Results of experimental studies and the modelling of heating and evaporation of monodisperse ethanol and acetone droplets in two regimes are presented. Firstly, pure heating and evaporation of droplets in a flow of air of prescribed temperature are considered. Secondly, droplet heating and evaporation in a flame produced by previously injected combusting droplets are studied. The phase Doppler anemometry technique is used for droplet velocity and size measurements. Two-colour laser induced fluorescence thermometry is used to estimate droplet temperatures. The experiments have been performed for various distances between droplets and various initial droplet radii and velocities. The experimental data have been compared with the results of modelling, based on given gas temperatures, measured by coherent anti-stokes Raman spectroscopy, and Nusselt and Sherwood numbers calculated using measured values of droplet relative velocities. When estimating the latter numbers the finite distance between droplets was taken into account. The model is based on the assumption that droplets are spherically symmetrical, but takes into account the radial distribution of temperature inside droplets. It is pointed out that for relatively small droplets (initial radii about 65 lm) the experimentally measured droplet temperatures are close to the predicted average droplet temperatures, while for larger droplets (initial radii about 120 lm) the experimentally measured droplet temperatures are close to the temperatures predicted at the centre of the droplets.

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The modified WAVE droplet breakup model, taking into account the transient processes during spray injection, the Effective Thermal Conductivity (ETC) liquid phase model, the gas phase model suggested by Abramzon and Sirignano, and the customised version of the Shell autoignition model have been implemented into the KIVA 2 CFD code. The observed Diesel spray tip penetration and Sauter Mean Radii show much better agreement with the prediction of the modified WAVE model compared with other droplet breakup models. The difference in the autoignition delay times predicted using the Infinite Thermal Conductivity (ITC) and ETC models is important for practical computations

a b s t r a c tThe results of numerical and experimental studies of heating and evaporation of monodisperse acetone, ethanol, 3-pentanone, n-heptane, n-decane and n-dodecane droplets in an ambient air of fixed temperature and atmospheric pressure are reported. The numerical model took into account the finite thermal conductivity of droplets and recirculation inside them based on the effective thermal conductivity model and the analytical solution to the heat conduction equation inside droplets. The effects of interaction between droplets are taken into account based on the experimentally determined corrections to Nusselt and Sherwood numbers. It is pointed out that the interactions between droplets lead to noticeable reduction of their heating in the case of ethanol, 3-pentanone, n-heptane, n-decane and n-dodecane droplets, and reduction of their cooling in the case of acetone. Although the trends of experimentally observed droplet temperatures and radii are the same as predicted by the model taking into account the interaction between droplets, the actual values of the predicted droplet temperatures can differ from the observed ones by up to about 8 K, and the actual values of the predicted droplet radii can differ from the observed ones by up to about 2%. It is concluded that the effective thermal conductivity model, based on the analytical solution to the heat conduction equation inside droplets, can predict the observed average temperature of droplets with possible errors not exceeding several K, and observed droplet radii with possible errors not exceeding 2% in most cases. These results allow us to recommend the implementation of this model into CFD codes and to use it for multidimensional modelling of spray heating and evaporation based on these codes.

Type screw water turbine is a type of water turbine which has the potential for small scale power plants, where water turbine screw type is suitable for rivers in parts of Indonesia because the operation of the turbine require only a low head turbine. With the potential of irrigation water streams at the rate of 0.3302 m3/s in Banjaran village allows the installation of the turbines type screw. In the process of designing a water turbine type screw to be optimized turbine screw to determine the value of the ratio d/D, and then calculating mechanically to determine the dimensions of the turbine blades, the turbine shaft, the transmission system (gears, pulleys and belt) as well as the power that can be produced by the turbines, by using a head of 1.05 meters. The results of this research are the technical specifications of the turbine screw with the design power of 2678.35 Watt. Performance test of the turbine was carried out in Nagrak village of Ciherang irrigation canals on Cangkuang Banjaran sub district. With variable discharge, measuring the speed of rotation of the shaft generator, the voltage and current that is produced as well as the efficiency of the turbine. From the results of testing gained 17.82 % efficiency, power turbine 531.84 Watts at discharge 0,277 m3/s.Keywords: Turbine, Head, Microhydro, OptimazedABSTRAKTurbin air tipe ulir adalah salah satu tipe turbin air yang berpotensi untuk pembangkit listrik skala kecil yang ramah lingkungan, dimana turbin air tipe ulir sangat cocok untuk sungai-sungai di wilayah Indonesia karena pengoperasian turbin ini hanya memerlukan head turbin yang rendah. Melihat potensi air aliran sungai irigasi dengan debit 0,3302 m3/s yang berada di Desa Banjaran memungkinkan pemasangan turbin tipe ulir. Pada proses perancangan turbin air tipe ulir dilakukan optimasi turbin screw dengan menentukan nilai perbandingan d/D, lalu melakukan perhitungan mekanikal untuk menentukan dimensi dari sudu turbin, poros turbin, sistem transmisi (roda gigi, puli dan belt) juga daya yang mampu dihasilkan turbin, dengan head 1,05 meter. Hasil dari penelitian ini berupa spesifikasi teknis turbin ulir dengan daya hasil rancangan sebesar 2678,35 Watt dan gambar 2 dimensi serta 3 dimensi turbin ulir hasil rancangan. Hasil perancangan kemudian direalisasikan. Untuk mengetahui kinerja turbin dilakukan pengujian yang dilaksanakan di saluran Irigasi Ciherang Desa Nagrak Kecamatan Cangkuang Banjaran. Dengan variabel ukur yaitu debit, kecepatan putaran poros generator, voltase dan arus yang dihasilkan serta efisiensi turbin. Dari hasil pengujian didapat efisiensi 17.82 %, Daya turbin 531.84 Watt pada debit 0,277 m3/s.Kata kunci: Turbin, Head, Mikrohidro, Optimasi