Thermal Performance Analysis Research Articles

Numerical Analysis of Hydraulic and Thermal Performance of Al2O3-Water Nanofluid in a Zigzag Channel with Central Winglets

This study numerically examined the impacts of central winglets and Al2O3-water nanofluid on the thermo-hydraulic performance in a zigzag channel. The analyzes based on Computational Fluid Dynamic (CFD) using the SIMPLE algorithm are actualized for nanofluid flow in Reynolds numbers (Re) varying between 200 and 1200. The volume fraction of nanoparticle (φ) is changed from 1% to 5 %. The upper and lower zigzag surfaces are kept at Tw = 350 K constant temperature. The results are given in terms of thermal improvement (η), dimensionless friction factor (Γ), and thermo-hydraulic performance (THP). In addition, the work is compared with the zigzag channel without winglet for the base fluid. The temperature and velocity distributions are obtained for the zigzag channel with and without winglet at different Reynolds numbers. The results show that the nanofluid and winglets contribute considerably to the enhancement of heat transfer, but the friction factor slightly increases. The heat transfer improves with increasing inlet velocity and particle volume fraction. The highest thermo-hydraulic performance is obtained as approximately 2.12 for Re = 400 and φ = 0.05.

Thermal Performance Analysis and Prediction of Printed Circuit Boards

Printed circuit boards (PCBs) are important components of electronic devices, they play the roles of mechanical connections and electrical transmission, thermal failure is their main failure mode, the heat flow analysis and thermal reliability design are the basis and premise to improve thermal performance of PCBs. In this paper, analysis models of PCBs thermal performance are built based on the principles of fluid mechanics and the finite element method, and we obtain the influence and analysis of internal heat sources on PCBs thermal performance. The study provides a theoretical basis for PCBs thermal reliability design which can be applied to high-density Internet of Things and blockchain ICT integration.

Thermal performance analysis of a new type of branch-fin enhanced battery thermal management PCM module

To solve the problem of the lightweight design of metal fins and strengthen the heat transfer between phase change material (PCM) and lithium batteries, the synergistic design of fins and phase change material-battery thermal management system (PCM-BTMS) is particularly important. In this paper, 9 new branch fin design schemes were proposed based on the conventional straight fin. The reliability of the computational fluid dynamics model was verified through the heat transfer experiments at different discharge rates. Firstly, the thermal performances of 9 new fins and the conventional straight fin under 5C discharge rate were compared and analyzed, and the optimal model was selected. Secondly, the effects of transverse fin coverage area, number, arc length, thickness, and arc length of inner and outer arc fins on the thermal performance were analyzed considering the effects of different heat transfer coefficients. The results show that the preferred fins have less effect on the heat transfer coefficient enhanced thermal performance compared with the conventional fins; the average cell temperature is reduced by 3.14 K and 3.92 K respectively by increasing the fin coverage area and the number of transverse fins to increase the contact area with PCM to enhance heat dissipation; the average cell temperature changes more significantly with the inner arc fins, and the cell temperature of Case H6 was reduced by 7.2 K; while the transverse fin arc length extension reduced the thermal performance of the system in high temperature cases. The volume of system remained the same, and the thickness of the transverse fins decreased the heat storage capacity of the system when the thickness of the transverse fins was larger. The optimal fins could keep the average cell temperature within 318.15 K. The heat transfer capability was improved by 14.98%, the operating time was extended by 131.5%, and the system weight was reduced by 10.28%.

Influence of thermal conductivity on transient mixed convection in a vented cavity with a hollow cylinder and filled with CNT-water nanofluid

