Reduced Thermal Resistance of a Two-Layer Wall Construction

2015 ◽  
Vol 725-726 ◽  
pp. 49-56
Author(s):  
Alexander S. Gorshkov ◽  
Ekaterina Ivanova
Keyword(s):  
Thermal Resistance ◽  
Heat Protection ◽  
Thermally Conductive ◽  
Wall Construction

The topic of the article regards to the development of new SP 50.13330.2012 «Heat protection of buildings» actualized edition of SNIP 23-02-2003. The article focuses on the reduced thermal resistance, which takes into account the influence of thermally conductive inclusions by the coefficient of heattechnical uniformity.

scholarly journals Optimization of the level of thermal insulation of enclosing structures of civil buildings

2018 ◽  
Vol 245 ◽  
pp. 06002 ◽  
Author(s):  
Jurgis Zemitis ◽  
Maxim Terekh
Keyword(s):  
Thermal Resistance ◽  
Thermal Insulation ◽  
Economic Efficiency ◽  
Heat Insulation ◽  
Optimal Level ◽  
Economic Conditions ◽  
Additional Heat ◽  
Heat Protection ◽  
Definition Of ◽  
The Given

In the work, methods of an estimation of economic efficiency of additional heat insulation of building enclosing structures and definition of an optimum thermal resistance are considered, deficiencies of the given techniques are marked. A model is proposed for determining the optimal level of heat protection in the new economic conditions.

Thermal and Mechanical Modeling of Metal Foams for Thermal Interface Application

2016 ◽  
Vol 138 (7) ◽  
Author(s):  
Ninad Trifale ◽  
Eric Nauman ◽  
Kazuaki Yazawa
Keyword(s):  
Thermal Resistance ◽  
Metal Foam ◽  
Electronics Cooling ◽  
Cost Effective ◽  
Metal Foams ◽  
High Porosity ◽  
Pore Density ◽  
Thermal Interface ◽  
Interface Thermal Resistance ◽  
Thermally Conductive

We present a study on the apparent thermal resistance of metal foams as a thermal interface in electronics cooling applications. Metal foams are considered beneficial for several applications due to its significantly large surface area for a given volume. Porous heat sinks made of aluminum foam have been well studied in the past. It is not only cost effective due to the unique production process but also appealing for the theoretical modeling study to determine the performance. Instead of allowing the refrigerant flow through the open cell porous medium, we instead consider the foam as a thermal conductive network for thermal interfaces. The porous structure of metal foams is moderately compliant providing a good contact and a lower thermal resistance. We consider foam filled with stagnant air. The major heat transport is through the metal struts connecting the two interfaces with high thermally conductive paths. We study the effect of both porosity and pore density on the observed thermal resistance. Lower porosity and lower pore density yield smaller bulk thermal resistance but also make the metal foam stiffer. To understand this tradeoff and find the optimum, we developed analytic models to predict intrinsic thermal resistance as well as the contact thermal resistance based on microdeformation at the contact surfaces. The variants of these geometries are also analyzed to achieve an optimum design corresponding to maximum compliance. Experiments are carried out in accordance with ASTM D5470 standard. A thermal resistance between the range 17 and 5 K cm2/W is observed for a 0.125 in. thick foam sample tested over a pressure range of 1–3 MPa. The results verify the calculation based on the model consisting the intrinsic thermal conductivity and the correlation of constriction resistance to the actual area of contact. The area of contact is evaluated analytically as a function of pore size (5–40 PPI), porosity (0.88–0.95), orientation of struts, and the cut plane location of idealized tetrakaidecahedron (TKDH) structure. The model is developed based on assumptions of elastic deformations and TKDH structures which are applicable in the high porosity range of 0.85–0.95. An optimum value of porosity for minimizing the overall interface thermal resistance was determined with the model and experimentally validated.

scholarly journals Thermally conductive cost of the heat-insulating materials

2020 ◽  
Vol 2020 (2) ◽  
pp. 92-98
Author(s):  
Orest Voznyak ◽  
◽  
Yuriy Yurkevych ◽  
Iryna Sukholova ◽  
Oleksandr Dovbush ◽  
...  
Keyword(s):  
Thermal Resistance ◽  
Energy Saving ◽  
Thermal Energy ◽  
Thermal Protection ◽  
Theoretical Research ◽  
Maximum Effect ◽  
Insulating Materials ◽  
Insulating Material ◽  
Thermally Conductive ◽  
The Cost

