Maximum Power From Fluid Flow by Applying the First and Second Laws of Thermodynamics

2016 ◽  
Vol 139 (3) ◽  
Author(s):  
German Amador Diaz ◽  
Jorge Duarte Forero ◽  
Jesus Garcia ◽  
Adriana Rincon ◽  
Armando Fontalvo ◽  
...  
Keyword(s):  
Heat Engine ◽  
Ideal Gas ◽  
Operating Conditions ◽  
Plant Performance ◽  
Working Fluid ◽  
Thermal Plant ◽  
Piston Cylinder ◽  
Proposed Model ◽  
Size Constraints ◽  
Flow Resistances

The application of equilibrium thermodynamics in the study of thermal plant performance under real operating conditions is a constant challenge. In this paper, an analysis of a reservoir pressure piston working between two linear flow resistances is performed by considering the friction of the piston cylinder system on the walls. The proposed model is developed to obtain the optimum power output and speed of the piston in terms of first law efficiency. If the friction on the piston–cylinder assembly is neglected, the expressions obtained are consistent with those presented in the literature under laminar regime. It was also demonstrated that for both laminar and turbulent regimes with overall size constraints, the power delivered can be maximized by balancing the upstream and downstream flow resistances of the piston. This paper also evaluated the influence of the overall size constraints and flow regime on the performance of the piston cylinder. This analysis is equivalent to evaluate the irreversibilities in an endo-irreversible Carnot heat engine with heat loss resistance between the engine and its heat reservoirs. The proposed model introduced some modifications to the results obtained from the recent literature and led to important conclusions. Finally, the proposed model was applied to calculate the lost available work in a turbine operating at steady flow conditions with an ideal gas as working fluid.

scholarly journals Large Eddy Simulations of Strongly Non-Ideal Compressible Flows through a Transonic Cascade

Energies ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 772
Author(s):  
Jean-Christophe Hoarau ◽  
Paola Cinnella ◽  
Xavier Gloerfelt
Keyword(s):  
Compressible Flows ◽  
Flow Behavior ◽  
Pressure Ratio ◽  
Organic Rankine Cycle ◽  
Ideal Gas ◽  
Operating Conditions ◽  
Large Eddy Simulations ◽  
Working Fluid ◽  
Viscous Effects ◽  
Large Eddy

Transonic flows of a molecularly complex organic fluid through a stator cascade were investigated by means of large eddy simulations (LESs). The selected configuration was considered as representative of the high-pressure stages of high-temperature Organic Rankine Cycle (ORC) axial turbines, which may exhibit significant non-ideal gas effects. A heavy fluorocarbon, perhydrophenanthrene (PP11), was selected as the working fluid to exacerbate deviations from the ideal flow behavior. The LESs were carried out at various operating conditions (pressure ratio and total conditions at inlet), and their influence on compressibility and viscous effects is discussed. The complex thermodynamic behavior of the fluid generates highly non-ideal shock systems at the blade trailing edge. These are shown to undergo complex interactions with the transitional viscous boundary layers and wakes, with an impact on the loss mechanisms and predicted loss coefficients compared to lower-fidelity models relying on the Reynolds-averaged Navier–Stokes (RANS) equations.

The Role of Internal Irreversibilities in the Performance and Stability of Power Plant Models Working at Maximum ϵ-Ecological Function

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Gabriel Valencia-Ortega ◽  
Sergio Levario-Medina ◽  
Marco Antonio Barranco-Jiménez
Keyword(s):  
Power Plants ◽  
Heat Engine ◽  
Combined Cycle ◽  
Ecological Function ◽  
Operating Conditions ◽  
Maximum Efficiency ◽  
Working Fluid ◽  
Engine Model ◽  
Improved Stability ◽  
The Stability

Abstract The proposal of models that account for the irreversibilities within the core engine has been the topic of interest to quantify the useful energy available during its conversion. In this work, we analyze the energetic optimization and stability (local and global) of three power plants, nuclear, combined-cycle, and simple-cycle ones, by means of the Curzon–Ahlborn heat engine model which considers a linear heat transfer law. The internal irreversibilities of the working fluid measured through the r-parameter are associated with the so-called “uncompensated Clausius heat.” In addition, the generalization of the ecological function is used to find operating conditions in three different zones, which allows to carry out a numerical analysis focused on the stability of power plants in each operation zone. We noted that not all power plants reveal stability in all the operation zones when irreversibilities are considered through the r-parameter on real-world power plants. However, an improved stability is shown in the zone limited by the maximum power output and maximum efficiency regimes.

