scholarly journals Effect of core flow heat transfer enhancement on power generation characteristics of thermoelectric generators with different performances

2021 ◽  
pp. 184-184
Author(s):  
Yanzhe Li ◽  
Shixue Wang ◽  
Yunchi Fu ◽  
Yulong Zhao ◽  
Like Yue
Keyword(s):  
Heat Transfer ◽  
Power Generation ◽  
Figure Of Merit ◽  
Thermoelectric Generator ◽  
Metal Foam ◽  
Maximum Output ◽  
Thermoelectric Generators ◽  
Core Flow ◽  
Gas Channel ◽  
The Core

In this study, the effect of enhancing the core flow heat transfer with metal foam on the performance of thermoelectric generators with different power generation characteristics is studied experimentally. Filling the core flow area of the gas channel in a thermoelectric generator with metal foam can greatly improve the heat transfer capacity of the gas channel with a small pressure loss, thereby improving the power generation efficiency. The results show that, first, the heat transfer enhancement achieved by partially filling the core area of the gas channel with metal foam can significantly improve the performance of thermoelectric generators, the maximum output power is about 1.5 times higher than that of the unfilled channel. Second, for a thermoelectric generator with different modules, the friction coefficient for different filling ratios increases by about 16 times at most, while the Nu value increases by only three times at most, and according to the PEC of the gas channel, metal foam with high filling rate and low pore density is more suitable for the thermoelectric generator. Third, it is more appropriate to use the thermoelectric module with a high figure of merit as the selection criterion for deciding whether to adopt the technique of enhancing heat exchange through the gas channel. The maximum output power and efficiency of the thermoelectric generator using the high figure of merit module are 300% and 160% higher than those of the thermoelectric generator using the low figure of merit module, respectively.

Boiling Heat Transfer From an Oscillated Water Column Through a Porous Domain: A Simplified Thermodynamic Analysis

2016 ◽  
Author(s):  
Ersin Sayar
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Water Column ◽  
Thermodynamic Analysis ◽  
Bubbly Flow ◽  
Pool Boiling ◽  
Oscillating Flow ◽  
Transition Regime ◽  
Core Flow ◽  
The Core

Heat transfer in an oscillating water column in the transition regime of pool boiling to bubbly flow is investigated experimentally and theoretically. Forced oscillations are applied to water via a frequency controlled dc motor and a piston-cylinder device. Heat transfer is from the electrically heated inner surface to the reciprocating flow. The heat transfer in the oscillating fluid column is altered by using stainless steel scrap metal layers (made off open-cell discrete cells) which produces a porous medium within the system. The effective heat transfer mechanism is enhanced and it is due to the hydrodynamic mixing of the boundary layer and the core flow. In oscillating flow, the hydrodynamic lag between the core flow and the boundary layer flow is somehow significant. At low actuation frequencies and at low heat fluxes, heat transfer is restricted in the single phase flows. The transition regime of pool boiling to bubbly flow is proposed to be a remedy to the stated limitation. The contribution by the pool boiling on heat transfer appears to be the dominant mechanism for the selected low oscillation amplitudes and frequencies. Accordingly the regime is a transition from pool boiling to bubbly flow. Nucleate-bubbly flow boiling in oscillating flow is also investigated using a simplified thermodynamic analysis. According to the experimental results, bubbles induce highly efficient heat transfer mechanisms. Experimental study proved that the heater surface temperature is the dominant parameter affecting heat transfer. At greater actuation frequencies saturated nucleate pool boiling ceases to exist. Actuation frequency becomes important in that circumstances. The present investigation has possible applications in moderate sized wicked heat pipes, boilers, compact heat exchangers and steam generators.

