scholarly journals Harvesting Nanoscale Thermal Radiation Using Pyroelectric Materials

2010 ◽  
Vol 132 (9) ◽  
Author(s):  
Jin Fang ◽  
Hugo Frederich ◽  
Laurent Pilon
Keyword(s):  
Heat Transfer ◽  
Thermal Radiation ◽  
Energy Conversion ◽  
Power Output ◽  
Radiative Heat ◽  
Vinylidene Fluoride ◽  
Waste Heat ◽  
Heat Fluxes ◽  
Working Fluid ◽  
New Device

Pyroelectric energy conversion offers a way to convert waste heat directly into electricity. It makes use of the pyroelectric effect to create a flow of charge to or from the surface of a material as a result of heating or cooling. However, an existing pyroelectric energy converter can only operate at low frequencies due to a relatively small convective heat transfer rate between the pyroelectric materials and the working fluid. On the other hand, energy transfer by thermal radiation between two semi-infinite solids is nearly instantaneous and can be enhanced by several orders of magnitude from the conventional Stefan–Boltzmann law as the gap separating them becomes smaller than Wien’s displacement wavelength. This paper explores a novel way to harvest waste heat by combining pyroelectric energy conversion and nanoscale thermal radiation. A new device was investigated numerically by accurately modeling nanoscale radiative heat transfer between a pyroelectric element and hot and cold plates. Silica absorbing layers on top of every surface were used to further increase the net radiative heat fluxes. Temperature oscillations with time and performances of the pyroelectric converter were predicted at various frequencies. The device using 60/40 porous poly(vinylidene fluoride–trifluoroethylene) achieved a 0.2% efficiency and a 0.84 mW/cm2 electrical power output for the cold and hot sources at 273 K and 388 K, respectively. Better performances could be achieved with 0.9Pb(Mg1/3Nb2/3)–0.1PbTiO3 (0.9PMN-PT), namely, an efficiency of 1.3% and a power output of 6.5 mW/cm2 between the cold and hot sources at 283 K and 383 K, respectively. These results are compared with alternative technologies, and suggestions are made to further improve the device.

Harvesting Nanoscale Radiation Heat Transfer With Pyroelectric Materials

2009 ◽  
Author(s):  
Jin Fang ◽  
Hugo Frederich ◽  
Laurent Pilon
Keyword(s):  
Heat Transfer ◽  
Energy Transfer ◽  
Energy Conversion ◽  
Electromagnetic Waves ◽  
Waste Heat ◽  
Radiation Heat Transfer ◽  
Low Frequency ◽  
Working Fluid ◽  
Radiation Heat ◽  
New Device

Pyroelectric energy conversion offers a novel, direct energy-conversion technology by transforming time-dependent temperature directly into electricity. It makes use of the pyroelectric effect to create a flow of charge to or from the surface of a material as a result of heating or cooling. However, existing pyroelectric energy converter can only operate at low frequency due to relatively low heat transfer rate between the pyroelectric materials and the working fluid subjected to oscillatory fluid flow between hot and cold sources. On the other hand, energy transfer by thermal radiation between two semi-infinite solids can be enhanced by several orders of magnitude as the gap separating them reduces to subwavelength size thanks to interference and tunneling of electromagnetic waves across the gap. This paper proposes a novel way to harvest nanoscale radiation heat transfer for direct pyroelectric energy conversion of waste heat into electricity. A new device is investigated numerically by accurately modeling nanoscale radiation heat transfer between the pyroelectric materials and hot and cold surfaces. Performance of the pyroelectric converter is predicted at various frequencies. The result shows that rapid energy transfer and higher operating frequency can be achieved to increase efficiency and power density.

scholarly journals Effects of radiative heat transfer on the structure of turbulent supersonic channel flow

2011 ◽  
Vol 677 ◽  
pp. 417-444 ◽  
Author(s):  
S. GHOSH ◽  
R. FRIEDRICH ◽  
M. PFITZNER ◽  
CHR. STEMMER ◽  
B. CUENOT ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Radiation ◽  
Radiative Heat Transfer ◽  
Radiation Effects ◽  
Radiative Heat ◽  
Pure Water ◽  
Molecular Transport ◽  
Working Fluid ◽  
Mean Flow ◽  
Total Energy Balance