scholarly journals Tailoring the Bore Surfaces of Water Hydraulic Axial Piston Machines to Piston Tilt and Deformation

Energies ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5997
Author(s):  
Meike Ernst ◽  
Andrea Vacca ◽  
Monika Ivantysynova ◽  
Georg Enevoldsen
Keyword(s):  
Experimental Testing ◽  
Hydrodynamic Pressure ◽  
Operating Conditions ◽  
Surface Shape ◽  
Working Fluid ◽  
Total Efficiency ◽  
Positive Displacement ◽  
Piston Cylinder ◽  
Low Viscosity ◽  
Axial Piston

A novel virtual prototyping algorithm has been developed to design one of the most critical lubricating interfaces in axial piston machines of the swash plate type—the piston–cylinder interface—for operation with water as the working fluid. Due to its low viscosity, the use of water as a lubricant can cause solid friction and wear in these machines at challenging operating conditions. The prototyping algorithm compensates for this by tailoring the shape of the bore surface that guides the motion of each piston in this type of positive displacement machine to conform with the piston surface, taking into account both the piston’s tilt and its deformation. Shaping these surfaces in this manner can render the interface more conducive to generating hydrodynamic pressure buildup that raises its load-carrying capacity. The present work first outlines the structure of the proposed algorithm, then presents a case study in which it is employed to design a bore surface shape for use with two prototypes, one virtual and one physical—both modified versions of a 444 cc commercial axial piston pump. Experimental testing of the physical prototype shows it to achieve a significantly higher maximum total efficiency than the stock unit.

Modeling of a New Crank-Less Rotary Heat Engine Concept for Solar Power Utilization

2018 ◽  
Author(s):  
Muhammad I. Rashad ◽  
Hend A. Faiad ◽  
Mahmoud Elzouka
Keyword(s):  
Degrees Of Freedom ◽  
Unit Cost ◽  
Heat Engine ◽  
Structure Design ◽  
Operating Conditions ◽  
Design Parameters ◽  
Working Fluid ◽  
Heat Engines ◽  
And Performance ◽  
Engine Concept

This paper presents the operating principle of a novel solar rotary crank-less heat engine. The proposed engine concept uses air as working fluid. The reciprocating motion is converted to a rotary motion by the mean of unbalanced mass and Coriolis effect, instead of a crank shaft. This facilitates the engine scaling and provides several degrees of freedom in terms of structure design and configuration. Unlike classical heat engines (i.e. Stirling), the proposed engine can be fixed to the ground which significantly reduce the generation unit cost. Firstly, the engine’s configuration is illustrated. Then, order analysis for the engine is carried out. The combined dynamics and thermal model is developed using ordinary differential equations which are then numerically solved by Simulink™. The resulting engine thermodynamics cycle is described. It incorporates the common thermodynamics processes (isobaric, isothermal, isochoric processes). Finally, the system behavior and performance are analyzed along with studying the effect of various design parameters on operating conditions such as engine speed, output power and efficiency.

scholarly journals Assessment of Uncertainties in Energetic and Exergetic Performances of a Flat Plate Solar Water Heater

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Intissar Harrabi ◽  
Mohamed Hamdi ◽  
Majdi Hazami
Keyword(s):  
Flat Plate ◽  
Multiwall Carbon Nanotubes ◽  
Operating Conditions ◽  
Working Fluid ◽  
Water Heater ◽  
Solar Water ◽  
Water Heaters ◽  
Proposed Model ◽  
Energy And Exergy ◽  
Solar Water Heaters

