Search results
1 – 10 of 208Pratheek Suresh and Balaji Chakravarthy
As data centres grow in size and complexity, traditional air-cooling methods are becoming less effective and more expensive. Immersion cooling, where servers are submerged in a…
Abstract
Purpose
As data centres grow in size and complexity, traditional air-cooling methods are becoming less effective and more expensive. Immersion cooling, where servers are submerged in a dielectric fluid, has emerged as a promising alternative. Ensuring reliable operations in data centre applications requires the development of an effective control framework for immersion cooling systems, which necessitates the prediction of server temperature. While deep learning-based temperature prediction models have shown effectiveness, further enhancement is needed to improve their prediction accuracy. This study aims to develop a temperature prediction model using Long Short-Term Memory (LSTM) Networks based on recursive encoder-decoder architecture.
Design/methodology/approach
This paper explores the use of deep learning algorithms to predict the temperature of a heater in a two-phase immersion-cooled system using NOVEC 7100. The performance of recursive-long short-term memory-encoder-decoder (R-LSTM-ED), recursive-convolutional neural network-LSTM (R-CNN-LSTM) and R-LSTM approaches are compared using mean absolute error, root mean square error, mean absolute percentage error and coefficient of determination (R2) as performance metrics. The impact of window size, sampling period and noise within training data on the performance of the model is investigated.
Findings
The R-LSTM-ED consistently outperforms the R-LSTM model by 6%, 15.8% and 12.5%, and R-CNN-LSTM model by 4%, 11% and 12.3% in all forecast ranges of 10, 30 and 60 s, respectively, averaged across all the workloads considered in the study. The optimum sampling period based on the study is found to be 2 s and the window size to be 60 s. The performance of the model deteriorates significantly as the noise level reaches 10%.
Research limitations/implications
The proposed models are currently trained on data collected from an experimental setup simulating data centre loads. Future research should seek to extend the applicability of the models by incorporating time series data from immersion-cooled servers.
Originality/value
The proposed multivariate-recursive-prediction models are trained and tested by using real Data Centre workload traces applied to the immersion-cooled system developed in the laboratory.
Details
Keywords
Songhua Li, Shanhang Huang, Chao Wei, Jian Sun, Yonghua Wang and Kun Wang
This study aims to understand the influence of raceway surface topography on the temperature rise characteristics of silicon nitride (Si3N4) full ceramic ball bearing and improve…
Abstract
Purpose
This study aims to understand the influence of raceway surface topography on the temperature rise characteristics of silicon nitride (Si3N4) full ceramic ball bearing and improve its service life.
Design/methodology/approach
The arithmetic average height Sa, skewness Ssk and kurtosis Sku in the three-dimensional surface roughness parameters are used to quantitatively characterize the surface topography of the raceway after superfinishing. The bearing life testing machine is used to test the Si3N4 full ceramic ball bearing using polytetrafluoroethylene (PTFE) cage under dry friction conditions, and the self-lubricating full ceramic ball bearing heat generation model is established.
Findings
With the decrease of Sa and Ssk on the raceway surface and the increase of Sku, the average height of the raceway surface decreases, and the peaks and valleys tend to be symmetrically distributed on the average surface, and the surface texture becomes tighter. This kind of raceway surface topography is beneficial to form a thin and uniform filamentous PTFE transfer film with a wide coverage area on the raceway surface based on consuming less cage materials and improving the temperature rise characteristics of hot isostatic pressing silicon nitride full ceramic ball bearings.
Originality/value
The research results provide a theoretical basis for the reasonable selection of Si3N4 ring raceway processing technology and have important significance for improving the working characteristics and service life of Si3N4 full ceramic ball bearings under dry friction conditions.
