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Amine solvents remain popular in the industries for post combustion carbon dioxide (CO2) capture. Dissociation constant of basic amine solvents plays significant role to influence the CO2 absorption. It is thus important to study the dissociation of new amine solvents for assessing their viability for CO2 capture. In the present work, potentiometric titration method is employed to determine the dissociation constants of dibasic (e. g. Piperazine (PZ), 1‐methyl piperazine (1‐MPZ) and tribasic amines (1‐(2‐aminoethyl‐piperazine) (AEPZ) which could be promising for formulating blended solvent system towards enhancing the rate of CO2 absorption. The estimated dissociation constants for the PZ and 1‐MPZ while match well with reported results, the dissociation constants for AEPZ has been determined newly here within the temperature range 298—318 K. In addition, the structural geometric parameters and Natural Bond Order (NBO) calculations of the amine solvents are performed based on Density Functional Theory (DFT). The NBO calculations predict charge distribution on the nitrogen and other elements, and envisage its effect on the pKa values of the amines. Further, potential energy surface (PES) scanning calculations are performed for AEPZ to explain it's ring inversion which is responsible for obtaining a single pKa value in experimental studies. [ABSTRACT FROM AUTHOR]

In this study, we present the idea of natural convection heat transfer from vertical cones with active base (i.e. all the surfaces are contributing in heat transfer process) for laminar flow in the range of Rayleigh number from 103 to 106. We did numerical simulations for different r/l ranging from 0.9 to 0.1 and orientation (tip upward and tip downward) keeping the total heat transfer area same for all the cases. From the numerical results, it can be concluded that average Nusselt number of downward tip cone is more compared to upward tip cone at same Rayleigh number for low r/l and for high r/l both give almost the same Nu when suspended in the air. When the cone is placed on the ground, downward tip cone is always more effective in natural convection than the upward tip cone. Average Nu and heat flux increase at particular Ra with decrease in r/l. A detailed study of the parameters like r/l, Rayleigh number on average Nu, heat flux, heat transfer ratio, flow field, and temperature plume can be found in this work. Finally simple and very accurate correlations for predicting average Nu are developed for all the studied cases of cone with varying r/l and Ra which will be very useful in designing heat transfer equipment. [ABSTRACT FROM AUTHOR]

Summary: Propylene is the most essential raw material and intermediate in the petrochemical sector. Industrial separation of propane and propylene is energy‐intensive and challenging, as they have similar molecular size and physical properties such as relative volatility. Based on the principle of solubility and diffusivity, alternatives for improved separation with energy reduction are being attempted. Also, separation based on molecular size difference is being explored to improve the propylene recovery as well as alleviate the high energy consumption. The present work reports an energy reduction, and a loss minimization achieved after implementation of the research outcome in the propylene fractionator (PF) located in the cracker complex of an industrial zone in India. At the cracker plant, the conventional PF operating at higher pressure (18 kg/cm2g) is used to produce Polymer grade Propylene. At the feed purification unit (FPU), the heat pump‐vapor recompression column operates at low pressure (10 kg/cm2g). This column is used to upgrade chemical‐grade propylene to polymer grade propylene. Process simulation with different scenarios has been developed for both the separation systems in Aspen Plus. Based on detailed study and adopted strategies, the energy consumption significantly reduced by 68% at FPU and waste heat utilization increased at PF column. Also, propylene losses were minimized after adopting the innovative concept of heat integration in both the separation units. The significant operational improvement for energy reduction up to 70% and product recovery up to 3% with enhanced safety achieved without major modification and cost at the industrial operation, reported in this work. [ABSTRACT FROM AUTHOR]

