Increase In Volumetric Concentration Research Articles

Numerical Investigation of the Pressure Drop Characteristics of Isothermal Ice Slurry Flow under Variable Ice Particle Diameter

Ice slurry is an advanced secondary refrigerant that has been attracting considerable attention for the past decade due to the growing concerns regarding energy shortage and environmental protection. To stimulate the potential applications of ice slurry, the corresponding pressure drop of this refrigerant must be comprehensively investigated. The flow of ice slurry is a complex phenomenon that is affected by various parameters, including flow velocity, ice particle size, and ice mass fraction. To predict the pressure drop of ice slurry flow in pipes, a mixture computational fluid dynamic model was adopted to simulate a two-phase flow without considering ice melting. The numerical calculations were performed on a wide range of six ice particle sizes (0.1, 0.3, 0.5, 0.75, 1, and 1.2 mm) and ice mass fraction ranging within 5%–20% in the laminar range of ice slurry flow. The numerical model was validated using experimental data. Results showed that the ice volumetric loading and flow velocity have a direct effect on pressure drop; it increases with the increase in volumetric concentration and flow velocity. The findings also confirmed that for constant ice mass fraction and flow velocity, the pressure drop is directly and inversely related to the particle and pipe diameters, respectively. Moreover, the rise in pressure drop is more significant for large ice particle diameter in comparison to smaller size ice particles at high values of ice concentration and flow velocity.

Assessing the effect of fillers on LVE properties of asphalt mastics at intermediate temperatures

This study aims at examining the performance of asphalt mastics in the Linear Viscoelastic (LVE) domain incorporating three Indian and three Austrian fillers. The various physical, morphological, and chemical properties of the fillers were analyzed with the help of respective characterization tests. In addition to the particle size distribution curve and fineness modulus, a new parameter called Filler Grain Coefficient (FGC) has been introduced in this study to quantify the distribution of particles in the system. This paper also attempts to find a correlation between various physical parameters. There are two variables i.e., $$\left| {G^{*} } \right|_{\text{LVE}}$$ and $$\left| {G^{*} } \right|_{\text{ratio}}$$ in order to quantify the Linear Viscoelastic complex modulus. The effects of both volume and surface area of fillers have been manifested by three ratios denoted as V/FM, V/FGC, and V/RV. To compare the outcome of the study, the Strategic Highway Research Program Linear Viscoelastic strain criteria is also included, which examines the applicability of the criteria to the asphalt mastics. The research incorporates a wide range of fillers with variable properties, as confirmed by the test results. Filler parameters Rigden Voids and Filler Grain Coefficient were found to be strongly correlated with almost all physical properties. On the grounds of variation in LVEM with volume concentration of filler, the highest rank can be attributed to Red Mud and LimeStone, respectively, followed by other fillers with Marble Dust being the lowest. The reinforcing effect of fillers and higher surface area contributed to the exponential increase in $$\left| {G^{*} } \right|_{\text{LVE}}$$ , with an increase in volumetric concentration. The variation of both variables: $$\left| {G^{*} } \right|_{\text{LVE}}$$ and $$\left| {G^{*} } \right|_{\text{ratio}}$$ , presented V/FM as the most worthy parameter, as it illustrated variation at different temperatures. The Linear Viscoelastic limits obtained from the study were relatively conservative compared to those from the SHRP study, this confirms the unsuitability of applying SHRP equations to the asphalt mastics. Moreover, the relationship instigated in the study can be used to reckon the LVE strain limit and to further analyse asphalt mastics.