Revisit of Thermoelectric Efficiency and Figure-of-Merit

2014 ◽  
Vol 787 ◽  
pp. 195-197
Author(s):  
Chun Lei Wang ◽  
Yuan Hu Zhu ◽  
Wen Bin Su ◽  
Jian Liu ◽  
Ji Chao Li
Keyword(s):  
Power Generation ◽  
Power Factor ◽  
Power Output ◽  
Figure Of Merit ◽  
Maximum Output Power ◽  
Load Resistance ◽  
Maximum Output ◽  
Thermoelectric Efficiency ◽  
Physical Boundary ◽  
Thermoelectric Parameters

Thermoelectric efficiency power generation represented based on the transportation equations obtained under different physical boundary conditions in the present investigation. The figure-of-merit and power factor derived from optimizing thermoelectric efficiency and maximizing power output. It is interesting to note that the maximum output power reached when the load resistance was the thermoelectric adiabatic resistance, while the optimized thermoelectric efficiency responded the isothermal resistance. The possible approach to characterizing these thermoelectric parameters proposed in the present investigation.

scholarly journals Performance evaluation of thermoelectric generators under cyclic heating

2021 ◽  
Vol 2116 (1) ◽  
pp. 012087
Author(s):  
N P Williams ◽  
L Roumen ◽  
G McCauley ◽  
S M O’Shaughnessy
Keyword(s):  
Figure Of Merit ◽  
Thermoelectric Generator ◽  
Crack Formation ◽  
Internal Resistance ◽  
Thermoelectric Generators ◽  
Cyclic Heating ◽  
Material Interface ◽  
Internal Damage ◽  
Dimensionless Figure Of Merit ◽  
Power Outputs

Abstract The effect of thermal cycling on thermoelectric generator (TEG) performance is investigated for six nominally identical samples subjected to the same heating cycle profile. All TEGs experienced performance degradation, with maximum power outputs between 28 % and 49 % of pre-cycling values and a post-cycling decrease in the dimensionless figure of merit ZT of 21 % to 49 %. Sudden significant power reductions and subsequent internal resistance increases were observed for all samples, indicative of internal damage to the structure of the TEGs arising from material interface separation and micro-crack formation.

Unsteady Flow/Quasi-Steady Heat Transfer Computations on a Turbine Rotor and Comparison With Experiments

2001 ◽  
Vol 124 (1) ◽  
pp. 152-159 ◽  
Author(s):  
T. Korakianitis ◽  
P. Papagiannidis ◽  
N. E. Vlachopoulos
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Unsteady Flow ◽  
Turbine Rotor ◽  
Frequency Parameter ◽  
Unsteady Heat Transfer ◽  
Core Flow ◽  
The Core ◽  
Reduced Frequency ◽  
Steady Heat

The unsteady flow in stator–rotor interactions affects the structural integrity, aerodynamic performance of the stages, and blade-surface heat transfer. Numerous viscous and inviscid computer programs are used for the prediction of unsteady flows in two-dimensional and three-dimensional stator–rotor interactions. The relative effects of the various components of flow unsteadiness on heat transfer are under investigation. In this paper it is shown that for subsonic cases, the reduced frequency parameter for boundary-layer calculations is about two orders of magnitude smaller than the reduced frequency parameter for the core flow. This means that for typical stator–rotor interactions, the unsteady flow terms are needed to resolve the location of disturbances in the core flow, but in many cases the instantaneous disturbances can be input in steady-flow boundary-layer computations to evaluate boundary-layer effects in a quasi-steady approximation. This hypothesis is tested by comparing computations with experimental data on a turbine rotor for which there are extensive experimental heat transfer data available in the open literature. An unsteady compressible inviscid two-dimensional computer program is used to predict the propagation of the upstream stator disturbances into the downstream rotor passages. The viscous wake (velocity defect) and potential flow (pressure fluctuation) perturbations from the upstream stator are modeled at the computational rotor–inlet boundary. The effects of these interactions on the unsteady rotor flow result in computed instantaneous velocity and pressure fields. The period of the rotor unsteadiness is one stator pitch. The instantaneous velocity fields on the rotor surfaces are input in a steady-flow differential boundary-layer program, which is used to compute the instantaneous heat transfer rate on the rotor blades. The results of these quasi-steady heat-transfer computations are compared with the results of unsteady heat transfer experiments and with the results of previous unsteady heat transfer computations. The unsteady flow fields explain the unsteady amplitudes and phases of the increases and decreases in instantaneous heat transfer rate. It is concluded that the present method is accurate for quantitative predictions of unsteady heat transfer in subsonic turbine flows.

