Amount Of Heat Research Articles

Economic and Environmental Benefits of Heating of Poultry Houses with Geothermal Energy: A Case Study for Nevşehir Province of Turkey

In this study, as an example of the use of geothermal energy resources for the air-conditioning of animal shelters, the technical, economic and environmental gains that will be achieved in the case of heating a chicken coop with a total floor area of 480 m2 in Nevşehir province of Turkey in the winter months have been evaluated. For this purpose, a standard chicken coop with a length of 40 m, a width of 12 m and a height of 2.5 m and a capacity of 4320 chickens has been considered. The optimum indoor temperature for adult chickens is considered to be 22 °C. The total heat losses related to the different structural components of the considered standard house were determined. The annual total highest heat load for the poultry house was calculated as Qt = 197.32 kW. For geothermal resources suitable for house heating in the region, the amount of heat to be gained from the geothermal fluid to the house environment was calculated, taking into account the lowest physical properties (the lowest temperature Tgeo = 30 °C and the lowest flow rate mgeo = 30 m3/h). Since the amount of heat energy gained to the poultry environment with geothermal fluid (Qgeo=278.96 kW) is higher than the total heat losses (Qt = 197.32 kW) of the poultry house (Qgeo>Qt), it can be used for poultry heating with geothermal fluid. In case the considered poultry house is heated with geothermal energy, a total of 45073 kg of fuel will be saved annually from LPG consumption and 42186.4 kg of diesel fuel consumption will be saved. If Diesel or LGP fuel is used instead of geothermal fluid for poultry heating, the annual total fuel cost will be 266 211.6 TL for LPG usage and 274 585.2 TL for Diesel usage. In case the considered house is heated with geothermal energy, 136 571.2 kgCO2-eq or 133 798.3 kgCO2-eq from the annual total greenhouse gas emissions will save compared to the use of LPG and Diesel, respectively.

BEM Modeling for Stress Sensitivity of Nonlocal Thermo-Elasto-Plastic Damage Problems

The main objective of this paper is to propose a new boundary element method (BEM) modeling for stress sensitivity of nonlocal thermo-elasto-plastic damage problems. The numerical solution of the heat conduction equation subjected to a non-local condition is described using a boundary element model. The total amount of heat energy contained inside the solid under consideration is specified by the non-local condition. The procedure of solving the heat equation will reveal an unknown control function that governs the temperature on a specific region of the solid’s boundary. The initial stress BEM for structures with strain-softening damage is employed in a boundary element program with iterations in each load increment to develop a plasticity model with yield limit deterioration. To avoid the difficulties associated with the numerical calculation of singular integrals, the regularization technique is applicable to integral operators. To validate the physical correctness and efficiency of the suggested formulation, a numerical case is solved.

Waste-to-energy power plants: Multi-objective analysis and optimization of landfill heat and methane gas by recirculation of leachate

Elevated thermal energy trapped in landfill voids is a potential threat to humans since, fires might get ignited, eventually releasing poisonous gases, contaminated fluids (leachate), and abnormal quantity of heat. This study explores the practical potential of landfills to produce heat and methane gas through a leachate recirculation process, which involves returning nutrient-rich fluids to landfills to maximize electricity generation. This paper presents an experimental investigation of the physio-chemical properties of landfills by recirculating leachate to achieve sustainable performance characteristics of landfill models. Five input parameters i.e. waste particle size (WPS in mm), waste addition (WA in Ktoe), inorganic matter content (IO in %), leachate recirculation rate (LRR in liters/day), and age of landfill (LA in years) each at five levels is considered. The investigation is accomplished on the central composite rotating design (CCRD) matrix with a 5-level factor. The results reveal that WPS at D10, WA at 52.32 Ktoe, IO at 2%, LRR at 300 l/day, and LA at 4.07 year is the optimal setting of the input parameters that produce optimum values of the output responses considered simultaneously. An innovative method is studied for simultaneously lowering the internal temperature of landfills to ideal levels while also enhancing the rate of methane production. Energy transfer to the ORC system is 2.3 GJ in winters while 1.5 GJ in summers. Landfills equipped with leachate recirculation facilities provide 2.2 times more energy with stabilization occurring in 4th year with an energy content of 950 MJ/m3 of waste.

