Efficient Use Of Available Energy Research Articles

Entropy Generation Minimization of Two-Phase Flow Irreversibilities in Hydrocarbon Reservoirs

The efficient use of available energy in hydrocarbon extraction processes is essential to reducing overall emissions in the petroleum industry. The inefficient design of an extraction process leads to higher emissions per unit mass of hydrocarbon recovery. Fluid friction and heat transfer are irreversible processes that are vital in decreasing the overall system’s operational efficiency. To reduce these irreversible energy losses in the petroleum reservoir production’s life, contributing factors such as the characteristic features of a reservoir formation, reservoir fluids, and production rate are investigated in this paper. This study examines irreversible energy loss in porous media and wellbore formations using entropy generation minimization at various stages of production and thermodynamic conditions, eventually achieving higher hydrocarbon recovery factors. Entropy production is used to develop predictive models that calculate reservoir and wellbore energy losses for multiphase flow. The proposed models consider oil and water as the working fluids in a porous medium and a wellbore. This paper also investigates the thermophysical effects around the wellbore by incorporating Hawkin’s model. A sensitivity analysis assessed the impact of rock and fluid properties and thermodynamic conditions such as temperature, wettability, and capillary pressure on the total entropy generation. The findings reveal that the capillary pressure significantly impacts the oil and water recovery factor and total entropy production. Additionally, the capillary pressure strongly influences the reservoir production life. The two-phase models show that as the recovery factor increases, the total entropy production decreases at lower production rates. This article helps to address the impact of irreversible processes on multiphase hydrocarbon reservoir operational efficiency. Furthermore, the results obtained from the numerical-simulation model open up a new research area for scholars to maximize the recovery factor using entropy generation minimization in heterogeneous reservoirs.

Particle swarm optimization algorithm for ignition of hydrogen isotopes (deuterium–tritium) pellets

Recent improvements on high power lasers have made access to dense and hot plasmas possible realizing the inertial confinement fusion (ICF). Results from Osaka University experiments found that higher energy gains are reachable through ideal adiabatic shock-free volume ignition. Laser pulses limit the range of laser input energy. Thus, it becomes necessary to make efficient use of available energy to obtain the highest gain. The present paper aims to investigate the attainment of highest gain for D–T fuel using this energy with iteration model. It is shown that the maximum gain of 1.36 × 106 is obtained only at input energy of 7.27 × 1010 J, volume of 0.586 cm3 and 8133times of solid state density.

Evaluation of data for developing an adaptive model of thermal comfort and preference

Energy requirements in India, and in all developing countries, are rising at over 10 per cent annually and may double after 2020. With the Energy Crisis there is a demand for the promotion of greater saving in energy and efficient use of available energy. This not only has the potential to meet the ever-increasing demand but it must be recognized as an important and sustainable solution for the energy crisis as energy saved is energy produced. Many studies have shown that, to the occupants, the most important consideration is thermal comfort. Thermal comfort is defined by ASHRAE, as that state of mind, which expresses satisfaction with the thermal environment. The context of the study of thermal comfort is the multi-billion dollar air-conditioning (AC) industry. The need to define ‘comfortable environments’ arose from this industry. Before air-conditioning buildings were built on the experience of countless builders of the past, experience being passed down the generations. One of the more contentious theoretical issues in the applied research area of thermal comfort has been the dialectic between “adaptive” and “static” models. Apart from having disparate methodological bases (the former laboratory-experimental, the latter field-based), the two approaches have yielded starkly differing prescriptions for how the indoor climate of buildings should be managed. These prescriptions carry implications for the types of permissible building designs, the means by which their thermal environments are controlled, and the amounts of energy they consume in the production of habitable indoor climates. Static models have led to indoor climate standards that have been universally applied across all building types, are characterized by minimal recognition of outdoor climatic context, and are contributing to an increased reliance on mechanical cooling. In contrast, proponents of adaptive models have advocated variable indoor temperature standards that more fully exercise the adaptive capabilities of building occupants. This approach potentially leads to more responsive environmental control algorithms, enhanced levels of occupant comfort, reduced energy consumption, and the encouragement of climatically responsive building design. Despite these apparent differences, our review of the research literature emerging from both approaches indicated that this seemingly irreconcilable split was primarily the result of narrow definitions of the term “thermal adaptation”, and that there were opportunities to bridge some of the gap between the hypotheses. This paper attempts to discuss the methods of evaluating the thermal preferences of the people of composite climate for developing an adaptive model of thermal comfort and preference.

