Improvement In Thermal Performance Research Articles

Thermal Regulation and Performance Improvement of Solar PV Panel Using PCM OM29

Thermal Regulation and Performance Improvement of Solar PV Panel Using PCM OM29

A Comparative Assessment of Different Aerogel-Insulated Building Walls for Enhanced Thermal Insulation Performance.

Aerogel is widely recognized as a superinsulating material with great potential for enhancing the thermal insulation performance of building walls. It can be applied in various forms such as aerogel plasters (AP), aerogel fibrous composites (AFC), and aerogel concrete (AC) in practical engineering applications. This study aims to investigate the most efficient application form for maximizing building insulation performance while minimizing the amount of aerogel used. To predict the thermal insulation performance of aerogel-insulated walls, a resistance-capacitance network model integrating the aerogels' effective thermal conductivity model was developed and was validated by comparing it with Fluent simulation software results in terms of surface temperature. Using the validated models, the thermophysical parameters, transient thermal properties, and transmission load were predicted and compared among AP, AFC, and AC walls. The results indicate that using AFC can result in approximately 50% cost savings to achieve the same thermal resistance. After adding a 20 mm thickness of aerogel to the reference wall without aerogel, the AFC wall exhibited the highest improvement in thermal insulation performance, reaching 46.0-53.5%, followed by the AP wall, and then the AC wall, aligning with considerations of microstructural perspectives, thermal resistance distributions, and thermal non-uniformity factors. Therefore, giving priority to AFC use could reduce the required amount of silica aerogel and enhance economic efficiency. These results provide valuable insights for theoretical models and the application of aerogel-insulated walls in building engineering insulation.

Comparative analysis of thermal performance for precast panel systems with conventional and innovative insulation materials

ABSTRACT Precast facades are one of the most popular technology solutions featuring high-quality implementation and installation. They consist of three layers, both the external and internal layers are concrete composite, where the core is a thermal insulation material. This study explores the thermal performance improvement of these locally manufactured panels and evaluates their effectiveness in supporting building sustainability and energy saving. The study is performed experimentally. Leca and Addipor aggregates were used as a replacement of mix aggregate to produce lightweight heat-insulating concrete. Compressive strength equals 15MPa were taken for both Leca and Addipor replacement ratio. The study simulates several sections of precast concrete panels using ANSYS. Proposed concrete models with traditional and innovative thermal insulation materials, which are Expanded Polystyrene Foam (EPS), Extruded Polystyrene Foam (XPS), Rigid polyurethane foam (PU) and Vacuum insulation panels (VIPs), were analyzed. In addition, a virtual room space was simulated thermally using the previous sections to perform thermal simulations, as rate of heat transfer and amount of energy savings. The use of polyurethane foam (PU) as a new thermal insulation material and vacuum insulation panels (VIP) as an innovative thermal insulation material helps to reduce energy consumption by a rate of 143% and 700% of conventional insulation materials (EPS), respectively. It achieves internal thermal comfort and supports building sustainability.

Enhancing battery module safety with insulation material: Hollow glass microspheres incorporating aerogel of varying particle sizes

Thermal runaway propagation (TRP) in lithium-ion batteries (LIBs) poses a critical safety concern, hindering their widespread application. In this study, we present a novel thermal insulation material designed to effectively mitigate TRP in LIBs. The material comprises a mechanical support framework consisting of hollow glass microspheres (HGMs) and acrylic emulsion, filled with aerogel particles (APs). We systematically investigate the influence of HGMs and APs addition on the properties. The findings reveal a positive correlation between HGMs and mechanical properties, as well as APs and thermal insulation properties, at appropriate addition levels. The optimal insulation material exhibits exceptional compressive strength (1.42 MPa), achieves a UL-94 V-0 flame retardancy rating, and demonstrates high thermal insulation performance (44.3 mW·m−1·K−1). Moreover, we explore the impact of strain on thermal insulation performance, observing a gradual increase in thermal resistance loss with higher strain. Notably, even at a strain of 70 %, the thermal conductivity experiences only a modest increase from 44.3 to 52 mW·m−1·K−1. Additionally, we evaluate the effect of APs size on the material's properties, finding that decreasing particle size from 50 to 5 μm leads to a reduction in mechanical properties (1.42 to 1.12 MPa) but an improvement in thermal insulation performance (44.3 to 39.7 mW·m−1·K−1). Finally, we validate the practical efficacy of the insulation material in preventing TRP through the use of a 2 mm thickness. This study presents a promising approach to enhance the safety of LIBs by developing an efficient insulation material with outstanding properties.

