Thermal Performance Of System Research Articles

Technical analysis of using a multi-storage system for a university campus: A case study of a Norwegian district heating system

The building sector accounts for 40% of the total energy use in the European Union. 80% of this use comes from space heating and domestic hot water systems. District heating (DH) systems make it possible to supply those demands by renewable energies, waste heat, and fossil fuel in a more efficient and environmentally friendly way. Peak load has a significant impact on the investment and operation cost of a DH system. Therefore, DH companies introduce DH price models that motivate heat users to reduce their peak load by charging for the heat rate extraction. The DH bill is divided into two parts: fixed and variable. The fixed part is counting for the extracted heat rate in kW, while the variable part is counting for the heat use in kWh. Depending on DH companies, some additional elements for volume or other expanses may be introduced. In this study, the focused was only on the two elements for the extracted heat rate and for the heat use, because they are taking the highest share of the DH bill. As a result of the above introduced approach for DH pricing models, introduction of thermal storage is a straightforward way for heat users to decrease their peak load. A DH system at a university campus in Norway is chosen as the case study. The entire system consisting of buildings, connection to a DH system, waste heat from the data center, and a multi-storage water tank (WT) was modeled in Modelica. In this study, instead of modeling the entire campus in one component, buildings are clustered, and one component modeled for each cluster of buildings. These clusters are based on heat demand profile of buildings. This could help to evaluate the performance of WT thermal storage system for different type of buildings. Result showed thermal storage system has better performance when it is implemented in a building with more fluctuation in heat demand. The system's peak is lower with a multistorage system compared to a single storage system. The main reason for this is reduced heat loss and improved adjustment in a multi-storage system.

Impact of hybrid nano PCM (paraffin wax with Al2O3 and ZnO nanoparticles) on photovoltaic thermal system: Energy, exergy, exergoeconomic and enviroeconomic analysis

Global renewable energy efforts place a significant preference on substantial solar photovoltaic (PV) systems. Photovoltaic thermal (PVT) systems are the upgraded version of PV modules that concurrently produce both electricity and heat. Hybrid nano-particles (2.0 wt % ZnO and 2.0 wt % Al2O3) into the phase change material (PCM) known as HNPCM system has been introduced in this current study for enhancing the electrical and thermal performance of the PVT system by improving the thermophysical properties of paraffin wax as used for passive cooling. Three PV systems were compared in terms of performance: a conventional PV system, a PVT system using paraffin wax as a PCM (PVT/PCM), and a PVT system with 2.0 wt % of Al2O3 and ZnO in PCM (PVT/HNPCM). Upon investigation, the PVT/HNPCM system under outdoor environmental condition shows that the inclusion of different nanoparticles in PCM led to improvements in thermal and overall efficiency of 17.32 % and 13.82 % compared to PVT/PCM, respectively. This results in increase of electrical efficiency of 34.84 % when compared to conventional PV panel and incremental peak exergy efficiency of 36.47 %. Besides, for PVT/HNPCM, cost of electricity production ($/kWh) is almost 16.67 % less than the conventional PV configuration and the payback time is about 2.1 years on the overall exergy basis. Additionally, PVT/HNPCM system exhibits the long-term life cycle conversion efficiency compared to conventional PV panel and maximum sustainability index of 1.21 has been also found. Finally, the conclusion can be drawn positively for PVT/HNPCM as the most effective system from the exergy efficiency, exergy cost, and CO2 avoidance rates point of view.

Анализ тепловой производительности радиационной системы жизнеобеспечения на основе экспериментальных данных

Solar energy is considered a renewable, most environmentally friendly and carbon-free form of energy. Solar collectors are one of the implementations of radiation life support systems. Their development requires a fairly large amount of initial data, such as the parameters of the premises, the required temperature, volume, thermal insulation of walls, floors and ceilings, the design of windows and doors, orientation to the cardinal points, the angles of inclination of the roof slopes, etc. The next group of factors is related to the location object, latitude, altitude above sea level, distance to large bodies of water, wind rose, etc. The third group is related to the weather itself: precipitation, cloudiness, outside air temperature, etc., a significant part of them, such as fog, haze, dew, shadow from each cloud affects the amount of insolation and all this cannot be taken into account in advance. The use of weather archives does not allow us to fully determine the specific thermal performance of solar collectors, since neither the average nor the current insolation is reflected in the archives. Without knowing the amount of real insolation and heat losses on the solar collector, it is impossible to determine the thermal performance of the radiation life support system per day, month, season or year. This paper discusses experimental and computational studies of the radiation life support system carried out in 2018–2022.