Summary: The utility of polyamine‐based solvent‐activators for the possible application in postcombustion CO2 capture technology has drawn considerable attention recently owing to its higher loading capacity as well as superior kinetics. The current work involves a comprehensive experimental cum theoretical investigation on the equilibrium solubility of CO2 pertaining to aqueous N‐(3‐aminopropyl)‐1,3‐propanediamine and its blends with N‐methyldiethanolamine and 2‐amino‐2‐methyl‐1‐propanol. The analysis was conducted within the operating temperature and CO2 partial pressure range of 303.2‐323.2 K and 2‐200 kPa, respectively. Two different mathematical models based on nonrigorous approaches such as equilibrium based modified Kent‐Eisenberg (KE) model and a multilayer feedforward neural network model have been developed to correlate the CO2 solubility data over a wide range of experimental conditions. Both the model predictions are well‐validated with the experimental results. The reaction scheme as well as the prevalence of important reaction products was further confirmed with qualitative 13C NMR as well as ATR‐FTIR analysis. Apart from these some of the important thermally induced transport properties viz, density, viscosity, and surface tension of the aqueous single and blended systems were measured and correlated with various consistent empirical models such as Redlich‐Kister and Grunberg‐Nissan model while surface tension data are modeled using temperature‐based multiple linear regression technique. [ABSTRACT FROM AUTHOR]

An experimental study was conducted on a laboratory-scale new infrared suppression (IRS) device to assess the mass entrainment of ambient air into it under various operating conditions. A numerical analysis was also undertaken to assess the mass entrainment rate against pertinent input parameters independently. The numerical results were validated against the experimental data to ensure the reliability of the numerical analysis of the new IRS device at real scales. The numerical method solves the three-dimensional, incompressible Navier-Stokes equations; the mass continuity equation; and the two-equation-based eddy viscosity model for the turbulent k-epsilon equations in the flow field. Numerical assessment of the air entrainment was performed for the conventional and the newly proposed IRS devices. A number of experiments on the new IRS device were carried out under various operating conditions. From the numerical study, it was observed that the conventional IRS device performs better than the new IRS device up to a geometric ratio of 1.4 (which is the ratio of diameters of the successive funnels used in an IRS device). Beyond the geometric ratio of 1.4, the newly proposed IRS device outperforms the conventional one significantly. For the new IRS device, the maximum mass entrainment was found to occur when four funnels were used and the nozzle was kept in flush condition with the lower opening of the bottom-most funnel. Mass entrainment increases with the nozzle-exit Reynolds number for the range of values considered in the study. [ABSTRACT FROM AUTHOR]

Natural convection heat transfer in a square cavity (with wavy or plane wall) filled with non-Newtonian power-law nanofluid has been elucidated for several input parameters like Ra spanning from 105 to 106, power-law index (n) from 0.6 to 1.4, and volume fraction of CuO nanoparticles (ϕ) from to 0 to 0.12. Effect of external magnetic field on heat transfer has been illustrated by varying the Ha from 0 to 90. In the present study, our main objective is to explore the effect of nanoparticles on heat transfer enhancement in non-Newtonian power-law fluid. It is found that the addition of nanoparticles (ϕ) to shear thinning fluid enhances the heat transfer approximately 15% when ϕ increases from 0 to 0.12 for Ha less than 60 at all Ra. For a shear thickening fluid, the same thing happens for all Ha at any Ra. The average surface Nusselt number for a cavity with wavy wall is less than that of a plane wall for all cases which is not true for the case of local Nusselt number. [ABSTRACT FROM AUTHOR]

Steam cracking is a fundamental application of olefin production which is the building block of petrochemical complex. Continuous efforts are being made to optimize the cracker performance by process-side optimization. The cracker furnace flue gas, which has a huge quantum of low-grade energy, is getting lost from the stack; a waste heat recovery system is being employed to generate ow-pressure steam. This also helps in the reduction of induced draft fan suction temperature. However, if there are no low-pressure steam consumers, the steam requires to be vented or partial heat recovery to be done. The lower heat recovery through waste heat recovery boiler restricts the cracking furnace throughput due to a higher suction temperature of the induced draft. A detailed steam network study has been done for a petrochemical complex having various downstream plants to maximize heat recovery as well as furnace throughput. For any equipment in question, to use a lower steam, it was a challenge to switch over from relatively higher-pressure steam to lower-pressure steam due to equipment design consideration as well as operating temperature requirement of any process. Different alternatives were thought of and evaluated based on process requirement, possibility of steam venting of other level steam, and cost of modifications. The outcome of this study has helped to utilize the low-pressure steam. The study indicated that for optimization of cracker performance, in addition to process side, there is a scope to improve on flue gas side operation also. [ABSTRACT FROM AUTHOR]

