Umit Unver

Evaluating thermal environments for sitting and standing posture

The human thermal environment can be represented by the air temperature, radiant temperature, air velocity, humidity, clothing and activity. This has implications for health, comfort and performance. An understanding of human thermoregulatory processes facilitates the design and development of improved heating and cooling systems. This study presents a computational model of thermal interactions between a human and the interior environment. The model is based on the heat balance equation for human body with different types of clothing ensembles, combined with empirical equations defining the sweat rate and mean skin temperature. Simulation has been performed by the use of steady state conditions, and two different posture positions, namely sitting and standing, are considered in this study. Results are in good agreement with available experimental data. The parametric studies show that the methodology described can provide an effective means for simulating thermal comfort level.

Comparison of Natural Gas Fired and Induction Heating Furnaces

Generally, in steel processing systems, steels are heated via induction or combustion furnaces. Natural gas fired furnaces have installation costs advantage while the induction furnaces have the advantages of less scale formation on the surface of the workpiece as well as less environmental pollutions. The operation cost of both systems is a vital argument to be solved. In this paper, a natural gas fired and induction heating furnaces of a forging process were studied. Thermodynamic analysis was performed for the furnaces which heat the steel workpiece up to 1,300 °C. The energy performances of both systems were analyzed and compared. It is concluded that, instead of a natural gas fired or an induction furnace, a hybrid furnace may save more energy and cost.

Influence of environmental temperature on exergetic parameters of a combined cycle power plant

Ambient conditions have significant effect on combined cycle power plants (CCPPs). Parameters-like efficiencies, fuel consumption, power production and even operation cost differ according to the ambient conditions that depend on the climate that cannot be changed. Therefore, deciding the location of the plant wisely would bring more efficient and profitable. In this paper, exergy analysis based on the second law of thermodynamics, considering environmental temperature variations, are performed for a cogeneration power plant. Mathematical model of analyse is introduced. Magnitudes of the variation of irreversibility, reversible power, power production and specific fuel consumption (SFC) are evaluated for the combined cycle. The results indicated that, decrease of environmental temperature augments the energy performance of the combined cycle form about 53% to 56% and improves the exergetic performance from about 51% to 56%. However, the augmentation via temperature decrease is not continuous. It is shown that the environmental temperature decrease causes a reduction about 5% in the SFC.

Performance Estimation of Gas Turbine System via Degree-Day Method

Nowadays the focus of the power sector is on renewable energy sources. Even so, in Turkey, the most preferred power plants are still co-generation power plants. Considering installed power, gas turbine power plants are the most used type. In gas turbine power cycles, both power and efficiency are highly affected by atmospheric temperature. In this study, the degree-day method is used to expose the variation of the electric power of a gas turbine with respect to atmospheric conditions. The installed capacity of the gas turbine is 237 MW. The operating data were supplied by Ovaakca Power Plant Administration of Bursa/Turkey. In this paper it is indicated that, for a 45 °C increment of atmospheric temperature, mass flow through the compressor at a unit time decreases by about 85.2 kg. Therefore, the compression work decreased by about 11.45 %. In addition, by means of the atmospheric temperature increment, both the total energy input via natural gas and intake airflow rate were decreased by 17.1 % and this resulted in a reduction in net electric power production.

A novel method for prediction of gas turbine power production: Degree-day method

Gas turbines are widely used in the energy production. The quantity of the operating machines requires a special attention for prediction of power production in the energy marketing sector. Thus, the aim of this paper is to support the sector by making the prediction of power production more computable. By using the data from an operating power plant, correlation and regression analysis are performed and linear equation obtained for calculating useful power production vs atmospheric air temperature and a novel method, the gas turbine degree day method, was developed. The method has been addressed for calculating the isolation related issues for buildings so far. But in this paper, it is utilized to predict the theoretical maximum power production of the gas turbines in various climates for the first time. The results indicated that the difference of annual energy production capacity between the best and the last province options was calculated to be 7500 MWh approximately.

