General Properties for an Agrawal Thermal Engine

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This paper presents a finite-time thermodynamic optimization based on three different optimization criteria: Maximum Power Output (MP), Maximum Efficient Power (MEP), and Maximum Power Density (MPD), for a simplified Curzon-Ahlborn engine that was first proposed by Agrawal. The results obtained for the MP are compared with those obtained using MEP and MPD criteria. The results show that when a Newton heat transfer law is used, the efficiency values of the engine working in the MP regime are lower than the efficiency values ( τ ) obtained with the MEP and MPD regimes for all values of the parameter τ = T 2 / T 1 , where T 1 and T 2 are the hot and cold temperatures of the engine reservoirs ( T 2 < T 1 ) , respectively. However, when a Dulong-Petit heat transfer law is used, the efficiency values of the engine working at MEP are larger than those obtained with the MP and the MPD regimes for all values of τ . Notably, when 0 < τ < 0.68 , the efficiency values for the MP regime are larger than those obtained with the MPD regime. Also, when 0.68 < τ < 1 , the efficiency values for the aforementioned regimes are similar. Importantly, the parameter τ plays a crucial role in the engine performance, providing guidance during the design of real power plants.

Section: Modeling Methods and Resultssupporting

confidence: 78%

Comparative Performance Analysis of a Simplified Curzon-Ahlborn Engine

Páez-Hernández

Chimal-Eguía

Ladino-Luna

et al. 2018

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“…While a brief description of its concepts is given below, a more extensive description can be found in these two reviews [ 54 , 55 ]. After early work [ 56 , 57 , 58 ] the approach became more formalized and is now used in a variety of applications as for instance dealing with chemical reactions [ 59 , 60 , 61 , 62 , 63 ], engines of different kinds [ 64 , 65 , 66 , 67 ] and in particular with efficiencies of energy transformation devices [ 68 , 69 , 70 , 71 , 72 , 73 ].…”

Section: Endoreversible Stirling Enginementioning

confidence: 99%

Optimized Piston Motion for an Alpha-Type Stirling Engine

Masser

Khodja

Scheunert

et al. 2020

The Stirling engine is one of the most promising devices for the recovery of waste heat. Its power output can be optimized by several means, in particular by an optimized piston motion. Here, we investigate its potential performance improvements in the presence of dissipative processes. In order to ensure the possibility of a technical implementation and the simplicity of the optimization, we restrict the possible piston movements to a parametrized class of smooth piston motions. In this theoretical study the engine model is based on endoreversible thermodynamics, which allows us to incorporate non-equilibrium heat and mass transfer as well as the friction of the piston motion. The regenerator of the Stirling engine is modeled as ideal. An investigation of the impact of the individual loss mechanisms on the resulting optimized motion is carried out for a wide range of parameter values. We find that an optimization within our restricted piston motion class leads to a power gain of about 50% on average.

“…It has proven to be a suitable tool for modeling complex and dissipative systems while providing reliable predictions. Using endoreversible thermodynamics technical and natural systems of different types have been modeled such as heat engines [ 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 ], distillation processes [ 31 ], thermoelectric generators [ 32 , 33 , 34 ], electrochemical devices [ 35 , 36 ] and solar thermal heat engines [ 37 , 38 ]. In addition, the effects of stochastic fluctuations were recently modeled using this ansatz [ 39 , 40 , 41 ].…”

Section: Introductionmentioning

confidence: 99%

Endoreversible Modeling of a Hydraulic Recuperation System

Masser

Hoffmann

2020

Hybrid drive systems able to recover and reuse braking energy of the vehicle can reduce fuel consumption, air pollution and operating costs. Among them, hydraulic recuperation systems are particularly suitable for commercial vehicles, especially if they are already equipped with a hydraulic system. Thus far, the investigation of such systems has been limited to individual components or optimizing their control. In this paper, we focus on thermodynamic effects and their impact on the overall systems energy saving potential using endoreversible thermodynamics as the ideal framework for modeling. The dynamical behavior of the hydraulic recuperation system as well as energy savings are estimated using real data of a vehicle suitable for application. Here, energy savings accelerating the vehicle around 10% and a reduction in energy transferred to the conventional disc brakes around 58% are predicted. We further vary certain design and loss parameters—such as accumulator volume, displacement of the hydraulic unit, heat transfer coefficients or pipe diameter—and discuss their influence on the energy saving potential of the system. It turns out that heat transfer coefficients and pipe diameter are of less importance than accumulator volume and displacement of the hydraulic unit.