Irreversible Factors Research Articles

Time dependent model to analyze the magnetic refrigeration performance of gadolinium near the room temperature

Abstract A practical time-dependent model has been constructed to forecast the effectiveness and productivity of a magnetic regenerative refrigerator, as well as to assess its cycle efficiency. The model incorporates many irreversible factors, including the cycle frequency, heat transfer efficiency, and heat leak. Furthermore, it is utilized to scrutinize a magnetic refrigerator that employs spherical Gd particles as the magnetic substance and water as the heat transfer medium. The different cycle steps of the magnetic refrigerator are examined, while the cooling capacity and temperature differential between the two heat exchangers are appraised. The results also show that the magnetic refrigerator can obtain a temperature span of 5 K under 0.8 T magnetic field after 30 cycles in a particular situation. The findings provide valuable information for the future planning and advancement of magnetic refrigeration technology at room temperature.

Anti‐fouling capacity enhancement of thin‐film composite polyamide membrane by chitosan graft polymerization methods

AbstractThis study aimed to improve the anti‐fouling properties of a thin‐film composite polyamide membrane by modifying it with chitosan and acrylic acid using UV‐induced and Redox‐initiated graft polymerization methods. The modified membrane's separation performance was evaluated by measuring the flux and retention of sodium ions in water during filtration. The anti‐fouling capacities of the modified membranes were determined by measuring the maintained flux ratios and irreversible fouling factors during the 8‐h filtration of aqueous solutions of sodium chloride at different concentrations (1000 and 10,000 ppm). In addition, by evaluating the membrane's surface properties using various methods, including field emission scanning electron microscopy, attenuated total reflection – Fourier transform infrared spectroscopy, and water contact angle measurements, we have demonstrated the validity of the experimental results. Our results showed that the grafted membranes under UV irradiation or redox initiators had enhanced anti‐fouling properties while maintaining salt retention. The modified membranes fabricated by UV‐induced or Redox‐initiated technique had superior anti‐fouling capabilities, with irreversible fouling factors and maintained flux ratios of around 8% and 43%, respectively, after 8 h of filtration, compared to only 12% and 36% for the unmodified membrane. These findings suggest that the modified membranes have the potential for use in filtration systems to prevent the fouling phenomenon.

Numerical entropy analysis of MHD electro-osmotic flow of peristaltic movement in a nanofluid

The present study investigates the MHD electro-osmotic flow of entropy generation analysis for peristaltic movement in a nanofluid with temperature-dependent viscosity. Long wavelengths, i.e., The magnitude of a wave's energy corresponds directly to its frequency while being inversely related to its wavelength in terms of velocity, temperature, and concentration, govern and confine the flow stream in the laminar region. Ohmic heating and hall effects are also included. Graphs are used to obtain and examine numerical solutions for axial velocity, temperature, concentration, Bejan number, and entropy generation. The effects of this research can help to improve pumping and gastrointestinal movements in different engineering devices. Debye–Huckel and lubrication approximations are studied to access the Boltzmann distribution of electric potential across an electric double layer. The investigations of an existing model are important in illuminating the microfluidics machinery used at the micro level for various transport phenomena in which fluids as well as particles are transported together. The current study has many applications and can be further extended to a three-dimensional profile with appropriate modifications and assumptions. When studying entropy generation, it is essential to examine the irreversible factors, while also taking into account the velocity and thermal slip conditions at channel boundaries. Moreover, the concept of entropy generation holds significant importance in comprehending various biological phenomena. Hence, the current research holds promising implications for both industrial and medical fields. The entropy generation is minimum at left wall of the channel for negative values of Helmholtz-Smoluchowski velocity.

Thermodynamic Derivation of the Reciprocal Relation of Thermoelectricity.

The Kelvin relation, relating the Seebeck coefficient and the Peltier coefficient, is a theoretical basis of thermoelectricity. It was first derived by Kelvin using a quasi-thermodynamic approach. However, Kelvin's approach was subjected to much criticism due to the rude neglect of irreversible factors. It was only later that a seemingly plausible proof of the Kelvin relation was given using the Onsager reciprocal relation with full consideration of irreversibility. Despite this, a critical issue remains. It is believed that the Seebeck and Peltier effects are thermodynamically reversible, and therefore, the Kelvin relation should also be independent of irreversibility. Kelvin's quasi-thermodynamic approach, although seemingly irrational, may well have touched on the essence of thermoelectricity. To avoid Kelvin's dilemma, this study conceives the physical scenarios of equilibrium thermodynamics to explore thermoelectricity. Unlike Kelvin's quasi-thermodynamic approach, here, a completely reversible thermodynamic approach is used to establish the reciprocal relations of thermoelectricity, on the basis of which the Kelvin relation is once again derived. Moreover, a direct thermodynamic derivation of the Onsager reciprocal relations for fluxes defined as the time derivative of an extensive state variable is given using the method of equilibrium thermodynamics. The present theory can be extended to other coupled phenomena.