The continuity, momentum, and the energy equations have been solved in 3D to predict the thermal plume and flow field around an isothermal horizontal longitudinally finned hollow cylinder in air. Effect of Rayleigh number (Ra), L/D, H/D, and s/D on heat transfer from the finned cylinder have been investigated where the input parameters are varied in a wide range of 104 ≤ Ra ≤107, 0.5 ≤ L/D ≤ 5, 0.0833 ≤ H/D ≤ 2, and 0.0785 ≤ s/D ≤ 0.785. Average surface Nusselt number (Nu) increases with increase in Ra and decreases with increase in cylinder length and fin number for all H/D. Nu for a finned solid cylinder is found to be marginally higher than that of the hollow cylinder except at low H/D of 0.0833 and high Ra of 107 when s/D is less than 0.2617 for all L/D. Fin effectiveness is found to be increased with addition of taller fins for both the solid and hollow cylinder with longitudinal fins. Efficiency of the finned cylinder decreases with increase in fin height and Ra for all L/D and s/D. A general correlation of Nu as a function of all the pertinent input parameters (Ra, L/D, H/D, and s/D) has been proposed separately for the hollow isothermal cylinder having longitudinal fins, which can be used for industrial and academic purposes. [ABSTRACT FROM AUTHOR]

Numerical simulation of air entrainment into a mixing pipe has been performed by solving the equations of conservation of mass, momentum and energy along with a two-equation-basedk–ϵmodel. It was found that there exists an optimum shape of the mixing pipe (both for non-isothermal and isothermal flow condition) for maximum air entrainment into the pipe. It was also found from the numerical experiments that there exists an optimum length of the mixing pipe, both in forward and reverse direction, with respect to the position of the exit of the nozzle that can entrain maximum air into the pipe. There also exists optimum diameter of the mixing pipe and optimum distance of the nozzle from the entrance of the mixing pipe (irrespective of the different Reynolds number based on nozzle) that entrains maximum air into the pipe. For same Reynolds number, the cylindrical mixing pipe has interestingly a much shorter entrance length compared to a simple pipe. An optimum nozzle diameter could be decided by considering the mixing pipe entrainment rate and the back pressure developed by the nozzle. [ABSTRACT FROM PUBLISHER]

In engineering practice and thermodynamics texts, it is assumed that, for the expansion of a gas from a high-pressure tank to a low-pressure tank (through a valve) under adiabatic conditions, the process in the high-pressure tank is isentropic. No theoretical explanation or experimental proof is, however, cited in support of this assumption. A thorough theoretical investigation of this question is presented in this paper. The present numerical computation with an unsteady simulation using the first law of thermodynamics and with no explicit assumption regarding the thermodynamic process that takes place in the high-pressure tank establishes that the expansion in the high-pressure tank is indeed isentropic. Although an analytical proof has not been formulated, it is believed that the present computations constitute the first theoretical justification for the much-used isentropic assumption found in thermodynamics textbooks. A direct determination of a steady solution using an average exit enthalpy for the high-pressure tank also gives a correct result if the pressure ratio in the high-pressure tank is limited to 2. Even though the gas expansion in the high-pressure tank turns out to be isentropic, it is shown that the overall process of gas expansion and compression to the low-pressure tank is an irreversible process. [ABSTRACT FROM AUTHOR]

The rate of air suction into a louvered cylindrical funnel with lateral openings has been computed numerically by solving the equations of conservation of mass, momentum, and energy along with the two k-ε turbulence closure equations. It was found that the air suction rate into a louvered funnel can be maximum for an optimum nozzle protrusion length into the funnel irrespective of the nozzle fluid temperature. There also exists an optimum funnel diameter (irrespective of the nozzle fluid temperature) and funnel height for which the air suction rate can be the maximum. Keeping the volume of the funnel constant, the shape of the funnel was changed to a frustum. It was found that an inverted frustum with a value of r1/r2 0.8 could suck the maximum amount of air compared to a cylindrical funnel of the same volume. The cylindrical sucking funnel has interestingly a much shorter entrance length compared to a simple pipe flow case with the same entrance Reynolds number. The entrance length for the sucking funnel is also a function of the nozzle fluid temperature, and a simple relation for the entrance length as a function of Ren and Tn/T∞ could also be developed for a sucking funnel. Numerical experiments were done for an inclined funnel to compute the mass suction into it. It was found that for Gr/Re2 ≤ 0.4 (where Gr is the Grashof number and Re is the Reynolds number) given by the funnel inclination had no effect on the rate of mass suction while for 0.4 < Gr/Re2 < 1 the funnel inclination had marginal influence. As the value of Gr/Re2 increased beyond 1 the influence of the funnel inclination on rate of mass suction was found to be significant. [ABSTRACT FROM AUTHOR]