The interaction between turbulence in a minimal supersonic channel and radiative heat transfer is studied using large-eddy simulation. The working fluid is pure water vapour with temperature-dependent specific heats and molecular transport coefficients. Its line spectra properties are represented with a statistical narrow-band correlated-k model. A grey gas model is also tested. The parallel no-slip channel walls are treated as black surfaces concerning thermal radiation and are kept at a constant temperature of 1000 K. Simulations have been performed for different optical thicknesses (based on the Planck mean absorption coefficient) and different Mach numbers. Results for the mean flow variables, Reynolds stresses and certain terms of their transport equations indicate that thermal radiation effects counteract compressibility (Mach number) effects. An analysis of the total energy balance reveals the importance of radiative heat transfer, compared to the turbulent and mean molecular heat transport.

Organic Rankine Cycle Working Fluid Selection and Performance Analysis for Combined Application With a 2 MW Class Industrial Gas Turbine

2014 ◽  
Author(s):  
Karsten Kusterer ◽  
René Braun ◽  
Dieter Bohn
Keyword(s):  
Heat Source ◽  
Energy Conversion ◽  
Gas Turbine ◽  
Power Output ◽  
Waste Heat ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Combined Cycle ◽  
Working Fluid ◽  
Combined Operation

The selection of suitable working fluids for use in Organic Rankine Cycles (ORC) is strongly addicted to the intended application of the ORC system. The design of the ORC, the kind of heat source and the ambient condition has an influence on the performance of the Organic Rankine Cycle and on the selection of the working fluid. It can come to a discrepancy between the best candidate from the thermodynamic point of view and the transformation into a real machine design. If an axial turbine design is considered for expansion and energy conversion within the ORC, the vapor volume flow ratios within the expansion path, the pressure ratio and of course the number of stages have to be considered within the fluid selection process and for the design parameters. Furthermore, environmental aspects have to be taken into account, e.g. the global warming potential (GWP) and the flammability of the selected fluid. This paper shows the results of the design and fluid selection process for an Organic Rankine Cycle for application in a combined operation with a 2MW class industrial gas turbine. The gas turbine contains two radial compressor stages with an integrated intercooler. To further increase the thermal cycle efficiency, a recuperator has been implemented to the gas turbine cycle, which uses the exhaust gas waste heat to preheat the compressed air after the second compressor, before it enters the combustion chamber. The shaft power is generated by a three stage axial turbine, whereby the first stage is a convection cooled stage, due to a turbine inlet temperature of 1100°C. To further increase the electrical efficiency and the power output of the energy conversion cycle, a combined operation with an organic Rankine cycle is intended. Therefore the waste heat from the GT compressor intercooler is used as first heat source and the waste heat of the exhaust gas after the recuperator as second heat source for the Organic Rankine Cycle. It is intended that the ORC fluid acts as heat absorption fluid within the compressor intercooler. Due to these specifications for the ORC, a detailed thermodynamic analysis has been performed to determine the optimal design parameter and the best working fluid for the ORC, in order to obtain a maximum power output of the combined cycle. Due to the twice coupling of the ORC to the GT cycle, the heat exchange between the two cycles is bounded by each other and a detailed analysis of the coupled cycles is necessary. E.g. the ambient temperature has an enormous influence on the transferred heat from the intercooler to the ORC cycle, which itself affects the heat transfer and temperatures of the transferable heat from the second heat source. Thus, a detailed analysis by considering the ambient operation conditions has been performed, in order to provide a most efficient energy conversion system over a wide operation range. The performance analysis has shown that by application of an ORC for a combined operation with the intercooled and recuperated gas turbine, the combined cycle efficiency can be increased, for a wide ambient conditions range, by more than 3 %pts. and the electrical power output by more than 10 %, in comparison to the stand alone intercooled and recuperated gas turbine.

