A mechanistic analysis of viscous fingering in low-tension polymer flooding in heavy-oil reservoirs

Modeling of the low tension polymer flooding (LTPF) in heavy oil reservoirs suffers from the paucity of detailed knowledge of viscous instability or fingering effects. Major limitations of previous approaches for studying viscous fingering in immiscible displacements are that the reported experiments have been conducted utilizing the linear displacements schemes in the media with high, single-phase permeabilities. Consequently, viscous instability has not been studied in low-permeability media and using the displacement schemes similar to the oil-field patterns (e.g., five-spot). To help understand viscous fingering in LTPF in heavy oil reservoirs and to overcome the limitations of previous studies, we conducted experiments in the low-permeability, one-quarter, five-spot patterns. New insights into the main driving mechanisms for viscous fingering are proposed. In summary, the mechanisms of spreading, splitting, coalescence, and microscopic crossflow drive the finger growth. In addition, the viscous fingers are readily initiated in the porous medium, but they can be damped out before traveling very far. This damping of the viscous fingers is due to the flow of the two phases in a direction transverse to the direction of bulk fluid movement as a result of dispersive processes such as stream splitting. Also, the initially-developed fingers may deteriorate over the time of displacement. This depends on the distance between the injector and producer and width of the porous medium. The presence of instabilities that look like fingers and stable displacements behind the unstable front were discovered. The results also indicate that a stable zone exists and progresses at varying velocities. Finally, we reveal three different types of displacements that occur in LTPF: stable displacements, displacement with macroscopic viscous fingering, and displacements with both macroscopic and microscopic viscous fingering.     

Extended beam search for non-exhaustive state space analysis

State space explosion is a major problem in both qualitative and quantitative model checking. This article focuses on using beam search, a heuristic search algorithm, for pruning weighted state spaces while generating. The original beam search is adapted to the state space generation setting and two new variants, motivated by practical case studies, are devised. These beam searches have been implemented in the μCRL toolset and applied on several case studies reported in the article.     

Simulation of reversible chain transfer catalyzed polymerization (RTCP): effect of different iodide based catalysts

Monte Carlo kinetic simulation method was performed to study the reversible chain transfer catalyzed polymerization (RTCP) of styrene in 80°C. The effect of different iodide based catalysts (AI) was investigated on RTCP systems by simulating the chain length distribution, the depletion rate of polymerization ingredients, average molecular weights and the monomer conversion. In RTCP systems a narrow distribution was obtained compared to iodide-mediated polymerization. Superior reversible chain transfer reaction constants (k_a and k_da) led to a more uniform chain length distribution and a faster PDI decrement. In each RTCP system k_da/k_a ratio, designates the concentration of A* by dictating the dominant side of exchange equilibriums which specifies the number of cross-termination reactions. Addition of cross-termination reactions to the iodide-mediated polymerization system decreases the number of combination reactions leading to lower average molecular weights. Higher k_da/k_a ratios also consequences in faster catalyst depletions and lessen monomer conversions. On the other hand, PhE-I was found to deplete rapidly in RTCP systems, changing the nonlinear increase of the number average molecular weight to a linear pattern. The Monte Carlo simulation results were in a fine agreement with experimental data which were obtained from different RTCP systems.     

Economic feasibility of solid oxide fuel cell (SOFC) for power generation in Iran

Supply utilities needed in site with the lowest cost and emission and highest efficiency are considered one of the main concerns of the process industry’s owners that requires doing more research in this area. In this research, during a case study, first comprehensive site of producing utility is optimized, and then the energy and environmental analysis of fuel cell system is taken place. Then fuel cell integration with utility site during two scenarios of entire supply of steam generated by HRSG of gas turbine and entire supply of gas turbine generated power was evaluated. According to the evaluation done, if the target is the entire supply of steam generated by HRSG of gas turbine, selecting solid oxide fuel cell (SOFC) system is economically and environmentally more affordable. So if the target is preheating, selecting the system is based on entire supply of steam generated by the boilers, and the number of eight SOFC systems will be required by which a power about 22 MW can be produced.     

Dispersed phase holdup and slip velocity of phases in a pulsed packed column in conditions with and without mass transfer

Dispersed phase holdup and slip velocity of phases were measured in a pilot plant pulsed packed column with a diameter of 76.2 mm for two different chemical systems in conditions with and without mass transfer. The effects of pulsation intensity, dispersed and continuous phases flow rates, interfacial tension and solute concentration on dispersed phase holdup and slip velocity of phases were investigated. A new empirical correlation in terms of the above‐mentioned parameters developed from the measurements is given for the prediction of slip velocity. The dispersed phase holdup was calculated by means of this correlation and very good agreement between calculated and experimental values was obtained.     

Development and thermal performance of wood-HPDE- PCM nanocapsule floor for passive cooling in building

Cooling demand in the building sector is growing rapidly; thermal energy storage systems using phase change materials (PCM) can be a very useful way to improve the building thermal performance. This work shows the benefits of PCM when incorporated in wood fiber-polymer composite as floor cooling system using nano-encapsulated PCMs. The wood-plastic-NPCM composites were produced using compression molding process and its mechanical and thermal properties were investigated. Two dynamic simulators were employed to investigate synthesized composites thermal performance. Increasing NPCM content in WPC showed that the fluctuations of the simulator temperature was decreased while the heat fluxes through the floor was increased. The variations of ambient maximum temperature have little effect on the air temperature of the simulator with 40% PCM which indicates that the amount of PCM was enough for studied environmental condition. Field experiments were performed using two medium-scale test houses located on Tehran-Iran. It can be concluded that using NPCM helps to reduce heating and cooling demand. Moreover, the natural night ventilation by opening windows reduced the number of hours that the temperature is above 23°C from 499 h/year in case1 (without opening) to 255 h/year in case 2(with opening). This means that natural night ventilation could help reduce the overheating period to about 50% with the use of NPCM.     

A comparative study of group delay equalizers for satellite communications

This article presents a comparative study of four different group delay (GD) equalizers with a narrow band filter used as input multiplexer for a Ku‐band satellite transponder. A dual mode cylindrical filter with 36 MHz bandwidth is designed and fabricated. The filter GD is measured and two types of group‐delay equalizers are designed to fulfill the requirements of the transponder's GD mask. Two rectangular and two cylindrical equalizers are designed and their performance parameters, such as insertion loss and equalized bandwidth, are compared. In addition, a comparison between the designed first order (C‐section) and second order (D‐section) GD equalizers is done.     

Modeling and analysis of flow energy harvesters made of PZT ceramics considering different patches,cross-sections,and tip bodies

A nonlinear developed model for various PZT wind energy harvesters with arbitrary dimensions and location of electroceramics has been prepared. This model can describe unimorph and bimorph harvesters with different cantilever cross-sections attached to a tip body with different shapes. The system model has been validated with results reported in the literature. A set of parametric studies has been conducted to examine the influences of the cantilever shape in addition to the shape of the tip body. Furthermore, the impacts of load resistance and wind speed on the output power have been analyzed. The effects of number, position, and dimensions of piezoceramics on the harvester performance have also been investigated. It is found that by increasing the total area of electroceramics (including the length, width, or the number of PZT patches), the peak of the wind critical speed and the middle resistance range where the instability speed is very sensitive to the electrical load shifts toward the lower resistances. Moreover, several instrumental points to design efficient and affordable vibrating wind harvesters at low and high flows have been obtained.