Details
Keywords
Adrian Pietruszka, Paweł Górecki and Agata Skwarek
This paper aims to investigate the influence of composite solder joint preparation on the thermal properties of metal-oxide-semiconductor field-effect transistors (MOSFETs) and…
Abstract
Purpose
This paper aims to investigate the influence of composite solder joint preparation on the thermal properties of metal-oxide-semiconductor field-effect transistors (MOSFETs) and the mechanical strength of the soldered joint.
Design/methodology/approach
Reinforced composite solder joints with the addition of titanium oxide nanopowder (TiO2) were prepared. The reference alloy was Sn99Ag0.3Cu0.7. Reinforced joints differed in the weight percentage of TiO2, ranging from 0.125 to 1.0 Wt.%. Two types of components were used for the tests. The resistor in the 0805 package was used for mechanical strength tests, where the component was soldered to the FR4 substrate. For thermal parameters measurements, a power element MOSFET in a TO-263 package was used, which was soldered to a metal core printed circuit board (PCB) substrate. Components were soldered in batch IR oven.
Findings
Shear tests showed that the addition of titanium oxide does not significantly increase the resistance of the solder joint to mechanical damage. Titanium oxide addition was shown to not considerably influence the soldered joint’s mechanical strength compared to reference samples when soldered in batch ovens. Thermal resistance Rthj-a of MOSFETs depends on TiO2 concentration in the composite solder joint reaching the minimum Rthj at 0.25 Wt.% of TiO2.
Research limitations/implications
Mechanical strength: TiO2 reinforcement shows minimal impact on mechanical strength, suggesting altered liquidus temperature and microstructure, requiring further investigation. Thermal performance: thermal parameters vary with TiO2 concentration, with optimal performance at 0.25 Wt.%. Experimental validation is crucial for practical application. Experimental confirmation: validation of optimal concentrations is essential for accurate assessment and real-world application. Soldering method influence: batch oven soldering may affect mechanical strength, necessitating exploration of alternative methods. Thermal vs mechanical enhancement: while TiO2 does not notably enhance mechanical strength, it improves thermal properties, highlighting the need for balanced design in power semiconductor assembly.
Practical implications
Incorporating TiO2 enhances thermal properties in power semiconductor assembly. Optimal concentration balancing thermal performance and mechanical strength must be determined experimentally. Batch oven soldering may influence mechanical strength, requiring evaluation of alternative techniques. TiO2 composite solder joints offer promise in power electronics for efficient heat dissipation. Microstructural analysis can optimize solder joint design and performance. Rigorous quality control during soldering ensures consistent thermal performance and mitigates negative effects on mechanical strength.
Social implications
The integration of TiO2 reinforcement in solder joints impacts thermal properties crucial for power semiconductor assembly. However, its influence on mechanical strength is limited, potentially affecting product reliability. Understanding these effects necessitates collaborative efforts between researchers and industry stakeholders to develop robust soldering techniques. Ensuring optimal TiO2 concentration through experimental validation is essential to maintain product integrity and safety standards. Additionally, dissemination of research findings and best practices can empower manufacturers to make informed decisions, fostering innovation and sustainability in electronic manufacturing processes. Ultimately, addressing these social implications promotes technological advancement while prioritizing consumer trust and product quality in the electronics industry.
Originality/value
The research shows the importance of the soldering technology used to assemble MOSFET devices.
Details
Keywords
Shanmugan Subramani and Mutharasu Devarajan
Polymer-based thermal interface materials (TIMs) are having pump out problem and could be resolved for reliable application. Solid-based interface materials have been suggested…
Abstract
Purpose
Polymer-based thermal interface materials (TIMs) are having pump out problem and could be resolved for reliable application. Solid-based interface materials have been suggested and reported. The purpose of this paper is suggesting thin film-based TIM to sustain the light-emiting diode (LED) performance and electronic device miniaturization.
Design/methodology/approach
Consequently, ZnO thin film at various thicknesses was prepared by chemical vapour deposition (CVD) method and tested their thermal behaviour using thermal transient analysis as solid TIM for high-power LED.
