Environmental Impacts and Sustainability
Farhad Gholami; Iraj Mirzaee; Mortaza Khalilian
Abstract
Failure Mode and Effects Analysis (FMEA) is utilized for risk appraisal in various domains. In the FMEA methodology, each failure mode is evaluated by considering three risk factors: severity (S), occurrence (O), and detection (D). Subsequently, the Risk Priority Number (RPN) is obtained by multiplying ...
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Failure Mode and Effects Analysis (FMEA) is utilized for risk appraisal in various domains. In the FMEA methodology, each failure mode is evaluated by considering three risk factors: severity (S), occurrence (O), and detection (D). Subsequently, the Risk Priority Number (RPN) is obtained by multiplying these listed factors. This study introduces the Deviation Value Step-Wise Method (DVSM) as a new mathematical model for determining the scores of the SOD factors. This methodology consists of three main steps. Firstly, the FMEA technique is used to identify failure modes. Then, the DVSM is employed to assign weights to the SOD components. In this step, relative importance is determined based on linguistic variables. The third step involves ranking failure modes using the weighted RPN. Two general examples and a case study of two-pipe heat exchanger failure modes are considered to validate the proposed model and test the obtained results. The results demonstrate that the suggested approach has enhanced the overall prioritization of failure modes. This enables the Decision-Maker (DM) to identify primary failure modes and formulate corrective/preventive actions. Finally, both sensitivity analysis and energy efficiency investigation have been performed.
Advanced Energy Technologies
Iraj Mirzaee; Aref Razmjoo; Nader Pourmahmoud
Abstract
This study conducts thermodynamic analysis on three trigeneration cycles including Organic Rankine Cycle (ORC), Liquefied Natural Gas (LNG) cold energy, and absorption refrigeration cycle in order to select appropriate working fluids. Different types of ORC cycles including simple ORC, regenerative, ...
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This study conducts thermodynamic analysis on three trigeneration cycles including Organic Rankine Cycle (ORC), Liquefied Natural Gas (LNG) cold energy, and absorption refrigeration cycle in order to select appropriate working fluids. Different types of ORC cycles including simple ORC, regenerative, and ORC with Internal Heat Exchange (IHE) were investigated. For those types, the operation of six working fluids with different thermodynamic behaviors (R141b, R124, R236fa, R245fa, R600, and R123) was evaluated. In power plants, a low-grade heat source was provided by condensing boiler hot water energy while the thermal sink was prepared by cold energy of LNG. The effect of boiler temperature variation on energy and exergy efficiencies was investigated. According to the derived results, regenerative ORC-based systems possessed maximum energy and exergy efficiencies, while simple ORC and ORC with internal heat exchanger exhibited approximately the same quantities. Also, among these analyzed working fluids, R141b had the maximum energetic and exergetic efficiencies, while R124 and R236fa had minimum performance.
