Interaction between effects of ambient parameters and those of other important parameters on electrospinning of PEI/NMP solution

By electrospinning method, fibers are produced with diameters ranging from hundred nanometers up to a few micrometers. In this study, the influence of ambient temperature and relative humidity on the morphology of electrospun polyetherimide (PEI) fibers at varying electrospinning parameters such as solution concentration, applied voltage, and tip-to-collector distance was investigated. 1-methyl-2-pyrrolidinone was used as a solvent for PEI. Morphology and diameter of electrospun PEI fibers were examined by field-emission scanning electron microscopy. It was seen that 20 wt% of the PEI solution shows the most increase in average diameters from 30 to 70% RH at 15, 25, and 35 °C. It was also seen that 20 wt% of the PEI solution shows the most decrease in average diameters from 15 to 35 °C at each of the RH values. An interesting result was observed for 12 cm of tip-to-collector distance. The average fiber diameters firstly decreased from 15 to 25 °C, and then increased from 25 to 35 °C for all of the RH values. © 2014, The Textile Institute

Investigation of effects of stone washing on performance for denim fabrics [Taş yikamanin denim kumaş performansi üzerindeki etkilerinin araştirilmasi]

Stone wash is one of the most frequently used washing applications for denim fabrics. The purpose of the stone washing process is to give the denim products an effect that has been worn for a long time and washed many times. In this study, the effects of stone wash applications on denim fabric properties are examined. A selected denim fabric was washed with different amounts of stone, temperature and duration during washing. In the research conducted, the results obtained by applying the test methods used in the performance evaluation of textile fabrics were analyzed by statistical methods in order to examine the effect of the washings on the fabrics. By evaluating the experimental study results; It has been found that while the stone washing process time, amount of stone and temperature of washing bath has effects on the fabric weight, width, shrinkage after washing, skew movement, tensile and tear strength properties

Investigation of dimensional parameters of single jersey fabrics and prediction of dimensional variation [Süprem örme kumaşlarin boyutsal parametrelerinin incelenmesi ve boyutsal değişiminin tahmin edilmesi]

In the current study, dimensional parameter values of single jersey fabrics produced by ring, compact and open-end rotor yarns with different tightness were investigated. In order to predict the dimensional variations, some equations were established and produced fabrics were subjected to full relaxation process. As a result of these processes, course count per cm, wale count per cm and loop length of the fabrics were measured and dimensional parameters were calculated. As a result of the study conducted, it is figured out that dimensional parameters of fabrics can change with respect to yarn types. Since the values calculated are in the range of predetermined values by the researchers, it was determined that fabrics are completed full relaxation after 5 washing operations. Dimensional change in course and wale directions after full relaxation operation were predicted by employing SPSS statistical program by using calculated dimensional parameter values

Second-law and experimental analysis of a cross-flow heat exchanger

This article presents a cross-flow plate-type heat exchanger that has been studied and manufactured in laboratory conditions because of its effective use in waste heat recovery systems. This new heat exchanger was tested with an applicable experimental setup, considering temperatures, velocity of the air, and the pressure losses occurring in the system. These variables were measured and the efficiency of the system was determined. The irreversibility of the heat exchanger was taken into consideration, while the design of the heat exchanger was such that the minimum entropy generation number was analyzed with respect to the second law of thermodynamics in the cross-flow heat exchanger. The minimum entropy generation number depends on the parameters called the optimum flow path length and dimensionless mass velocity. Variations of the entropy generation number with these parameters are analyzed. © 1999 Taylor & Francis Group, LLC