Analysis of Anthropogenic Waste Heat Emission from an Academic Data Center

The rapid growth in computing and data transmission has significant energy and environmental implications. While there is considerable interest in waste heat emission and reuse in commercial data centers, opportunities in academic data centers remain largely unexplored. In this study, real-time onsite waste heat data were collected from a typical academic data center and an analysis framework was developed to determine the quality and quantity of waste heat that can be contained for reuse. In the absence of a comprehensive computer room monitoring system, real-time thermal data were collected from the data center using two arrays of thermometers and thermo-anemometers in the server room. Additionally, a computational fluid dynamics model was used to simulate temperature distribution and identify “hot spots” in the server room. By simulating modification of the server room with a hot air containment system, the return air temperature increased from 23 to 46 °C and the annual waste heat energy increased from 377 to 2004 MWh. Our study emphasizes the importance of containing waste heat so that it can be available for reuse, and also, that reusing the waste heat has value in not releasing it to the environment.

Graph convolution network-based surrogate model for natural convection in annuli

This work develops a model for natural convection in annuli with internal heat sources based on Graph Convolution Network (GCN), achieving rapid prediction by directly establishing the mapping relationship between the geometric features and the temperature field. The GCN learns node features and connections between nodes in data structures. Compared with traditional machine learning networks, GCN exhibits greater advantages in handling complex geometric shapes and unstructured nodes. In this study, numerous data samples were constructed with various geometric features, e.g., varying sizes, positions, and quantities of internal heat sources. The results indicate that a fully trained GCN was capable to adaptively predict temperature field distributions with arbitrary heat source sizes, positions, and quantities. The mean prediction errors of GCN for the temperature field are around 0.17 %, 0.32 %, and 0.85 %, for the single, double, and triple heat sources cases, respectively. Furthermore, the GCN prediction performance was also compared with surrogate models by the convolutional, and fully connected neural networks (CNN and FNN), which shows an improvement of 88.1 % and 84.8 %, respectively. Therefore, compared with numerical results and other surrogate models, the proposed model presents superior geometric adaptability, high prediction accuracy and a remarkable enhancement in computational efficiency (three orders of magnitude).

Effect of grinding parameters and coolants on grindability of Ti grade 9 alloy

For many years, surface roughness has drawn considerable attention, and it is a crucial design element in a variety of circumstances, including components sensitive to fatigue stresses, precision fittings, fastener holes, and aesthetic demands. Grinding the is best conventional machining process to achieve a better surface finish on a given component. Titanium 3Al-2.5 V or Ti grade 9 alloy is primarily utilized in the biomedical, aerospace, and automotive sectors. But because of its low heat conductivity, high chemical reactivity and rapid work hardening, this alloy is known as a difficult-to-cut material. In grinding, the abrasives have low thermal conductivity and small chip sizes, which in turn more heat to being focused in the cutting zone. This heat harms the surface of the workpiece. Therefore, it's crucial to regulate the quantity of heat that the workpiece receives.In this context, this work examines the surface quality of the Titanium 3Al-2.5 V alloy following surface grinding with an Al2O3 wheel under various grinding settings, including surface roughness (Ra), microhardness and material removal rate (MRR) from the workpiece. Techniques for delivering coolant conventionally (flood coolant), dry and using MQL were used and grinding performance were evaluated. The findings demonstrated that the Ra varied from 0.32 to 0.594 µm and hardness on the machine surface varied from 61.7 to 72 HRC. The MRR varied from 0.09 to 0.42 g/minute for the changes in depth of cut, table feed and coolants. Overall, the MQL has produced a good surface finish, high MRR and moderate hardness on the workpiece.

Thermal relations in sled dogs before and after exercise.