Evaluation of an integrated electric power generation system with natural gas engines operating in dual mode through heat recovery with thermoelectric devices for hydrogen production

In the present investigation, an environmental, thermal, economic, and social analysis of an integrated system is carried out, which has as its function the production of hydrogen through the recovery of residual thermal energy from exhaust gases. The proposed integrated system consists of a thermoelectric generator and a hydrogen production bench based on the water electrolysis process. For the development of the research, an internal combustion engine fueled with natural gas was used, operating under four load conditions (25%, 50%, 75%, and 100%). From the environmental assessment, it is demonstrated that the implementation of the integrated system allows a decrease of 12.30%, 6.26%, and 7.90% in CO, CO2, and HC emissions. However, the addition of hydrogen causes a 9.9% increase in NOx emissions. Additionally, the implementation of the integrated system allows a 4.9% decrease in brake specific fuel consumption and a 4.9% increase in engine thermal efficiency. The improvement in engine thermal performance contributes to the 7% reduction in engine operating costs. On the other hand, it demonstrates an 8.7% reduction in the environmental and social impact cost and a 9% reduction in the ecological cost. Additionally, the integrated system minimizes the cost of environmental and social impact, as well as the ecological cost of polluting gases CO, CO2, and HC. The mixture of natural gas and hydrogen allows for a 4.70% and 7.59% increase in pressure and maximum heat release rate. In general, the proposed integrated system is a way to harness the thermal energy of exhaust gases for hydrogen production. In this way, it is possible to obtain an auxiliary fuel that improves the efficiency of the combustion process of the natural gas engine. This allows for minimizing energy losses in self-generation activities in Colombia, achieving better energy management and a reduction in operating costs.

Impact of jet intermittency on surface-structured heat sinks for electronics liquid cooling

The boosting heat generation rate of high-performance processors is challenging the conventional cooling techniques. Passive surface structure designs no longer satisfy the heat dissipation requirement. The present work proposes the combined design of active jet intermittency and passive surface modification in heat sinks, and evaluates the heat transfer enhancement through numerical and experimental approaches. The trapezoidal-waveform flow rate at the inlet has constant time-averaged Reynolds number of 763 and the Strouhal number ranges from 0.01 to 0.04. The surface geometry includes cylindrical groove and hemispherical dimple with different arrangements. The underlying physics of thermal performance improvement is explained by complex flow circulation that disrupts the thermal boundary layer growth and dynamic vortex motion that promotes mixing between near-wall fluid and mainstream coolant. Higher pulsation frequency and smaller duty cycle are beneficial for cooling enhancement while the percentage improvement of dimple structure is higher than groove structure, which agrees with the experimental results. Compared to the steady-flow flat heat sink, a maximum enhancement of 45% is obtained by adopting intermittent jet at grooved surface.

Thermal performance improvement of a circular tube-and-fin heat exchanger by ellipsoidal protrusions on fin surfaces

A novel fin stamped out with ellipsoidal protrusions is proposed to improve the performance of a circular tube-and-fin heat exchanger in this paper. The ellipsoidal protrusions have a similar function as the traditional plane or curved vortex generators that can generate longitudinal vortices in the flow channel. The effect of different attack angles of the ellipsoidal protrusions on the thermal performance of a circular tube-and-fin heat exchanger is numerically analyzed. The turbulent flow and heat transfer properties were investigated by Standard k-ε turbulence model with finite volume method. The results illustrated that the ellipsoidal protrusions can substantially improve the intensity of secondary flow and enhance the heat transfer. The ellipsoidal protrusions exhibited better heat transfer than the traditional vortex generators. Nu of the fin with ellipsoidal protrusions increased up to 31.73 % and 19.95 % compared with the smooth fin and the fin with vortex generators, respectively. Both Nu and f of the fin with ellipsoidal protrusions increased with the increase in attack angle. An optimum attack angle of 20° of the ellipsoidal protrusion existed for the highest thermal performance factor of 1.165. Fitted equations for Nu, f, and JF were provided for facilitating application to engineering.

Optimization design method of material stiffness of contact interface considering surface roughness for improving thermal contact performance

The contact interface of precision mechanical equipment, such as electronic equipment, is the crucial medium for transferring internal loads and physical properties and realizing the intended function of the equipment. The thermal contact performance of precision mechanical equipment determines its overall thermal performance. Previous studies have consistently ignored the activeness of differential distribution of contact interface material stiffness in improving thermal contact performance. Therefore, this paper creatively proposed a new idea to improve thermal contact performance by designing the material stiffness of the contact interface. Firstly, based on the precise analysis model of thermal contact performance considering surface roughness, a heuristic-based optimization design method of material stiffness of contact interface was developed, which took the contact interface temperature distribution non-uniformity (CITDN) and thermal contact resistance (TCR) as the optimization objectives. Then, based on this method, the optimization designs of electronic chip packaging and proton exchange membrane fuel cell (PEMFC) were carried out. The results showed that after optimization, the TCR and CITDN of the electronic chip package were reduced by 83.23% and 92%, respectively, and the TCR and CITDN of PEMFC were decreased by 99.78% and 88.71%, respectively. This method achieved a substantial improvement in thermal contact performance.