Performance study on turbulent heat transfer using rectangular air duct integrated with continuous and intermittent ribs turbulators

To continue the scientific path specialized in enhancing the thermal performance of thermal systems, several tests are carried out to improve the overall performance of a rectangular duct as air flows through it. This study reports experimentally and numerically the heat transfer enhancement and overall performance of a rectangular air duct with various arrangement of continuous and intermittent ribs turbulators. The ribs are inserting in several array arrangements at a 90o relative to the direction of flow. Three ribs lengths s= 30, 60 and 150 mm employed with the several arrangements that?s tested in the current study, with the pitch ratios (p/e)= 5.0 and height ratios (e/H) = 0.330. These cases include: continuous ribs case (CR), intermittent-continuous-intermittent ribs case (ICIR) and intermittent-ribs (IR). Reynolds number (Re) is ranging from 10,000 to 35,000. The experimental work was performed by designed and fabricated test rig while the numerical work was performed in commercially ANSYS Fluent 17.2. the outcomes show that (IR) case offers the best overall performance for all tested velocities, its 1.54 for experimental study and 1.57 for numerical study at Re=10000. Also, the highest friction factor values are found in (IR) case, it is found to be 0.082 in Re=10000.

EXPERIMENTAL AND NUMERICAL STUDY ON EFFECTS OF NEW-GENERATION FINNED HEAT EXCHANGER ON THERMAL PERFORMANCE OF THERMOELECTRIC COOLING SYSTEMS

In this study, an attempt has been made to increase the efficiency of the thermoelectric refrigerator by designinig a new-generation finned heat exchanger. Surface extension, which is one of the most applied passive heat transfer enhancement techniques, was applied for this finned heat exchanger. In this application, the heat absorbed from the cooling room is transferred to the external environment more effectively. In addition, by using an external thermoelectric element (which is installed with the secondary heat exchanger), the heat exchanger cools down faster and the heat is transferred to the environment more quickly. The manufactured cooling system was tested experimentally under different working conditions, including natural and forced convection. The effects of air velocity and applied voltage to the external TE module on thermal performance were examined. Additionally, the external finned heat exchanger has been simulated and heat transfer characteristics have been evaluated using computational fluid dynamics. The lowest and highest COP values have been obtained as 0.003 and 0.011, respectively, when the external TE module has been passive. By providing 12 V for the external TE module, the lowest and highest COP values have been observed as 0.0031 and 0.0042, respectively. In addition, the importance of surface extension applications for the efficient operation of thermoelectric elements has been emphasized.

Evaluating the Performance of Photovoltaic Thermal Systems in Varied Climate Conditions: An Exergy and Energy Analysis Approach

Evaluating the Performance of Photovoltaic Thermal Systems in Varied Climate Conditions: An Exergy and Energy Analysis Approach

Experimental study on the thermal performance of building external window greenery in a subtropical climate

Previous research has found that building greenery systems can cool both buildings and their surrounding environments during the summer. However, the window greenery system, which is a widely adopted form of building greenery, has received limited attention. This study analyzed the thermal performance of window greenery systems in general and the building-integrated window gardens in specific, based on in-situ measurements in a subtropical city. The results show that the cooling effects of the window garden on the envelope were significant near the bottom region. During the air-conditioning period, the heat flux through the bottom wall and windowpane interior surfaces was decreased by 29.0 % and 25.8 %, respectively. A regression model for heat flux through the bottom windowpane was proposed, which estimated that the reduction in radiative heat transfer by plants was 88.0 %. The equivalent heat transfer coefficient for the walls adjacent to the window garden was calculated. Window gardens also improved the outdoor microclimate, reduced the average air temperature over planting troughs by 1.0 °C, and increased the average relative air humidity by around 10.0 % throughout the day. Given that window gardens’ cooling effects strongly depend on water evaporation, a win–win strategy for energy and water saving by harvesting the air conditioning condensate for irrigation is proposed. Based on an estimation, the condensate could fully meet the daily requirements of window greenery, confirming the feasibility of the win–win strategy.

