In the Natural Gas (NG) distribution network, the town border stations are used to reduce NG pressure. Currently, pressure reduction is done by using throttling valves that cause a significant amount of physical exergy loss. Reciprocating Expansion Engine (REE) is a new tool to recover this pressure exergy. This study presents a thermodynamic evaluation to simulate the REE rigorously. The GERG-2008 equation of state (EOS) as an accurate model is used to calculate NG thermodynamic properties. As the utilization of GERG-2008 EOS requires specific inputs (pressure, temperature and mole fraction), the Try & Error method is utilized (while the inputs are density, specific internal energy, and NG composition). An Artificial Neural Network (ANN) method is also developed as an additional and alternative tool to overcome a basic limitation of the Try & Error method (knowing the NG composition). The validation results show that the error of the ANN and Try & Error methods for temperature, pressure calculation are reported 0.03%, 0.08%, and 0.04%, 0.9%, respectively. Also, the results show that the NG compositions have a significant impact on REE performance so that the indicated work for Khangiran and Bidboland NG mixtures are reported 165 and 143 kJ/kg, respectively.
The accurate modeling of the fast-fill process occurring in Compressed Natural Gas (CNG) fuelled vehicle storage cylinders is a complex process and should be thoroughly studied. Final in-cylinder conditions should meet appropriate cylinder safety standards. The composition of natural gas plays an important role on its thermodynamic properties and consequently, on the fast-fill process and the final conditions. Here, a theoretical analysis has been developed to study the effects of the natural gas composition on the filling process of an onboard Natural Gas Vehicle (NGV) cylinder. The cylinder is assumed as a lumped system. The analysis is based on laws of thermodynamics and mass balance. Based on AGA8 Equation of State (EOS) and thermodynamics relationships, the required properties of natural gas mixtures have been calculated. The results are presented for an adiabatic system. The results show that the compositions of natural gas have great effects on the filling process and final in-cylinder conditions. Furthermore, the gas with less methane percentage in its composition is more suitable for the filling process.
The main motivation of this study is to offer, develop, and optimize a novel solar combined technology to bring sustainability to the industrial sector via supplying 100 % green and cost-effective heating and cooling. The combination of a special type of parabolic trough collector designed to be inexpensive with low-concentration yet high-optical efficiency and a specially developed bio-driven boiler to compensate for the fluctuations of the solar energy is the heart of the proposed system. The article presents a thorough complex optimization and techno-economic-environmental analysis of the proposed solution and conducts a benchmarking analysis against cheap but unsustainable technologies of today's industries for a large case study in Northern Europe. The results prove the strong impacts of the technology in emission reduction and lower cost production of industrial heating and cooling. The solar component of the system fulfills nearly 50 % of the total demand, with the biomass heater, burning sugarcane bagasse, covering the additional demand. For the proposed system, a levelized cost of energy of 69.9 USD/MWh and an emission index of 267.7 tons/GWh are achieved, while the identical and alternative systems would necessitate 9,660, 11,600, and 3860 tons of coal, wood, or LPG, respectively, to fulfill the park's thermal requirements.
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