Waste Heat Recovery in a Cruise Vessel in the Baltic Sea by Using an Organic Rankine Cycle: A Case Study

2015 ◽  
Author(s):  
Fredrik Ahlgren ◽  
Maria E. Mondejar ◽  
Magnus Genrup ◽  
Marcus Thern
Keyword(s):  
Power Output ◽  
Heat Recovery ◽  
Waste Heat Recovery ◽  
Waste Heat ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Operating Conditions ◽  
Maritime Transportation ◽  
Working Fluid ◽  
Net Power Output

Maritime transportation is a significant contributor to SOx, NOx and particle matter emissions, even though it has a quite low CO2 impact. New regulations are being enforced in special areas that limit the amount of emissions from the ships. This fact, together with the high fuel prices, is driving the marine industry towards the improvement of the energy efficiency of current ship engines and the reduction of their energy demand. Although more sophisticated and complex engine designs can improve significantly the efficiency of the energy systems in ships, waste heat recovery arises as the most influent technique for the reduction of the energy consumption. In this sense, it is estimated that around 50% of the total energy from the fuel consumed in a ship is wasted and rejected in fluid and exhaust gas streams. The primary heat sources for waste heat recovery are the engine exhaust and the engine coolant. In this work, we present a study on the integration of an organic Rankine cycle (ORC) in an existing ship, for the recovery of the main and auxiliary engines exhaust heat. Experimental data from the operating conditions of the engines on the M/S Birka Stockholm cruise ship were logged during a port-to-port cruise from Stockholm to Mariehamn over a period of time close to one month. The ship has four main engines Wärtsilä 5850 kW for propulsion, and four auxiliary engines 2760 kW used for electrical consumers. A number of six load conditions were identified depending on the vessel speed. The speed range from 12–14 knots was considered as the design condition, as it was present during more than 34% of the time. In this study, the average values of the engines exhaust temperatures and mass flow rates, for each load case, were used as inputs for a model of an ORC. The main parameters of the ORC, including working fluid and turbine configuration, were optimized based on the criteria of maximum net power output and compactness of the installation components. Results from the study showed that an ORC with internal regeneration using benzene would yield the greatest average net power output over the operating time. For this situation, the power production of the ORC would represent about 22% of the total electricity consumption on board. These data confirmed the ORC as a feasible and promising technology for the reduction of fuel consumption and CO2 emissions of existing ships.

Calculation and Optimization of Heat Transfer between the Low Exergy Heat Source and Organic Rankine Cycle Applied to Heat Recovery Systems

2013 ◽  
Vol 597 ◽  
pp. 45-50
Author(s):  
Sławomir Smoleń ◽  
Hendrik Boertz
Keyword(s):  
Heat Transfer ◽  
Heat Source ◽  
Heat Recovery ◽  
Power Plants ◽  
Waste Heat ◽  
Organic Rankine Cycle ◽  
Optimization Procedure ◽  
Rankine Cycle ◽  
Working Fluid ◽  
Total System

One of the key challenges on the area of energy engineering is the system development for increasing the efficiency of primary energy conversion and use. An effective and important measure suitable for improving efficiencies of existing applications and allowing the extraction of energy from previously unsuitable sources is the Organic Rankine Cycle. Applications based on this cycle allow the use of low temperature energy sources such as waste heat from industrial applications, geothermal sources, biomass, fired power plants and micro combined heat and power systems.Working fluid selection is a major step in designing heat recovery systems based on the Organic Rankine Cycle. Within the framework of the previous original study a special tool has been elaborated in order to compare the influence of different working fluids on performance of an ORC heat recovery power plant installation. A database of a number of organic fluids has been developed. The elaborated tool should create a support by choosing an optimal working fluid for special applications and become a part of a bigger optimization procedure by different frame conditions. The main sorting criterion for the fluids is the system efficiency (resulting from the thermo-physical characteristics) and beyond that the date base contains additional information and criteria, which have to be taken into account, like environmental characteristics for safety and practical considerations.The presented work focuses on the calculation and optimization procedure related to the coupling heat source – ORC cycle. This interface is (or can be) a big source of energy but especially exergy losses. That is why the optimization of the heat transfer between the heat source and the process is (besides the ORC efficiency) of essential importance for the total system efficiency.Within the presented work the general calculation approach and some representative calculation results have been given. This procedure is a part of a complex procedure and program for Working Fluid Selection for Organic Rankine Cycle Applied to Heat Recovery Systems.

