Analysis of Refrigeration Cycle Performance with an Ejector

A conventional refrigeration cycle uses expansion device between the condenser and the evaporator which has losses during the expansion process. A refrigeration cycle with ejector is a promising modification to improve the performance of conventional refrigeration cycle. The ejector is used to recover some of the available work so that the compressor suction pressure increases. To investigate the enhancement a model with R134a refrigerant was developed. To solve the set of equations and simulate the cycle performance a subroutine was written on engineering equation solver (EES) environment. At specific conditions, the refrigerant properties are obtained from EES. At the design conditions the ejector refrigeration cycle achieved 5.141 COP compared to 4.609 COP of the conventional refrigeration cycle. This means that ejector refrigeration cycle offers better COP with 10.35% improvement compared to conventional refrigeration cycle. Parametric analysis of ejector refrigeration cycle indicated that COP was influenced significantly by evaporator and condenser temperatures, entrainment ratio and diffuser efficiency

Analysis of Refrigeration Cycle Performance with an Ejector

A conventional refrigeration cycle uses expansion device between the condenser and the evaporator which has losses during the expansion process. A refrigeration cycle with ejector is a promising modification to improve the performance of conventional refrigeration cycle. The ejector is used to recover some of the available work so that the compressor suction pressure increases. To investigate the enhancement a model with R134a refrigerant was developed. To solve the set of equations and simulate the cycle performance a subroutine was written on engineering equation solver (EES) environment. At specific conditions, the refrigerant properties are obtained from EES. At the design conditions the ejector refrigeration cycle achieved 5.141 COP compared to 4.609 COP of the conventional refrigeration cycle. This means that ejector refrigeration cycle offers better COP with 10.35% improvement compared to conventional refrigeration cycle. Parametric analysis of ejector refrigeration cycle indicated that COP was influenced significantly by evaporator and condenser temperatures, entrainment ratio and diffuser efficiency

A Review on Gas Turbine Gas-Path Diagnostics : State-of-the-Art Methods, Challenges and Opportunities

Gas-path diagnostics is an essential part of gas turbine (GT) condition-based maintenance (CBM). There exists extensive literature on GT gas-path diagnostics and a variety of methods have been introduced. The fundamental limitations of the conventional methods such as the inability to deal with the nonlinear engine behavior, measurement uncertainty, simultaneous faults, and the limited number of sensors available remain the driving force for exploring more advanced techniques. This review aims to provide a critical survey of the existing literature produced in the area over the past few decades. In the first section, the issue of GT degradation is addressed, aiming to identify the type of physical faults that degrade a gas turbine performance, which gas-path faults contribute more significantly to the overall performance loss, and which specific components often encounter these faults. A brief overview is then given about the inconsistencies in the literature on gas-path diagnostics followed by a discussion of the various challenges against successful gas-path diagnostics and the major desirable characteristics that an advanced fault diagnostic technique should ideally possess. At this point, the available fault diagnostic methods are thoroughly reviewed, and their strengths and weaknesses summarized. Artificial intelligence (AI) based and hybrid diagnostic methods have received a great deal of attention due to their promising potentials to address the above-mentioned limitations along with providing accurate diagnostic results. Moreover, the available validation techniques that system developers used in the past to evaluate the performance of their proposed diagnostic algorithms are discussed. Finally, concluding remarks and recommendations for further investigations are provided.DIAGNOSI

Computational analysis of the inflow air slot size influence on solar vortex generator peformance

Nowadays, attention is directed towards the possibilities of harnessing the potential of tornado by creating an artificial convective vortices for green electricity generation. In view of this research trending, a novel new solar vortex power generator, designed, fabricated and experimented at University Technology PETRONAS, Malaysia. In this paper, ANSYS - FLUENT 15 software was used to simulate the influence of inflow slot size on the vortex updraft velocity. Two cases hav been investigated. Case 1 with new dimension of 0.1 m width and guide vane height of 0.6 m. Whereas, case 2 with slot dimension of 0.3 m height and 0.15 m width. From the attained results, it could be deduced that the slot size is an important parameter which impacts on the vortex strength. The vortex exit velocity increased by 50% a nd by 2.6% for the case 1 and case 2, respectively. This indicates that the slot height is highly influencing the vortex strength. Thus far, the indexes from the numerical simulation can be used in re-designing of the inflow slot size for optimal performance

Performance Analysis of Transcritical Carbon Dioxide Rankine Cycle with Regenerator

Transcritical carbon dioxide Rankine cycle (TCRC) has a potential to convert low grade heat source into power. Thus, the objective of this paper is to evaluate TCRC performance based on the first and the second law of thermodynamics for wide and different operating conditions. To address this, TCRC thermal efficiency, exergetic efficiency, utilization ratio and the exergy destruction of the components are analyzed parametrically. Engineering Equation Solver (EES) is used to solve the set of equations and to evaluate the working fluid properties at the given conditions. For the analysis compressor efficiency, turbine efficiency and effectiveness of the regenerator are assumed to be 0.9, 0.9 and 0.95, respectively. The pump inlet pressure was assumed to be 6.2 MPa. It is found that at 10 MPa turbine inlet pressure 240°C is the optimal turbine inlet temperature operating condition. The percentage of exergy destructions at 240°C turbine inlet temperature are 0.94, 4.53, 9.55, 41.23, and 43.74 by the pump, turbine, condenser, heater and regenerator, respectively. Hence, the highest and the smallest exergy destructions are in the regenerator and the pump. This study will help to select the potential component for further improvement