The International Initiative to Measure Perceived Risk in Arthroplasty: The Results From a Multinational Survey

BackgroundThere is an inherent moral imperative to avoid complications from arthroplasty. Doing so at ideal cost is also associated with surgeon reputation, and, increasingly in health care delivery systems that measure and competitively score outcomes, reimbursement to the surgeons and their hospitals. As a result, patients who are perceived to be in higher risk comorbidity groups, such as the obese and diabetics, as well as those challenged by socioeconomic factors may face barriers to access elective arthroplasty. MethodsIn this initiative, surveys were sent to surgeons in 8 different countries, each adapted for their own unique payment, remuneration, and punitive models. The questions in the surveys pertained to surgeons’ perception of risk regarding medical and socioeconomic factors in patients indicated for total hip or knee arthroplasty. This paper primarily reports on the results from Canada, Ireland, and the United Kingdom. ResultsThe health care systems varied between a universal/state funded health care system (Canada) to those that were almost exclusively private (India). Some health care systems have “bundled” payment with retention of fees for postoperative complications requiring readmission/reoperation and including some with public publication of outcome data (United States and the United Kingdom), whereas others had none (Canada). There were some major discrepancies across different countries regarding the perceived risk of diabetic patients, who have variable Hemoglobin A1c cut-offs, if any used. However, overall the perception of risk for age, body mass index, age, sex, socioeconomic, and social situations remained surprisingly consistent throughout the health care systems. Any limitations set were primarily driven by surgeon decision making and not external demands. ConclusionSurgeons will understandably try and optimize the health status of patients who have reversible risks as shown by best available evidence. The evidence is of variable quality, and, especially for irreversible social risk factors, limited due to concerns over cost and quality outcomes that can be influenced by experience-driven perceptions of risk. The results show that perceptions of risk do have such influence on access across many health care delivery environments. The authors recommend better risk-adjustment models for medical and socioeconomic risk factors with possible stratification/exclusions regarding reimbursement adjustments and reporting to help reverse disparities of access to arthroplasty.

Longitudinal changes in radiographic features of pulmonary Mycobacterium avium complex diseases

BackgroundThe radiographic features of Mycobacterium avium complex pulmonary disease (MAC-PD), a major component of nontuberculous mycobacteria, consist of a variety of lesions; however, the responsiveness of each type of radiographic factor to treatment is unclear. Thus, we evaluated the longitudinal changes of each factor in serial computed tomography (CT) images using a mixed-effects model, and investigated the radiographic transition in patients with MAC-PD whose progress could be followed. MethodsIn this retrospective study, eighty-four patients diagnosed with MAC-PD and with yearly CT records were recruited after a review of 328 medical records with culture-positive MAC in respiratory specimens. The study participants were divided into two groups: treatment (n = 43) and no-treatment (n = 41) groups. Radiographic images were scored using the nodule (N), infiltration (I), cavity (C), ectasis (E) scoring system. Longitudinal changes in each radiographic lesion factor were analyzed using a mixed-effects model in treated and untreated patients. ResultsAll factors tended to progress without treatment, and significant longitudinal changes were observed in the N, I, and E factors (N: p = 0.010, I: p = 0.004, E: p < 0.001). Although treatment tended to improve N and I in radiographic images (N: p = 0.006, I: p = 0.203), cavities and ectasis progressed, regardless of treatment (C: p = 0.057 and E: p = 0.033). ConclusionRadiographic changes of MAC-PD can be categorized into reversible (nodules and infiltrations) and irreversible (cavities and ectasis) lesions. Early treatment may prevent the accumulation of irreversible factors.

DISTANCE CLASSES AS ONE OF THE FORMS OF ENSURING THE QUALITY AND EFFECTIVENESS OF EDUCATION IN EDUCATIONAL INSTITUTIONS

The modern education system is due to two irreversible progressive factors: the intensive development of information technology and fierce competition in the market of educational services. The leading role of distance learning in these processes is undeniable. The question is in optimizing the use of innovative resources for solving linguistic problems.

