A Novel Hydraulic Heat Engine Based on Ferrofluid Displacer With Applications in Solar Power Generation

2017 ◽  
Author(s):  
Mohsen Saadat ◽  
Mehdi Mirzakhanloo ◽  
Pieter Gagnon ◽  
Mohammad-Reza Alam
Keyword(s):  
Heat Transfer ◽  
Power Density ◽  
Heat Engine ◽  
Closed Cycle ◽  
Dynamic Simulations ◽  
Solar Power Generation ◽  
Heat Engines ◽  
Stirling Engines ◽  
Transfer Capability ◽  
Order Of Magnitude

Conventional closed cycle heat engines — such as Stirling engines — have many advantages, such as high theoretical efficiency and the ability to produce useful work out of any heat source. However, they suffer from low power density due to poor heat transfer capability between the working gas and its surrounding walls. In this work, we proposed a new architecture where the solid displacer of a Stirling engine is replaced with a ferrofluid liquid displacer. In this approach, the relative displacer location with respects to the engine chamber is controlled (and stabilized) through a strong magnetic field generated by a permanent magnet. The liquid nature of the displacer allows the hot and cold chambers of the engine to be filled with porous material, improving the heat transfer by an order of magnitude. Additionally, this engine architecture mitigates sealing issues, can operate at higher pressures, and has naturally lubricating surfaces. A relatively simple configuration of this idea is modeled in this work. Exploratory dynamic simulations of this unoptimized architecture show a thermal efficiency of 21% and a power density of approximately 700W/lit.

scholarly journals Work Criteria Function of Irreversible Heat Engines

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Mahmoud Huleihil
Keyword(s):  
Heat Transfer ◽  
Power Density ◽  
Design Process ◽  
Heat Engine ◽  
Educational Tool ◽  
Heat Engines ◽  
Efficient Power

The irreversible heat engine is reconsidered with a general heat transfer law. Three criteria known in the literature—power, power density, and efficient power—are redefined in terms of the work criteria function (WCF), a concept introduced in this study. The formulation enabled the suggestion and analysis of a unique criterion—the efficient power density (which accounts for the efficiency and power density). Practically speaking, the efficient power and the efficient power density could be defined on any order based on the WCF. The applicability of the WCF is illustrated for the Newtonian heat transfer law (n=1) and for the radiative law (n=4). The importance of WCF is twofold: it gives an explicit design and educational tool to analyze and to display graphically the different criteria side by side and thus helps in design process. Finally, the criteria were compared and some conclusions were drawn.

Performance Optimization and Parametric Analysis of a Class of Solar-Driven Heat Engines

2010 ◽  
Author(s):  
Houcheng Zhang ◽  
Lanmei Wu ◽  
Guoxing Lin
Keyword(s):  
Heat Transfer ◽  
Heat Loss ◽  
Performance Optimization ◽  
Solar Collector ◽  
Heat Engine ◽  
Working Fluid ◽  
Convection Heat ◽  
Combined System ◽  
Heat Engines ◽  
Internal Irreversibility

A class of solar-driven heat engines is modeled as a combined system consisting of a solar collector and a unified heat engine, in which muti-irreversibilities including not only the finite rate heat transfer and the internal irreversibility, but also radiation-convection heat loss from the solar collector to the ambience are taken into account. The maximum overall efficiency of the system, the optimal operating temperature of the solar collector, the optimal temperatures of the working fluid and the optimal ratio of heat transfer areas are calculated by using numerical calculation method. The influences of radiation-convection heat loss of the collector and internal irreversibility on the cyclic performances of the solar-driven heat engine system are revealed. The results obtained in the present paper are more general than those in literature and the performance characteristics of several solar-driven heat engines such as Carnot, Brayton, Braysson and so on can be directly derived from them.

Thermo-Mechanical Modeling of a Shape Memory Alloy Heat Engine

2011 ◽  
Author(s):  
Christopher B. Churchill ◽  
John Shaw
Keyword(s):  
Heat Transfer ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Heat Engine ◽  
The United States ◽  
Thermodynamic Efficiency ◽  
Low Grade ◽  
Heat Engines ◽  
Deformation Mechanics ◽  
Sma Spring