Performance Analysis of Transcritical Carbon Dioxide Rankine Cycle with Regenerator

Transcritical carbon dioxide Rankine cycle (TCRC) has a potential to convert low grade heat source into power. Thus, the objective of this paper is to evaluate TCRC performance based on the first and the second law of thermodynamics for wide and different operating conditions. To address this, TCRC thermal efficiency, exergetic efficiency, utilization ratio and the exergy destruction of the components are analyzed parametrically. Engineering Equation Solver (EES) is used to solve the set of equations and to evaluate the working fluid properties at the given conditions. For the analysis compressor efficiency, turbine efficiency and effectiveness of the regenerator are assumed to be 0.9, 0.9 and 0.95, respectively. The pump inlet pressure was assumed to be 6.2 MPa. It is found that at 10 MPa turbine inlet pressure 240°C is the optimal turbine inlet temperature operating condition. The percentage of exergy destructions at 240°C turbine inlet temperature are 0.94, 4.53, 9.55, 41.23, and 43.74 by the pump, turbine, condenser, heater and regenerator, respectively. Hence, the highest and the smallest exergy destructions are in the regenerator and the pump. This study will help to select the potential component for further improvement

Design of Flue Gas-Air Heat Exchanger for Regeneration of Desiccant System

Heat recovering from biogas waste energy requires robust heat exchanger design. This paper presents the design of fuel gas-air heat exchanger (FGAHE) for recovering waste heat from biogas burning to regenerate desiccant material. Mathematical model was built to design the FGAHE based on logarithmic mean temperature difference (LMTD) and staggered tube bank heat transfer correlations. MATLAB code was developed to solve the algorithm based on overall heat transfer coefficient iteration technique. The effect on tube diameter on design and thermal characteristics of FGAHE is investigated. The results revealed that the smaller tube diameter leads to smaller heat transfer area and tube. On the other hand, the overall heat transfer coefficient and Nusselt numbers have larger rates at smaller tube diameter. In conclusion, the nominated tube diameter for FGAHE is the smaller diameter of 0.0127 m due to the high thermal performance

Design of Flue Gas-Air Heat Exchanger for Regeneration of Desiccant System

Heat recovering from biogas waste energy requires robust heat exchanger design. This paper presents the design of fuel gas-air heat exchanger (FGAHE) for recovering waste heat from biogas burning to regenerate desiccant material. Mathematical model was built to design the FGAHE based on logarithmic mean temperature difference (LMTD) and staggered tube bank heat transfer correlations. MATLAB code was developed to solve the algorithm based on overall heat transfer coefficient iteration technique. The effect on tube diameter on design and thermal characteristics of FGAHE is investigated. The results revealed that the smaller tube diameter leads to smaller heat transfer area and tube. On the other hand, the overall heat transfer coefficient and Nusselt numbers have larger rates at smaller tube diameter. In conclusion, the nominated tube diameter for FGAHE is the smaller diameter of 0.0127 m due to the high thermal performance

CFD modeling of artificial vortex air generator for green electric power

This paper presents and discusses a Computational Fluid Dynamics (CFD) simulation of artificial vortex air generator as part of the preliminary of Solar Vortex Power Generator for an electrical power generation. A vortex air generator system was built, consisting of concentric cylinders. The inner cylinder was fitted with stationary air guide vanes and covered at the top by a transparent plate to capture the solar radiation and create swirling updraft flow which is able to rotate wind turbine and produces power. The influence of inlet air velocity and temperature on the swirling strength and mass flow generated has been evaluated by validated CFD simulation. ANSYS Fluent software was adopted to solve the 3-D, steady state of Navier-Stokes and energy equations in cylindrical coordinate system integrated with discrete ordinates (DO) radiation model. For the preliminary vortex generator design, the CFD results were validated first with previous experimental measurements. Then the variable operation parameters were carried out on the proposed model. The simulation result demonstrated that inflow velocity is a key parameter for enhancing the system performance. By increasing the inflow velocity from 0.4 m/s to 0.6 m/s and inflow temperature 323°k the enhancement rate of the mass air flow generated reached to 26% compared with 7% when increase the inflow temperature to 328°k and inflow velocity 0.4 m/s

Computational analysis of the inflow air slot size influence on solar vortex generator peformance

Nowadays, attention is directed towards the possibilities of harnessing the potential of tornado by creating an artificial convective vortices for green electricity generation. In view of this research trending, a novel new solar vortex power generator, designed, fabricated and experimented at University Technology PETRONAS, Malaysia. In this paper, ANSYS - FLUENT 15 software was used to simulate the influence of inflow slot size on the vortex updraft velocity. Two cases hav been investigated. Case 1 with new dimension of 0.1 m width and guide vane height of 0.6 m. Whereas, case 2 with slot dimension of 0.3 m height and 0.15 m width. From the attained results, it could be deduced that the slot size is an important parameter which impacts on the vortex strength. The vortex exit velocity increased by 50% a nd by 2.6% for the case 1 and case 2, respectively. This indicates that the slot height is highly influencing the vortex strength. Thus far, the indexes from the numerical simulation can be used in re-designing of the inflow slot size for optimal performance