Identification Risk Factors of Stroke: Literature Review

Abstract: State spending to deal with stroke is quite large every year due to the high incidence of stroke. Data from the Ministry of Health of Indonesia mentions an increasing number in health financing every year, the country financed stroke services by 2.56 trillion in 2018. The magnitude of the incidence of stroke can be lowered by controlling the risk factors of stroke. This study aimed to identify stroke risk factors, both those modifiable risk factors and irreversible risk factors. Research is conducted with a literature review using descriptive study methods or correlation analysis with cross sectional approaches. Sixteen articles identified from Google scholars and Garuda databases in the 2015-2020 range, and were analysed using JBI critical appraisal tools-checklist for analytical cross-sectional studies and JBI critical appraisal tools-checklist for prevalence studies. Synthesis narrative was used to analyse the articles. Out of 16 articles examined the modifiable risk factors were hypertension, dyslipidemia, diabetes mellitus, lack of physical activity, blood sugar levels, cholesterol levels in blood, alcohol and drug consumption, kidney disease, tuberculosis, heart disease, heart failure, obesity, central obesity, atrial fibrillation and also smoking are declared associated with the incidence of stroke. The irreversible risk factors are age, gender, education, family history, income employment, previous stroke history, and rural and urban distribution. Risk factors divided into two categories modifiable risk factors and irreversible risk factors. It is important to know the risk factors of stroke in order prevent the occurrence of stroke as early as possible by avoiding modifiable stroke risk factors. Hypertension, smoking, diabetes mellitus obesity, dyslipidemia, and lack of activity are the most modifiable stroke risk factors identified in the articles. The most irreversible risk factors identified in the article are age, gender, and level of education.

A Review on epigenetics alternations in high fat diet induced diabetes

T2DM is complicated, with irreversible risk factors such as age, genetic, race, and ethnicity, as well as reversible risk factors like as food, physical activity, and smoking, with eating habits and sedentary lifestyle being the key contributors for fast growing incidence. Chronic exposure to HFD promotes liver damage, poor glucose homeostasis, hyper insulinemia, late pancreatic β-cell failure to generate insulin due to cell fatigue and resultant hyperglycemia, which are the key hallmarks of T2DM. Metabolic diseases such as T2DM have been linked to epigenetic changes that occur without changes in the DNA sequence, such as cytosine methylation of DNA, histone posttranslational modifications, and microRNA, which provide links between genes and environmental factors such as diet, smoking, and other lifestyle factors. T2DM affects insulin gene expression and beta cell differentiation via both histone modifications and DNA methylation in diabetic islets, which plays a vital role in regulating mitochondrial genes and in diabetes regulation. As a result, we provide existing evidence on epigenetic changes in high fat diet-induced diabetes. Metabolic diseases such as T2DM have been linked to epigenetic changes that occur without changes in the DNA sequence, such as cytosine methylation of DNA, histone posttranslational modifications, and microRNA, which provide links between genes and environmental factors such as diet, smoking, and other lifestyle factors. T2DM affects insulin gene expression and beta cell differentiation via both histone modifications and DNA methylation in diabetic islets, which plays a vital role in regulating mitochondrial genes and in diabetes regulation. In this review, we provide existing evidence on epigenetic changes in high fat diet-induced diabetes.

Identification Risk Factors of Stroke: Literature Review

State spending to deal with stroke is quite large every year due to the high incidence of stroke. Data from the Ministry of Health of Indonesia mentions an increasing number in health financing every year, the country financed stroke services by 2.56 trillion in 2018. The magnitude of the incidence of stroke can be lowered by controlling the risk factors of stroke. This study aimed to identify stroke risk factors, both those modifiable risk factors and irreversible risk factors. Research is conducted with a literature review using descriptive study methods or correlation analysis with cross sectional approaches. Sixteen articles identified from Google scholars and Garuda databases in the 2015-2020 range, and were analysed using JBI critical appraisal tools-checklist for analytical cross-sectional studies and JBI critical appraisal tools-checklist for prevalence studies. Synthesis narrative was used to analyse the articles. Out of 16 articles examined the modifiable risk factors were hypertension, dyslipidemia, diabetes mellitus, lack of physical activity, blood sugar levels, cholesterol levels in blood, alcohol and drug consumption, kidney disease, tuberculosis, heart disease, heart failure, obesity, central obesity, atrial fibrillation and also smoking are declared associated with the incidence of stroke. The irreversible risk factors are age, gender, education, family history, income employment, previous stroke history, and rural and urban distribution. Risk factors divided into two categories modifiable risk factors and irreversible risk factors. It is important to know the risk factors of stroke in order prevent the occurrence of stroke as early as possible by avoiding modifiable stroke risk factors. Hypertension, smoking, diabetes mellitus obesity, dyslipidemia, and lack of activity are the most modifiable stroke risk factors identified in the articles. The most irreversible risk factors identified in the article are age, gender, and level of education