Regulation of internal body temperature (Tb), or thermoregulation, is an evolutionarily conserved trait that places demand on basal metabolic rate of endothermic animals. Across species, athletes generate increased quantities of heat in comparison to their nonathletic counterparts and, therefore, must mediate physiological unbalance by upregulating the effectiveness of their heat dissipation abilities. Canine athletes are no exception to this phenomenon, however, with literature denoting body temperatures lower than nonathletic canines, it is clear they must possess adaptations to mitigate this demand. With VO2 max measurements of more than 200 mL/kg/min in sled dogs with mild training to 300 mL/kg/min in highly trained animals, sled dogs are a prime example of athleticism in canines. Seeking to determine correlations between Tear and body mass, morphology, and age of canine athletes, core body temperature (Tb) was measured with an instant ear thermometer, using Tear as a correlate before and after a 2-mile run. In addition, we employed thermal imaging analysis to capture body-wide heat dissipation patterns in sled dogs, and focused on thermal variation of mouth (Tmouth), nose (Tnose), and eyes (Teye). Furthermore, we looked at correlations between thermal variability across these four tissues and head morphology of each dog. Tear was consistently the highest temperature across all tissues measured, with a 1.5°C increase between pre- to postexercise (p < 0.001). Thermal imaging revealed significant positive correlations between Tmouth and body mass 15 min postexercise (p = 0.0023) as well as significantly negative correlations between Tnose and body mass at before exercise (p = 0.0468), Teye and nose length after run (p = 0.0076), and Tmouth and nose length after run (p = 0.0110). As body temperature rises during exercise, it becomes increasingly important to regulate blood flow throughout the body to supply working tissues with oxygen. This demand is offset by the role of the snout in evaporative cooling through panting, functioning as a prime location for heat dissipation and therefore maintaining significant relationships with many other vascularized tissues.

Peridynamic analysis of thermal behaviour of PCM composites for heat storage

One possibility to utilize excess energy from electricity generation or other industrial processes is to use thermal energy storage systems based on phase change materials (PCM). These systems can accumulate and release significant amounts of heat energy during the phase transitions. The volume and properties of PCM undergo rapid changes during the transitions, creating strong physical non-linearities and geometric discontinuities. Describing this complexity with local formulations of the physical processes, i.e., formulations with differential equations, makes the numerical solutions of the corresponding problems challenging. This paper presents a numerical approach for the analysis of such physically complicated systems based on Peridynamics. The approach is illustrated by modelling and analysing the thermal behaviour of a PCM. The computational challenges associated with simulating composite structures with large differences in the heat conductivity of their components are addressed by investigating the influence of different types of peridynamic kernels and their numerical implementation. The results demonstrate that the solution is significantly influenced by the definition of the average thermal conductivity of the peridynamic bonds. The proposed modelling framework provides the base for developing a precise thermo-hydro-mechanical description of PCM composites that can fully represent the complex physical behaviour of thermal energy storage systems.

Improving the novel white coconut oil-based metalworking fluid using nano particles for minimum surface roughness and tool tip temperature

At present, nearly 85 % all of the requirement for MWFs are satisfied by the use of mixtures of petroleum by-products and synthetic substances with supplementary additives to enhance their properties. The demand for easily biodegradable, environmental friendly MWFs is a current requirement. COCOTP, a novel biodegradable MWF based on white (refined) coconut oil, developed by authors, had previously shown promising tribological properties for machining mild steel (MS) and stainless steel (SS) when used with the flooding method, but had fallen short of the performance of commercially available, non-biodegradable alternatives with MQL. Therefore in the current investigation, nano-particles were added to improve the performance of novel COCOTP MWF to use it with MQL conditions. Two nanomaterials nano-graphite and nano-Al2O3 were separately added to the base fluid in different concentrations as a monodispersed suspension. These nano enhanced fluids (NEFs) were subsequently used in straight turning experiments of two work materials AISI304 and SS400. Both the nano-enhanced fluids show convincing improvements over both COCOTP and mineral-oil based fluids in terms of surface roughness of the specimens regardless of the material being turned. However when machining SS 400, NEFs perform better only in lower speeds in terms of temperature. SS400 has a much higher thermal conductivity than AISI304 means that the quantity of residual heat remaining at the point of material removal which can be absorbed by the cutting fluid is lower in SS400. During machining SS400 under MQL lubrication 9.8 %, 26.8 % and 24 % reduction of surface roughness values (with respect to soluble oil) and during machining AISI304 55.3 %, 73.7 % and 70.4 % reduction of surface roughness values were obtained at 1175 rpm with COCOTP, NEF A and NEF G respectively. Based on the experimental results, the best-performing nano-enhanced fluids under MQL are 0.3 % (w/w) Al2O3 and 0.3 % (w/w) graphite.