The article presents the results of theoretical research to achieve the maximum effect in determination of the economically feasible level of buildings thermal protection. It must be optimal both thermally and economically, an indicator of which there are the costs. Graphical and analytical dependences are given. The research results substantiate the maximum effect when different thermal insulating materials are used. The aim is to increase the efficiency of energy saving measures, reduce their cost by optimizing the cost of thermal energy and insulating materials, determining the optimization criteria and justification for choice the optimal insulating material and its thickness, and determining the optimal thermal resistance, identifying ways to improve energy efficiency and substantiation of the calculation method. One of the most common thermal renovation measures, namely insulation of external walls, is considered. An economic assessment has been conducted, which is an important factor in a certain energy-saving proposition. The solution of the problem is presented, which includes two stages. The result of the first stage is the selection of the optimal heat-insulating material. The second stage is a substantiation of economically expedient thickness of the heatinsulating material. The obtained results make it possible to increase the efficiency of energy saving in thermal renovation of buildings taking into account both energy and economic aspects. In this paper the results of mathematical provement of such factor importance as the thermally conductive cost of the heat-insulating material at their thickness optimization are presented. Determining for the establishment of the normative thermal resistance in the future is the ratio of the cost of thermal energy to the thermal conductivity of the insulating material.

Impact of thermal interface material on luminous flux curve of InGaAlP low-power light-emitting diodes

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Muna E. Raypah ◽  
Mutharasu Devarajan ◽  
Shahrom Mahmud
Keyword(s):  
Low Power ◽  
Thermal Resistance ◽  
Thermal Management ◽  
Light Output ◽  
Luminous Flux ◽  
Thermal Interface Material ◽  
Junction Temperature ◽  
Thermal Interface ◽  
Content Type ◽  
Thermally Conductive

Purpose One major problem in the lighting industry is the thermal management of the devices. Handling of thermal resistance from solder point to the ambiance of the light-emitting diode (LED) package is linked to the external thermal management that includes a selection of the cooling mode, design of heatsink/substrate and thermal interface material (TIM). Among the significant factors that increase the light output of the of the LED system are efficient substrate and TIM. In this work, the influence of TIM on the luminous flux performance of commercial indium gallium aluminium phosphide (InGaAlP) low-power (LP) LEDs was investigated. Design/methodology/approach One batch of LEDs was mounted directly onto substrates which were glass-reinforced epoxy (FR4) and aluminium-based metal-core printed circuit boards (MCPCBs) with a dielectric layer of different thermal conductivities. Another batch of LEDs was prepared in a similar way, but a layer of TIM was embedded between the LED package and substrate. The TIMs were thermally conductive epoxy (TCE) and thermally conductive adhesive (TCA). The LED parameters were measured by using the integrated system of thermal transient tester (T3Ster) and thermal-radiometric characterization of LEDs at various input currents. Findings With the employment of TIM, the authors found that the LED’s maximum luminous flux was significantly higher than the value mentioned in the LED datasheet, and that a significant reduction in thermal resistance and junction temperature was revealed. The results showed that for a system with low thermal resistance, the maximum luminous flux appeared to occur at a higher power level. It was found that the maximum luminous flux was 24.10, 28.40 and 36.00 lm for the LEDs mounted on the FR4 and two MCPCBs, respectively. After TCA application on the LEDs, the maximum luminous flux values were 32.70, 36.60 and 37.60 lm for the FR4 and MCPCBs, respectively. Moreover, the findings demonstrated that the performance of the LED mounted on the FR4 substrate was more affected by the employment of the TIM than that of MCPCBs. Research limitations/implications One of the major problems in the lighting industry is the thermal management of the device. In many low-power LED applications, the air gap between the two solder pads is not filled up. Heat flow is restricted by the air gap leading to thermal build-up and higher thermal resistance resulting in lower maximum luminous flux. Among the significant factors that increase the light output of the LED system are efficient substrate and TIM. Practical implications The findings in this work can be used as a method to improve thermal management of LP LEDs by applying thermal interface materials that can offer more efficient and brighter LP LEDs. Using aluminium-based substrates can also offer similar benefits. Social implications Users of LP LEDs can benefit from the findings in this work. Brighter automotive lighting (signalling and backlighting) can be achieved, and better automotive lighting can offer better safety for the people on the street, especially during raining and foggy weather. User can also use a lower LED power rating to achieve similar brightness level with LED with higher power rating. Originality/value Better thermal management of commercial LP LEDs was achieved with the employment of thermal interface materials resulting in lower thermal resistance, lower junction temperature and brighter LEDs.

