University of Tabriz

About: University of Tabriz is a education organization based out in Tabriz, Iran. It is known for research contribution in the topics: Population & Nanocomposite. The organization has 12141 authors who have published 20976 publications receiving 313982 citations.

A thermodynamic study of waste heat recovery from GT-MHR using organic Rankine cycles

Abstract: This paper presents an investigation on the utilization of waste heat from a gas turbine-modular helium reactor (GT-MHR) using different arrangements of organic Rankine cycles (ORCs) for power production. The considered organic Rankine cycles were: simple organic Rankine cycle (SORC), ORC with internal heat exchanger (HORC) and regenerative organic Rankine cycle (RORC). The performances of the combined cycles were studied from the point of view of first and second-laws of thermodynamics. Individual models were developed for each component and the effects of some important parameters such as compressor pressure ratio, turbine inlet temperature, and evaporator and environment temperatures on the efficiencies and on the exergy destruction rate were studied. Finally the combined cycles were optimized thermodynamically using the EES (Engineering Equation Solver) software. Based on the identical operating conditions for the GT-MHR cycle, a comparison between the three combined cycles and a simple GT-MHR cycle is also were made. This comparison was also carried out from the point of view of economics. The GT-MHR/SORC combined cycle proved to be the best among all the cycles from the point of view of both thermodynamics and economics. The efficiency of this cycle was about 10% higher than that of GT-MHR alone.

Modified Pencil Lead as a New Fiber for Solid-Phase Microextraction

Abstract: The efficiency of modified pencil lead as a new fiber for solid-phase microextraction (SPME) has been investigated. Modified pencil lead fibers have been prepared by use of several activation processes, for example heating at 600 °C in the stream of inert gas (He), heating under reflux with concentrated H2SO4 , fusing with NaOH at 400 °C, and activation at 600 °C with water vapor for 60 min. The fibers were used for extraction of trace amounts of polycyclic aromatic hydrocarbons (PAH) from aqueous samples. Monitoring of extracted compounds and quantitative analysis of model samples were performed by capillary GC–FID. The results obtained prove the suitability of the proposed fibers for sampling organic compounds from water. Effects on extraction efficiency of factors such as temperature, salting out, stirring speed, and exposure time were studied. Under optimum conditions and using one fiber for extraction of naphthalene as a typical compound, a relative standard deviation of 5.3% (n=7) was achieved. The calibration plot was linear in the range 50–10,000 pg mL−1 (r=0.9997) and the detection limit was 25 pg mL−1 (S/N=3). This fiber is very stable at high temperature, inexpensive, and can be prepared simply.

Extended Topology for a Boost DC–DC Converter

Abstract: In this paper, a new structure for a nonisolated boost dc–dc converter is proposed. The proposed converter generates higher voltage gain than some conventional nonisolated boost dc–dc converters. In this paper, the voltage and current equations of the elements and voltage gain in continuous conduction mode and discontinuous conduction mode are extracted. Then, the critical inductance converter is extracted and the current stresses in the switches are calculated. To achieve high voltage gain, a generalized structure based on the proposed structure generates for dc–dc converters. Meanwhile, the root mean square current relations of devices are obtained for an extended structure. Finally, the results of PSCAD/EMTDC software and laboratory prototype are used to reconfirm theoretical concept.