This study is aimed to perform a numerical time-dependent investigation thermal conductivity effect of the annular cylinder within a vented cavity using CNT based-water nanofluid. For demonstrating the effect of thermal conductivity, four distinct hollow cylinder materials such as Ks = 0.5(Plastic tiles), Ks = 0.84(Clay tiles), Ks = 1.1(Concrete tiles), and Ks = 2(Slate tiles) are introduced together with a suitable variation of dimensionless time (0 ≤ τ ≤ 1). The governing equations of the model with associated boundary conditions is solved using finite element based Galerkin's weighted residual method. Different contour plots for thermal and flow field transformation and mean Nusselt number, mean fluid temperature, bulk convective field temperature, temperature gradient, pressure gradient, vortices, and fluid velocity magnitude are presented for qualitative and quantitative thermal performance analysis. With the decrease of solid thermal conductivity, 27.3% thermal transport enhancement is noted from the heated surface of the cylinder. However, a 16.3% increase in the bulk fluid temperature has been recorded with the increase in cylinder conductivity. The numerical outcomes from this investigation propose a better thermo-fluid efficiency compared to the existing methodology which can be suggestive to engineers and researchers for designing heat exchangers, heat pipes, and other thermal systems.

Evaluation and thermal performance of cool pavement under desert weather conditions: Surface albedo enhancement and carbon emissions offset

Surfaces such as pavement, buildings, and other heat-absorbing surfaces that store more heat than natural vegetation generate the Urban Heat Island (UHI) effect. Temperatures are known to be significantly higher in urbanized areas compared to rural ones.The application of a reflective surface treatment to the pavement improves its solar reflectivity while lowering the warmth of its surface. The main objective of this study is to assess the performance of a cool pavement in an educational complex parking area, under desert climatic conditions to reduce heat islands. White and high reflective material was applied to the tested parking pavement area. Various experimental techniques were used to assess the performance of non treated (baseline) and treated (cool) pavements including spectral radiation, reflectance (albedo), solar irradiance, and pavement surface temperature. The results show that the coated pavement has a 15 % reflectance in ultraviolet A (UVA) and the untreated pavement has a 17 % solar reflectance (baseline basement). There are no potential dangers to human health posed by the coated pavement's reflection of UVA (For visible wavelengths, coated pavement has a reflectance of roughly 70 %, while uncoated pavement has a reflectivity of only 24 %. Under desert climatic conditions, the results show a net decrease in surface temperature of the coated pavement by up to 15 °C compared to the uncoated one. In the summer, for example, raising the albedo of the pavement surface from 24 % to 70 % lowered the surface temperature from 60 °C to 47 °C. This represents a 22 % decrease in pavement surface temperature. The thermal performance analysis of the cool pavement technology reveals that the pavement surface albedo enhancement will help to increase surface reflectance while lowering pavement surface temperature and offsetting CO2 emissions. Increasing the pavement surface albedo by 192 % (from 24 % to 70 %) for the total treated surface area (81,000 m2) in the educational complex will offset 28,350 tons of CO2. The application of a white coating with a high reflective value on concrete and asphalt pavements will help to extend the life of the pavement, reduce the energy consumption of buildings and the emissions of greenhouse gases, minimize the emissions of carbon dioxide caused by the enhancement of albedo (a strategy for mitigating the effects of climate change), improve parking lot visibility, and deal with the effects of heat islands.

Thermal performance analysis and experimental verification of lithium-ion batteries for electric vehicle applications through optimized inclined mini-channels

Power units (i.e., batteries) of electric vehicles (EVs) generate heat while being charged or discharged, which deteriorates their performance and reliability over time. This paper investigates a comprehensive spectrum of geometric and thermo-fluidic parameters of a liquid coolant flowing through mini-channels. These are embedded in the surface of an EV battery to curtail overheating. Design parameters such as aspect ratio and angular orientation of the mini-channels were varied randomly to investigate several geometric configurations that are scarcely intuitive. The coolant mass flow rate and the fluid inlet temperature were also varied through a large dataset of randomly distributed values. A real-time EV driving cycle was implemented alongside an experimentally validated model to evaluate the battery operation, which evidenced the complex dependence of the battery’s thermal state with different levels of cooling retrofitting. The study also analyzed the parasitic power consumption arising from the pumping and cooling energy demands to drive the coolant system to achieve an optimally designed retrofit for a reliable battery performance. It was found that the mini-channel parameters considerably affect the thermal performance of the battery. However, the optimized case was found to have a minimum temperature difference in the battery and a minimum power requirement. The case with a fluid inlet velocity of 0.13 m/s, a fluid inlet temperature of 312.9 K, an aspect ratio of 1.7, and an inclination angle of 4.9° was found to be the most suitable, leading to a refrigeration power requirement of 0.85 W only. The battery temperature after the end of the driving cycle was maintained at 313 K.

