Suppression of natural convection heat transfer along a vertical flat plate with concavities

To clarify the effect of the suppression of natural heat transfer, the local heat transfer coefficients on a vertical cooled flat plate with circular grooves were measured by a multi‐type thermocouple method. Two flat plates with and without periodic circular grooves were tested in this experiment. The characteristics of heat transfer along the plate for both plates were compared. The local heat transfer coefficients on the periodic grooved plate became smaller than that of the flat plate. The flow pattern was changed when it passed over the grooves, and circulation was generated in the grooves in the downstream. As a result, the thickness of the thermal boundary layer on the grooved plate was more developed than the normal flat plate. © 2010 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.20294     

Five years operating experience of large scale distillation test plant made of carbon steel

The distillation test plant operated since April 14, 1972 during 94.2% of the work day has the capacity to treat 1,000 cu. meter/day of sea water, to produce 850t of fresh water of excellent quality, leaving 150t of concentrated brine containing 20% solid matter. Raw sea water was pretreated to prevent scale formation and corrosion of materials in distillation. Patents have been granted in Japan, USA, United Kingdom, West Germany, France, Italy, etc. (1).This method enables use of a base metal such as common steel for construction with the following advantages:Capital investment is cheaper.No galvanic corrosion arises.Mechanical structure is rigid.Contamination of poisonous heavy metals is avoidable.Upper limit of temperature is higher.Amount of raw sea water is smaller.Amount of exhaust brine is smaller.     

A study on the spray characteristics of a piezo pintle-type injector for DI gasoline engines

We studied the spray flow initiated from a piezo pintle-type injector for DI gasoline engines in an environment supplied by a constant volume vessel by means of laser diagnostics. To fully grasp the effects of the characteristic parameters, including designed spray angle, needle lift, injection pressure (P _inj ) and ambient pressure (P _b ), on the spray atomization and mixture preparation, particle image velocimetry (PIV) and phase Doppler anemometry (PDA) are used in the experiment, respectively. The gas perpendicularly enters into the outer periphery of the conical spray injected through the pintle-type injector activated by piezo, which creates two large-scale vortices: the vortex A and vortex B. The velocity standard deviation of the spray field is introduced to analyze the gas flow motion in the vicinity of nozzle. The droplet information of spray field is also recorded by PDA in variable boundary conditions. The time dividing method is used to study the droplet characteristics in four parts of spray. The injector with 98° designed spray angle has smaller droplet mean diameter (D10 and D32), due to a larger spray distribution. When the droplet velocity of the spray field is close to 0 m/s, the D10 and D32 hold at around 10 μm and 20 μm, respectively, in atmospheric pressure condition, which are about 20 μm and 40 μm, respectively, at ambient pressure of 1.1 MPa.     

XRD Studies on the conversion from several manganese oxides to β-manganese dioxide during acid digestion in MnSO4H2SO4 system

The wet method to change crystal structure from several manganese oxides to β-manganese dioxide, iso-structural with rutile, was reported.Manganese oxides such as Mn₂O₃ and Mn₃O₄ gave the same XRD profiles as an electrolytic MnO₂ (EMD) on boiling in dilute H₂SO₄ solution at 90–100°C for several hours and finally gave the XRD pattern of β-MnO₂ for a prolonged reaction period. Interesting finding was that several MnO₂s such as δ-MnO₂, α-MnO₂, EMD and heat-treated EMD could be converted into β-MnO₂ by using the proton-assisted rearrangement reaction in a boiling dilute H₂SO₄ solution containing Mn²⁺ ion at 90–110°C for several hours to several weeks depending on starting materials. The complex situations on classifying artificial manganese dioxides especially EMDs in terms of crystal structure are discussed.     

Characterization of the extracts and residues from CS2-N-methyl-2-pyrrolidinone mixed solvent extraction

The extracts and residues obtained by extraction of five bituminous coals with CS₂-N-methyl-2-pyrrolidinone mixed solvent (1:1 by volume) were characterized at room temperature. The extraction yields were 31.1–63.0% (daf) and the extracts were fractionated into acetone soluble (AS), acetone insoluble-pyridine soluble (PS) and pyridine insoluble-mixed solvent soluble (MS) fractions. The MS fraction, which was the heaviest fraction examined, had higher values of % oxygen, f_a, molecular weight and spin concentration than the corresponding AS and PS fractions, but a similar degree of aromatic condensation. The quantities of volatile matter (daf) in the residues were similar or slightly less than those in the extracts.