Assessment of economic, thermal and hydraulic performances a corrugated helical heat exchanger filled with non-Newtonian nanofluid

Improved heat transfer efficiency with considering economic analysis in heating systems is an interesting topic for researchers and scientists in recent years. This research investigates the heat transfer rate (HTR) and flow of non-Newtonian water-Carboxyl methyl cellulose (CMC) based Al2O3 nanofluid in a helical heat exchanger equipped with common and novel turbulators using two-phase model. The requirements for dimensions and cost reduction and also energy saving in thermal systems are the main goal of this study. According to gained results usage of corrugated channel in helical heat exchanger has a considerable influence on thermal and hydraulic performance evaluation criteria (THPEC) index of helical heat exchanger and can improve the THPEC index. Thus, Re = 5000 is obtained as an optimum value, in which the maximum THPEC value is achieved. As it is found in this paper, in case of using novel heat exchanger instead of the basic smooth system, the thermal properties (by considering Nusselt number) increases about 210%, the hydraulic performance (friction factor) reduces about 28%, performance evaluation criteria index increases about 57% and the material consumption (in case of similar THPEC) decreases about 31%. In another word, with considering economic analysis for the basic and novel system which has same efficiencies, the novel one has lower length and consequently 31% lower material

Maximization of propylene in an industrial FCC unit

YesThe FCC riser cracks gas oil into useful fuels such as gasoline, diesel and some lighter products such as ethylene and propylene, which are major building blocks for the polyethylene and polypropylene production. The production objective of the riser is usually the maximization of gasoline and diesel, but it can also be to maximize propylene. The optimization and parameter estimation of a six-lumped catalytic cracking reaction of gas oil in FCC is carried out to maximize the yield of propylene using an optimisation framework developed in gPROMS software 5.0 by optimizing mass flow rates and temperatures of catalyst and gas oil. The optimal values of 290.8 kg/s mass flow rate of catalyst and 53.4 kg/s mass flow rate of gas oil were obtained as propylene yield is maximized to give 8.95 wt%. When compared with the base case simulation value of 4.59 wt% propylene yield, the maximized propylene yield is increased by 95%

Electromagnetic wave scattering from rough layered interfaces: analysis with the small perturbation method and the small slope approximation

International audienceWe propose a theoretical study on the electromagnetic wave scattering from layered structures with an arbitrary number of rough interfaces by using the small perturbation method and the small slope approximation. The interfaces are characterized by Gaussian height distributions with zero mean values and Gaussian correlation functions. They can be correlated or not. The electromagnetic field in each medium is represented by a Rayleigh expansion and a perturbation method is used for solving the boundary value problem and determining the first-order scattering amplitudes by recurrence relations. The scattering amplitude under the first-order small slope approximation are deduced from results derived from the first-order small perturbation method. Comparison between these two analytical models and a numerical method based on the combination of scattering matrices is presented

Separation selectivity of various gases in the ionic liquid 1-ethyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate

The separation of carbon dioxide (CO2) from methane (CH4) is an important process in many industrial areas such as natural gas processing and biogas purification [1]. Natural gas also contains significant amounts of ethane, some propane, butane, and other higher hydrocarbons [2]. In natural gas treating, loss of heavy hydrocarbons is a concern. It is desirable to recover these compounds due to practical problems. There are many methods available for the removal of acid gases from gas streams. The most commonly used are chemical solvents, physical solvents, membranes and cryogenic fractionation [3]. Physical solvents tend to be favoured over chemical solvents when the concentration of acid gases is very high. However, if the concentration of heavy hydrocarbons is high, a physical solvent may not be the best option due to higher co-absorption of hydrocarbons. An acceptable solvent should have a high capacity for acid gas and a low capacity for hydrocarbons [4]. Therefore, ILs have been proposed to be used as a solvent for CO2 capture, because of their advantageous properties over conventional ones [5]. We found that the ionic liquid (IL) 1-ethyl-3 methylimidazoliumtris(pentafluoroethyl) trifluorophosphate ([emim][FAP]) shows the highest carbon dioxide (CO2) solubility of all ILs studied so far and shows higher selectivities for CO2/CH4 separations than any other IL, indicating the promising potential of using this IL for the separation of CO2 from natural gas. Also, the solubilities of C2H6, C3H8 and C4H10 in ([emim][FAP]) were measured and compared to the CO2 solubility in the same IL. The separation ratio between CO2 and hydrocarbons decreases as the hydrocarbon chain becomes longer. The selectivity increase accordingly to the order: SCO2/C4H10 <SCO2/C3H8 <SCO2/C2H6 <SCO2/CH4. A maximum selectivity is achieved at lower temperatures. Therefore, the CO2 removal from a natural gas stream is recommended to be performed at low temperatures in order to achieve the best separation. The obtained solubility data are modelled with the Peng-Robinson equation of state combined with quadratic mixing rule. The calculated data have been found to be in a good agreement with the experimental results