Findings
Low value in total thermal resistance (Rth-tot) was observed for ZnO thin film boundary condition than bare Al boundary condition. The measured interface (ZnO thin film) resistance {(Rth-bhs) thermal resistance of the interface layer (thin film) placed between metal core printed circuit board (MCPCB) board and Al substrates} was nearly equal to Ag paste boundary condition and showed low values for ZnO film prepared at 30 min process time measured at 700 mA. The TJ value of LED mounted on ZnO thin film (prepared at 30 min.) coated Al substrates was measured to be 74.8°C. High value in junction temperature difference (ΔTJ) of about 4.7°C was noticed with 30 min processed ZnO thin film when compared with Al boundary condition. Low correlated colour temperature and high luminous flux values of tested LED were also observed with ZnO thin film boundary condition (processed at 30 min) compared with both Al substrate and Ag paste boundary condition.
Originality/value
Overall, 30 min CVD processed ZnO thin film would be an alternative for commercial TIM to achieve efficient thermal management. This will increase the life span of the LED as the proposed material decreases the TJ values.
Details
Keywords
Zhicai Yu, Lili Wang, Yiwei Shao, Yun Liu, Yuhang Zhao, Yi Qin, Yingzi Zhang and Hualing He
This study aims to fabricate a novel electromagnetic interference (EMI) shielding composite aerogel with both thermal insulation and high temperature warning functions.
Abstract
Purpose
This study aims to fabricate a novel electromagnetic interference (EMI) shielding composite aerogel with both thermal insulation and high temperature warning functions.
Design/methodology/approach
An emerging bio-based polypyrrole (PPy) gel/Fe3O4/calcium alginate (PFC) EMI shielding composite aerogel was prepared by freeze-drying and in situ polymerization method. First, Fe3O4/calcium alginate (CA) aerogel was obtained by freeze-drying the Fe3O4/CA mixture. Then, PPy/Fe3O4/CA was obtained by synthesizing PPy on the surface of CA/Fe3O4 aerogel through in situ polymerization. Finally, PPy/Fe3O4/CA was immersed in porphyrin solution (cross-linking agent) to get the final PFC EMI shielding composite aerogel.
Findings
Due to the matched impedance between Fe3O4 and PPy, the EMI shielding performance of PFC composite aerogel can reach up to −8 dB. In addition, the PFC EMI shielding composite aerogel also shows excellent self-extinguishing and thermal insulation properties. After leaving the flame, the burning PFC aerogel is quickly extinguished. When the PFC aerogel is placed on the heating plate at 230 °C, the temperature on the side of the aerogel away from the heating plate is only 90.3 °C after 5 min of heating. The electrical resistance of the PFC composite aerogel can be reduced from 3.62 × 104 O to 5 × 102 O to trigger the warning light after 3 s of exposure to the alcohol lamp flame. This reversible thermal resistance response characteristic can be used to give an early warning signal when the PFC encounters high temperature or flame.
Originality/value
This work provides a novel strategy for designing a multifunctional EMI shielding composite aerogel with repeatable high temperature warning performance. This PFC composite aerogel shows potential applications in the prevention of material combustion in high temperature electromagnetic environments.
Details
Keywords
Amanda de Oliveira e Silva, Alice Leonel, Maisa Tonon Bitti Perazzini and Hugo Perazzini
Brewer's spent grain (BSG) is the main by-product of the brewing industry, holding significant potential for biomass applications. The purpose of this paper was to determine the…
Abstract
Purpose
Brewer's spent grain (BSG) is the main by-product of the brewing industry, holding significant potential for biomass applications. The purpose of this paper was to determine the effective thermal conductivity (keff) of BSG and to develop an Artificial Neural Network (ANN) to predict keff, since this property is fundamental in the design and optimization of the thermochemical conversion processes toward the feasibility of bioenergy production.