DESIGN AND CONSTRUCTION OF A SIMPLE THERMOELECTRIC GENERATOR HEAT EXCHANGER FOR POWER GENERATION FROM SALINITY GRADIENT SOLAR POND

2015 ◽  
Vol 76 (5) ◽  
Author(s):  
Baljit Singh ◽  
Altenaijy Saoud ◽  
Muhammed Fairuz Remeli ◽  
Lai Chet Ding ◽  
Abhijit Date ◽  
...  
Keyword(s):  
Power Generation ◽  
Heat Exchanger ◽  
Thermal Energy ◽  
Thermoelectric Generator ◽  
Salinity Gradient ◽  
Electrical Power ◽  
Thermoelectric Generators ◽  
Lower Zone ◽  
Solar Pond ◽  
Electrical Power Output

Solar pond is one source of renewable thermal energy. The solar pond collects and stores thermal energy at the lower zone of the solar pond. The temperature at the lower zone can reach up to 90 °C. The solar pond is capable storing thermal energy for a long period. The stored thermal energy can be converted into electricity by using thermoelectric generators. These thermoelectric generators can be operated using the cold and hot zones from a solar pond. In this paper, the experimental investigation of power generation from the solar pond using thermoelectric generator and simple heat exchanger is discussed. A maximum of 7.02 W of electrical power output was obtained from a simple heat exchanger with 40 thermoelectric modules.

Unsteady-Flow/Quasi-Steady Heat Transfer Computations on a Turbine Rotor and Comparison With Experiments

1993 ◽  
Author(s):  
T. Korakianitis ◽  
P. Papagiannidis ◽  
N. E. Vlachopoulos
Keyword(s):  
Heat Transfer ◽  
Boundary Layer ◽  
Unsteady Flow ◽  
Turbine Rotor ◽  
Frequency Parameter ◽  
Unsteady Heat Transfer ◽  
Core Flow ◽  
The Core ◽  
Reduced Frequency ◽  
Steady Heat

The unsteady flow in stator-rotor interactions affects the structural integrity, aerodynamic performance of the cascades, and blade-surface heat transfer. Numerous viscous and inviscid computer programs are currently becoming available for the prediction of unsteady flows in two-dimensional and three-dimensional stator-rotor interactions. The relative effects of the various components of flow unsteadiness on heat transfer are currently under investigation. In this paper it is shown that for subsonic cases the reduced frequency parameter for boundary-layer calculations is about two orders of magnitude smaller than the reduced frequency parameter for the core flow. This means that for typical stator-rotor interactions the unsteady flow terms are needed to resolve the location of disturbances in the core flow, but in many cases the instantaneous disturbances can be input in steady-flow boundary-layer computations to evaluate boundary-layer effects in a quasi-steady approximation. This hypothesis is tested by comparing computations with experimental data on a turbine rotor for which there is extensive experimental heat-transfer data available in the open literature. An unsteady compressible inviscid two-dimensional computer program is used to predict the propagation of the upstream stator disturbances into the downstream rotor passages. The viscous wake (velocity defect) and potential flow (pressure fluctuation) perturbations from the upstream stator are modeled at the computational rotor-inlet boundary. The effects of these interactions on the unsteady rotor flow result in computed instantaneous velocity and pressure fields. The period of the rotor unsteadiness is one stator pitch. The instantaneous velocity fields on the rotor surfaces are input in a steady-flow differential boundary-layer program, which is used to compute the instantaneous heat-transfer rate on the rotor blades. The results of these quasi-steady heat-transfer computations are compared with the results of unsteady heat-transfer experiments and with the results of previous unsteady heat-transfer computations. The unsteady flow fields explain the unsteady amplitudes and phases of the increases and decreases in instantaneous heat-transfer rate. It is concluded that the present method is accurate for quantitative predictions of unsteady heat transfer in subsonic turbine flows.

