Assessment of modulated hot wire method for thermophysical characterization of fluid and solid matrices charged with (nano)particle inclusions

Recently we reported on simultaneous thermal conductivity k and thermal diffusivity a measurement of liquids and in particular of nanofluids in a configuration using an ac excited hot wire combined with lock-in detection of the third harmonic (3ω method) [1]. The conductive wire is used as both heater and sensor. The requirements for the asymptotic validity of the line heat source model are fulfilled at low modulation frequencies below a few Hz. The study of the relative sensitivity of signal amplitude and phase to changes in k and a indicates that there is an optimum frequency range for accurate and stable results. We extend by up to two decades the feasible frequency range for 3ω measurements by considering various more elaborate models for the heat transfer between the wire and the fluid. Finally we show that the same ac hot wire method can be applied to soft solid, composite materials. We measured the k enhancement of a poly(ethylene vinyl acetate) EVA polymer matrix charged with various fractions of graphite

Pizza ve milföy hamurlarının özgül ısılarının belirlenmesi

Today, various types of bread are being made around the globe, depending upon different Technologies. As with in the world, different types of bread are consumed in Turkey. The loaf bread is a common type but the consumption of local breads are also fairly common. Flat breads are widely consumed in the Middle East and North Africa as well as in our country. Flat breads differ from pan bread called western- type bread having high specific volume. Tırnaklı and Acık ekmek are recognized as flat type bread and widely consumed in Sanliurfa province. In this study, recent information about traditional production methods of Tırnaklı and Acık ekmek were summarized.Bu çalışmada milföy ve pizza hamurlarının özgül ısıları fark tarama kalorimetresi (DSC) kullanılarak -60 °C ile 100 °C sıcaklık aralığında deneysel olarak belirlenmiştir. Örneklerin donmuş durumdaki özgül ısı değerlerinin donmamış durumuna ait özgül ısı değerlerinden daha düşük olduğu ve sıcaklığın artmasıyla arttığı bulunmuştur. Donmamış durumda ise örneklerin özgül ısı değerlerinin sıcaklıkla artış gösterdiği saptanmıştır. Milföy hamurunun özgül ısı değerinin donmuş ve donmamış durumda pizza hamurunun özgül ısı değerinden daha düşük olduğu saptanmıştır. Ölçüm sonuçlarının literatürde bulunan değerlerle uyumlu olduğu görülmüştür