This paper aims to quantify sensitivities of energy and exergy performances of Flat Plate Solar Water Heaters (FPSWHs) with respect to measurement parameters. For that purpose, a computational tool is developed and validated by using outdoor conditions according to the test standard EN 12975. First of all, numerical simulations are compared with experimental results and available data in the literature, and the comparison shows a good agreement. Then, we apply the proposed model to the quantification of uncertainties associated with transient simulation. Results show that ambient temperature is the main relevant factor in operating conditions, and its effect reaches 13.7% and 3.89% on energy and exergy efficiencies, respectively, when the deviation in the sensor measurement is about ±1°C. When 0.15 v% multiwall carbon nanotubes (MWCNT)-Ethylene-Glycol (E-G) (30 : 70) nanofluid is used as working fluid, results show that a suitable choice of nanofluid properties achieves 84.7% of the thermal efficiency during the zero reduced temperature conditions compared to 75.4% when the collector works with E-G. Using common empirical correlations affects substantially the accuracy of the fitting parameters, and the deviation in exergy efficiency reaches 1.18%.

scholarly journals Regarding the application limitations of the Carnot, s theorem

2019 ◽  
Vol 21 (3) ◽  
pp. 32-45
Author(s):  
V. G. Kiselev
Keyword(s):  
Correction Term ◽  
Heat Engine ◽  
Thermodynamic Characteristics ◽  
Ideal Gas ◽  
Working Fluid ◽  
Cyclic Process ◽  
Carnot Cycle ◽  
Real Gas ◽  
Main Research ◽  
Thermodynamic Potentials

The purpose of this article is to perform a comparative study of a reversible heat engine with an ideal or real gas as a working fluid and to determine the change in its efficiency depending on the thermodynamic characteristics of the working fluid. The main research method is the method of thermodynamic potentials, based primarily on the analysis of changes in the free and internal energy of an ideal and real gas in a cyclic process. The theory of thermodynamic potentials is used to consider the Carnot quasistatic heat engine. A comparative analysis of its operation is carried out, for a cycle with both an ideal and a real gas as a working fluid. The possibility of analyzing cyclic processes occurring in heat engines using the method of thermodynamic potentials has been identified and substantiated. The study has shown that the existing formulation of the Carnot’s theorem is valid only for ideal gas as a working fluid. Based on the work carried out, the Carnot’s theorem in the general case can be formulated, for example, as follows: the efficiency of the heat engine ηr, when it operates at the reversible Carnot cycle with real gas as a working fluid, is determined by the following expression:hr= 1 - TB /TA + ε,where TA and TB are the temperatures of the upper and lower isotherms of the Carnot cycle, respectively; ε is the correction term (positive or negative), depending on the thermodynamic properties of a real gas, which tends to zero as the properties of a real gas approach the properties of an ideal gas.

scholarly journals Sensitivity Analysis of OTEC-CC-MX-1 kWe Plant Prototype

Energies ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2585
Author(s):  
Jessica Guadalupe Tobal-Cupul ◽  
Estela Cerezo-Acevedo ◽  
Yair Yosias Arriola-Gil ◽  
Hector Fernando Gomez-Garcia ◽  
Victor Manuel Romero-Medina
Keyword(s):  
Sensitivity Analysis ◽  
Experimental Tests ◽  
Caribbean Sea ◽  
Ocean Model ◽  
Operating Conditions ◽  
Working Fluid ◽  
Ocean Energy ◽  
Mexican Caribbean ◽  
Water Temperature Data ◽  
Mass Flows

The Mexican Caribbean Sea has potential zones for Ocean Thermal Energy Conversion (OTEC) implementation. Universidad del Caribe and Instituto de Ciencias del Mar y Limnologia, with the support of the Mexican Centre of Innovation in Ocean Energy, designed and constructed a prototype OTEC plant (OTEC-CC-MX-1 kWe), which is the first initiative in Mexico for exploitation of this type of renewable energy. This paper presents a sensitivity analysis whose objective was to know, before carrying out the experimental tests, the behavior of OTEC-CC-MX-1 kWe regarding temperature differences, as well as the non-possible operating conditions, which allows us to assess possible modifications in the prototype installation. An algorithm was developed to obtain the inlet and outlet temperatures of the water and working fluid in the heat exchangers using the monthly surface and deep-water temperature data from the Hybrid Coordinate Ocean Model and Geographically Weighted Regression Temperature Model for the Mexican Caribbean Sea. With these temperatures, the following were analyzed: fluctuation of thermal efficiency, mass flows of R-152a and water and power production. By analyzing the results, we verified maximum and minimum mass flows of water and R-152a to produce 1 kWe during a typical year in the Mexican Caribbean Sea and the conditions when the production of electricity is not possible for OTEC-CC-MX-1 kWe.

