Fluidized tube heat exchanger

The presence of solid particles in a heat exchanger is important in keeping the surface clean, thus having a beneficial effect on heat transfer. Solids circulation in the system can be provided by means of a recycle tube mounted in the central core of the heat exchanger. In this study a pilot scale fluidized tube heat exchanger system which consists of six fluidization tubes together with the centrally located recycling tube was constructed and pressure drop, liquid–wall and solid–wall friction forces and the effects of the amount of solids introduced to the system on heat transfer were investigated. Experimental results indicate that although the recycle tube causes an approximately 35% decrease in the heat transfer coefficient when no solid is used, the presence of the solids in the system increases the heat transfer coefficient by about 45% above that of the solids‐free system. © 1999 Society of Chemical Industry     

Procedure to obtain higher than 14% efficient thin film CdS/CdTe solar cells activated with HCF2Cl gas

This work reports a process used to obtain CdS/CdTe thin film solar cells with high efficiencies between 14% and 14.6%. The procedure consists of sequentially depositing by RF sputtering and close space sublimation (CSS) of several layers onto a glass substrate, configured as glass/ITO/ZnO/CdS/CdTe/Cu/Mo. The CdTe layer was deposited by CSS at low substrate temperature (500 °C) under Ar–O₂ atmosphere and the activation process is performed with a mixture of Freon gas (HCF₂Cl) and other gases.     

Car-borne survey of natural background gamma dose rate in Çanakkale region, Turkey

Natural background gamma radiation was measured along roads in the environs of ?anakkale region by using a car-borne spectrometer system with a plastic gamma radiation detector. In addition, activity concentrations of 23?U, 22?Ra, 232Th and ??K in soil samples from the ?anakkale region were determined by using a gamma spectrometer with an HPGe detector. A total of 92,856 data of the background gamma dose rate were collected for the ?anakkale region. The background gamma dose rate of the ?anakkale region was mapped using ArcGIS software, applying the geostatistical inverse distance-weighted method. The average and population-weighted average of the gamma dose are 55.4 and 40.6 nGy h?1, respectively. The corresponding average annual effective dose to the public ranged from 26.6 to 96.8 μSv.     

Experimental and three-dimensional global-local finite element analysis of a composite component including degradation process at the interfaces

A specimen is studied in order to analyse the stringer runout effect in a specific design. An experimental test was carried out in several stages until specimen collapse, allowing the damaged regions and their characteristic geometric dimensions to be identified by ultrasound inspections. Several numerical analyses based on finite element method of the component were performed using the commercial software ABAQUS. These numerical analyses aimed to study in detail the onset and propagation of damage in the skin-stringer joint during the load procedure. Due to the high computational cost that this kind of procedure usually requires, a global–local approach was performed, comparing the two techniques offered by the software ABAQUS: Submodeling and Shell-to-Solid Coupling. Shell element typology was used in both cases for the global model. In order to estimate the extension of the critical zone in the specimen, the adhesive layer was modeled by means of solid elements. With reference to the local analysis, laminate continuum elements were selected to discretize the skin and the stringer, whereas the adhesive was represented by interface cohesive elements to take the damage evolution into account. A final correlation was carried out between numerical predictions and experimental results of the damaged regions in the component at several load levels.     

Energetic and exergetic performance evaluation of the quadruple-effect evaporator unit in tomato paste production

Quadruple-effect evaporator units are commonly used in food focus area in sector is evaporative unit. It consumes about 60% of total energy input. The present study evaluates the performance of quadruple-effect evaporator unit (QEEU) by using exergy analysis based on actual operational data. A tomato paste factory is chosen for the analysis. The highest exergy destruction/loss occurs in the first effect with 158.2 kW, 52.7% of exergy input in first effect. Steam temperature should be decreased in order to decrease exergy destruction in first effect. Also, third effect achieves the highest exergy efficiency with 93.3%. Exergetic improvement potential of each effect varies between 0.3 kW and 83.6 kW. The highest and lowest exergetic improvement potential occurs in first and third effect of QEEU system, respectively. Exergetic improvement potential is equals to 52.80%, 11.10%, 6.73% and 69.8% of exergy loss/destruction from the first effect to the last effect, respectively. Total exergetic improvement potential is achieved as 128 kW (55% of total exergy loss/destruction) in QEEU system. It is expected that analyses result provide important information for designer and/or resources of multiple effect evaporator unit.     

Anatomical basis for cell transplantation into mouse seminiferous tubules

Cell transplantation into the seminiferous tubules is a useful technique for the study of physiological and pathological conditions affecting the testis. However, the precise three-dimensional organization and, particularly, the complex connectivity of the seminiferous network have not yet been thoroughly characterized. To date, the technical approaches to address these issues have included manual dissection under the stereomicroscope, reconstruction of histological serial sections, and injection of contrast dyes, but all of them have yielded only partial information. Here, using an approach based on the microinjection of a self-polymerizing resin followed by chemical digestion of the surrounding soft tissues, we reveal fine details of the seminiferous tubule scaffold and its connections. These replicas of the testis seminiferous network were studied by scanning electron microscopy. The present results not only establish a morphological basis for more precise microinjection into the mouse seminiferous tubules but also enable a more profound investigation of physiological and embryological features of the testis.     

Immobilization of β-Glucosidase and Its Application for Enhancement of Aroma Precursors in Muscat Wine

Enzyme immobilization is becoming more widely practised in biotechnology because of the advantages that this method brings. In this study, commercial β-glucosidase for aroma released in winemaking was immobilized on diverse supports (alginate–chitin, chitosan–chitin) by using different methods. It was found that the most appropriate matrix was chitosan by adsorption and reticulation. The optimal immobilization conditions were pH 3.5, immobilization time 120 min, and concentration of cross-linker glutaraldehyde 0.25 %. Stability of the immobilized enzymes was assessed, which revealed a number of advantages, such as a lower enzyme dose required for immobilization (367 times lower than the free enzyme dose recommended by the manufacturer), high stability over time, and reusability. In vitro studies of cellobiose and in vivo studies of wine and aroma precursors isolated from grape must yielded similar outcomes with respect to enzyme hydrolysis of free and immobilized proteins.