Numerical investigation to optimize the modified cavity receiver for enhancement of thermal performance of solar parabolic dish collector system

The concentrated parabolic dish collector (PDC) systems are widely utilized for the purpose of generating high-temperature heat by receiving and converting solar energy efficiently into thermal energy. Cavity receivers including spiral coils have a common use in PDC system for optimal thermal performance. Therefore, to enhance the thermal performance of a PDC system, the present study investigates different cavity receiver configurations, such as cylinder and conical shaped receivers with flat and spherical absorber surface as well as the effect of spiral coil arrangement. To identify the most optimal spirally coiled cavity receiver, the comparison is conducted based on outlet temperature, heat exchange rate, thermal efficiency, effectiveness, and thermal performance capability (TPC). The investigations were conducted using the ANSYS Fluent CFD simulation software package. The SolTrace software package was utilized to compute the maximum heat flux incident on the absorber surface of the receiver, and peak heat flux data was used as input parameter at the absorber surface of the receiver. Furthermore, to select the suitable working fluid in PDC system, different heat transfer fluids, such as Syltherm 800, Xceltherm 600, ParathermHR™ and water, respectively were studied. From the thermal analysis of various proposed receiver geometries, the receiver with conical shape and spherical absorber surface is more efficient over other configurations. It provides 50 % higher heat transfer rate thancylindrical receiver with flat absorber surface. Moreover, receiver's thermal performance could modestly be improved by modifying the spiral coil pitch (variable pitch). In terms of pumping power consumption, readily availability, low viscosity, and high specific heat, water is suggested as working fluid for receiver of PDC system.

Investigations of Li-Ion Battery Thermal Management Systems Based on Heat Pipes: A Review

Investigations of Li-Ion Battery Thermal Management Systems Based on Heat Pipes: A Review

Simulation of a Thermal Recuperative Incinerator of VOCs with a Special Focus on the Heat Exchanger

Simulation and modeling of thermal recuperative incinerators may play an important role in enhancing efficiency and ensuring compliance with environmental regulations. In this context, the primary objective of this study is to simulate and comprehensively understand the operation of a geometrically complex thermal recuperative incinerator with an integrated preheater featuring varying levels of heat recovery. To achieve this objective, a simple yet effective 0D model was developed. This modeling approach allows for a holistic evaluation of the performance of the incinerator, enabling the assessment of key parameters, such as temperatures and heat transfer rates, under varying operating conditions. Successful validation of the model is established by comparing its results with measurements from an industrial thermal recuperative incinerator in operation at a vehicle assembly plant, with maximum relative differences of around 9%. Simulations for different percentages of flue gases bypassing the preheater were conducted, indicating a good compromise between heat transfer and pressure drop and a 22% heat recovery at around 50%. The model presented in this paper provides a robust foundation for comprehensively assessing and optimizing the performance of thermal recuperative incinerators and systems that comprise thermal recuperative incinerators, with implications for waste management and sustainable energy recovery systems.

Fracture aperture anisotropic effects on field scale enhanced geothermal system thermal performance

The thermal performance of a field-scale Enhanced Geothermal System was investigated, considering anisotropy in fracture aperture distributions. The fracture aperture distribution was treated as an autocorrelated random field with different ranges in the x- and y-directions, defined by geometric anisotropic ratios between 1.5 and 4. To model realistic aperture distributions, constraints were applied to ensure the aperture distributions had Hurst exponents that are typical of fractures observed in nature.The thermal drawdown between the perpendicular and parallel flow configurations was compared, revealing a 60 % likelihood of improved heat transfer in the perpendicular flow configuration. When exploring the impact of geometric anisotropy ratios on thermal performance, aperture distributions with a geometric anisotropy ratio of 2 demonstrated about 70 % better thermal performance in favor of the perpendicular flow direction. This ratio also exhibited aperture distributions with Hurst exponents within the range found in natural faults and fractures, suggesting a 70 % likelihood of improved thermal performance in the perpendicular flow configuration for actual fracture behavior.The perpendicular flow configuration mainly exhibited tortuous flow paths, while the parallel flow direction mostly had near-horizontal flow paths. The tortuous flow paths increased contact between the fluid and fracture surface area, resulting in improved thermal performance.The findings suggest the importance of considering shear direction at the field scale when placing wells. Placing a well perpendicular to the direction of slip or shear may yield enhanced thermal performance compared to placing a well parallel to the direction of slip or shear.