Analysis of the Efficiency of Landfill Gas Treatment for Power Generation in a Cogeneration System in Terms of the European Green Deal

Climate change and environmental degradation pose a threat to Europe and the world. The mechanism that will address these challenges is the European Green Deal, which envisions transforming the EU into a modern, resourceful, economical and competitive economy, aiming for zero greenhouse gas emissions. Landfill gas generated in a landfill waste deposit poses a threat to the environment and people. In this aspect, its capture, treatment and safe neutralization or use for energy purposes are important. Treatment of landfill gas, which is the fuel for gas engines in cogeneration units, is crucial for their proper operation and the quantity and quality of electricity and heat generated. The purpose of this study was to perform research to determine the hydrogen sulfide content of landfill gas and the actual efficiency of hydrogen sulfide removal from the gas using activated carbon. The tests performed constitute the basis for the reliable operation of gas engines in cogeneration installations and are dedicated mainly to the operators of these installations. Accordingly, three measurement campaigns were carried out, each with 42 measurements, the first for the “raw” gas obtained directly from the landfill, the second for the gas before entering the carbon filter and the third after its treatment. In addition, surface analysis was performed, and the elemental composition of the “fresh” molded activated carbon constituting the filter material was determined using a scanning electron microscope with an EDS system. The results showed a high elemental content of carbon in the test sample at 92.78%, while the efficiency of hydrogen sulfide removal from landfill gas by activated carbon, calculated from the measurements, was 97.05%. The obtained test results confirmed the validity of using impregnated activated carbon to remove hydrogen sulfide from landfill gas and its high adsorption efficiency, which can consequently result in reliable operation of the gas engine in the cogeneration unit and ultimately fit in with the objectives of the European Green Deal. The research results are an incentive for operators of cogeneration installations to systematically examine the quality of landfill gas and the efficiency of biogas purification devices.

Performance analysis of ocean thermal energy conversion system integrated with waste heat recovery from offshore oil and gas platform

To improve ocean thermal energy conversion (OTEC) system efficiency, four systems utilizing the waste heat recovery from offshore oil and gas platform are proposed, including flue gas boosting OTEC (system I), production water boosting surface seawater OTEC (system II), production water boosting working medium OTEC (system III), and production water boosting vapor OTEC (system IV). The system thermodynamic performance are investigated. The results show that system IV has larger power generation (Wnet), thermal efficiency (ηth) and exergy efficiency (ηex) than others. Compared with single OTEC system, for system IV, Wnet, ηth and ηex are increased by 1569.13 %, 70.35 % and 138.26 %, respectively. For system IV, with the increase of flue gas waste heat quantity from 2000 to 4000 kW, Wnet, ηth and ηex are increased by 562 %, 390 % and 181 % respectively; with the increase of production water waste heat quantity from 0 to 100 kW, Wnet, ηth and ηex are 12.59 %, 5.73 % and 2.86 % respectively. Wnet rises first and then decreases with the increase of evaporation pressure (Peva) or base fluid concentration (xb), presenting an optimal Peva of 1.5 MPa and xb of 0.82 corresponding to the maximum Wnet; Wnet decreases with the increase of condensation temperature.

