Thermal-Flow Analysis of a Simple LTD (Low-Temperature-Differential) Heat Engine

Kim, Yeongmin; Chun, Wongee; Chen, Kuan

doi:10.3390/en10040567

Cited by 8 publications

(6 citation statements)

References 11 publications

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“…The source of power of the Stirling engine is the pressure gradient in air room, which is formed because of the difference in the temperature of the cold and hot plates. In this section, we refer to the method of Kim et al to calculate the gas work of the Stirling engine [8]. Because of the low speed and small size of the gamma-type Stirling engine, the airflow in the air room can be reasonably assumed to be laminar.…”

Section: Gas Workmentioning

confidence: 99%

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An Analysis Model Combining Gamma-Type Stirling Engine and Power Converter

Shih

2019

Energies

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Waste heat is a potential source for powering our living environment. It can be harvested and transformed into electricity. Ohmic heat is a common type of waste heat. However, waste heat has the following limitations: wide distribution, insufficient temperature difference (ΔT < 70 K) for triggering turbines, and producing voltage below the open voltage of the battery. This paper proposes an energy harvester model that combines a gamma-type Stirling engine and variable capacitance. The energy harvester model is different from Tavakolpour-Saleh’s free-piston-type engine [7.1 W at ΔT = 407 K (273–680 K)]. The gamma-type Stirling engine is a low-temperature-difference engine. It can be triggered by a minimum ΔT value of 12 K (293–305 K). The triggering force in the variable capacitance is almost zero. Furthermore, the gamma-type Stirling engine is suitable for harvesting waste heat at room temperature. This study indicates that 21 mW of energy can be produced at ΔT = 30 K (293–323 K) for a bias voltage of 70 V and volume of 103.25 cc. Because of the given bias voltage, the energy harvester can break through the open voltage of the battery to achieve energy storage at a low temperature difference.

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Section: Gas Workmentioning

confidence: 99%

“…However, a variety of instantaneous pressures should be considered in reality. Kim et al used thermal flow to analyze high and low pressures in an LTD Stirling engine [8].…”

Section: Introductionmentioning

confidence: 99%

An Analysis Model Combining Gamma-Type Stirling Engine and Power Converter

Shih

2019

Energies

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“…10 Their research focused on the use of large-scale thermoelectric refrigerator for the air conditioning applications. Kim et al 11 suggested a combined thermal-flow analysis of a simple low-temperature-differential (LTD) heat engine to utilize lowgrade waste heat from the industries. In harvesting mechanical energy from the waste heat, Sato et al 12 demonstrated a functional shape memory alloy (SMA) heat engine that produced 1.16 W of electrical power at a temperature of 100°C.…”

Section: Introductionmentioning

confidence: 99%

Power generation by a thermomagnetic engine by hybrid operation of an electromagnetic generator and a triboelectric nanogenerator

et al. 2019

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Summary This paper reports a thermomagnetic generator based on the magneto‐caloric effect of Gadolinium to scavenge low‐grade thermal energy and its eventual conversion into electrical energy. Gadolinium is one of the distinct materials whose Curie temperature is nearly room temperature. For this reason, a Gadolinium‐based thermomagnetic engine offers enormous possibilities to harness available waste heat from the industries. In this work, the performance of an electromagnetic generator (EMG) coupled with a triboelectric nanogenerator (TENG) was experimentally investigated as it is driven by a thermomagnetic engine exploiting low temperature waste heat. At the temperature difference of 46.5°C between the hot and cold water jets, the thermomagnetic engine produced an average rotational speed of 263 ± 1.5% rpm and a mechanical output power of 76.38 ± 0.5% mW. At the aforementioned rotational speed, the hybrid generator delivered a rectified peak voltage of 15.34 V on an open‐circuit, a short‐circuit current of 20.1 mA, and the largest power output, 12.1 mW, at a 120 Ω load. It was demonstrated that the proposed energy harvester could light dozens of light‐emitting diodes or power a digital thermometer. It is feasible that the proposed thermomagnetic generator can be utilized as an effective power source for various applications.

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“…Stirling engines have high theoretical efficiencies and can be powered by external heat sources; therefore, there is a high degree of potential for Stirling engines to produce renewable energy from several sustainable sources, such as concentrated solar thermal power and biomass. Theoretically, Stirling engines can convert heat into mechanical energy at the Carnot efficiency [1,2], which is the maximum achievable efficiency for heat engines, but in practice Stirling engines have failed to achieve these high efficiencies and the reduction is more than would be predicted by typical mechanical losses alone [3]. The practical efficiency depends on many factors, including the operating conditions, regenerator effectiveness [4], friction losses [5,6], dead volume [7], and the ability of the engine to follow the theoretical Stirling cycle.…”

Section: Introductionmentioning

confidence: 99%

Efficiency Reduction in Stirling Engines Resulting from Sinusoidal Motion

2018

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Stirling engines have a high potential to produce renewable energy due to their ability to use a wide range of sustainable heat sources, such as concentrated solar thermal power and biomass, and also due to their high theoretical efficiencies. They have not yet achieved widespread use and commercial Stirling engines have had reduced efficiencies compared to their ideal values. In this work we show that a substantial amount of the reduction in efficiency is due to the operation of Stirling engines using sinusoidal motion and quantify this reduction. A discrete model was developed to perform an isothermal analysis of a 100cc alpha-type Stirling engine with a 90 ∘ phase angle offset, to demonstrate the impact of sinusoidal motion on the net work and thermal efficiency in comparison to the ideal cycle. For the specific engine analyzed, the maximum thermal efficiency of the sinusoidal cycle was found to have a limit of 34.4%, which is a reduction of 27.1% from Carnot efficiency. The net work of the sinusoidal cycle was found to be 65.9% of the net work from the ideal cycle. The model was adapted to analyze beta and gamma-type Stirling configurations, and the analysis revealed similar reductions due to sinusoidal motion.

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Thermal-Flow Analysis of a Simple LTD (Low-Temperature-Differential) Heat Engine

Cited by 8 publications

References 11 publications

An Analysis Model Combining Gamma-Type Stirling Engine and Power Converter

An Analysis Model Combining Gamma-Type Stirling Engine and Power Converter

Power generation by a thermomagnetic engine by hybrid operation of an electromagnetic generator and a triboelectric nanogenerator

Efficiency Reduction in Stirling Engines Resulting from Sinusoidal Motion

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