesting algebraic version of Nested Dissection, which constructs a sparse factorization of the matrix A-λ I n where A is the input matrix and I n is the n \times n identity matrix. While Nested Dissection is commonly used to minimize the fill-in in the solution of sparse linear systems, our innovation is to use the Separator structure to bound also the work for manipulation of rational functions in the recursively factored matrices. The matrix elements are assumed to be over an arbitrary field. We compute the characteristic polynomial of a sparse symmetric matrix in polylog time using P(n)(n+M(s(n)))≤ P(n)(n+ s(n) 2.376 ) processors, where P(n) is the processor bound to multiply two degree n polynomials in O(log n) parallel time using a PRAM (P(n) = O(n) if the field supports an FFT of Size n but is otherwise O(nlog log n) [CK]. Our method requires only that a matrix be symmetric and non-singular (it need not be positive definite as usual for Nested Dissection techniques). For the frequently occurring case where the matrix has small Separator Size, our polylog parallel algorithm has work bounds competitive with the best known sequential algorithms (i.e., the Ω(n 2 ) work of sparse Lanczos methods), for example, when the sparsity graph is a planar graph, s(n) ≤ O( \sqrt n ) , and we require polylog time with only P(n)n 1.188 processors.