Thermal Performance and Energy Analysis of Phase Change Material-Integrated Building with the Auxiliary Heating System in Different Climate Regions

Phase change material (PCM) embedded in the building contributes to enhancing indoor thermal comfort and reducing the heating load in winter by absorbing/releasing solar energy. The application effects of PCM incorporated into a single-space passive solar building with the auxiliary heating system (AHS) were investigated numerically in the six representative regions of western China. In the calculation and analysis by the enthalpy model, it was found that the effectiveness of PCM greatly depended on local climate conditions, thickness, and location of PCM. The results indicated that it was necessary to adopt the AHS for winter heating of the passive solar building. On this basis of using AHS, it showed a favorable thermal energy storage effect after the application of PCM resulting in the minimum indoor air temperature being maintained above 15°C within the comfort range stably. The integrated discomfort degree in each region was decreased by more than 96% compared to the original building, and the average temperature in Lhasa was 2°C higher than that in Urumqi. Furthermore, the highest rate of energy saving and carbon dioxide emission saving in the six regions was 19.7% and 17.4% in Lhasa, and the lowest were 4.3% and 4.2% in Urumqi, while other regions were relatively close, respectively. As a result, it can be stated that for a passive solar building using the AHS during the heating period, PCM was the most suitable for application in Lhasa, unsuitable in Urumqi, and generally suitable in other regions.

Erratum: “Thermal performance analysis for moderate Rayleigh numbers of Newtonian hybrid nanofluid filled U-shaped cavity with various thermal profiles” [Phys. Fluids 33, 032006 (2021)

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Modeling and simulation of vehicle integrated thermal management system for a fuel cell hybrid vehicle

The high-efficiency thermal management is one of the major challenges for fuel cell vehicles due to the diversity and complexity of the components and systems. Thermal management systems and corresponding control strategies can affect the components’ performance, durability and reliability, the vehicle’s driving performance, fuel economy and occupant thermal comfort. The main objective of this study is to perform multi-case simulation analysis of the fuel cell vehicle thermal management system through modeling to derive the operating mechanism and thermal performance analysis of each subsystem and integrated system. To achieve this purpose, an integrated thermal management system model with different control strategies was proposed based on a fuel cell vehicle prototype, powered by a 65 kW proton exchange membrane fuel cell stack and a Li-ion battery with a capacity of 15 kWh, which considers the cooling of the driving system, fuel cell stack, battery and cabin. The results showed that the critical temperature of each subsystem could be controlled within a reasonable range even in the battery charging mode, where the fuel cell generated about 136.6 % more thermal power than the discharging mode to charge the battery. Moreover, in the series structure of the radiators and condenser, the average temperatures of the inlet air of the motor and the subsequent fuel cell radiator were respectively 3.9 °C and 7 °C higher than the ambient temperature (35 °C), thus reducing the impact of the radiator fan. The proposed model may provide the contribution in the design of integrated solutions for thermal management systems for fuel cell hybrid vehicles under high temperature scenarios, including control strategies development and system-level coupling analysis.

Thermal and chemical reliability of paraffin wax and its impact on thermal performance and economic analysis of solar water heater

In the current investigation, two hot water storage tank integrated evacuated tube collector systems have been designed and fabricated. In one of the systems, an evacuated tube integrated with PCM (phase change material) is termed a testing system while another evacuated tube system was left without PCM termed a reference system. Based on the experimental results, it has been found that the incorporation of paraffin wax in the testing system improved the thermal energy output. Also, the thermal cycling of selected PCM has undergone up to 1500 cycles and results showed very negligible changes in its chemical and thermal properties. The useful energy output of the system with PCM has been improved by 36.81 %, 26.97 %, and 22.72 % for Run_40oC, Run_45oC, and Run_50oC respectively. In addition to this, extra hot water obtained from the testing system was 14 L for Run_40oC, 5 L for Run_45oC, and 6 L for Run_50oC respectively as compared to the reference system. Concerning techno-economic analysis, on average, the value of per litre cost of production of hot water (CPL) by the proposed system and electric water heater was observed to be INR 0.16 and INR 0.48 respectively. The net present value of the proposed system was found to be approximately INR 11598 and total expenditure on the proposed system can be recovered after 4.07 years which is much shorter compared to the life of the proposed system.The present work removes the overheating issue of heat pipes and improves the performance of the system by modifying in design and utilization of paraffin wax as heat storage material.