Novel principle for characterizing the material-level parameters of a thermoelectric generator module

• A high-fidelity transient model considering all related effects is built and verified. • A modified characterization method using stepped temperature rise is proposed. • The modified method improves the implementation efficiency by 108 times in theory. • A generally consistent accuracy in both characterized results is validated by tests. Accurate characterization of all the three material-level parameters, i.e., thermal conductivity, Seebeck coefficient and electrical resistivity, is a premise for performance evaluation or degradation analysis of both the lab-made and commercial thermoelectric generator (TEG) modules. The recently reported quasi-steady-state (QSS) method can directly derive all the three temperature-dependent parameters through in situ TEG module characterization but shows a poor efficiency. This paper presents a modified QSS method based on stepped temperature rise for a high implementation efficiency. Both the optimal ‘width’ and ‘height’ of each step are elaborately specified. Its feasibility is then validated using a high-fidelity transient TEG model, which considers all the related effects and key irreversible factors. According to the simulations, the modified method has a 108 times higher efficiency than that of the original QSS method. Finally, the practicality of this modified method is explored by tests, which shows a consistent accuracy compared to the original method. Therefore, the modified QSS method is more practical, because it can greatly improve the efficiency on the premise of ensuring the accuracy with its similarity to the original QSS method. All the principle, method and conclusions can assist TEG performance estimation and guide the design of large-scale power systems.

Characterization of polyamide thin film composite membranes incorporated silver nanoparticles

AbstractIn this study, the polyamide thin film composite membrane surface has been modified by anti‐microbial silver nanoparticles (AgNPs). The membrane surfaces were interwoven with AgNPs by ultraviolet grafting polymerization method using AgNPs with or without poly(ethylene glycol) (PEG). The membrane surface characteristics were determined by scanning electron microscopy–energy dispersive x‐ray spectrometry images, attenuated total reflection–Fourier transforms infrared spectroscopy, water contact angle values, and anti‐bacterial property. The separation performance was determined based on the flux and the ability to remove calcium ions in water. The anti‐biofouling property was appraised through the maintained flux ratios and the irreversible fouling factors of unmodified and modified membranes during 10 h‐filtration of protein bovine serum albumin (BSA) in an aqueous solution, in which, before filtration of BSA, all membranes were immersed in E. coli bacteria solution for 4 days. The results of the experiments corroborated the hydrophilicity and more anti‐microbial property of the membrane surfaces after being incorporated into AgNPs. The water contact angle decreased from around 49° for the unmodified membrane to 36° and 23° for the AgNP‐modified membranes without/with PEG, while no colonies appeared in the medium containing the AgNP‐modified membranes. The separation property of modified membranes was improved, with both membrane flux and antifouling properties, along with the substantial surge of the anti‐biofouling property. After 10 h of BSA filtration, the fluxes of the modified membranes were maintained at 68% and 78% for AgNP‐modified membranes without and with PEG, respectively. Conversely, this value was only 46% for the unmodified one.

Thermal Brownian refrigerator with external and internal irreversibilities

In this paper, a new model of irreversible thermal Brownian refrigerators considering external and internal irreversibilities is established by using finite time thermodynamics. The analytical formulas of cooling load and coefficient of performance (COP) are derived with Newtonian heat transfer law. The operating temperatures of the refrigerator are obtained by solving equations, and the basic performance characteristics and valid working areas are studied. The optimal performance is achieved by optimizing the design parameters and the heat transfer process. The effects of key parameters, temperature ratio and irreversible factors on optimal performance are investigated. The new model performance is compared with that of previous models. Results show that the new model provides a unified description for thermal Brownian refrigerators. The cooling load and COP exist maximal values about thermal conductance ratio between the two heat exchangers. When the thermal conductance ratio and other design parameters are optimal, the corresponding operating temperatures of the thermal Brownian refrigerator reach the optimal values. The results are universal, and it contains the results of previous models with different irreversible factors.

