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• Thermo-hydraulic performance of PTSC's tube with conical turbulators is numerically investigated. • Hybrid nanofluid type, concentration, inlet fluid temperature effects are studied. • Conical turbulators augmented PTSC's thermal performance by 233.4% using Ag-SWCNT/Syltherm oil. • The thermal and exergetic efficiencies increment are 11.5% and 18.2%, respectively. • The maximum decrement in the entropy generation rate and ratio are 42.7% and 33.7%. Parabolic Trough Solar Collector (PTSC) is one of the most popular and an effective device that converts solar radiation into a heat or useful energy. However, it suffers from high temperature gradient and low thermal efficiency. The solution for this problem is to use new advanced coolants (hybrid nanofluids) in order to enhance PTSC's thermal efficiency. A numerical analysis on the thermo-hydraulic performance of a PTSC receiver's tube equipped with conical turbulators is presented. The Navier-Stokes equations are solved using Finite Volume Method (FVM) coupled with Monte Carlo Ray Tracing (MCRT) method. The flow and thermal characteristics as well as entropy generation of the PTSC's receiver tube are investigated for three hybrid nanofluids (Ag-SWCNT, Ag-MWCNT, and Ag-MgO) having a mixing ratio of (50:50) dispersed in Syltherm oil 800, Reynolds number (5000 to 100,000) and fluid inlet temperatures (400 to 650 K). The conical turbulators effectively augmented the thermal performance by 233.4% utilising Ag-SWCNT/Syltherm oil instead of pure Syltherm oil. The performance evaluation criterion is found to be in the range of 0.9–1.82. The thermal and exergetic efficiencies increased by 11.5% and 18.2%, respectively. The maximum decrement in the entropy generation rate and entropy generation ratio are 42.7% and 33.7%. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: In the present work, simple-to-use predictive tool, which is simpler than current available models and involves a fewer number of parameters, requiring less complicated and shorter computations, is formulated to arrive at an appropriate estimation of the transport properties (namely viscosity and thermal conductivity) of carbon dioxide (CO2) as a function of pressure and temperature. The correlation developed accurately works for temperatures between 260 and 450K as well as pressures between 10 and 70MPa which is the range of pressure that is widely considered in CO2 sequestration. Results have been compared with the reported data and excellent agreement has been obtained between the predicted results and observed values. The average absolute deviations were found to be 1.1 and 1.3% for viscosity and thermal conductivity of carbon dioxide respectively. Proposed simple predictive tool and can be of immense practical value for the engineers to have a quick check on the transport properties (namely viscosity and thermal conductivity) of carbon dioxide at various temperatures and pressures without performing any experimental measurements. In particular, personnel dealing with regulatory bodies of greenhouse gas control and process industries would find the proposed approach to be user friendly involving transparent calculations with no complex expressions. [Copyright &y& Elsevier]

Abstract: Among the methods that are being developed to date for CO2 capture and separation, carbon dioxide adsorption is of great interest due to its low energy consumption, low equipment cost and easiness for application. In this work, a simple method which is easier than existing approaches requiring more complicated and longer computations is presented to accurately predict the carbon dioxide adsorption isotherms for a microporous material as a function of temperature and partial pressure of carbon dioxide. The method appears promising and can be extended for CO2 capture as well as for separation of wide range of adsorbents and microporous materials including several molecular sieves merely by the quick readjustment of tuned coefficients. The proposed method showed consistently accurate results across the proposed pressure and temperature ranges. Predictions showed an average absolute deviation of 1.4% compared to existing Sips and Langmuir equations which show an average absolute deviations of 2.3% and 4%, respectively. The proposed method is superior owing to its accuracy and clear numerical background, wherein the relevant coefficients can be retuned quickly for various cases. This simple-to-use approach can be of immense practical value for the engineers and scientists to have a quick check on adsorption capacities of a given adsorbent at various temperatures and pressures without the necessity of any experimental measurements. In particular, personnel dealing with regulatory bodies of greenhouse gas control and process industries would find the proposed approach to be user friendly involving transparent calculations with no complex expressions. [Copyright &y& Elsevier]

Abstract: Evaluation of a triethylene glycol (TEG) system involves first establishing the minimum triethylene glycol (TEG) concentration required to meet the outlet gas water dew point specification. In the present work, simple-to-use correlation, which is simpler than currently available models involving a large number of parameters, requiring more complicated and longer computations, has been developed for the rapid estimation of the water dew point of a natural gas stream in equilibrium with a TEG solution at various temperatures and TEG concentrations. This correlation can be used to estimate the required TEG concentration for a particular application or the theoretical dew point depression for a given TEG concentration and contactor temperature. Actual outlet dewpoints depend on the TEG circulation rate and number of equilibrium stages, but typical approaches to equilibrium are 6–11°C. Equilibrium dewpoints are relatively insensitive to pressure and this correlation may be used up to 10 300kPa (abs) with little error. The proposed correlation covers VLE data for TEG–water system for contactor temperatures between 10°C and 80°C and TEG concentrations ranging from 90.00 to 99.999wt%. The average absolute deviation percent from the data reported in the literature is 0.5% which shows the excellent performance of proposed correlation. This simple-to-use correlation can be of immense practical value for the gas engineers to have a quick check on equilibrium water dew point of natural gas at various temperatures and TEG weight percents. In particular, personnel dealing with natural gas dehydration and processing would find the proposed approach to be user friendly involving no complex expressions with transparent calculations. [Copyright &y& Elsevier]

Abstract: In this paper, new correlations for predicting density and the solubility of carbon dioxide in pure water as well as the aqueous sodium chloride solutions are developed, where using the generated interaction parameters, the solubility model is applied to correlate the carbon dioxide solubilities in aqueous solutions for temperatures between 300 and 400K and pressures from 50 to 700bar. The correlation developed for predicting density of carbon dioxide accurately works for pressures between 25 and 700bar and temperatures between 293 and 433K. The results have been compared with the reported data and it was found that there is a good agreement between the prediction results and observed values. [Copyright &y& Elsevier]

The article focuses on the easy-to-use correlation to predict the emmissivities of carbon dioxide and water for combustion gas temperature function, carbon dioxide and water partial pressure, and radiation path length. It presents the optimization of boilers, furnaces and combustion equipment to estimate gas emissivities. It was found out that gases have a symmetrical molecular structure and that they do not emit or absorb radiation at low to moderate temperatures. It notes that the thickness, shape, surface area, pressure and temperature distribution of gas layer should be considered in calculating its emitted or absorbed radiation.