Thermal Performance Analysis of Functional Parameters of the Floor Heating System in Africa

Buildings frequently utilize radiant heating floors because they offer benefits including effective use of space and homogeneous temperature distribution, which results in increased thermal comfort. The present work aims to investigate the perfect use of floor heating systems analytically and numerically with improved thermal performance to prove their efffficiency in various African climates. The evaluation depends on the functional parameters of the heating system and particularly focuses on floor surface temperature to acquire the desired heat flux and the perfect supply water temperature. According to results, It is desirable to use floor coverings with low thermal resistance and should not exceed R = 0.15 m2 . K/W since it has considerable influence on the thermal efffficiency of the underfloor heating components. The pipe diameter is suggested to be about 20 mm. By comparing pipe spacings of 15 mm and 30 mm, the difference in supply water temperature is approximately 7.4 C. The smaller the pipe spacing, the more energy it delivers and makes the floor much warmer while reducing heating time. Regarding the effect of pipe materials, PE-X is chosen for this study because of its low cost and resistance to corrosion and scaling. As the influence of these studied parameters on floor heating is remarkable, there is also the impact of the ambient temperature of each city on the floor heating efffficiency. The proposed model can be applied and considered potentially beneficial and helpful to the control, and design of floor heating systems, and choosing the right heating source.

Energy and Thermal Performance Analysis of PCM-Incorporated Glazing Units Combined with Passive and Active Techniques: A Review Study

The building envelope provides thermal comfort, an excellent visual view, and sunlight for the occupants. It consists of two parts: (i) an opaque (non-transparent) part (e.g., walls and roofs) and (ii) a transparent part (e.g., windows, curtain walls, and skylight devices). Recently, the use of fully-glazed facades, especially in large cities, has increased due to their aesthetical and structural advantages. This has led this study to review the performance of the currently passive smart glazing technologies. Phase Change Materials (PCMs) as latent energy storage material is the focus of this review, as well as other individual and combined techniques, including shading systems, solar cells (photovoltaic), and chromogenic (thermotropic and thermochromic) materials. PCM-integrated glazing systems have been extensively studied and rapidly developed over the past several decades from the standpoint of unique system designs, such as passive, active, and passive/active mixed designs, intelligent management, and sophisticated controls. In the academic literature, numerous studies on PCM-integrated building envelopes have been conducted, but a comprehensive review of PCM-integrated GUs combined with other passive and active techniques using dialectical analysis and comparing the climatic conditions of each study using Köppen-Geiger climate classification climate classification has been performed only rarely. Consequently, the primary objective of this study is to reduce this discrepancy for all types of glazing, excluding glazed roofs. This review article also contains literature tables as well as highlights, limitations, and further research suggestions at the end of each subsection.

Thermal and flow performance analysis of a concentrated linear Fresnel solar collector with transverse ribs.

This article deals with the impact of including transverse ribs within the absorber tube of the concentrated linear Fresnel collector (CLFRC) system with a secondary compound parabolic collector (CPC) on thermal and flow performance coefficients. The enhancement rates of heat transfer due to varying governing parameters were compared and analyzed parametrically at Reynolds numbers in the range 5,000-13,000, employing water as the heat transfer fluid. Simulations were performed to solve the governing equations using the finite volume method (FVM) under various boundary conditions. For all Reynolds numbers, the average Nusselt number in the circular tube in the CLFRC system with ribs was found to be larger than that of the plain absorber tube. Also, the inclusion of transverse ribs inside the absorber tube increases the average Nusselt number by approximately 115% at Re = 5,000 and 175% at Re = 13,000. For all Reynolds numbers, the skin friction coefficient of the circular tube with ribs in the CLFRC system is larger than that of the plain absorber tube. The coefficient of surface friction reduces as the Reynolds number increases. The performance assessment criterion was found to vary between 1.8 and 1.9 as the Reynolds number increases.

