Basic Aspects of Gas Turbine Heat Transfer

The use of gas turbines for power generation and electricity production in both single cycle and combined cycle plant operation is extensive and will continue to globally grow into the future. Due to its high power density and ability to convert gaseous and liquid fuel into mechanical work with very high thermodynamic efficiencies, significant efforts continue today to further increase both the power output and thermodynamic efficiencies of the gas turbine. In particular, the aerothermal design of gas turbine components has progressed at a rapid pace in the last decade with all gas turbine manufacturers, in order to achieve higher thermodynamic efficiencies. This has been achieved by using higher turbine inlet temperatures and pressures, advanced turbine aerodynamics and efficient cooling systems of turbine airofoils, and advanced high temperature alloys, metallic coatings, and ceramic thermal barrier coatings. In this chapter, issues related to the thermal design of gas turbine blades are highlighted and several heat transfer technologies are examined, such as convective cooling, impingement cooling, film cooling, and application of thermal barrier coatings. Typical methods for validating the thermal designs of gas turbine airofoils are also outlined

Organoaxial volvulus of descending colon: a case report

“Colonic volvulus” refers to the twisting of colon, which most commonly involves sigmoid colon causing obstruction, ischemia and gangrene. But very rarely segment of descending colon can be involved. This is a case of 42 year old male with vomiting, abdomen pain and distension since one day, showing organoaxial volvulus of descending colon loop with a twist of mesentery

Osjetljiva spektrofotometrijska metoda za određivanje sulfonamida u farmaceutskim pripravcima

A new, simple and sensitive spectrophotometric method for the determination of some sulfonamide drugs has been developed. The method is based on the diazotisation of sulfacetamide, sulfadiazine, sulfaguanidine, sulfamerazine, sulfamethazine, sulfamethoxazole and coupling with 8-hydroxyquinoline in alkaline media to yield red coloured products, with absorption maximum at 500 nm. The Beer’s law is obeyed from 0.17.0 µg mL1. The limits of quantification and limits of detection were 0.110.18 and 0.030.5 µg mL1, respectively. Intraday precision (RSD 0.10.5%) and accuracy (recovery 97.3100.8) of the developed method were evaluated. No interference was observed from common adjuvants. The method has been successfully applied to the assay of sulpha drug in the pharmaceutical formulations.U radu je opisana nova, jednostavna i osjetljiva spektrofotometrijska metoda za određivanje sulfonamida. Metoda se temelji na prevođenju sulfacetamida, sulfadiazina, sulfagvanidina, sulfamerazina, sulfometazina i sulfametoksazola u diazoderivate koji kondenzacijom s 8-hidroksikinolinom u alkalnom mediju daju crveno obojene produkte s maksimumom apsorpcije pri 500 nm. Beerov zakon vrijedi u koncentracijskom rasponu 0,17,0 µg mL1. Granice kvantifikacije i granice detekcije su 0,11-0,18, odnosno 0,03-0,05 µg mL-1. Za predloženu metodu procijenjene su intermedirska preciznost (RSD 0.1-0,5%) i točnost (analitički povrat 97,3-100,8). Uobičanjene pomoćne tvari u tabletama ne interferiraju tijekom određivanja. Metoda je uspješno primijenjena za analizu sulfonamida u farmaceutskim pripravcima

Experimental investigation of sequential narrow impingement channels for turbine cooling

Sequentially stacked impingement channels allow for a more effective use of the cooling fluid and can limit the heat transfer reduction due to the crossflow when the number of jets increases. In this paper, sequential impingement channels are experimentally investigated using the transient liquid crystal technique. Twelve configurations are tested: the baseline consists in a double rectangular channel with 5 jets per channel; other configurations feature different number of jets, variations of the jet-to-jet spacing and of the transition zone length, reduction of the cross-section in the transition zone and addition of a bypass between the channels. Results show that heat transfer coefficients (HTC) in the 2nd channel are similar to the 1st, and that the cross-section reduction in the transition zone allows for an increase of the HTC in this critical zone with only a moderate increase of pressure losses