scholarly journals Component-Oriented Modeling of a Micro-Scale Organic Rankine Cycle System for Waste Heat Recovery Applications

2021 ◽  
Vol 11 (5) ◽  
pp. 1984
Author(s):  
Ramin Moradi ◽  
Emanuele Habib ◽  
Enrico Bocci ◽  
Luca Cioccolanti
Keyword(s):  
Electric Power ◽  
Heat Recovery ◽  
Waste Heat Recovery ◽  
Waste Heat ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Operating Conditions ◽  
Working Fluid ◽  
Pump Efficiency ◽  
Micro Scale

Organic Rankine cycle (ORC) systems are some of the most suitable technologies to produce electricity from low-temperature waste heat. In this study, a non-regenerative, micro-scale ORC system was tested in off-design conditions using R134a as the working fluid. The experimental data were then used to tune the semi-empirical models of the main components of the system. Eventually, the models were used in a component-oriented system solver to map the system electric performance at varying operating conditions. The analysis highlighted the non-negligible impact of the plunger pump on the system performance Indeed, the experimental results showed that the low pump efficiency in the investigated operating range can lead to negative net electric power in some working conditions. For most data points, the expander and the pump isentropic efficiencies are found in the approximate ranges of 35% to 55% and 17% to 34%, respectively. Furthermore, the maximum net electric power was about 200 W with a net electric efficiency of about 1.2%, thus also stressing the importance of a proper selection of the pump for waste heat recovery applications.

scholarly journals Action and Entropy in Heat Engines: An Action Revision of the Carnot Cycle

Entropy ◽  
2021 ◽  
Vol 23 (7) ◽  
pp. 860
Author(s):  
Ivan R. Kennedy ◽  
Migdat Hodzic
Keyword(s):  
Heat Engine ◽  
Working Fluid ◽  
Field Energy ◽  
Carnot Cycle ◽  
Gibbs Potential ◽  
Atmospheric Gases ◽  
Temperature Dependent ◽  
Expansion Phase ◽  
Heat Engines ◽  
The Difference

Despite the remarkable success of Carnot’s heat engine cycle in founding the discipline of thermodynamics two centuries ago, false viewpoints of his use of the caloric theory in the cycle linger, limiting his legacy. An action revision of the Carnot cycle can correct this, showing that the heat flow powering external mechanical work is compensated internally with configurational changes in the thermodynamic or Gibbs potential of the working fluid, differing in each stage of the cycle quantified by Carnot as caloric. Action (@) is a property of state having the same physical dimensions as angular momentum (mrv = mr2ω). However, this property is scalar rather than vectorial, including a dimensionless phase angle (@ = mr2ωδφ). We have recently confirmed with atmospheric gases that their entropy is a logarithmic function of the relative vibrational, rotational, and translational action ratios with Planck’s quantum of action ħ. The Carnot principle shows that the maximum rate of work (puissance motrice) possible from the reversible cycle is controlled by the difference in temperature of the hot source and the cold sink: the colder the better. This temperature difference between the source and the sink also controls the isothermal variations of the Gibbs potential of the working fluid, which Carnot identified as reversible temperature-dependent but unequal caloric exchanges. Importantly, the engine’s inertia ensures that heat from work performed adiabatically in the expansion phase is all restored to the working fluid during the adiabatic recompression, less the net work performed. This allows both the energy and the thermodynamic potential to return to the same values at the beginning of each cycle, which is a point strongly emphasized by Carnot. Our action revision equates Carnot’s calorique, or the non-sensible heat later described by Clausius as ‘work-heat’, exclusively to negative Gibbs energy (−G) or quantum field energy. This action field complements the sensible energy or vis-viva heat as molecular kinetic motion, and its recognition should have significance for designing more efficient heat engines or better understanding of the heat engine powering the Earth’s climates.

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