Heat transfer and pressure drop performance of Al2O3/water and TiO2/water nanofluids in tube fitted with simple or modified spiral tape inserts

The present paper deals with the forced convection and pressure drop of Al2O3/water and TiO2/water nanofluids with the presence of inserts in a circular tube. The constant heat flux is maintained around the copper tube with the help of a nichrome wire heater. Two types of inserts are used; simple and modified spiral tape inserts. The modified spiral tape is consisting of zig-zag cuts having notches (or grooves) and projected parts. The Nusselt number, friction factor and thermal performance factor are calculated for different cases: (1) tube with distilled water, (2) tube with distilled water and inserts and (3) tube with nanofluids and inserts. The empirical correlations are developed for all these cases. For Al2O3/water nanofluids, the Nu values decreases with the increase in concentrations, whereas for TiO2/water nanofluids, the Nu values has highest at 0.05% concentration, then there is a decreasing order with the concentrations of 0.075% and 0.1%. it is observed that modified spiral tape inserts with twist ratios of 3.04 and 4.35 effectively enhance the heat transfer without extra penalty of pumping power.

Design and simulation of components of vacuum forming machine using household vacuum cleaner

Plastic products ranging from toothbrushes to smartphones are an inseparable commodity in daily human life and their impact cannot be underestimated. This paper aims to design and simulate the vacuum forming process using readily available materials in context of Nepal. Vacuum forming process is a thermoforming process where the heated plastic sheet derives the shape of the mold through the application of vacuum and is used to make packaging products and other household products. Simulations were done to find out the optimum distance between the plastic sheet and the heater, arrangement of the wire in the heater, load bearing capacity of the design and the flow of vacuum in the arrangement. Nichrome wire coiled as heater coil is used as the heating material and laid in a spiral path with the plastic sheet 35mm below provided the best heating results and 1800W vacuum cleaner provided the necessary pressure of 85-90kPa and velocities of 100- 115m/s while the steel posts provided adequate strength.

On-Line Sorbentless Cryogenic Needle Trap and GC–FID Method for the Extraction and Analysis of Trace Volatile Organic Compounds from Soil Samples

In this study, an automated sorbentless cryogenic needle trap device (ASCNTD) coupled with a gas chromatograph (GC) was developed with the aim of sampling, pre-concentration and determination of volatile organic compounds (VOCs) from soil sample. This paper describes optimization of relevant parameters, performance evaluation and an illustrative application of ASCNTD. The ASCNTD system consists of a 5 cm stainless steel needle passed through a hollow ceramic rod which is coiled with resistive nichrome wire. The set is placed in a PVC (Polyvinyl chloride) chamber through which liquid nitrogen can flow. The headspace components are circulated with a pump to pass through the needle, and this results in freeze-trapping of the VOCs on the inner surface of the needle. When extraction is completed, the analytes trapped in the inner wall of the needle were thermally desorbed and swept by the carrier gas into the GC capillary column. The parameters being effective on the extraction processes, namely headspace flow rate, the temperature and time of extraction and desorption were optimized and evaluated. The developed technique was compared to the headspace solid-phase microextraction method for the analysis of soil samples containing BTEX (Benzene, Toluene, Ethylbenzene and Xylene). The relative standard deviation values are below 8% and detection limits as low as 1.2 ng g−1 were obtained for BTEX by ASCNTD.

Study of perspective methods for pasteurization of milk for farming

The article considers an experimental actinator using simultaneous exposure of a thin layer of milk to the flow of infrared and ultraviolet rays. The actinator consists of a vertical cylindrical body inside which a cylinder is coaxially located, an IR heater made of transparent quartz glass and wound spirally (of nichrome wire) located on its upper part of the former of a thin layer of milk in the form of a hollow ball connected to the working cylinder in the bottom parts of the drive of the finished product in the form of a truncated cone and a nozzle for removal of the finished product, a UV irradiation lamp, a cruciform liquid dispenser contained inside the forms a thin layer of milk, connected to it by a branch pipe for feeding the initial product, connected with it through a pipeline, a tap for adjusting the pressure and flow of milk, a pump and a tank for the initial product with a tap. The methodological basis for the calculation was used analytical development of heat exchange by radiation.

The Development of Physics Teaching Aids to Demonstrate the Intensity of Blackbody Radiation As a Function of Temperature