Heat Transfer Enhancement in a Double Sequential Impingement Channel

Sequential impingement channels can reduce the adverse effect of crossflow in narrow impingement channels, as well as increase the cooling efficiency. In this work, sequential impingement channels are experimentally investigated using the transient liquid crystal technique to assess their thermal performances. A low heat transfer region is identified in the downstream part of the first channel where the flow is discharged into the second plenum. Various means of increasing the heat transfer at this location are investigated. Ribs on the target plate allow for an increase of the average heat transfer coefficient with small losses in pressure. Reducing the channel cross-section increases the mean flow velocity and, combined with the ribs, allows for a further increase of the heat transfer. Additionally, the geometrical changes of the channel caused by the addition of a ramp with a rounded corner, allow to decrease the pressure losses associated with the discharge into the second plenum, which is not optimal in the baseline configuration due to the sharp corner of the purge hole. Further reducing the cross-section to increase the heat transfer, however, increases the pressure losses due to the small open area in the transition zone

A unique presentation of 5-fluorouracil (5-FU) induced cerebral encephalopathy

5-Fluorouracil (5-FU), a commonly used antimetabolite and antineoplastic agent, has been approved for the treatment of various cancers. It is associated with systemic side-effects such as gastrointestinal problems, neutropenia. 5-FU-related encephalopathy is very rarely reported. Imaging with computed tomography (CT) and magnetic resonance imaging (MRI) plays a key role in diagnosing and monitoring the changes. Since the prognosis of cerebral involvement is usually good if recognized and treated in time, the reporting radiologist and treating physician should be familiar with them. We present a rare case of 5-FU-induced encephalopathy that was diagnosed based on her clinical and MRI findings and managed successfully

Simple, efficient and economical methods for isolation and estimation of novel isoflavone using RP-HPLC

The study was undertaken to develop a simplified procedure for the isolation of bioactive isoflavone from Iris kashmiriana, using a direct method of isolation, avoiding the use of chromatographic techniques. The compound was isolated by commercially viable procedure. The extraction of powdered drug (500 g) was done with petroleum ether (60–80) using a Soxhlet apparatus (24 h run). The petroleum ether extract (gums and resins 2.13 g) was obtained and the marc (400 g) was subjected to extraction with 95% methanol using a Soxhlet apparatus (24 h run). The methanolic extract (5 g) was subjected to successive fractionation with toluene, chloroform and ethyl acetate and n- butanol. On the basis of phytochemical analysis, the glycoside was present in n- butanol fraction. The n-butanol fraction (1.5 g) was taken in dried methanol, passed through activated animal charcoal and subjected to acid hydrolysis. The isoflavone (250 mg), was obtained after the usual process of separation. The purity of the compound was checked by analyzing TLC (Thin Layer chromatography) and melting point. Further, the chemical method was used to characterize the compound by shift reagents using UV spectroscopy. The quantitative estimation of isoflavone was done using RP-HPLC and was found to be 98.9% pure. • The “previously undescribed” isoflavone was isolated by modifying approach of solvent/solvent extraction, fractionation and acid hydrolysis. • The spectroscopic characterization was equaly done by IR, 1HNMR, 13CNMR, Mass spectrometry. • 98.9% purity was achieved using RP-HPLC with simple solvent (Methanol and Water 55: 45)

Isolation, characterization and identification of bioactive compounds from Herbal Medicines and Medicinal Plant Extracts by Fourier Transform Infrared Spectroscopy: A brief review

Herbal medicines are mostly used from thousands of years in primary health care of society and community of both developed and developing countries. It mainly includes whole plant, herbs, extracts, isolated compounds, polyherbal preparations, phytoformulations etc. Identification of bioactive compounds from phytomedicines plays a very important role in drug development and drug design process. The characterization of phytomedicines is very much essential in the identification of compounds. For the purpose of identification two methods, Spectroscopy and Chromatography play important role. Fourier Transform Infrared Spectroscopy (FTIR) is the widely used technique which is mainly used to identify functional groups in herbal medicines. Various scientific research articles published on extraction, isolation, characterization and identification of phytoconstituents from medicinal plants and other forms of herbal medicines is being reviewed in this article. We have mainly focused on the FTIR characterization and identification of phytochemicals from herbal medicines and are briefly presented in this review work. Our present review article concludes that the FTIR spectroscopy plays very much essential role in the identification and characterization of bioactive compounds from herbal medicines