Thermal insulation performance of rock wool reinforced kaolinite-based porous geopolymer

The development of thermal insulation materials with superior comprehensive properties is crucial to building energy conservation. This paper presents a kaolinite-based porous geopolymer type composite thermal insulation material through alkali activation, room temperature foaming technology, and the rock wool fiber reinforcement. The effects of rock wool fiber contents and heat treatment on the comprehensive properties of the kaolinite-based porous geopolymer were investigated. The addition of rock wool fiber can enhance the mechanical properties of kaolinite-based porous geopolymer, while heat treatment can generate a hierarchical porous structure, resulting in a dramatical improvement in thermal insulation performance. With a rock wool fiber content of 15 wt%, the sample exhibits a porosity of ∼90%, density of 0.118 g/cm3, thermal conductivity of 0.057 W/(m·K), and a maximum compressive strength of 0.66 MPa, increased by ∼22% compared to samples without addition of rock wool. Additionally, the optimized thermal insulation material followed waterproofing treatment exhibits excellent hydrophobicity with a contact angle of up to 98.5°. Therefore, this novel thermal insulation material not only has a simple manufacturing process and eco-friendly properties, but also showcases properties including lightweight construction, high strength, and low thermal conductivity. Consequently, it holds immense potential in the area of building energy conservation.

Layered Inorganic Silicate Aerogel Pillared by Nanoclusters for High Temperature Thermal Insulation.

Layered inorganic material, with large-area interlayer surface and interface, provides an essential material platform for constructing new configuration of functional materials. Herein, a layered material pillared with nanoclusters realizing high temperature thermal insulation performance is demonstrated for the first time. Specifically, systematic synchrotron radiation spectroscopy and finite element calculation analysis show that ZrOx nanoclusters served as "pillars" to effectively produce porous structures with enough boundary defect while maintaining the layered structure, thereby significantly reducing solid state thermal conductivity (≈0.32Wm-1 K-1 , 298-573K). Moreover, the layered inorganic silicate material assembled aerogel also exhibits superior thermal insulation performance from room temperature (0.034Wm-1 K-1 , 298K, air conditions) to high temperature (0.187Wm-1 K-1 , 1073K, air conditions) and largely enhanced compressive strength (42kPa at 80% compression), which is the best layered material-based aerogel that has achieved synergistic improvement in thermal and mechanical performance so far. Layered inorganic silicate aerogel pillared by nanoclusters will pave a new avenue for the design of advanced thermal insulation materials under extreme conditions.

Experimental study on the thermal performance of a liquid-cooled heat sink integrating heat pipes for dual CPU servers

The increasing power consumption of server CPUs poses a challenge for data center cooling. In this work, a liquid-cooled heat pipe heat sink (LHPHS) with compactly arranged heat pipes is designed and fabricated for CPU cooling in dual CPU servers. Water is selected as the working fluid in the heat pipes. Experiments are conducted to explore the heat dissipation potential of LHPHS under high inlet coolant temperature and high heat load conditions, and to investigate the operational stability of LHPHS under the conditions of uneven heat generation between two CPUs. Furthermore, a one-dimensional thermal resistance network and numerical model of the LHPHS are established to quantitatively analyze the thermal resistance distribution of LHPHS and the variation of thermal resistance with coolant flow rate. The results show that, firstly, the LHPHS operates stably under high inlet coolant temperature and high heat load conditions, meeting the heat dissipation requirements of up to 37.5 W/cm2 with a coolant flow rate of 1 L/min and inlet coolant temperature of 35℃. Secondly, the LHPHS exhibits excellent performance in controlling temperature difference between CPUs and even when there is discrepant heat generation between them. Thirdly, the LHPHS performs a low thermal resistance, measuring 0.044 ℃/W at a coolant flow rate of 0.5 L/min, and this resistance further decreases as the flow rate increases. Additionally, it is observed that the thermal resistance of the liquid-cooled plate decreases with the increasing flow rate, and heat transfer within the heat pipes becomes a critical aspect under high coolant flow rates. Therefore, reducing the thermal resistance of the heat pipe is crucial for the thermal performance improvement of the LHPHS.