Research on Improvement of Thermal Insulation and Anti-Radiation Performances of Traditional Wooden Vernacular Dwellings of Tujia Minority in West Hunan

2014 ◽  
Vol 633-634 ◽  
pp. 936-940
Author(s):  
Li Zhe ◽  
Shi Lei
Keyword(s):  
Thermal Resistance ◽  
Thermal Insulation ◽  
Thermal Environment ◽  
Air Cavity ◽  
Before And After ◽  
Practical Engineering ◽  
Wall Construction ◽  
Technological Improvements

On the premise of protecting traditional styles of the dwellings, performances of thermal insulation and anti-radiation performances of traditional wooden dwellings of Tujia Minority in West Hunan and the interior thermal environment were improved through technological improvements in this paper. By improving wall construction technologies, thermal insulation boards and wooden planks were added to exterior walls of these dwellings. Furthermore, a two-layer air cavity formed and thus greatly improved thermal resistance of walls. Meanwhile, feasibility of improvement technologies proposed in this paper was validated by practical engineering tests and data detected before and after tests

Buckling of Magnetically Formed Filler Fiber Columns Under Compression Increases Thermal Resistance of Soft Polymer Composites

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
Matthew Ralphs ◽  
Chandler Scheitlin ◽  
Robert Y. Wang ◽  
Konrad Rykaczewski
Keyword(s):  
Thermal Conductivity ◽  
Thermal Resistance ◽  
Thermal Performance ◽  
Volume Fraction ◽  
Potential Method ◽  
Nickel Particles ◽  
Thermal Management Of Electronics ◽  
Thermally Conductive ◽  
Soft Polymer ◽  
Magnetically Aligned

Thermally conductive soft composites are in high demand, and aligning the fill material is a potential method of enhancing their thermal performance. In particular, magnetic alignment of nickel particles has previously been demonstrated as an easy and effective way to improve directional thermal conductivity of such composites. However, the effect of compression on the thermal performance of these materials has not yet been investigated. This work investigates the thermal performance of magnetically aligned nickel fibers in a soft polymer matrix under compression. The fibers orient themselves in the direction of the applied magnetic field and align into columns, resulting in a 3× increase in directional thermal conductivity over unaligned composites at a volume fraction of 0.15. Nevertheless, these aligned fiber columns buckle under strain resulting in an increase in the composite thermal resistance. These results highlight potential pitfalls of magnetic filler alignment when designing soft composites for applications where strain is expected such as thermal management of electronics.

scholarly journals Significant Reduction of Interfacial Thermal Resistance and Phonon Scattering in Graphene/Polyimide Thermally Conductive Composite Films for Thermal Management

Research ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-13 ◽  
Author(s):  
Kunpeng Ruan ◽  
Yongqiang Guo ◽  
Chuyao Lu ◽  
Xuetao Shi ◽  
Tengbo Ma ◽  
...  
Keyword(s):  
Thermal Resistance ◽  
Thermal Management ◽  
Polymer Composite ◽  
Thermal Conduction ◽  
Phonon Scattering ◽  
Composite Films ◽  
Conductive Polymer ◽  
Interfacial Thermal Resistance ◽  
Conductive Composite ◽  
Thermally Conductive