Enhancing thermal comfort and natural ventilation in residential buildings: A design and assessment of an integrated system with horizontal windcatcher and evaporative cooling channels

In this study, researchers investigated the efficacy of natural cooling in a residential building employing a horizontal windcatcher alongside a direct evaporative cooling system featuring a cross-flow pattern. ANSYS Fluent was used to model the three-dimensional airflow, while MATLAB measured the system's thermal performance. The study assessed thermal comfort and natural ventilation in accordance with the Adaptive Thermal Comfort Standard (ATCS) and ISO/EN7730 Standard. The impact of environmental conditions and window aperture on the hybrid system's functionality was scrutinized, culminating in design guidelines dictating the acceptable range of window openings to ensure compliance with thermal comfort conditions. The passive system demonstrated the capability to maintain thermal comfort within the test building under a maximum cooling load of 12,000 W (ATCS) and 6000 W (ISO/EN7730). Moreover, the natural cooling system decreased hourly electricity consumption during hot seasons in Tehran, Iran, by 0.0155 (kW/m2) compared to split air conditioners and 0.00087 (kW/m2) compared to evaporative coolers. The study also investigated the influence of neighboring buildings positioned at specific distances relative to the test building on the system's performance. Furthermore, adopting the suggested horizontal windcatcher instead of conventional vertical windcatchers resulted in a 50 % reduction in energy consumption.

Neural network design for cubic autocatalysis chemical processes, the flow of a Darcy‐Forchheimer viscous fluid is optimized for entropy

AbstractIn this article, neural network backpropagation (NNBP) is used to present two‐dimensional Darcy‐Forchheimer viscous fluid (DFVF) of viscous liquid against a stretching sheet under the influence of heat sink/source and viscous dissipation. Mathematical modelling and numerical simulation are also discussed. Thermal polymer processing, engineering processes, and industrial processes all benefit from the dynamic entropy generation phenomenon. Scientists are primarily interested in finding ways to decrease entropy formation to polish up the thermal performance of industrial systems. In this continuation, the optimal frame for the Darcy‐Forchheimer flow with a curved surface has been developed. Non‐linear partial systems are converted to dimensionless differential systems through the employment of the appropriate variables. Utilizing tools from the bvp4c method, the problem's highly nonlinear equations are numerically solved. These ODEs are solved by applying the bvp4c solution approach to produce the reference dataset for NNBP. Using this reference dataset in MATLAB, the graphs for the solution and error analysis for changing various parameters are analyzed. The performance of NNBP is validated using mean squared error data, regression analysis, and error histogram. The DFVF solution is examined using the testing, validation, and training procedures. Examined through influential variables the effects of fluid flow, thermal field, Bejan number, and concentration.

Effect of α-methyl on the performance of photocurable 3D printing polyurethane materials

For photosensitive polyurethane systems, reactive diluents are indispensable components whose main role is to reduce the viscosity of the polyurethane prepolymer to meet the requirements of the photocurable 3D printing technology for high fluidity of the precursor solution. Generally, the reactive diluent would be involved in the photocuring reaction, which in turn has a remarkable impact on the mechanical, reaction kinetics, and thermodynamic characteristics of the photosensitive polyurethane system. However, this feature is usually neglected in the study of photosensitive urethane acrylate (PUA) systems, so there is a considerable necessity to investigate the mechanism of active diluents in the photocured reaction of PUA systems. In this work, the effects of α-methyl groups along the chains of diluent molecules on the photoreaction kinetics, photocurable 3D printing, mechanical and mechanical properties, and thermodynamic characteristics of PUAs were investigated employing hydroxyethyl methacrylate and hydroxyethyl acrylate as active diluents, respectively. The relationship between chemical structure and kinetics of PUA systems was also elucidated by using dynamic mechanical analysis tests. The results demonstrated that the α-methyl group blocks the migration of reactive radicals, reduces the efficiency of the photoreaction, and causes an increase in the rigidity and strength of the molecular chain. This study not only revealed the effect of α-methyl on the kinetic mechanical and thermal performance of PUA systems but also paves the way for the development of a new class of photosensitive PUA materials used for the photocurable 3D printing technology.