Thermal Performance of Autocatalytic Chemical Reaction for Hybrid Nanomaterial Fluid Flow

The mass and heat transfer in hybrid magnetohydrodynamic (MHD) nanofluids is controlled by an autocatalytic chemical mechanism, which is the subject of the current study's thorough analysis. The focus of the work is on the nanolayers at interfaces, which link nanoparticles with the supporting fluids and enable coupled mass and heat transfer phenomena.To further investigate its effects, a uniform transverse magnetic field is added to the study.By using similarity methods, the governing nonlinear coupled partial differential equation that describes this sophisticated system is converted into a collection of ordinary differential equations (ODEs). Two numerical approaches( Bvp4c) and the Shooting method, are used to solve the ODEs in order to get precise answers and do a comparison study. One interesting finding about the improvement of thermal performance is that a rise in nanolayer thickness (between 1 and 4) considerably adds to the enhancement. Additionally, it is discovered that improvements in the chemical reaction parameter, which ranges from 0.15 to 0.27, cause the Sherwood number to rise.It is noteworthy that the results of this study add to a better understanding of the complex interactions between magnetohydrodynamics, chemical processes, and nanofluid dynamics. The numerical techniques used highlight the significance of accurate mathematical modeling in illuminating the complexity of such systems. In addition to strengthening the theoretical foundation, this study offers useful information that could have an impact on heat transfer and nanofluid technology applications.

A study of thermal performance enhancement of building envelopes by using corncob as construction material

The energy-saving design of buildings effectively reduces heating energy consumption, improves indoor environmental problems in traditional houses, and plays an essential role in alleviating the increasingly severe environmental and energy problems. This study reviews the status of research on building energy-saving renovation and environmental improvement in various countries and summarizes their relevant research experiences. It described the theories and methods of survey, experiment, and numerical simulation to provide a theoretical basis for energy-saving renovation and environmental improvement of residential houses. Furthermore, it introduces corncob concrete material to provide new materials for the renovation of an old building. This research is based on the coastal Liyuan houses in Qingdao, and the problems of Liyuan houses are identified through in-field investigation. Then, through experimental simulations, the application and efficiency of corncob materials in the thermal performance improvement of the envelope are explored. The renovation of old residential houses in terms of energy-saving and environmental improvement is proposed from envelope renovation.

Thermal performance improvement of a radial pulsating heat pipe with diverging channels by adopting Tesla valves at various heat fluxes

The thermal performance of a pulsating heat pipe (PHP) can be improved by increasing the flow circulation with the adoption of novel channel designs to minimize flow resistance. This study aimed to improve the thermal performance characteristics of a radial PHP with diverging channels by adopting Tesla valves. The effects of heat flux, condensation temperature, and heat transfer area ratio on the thermal resistance and heat transfer coefficient of the PHP with Tesla valves were measured under different heating and cooling conditions. In addition, the flow behaviors and pressure variations were analyzed for a short time frame. The PHP with Tesla valves exhibited a 17 %-lower thermal resistance than that without Tesla valves owing to the increased flow circulation with preferential movement in one direction. Furthermore, the heat transfer capability of the PHP with Tesla valves increased with increasing condensation temperature and heat transfer area ratio at the same heat flux. In addition, the optimal filling ratios were determined to be 70, 80, and 90 % for heat transfer area ratios of 0.13, 0.08, and 0.05, respectively. Finally, contour maps for the maximum temperature deviation were developed in terms of the heat flux, heat input, and heat transfer area ratio.

Thermal performances of pumped thermosyphon loops with evaporator configured by serpentine ribbed channel with and without internal effusion

Thermal performances of two pumped thermosyphon loops (PTL) with the evaporator configured by the serpentine ribbed channel with or without the internal effusion are studied. The boiling flow structure, thermodynamic cycle, phase-change heat transfers, and thermal resistance of each loop are compared. With effusion, the evident pressured-drop reduction across the evaporator has led to the decreased boiling temperature and the shrunk sub-cooling region in the evaporator to promote the PTL performance. The merit index that assesses the reductions of loop thermal resistance and total pumping power consumption affirms the considerable thermal performance improvement by the internal effusion in evaporator. Relative to the PTL without effusion, the loop thermal resistance is reduced by 3–32% with the coefficient of performance raised by 14–207%.