The developing flexible electronic equipment are greatly affected by the rapid accumulation of heat, which is urgent to be solved by thermally conductive polymer composite films. However, the interfacial thermal resistance (ITR) and the phonon scattering at the interfaces are the main bottlenecks limiting the rapid and efficient improvement of thermal conductivity coefficients (λ) of the polymer composite films. Moreover, few researches were focused on characterizing ITR and phonon scattering in thermally conductive polymer composite films. In this paper, graphene oxide (GO) was aminated (NH2-GO) and reduced (NH2-rGO), then NH2-rGO/polyimide (NH2-rGO/PI) thermally conductive composite films were fabricated. Raman spectroscopy was utilized to innovatively characterize phonon scattering and ITR at the interfaces in NH2-rGO/PI thermally conductive composite films, revealing the interfacial thermal conduction mechanism, proving that the amination optimized the interfaces between NH2-rGO and PI, reduced phonon scattering and ITR, and ultimately improved the interfacial thermal conduction. The in-plane λ (λ∥) and through-plane λ (λ⊥) of 15 wt% NH2-rGO/PI thermally conductive composite films at room temperature were, respectively, 7.13 W/mK and 0.74 W/mK, 8.2 times λ∥ (0.87 W/mK) and 3.5 times λ⊥ (0.21 W/mK) of pure PI film, also significantly higher than λ∥ (5.50 W/mK) and λ⊥ (0.62 W/mK) of 15 wt% rGO/PI thermally conductive composite films. Calculation based on the effective medium theory model proved that ITR was reduced via the amination of rGO. Infrared thermal imaging and finite element simulation showed that NH2-rGO/PI thermally conductive composite films obtained excellent heat dissipation and efficient thermal management capabilities on the light-emitting diodes bulbs, 5G high-power chips, and other electronic equipment, which are easy to generate heat severely.

Synthesis and characterization of high-temperature resistant and thermally conductive magnetic PBI/Fe3O4 nanofibers

2020 ◽  
Vol 32 (9) ◽  
pp. 1031-1042
Author(s):  
İlkay Özaytekin ◽  
Kamil Oflaz
Keyword(s):  
Thermal Conductivity ◽  
Thermal Resistance ◽  
Magnetite Nanoparticles ◽  
Polyvinylidene Fluoride ◽  
Magnetic Particles ◽  
Operating Voltage ◽  
Force Microscopy ◽  
Nanocomposite Fiber ◽  
Thermally Conductive ◽  
Vibration Sample Magnetometry

In the present study, magnetite nanoparticles were added to an electrospinning solution of polyvinylidene fluoride (PVDF)/polybenzimidazole (PBI) polymers to prepare PBI/Fe3O4 nanofibers (NFs). The operating voltage of the electrospinning device was set to 15 kV, the distance between the needle and the plate was 10 cm, and the feed rate was set to 0.3 mL h−1. The microstructures of the as-prepared NFs were investigated by Fourier transform infrared spectrophotometry, atomic force microscopy, thermogravimetric analysis, and vibration sample magnetometry. Magnetite-doped PVDF/PBI NFs exhibited superior magnetism and saturation magnetization in the range of 1.5–5 emu g−1. It was observed that the thermal resistance of the fibers increased with the increasing amount of magnetic particles and nanocomposite fiber (NCF) 1 and NCF2 exhibited excellent thermal resistance up to 415°C and 450°C, respectively. The heat conduction coefficient of the fibers was measured at 4, 6, and 8 W. The thermal conductivity of the NFs increased with the increasing amount of magnetite nanoparticles, and the highest thermal conductivity coefficient for NCF2 (1.83 W mK−1) was measured at 4 W.

Highly thermally conductive polymer nanocomposites based on boron nitride nanosheets decorated with silver nanoparticles

RSC Advances ◽  
2016 ◽  
Vol 6 (47) ◽  
pp. 41630-41636 ◽  
Author(s):  
Fangfang Wang ◽  
Yimin Yao ◽  
Xiaoliang Zeng ◽  
Tao Huang ◽  
Rong Sun ◽  
...  
Keyword(s):  
Silver Nanoparticles ◽  
Boron Nitride ◽  
Thermal Resistance ◽  
Polymer Nanocomposites ◽  
Conductive Polymer ◽  
Interfacial Thermal Resistance ◽  
Boron Nitride Nanosheets ◽  
Thermally Conductive

The interfacial thermal resistance among boron nitride nanosheets are reduced by sintering silver nanoparticles deposited on boron nitride nanosheets surfaces, beneficial for the forming networks.

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