Comparison of two different ways of using inertance tube in a pulse tube cooler

It is well known that the pressure wave should lead the volume flow rate at the ambient end of the pulse tube for a high-efficiency operation of a pulse tube cooler. Inertance tube can provide such a phase relationship without DC flow problem. However, inertance tube is always connected with a reservoir in previous literatures. Through theoretical calculation here, inertance tube without a reservoir can also provide a rather large phase-leading effect. Thus phasor diagram is used to analyze the relationship between phase-leading requirement and the pulse tube geometry. Roughly speaking, a larger void volume of pulse tube would require a larger phase-leading effect. Comparison experiments are also done on a thermoacoustically-driven pulse tube cooler. With i.d.2 mm tube as inertance tube, the tube without reservoir yields close results in terms of lowest temperature to that of the tube with reservoir and both give much better performance than that of an orifice with reservoir. Finally, the advantages of using inertance tube without reservoir are given.     

ON THE COMPUTATION OF MULTIPHASE EQUILIBRIA

The main purpose of this paper is to present a new mathematical programming formulation of the multiphase equilibrium problem along with a Newton-type algorithm for its solution. The approach pursued relies on the Gibbs free energy function and geometric programming duality. The problem arised in connection with a real-life problem in oil reservoir engineering. The presentation of the model is based on a detailed mathematical analysis of the multiphase equilibrium problem. The computational results reported are obtained using data systems from oil reservoir engineering.     

某引水工程取水口围堰和预留岩坎拆除爆破

某引水工程取水口前端预留岩坎与已建水库相连,距离取水口塔体和已建大坝较近,为确保周边建筑物安全,拆除时先进行预留岩坎迎水坡爆破剥离,减少其厚度,再对混凝土围堰和剩余预留岩坎进行分层分区拆除爆破。爆破施工中采取了有效的安全爆破控制技术措施,降低了施工难度,保证了施工质量,达到了预期的效果。通过分层分区拆除爆破,有效解决了围堰和预留岩坎在大型水库水下淹没深度较深且不需人为降低水库水位进行拆除爆破的难题,为今后类似工程积累了宝贵的经验。     

Optimal reservoir flood operation using a decomposition-based multi-objective evolutionary algorithm

Reservoir flood control operation (RFCO) is a challenging optimization problem with interdependent decision variables and multiple conflicting criteria. By considering safety both upstream and downstream of the dam, a multi-objective optimization model is built for RFCO. To solve this problem, a multi-objective optimizer, the multi-objective evolutionary algorithm based on decomposition–differential evolution (MOEA/D-DE), is developed by introducing a differential evolution-inspired recombination into the algorithmic framework of the decomposition-based multi-objective optimization algorithm, which has been proven to be effective for solving complex multi-objective optimization problems. Experimental results on four typical floods at the Ankang reservoir illustrated that the suggested algorithm outperforms or performs as well as the comparison algorithms. It can significantly reduce the flood peak and also guarantee the dam’s safety.     

某工厂乙醇蒸馏设备的热回收系统应用的节能特性分析

传统的乙醇生产工艺存在设备投资大、能耗高等问题,因而发展受到制约。减少燃料消耗,提高能源的利用率,促进经济社会可持续发展。文中提出利用第二类溴化锂吸收式热泵先进的节能技术与工厂乙醇工艺需要相结合,回收利用中温热源,制取生产需求的高温热源,从而达到节能减排的要求。     

Dynamic analysis of dam–reservoir-foundation interaction in time domain

In this paper, a time domain dynamic analysis of the dam–reservoir-foundation interaction problem is developed by coupling the dual reciprocity boundary element method (DRBEM) for the infinite reservoir and foundation domain and the finite element method for the finite dam domain. An efficient coupling procedure is formulated by using the substructuring method. Sharans boundary condition at the far end of the infinite fluid domain is implemented. To verify the proposed scheme, numerical examples are carried out and compared with available exact solutions and finite–finite element coupling results for the problem of the dam–reservoir interaction. Finally, a complete dam–reservoir-foundation interaction problem is solved and its solution is compared with previously published results.The author is thankful to the anonymous reviewer of this paper for his suggestions and comments, which improved considerably the present paper.     