Two thirds of the energy generated in the United States is currently lost as waste heat, representing a potentially vast source of green energy. Low Carnot efficiency is an inherent limitation of extracting energy from low-grade thermal sources (temperature gradients near or below 100C), and SMA heat engines could be useful for those applications where low weight and packaging are overriding considerations. Although many shape memory alloy (SMA) heat engines have been proposed to harvest this energy, and a few have been built and demonstrated in past decades, they have not been commercially successful. Some of the barriers to commercialization include their perceived low thermodynamic efficiency, high material cost, low material durability, complexities when using fluid baths, and the lack of robust constitutive models and design tools. Recent advances, however, in SMA longevity, reductions in materials costs (as production volumes have increased), and a better understanding of SMA behavior have stimulated new research on SMA heat engines. The Lightweight Thermal Energy Recovery System (LighTERS) is an ongoing ARPA-E funded collaboration between General Motors, HRL Laboratories, Dynalloy, Inc., and the University of Michigan. In the LighTERS engine (a refinement of the Dr. Johnson engine), a closed loop SMA spring element generates mechanical power by pulling itself between alternating hot and cold air regions. The first known thermo-mechanical model for this type of heat engine was developed in three stages. First, the constitutive and heat transfer relationships of an SMA spring form were characterized experimentally. Second, those relationships were used as inputs in a steady-state model of the heat engine, including both convective heat transfer and large-deformation mechanics. Finally, the model was validated successfully against measurements of a experimental heat engine built at HRL Labs.

scholarly journals Thermodynamicly similar indicator diagrams of the heat engines Energy non-dimensional diagram of the heat engine closed cycle

2020 ◽  
Vol 1 (2) ◽  
pp. 10-17
Author(s):  
F.E. Kalnitskiy ◽  
◽  
D.l. Morozov ◽  
M.G. Tatarov ◽  
A.I. Fedulov ◽  
...  
Keyword(s):  
Heat Engine ◽  
Closed Cycle ◽  
Heat Engines

scholarly journals Optimization, Stability, and Entropy in Endoreversible Heat Engines

Entropy ◽  
2020 ◽  
Vol 22 (11) ◽  
pp. 1323
Author(s):  
Julian Gonzalez-Ayala ◽  
José Miguel Mateos Roco ◽  
Alejandro Medina ◽  
Antonio Calvo Hernández
Keyword(s):  
Heat Transfer ◽  
Stationary State ◽  
Entropy Generation ◽  
Pareto Front ◽  
Heat Engine ◽  
Heat Fluxes ◽  
Working Fluid ◽  
Input Output ◽  
Engine Model ◽  
Heat Engines

The stability of endoreversible heat engines has been extensively studied in the literature. In this paper, an alternative dynamic equations system was obtained by using restitution forces that bring the system back to the stationary state. The departing point is the assumption that the system has a stationary fixed point, along with a Taylor expansion in the first order of the input/output heat fluxes, without further specifications regarding the properties of the working fluid or the heat device specifications. Specific cases of the Newton and the phenomenological heat transfer laws in a Carnot-like heat engine model were analyzed. It was shown that the evolution of the trajectories toward the stationary state have relevant consequences on the performance of the system. A major role was played by the symmetries/asymmetries of the conductance ratio σhc of the heat transfer law associated with the input/output heat exchanges. Accordingly, three main behaviors were observed: (1) For small σhc values, the thermodynamic trajectories evolved near the endoreversible limit, improving the efficiency and power output values with a decrease in entropy generation; (2) for large σhc values, the thermodynamic trajectories evolved either near the Pareto front or near the endoreversible limit, and in both cases, they improved the efficiency and power values with a decrease in entropy generation; (3) for the symmetric case (σhc=1), the trajectories evolved either with increasing entropy generation tending toward the Pareto front or with a decrease in entropy generation tending toward the endoreversible limit. Moreover, it was shown that the total entropy generation can define a time scale for both the operation cycle time and the relaxation characteristic time.

The Regenerative Criteria of an Irreversible Brayton Heat Engine and its General Optimum Performance Characteristics

2005 ◽  
Vol 128 (3) ◽  
pp. 216-222 ◽  
Author(s):  
Yue Zhang ◽  
Congjie Ou ◽  
Bihong Lin ◽  
Jincan Chen
Keyword(s):  
Heat Transfer ◽  
Power Output ◽  
Pressure Ratio ◽  
Heat Engine ◽  
Optimal Performance ◽  
Performance Characteristics ◽  
Heat Transfer Area ◽  
Total Heat Transfer ◽  
Heat Engines ◽  
Compression And Expansion

An irreversible cycle model of the Brayton heat engine is established, in which the irreversibilities resulting from the internal dissipation of the working substance in the adiabatic compression and expansion processes and the finite-rate heat transfer in the regenerative and constant-pressure processes are taken into account. The power output and efficiency of the cycle are expressed as functions of temperatures of the working substance and the heat sources, heat transfer coefficients, pressure ratio, regenerator effectiveness, and total heat transfer area including the heat transfer areas of the regenerator and other heat exchangers. The regenerative criteria are given. The power output is optimized for a given efficiency. The general optimal performance characteristics of the cycle are revealed. The optimal performance of the Brayton heat engines with and without regeneration is compared quantitatively. The advantages of using the regenerator are expounded. Some important parameters of an irreversible regenerative Brayton heat engine, such as the temperatures of the working substance at different states, pressure ratio, maximum value of the pressure ratio, regenerator effectiveness and ratios of the various heat transfer areas to the total heat transfer area of the cycle, are further optimized. The optimal relations between these parameters and the efficiency of the cycle are presented by a set of characteristic curves for some assumed compression and expansion efficiencies. The results obtained may be helpful to the comprehensive understanding of the optimal performance of the Brayton heat engines with and without regeneration and play a theoretical instructive role for the optimal design of a regenerative Brayton heat engine.