Thermal Brownian heat engine with external and internal irreversibilities

A finite time thermodynamic model of irreversible thermal Brownian heat engines with various irreversibilities is built. The analytical expressions of power and efficiency are derived. The working temperatures are solved by combining equations, the essential performance characteristics of heat engine are further analyzed. The relationships among optimal performance indicators and design parameters are also studied. The optimal performance characteristics are obtained by optimizing the internal parameters and thermal conductance ratio of heat exchangers. The optimal working regions and optimal working temperatures are also given. Finally, the new model performance is compared with that of the non-equilibrium thermodynamic one, and the significance of the new model is illustrated. The results show that the new model can be simplified to the existing models, and the optimal performances of those existing models with different irreversible factors can also be derived through the optimization relation in this paper. The power and efficiency have extreme values about barrier height, thermal conductance ratio and external load, respectively. When those parameters are optimized simultaneously, the corresponding values of the working temperature are optimal for the heat engine. The kinetic energy will reduce power and efficiency, which is different from the result of the non-equilibrium thermodynamic models.

Failure diagnosis and trend‐based performance losses routines for the detection and classification of incidents in large‐scale photovoltaic systems

AbstractFault detection and classification in photovoltaic (PV) systems through real‐time monitoring is a fundamental task that ensures quality of operation and significantly improves the performance and reliability of operating systems. Different statistical and comparative approaches have already been proposed in the literature for fault detection; however, accurate classification of fault and loss incidents based on PV performance time series remains a key challenge. Failure diagnosis and trend‐based performance loss routines were developed in this work for detecting PV underperformance and accurately identifying the different fault types and loss mechanisms. The proposed routines focus mainly on the differentiation of failures (e.g., inverter faults) from irreversible (e.g., degradation) and reversible (e.g., snow and soiling) performance loss factors based on statistical analysis. The proposed routines were benchmarked using historical inverter data obtained from a 1.8 MWp PV power plant. The results demonstrated the effectiveness of the routines for detecting failures and loss mechanisms and the capability of the pipeline for distinguishing underperformance issues using anomaly detection and change‐point (CP) models. Finally, a CP model was used to extract significant changes in time series data, to detect soiling and cleaning events and to estimate both the performance loss and degradation rates of fielded PV systems.

Multi-objective performance optimization of regenerative S-CO2 Brayton cycle based on neural network prediction

• A finite time thermodynamic model for regenerative S-CO 2 Brayton cycle is set up. • Artificial neural networks and multi-objective optimization are used. • Four different optimization objectives are considered. • The thermal efficiency and net power output are increased by 31.15% and 43.29%. • The exergy efficiency is increased by 33.75%. The regenerative supercritical CO 2 Brayton cycle (RSCBC) has great development potential in waste heat recovery and utilization, and it is necessary to carry out performance analysis and optimization. This article first applies the theory of finite time thermodynamics to establish a RSCBC model with finite temperature difference heat transfer, irreversible compression, irreversible expansion and other irreversible factors under variable temperature heat source conditions, and then uses the data samples to construct the corresponding neural network model. Based on the NSGA-Ⅱ algorithm, the working fluid mass flow rate, the pressure ratio, the heat conductance distribution ratios of the regenerator and the heater are chosen as optimization variables, multi-objective optimization is carried out with the goals of cycle thermal efficiency, net power output, ecological function and exergy efficiency. The results show that the use of neural network models to predict cycle performance can save a lot of calculation time compared to traditional calculation methods; after optimization, the positive ideal point is not on the Pareto front, which shows that the four optimization objectives are mutually restricted and affect each other. The results by using Shannon Entropy method for decision-making have a lower deviation index, and those by using TOPSIS and LINMAP methods for decision-making are consistent with each other; for the results by using Shannon Entropy method for decision-making, the cycle thermal efficiency and net power output can reach 38.4% and 12.047 MW respectively, which can be increased by 31.15% and 43.29% compared to those for the initial design point respectively, and the ecological function and exergy efficiency can reach 7.6274 MW and 73.2% respectively, which are 4.2588 times and 33.75% higher than those for the initial design point respectively. The obtained results can provide some guidance for the optimal design of the RSCBC in real engineering.