Finite Element Simulation of Micro-Thermoelectric Generators Based on Microporous Glass Template

2020 ◽  
Vol 861 ◽  
pp. 499-508
Author(s):  
Fu Li ◽  
Bo Li ◽  
Ning Su
Keyword(s):  
Power Generation ◽  
Finite Element ◽  
Performance Test ◽  
Maximum Output Power ◽  
Electrical Potential ◽  
Maximum Output ◽  
Thermoelectric Generators ◽  
Element Analysis ◽  
Microporous Glass ◽  
Power Generation Performance

COMSOL Multiphysics software-based three-dimensional finite element analysis is widely used in the performance simulation of thermoelectric devices. In this study, this software is used to simulate the heat transfer processes and power generation performance of micro-thermoelectric generators based on a microporous glass template. The temperature and electrical potential fields are coupled to each other through the thermoelectric effects during the calculations. The power generation performances of micro-thermoelectric generators with different template heights (d) for various temperature differences between their hot and cold ends (∆Th-c) are calculated. For the micro-thermoelectric generator that included four pairs of TE couples, the temperature difference between the two sides of the TE columns (∆TTE) and the open circuit voltage (Uoc) both increased with increasing d, but the growth rate gradually decreased. When d is greater than 0.2 mm, the increment basically becomes negligible. The maximum output power (Pmax) first increases and then decreases with increasing d, reaching a maximum value when d is 0.2 mm. Therefore, we can optimize the size of device according to the simulation results to ensure that the device produces the optimal output performance during the experiments. A model with the same parameters used in the experiment (i.e., d=0.2 mm) was then established and it generated a Uoc of 35.2 mV and a Pmax of 228.8 μW when ∆Th-c was 107.5 K (∆TTE = 97.55 K). The errors between the simulation and the experimental results are small and thus also verify the accuracy of the power generation performance test results.

An Efficiency Entitlement Study for Thermoelectric Generators

2007 ◽  
Author(s):  
H. Peter J. De Bock ◽  
Vladimir Novak
Keyword(s):  
Power Generation ◽  
Thermoelectric Power ◽  
Material Properties ◽  
Thermoelectric Generator ◽  
Operating Conditions ◽  
Thermoelectric Generators ◽  
Thermoelectric Power Generation ◽  
Closed Form Solutions ◽  
Recent Developments ◽  
System Operating

Recent developments in thermoelectric materials and systems have led to renewed interest in thermoelectric devices for power generation. Operating conditions of the heat source and heat sink are essential in evaluating the conversion efficiency of such thermoelectric generator systems. This study provides a method for evaluating efficiency entitlement for thermoelectric power generation when thermoelectric material properties and system operating conditions are specified. The efficiency entitlement in closed form solutions for the most commonly used thermoelectric power generation configurations are presented followed by results and discussion.

Heat-Exchanger Effectiveness in Thermoelectric Power Generation

1981 ◽  
Vol 103 (4) ◽  
pp. 693-698 ◽  
Author(s):  
M. S. Bohn
Keyword(s):  
Heat Transfer ◽  
Power Generation ◽  
Heat Exchanger ◽  
Thermoelectric Power ◽  
Thermoelectric Generator ◽  
Electrical Power ◽  
Thermoelectric Power Generation ◽  
Cold Fluid ◽  
Thermoelectric Heat ◽  
Two Fluid

This paper presents a method for calculating the electrical power generated by a thermoelectric heat exchanger. The thermoelectric heat exchanger transfers heat from a hot fluid to a cold fluid through a thermoelectric generator located in the heat-exchanger wall separating the two fluid streams. The method presented here is an extension of the NTU method used to calculate heat-exchanger heat-transfer effectiveness. The effectiveness of thermoelectric power generation is expressed as the ratio of the actual power generated to the power that would be generated if the entire heat-exchanger area were operating at the inlet fluid temperatures. This method collapses results for several heat-exchanger configurations and allows a concise presentation of the results. It is shown that the NTU method of calculating heat-exchanger heat-transfer effectiveness can be modified in a similar way.

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