The purpose of this study was to develop teaching aids of blackbody radiation experiment and practicum devices based on modified free inquiry which are valid and reliable. This teaching aids was designed to demonstrate the relationship between the intensity of radiation and the absolute temperature of a blackbody (the law of Stefan-Boltzmann). The principle of this experiments is the amount of current will flow from the voltage source and enter to the black box. The black box will absorb and emit radiation. There is a nichrome wire inside the black box that will be light up, heat and emit radiation when electrically flowed. The emitted heat will be measured by temperature sensors using thermocouple located outside the black box. Based on experts and practitioner evaluation, the developed teaching aids of blackbody radiation experiment and practicum devices based on modified free inquiry were found to be valid, and reliable. The results of the experiment showed that the intensity of blackbody radiation was directly proportional to its temperature. This result is consistent with the law of Stefan-Boltzmann. Furthermore, the average of students’ perception of the developed teaching aids and practicum devices of blackbody radiation are 74.92% (good) and 80.17% (very good) respectively. This indicates that the teaching aids and practicum devices that have been developed can be used to demonstrate and prove the modern physics concepts related to blackbody radiation.Keywords: Teaching Aids, Stefan-Boltzmann’s law, Blackbody RadiationPenelitian ini bertujuan untuk mengembangan alat peraga eksperimen radiasi benda hitam dan perangkat praktikum fisika berbasis modified free inquiry yang valid dan reliabel. Alat peraga tersebut dirancang untuk mendemonstrasikan hubungan antara intensitas radiasi benda hitam dengan suhu mutlak yang dipancarkannya (Hukum Stefan-Boltzmann). Prinsip kerja dari alat peraga tersebut adalah arus akan mengalir dari sumber tegangan dan masuk ke dalam kotak lubang hitam. Kotak ini berfungsi untuk menyerap dan memancarkan radiasi. Di dalam kotak terdapat kawat nicrom yang akan menyala dan memancarkan radiasi ketika dialiri arus listrik. Panas yang dipancarkan akan diukur oleh termokopel radiasi yang berada di luar kotak. Berdasarkan penilaian validator, alat peraga eksperimen radiasi benda hitam dan perangkat praktikum fisika berbasis modified free inquiry yang telah dikembangkan dinyatakan valid dan reliabel. Hasil uji coba menunjukkan bahwa intensitas radiasi yang dipancarkan oleh benda hitam berbanding lurus dengan temperaturnya yang sesuai dengan hukum Stefan-Boltzmann. Selanjutnya, rata-rata persepsi praktikan terhadap alat peraga eksperimen radiasi benda hitam dan perangkat praktikum yang telah dikembangkan secara berturut-turut adalah 74,92% (baik) dan 80,17% (sangat baik). Hal ini mengindikasikan bahwa alat peraga dan perangkat praktikum yang telah dikembangkan dapat digunakan untuk mendemonstrasikan dan membuktikan konsep-konsep fisika modern yang berhubungan dengan radiasi benda hitam.Kata kunci: Alat Peraga, Hukum Stefan-Boltzmann, Radiasi Benda Hitam

Effects of Hydrogen-Air Gas Mixture Volume and Initiation Type and Energy on the Propagation of a Spherical Flame Front

The investigation considered a spherical flame front propagating in free space filled with a hydrogen-air mixture containing 15 % hydrogen. The experiments were conducted inside latex shells. We initiated combustion in the centre of the volume, using either a 1 mJ spark or a nichrome wire explosion releasing 5 J of energy. In the case of the 7 m3 and larger shells, we recorded video data on the flame front using an InfraTec ImageIR 8320 infrared camera featuring a 2.0--5.7 μm spectral ranges and a rate of 300 frames per second. In the case of the 0.003 m3 and smaller shells, we visualised the processes by means of an IAB-451 schlieren system. We recorded these images using a Videosprint G/2 visible-wavelength camera at a rate of 1000 frames per second. We identified the differences in flame front acceleration dynamics for the same combustible mixture composition and flame initiation energy. We found that the distribution function specifics concerning the pre-exponential factors in the power law of flame front acceleration indicate that individual random perturbations have a considerable effect at the initial stage of quasi-spherical flame front formation. We compared flame front propagation for the cases when the initiation energy was 1 mJ and 5 J respectively and determined that the initiation energy also affects the process

Impact of Holder Materials on the Heating and Explosive Breakup of Two-Component Droplets

The heating of two-component droplets and the following explosive breakup of those droplets have been extensively studied over the most recent years. These processes are of high interest, since they can significantly improve the performance of many technologies in fuel ignition, thermal and flame liquid treatment, heat carriers based on flue gases, vapors and water droplets, etc. Research throughout the world involves various schemes of droplet heating and supply (or, less frequently, injection) to heating chambers. The most popular scheme features the introduction of a two-component or multi-component droplet onto a holder into the heating chamber. In this research, we study how holder materials affect the conditions and integral characteristics of droplet heating and explosive breakup: heating time until boiling temperature; minimum temperature sufficient for droplet breakup; number and size of fragments in the resulting droplet aerosol, etc. Experiments involve droplets that are produced from flammable (oil) and non-flammable (water) components with significantly different thermophysical and optical properties, as well as boiling temperature and heat of vaporization. The most popular elements with the scientific community, such as ceramic, steel, aluminum, copper, and phosphorus rods, as well as a nichrome wire, serve as holders. We establish the roles of energy inflow from a holder to a droplet, and energy outflow in the opposite direction. We compare the holder results with a supporting thermocouple, recording the drop temperature under a heat transfer provided at 350°C. Finally, we forecast the conditions that are required for a significant improvement in the performance of thermal and flame water treatment through the explosive breakup of two-component droplets.