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Thermodynamic modeling and analysis of a novel heat recovery system in a natural gas city gate station

Khanmohammadi, Shoaib, Saadat-Targhi, Morteza
Journal of cleaner production 2019 v.224 pp. 346-360
air, electric power, exergy, heat recovery, mass flow, natural gas, thermal energy, thermodynamic models, thermoelectric generators
In the present study, five configurations of integrated system are introduced and comprehensive thermodynamic modeling and analysis for different arrangements are carried out. An organic Rankine flash cycle (ORFC) and a thermoelectric generator (TEG) are integrated with a real city gate station (CGS) to recover the thermal energy of exhaust gas at 400 °C in an indirect water bath heater (IWBH). The new aspect of the present research is proposal the novel arrangements of the TEG modules, ORFC and IWBH to improve the thermal performance of the CGS integrated system.Energy and exergy analyses employed to evaluate different arrangements of integrated systems.Comparative analysis of different suggested systems revealed that integrated system including IWBH, ORFC and TEG modules with placing the TEG modules after ORFC (Case V) shows better performance. Due to the better performance, Case V is considered for more studies. Under the given condition for the selected case, in a complete year, results indicate that the maximum and minimum values of electrical output power for TEG modules is 132 W and 100 W and for ORFC is 11.5 kW and 2.1 kW. Also, the parametric study of the Case V inferred that with increasing the amount of excess air form 50%–200%, the fuel mass flow rate increased by 35.6% which ultimately leads to a reduction in thermal efficiency of the system. The results suggests that proper arrangement of TEG modules and ORFC in the IWBH can improve the total thermal efficiency as well as the total electrical output power. Analyses of different proposed arrangements, also indicates that with the use ORFC and TEG modules in the worst and best cases 2.284 kW and 5.904 kW electrical energy can be recovered from the IWBH in the CGS.