Development of multi-module arranged in series using U-type longitudinal fin tube in thermal energy storage system

The performance of a thermal energy storage (TES) system for commercial applications can be improved using phase change materials (PCM). This study develops a vertical multi-module from a PCM for a TES system that achieves the same effect as a single-module by arranging multiple-modules in series as a U-type longitudinal fin tube to enhance the system's performance. The U-type longitudinal fin tube is designed to enhance heat transfer within the module, and a single-module is designed for multi-module applications. The TES system is analyzed to the average heat transfer rate, overall heat transfer coefficient, quantity of heat storage/release, and utilization ratio at different heat transfer fluid (HTF) flow rates, inlet and outlet temperatures and different number of modules. Consequently, the addition of several modules improves the thermal performance, and an increase in the HTF flow rate improves the average heat transfer rate. The overall heat transfer coefficient is used to analyze the thermal characteristics of the PCM. During the heat charging and discharging processes, the average heat transfer rates are 2.4 and 2.55 kW, respectively, and the quantities of heat storage and release are 5,153.59 and 4,771.79 kJ, respectively, for three modules. The overall heat transfer coefficient of the PCM exhibits similar results with an increasing HTF flow rate; it increases marginally from 42.25 to 45.8 and 9.9–10.8 W∙m−2∙K−1 as more modules are added. Further, the results of this study confirm that the relatively low HTF flow rates in the multi-module require the addition of several modules and that increasing the HTF flow rates limits the number of modules.

Environmental impacts of structural lumber production in Japan

Low-rise buildings in Japan are predominantly made of wood. Furthermore, the government promotes the use of wood in mid- and high-rise buildings to tackle climate change. Therefore, the environmental impact of structural lumber should be assessed. In this study, we evaluated greenhouse gas (GHG) emissions and resource consumption associated with structural lumber production using life cycle assessment. Herein, we focused on Japanese Agricultural Standard certified structural lumber (artificially dried lumber and machine-grade structural lumber) made from Japanese roundwood. To ensure representativeness, 15 companies and 15 sawmills covering more than 50% of Japan's structural lumber production were selected and data on their production were collected. The results show that the GHG emissions and resource consumption of Japanese structural lumber are 7.99 × 10 kg-CO2e/m3 and 1.77 × 10–3 kg-Sb eq./m3, respectively. The major sources of GHG emissions are electricity and roundwood production. Roundwood and metal tools significantly affect resource consumption. The recycling of rare metals in tools is essential for reducing resource consumption. A significant amount of heat energy is utilized for drying, and this heat energy is supplied from both biomass and fossil fuels. GHG emissions and resource consumption are 5.3 and 1.6 times higher, respectively, if biomass fuel is replaced by fossil fuel. Policies supporting the introduction of biomass boilers have been highly effective. It is recommended to further promote measures such as replacing fossil fuel-based boilers with biomass boilers and effectively utilizing biomass boilers in multiple regional sawmills. In addition, switching from grid electricity to electricity generated by renewable energy sources is effective for further reducing environmental impacts. The long-term use of structural lumber is valid for combating global warming because it fixes carbon for decades. In this study, the CO2 emissions from biomasaluated in terms of carbon neutrality. Appropriate forest management is a prerequisite for carbon neutrality, and the promotion of sustainable forest management, such as reforestation after logging, is crucial.

Impact of Convection and Rotation on Advanced Thermal Energy Storage Using Nanoencapsulated Phase Change Materials in Wavy Enclosures

Free convection heat transfer in hybrid nanofluids in a differentially heated wavy enclosure is studied. The wavy enclosure moves at a constant counterclockwise rotational speed along its longitudinal axis. The enclosure is filled with a hybrid nanofluids consisting of water (H2O) and nanoencapsulated phase change materials (NEPCMs). These NEPCMs consist of a polyurethane coating and a core of N‐nonadecane, which undergoes a phase transition and has the capacity to retain or emit a significant quantity of latent heat. The dimensionless forms of the governing equations have been solved using finite element method. The validity of the present code is demonstrated by comparing its predictions with published results. The governing parameters under consideration are the corrugated number, 0 ≤ N ≤ 3, the volume fraction of hybrid nanoparticles, 0.0 ≤ ϕ ≤ 0.05, the Taylor number, 8 × 102 ≤ TaH2O ≤ 2 × 104. Changing the rotation speed is found to alter the melting and solidification zones in terms of pathways and size zones. The melting zone has a large size at moderate wave number, and its size shrinks and shifts downward as the wave number increases. An increase in the heat transfer rate values up to 38% is obtained when the concentration is adjusted from 1% to 5% for N = 1.

