Evaluation of two-dimensional approach for computational modelling of heat and momentum transfer in liquid containing horizontal cans and experimental validation

Axi-symmetric approach in vertical cans lead to 2-dimensional (2D) model with shorter computational times. For horizontal cans containing liquids, this approach is not possible due to internally evolved natural convection. If an assumption is made to neglect gravitational effect in horizontal direction, it may be possible to use a 2D model. Therefore, the objective of this study was to evaluate this approach numerically and experimentally. In simulations, continuity, energy and momentum equations were solved in 2D and 3D using Ansys CFX 12.1 for horizontal cans containing water and another viscous liquid. In experiments, water filled cans were prepared, and temperature data were compared with simulation results. The results demonstrated the possible use of 2D approach in modelling for liquid containing horizontal cans with significant reduction in computational times. Optimization algorithms of simulation programs are also expected to be used in combination with simulation studies since computation times are reduced significantly.     

A snapshot of geothermal energy potential and utilization in Turkey

Turkey is one of the countries with significant potential in geothermal energy. It is estimated that if Turkey utilizes all of her geothermal potential, she can meet 14% of her total energy need (heat and electricity) from geothermal sources. Therefore, today geothermal energy is an attractive option in Turkey to replace fossil fuels. Besides, increase in negative effects of fossil fuels on the environment has forced many countries, including Turkey, to use renewable energy sources. Also, Turkey is an energy importing country; more than two-thirds of her energy requirement is supplied by imports. In this context, geothermal energy appears to be one of the most efficient and effective solutions for sustainable energy development and environmental pollution prevention in Turkey. Since geothermal energy will be used more and more in the future, its current potential, usage, and assessment in Turkey is the focus of the present study. The paper not only presents a review of the potential and utilization of the geothermal energy in Turkey but also provides some guidelines for policy makers.     

An exposé of bioenergy and its potential and utilization in Turkey

Turkey is heavily dependent on expensive imported energy resources (oil, gas and coal) that place a big burden on the economy. Air pollution is also becoming a great environmental concern in the country. In this regard, renewable energy resources appear to be one of the most efficient and effective solutions for clean and sustainable energy development in Turkey. Turkey's renewable sources are the second largest source for energy production after coal. About two-thirds of the renewable energy produced is obtained from bioenergy, which is used to meet a variety of energy needs, including generating electricity, heating homes, fueling vehicles and providing process heat for industrial facilities. The amount of usable bioenergy potential of Turkey is approximately 17 Mtoe. This article not only presents a review of the potential and utilization of the bioenergy in Turkey but also provides some guidelines for policy makers.     

Electricity demand analysis using cointegration and ARIMA modelling: A case study of Turkey

In the early 2000s, the Republic of Turkey has initiated an ambitious reform program in her electricity market, which requires privatization, liberalization as well as a radical restructuring. The most controversial reason behind, or justification for, recent reforms has been the rapid electricity demand growth; that is to say, the whole reform process has been a part of the endeavors to avoid the so-called “energy crisis”. Using cointegration analysis and autoregressive integrated moving average (ARIMA) modelling, the present article focuses on this issue by both providing an electricity demand estimation and forecast, and comparing the results with official projections. The study concludes, first, that consumers’ respond to price and income changes is quite limited and therefore there is a need for economic regulation in Turkish electricity market; and second, that the current official electricity demand projections highly overestimate the electricity demand, which may endanger the development of both a coherent energy policy in general and a healthy electricity market in particular.     

Regulatory reform in Turkish energy industry: An analysis

The Republic of Turkey has initiated an ambitious reform program in the most important segments of her energy market; which requires privatization, liberalization as well as a radical restructuring of these industries. However, there is no consensus that the measures introduced are optimal. The present article attempts, first, to evaluate the regulatory framework created by the laws of 2001 in terms of economic efficiency considerations; and second, to determine what still needs to be done to improve the current situation. The paper not only provides an analysis of these reforms but also lists some policy suggestions. The study concludes that despite relatively good legislative framework, in practice, the reforms in Turkey are far from ideal as they are mainly in the form of “textbook reforms”; and therefore a significant amount of work still lies ahead of Turkey to set up a fully fledged energy market.     

Thawing and freezing of selected meat products in household refrigerators

Recently, several manufacturers of domestic refrigerators have introduced models with “quick thaw” and “quick freeze” capabilities. In this study, the time required for freezing and thawing different meat products was determined for five different models of household refrigerators. Two refrigerators had “quick thaw” compartments and three refrigerators had “quick freeze” capabilities. It was found that some refrigerator models froze and thawed foods significantly faster than others (P<0.05). The refrigerators with the fastest freezing and thawing times were found to be those with “quick thaw” and “quick freeze” capabilities. Heat transfer coefficients ranged from 8 to 15 Wm⁻²K⁻¹ during freezing, and the overall heat transfer coefficients ranged from 5 to 7 Wm⁻² K⁻¹ during thawing. Mathematical predictions for freezing and thawing time in the refrigerators gave results similar to those obtained in experiments. With the results described, manufacturers can improve their design of refrigerators with quick thawing and freezing functions.     

Velocity and temperature field characteristics of water and air during natural convection heating in cans

Presence of headspace during canning is required since an adequate amount allows forming vacuum during the process. Sealing technology may not totally eliminate all entrapped gases, and headspace might affect heat transfer. Not much attention has been given to solve this problem in computational studies, and cans, for example, were mostly assumed to be fully filled with product. Therefore, the objective of this study was to determine velocity and temperature evolution of water and air in cans during heating to evaluate the relevance of headspace in the transport mechanism. For this purpose, canned water samples with a certain headspace were used, and required governing continuity, energy, and momentum equations were solved using a finite volume approach coupled with a volume of fluid element model. Simulation results correlated well with experimental results validating faster heating effects of headspace rather than insulation effects as reported in the literature. The organized velocity motions along the air-water interface were also shown. Practical Application: Canning is a universal and economic method for processing of food products, and presence of adequate headspace is required to form vacuum during sealing of the cans. Since sealing technology may not totally eliminate the entrapped gases, mainly air, headspace might affect heating rates in cans. This study demonstrated the increased heating rates in the presence of headspace in contrast with some studies in the literature. By applying the effect of headspace, required processing time for thermally processed foods can be reduced leading to more rapid processes and lower energy consumptions.