Studies on Thermal Stratification Phenomenon in LH2 Storage Vessel

A study of convective heat transfer in a cryogenic storage vessel is carried out numerically and experimentally. A scaled down model study is performed using water as the model fluid in a rectangular glass tank heated from the sides. The convective flow and the resulting thermal stratification phenomenon in the rectangular tank are studied through flow visualization, temperature measurement, and corresponding numerical simulations. It is found that a vortex-like flow near the top surface leads to a well-mixed region there, below which the fluid is thermally stratified. In addition, in an attempt to simulate the actual conditions, a numerical study is performed on a cylindrical cavity filled with liquid hydrogen (LH₂) and heated from the sides. The results are compared with our model study with water, and the qualitative agreement is found to be good.     

Fabrication of highly expanded thermoplastic polyurethane foams using microcellular injection molding and gas‐laden pellets

Thermoplastic polyurethane (TPU) is one of the most widely used and versatile thermoplastic materials. TPU foams have been extensively applied in various industries including the furniture, automotive, sportswear, and packaging industries. In this study, two methods of producing highly expanded TPU injection molded foam were investigated: (1) microcellular injection molding (MIM) with N₂ as a blowing agent, and (2) a novel gas‐laden pellet/MIM combined process with N₂ and CO₂ as co‐blowing agents. Two designs of experiments (DOEs) were performed to learn the influences of key processing parameters and to optimize foam quality. By using N₂ and CO₂ as co‐blowing agents, a bulk density as low as 0.20 g/cm³ was successfully achieved with a hysteresis compression loss of 24.4%. POLYM. ENG. SCI., 55:2643–2652, 2015. © 2015 Society of Plastics Engineers     

Formation and Coalescence Stability of Emulsions Stabilized by Different Milk Proteins

The volume fraction of oil emulsified, surface area, droplet diameter, and coalescence rates of emulsions stabilized by different milk proteins were studied at protein concentrations of 0.25, 0.5, 1.0, and 2.0% (w/w); pH 4, 5, and 7; and ionic strengths 0.1 and 0.2. The emulsion activity index (EAI) and coalescence stability generally increased with increasing protein solubility and hydrophobicity. The volume fraction of oil emulsified decreased with increasing ionic strength. Coalescence stability correlated with droplet diameter for emulsions stabilized by α-lactalbumin, β-lactoglobulin, and sodium caseinate (r²=0.96). With the exception of β-lactoglobulin-stabilized emulsions, coalescence stability was largely unaffected by pH.     

Elemental analysis of rain－and fresh water by neutron activation analysis

Analysis of rain-and fresh water for trace constitutents is a mandatory part of environmental monitoring.This text gives a survey of neutron activation analysis(NAA) within the framework of current environmental water research programmes.based on the practice developed in co-operation with the Dutch Energy Research Centre at Petten(ECN).While the procedures reported in literature cover obout thirty five elements,our routine procedures of instrumental neutron activation analysis(INAA) is limited to ten to fifteen elements.THe use of some dedicated radiochemical separations(RNAA) adds another six,some of which are speciated as well.Current contributions of NAA to water analysis center on determination and speciation of anionic trace elements,notably Br.I,As,and Se,on the assay of some ultra traces like Ag,Au and Hg and on validation.     

A novel approach of manufacturing Nickel Wicks for loop heat pipes using Metal Injection Moulding (MIM)

Sintered nickel powder is proposed to be used as porous wicks in loop heat pipes used for space applications such as satellites and space crafts. In this work, the manufacturing procedure for tubular wicks through novel Metal Injection Moulding (MIM) route is discussed. Nickel powder, Polypropylene powder and thermoplastic binder are used to produce feedstock for injection moulding. Ideal sintering condition identified as 900°C and 60 minutes. Porosity, pore diameter of the wicks are evaluated by geometric measurements using an electronic weight measuring machine and a micrometer and extrusion flow Porosimeter, respectively. Permeability was calculated according to the Carmen–Kozeny equation. Experimental finding shows that porosity level of 55 vol%, average pore diameter of 2.6 μm, permeability of 1.94 × 10^???12 m² and roundness of 5% have been achieved in the porous wick. SEM investigation of pore structures shows the presence of large pores which leads to enhanced porosity and interconnected fine pore network responsible for generation of required capillary pumping pressure.     

Dielectric response of PLZT ceramics <Emphasis Type="Italic">x</Emphasis>/57/43 across ferroelectric–paraelectric phase transition

The dielectric properties of lead lanthanum zirconate titanate (PLZT) ceramics [Pb(Zr_0·57Ti_0·43)O₃ + x at% of La, x = 3, 5, 6, 10 and 12] have been measured in the frequency range 1 Hz–1 MHz using the vector impedance spectroscopy (VIS) at different temperatures. All the compositions show both non-dispersive and dispersive dielectric responses in different temperature regions. The non-dispersive region obeys the universal dielectric response. A low frequency (<1 kHz) relaxation phenomenon with a high value of distribution parameter ‘h’ (~0·4 to 0·6) has been observed in all the compositions around the temperature corresponding to the maximum dielectric constant (T _m). The activation energies as calculated from the relaxation and d.c. conduction processes are comparable. The ferroelectric phase transition is diffuse in nature and broadening of the peak increases with La content.     

Development of a Bridge Bumper to Protect Bridge Girders from Overheight Vehicle Impacts

Abstract:   Bridges with low clearance are vulnerable to collision with overheight vehicles. Collisions of overheight vehicles can cause fatalities and injuries to the drivers and passengers of the overheight vehicles, and damage to bridge girders. The repair of the damaged bridges can be costly and time consuming. This article investigates the feasibility of developing a bridge bumper that minimizes the physical injuries and the likelihood of fatalities and protects the structural elements of bridges by absorbing the impact energy. The article presents the results of small-scale impact experiments using the proposed bridge bumper with several options of energy-absorbing materials to protect a reinforced concrete beam. Finite element analyses are carried out to simulate the small-scale impact experiments. Optimization of the finite element model is conducted for the response quantities of interest with respect to the geometrical parameters and the material properties of the proposed bridge bumper. Such analysis can guide the design of an optimal bridge bumper that maximizes the energy dissipation and minimizes the damage to the bridge girder and the likelihood of fatalities and injuries. A possible full-scale implementation of the proposed bridge bumper is also described.     

Voltage-current characteristics and power relation in arc plasma in a transverse magnetic field †

The variation of current and the corresponding voltage across a mercury are plasma in a varying transverse magnetic field (0 to 3000 g) has been measured for various initial discharge currents. The current gradually decreases and the voltage across the arc increases with the increase of the magnetic field, the power consumed gradually increases and, attaining a maximum value at a certain value of the magnetic field which is different for different initial currents, gradually decreases with the further increase of the magnetic field. Assuming Beckman's expression (1948) for the axial field and the electron density distribution in a transverse magnetic field and Langmuir's expression (1925) for the current in the are plasma, the observed variation of current and voltage can be satisfactorily explained. A theoretical expression has been derived for the magnetic field at which the power consumed becomes a maximum, by assuming the above deductions and also taking into consideration the variation of electron temperature with magnetic field. The value of the magnetic field thus calculated agrees fairly well with the experimental results, especially for low values of initial currents, and the discrepancy for higher currents has been attributed to the limitations of the above deductions for higher values of H/P