Estimating temperature distribution and heat quantity of spindle shaft for machining centers

Estimating temperature distribution and heat quantity of spindle shaft for machining centers

CFD Analysis for the Variation of Velocity inside Different Types of Ribs

Abstract: Heat exchanger is used to accomplish the industrial demand. Heat Exchanger are necessary for nuclear reactors and in chemical engineering, for of large quantity of heat is conveying in a slight space with high heat transmission rates and slight habitation time distributions even it suffers through a disadvantage of larger pressure drop. From my analysis, it is found that the uses of ribs inside the solar heat exchanger increase the heat transfer with increase in Reynolds number. Through analysis, it is also found that the value of heat transfer coefficient increases with increase in Reynolds number, heat transfer coefficient is maximum for rectangular shape rib in both the cases that are during using water and nano fluid as a working fluid. The average heat transfer coefficient ratio graph shows that rib used in the solar heat exchanger with nano fluid flow shows more heat transfer enhancement as compared to a solar heat exchanger with simple water flow. Overall it is found that rectangular shape ribs show more heat transfer coefficient as compared to other rib.

(Invited) Benchmarking and Predicting the Risks of Commercial Li-Ion Cells Undergoing Thermal Runaway

The performance of commercial Li-ion batteries increases year after year. New mechanical designs of cells as well as changing electrolyte and active material compositions continually push performance boundaries forward. With such changes, the risks associated with thermal runaway of cells change too and a challenge persists in recording and benchmarking risks to determine whether increased performance comes at the expense of increased risk in the event of thermal runaway. The Battery Failure Databank provides a record of thermal and mass ejection behaviors of past and present commercial cells and provides a valuable resource for benchmarking behaviors and determining the predictability of risks associated with thermal runaway.A Fractional Thermal Runaway Calorimeter (FTRC), developed by the NASA Johnson Space Center in collaboration with the National Renewable Energy Laboratory (NREL), distinctly measures heat emitted from the body of commercial cells and heat that is ejected from the cell. The FTRC also facilitates in-situ high-speed radiography to link phenomena occurring inside the cell with external thermal measurements. The FTRC was used for all tests recorded in the Battery Failure Databank and high-speed radiographs accompany each thermal dataset. Having thermal, mass ejection, and internal dynamics behaviors from hundreds commercial cells under mechanical and thermal abuse conditions facilitates statistical analyses of cell behaviors and evaluation of the efficacy of machine learning methods for predicting risks associated with thermal runaway.Using data from the Battery Failure Databank, the following three topics will be covered in this talk: Correlations between heat generation and mass ejection: The total heat output from cells showed a strong correlation with the quantity of material ejected. An explanation for this based on distinct heat measurements from ejected and non-ejected materials will be discussed. Potential causes of outlier cells that produce exceptionally high heat: Upon conducting numerous repeat tests for each cell, outlier cells that produce exceptionally high quantities of heat were observed. High-speed radiography data revealed that internal dynamic phenomena can lead to extreme variations in thermal and ejection behavior observed externally. The predictability of thermal runaway outcomes using machine learning methods and limited data: With limited data on thermal behavior, mass ejection, and cell specifications, the accuracy of zero- and one-shot approaches to predicting the variation and distribution of heat output during thermal runaway of a new cell type, based on training data in the Battery Failure Databank, will be discussed. The analyses and open-access resources provided with this work are expected to provide a foundation for benchmarking the behavior and predictability of risks associated with thermal runaway of past and present commercial Li-ion cells. In addition to providing a valuable resource for designing safe battery systems, it is expected that this data will be imperative as we evaluate next generation cell designs and assess their respective failure mechanisms and associated risks.