An Integrated Fuzzy Multi-criteria Approach for Evaluation of Energy Resources: A Case Study of Turkey

The energy consumption of the world has been increasing in a consistent trend. This increment is faster than overall energy supply. The construction of additional power plants is essential to keep up with meeting the growing total energy demand. However, the effects of these power plants on social life and local economy should be considered during the planning stage. In this chapter, a Delphi method integrated fuzzy multi-criteria decision-making methodology is proposed to evaluate and to compare power plant alternatives. This approach is based on the fuzzy logarithmic least squares method and performs good solutions under implicit information conditions. The methodology is tested in a case study to find the optimal plant type for Turkey. The numerical results together with conducted sensitivity analysis provide insights on the strength and feasibility of the proposed method.

Exergetic Analysis of a Gas Turbine with Inlet Air Cooling System

The climate condition affects the performance of the combined-cycle power plants. The efficiency of the combined cycle is significantly influenced by the temperature, pressure and humidity of the air. When the ambient air temperature increases, the density of the air decreases, and it leads to a reduction of power generated by the gas turbine. In this work, the energy and exergy analysis of a commercial gas turbine, with inlet air cooling, was performed. The effects of fogging system on gas-turbine performance studied. For this aim, the energy and exergy balances were obtained for each piece of equipment. Calculations have been made for four different cases for the regarded gas turbine system. Furthermore, exergetic efficiency, exergy destruction rates and improvement potentials were obtained, and the results of the study demonstrated graphically. It is concluded that the net power output of the gas turbine system increased at lower inlet temperatures and exergy destruction rates occurred from highest to lowest as combustion chamber (CC), gas turbine (GT) and air compressor (AC), respectively.

A Design Approach for Cooling Gas Turbine Intake Air with Solar-Assisted Absorption Cooling Cycle

The Republic of Turkey’s current energy policy encourages households, industries, and energy production facilities to be energy wise. In this chapter, the Bursa Ovaakca power plant, which is one of the largest power plants of Turkey, was investigated with regard to boosting production. The scope of this chapter was to design a solar-assisted absorption cooling plant for cooling the intake air of gas turbines. The aim of this chapter is to achieve an efficiency augmentation in gas turbines through a solar energy-assisted absorption cooling system. The COP of the designed absorption cooling system has been calculated to be 0.75, and the utilization factor is 28.6.

Design of an Inlet Air-Cooling System for a Gas Turbine Power Plant

In this study, the gas turbine cycle of Ovaakca power plant that is located in Bursa, Turkey was analysed. The aim of the study is to determine the use of an ice thermal energy storage system for the 239 MW-powered gas turbine cycle. The performance of the system was investigated for full-load conditions. Energy and exergy analysis were performed by using last decade’s meteorological weather data. The results showed that utilizing an ice thermal energy storage system can boost the net power up to 12.60%.

Mühendislik Disiplinleri İçin Bilimsel Makale Yazım Esasları

Bilimsel makaleler, yeni bir konseptin tanitilmasi, yerel veya yaygin bir yenilik icermesi gerekliligi, yeni bir metodun kullanilmasi, bilinen bir metodun yeni bir alana uygulanmasi veya bunlar gibi cesitli inovasyon ozellikleri sayesinde, bilimin bu gunku seviyeye ulasmasina katki saglayan en onemli faktorlerden birisidir. Son dort yuz yil icerisinde surekli gelisen bilimsel yayincilikta artik rastgele yazilmis, duzensiz makalelerin yayinlanma sansi yoktur. Bu calismada, bilimsel calismalarin kapatma raporu niteliginde olan bilimsel makalelerin kabul edilme sanslarini arttirmak uzere, yayinin nasil yazilmasi gerektigi ile ilgili anahtar bilgiler verilmektedir. Bu kapsamda ulusal ve uluslar arasi literatur taranarak, bilimsel makale yazimi ile ilgili ulkemizde ve dunyada kabul goren TUBITAK gibi kurumlarin ve dergi editorlerinin tavsiyeleri derlenerek, kilavuz niteligindeki bu calisma ortaya konmustur. Calismada uluslararasi literaturde en cok kabul goren sekliyle bilimsel makalenin kisimlari tanitilmis ve her bir kisimda nelere yer verilmesi gerektigi mumkun oldugu kadar basite indirgenerek orneklerle anlatilmistir. Bu calismada bilimsel arastirma etigi, hazirlik asamalari gibi yazim oncesi ve dergi secimi, uygun formatta sunum gibi yazim sonrasi asamalar kapsam disi birakilmistir.