Making carbon sequestration a paying proposition

Atmospheric carbon dioxide (CO(2)) has increased from a preindustrial concentration of about 280 ppm to about 367 ppm at present. The increase has closely followed the increase in CO(2) emissions from the use of fossil fuels. Global warming caused by increasing amounts of greenhouse gases in the atmosphere is the major environmental challenge for the 21st century. Reducing worldwide emissions of CO(2) requires multiple mitigation pathways, including reductions in energy consumption, more efficient use of available energy, the application of renewable energy sources, and sequestration. Sequestration is a major tool for managing carbon emissions. In a majority of cases CO(2) is viewed as waste to be disposed; however, with advanced technology, carbon sequestration can become a value-added proposition. There are a number of potential opportunities that render sequestration economically viable. In this study, we review these most economically promising opportunities and pathways of carbon sequestration, including reforestation, best agricultural production, housing and furniture, enhanced oil recovery, coalbed methane (CBM), and CO(2) hydrates. Many of these terrestrial and geological sequestration opportunities are expected to provide a direct economic benefit over that obtained by merely reducing the atmospheric CO(2) loading. Sequestration opportunities in 11 states of the Southeast and South Central United States are discussed. Among the most promising methods for the region include reforestation and CBM. The annual forest carbon sink in this region is estimated to be 76 Tg C/year, which would amount to an expenditure of $11.1-13.9 billion/year. Best management practices could enhance carbon sequestration by 53.9 Tg C/year, accounting for 9.3% of current total annual regional greenhouse gas emission in the next 20 years. Annual carbon storage in housing, furniture, and other wood products in 1998 was estimated to be 13.9 Tg C in the region. Other sequestration options, including the direct injection of CO(2) in deep saline aquifers, mineralization, and biomineralization, are not expected to lead to direct economic gain. More detailed studies are needed for assessing the ultimate changes to the environment and the associated indirect cost savings for carbon sequestration.

Cannibals and parasites: conflicting regulators of bimodality in high latitude Arctic char, Salvelinus alpinus

Unexploited populations of Arctic char (Salvelinus alpinus) sampled in autonomous lake ecosystems in northern Svalbard demonstrate extraordinary catch curves with age and size frequency distributions characterized by discrete bimodality. Analyses of size‐age relationship, summer diet and food‐related intestinal parasite intensities of modal char groups revealed a pattern of discrete ontogenetic niche shifts. Life‐history changes at age 10–15 and size 200–300 mm/50–300 g involved shifting from an initial mode of small‐sized, slow‐growing and sexually mature individuals feeding on micro‐crustaceans and aquatic insects (Chironomidae, Trichoptera), to a terminal mode of large‐sized and fast‐growing cannibals. Cannibalism, however, was found to result in accumulation of cestodan parasites, of which Diphyllobothrium ditremum increases age‐related mortality rates and may be lethal at 1500–2000 plerocercoids. Genetically allopatric populations with cannibalism demonstrated a female‐biased sex ratio, primarily in the initial mode, suggesting sexual asynchrony in their ontogeny. By contrast, a small population of large‐sized, non‐cannibalistic Arctic char feeding exclusively on the large amphipod Gammaracanthus lacustris, demonstrated unimodal size and age frequency distribution, faster growth, an excess of males and lower parasite burden. Seasonal prey shortage and slow juvenile growth in association with fitness components favoring large body size is a suggested mechanism for inducing cannibalism. Although not the basic cause of bimodality as such, it is concluded that ontogenetic niche shift by cannibalism reinforces discrete age modal divergence resulting in the numerical preponderance of large‐sized individuals in these marginal char populations. Cannibalism is thus considered an important strategy for survival of landlocked Arctic char in the High Arctic. As a conflicting cost to the more efficient use of available energy by larger individuals, the accumulation of cestodan parasites in cannibals, however, will reduce the survival rate of old individuals and accelerate their termination within this modal group.

"Dakota Sun" - the next generation solar powered racing vehicle

Based on the experience gained from Sunrayce '95, the Solar Motion Team has made many changes to the design of the next generation solar car. These changes have resulted in a vehicle that is very different from the "Solar Rolar", The Dakota Sun is a three wheeled vehicle with separate cab and solar array. This design allows for improved aerodynamics, decreased weight, lower rolling resistance, and ease of manufacture compared to the four wheeled catamaran used in the last race. However, this design sacrifices total enclosed wheel base area, additional room for components, and added power from side solar panels, The major objectives for the team's redesigned Sunrayce '97 entry are: systems integration; decrease the weight of the car; decrease aerodynamic drag; more efficient use of available energy; and increased driver safety. The team has set a standard to use the latest available technology. Although this increases the complexity of the components, by using a systems engineering approach the "Dakota Sun" has evolved into a more integrated vehicle. This philosophy of integrated design has resulted in great improvements in mechanical design and manufacturing techniques, as well as electrical innovations. The major design changes evident from the original Sunraycen '95 vehicle are the result of an evolutionary design process that has produced the highly competitive Sunraycel '97 design outlined in this article.

The Influence of Availability Costs on Optimal Heat Exchanger Design

Optimizing heat exchangers based on second-law rather than first-law considerations ensures that the most efficient use of available energy is being made. In this paper, second-law efficiency is used to develop a new technique for optimizing the design of heat exchangers. The method relates the operating costs of the exchanger to the destruction of availability caused by the exchanger operation. The destruction of availability is directly related to the second-law efficiency of the exchanger. This allows one to find the NTU at which the benefits of reduced availability losses are offset by the costs of added area; this is the optimal point. It can be difficult to determine the proper cost of irreversibility to be used in the optimization process. This issue can be handled by including the irreversibility cost in a dimensionless parameter that represents the ratio of annual ownership costs to annual operating costs that include irreversibility costs. In this way, each heat exchanger designer can estimate the costs of irreversibilities for his particular system, and then use the generalized method that is developed herein for determining the optimal heat exchanger size. The method is applicable to any heat exchanger for which the ε-NTU-R relationships are known.