Performance Comparison of Mini-Rectangular Fin Heat Sinks Using Different Coolants: Supercritical CO₂, Water and Al₂O₃/H₂O Nanofluid

Mini-channel heatsinks have proven useful in removing high heat fluxes from microelectronic devices. However, further miniaturization of electronic devices requires significant enhancement in the mini-channel heatsinks’ thermohydraulic characteristics, which depend greatly on the coolant and geometrical configuration of the channel. Therefore, the current study explores the potential of mini-channel heatsinks’ using different coolants (water, nanofluid and supercritical carbon dioxide) and various channel configurations. The effect of various channel configurations on the thermohydraulic characteristics of the mini-channel heat sinks is evaluated numerically for different coolants employing three flow rates (17 g/s, 34 g/s and 50 g/s). Hence, the effects of fin height, spacing and thickness, and mass flow rate on the overall heat transfer coefficient (CHT) and pressure drop (ΔP) are reported for the abovementioned coolants. It is found that increasing the mass flow rate increases both the CHT and ΔP. It is also noted that increasing the fin height and spacing decreases both the CHT and ΔP, as opposed to increasing the thickness, which causes both the CHT and ΔP to increase. Among the three coolants used, the sCO2 shows superior performance compared to the water and nanofluid and this based on higher CHT and lower ΔP. Moreover, the performance evaluation criterion (PEC) for the sCO2 is higher than that for the water and nanofluid by 53% at 17 g/s flow rate and 243% at 50 g/s flow rate

Performance Comparison of Mini-Rectangular Fin Heat Sinks Using Different Coolants: Supercritical CO2, Water and Al2O3/H2O Nanofluid

Mini-channel heatsinks have proven useful in removing high heat fluxes from microelectronic devices. However, further miniaturization of electronic devices requires significant enhancement in the mini-channel heatsinks&rsquo; thermohydraulic characteristics, which depend greatly on the coolant and geometrical configuration of the channel. Therefore, the current study explores the potential of mini-channel heatsinks&rsquo; using different coolants (water, nanofluid and supercritical carbon dioxide) and various channel configurations. The effect of various channel configurations on the thermohydraulic characteristics of the mini-channel heat sinks is evaluated numerically for different coolants employing three flow rates (17 g/s, 34 g/s and 50 g/s). Hence, the effects of fin height, spacing and thickness, and mass flow rate on the overall heat transfer coefficient (CHT) and pressure drop (&Delta;P) are reported for the abovementioned coolants. It is found that increasing the mass flow rate increases both the CHT and &Delta;P. It is also noted that increasing the fin height and spacing decreases both the CHT and &Delta;P, as opposed to increasing the thickness, which causes both the CHT and &Delta;P to increase. Among the three coolants used, the sCO2 shows superior performance compared to the water and nanofluid and this based on higher CHT and lower &Delta;P. Moreover, the performance evaluation criterion (PEC) for the sCO2 is higher than that for the water and nanofluid by 53% at 17 g/s flow rate and 243% at 50 g/s flow rate