This paper discusses the computation of air entrainment in to the louvers of a cylindrical funnel as a result of a high-velocity isothermal air jet placed inside the funnel having different lengths of protrusion and different funnel diameters. The experimental setup consists of a cylindrical Perspex tube with circular louvers cut around it. The flow through the nozzle is measured with a rotameter, and the velocity at the cylinder outlet is measured with a hot wire anemometer. The numerical simulation is carried out by solving the conservation equations of mass and momentum for the funnel with a surrounding computational domain so that the suction can take place at the louver entry. The resulting equations have been solved numerically using finite volume technique in an unstructured grid employing eddy viscosity based two-equation k-ϵ turbulence model of Fluent 6.3. It has been found from the experiment and the CFD computation that there exists an optimum funnel diameter for which the mass ingress into the funnel is highest, and also there exists an optimum protrusion length of the nozzle that entrains maximum air flow into the funnel. For isothermal air suction the mass ingress into the funnel does not depend on the inclination of the funnel, whereas for low velocity and high temperature of the nozzle fluid the mass ingress in to the funnel depends on the inclination of the funnel. After a critical nozzle velocity (Gr/Re² < 0.5), the mass ingress into the funnel does not again depend on the inclination of the funnel. An approximate relation for the entrance length of a sucking pipe has also been developed from the present CFD solution. The original contribution of the paper is the setting of a computational methodology for computing various conditions of suction flow in to a funnel while having the numerical confidence by comparing the CFD result with a small-scale experimental measurement in the laboratory. [ABSTRACT FROM AUTHOR]

Basic engineering education should be supported by state-of-the-art computational tools such as Engineering Equation Solver (EES), Matlab, or Mathematica, so that students can solve complicated and real-life problems easily in a short time. It also allows them to develop a practical feel for the subject, which is normally difficult using traditional methods of teaching, where students use a textbook for basic learning, a calculator to solve problems and a notebook to record answers. If the method of teaching proposed here is followed in any engineering subject then pen-and-paper examination can be minimized; furthermore, examination on a computer can be done online. [ABSTRACT FROM AUTHOR]

This article presents the results of computations on pilot-based turbulent methane/air co-flow diffusion flames under the influence of the preheated oxidizer temperature ranging from 293 to 723 K at two operating pressures of 1 and 3 atm. The focus is on investigating the soot formation and flame structure under the influence of both the preheated air and combustor pressure. The computations were conducted in a 2D axisymmetric computational domain by solving the Favre averaged governing equation using the finite volume-based CFD code Ansys Fluent 19.2. A steady laminar flamelet model in combination with GRI Mech 3.0 was considered for combustion modeling. A semi-empirical acetylene-based soot model proposed by Brookes and Moss was adopted to predict soot. A careful validation was initially carried out with the measurements by Brookes and Moss at 1 and 3 atm with the temperature of both fuel and air at 290 K before carrying out further simulation using preheated air. The results by the present computation demonstrated that the flame peak temperature increased with air temperature for both 1 and 3 atm, while it reduced with pressure elevation. The OH mole fraction, signifying reaction rate, increased with a rise in the oxidizer temperature at the two operating pressures of 1 and 3 atm. However, a reduced value of OH mole fraction was observed at 3 atm when compared with 1 atm. The soot volume fraction increased with air temperature as well as pressure. The reaction rate by soot surface growth, soot mass-nucleation, and soot-oxidation rate increased with an increase in both air temperature and pressure. Finally, the fuel consumption rate showed a decreasing trend with air temperature and an increasing trend with pressure elevation. [ABSTRACT FROM AUTHOR]