Mixed integer simulation optimization for optimal hydraulic fracturing and production of shale gas fields

Optimal development of shale gas fields involves designing a most productive fracturing network for hydraulic stimulation processes and operating wells appropriately throughout the production time. A hydraulic fracturing network design—determining well placement, number of fracturing stages, and fracture lengths—is defined by specifying a set of integer ordered blocks to drill wells and create fractures in a discrete shale gas reservoir model. The well control variables such as bottom hole pressures or production rates for well operations are real valued. Shale gas development problems, therefore, can be mathematically formulated with mixed-integer optimization models. A shale gas reservoir simulator is used to evaluate the production performance for a hydraulic fracturing and well control plan. To find the optimal fracturing design and well operation is challenging because the problem is a mixed integer optimization problem and entails computationally expensive reservoir simulation. A dynamic simplex interpolation-based alternate subspace (DSIAS) search method is applied for mixed integer optimization problems associated with shale gas development projects. The optimization performance is demonstrated with the example case of the development of the Barnett Shale field. The optimization results of DSIAS are compared with those of a pattern search algorithm.     

Partial constraint satisfaction approaches for optimal operation of a hydropower system

Optimal operation models for a hydropower system using partial constraint satisfaction (PCS) approaches are proposed and developed in this study. The models use mixed integer nonlinear programming (MINLP) formulations with binary variables. The models also integrate a turbine unit commitment formulation along with water quality constraints used for evaluation of reservoir downstream water quality impairment. New PCS-based models for hydropower optimization formulations are developed using binary and continuous evaluator functions to maximize the constraint satisfaction. The models are applied to a real-life hydropower reservoir system in Brazil. Genetic Algorithms (GAs) are used to solve the optimization formulations. Decision maker's preferences towards power production targets and water quality improvements are incorporated using partial satisfaction constraints to obtain compromise operating rules for a multi-objective reservoir operation problem dominated by conflicting goals of energy production, water quality and consumptive water uses.     

Non-linear singular integral representation for petroleum reservoir engineering

A new mathematical model is proposed in order to determine the properties of the reservoir materials, when oil reserves are moving through porous media, which is a very important problem of petroleum reservoir engineering. Thus, the above problem is reduced to the solution of a non-linear singular integral equation, which is numerically evaluated by using the singular integral operators method (SIOM). Also, several properties of the porous medium equation, which is a Helmholtz differential equation, are analyzed and investigated. An application is finally given for a well testing to be checked when an heterogeneous oil reservoir is moving in a porous medium. By using the SIOM, the pressure response from the well test conducted in the above heterogeneous oil reservoir is calculated.     

Earthquake‐induced hydrodynamic pressures on a 3D rigid dam–reservoir system using DRBEM and a radiation matrix

The dual reciprocity method is applied to determine the hydrodynamic pressure distribution in a three‐dimensional dam–reservoir system subjected to earthquake excitation. The reservoir domain is idealized as a finite region of irregular geometry adjacent to the dam followed by an infinite domain of uniform cross‐section in the upstream direction. The reservoir hydrodynamic pressure response is governed by the Helmholtz equation subject to free surface, dam–reservoir interface, absorbing bottom/banks and radiation boundary conditions. A three‐dimensional (3D) dual reciprocity model is developed to determine the hydrodynamic pressure in the finite reservoir domain. A radiation matrix is developed and introduced to relate the hydrodynamic pressure and its normal derivative on the interface between the finite and infinite domains. The three‐dimensional radiation model used is developed by applying a two‐dimensional dual reciprocity formulation along the interface of the finite and infinite reservoirs together with a continuum solution in the upstream direction of the infinite domain. The model is compared for the hydrodynamic response of a three‐dimensional rectangular reservoir and found to be in excellent agreement with results obtained from a model based on the analytical formulation existing in the literature. Copyright © 2003 John Wiley & Sons, Ltd.     

Pressure transient analysis of deformable reservoirs

A new integrated methodology of evaluating the change in the permeability of a fractured or pressure-sensitive porous reservoir based on analytical or numerical simulation of a fluid inflow to a well has been proposed. The analysis draws on results of well tests. Analytical solutions of direct and inverse problems allow an evaluation of the permeability variation with decreasing pressure. Numerical simulation of an unsteadystate fluid inflow to a well (a direct problem) allows determining the diagnostic signs of variation in the reservoir permeability from the dynamics of the bottom hole pressure and an assessment of the evaluations obtained from solving an inverse problem. The methodology has been approved using results of some well tests.     