Relationship Between Smoking and Ischemic Stroke: Meta Analysis

Background: Ischemic stroke is a non-communicable disease that has irreversible and modifiable risk factors. One of the risk factors that can be changed in preventing ischemic stroke is smoking behavior. The purpose of this study was to determine the relationship between smoking and the incidence of ischemic stroke from several previous studies. Subjects and Method: This article was compiled with a systematic review and meta-analysis study. This study uses the PICO model as follows. Population= Patients at Risk of Ischemic Stroke, Intervention= Smoking, Comparison= Not Smoking, and Outcome= Ischemic Stroke Incidence. The articles used in this study were obtained from several databases including PubMed and ScienceDirect. This article was collected within 1 month. The keywords to search for articles were as follows: Current AND Smoking OR Tobacco OR Cigarettes AND Hypertension AND "Ischemic Stroke" OR CVA (Cerebrovascular Accident). Results: Nine articles reviewed in this meta-analysis were from Lebanon, Mexico, Pakistan, Finland, Pakistan, United States of America, Saudi Arabia, Bangladesh, Iran. In this study, smokers had a 1.66 times risk of developing an ischemic stroke compared to nonsmokers and it was statistically significant (aOR= 1.66; 95%CI= 1.48 to 1.86; p&lt; 0.001). People who smoked had a 1.66 times risk. experienced the incidence of isleemic stroke compared to non-smokers and was statistically significant (aOR= 1.66; 95%CI= 1.48 to 1.86; p&lt; 0.001). Conclusion: Smoking has a relationship with the occurrence of ischemic stroke in at-risk patients. Keywords: smoking, hypertension, ischemic stroke. Correspondence: Septyan Dwi Nugroho. Universitas Sebelas Maret. Jl. Ir. Sutami 36A, Surakarta 57126, Central Java, Indonesia. Email: septyandwin@gmail.com. Mobile: 081804418933.

I must eat what I want: A roadblock to type 2 diabetes management

Globally, type 2 diabetes mellitus (T2DM) is considered as one of the most common diseases, which is associated with irreversible risk factors such as age, gene, race, ethnicity, and reversible factors such as diet, physical activity, and smoking. Noncompliance to dietary regimen is the major factors for rapidly rising incidence of T2DM among developing countries. Recently, elevated HbA1c level has also been considered as one of the leading risk factors for developing microvascular and macrovascular complications. Improvement in the elevated HbA1c level can be achieved through diet management; thus, this study found that improvement in patients' dietary knowledge, attitude toward, and compliance to diet regimen will promote a better control of the disease. In conclusion, the stakeholders (health-care providers, health facilities, agencies involved in T2DM care) should educate the patients on the importance of dietary modification in the disease management. Similarly, there is a need for nurses and other health care professionals to advocate and promote a better holistic management that will encourage patients participation and family involvement in the care.

Exergy Analysis of the Electromagnetic Railgun

In this article, the energy conservation equation of a railgun is established by the Poynting theorem. The concept of exergy in thermodynamics is introduced, and the exergy calculation formula of electromagnetic (EM) energy, kinetic energy, and Joule heat as well as the exergy balance equation of the system are obtained. Using the experimental parameters of a medium-caliber railgun, the exergy of magnetic energy stored in the inductor of the system after a launch is calculated by dynamic simulation, and the exergy loss caused by friction and air drag as irreversible factors is obtained. The skin effect caused by time-varying EM field is considered when calculating the heat exergy of Joule heat of rails. Through the transient thermal simulation of the rail by the finite-element software, the temperature field distribution of the rail is obtained. On this basis, the qualitative temperature for calculating the heat exergy is obtained, and the heat exergy stored on the rail after the launch is calculated by the formula. Finally, how to reduce the exergy loss of the railgun is analyzed qualitatively.

An in-depth study of nonlinear parametric characterization for thermoelectric generator modules

Thermoelectric (TE) parameters provide indispensable data for the optimal design, accurate modeling, and performance assessment of off-the-shelf TE modules. However, the lack of unified characterization methods for these nonlinear data creates challenges for the design of large-scale TE systems. This paper aims at a thorough exploration of the accuracy, efficiency, and applicability of five typically reported characterization methods in terms of temperature-dependent material-level TE parameters (Seebeck coefficient, thermal conductivity and electrical resistivity). A common test setup was built and specifically improved for the convenient and high-precision measurement of heat rate. The four methods except for the Buist’s modified Harman method can characterize the satisfactory material-level TE parameters only if the thermoelectric generator (TEG)’s irreversible factors are considered including the thermal resistances of substrates and interlaminar contact resistances. The applicability of each method in a large temperature range is discussed by simulation beyond their inherent limits of adopted setups in this paper. Most methods show significant deviations at high temperatures due to their inherent parametric spatial-independence assumptions. From the perspective of their theoretical feasibility and practical accuracy, the quasi steady-state method is more advantageous than others. This research can guide the employment of characterization methods and assist the design and optimization of large-scale TE systems.