Numerical Investigation of Phase Change Material-Based Hybrid Battery Thermal Management System for Mass Optimization

In this work, a hybrid battery thermal management system using active cooling and Phase Change Material (PCM) has been studied. The additional weight of PCM poses design challenges, and hence its optimization is required. In this regard, a PCM enclosure of a cylindrical structure with six cylindrical cells is considered in 6-row and 1-column arrangement in the present work. The thermal performance of the proposed system is numerically investigated with different thicknesses of PCM layers at constant heat generation and coolant (air) flow rates. It is found that the battery thermal management with only PCM shows unsatisfactory performance under extended severe operating conditions. However, the addition low-flow convectional cooling improved the performance and the system’s reliability. It is found that for the proposed system, PCM thickness of 1 mm for the first battery cell and 2 mm for the subsequent battery cells help in better heat dissipation showing minimal thermal non–uniformity (1.1 °C) and reduced maximum temperature (39.6 °C) within the battery pack. Consequently, the optimized system shows 68.3% reduction in PCM mass as compared to the case of uniform thickness of the PCM.

Effect of non-uniform heat rise/fall and porosity on MHD Williamson hybrid nanofluid flow over incessantly moving thin needle

In this work, a novel enhanced model of the thermophysical characteristics of hybrid nanofluid is introduced. An innovative kind of fluid called hybrid nanofluid has been engineered to increase the heat transfer rate of heat and performance of thermal system. A growing trend in scientific and industrial applications pushed researchers to establish mathematical models for non-Newtonian fluids. A parametric study on theheat transfer and fluid flow of a Williamson hybrid nanofluid based on AA7075-AA7072/Methanol overincessantly moving thin needle under the porosity, Lorentz force, and non-uniform heat rise/fallis performed. Due to similarity variables, the partial differential equations governing the studied configuration undergo appropriate transformation to be converted into ordinary differential equations. The rigorous built-in numerical solver in bvp4c MATLAB has been employed to determine the numerical solutions of the established non-linear ordinary differential equations. It is worthy to note that velocity declines for both AA7075/Methanol nanofluid and AA7075- AA7072/Methanol hybrid nanofluid, but highervelocitymagnitudes occur for theAA7075/Methanol whilethe Williamson fluid parameters increased. It is alsoconcluded that as the porosity parameter isincreased, the flow intensity decreases gradually. It is worthy to note that for both non-uniform heat-rise and fall parameters, the temperature of the fluid gets stronger. Mounting valuesof needle thickness parameter leads to reduction in fluid speed and temperature. It is noticedthat as volume fractions of both types of nanoparticles are augmented then fluidvelocity and temperature amplify rapidly. A Comparison of current and published results is performed to ensure the validity of the established numerical model.

Conceptualization of a novel battery thermal management system based on capillary-driven evaporative cooling

In conventional heat pipe based battery thermal management systems the thermal contact between the battery and the heat pipe is enhanced by means of heat conductive elements. These additional elements introduce multiple layers of thermal resistance and contribute to increased weight. This paper aims to address this issue by minimizing the contact thermal resistance and potentially reduce this additional weight. The proposed solution relies on capillary-driven evaporative cooling (CDEC), wherein a wick structure is directly integrated onto the battery's surface to enable direct cooling. To demonstrate this concept, an experimental study was conducted by affixing a Copper foam to an emulated battery block, and using ethanol and Novec 7000 as cooling media. The CDEC system's thermal performance was assessed under three heating conditions, and different operating conditions. The results indicated that the copper foam with higher pore density outperformed the other due to its greater wetting height. The maximum cell surface temperature was maintained around 40 °C for a continuous 50 W heat input. Furthermore, the thermal resistance of the system was lowered by a factor of 6 compared to an air-cooled system. The thermal resistance ranged from a minimum of 0.32 to a maximum of 1.5 K/W, which were comparatively low compared to some existing battery thermal management system designs. This paper introduces an innovative battery cooling concept, presents experimental evidence of its feasibility, and demonstrates its ability to effectively regulate battery temperature within acceptable limits even under high heat loads, while minimizing overall thermal resistance.