scholarly journals Experimental Investigation of Embedded Micropin-Fins for Single-Phase Heat Transfer and Pressure Drop

2018 ◽  
Vol 140 (2) ◽  
Author(s):  
Chirag R. Kharangate ◽  
Ki Wook Jung ◽  
Sangwoo Jung ◽  
Daeyoung Kong ◽  
Joseph Schaadt ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Friction Factor ◽  
Integrated Circuit ◽  
Single Phase ◽  
Absolute Error ◽  
Heat Fluxes ◽  
Operating Conditions ◽  
Working Fluid ◽  
Pin Fin

Three-dimensional (3D) stacked integrated circuit (IC) chips offer significant performance improvement, but offer important challenges for thermal management including, for the case of microfluidic cooling, constraints on channel dimensions, and pressure drop. Here, we investigate heat transfer and pressure drop characteristics of a microfluidic cooling device with staggered pin-fin array arrangement with dimensions as follows: diameter D = 46.5 μm; spacing, S ∼ 100 μm; and height, H ∼ 110 μm. Deionized single-phase water with mass flow rates of m˙ = 15.1–64.1 g/min was used as the working fluid, corresponding to values of Re (based on pin fin diameter) from 23 to 135, where heat fluxes up to 141 W/cm2 are removed. The measurements yield local Nusselt numbers that vary little along the heated channel length and values for both the Nu and the friction factor do not agree well with most data for pin fin geometries in the literature. Two new correlations for the average Nusselt number (∼Re1.04) and Fanning friction factor (∼Re−0.52) are proposed that capture the heat transfer and pressure drop behavior for the geometric and operating conditions tested in this study with mean absolute error (MAE) of 4.9% and 1.7%, respectively. The work shows that a more comprehensive investigation is required on thermofluidic characterization of pin fin arrays with channel heights Hf < 150 μm and fin spacing S = 50–500 μm, respectively, with the Reynolds number, Re < 300.

Impact of Soot Radiative Properties, Pressure and Soot Volume Fraction on Radiative Heat Transfer in Turbulent Sooty Flames

2020 ◽  
Author(s):  
Kevin Torres Monclard ◽  
Olivier Gicquel ◽  
Ronan Vicquelin
Keyword(s):  
Heat Transfer ◽  
Thermal Radiation ◽  
Radiative Heat Transfer ◽  
Radiative Heat ◽  
Volume Fraction ◽  
Soot Volume Fraction ◽  
Turbulent Flames ◽  
Radiative Properties ◽  
Jet Flame ◽  
Soot Particles

Abstract The effect of soot radiation modeling, pressure, and level of soot volume fraction are investigated in two ethylene-air turbulent flames: a jet flame at atmospheric pressure studied at Sandia, and a confined pressurized flame studied at DLR. Both cases have previously been computed with large-eddy simulations coupled with thermal radiation. The present study aims at determining and analyzing the thermal radiation field for different models from these numerical results. A Monte-Carlo solver based on the Emission Reciprocity Method is used to solve the radiative transfer equation with detailed gas and soot properties in both configurations. The participating gases properties are described by an accurate narrowband ck model. Emission, absorption, and scattering from soot particles are accounted for. Two formulations of the soot refractive index are considered: a constant value and a wavelength formulation dependency. This is combined with different models for soot radiative properties: gray, Rayleigh theory, Rayleigh-Debye-Gans theory for fractal aggregates. The effects of soot radiative scattering is often neglected since their contribution is expected to be small. This contribution is determined quantitatively in different scenarios, showing great sensitivity to the soot particles morphology. For the same soot volume fraction, scattering from larger aggregates is found to modify the radiative heat transfer noticeably. Such a finding outlines the need for detailed information on soot particles. Finally, the role of soot volume fraction and pressure on radiative interactions between both solid and gaseous phases is investigated.