Effect of continuous feeding of CO2 and pH in cell concentration and product titers in hIFNγ producing HEK293 cells: Induced metabolic shift for concomitant consumption of glucose and lactate

Although pH control at physiological levels is generally considered as the optimal culture condition, in some cases other strategies should be taken into account for their beneficial effects on process performance. pH and CO2 levels are chemical variables that have a major impact in cell growth and product titers in cell culture since their effect on key metabolic routes. HEK293 cells expressing recombinant hIFNγ showed different metabolic behavior when cultured in shake flask compared to pH-controlled bioreactors, in which a decrease in cell density and product titer were observed. This yield loss observed in bioreactor cultures could be reverted by adding 1% CO2 to air inlet flow in a non-controlled pH bioprocess. With this strategy, a significant outcome of 4-fold increase in terms of maximum cell density and 2-fold increase in volumetric concentration of recombinant protein (hIFNγ) when compared to the pH-controlled culture in bioreactor (standard culture conditions) has been obtained. Results evidenced the importance of pH and CO2 concentration in this case, in order to reproduce the behavior observed in optimization experiments performed in shake flasks. Thus, it was demonstrated that not always constant controlled variable setpoint (like pH or CO2 addition) becomes the best bioprocess performance strategy.

Experimental investigation of convective heat transfer augmentation for car radiator using ZnO–water nanofluids

New experimental data are reported for water based nanofluids to enhance the heat transfer performance of a car radiator. ZnO nanoparticles have been added into base fluid in different volumetric concentrations (0.01%, 0.08%, 0.2% and 0.3%). The effect of these volumetric concentrations on the heat transfer performance for car radiator is determined experimentally. Fluid flow rate has been varied in a range of 7–11LPM (liter per minute) (corresponding Reynolds number range was 17,500–27,600). Nanofluids showed heat transfer enhancement compared to the base fluid for all concentrations tested. The best heat transfer enhancement up to 46% was found compared to base fluid at 0.2% volumetric concentration. A further increase in volumetric concentration to 0.3% has shown a decrease in heat transfer enhancement compared to 0.2% volumetric concentration. Fluid inlet temperature was kept in a range of 45–55 °C. An increase in fluid inlet temperature from 45 °C to 55 °C showed increase in heat transfer rate up to 4%.

INVESTIGATION OF Fe-DOPED AND -UNDOPED NiO NANOCRYSTALLINE FILMS

The NiO and Fe -doped NiO thin films have been prepared by using spray pyrolysis technique. The effects of change in the volumetric concentration and substrate temperature on the film characteristics have been investigated. With the increase in volumetric concentration, the grain size and the roughness of the film increase; while the number of voids has been reduced. In case of NiO thin films the activation energy was found to increase from 0.33 eV to 0.40 eV with the increase in the film thickness. The analysis of the data suggests that the density of states at the Fermi level increase with the thickness of the film. In Fe -doped NiO film the density of states was found to increase with the increase in the substrate temperature. The optical measurements show that the maximum transmittance (≈77.13%) occurs for the film corresponding to the lowest volumetric concentration. On increasing the substrate temperature the transmittance also increases, thus displaying the decrease in the film thickness.

Effects of Non-Absorbable Gases on the Absorption Process of Aqueous LiBr Solution Film in a Vertical Tube (II)

Among the heat/mass exchange units composing an absorption system, the absorber, where the refrigerant vapor is absorbed into the liquid solution is the one least understood. In the present study, the effects of non-absorbable gas on the absorption process of aqueous lithium bromide solution falling film inside a vertical tube were experimentally investigated. In the range of film Reynolds number of 30 ~ 195, heat and mass transfer characteristics were investigated as a function of non-absorbable gas volumetric concentration, 0.2 ~ 20%. An increase of non-absorbable gas volumetric concentration degraded the mass transfer rate dramatically in the absorption process. The reduction of mass transfer rate was significant for the addition of small amount of non-absorbable gas to the pure vapor. At film Reynolds number of 130, an increase of non-absorbable gas concentration from 0.2 to 6.0% resulted in the decrease of mass transfer rate by 36% and 20% of non-absorbable gas by 59%. However the decrease of film Nusselt number with the increase of volumetric concentration of non absorbable gas was relatively smaller than the decrease of Sherwood number. Critical film Reynolds number was identified to exist for the maximum heat and mass transfer regardless of the volumetric concentration of non-absorbable gases.