Investigation on the Performance Characteristic of a Solar-Driven Braysson Heat Engine With Multi-Irreversibilities

2009 ◽  
Author(s):  
Lan Mei Wu ◽  
Guo Xing Lin
Keyword(s):  
Heat Transfer ◽  
Solar Collector ◽  
Heat Engine ◽  
Transfer Mechanism ◽  
Heat Transfer Mechanism ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Heat Engines ◽  
Engine System ◽  
Internal Irreversibility

An irreversible solar-driven Braysson heat engine system is put forward, in which finite rate heat transfer with the radiation-convection mode from the solar collector to the heat engine and the convection mode from the heat engine to the heat sink, the radiation-convection heat loss from the solar collector to the ambience, the internal irreversibility due to nonisentropic processes in the expander and compressor devices are taken into account. On the basis of thermodynamic analysis method, the analytic expression between the overall efficiency of the solar-driven Braysson heat engine system and the operating temperature of the solar collector is derived and the influences of different heat transfer mechanism, the internal irreversibility parameter, the isobaric temperature ratio, the ratio of heat-transfer coefficients on the optimal performance of the solar-driven Braysson heat engine system are evaluated and depicted quantificationally. The results obtained in the present paper are helpful to deeply reveal the effect of heat transfer mechanism and multi-irreversibilities on the performance of solar driven heat engines.

scholarly journals COMPARISON OF EFFICIENCY OF A SOLAR DRIVEN CARNOT ENGINE UNDER MAXIMUM POWER AND POWER DENSITY CONDITIONS

2015 ◽  
pp. 225-231
Author(s):  
Abhijit Sinha ◽  
Agnimitra Biswas ◽  
Kaushal Kumar Sharma
Keyword(s):  
Heat Transfer ◽  
Power Density ◽  
Heat Engine ◽  
Extreme Temperature ◽  
Maximum Power ◽  
Design Parameters ◽  
Thermodynamic Efficiency ◽  
Power Functions ◽  
Radiation Mode ◽  
Internal Irreversibility

A comparative analysis on thermodynamic efficiency based on maximum power & power density conditions have been performed for a solar-driven Carnot heat engine with internal irreversibility. In this analysis, the heat transfer from the hot reservoir is to be in the radiation mode and the heat transfer to the cold reservoir is to be in the convection mode. The thermodynamic efficiency function, power & power density functions have been derived and maximization of the power functions have been performed for various design parameters. From the optimum conditions, the thermal efficiencies at maximum power and power densities have been obtained. The effects of internal irreversibility, extreme temperature ratios & specific engine size in area ratio between the hot & cold reservoirs as various design parameters on thermodynamic efficiencies have been investigated for both the conditions. The efficiencies have been compared with Curzon- Ahlborn & Carnot efficiencies respectively. The analysis showed that the efficiency at maximum power output is greater than the efficiency at maximum power density. And the efficiencies can be greater than the Curzon- Ahlborn`s efficiency only for low values of design parameters.

Finite-Time Thermodynamics and Endoreversible Heat Engines

1993 ◽  
Vol 21 (4) ◽  
pp. 337-346 ◽  
Author(s):  
C. Wu ◽  
R. L. Kiang ◽  
V. J. Lopardo ◽  
G. N. Karpouzian
Keyword(s):  
Heat Transfer ◽  
Finite Time ◽  
Heat Engine ◽  
Power Production ◽  
Maximum Power ◽  
The Other ◽  
Finite Time Thermodynamics ◽  
Equilibrium Time ◽  
Heat Engines ◽  
Maximum Value

An endoreversible heat engine is an internally reversible and externally irreversible cyclic device which exchanges heat and power with its surroundings. Classical engineering thermodynamics is based on the concept of equilibrium. Time is not considered in the energy interactions between the heat engine and its environment. On the other hand, although rate of energy transfer is taught in heat transfer, the course does not cover heat engines. The finite-time thermodynamics is a newly developing field to fill in the gap between thermodynamics and heat transfer. Two types of engines are modelled in this paper—a reciprocating and a steady flow—with results obtained for maximum power output and efficiency at maximum power. It is shown that the latter is the same for both types of engines but that the maximum value of power production is different.

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