scholarly journals Parametric Optimization and Thermodynamic Performance Comparison of Organic Trans-Critical Cycle, Steam Flash Cycle, and Steam Dual-Pressure Cycle for Waste Heat Recovery

Energies ◽  
2019 ◽  
Vol 12 (24) ◽  
pp. 4623 ◽  
Author(s):  
Liya Ren ◽  
Huaixin Wang
Keyword(s):  
Heat Source ◽  
Power Output ◽  
Initial Temperature ◽  
Waste Heat ◽  
Cycle Performance ◽  
Working Fluid ◽  
Inlet Temperature ◽  
Thermodynamic Performance ◽  
Pressure Cycle ◽  
Net Power Output

Compared with the basic organic and steam Rankine cycles, the organic trans-critical cycle (OTC), steam flash cycle (SFC) and steam dual-pressure cycle (SDC) can be regarded as the improved cycle configurations for the waste heat power recovery since they can achieve better temperature matching between the heat source and working fluid in the heat addition process. This study investigates and compares the thermodynamic performance of the OTC, SFC, and SDC based on the waste heat source from the cement kiln with an initial temperature of 320 °C and mass flow rate of 86.2 kg/s. The effects of the main parameters on the cycle performance are analyzed and the parameter optimization is performed with net power output as the objective function. Results indicate that the maximum net power output of SDC is slightly higher than that of SFC and the OTC using n-pentane provides a 19.74% increase in net power output over the SDC since it can achieve the higher use of waste heat and higher turbine efficiency. However, the turbine inlet temperature of the OTC is limited by the thermal stability of the organic working fluid, hence the SDC outputs more power than that of the OTC when the initial temperature of the exhaust gas exceeds 415 °C.

CFD Modeling of Cogeneration Burner Applications and the Significance of Thermal Radiative Heat Transfer Effects

2003 ◽  
Author(s):  
A. F. Tenbusch
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Thermal Radiation ◽  
System Design ◽  
Radiative Heat Transfer ◽  
Radiative Heat ◽  
Flow Distribution ◽  
Cfd Modeling ◽  
Large Temperature ◽  
Flow Heat

Industrial burners provide process heat for a wide range of applications including cogeneration power production. In such applications a (typically) natural gas fired stationary turbine powers an electric generator and indirectly powers a heat recover steam generator (HRSG). The HRSG steam cycle operates by reclaiming the residual thermal energy of the gas turbine exhaust (GTE) flow. Burners are used to reheat the GTE and increase plant capacity during peak demand periods. CFD modeling is used in the design of burner systems for HRSG applications. GTE flow exiting the turbine unit is passed through a diffuser and then expanded into ductwork where the steam system heat exchangers are located. The expansion of the GTE flow from the turbine diffuser to the full cross section of the ductwork is usually severe and creates an uneven flow distribution. Flow correcting structure may be needed to distribute the flow depending upon the severity of the duct expansion. CFD modeling is used to predict the flow distribution of the GTE and guide the design of any necessary flow correcting structure. Burners are typically installed in an array upstream of the application heat exchanger inlet. CFD combustion, heat transfer, and flow analysis is employed in the burner system design process to locate the burner array, determine any necessary flow baffling, and to ensure and provide a uniform thermal distribution at the downstream heat exchanger inlet. Excessive thermal variation in the GTE flow entering the heat exchanger results in large temperature gradients that can lead to thermal cracking and fatigue of the heat exchanger surfaces. CFD modeling is used to ensure that the burner system design produces a uniform flow and temperature distribution at the heat exchanger inlet region downstream of the burners. This report presents a case study of a CFD flow, heat-transfer, and combustion analysis for a typical HRSG burner application. Two CFD models were constructed for the analysis. The first model included the coupled effects of flow, heat transfer, and combustion for the entire HRSG model volume, but excluded the effects of thermal radiation. The second model included a sub-domain of the HRSG volume near the burner and included the additional effects of thermal radiation, both surface radiation and the effects of the radiatively participating flue gas. Radiative effects were included in the second model by employing the Discrete Transfer Method. Results of the study showed the significant role thermal radiative heat transfer had on the resulting temperature predictions downstream of the flame zone.

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