Quench cooling of steel plates by reciprocating moving water jet impingement

Owing to the short time duration and violent nature of boiling regimes, the steel quench cooling on the Run Out Table is extremely complex, this challenges the prediction of the heat transfer coefficient. In this study, we first established a novel reciprocally moving nozzles platform to experimentally investigate the moving quenching process. Then the two-dimensional transient heat flux, wetting behaviors, and heat transfer mechanism that was influenced by the surface temperature, and moving speed were explored. These results revealed the heat flux reduced with the moving speed but elevated with the surface temperature. The wetted area also expanded linearly with the decrease in temperature. With the aid of the developed two-dimensional transient heat flux, the heat quantity was revealed to decrease with the surface temperature at different speeds, but the decline proportion was much lower than that of MHF (maximum heat flux). Notably, the transient heat flux and heat transfer capacity in two-dimensional favored predicting the temperature field of the steel quenching process under industrial conditions. The findings in this work provided the envision to understand the heat transfer mechanism in the moving quenching cooling and provided a flexible method to investigate cooling in a moving state.

Experimental and simulation study of a U-shaped water-cooled sleeve heat pipe radiator for high heat flux density

Effective heat dissipation methods are desperately needed to ensure heat transfer of the large quantity of heat generated by radioactive isotopes in restricted places. This study employs the Bell-Delaware method to design a U-shaped water-cooled sleeve heat pipe radiator (UWC-HP) intended for heat dissipation on a 16 cm2 surface area with a heat flux density of 200 W/cm2. We have established a 3D model, which was experimentally validated, showing an error within 5 %. Subsequently, as the refrigerant and structural design of the condenser segment are crucial factors leading to the limitations of UWC-HP, this study aims to evaluate the impact of the condenser segment on the heat dissipation performance. Specifically, we investigated the effects of different cooling water temperatures, flow rates, and fin designs on the heat dissipation performance of the UWC-HP. Based on this, We found that the rib height, the number of ribs, and the rib material can strengthen the performance of the heat sink by a maximum of 12.3 %, 10.1 %, and 3.7 %, respectively. The heat sink optimized by orthogonal experiments has a maximum heat source surface temperature of 506.22 K and Nu of 101.85, which reduces the maximum surface temperature of the heat source by a maximum of 22 K and strengthens the heat sink capacity of heat pipes by 20 %. This article achieves efficient heat transfer for isotopic decay heat in a confined space by designing a heat pipe heat exchanger. It reduces the equipment's temperature and enhances the safety of the nuclear reactor.

Hydrothermal and entropy generation analyses of natural convection of nano-encapsulated phase change materials suspension in a cavity subjected to the localized heating

Being heated electronic components significantly reduces their efficiency, and thus requiring high-efficient cooling strategies to keep such devices operating at an optimal temperature level. The present study is devoted to investigating the cooling performance of water-based nano-encapsulated phase change materials (NePCMs) suspension in the presence of a heat source with uniform temperature. The nano-sized PCM capsules are constructed by n-nonadecane as the core and polyurethane for the protective shell. The n-nonadecane is capable of absorbing/releasing a significant quantity of latent heat in the process of its phase transition, which is actually beneficial for improving the heat transfer performance. The home developed FORTRAN program based on the finite volume method (FVM) combined with the artificial compressibility algorithm is employed to solve the nonlinear coupled equations for fluid flow and heat transfer. The influences of the Rayleigh number (103≤Ra≤105), the Stefan number (0.1≤Ste≤0.9), the volume fraction of the nano-capsules (0≤ϕ≤0.04), and the heating position (0.25≤a≤0.75) on the hydrothermal behavior and entropy generation are explored. The findings reveal that there exists a capsule loading interval wherein the heat transfer enhancement can be achieved, but beyond that range, the deterioration of cooling performance may occur. Moreover, the contribution of suspending NePCMs to the heat transfer improvement is greatly more noticeable at low Rayleigh number, and particularly for the arrangement of upper heating. The average Nusselt number decreases with the increment of the Stefan number, and the variation approximately follows an exponential change for all considered Rayleigh numbers and heating positions. Concerning the entropy generation, it is essentially contributed by the heat transfer irreversibility, and the region with high irreversibility is always located around the intersection of the heated surface and the insulated vertical wall. This research can provide theoretical guidance for cooling the electronic components by utilizing the NePCMs suspension.