Design/methodology/approach
The experimental determination of keff as a function of BSG particle diameter and heating rate was performed using the line heat source method. The resulting values were used as a database for training the ANN and testing five multiple linear regression models to predict keff under different conditions.
Findings
Experimental values of keff were in the range of 0.090–0.127 W m−1 K−1, typical for biomasses. The results showed that the reduction of the BSG particle diameter increases keff, and that the increase in the heating rate does not statistically affect this property. The developed neural model presented superior performance to the multiple linear regression models, accurately predicting the experimental values and new patterns not addressed in the training procedure.
Originality/value
The empirical correlations and the developed ANN can be utilized in future work. This research conducted a discussion on the practical implications of the results for biomass valorization. This subject is very scarce in the literature, and no studies related to keff of BSG were found.
Details
Keywords
Lijun Chen, Wanting Zhao and Zheqing Gong
The traditional vinyl ester of neodecanoic acid-vinyl acetate (VeoVa10-VAc) copolymer latex is a linear structure with poor film formation, thus causing solvent resistance and…
Abstract
Purpose
The traditional vinyl ester of neodecanoic acid-vinyl acetate (VeoVa10-VAc) copolymer latex is a linear structure with poor film formation, thus causing solvent resistance and wear resistance of the latex film to be poor. This study aims to investigate the use of cross-linkers in emulsion polymerization to modify the latex. During the course of film formation, the reactive functional groups react to form cross-linkage. The network structure can effectively improve the compactness of the resin, thereby greatly improving the water resistance, solvent resistance and heat resistance of the resultant film. In addition, the reactive emulsifier is used to replace the conventional emulsifier. Thus, the drawbacks of the conventional emulsifier molecules migrate and desorb can be avoided when the polymer latex is stored.
Design/methodology/approach
The cross-linked VAc-VeoVa10 latex has been synthesized with the reactive surfactants, in which VAc and VeoVa10 are used as the main monomers and ethylene glycol dimethacrylate (EGDMA) was used as the cross-linked monomer. Potassium persulfate (KPS) and mixed surfactants of alkyl allyl polyoxyethylene ether ammonium sulfate (JS-20) and allyl nonyl phenol polyoxyethylene ether (ANPEO-10) were used as the initiator and emulsifier, respectively. The structure of resultant latex film was characterized by Fourier transform infrared spectroscopy. The latex films were tested by thermogravimetric analysis, differential scanning calorimetry and contact angle (CA). The particle size and its distribution of the latex were measured by the nano particle size analyzer.
Findings
The factors that had an influence on the properties of the latex and the film were investigated in detail. The stability of the resultant latex is good. The average particles of the latex and its distribution are small and uniform, respectively. In comparison with the conventional latex film, the thermal stability and hydrophobicity of the resultant latex film are improved obviously.
Practical implications
The resultant latex can be used in both the waterborne interior and exterior wall coatings, pickering stabilized waterborne polymer dispersions, polymer powders, environmentally friendly polymer-modified waterproof mortar and other fields, which can be satisfied with the high demand of thermal stability and hydrophobicity.
Originality/value
The modification of poly (VAc-VeoVa10) by reactive emulsifier and cross-linker is seldom reported. In this study, the cross-linked poly (VAC-VeoVa) latex is prepared through the reactive surfactants, with VAc and VeoVa10 used as the main monomers and EGDMA used as the cross-linked monomer. KPS and mixed surfactants of JS-20 and ANPEO-10 are used as the initiator and emulsifier, respectively.