Experimental study on thermal performance of a closed heat pump drying system

The compressor speed, expansion valve opening and drying temperature are critical to the thermal performance improvement and control logic optimization of the closed heat pump drying (CHPD) system. This paper investigates the effects of the three parameters on the thermal performance of the CHPD system by the single factor experiment method. According to the experimental findings, as the compressor speed of the system increased, the heating capacity grew by 11.4%, but the coefficient of performance (COP) declined by 41.3%. As the expansion valve opening of the system increased, the heating capacity and COP grew by 73.5% and 82.9%, respectively. As the drying temperature of the system rose, the heating capacity grew by 3.1%, but the COP dropped by 25.3%. It can be concluded that reducing the compressor speed and drying temperature, and increasing the expansion valve opening could effectively enhance the thermal performance of the CHPD system.

Improvement of thermal insulation performance of precast concrete curtain walls for apartment buildings

Improvement of thermal insulation performance of precast concrete curtain walls for apartment buildings

Quantitative review on recent developments of flat-plate solar collector design. Part 1: Front-side heat loss reduction

Several studies demonstrated novel and effective design solutions for the FPC thermal performance enchantment by the front side heat loss reduction. However, these design improvements were tested under different climatic and operating conditions. This fact makes it almost impossible to compare these design improvements. The following study quantitatively analyses the current flat-plate solar collector design developments, focusing on reducing front-side heat loss. It also performs a simulation analysis to demonstrate the thermal performance improvement of the chosen design solutions for three specific applications. The literature review was performed to identify the most promising design solutions. Then, the considered design solutions were modelled using the validated detailed theoretical model of a flat-plate solar collector (FPC). Finally, the modelling results were used to perform the thermal performance simulation analysis for Würzburg (Germany) climatic conditions and constant mean fluid operating temperatures of 50, 75, and 100 °C. The simulation results indicated that applying the considered design solutions to decrease the front-side heat losses could significantly increase the FPC thermal performance. Moreover, for high-temperature applications, where the front-side heat loss is a crucial factor determining the FPC thermal performance, there is more than a significant potential for the FPC thermal performance enchantment. To sum up, our findings indicate a significant thermal performance improvement potential that could increase the application range of FPCs and make them more competitive for a broader application area.

Thermal performance improvement of PCM layers

Thermal shielding through phase change material wallboards exposed to oscillating temperature conditions has been previously studied by several authors. PCM layers provide thermal comfort by releasing(absorbing) latent heat energy, constituting a sort of active cooling(heating) system produced by the dynamics of liquid-solid interfaces. In this work, the effect of volume displacements in the thermal performance of PCM wallboards is analyzed. The thermal energy released(absorbed) at the inner wall is greatly affected by the dynamics of volume displacements and the formation of one or more interfaces, when exposed to temperature oscillations around the melting point of the material. Equations of motion for the thickness of the PCM layer and interfaces, are derived. Volumetric effects produced by the sharp density change of liquid-solid transitions as well as the thermal expansion of each phase are considered in the analysis. We found that the term proportional to the expansion coefficient that appears in the equations of motion is negligible. The effect is hidden by volume displacements produced through the density difference between phases. Semi-analytical methods were used to solve the equations of motion described in this work. We found that the thermal energy released(absorbed) is deeply affected by the initial configuration of phases and the time instant of exposure to ambient conditions. Thermal shielding can be improved through PCM preparation and time of installation, according to the results found in this work. Finally, examples with two alkanes are provided when the external wall is exposed to different weather conditions.

Experimental investigation of blended H2/CH4 combustion in combustors with block for micro-thermophotovoltaic

To extend the operation conditions and improve the working performance of micro-thermophotovoltaic system, the combustor with varied block setting and length is proposed, where blended CH4/H2 is employed. Effects of CH4 addition, burner dimensions and parameters on combustion characteristics, energy conversion and multi-factors on working performance are investigated under various flow rates. Results demonstrate that the consumption and production of OH and H radicals are strongly impacted by the CH4 blending ratio, affecting the flame regime, burning heat release and heat transfer in the combustion chamber. And 5–15 % CH4 addition is beneficial to the improvement of burner thermal performance, where the highest radiation temperature is achieved at mCH4 = 15 % in combustor C24-0.4 under lower fuel flow rate, while it is also affected by the burner setting. A higher CH4 mixing ratio contributes to the combustor with thin block and the thicker block with lower CH4 addition can both contribute to achieve a better working performance. Besides, the augment of burner length extends the operating conditions and the radiant area, while it reduces Tw, and combustor C29-0.6 obtains the highest radiation power of 48.1 W and electrical power output of 2.9 W with a system efficiency 2.2 % at mCH4 = 10 %, Vf = 635 mL/min and Φ = 1.0. So, the appropriate CH4 addition, block setting and burner size can yield enhanced system performance.