A CFD modelling for optimizing geometry parameters for improved performance using clean energy geothermal ground-to-air tunnel heat exchangers

In this numerical study, different geometric parameters have been optimized for improved performance using a clean energy geothermal Ground to Air Tunnel Heat Exchanger (GATHE). A commercial computational fluid dynamic code ANSYS Fluent was used, and the code has been validated with the available experimental and analytical results. Three soil samples were used to analyze the thermal properties, each with a thermal conductivity of 0.65, 1.25 and 3.50 Wm−1K−1. The critical soil thickness was found to be 10 times the pipe diameter and the lowest outlet temperature of 300.1 K was achieved for a 60 m pipe with a soil thermal conductivity of 3.50 Wm−1K−1. To further enhance the performance of the system, multiple fin arrays were introduced into the ductwork at 0.5 m, 1.0 m and 2.0 m pitches. For a 10 m long pipe with fins installed every 0.5 m, an outlet temperature of 306.7 K was observed. With 4 fins for temperature variation, performance increased by 19.4 % compared to the case without fins. When the fin spacing is 1 m, the temperature drop increases by 5.6 %, and when the fin spacing is 2 m, the temperature drop increases to 7 %, with an outlet temperature of 306.1 K. Finally, a novel set of multiple blocks in diverging and converging patterns was introduced to restrict airflow and further improve heat dissipation. Compared to a single-fin block, the outlet temperature of the 4-fin block was reduced by 14.52 % due to the increased contact area, thus improving the thermal performance of the heat exchanger system.

Analyzing competing effects between heat transfer area and natural convection to enhance heat transfer in latent heat storage

Phase change materials (PCMs) are effective means of storing thermal energy and to balance temporal supply-demand mismatch. To enhance heat transfer within the PCM, internal fins are often employed to increase the heat exchange area, but they usually suppress simultaneously natural convection reducing the performance of the PCM storage. To better understand these two conflicting effects and to find a better trade-off between the different heat transfer means, a comprehensive numerical study of PCM storage with different fin shapes (straight and sinusoidal wavy fins) and surface areas, but with equivalent volume fraction, was accomplished. The results show that increasing the surface area of sinusoidal fins improves only marginally the heat transfer, mainly because the flow velocity of natural convection along the normal direction of the solid interface is inhibited. The velocity normal to the solid interface was found to be the most critical factors to the overall heat transfer efficiency of the system and to the time needed to complete the phase change in the PCM container. The study clearly shows that to enhance the heat transfer in PCM, the effects from natural convection (direction and strength) play a more important role than the heat exchange surface area. To improve the thermal performance and efficiency of PCM storage systems both factors need to be combined in an optimal way.

The Influence of Nanofluid Characteristics on the Thermal Performance of Photovoltaic Thermal System

Optimal solar energy utilization can be achieved with a Photovoltaic Thermal (PVT) system, which simultaneously produces electricity and heat. PVT generally uses water as heat transfer fluid to cool the PV cells while transporting heat for other purposes. However, water has low thermal conductivity and capacity as a heat transfer fluid. Nanofluid, which is popular in heat exchanger applications, has also been researched and tested for use in improving the performance of PVT systems. The superior thermal conductivity of nanofluid could produce a PVT system efficiency of up to 89.75%. However, nanofluid applications in the PVT system still face challenges, especially in their preparation and properties. This study determines the properties of nanofluids that could improve the electrical and thermal performance of PVT systems. The authors found that preparation procedures for manufacturing nanofluids were essential for researchers to consider before applying nanofluids. Also, some disadvantages of nanofluids are still an obstacle in their application, especially economic issues and adverse environmental effects.