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71.
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R.H. Ericksen 《Polymer》1985,26(5):733-746
Creep of Kevlar 29, Kevlar 49 and PRD 49-III fibres was investigated. The fibres exhibited transient creep and the strain-time relationship was represented by a logarithmic time law. The creep strain recovered with time when the load was removed. Upon reloading to the same creep stress the strain-time relationship was again logarithmic but the creep rate was reduced. Modulus measurements were made during the creep test and these showed that the modulus increased with time. This result indicated a crystallite rotation mechanism which could account for the experimentally observed creep strain. Creep in PRD 49-III fibres exhibited a small temperature dependence over the temperature range 20°C to 150°C. The apparent creep activation energy was consistent with the range of values reported for hydrogen bonding. This suggests one possible creep mechanism in which the combined action of stress and thermal activation causes rearrangement of intercrystalline bonds in the crystallite boundaries resulting in boundary creep. Boundary creep allows crystallite rotation which produces the macroscopic creep strain. Boundary creep is discussed in terms of the fibre morphology and a model of delayed elasticity. 相似文献
74.
Emmanuel O. Egbogah Richard A. Dawe 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1985,35(3):132-144
Recent studies have suggested the possibility of spontaneous emulsification as a mechanism for enhanced oil recovery (EOR). The discussions have, however, remained essentially qualitative. A study was therefore undertaken to estimate quantitatively the contribution of spontaneous emulsification as an EOR mechanism. The tests were conducted on several bulk liquid/liquid systems as well as by displacement experiments in unconsolidated synthetic sand packs. Spontaneous emulsification was found to be a mechanism for EOR: the estimated extra contribution to EOR due to this mechanism was found to be significant in laboratory scale displacement experiments. Tertiary recovery was always greater when spontaneous emulsification was evident than otherwise. Results of tests on bulk liquid/liquid systems indicate that the occurrence or absence of spontaneous emulsification can be correlated with the values of ‘partition parameter’. It may be concluded that higher oil recoveries may be achieved in chemical EOR processes where interface mass transfer (and the accompanying spontaneous emulsification) occurs. The evaluation of efficiency of residual oil mobilisation through the capillary number theory (with and without spontaneous emulsification) is also discussed. Displacement tests with spontaneously emulsifying systems showed that residual oil left behind a conventional waterflood was mobilised in a range of capillary numbers much less than that which applies to low-tension waterfloods. 相似文献
75.
热环是用于非相邻冷热源间热量传递或余热回收的节能装置。本文对热环的基本原理、特点进行了简要介绍 ,在此基础上 ,分析建立了热环的输热能力、输热系数、工作温度等性能指标的计算方程 ,并进行了较系统的实验研究 相似文献
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A simple 3-D physical model has been developed to investigate the use of in-situ combustion in heterogeneous reservoirs. Gas over-ride phenomena is one of the major causes of instability of combustion process; gas override results in poor sweep efficiency with subsequent low oil recovery. However, the use of horizontal wells in direct line drive arrangement has shown a great deal of combustion stability and propagation by means of controlling gas override This paper has extended the scope of using horizontal wells in direct line drive configuration in heterogeneous reservoirs. Three cases of reservoir heterogeneity were investigated in this study. In the first case, a dual-layer permeability of sand was used (a high permeability layer on top and a low permeability layer on bottom); in the second case, placement of the aforementioned layers was swapped, and in the third case, a high permeability streak was sandwiched between two low permeability layers of fine sand. The results indicated that a stable combustion front has been achieved in the first two cases with a high oil recovery, however the performance of the combustion process markedly deteriorated when a high permeability streak layer was utilised as a result of a severe low temperature oxidation due to oxygen channelling through the streak, with subsequent poor sweep efficiency and in turn low oil recovery. The use of horizontal wells as producers and injectors in a line drive configuration is beneficial and effective for minimising the effect of reservoir heterogeneity to some extent. 相似文献
79.
确定异常高压气藏地质储量和可采储量的新方法 总被引:7,自引:1,他引:6
基于文献[1]的定容,封闭,异常高压气藏的物质平衡方程式,提出了确定异常高压气藏原始地质储量,可采储量和采收率的新方法,通过实例的应用和对比表明,提供的新方法是适用的有效的。 相似文献
80.
Economic ideas and processes are becoming increasingly integrated with more traditional engineering and hydrologic models
of water management problems. Combining economic management concepts and performance indicators with an engineering-level
of understanding of a hydrologic system can provide results and insights more directly relevant for water management decisions
and policies. When such models are developed and used with involvement of stakeholders, they can become a basis for shared
understanding of water problems as a foundation for negotiated management and policy solutions. When implemented with optimization
software, integrated hydro-economic models also can suggest promising innovative solutions for policy-makers to consider.
Their applications to river basin management problems are reviewed. Economic and integrated economic-engineering-hydrologic
modeling is then discussed in the context of the evolving European Water Framework Directive. Relevant items are cost recovery
and water pricing, cost-effectiveness of water management measures, and public participation in decision processes. 相似文献