Details
Keywords
Samridhi Garg, Monica Puri Sikka and Vinay Kumar Midha
Perspiration and heat are produced by the body and must be eliminated to maintain a stable body temperature. Sweat, heat and air must pass through the fabric to be comfortable…
Abstract
Purpose
Perspiration and heat are produced by the body and must be eliminated to maintain a stable body temperature. Sweat, heat and air must pass through the fabric to be comfortable. The cloth absorbs sweat and then releases it, allowing the body to chill down. By capillary action, moisture is driven away from fabric pores or sucked out of yarns. Convectional air movement improves sweat drainage, which may aid in body temperature reduction. Clothing reduces the skin's ability to transport heat and moisture to the outside. Excessive moisture makes clothing stick to the skin, whereas excessive heat induces heat stress, making the user uncomfortable. Wet heat loss is significantly more difficult to understand than dry heat loss. The purpose of this study is to provided a good compilation of complete information on wet thermal comfort of textile and technological elements to be consider while constructing protective apparel.
Design/methodology/approach
This paper aims to critically review studies on the thermal comfort of textiles in wet conditions and assess the results to guide future research.
Findings
Several recent studies focused on wet textiles' impact on comfort. Moisture reduces the fabric's thermal insulation value while also altering its moisture characteristics. Moisture and heat conductivity were linked. Sweat and other factors impact fabric comfort. So, while evaluating a fabric's comfort, consider both external and inside moisture.
Originality/value
The systematic literature review in this research focuses on wet thermal comfort and technological elements to consider while constructing protective apparel.
Details
Keywords
This study aims to explore the synthesis, characteristics and utilization of polymer composites integrated with cutting-edge pigments.
Abstract
Purpose
This study aims to explore the synthesis, characteristics and utilization of polymer composites integrated with cutting-edge pigments.
Design/methodology/approach
The incorporation of advanced pigments introduces functionalities such as enhanced mechanical strength, thermal stability, ultraviolet resistance and color stability, thus extending the range of applications in diverse fields including automotive, aerospace, electronics and construction.
Findings
This review discusses the mechanisms underlying the property enhancements achieved through the incorporation of advanced pigments and highlights recent developments in the field.
Originality/value
Polymer composites incorporating advanced pigments have garnered significant attention in recent years because of their potential to enhance various material properties and broaden their applications. This paper explores the fabrication methods of polymer composites reinforced with organic/inorganic advanced pigments in brief along with their characteristics and applications.
Details
Keywords
Ali Hashemi, Parsa Yazdanpanah Qaraei and Mostafa Shabanian-Poodeh
The aim of this paper is to provide a simple yet accurate and efficient geometric method for thermal homogenization of impregnated and non-impregnated coil winding technologies…
Abstract
Purpose
The aim of this paper is to provide a simple yet accurate and efficient geometric method for thermal homogenization of impregnated and non-impregnated coil winding technologies based on the concept of thermal resistance.
Design/methodology/approach
For regular windings, the periodic microscopic cell in the winding space is identified. Also, for irregular windings, the average microscopic cell of the winding is determined. An approximation is used to calculate the thermal resistance of the winding cell. Based on this approximation, the winding insulation is considered as a circular ring around the wire. Mathematical equations are obtained to calculate the equivalent thermal resistance of the cell. The equivalent thermal conductivity of the winding is calculated using equivalent thermal resistance of the cell. Winding thermal homogenization is completed by determining the equivalent thermal properties of the cell.
Findings
The thermal pattern of different windings is simulated and compared with the results of different homogenization methods. The results show that the proposed method is applicable for a wide range of windings in terms of winding scheme, packing factor and winding insulation. Also, the results show that the proposed method is more accurate than other winding homogenization methods in calculating the equivalent thermal conductivity of the winding.
Research limitations/implications
In this paper, the change of electrical resistance of the winding with temperature and thermal contact between the sub-components are ignored. Also, liquid insulators, such as oils, and rectangular wires were not investigated. Research in these topics is considered as future work.
Originality/value
Unlike other homogenization methods, the proposed method can be applied to non-impregnated and irregular windings. Also, compared to other homogenization methods, the proposed method has a simpler formulation that makes it easier to program and implement. All of these indicate the efficiency of the proposed method in the thermal analysis of the winding.
Details