Seismically induced, non-stationary hydrodynamic pressure in a dam-reservoir system

Stochastic seismic analysis of hydrodynamic pressure in a dam-reservoir system is presented in this paper. The analysis is conducted assuming infinite reservoir compressible fluid and modeling seismic acceleration as a normal zero-mean stochastic process obtained by Penzien filter. The non-homogeneous boundary conditions associated to the problem have been incorporated into the equation of pressure wave scattering in the form of a forcing function turning the non-homogeneous boundary value problem into an homogeneous one. Solution obtained via modal analysis in time-domain is coupled with the use of classical Itô stochastic differential calculus to characterize the stochastic hydrodynamic pressure field. Both cases of hydrodynamic pressure acting along the upstream face of the dam in presence of stationary and non-stationary seismic accelerations have been considered.     

Modelling and state estimation for a two-dimensional moving boundary problem

The five-spot waterflooding problem has been modelled as a two-dimensional moving boundary problem with a sharp interface separating the water and oil regions. The Galerkin method was used to solve for the shape and movement of the interface, as well as for the pressures in the reservoir. Having obtained a working model, the extended Kalman filter was then used to estimate the interfacial position when using corrupted pressure measurements from a single sensor in the field.     

Productivity model of horizontal wells in a sour gas reservoir

ABSTRACT

The utilization of a horizontal well has a great significance in the development of sour gas reservoir. The accurate prediction of the productivity of horizontal well will become more and more important in developing sour gas reservoir. In this paper, the effect of sulfur deposition on permeability is considered and a productivity prediction formula of the horizontal well is established. The effects of the length of horizontal well, the effective thickness of the reservoir, elemental sulfur deposition, and reservoir heterogeneity on productivity are analyzed and calculated. The theoretical results show that elemental sulfur disposition and the heterogeneity are the most important factors. According to the field case, the calculating results of improved Joshi’s equation approaches the real productivity, which means that it could be used to predict the productivity of horizontal well at initial stage during sour gas reservoir development. The results can be used as a reference for the development of similar sour gas reservoir.     

Optimal operation of a multibasin reservoir system

A simulation-optimization procedure is presented for evaluating the extent of interbasin transfer of water in the Peninsular Indian river system consisting of 15 reservoirs on four river basins. A system-dependent simulation model is developed incorporating the concept of reservoir zoning to facilitate releases and transfers. The simulation model generates a larger number of solutions which are then screened by the optimization model. The Box complex nonlinear programming algorithm is used for the optimization. The performance of the system is evaluated through simulation with the optimal reservoir zones with respect to four indices, reliability, resiliency, vulnerability and deficit ratio. The results indicate that by operating the system of 15 reservoirs as a single unit the existing utilization of water may be increased significantly.     

A pulse tube cryocooler with a cold reservoir

Phase difference between pressure wave and mass flow is decisive to the cooling capacity of regenerative cryocoolers. Unlike the direct phase shifting using a piston or displacer in conventional Stirling or GM cryocoolers, the pulse tube cyocooler (PTC) indirectly adjusts the cold phase due to the absence of moving parts at the cold end. The present paper proposed and validated theoretically and experimentally a novel configuration of PTC, termed cold reservoir PTC, in which a reservoir together with an adjustable orifice is connected to the cold end of the pulse tube. The impedance from the additional orifice to the cold end helps to increase the mass flow in phase with the pressure wave at the cold end. Theoretical analyses with the linear model for the orifice and double-inlet PTCs indicate that the cooling performance can be improved by introducing the cold reservoir. The preliminary experiments with a home-made single-stage GM PTC further validated the results on the premise of minor opening of the cold-end orifice.     

Removal and degradation of phenol in a saturated flow by in-situ electrokinetic remediation and Fenton-like process.