Thermal performance analysis and multi-objective optimization of thermal energy storage unit with cascaded packed bed in a solar heating system

• Established the CPBTES’s continuous solid phase simplified model and exergy analysis model. • The numerically predicted temperatures match well with the experimental measurements. • Compared the thermal performance of CPBTES and PBTES in the solar heating system. • The regression model of main influencing factors and evaluation indexes was established by the response surface method, • Obtained the optimal parameter combination of multi-objective optimization. The capacity expansion and optimal design of the TES has an important impact on the operational efficiency of the solar heating system. In this study, a CPBTES system with a three-stage PCM was designed for a solar heating system. A one-dimensional, two-phase model based on thermal resistance analysis was established, and the adaptability of the model was verified by different experiments. A multi-objective evaluation system was established, and the response surface methodology was used to carry out the influence factor analysis and multi-objective optimization. The result showed that in the same operating conditions, CPBTES had a more uniform temperature distribution than single-stage TES, which was the key factor to improve the exergy efficiency. CPBTES improved the ideal charging completion time and the exergy efficiency by 7% and 5%, respectively, and reduced the effective TES capacity by 4% compared to single-stage TES. The optimal combination of parameters after multi-objective optimization was aspect ratio of 1.97, dimensionless diameter of 0.03, void ratio of 0.24, and intermediate filling ratio of 0.66. The multi-objective optimization result and method in this study can contribute to new ideas for similar engineering problems.

A novel configuration of a dual concentrated photovoltaic system: Thermal, optical, and electrical performance analysis

In this work, a validated finite element-based coupled optical, thermal, and electrical model is used to assess the performance of a dual concentrated photovoltaic system thermally regulated using a PCM for the environmental conditions of Lahore, Pakistan. Thermal management of the system is achieved using a selected PCM. That has a melting temperature of 53-56?C, a thermal conductivity of 19 W/mK, and heat of fusion of 220 kJ/kg. Thermal regulation and power output of the system are analyzed for a clear day of six months of a year. It is found that the maximum temperature of the upper PV cell is ~80?C while for the bottom PV cell is ~82?C in July. The percentage power gain obtained after the addition of an upper concentrated PV cell is ~17.9%. The maximum and minimum power of the system is found to be 0.079 kWh/day/m2 and 0.041 kWh/day/m2 in May and November, respectively.

Global sensitivity analysis of a generator-absorber heat exchange (GAX) system’s thermal performance with a hybrid energy source: An approach using artificial intelligence models

• Temperature, heat and flow measurements of an experimental GAX cycle. • Evaluation of artificial intelligence (AI) techniques for multivariate modeling. • Artificial neural networks represent the GAX system with the best accuracy. • AI model coupled to the PAWN method for a global sensitivity analysis of GAX cycle. • COP is affected the most by the temperature measured at the generator inlet. Generator-absorber heat exchange (GAX) systems represent a promising alternative to substitute environmentally harmful refrigeration devices based on conventional vapor compression, as long as a proper analysis of thermal performance and the complex interactions of heat transfer that occur into GAX cycle is taken in consideration. In this research, a cooling process based on a GAX system that uses ammonia-water working fluid and a hybrid source (natural gas-solar) is studied to analyze the variables that affect the system’s thermal performance. The work’s novelty is the hybridization between artificial intelligence (AI) modeling and the global sensitivity analysis (GSA) developed with the PAWN method. Experimental data was obtained from a system with a cooling capacity of 10.5 kW (3 Ton), designed to work at heat source temperatures of 200 °C. The measured variables were the temperatures at generator, heat at evaporator, and working fluid volumetric flow. Three AI techniques (artificial neural networks, genetic programming, and support vector machines) were evaluated for modeling the thermodynamic cycle. Results obtained from the PAWN method applied to the artificial neural network, since it was the best AI model, indicates that the operational parameters with a greater impact in the system’s performance are the inlet temperature at the generator (30.7 %) and the heat measured at the evaporator for NH 3 (27.4 %), for the first output COP N H 3 . For the second output COP H 2 O , the inlet temperature at the generator (32.5 %) and the and heat measured at the evaporator for H 2 O (26.7 %), have a greater impact for such output. The proposed IA-GSA methodology contributes to the development of operational decision-making related to instrumentation, operation performance, and corrective and/or preventive maintenance actions of GAX systems. The developed thermal performance model has potential for implementation in embedded systems (smart sensors) as a critical element in control and optimization strategies to improve the performance of these cycles.

Localized Theoretical Analysis of Thermal Performance of Individually Finned Heat Pipe Heat Exchanger for Air Conditioning with Freon R404A as Working Fluid

Localized Theoretical Analysis of Thermal Performance of Individually Finned Heat Pipe Heat Exchanger for Air Conditioning with Freon R404A as Working Fluid

Signal processing and thermal performance analysis of motor heat recovery system

In order to realize the condition monitoring of the motor ?anytime, anywhere?, improve the detection accuracy and shorten the detection time, the author proposes a fault signal processing and diagnosis system for the motor heat recovery system based on the IoT. That is, based on the IoT technology, a mobile terminal oriented motor remote monitoring and fault diagnosis system, the sensing layer of the system collects real-time motor operation status data, and the transmission layer realizes data transmission, cloud storage and response to data requests from the application layer, finally, at the mobile end, the motor running status and diagnosis results are displayed through charts and text, so as to realize remote monitoring and fault diagnosis of the motor. The experimental results show that the accuracy of fault diagnosis test of GA-SVM in mobile terminal is more than 90%, and the running time is less than 30 ms, and the running time is very short. It proves that the mobile terminal uses the fault detection method based on GA-SVM model with high accuracy and short detection time, that is, the fault signal processing and diagnosis accuracy of the motor heat recovery system of the IoT is high and the detection time is short.

Thermal Performance Analysis of Carbon Materials Based TSV in Three Dimensional Integrated Circuits

Thermal Performance Analysis of Carbon Materials Based TSV in Three Dimensional Integrated Circuits

Synthesis, thermophysical characterization and thermal performance analysis of novel Cu-MXene hybrid nanofluids for efficient coolant applications.

Hybrid nanofluids are considered as an alternative for conventional heat transfer fluids and mono nanofluids due to its remarkable enhancement in thermo-physical properties. However, there are some limitations in achieving the better thermo-physical properties due to the stability of nanoparticles in different base fluids at higher concentration. This work aims at synthesizing, thermo-physical characterization and thermal performance estimation of stable Cu-MXene based hybrid nanofluids using various base fluids at very low volume concentration of Cu and MXene nanostructures. Two step method is employed to prepare Cu-MXene hybrid nanofluids by dispersing the low volume concentration of as prepared Cu and MXene nanostructures (ranging from 0.01-0.05 vol%) containing SDS surfactant in various base fluids such as water, methanol, castor oil and silicon oil. Synthesized mono and hybrid nanofluids shows excellent stability against aggregation up to 7 days as evidenced from higher zeta potential values. Wettability studies conducted using contact angle measurement suggests that the castor oil, methanol and silicon oil based hybrid nanofluids exhibits hydrophilic behavior (showing contact angle less than 90°). Hybrid nanofluids display excellent enhancement in thermal conductivity at very low concentration of nanostructures (more than 70% for methanol based Cu-MXene hybrid nanofluid). Viscosity of the silicone oil based hybrid nanofluids show a remarkable enhancement followed by water, methanol and castor oil based hybrid nanofluids. Thermal conductivity and viscosity of hybrid nanofluids are effectively validated with existing theoretical models. Moreover, specific heat and pumping power of the hybrid nanofluids with respect to volume concentration of nanostructures are determined using the existing theoretical equations. Thermal performance of hybrid nanofluids was successfully estimated using Figure of Merit (FOM) analysis and suggested the better heat transfer fluid for improving the heat transfer performance under laminar and turbulent flow conditions for efficient cooling applications.