In this laboratory study, a sandy loam soil saturated with phenol solution was treated by in-situ electrokinetics-Fenton process incorporated with a permeable reactive wall of scrap iron powder (SIP). The soil was contaminated and saturated with aqueous phenol solution of 90-115 mg/kg in concentration. It was then placed in a soil cell. The soil cell was assembled with an anode reservoir and a cathode reservoir at its ends. A bed of SIP (1.05-32.69 g) was inserted in the soil cell at a distance of 5 cm from the anode reservoir compartment. For the test runs, 0.3% H(2)O(2) was used as the anode reservoir fluid, whereas de-ionized water was used as the cathode reservoir fluid. An electric gradient of 1 V/cm was applied to enhance the saturated flow in the soil cell for a period of 10 days. Experimental results have shown that the electroosmotic (EO) flow quantity decreased as the amount of SIP increased. This phenomenon was in good agreement with the results showing the value of EO permeability increased with a decreasing amount of SIP. Results also showed that throughout the test period the cumulative, consumed mass of H(2)O(2) in the anode reservoir increased as the amount of SIP decreased. On the other hand, the cumulative, increased mass of phenol in the cathode reservoir was found to increase with a decreasing amount of SIP. Meanwhile, the residual phenol concentration in the soil cell was found to decrease with a decreasing amount of SIP. When 1.05 g scrap iron powder was used, an overall removal and destruction efficiency of phenol of 99.7% was obtained. Therefore, it is evident that an in-situ combined technology of electrokinetic remediation and Fenton-like process is capable of simultaneously removing and degrading the phenol in a saturated flow.     

Controlling entanglement dynamics of two qubits coupled to a common reservoir via a coherent field

We investigate the time evolution of entanglement between two two-level atoms which are coupled to a common multimode electromagnetic reservoir and simultaneously driven by a coherent field. We find that the entanglement can always be created and maintained with a moderate intensity of the driving field during the track of approaching steady entangled states when both atoms are initially in their ground states and the reservoir is in the vacuum state or the squeezed vacuum state. We also show that the steady-state entanglement between the atoms can be enhanced by use of the coherent field when the reservoir is in the weakly squeezed vacuum state. More interestingly, in the squeezed reservoir case, the sudden death period in the time evolution of the entanglement can be removed by use of the coherent driving field.     

Flow of non-newtonian fluid through porous media

This article shows the solutions of the nonlinear equations describing the transient flow of power law fluids through a porous medium. These are obtained by means of a generalized Boltzmann transformation approach for several cases of practical interest in interpretation of well-flow tests of short duration, used currently in oil reservoir engineering for obtaining the reservoir properties. A formulation of a moving boundary problem for a short time, appearing during the production of fluids by elastic decompression, is used in deriving the exact solutions in closed form for certain cases. The presence of a decompression front is physically demonstrated and its location in the reservoir at a given time is determined. The limitations associated with the generalized Boltzmann transformation approach in solving the nonlinear equations of power law fluid flow in oil reservoirs are shown and discussed with regard to the interpretation of the well-flow test analysis.     

Hydro energy management optimization in a deregulated electricity market

When electricity prices were regulated, hydropower optimization often considered only the inflow uncertainty. In a deregulated electricity market, price uncertainty must be also considered in addition to inflow uncertainty. This makes the operation problem more challenging due to inclusion of the objective of minimizing risk. It also makes the objective function nonlinear while the estimation of risk is problematic. For dealing with uncertainty, a set of finite scenarios of inflow or price sequences may form the evolution of information over the stages that are used in optimization algorithms. Such implicit optimization methods can be seen as an extension of deterministic optimization. A disadvantage is the number of scenarios may grow exponentially in multi-stage optimization problems, even with only a few branches at each stage. An explicit method, denoted as the Fletcher-Ponnambalam model (FP), has been recently developed for the first and second moments of the storage state distributions in terms of moments of the inflow distributions. This method provides statistical information on the nature of random behaviour of the system state variables without any discretization and hence suitable for multireservoir problems. Also not considering scenarios makes it computationally inexpensive, as there is little growth to the size of the original problem. In this paper, we introduce the price uncertainty into the FP model; our results indicate that the method could achieve optimum policy considering also the reduction of risk, using the second moment information. Our study is for medium term operations of a single reservoir. The results are compared with corresponding results from simulation and where possible, with the well-known Benders' Decomposition method (BD).