Thermal Transfer Characteristics Research Articles

Comparison of thermal transfer characteristics of wood flooring according to the installation method

There are two types of installation methods for wood flooring; a floating installation method for laminate flooring, and an adhesive installation method for engineered flooring. Thermal transfer characteristics from the floorings show a significant difference depending on the installation method, so this study focused on the comparative thermal transfer characteristics by preparing mock-up scale. The laminate flooring and the modified engineered flooring of the Korean Standard were used to conduct the tests. The tests were set up in two rooms in an apartment in Seoul, and a water heat source was prepared at 45°C and 75°C. As a result, the velocity of thermal transfer of the modified engineered flooring using adhesive was faster than that of the laminate flooring. There was no difference of temperature between both samples at 45°C of water supply, but a great difference was shown at 75°C. Moreover, installing the modified PE foam helped the floating installation method to develop a thermal transfer performance comparable to that of the preceding research.

Effect of interfacial structure on the thermal conductivity of carbon nanofibers reinforced aluminum nitride composites

The interface in carbon nanofilaments/ceramic–matrix composites significantly affects the interfacial thermal transfer characteristics. In this work, the effect of interfacial structure on the thermal conductivities of carbon nanofibers (CNFs)/aluminum nitride (AlN) composites with and without sintering aids (Y2O3 and CaF2) were studied. For the composites sintered with aids, the interfacial amorphous glass phases originated from the aids and Al2O3 layer in AlN powders surrounded the CNFs, which acted as elongated pores for deteriorating the thermal conductivity. However, a clean interface was obtained in the composites without aids because the amorphous carbon and the Al2O3 layers in the CNF–AlN system were removed by their interreaction to form volatile products such as Al2O and CO, resulting in the enhanced thermal conductivity. Moreover, theoretical analysis was also employed to investigate the effect of the interfacial structure on the thermal conductivity of the CNFs/AlN composites.

Phase State and Physical Properties of the Mo-Ru-Ph-Pd Alloys

ABSTRACTMo3Ru5MPd (M = Ru, Rh, Pd) as the simulated materials for the undissolved residue in the nuclear fuel reprocessing were prepared by arc melting method. The physical properties and oxidation behavior of the alloys were evaluated from viewpoint of the safety and economy in the reprocessing. The electrical resistivity, ρ, of Mo3Ru5RhPd was shown to be 0.8 μΩm at room temperature. On the other hand, the ρ values of samples without Rh were marked at 0.4 μΩm. The thermal properties of the each sample had the different thermal transfer characteristics. In particular, although the thermal conductivities of Mo3Ru5RhPd and Mo3Ru5Pd2 samples show almost the same value, the lattice thermal conductivities of both samples showed different values. Oxidation behavior was analyzed using the thermogravity(TG) and differential thermal analyses(DTA). The TG curve of each sample by oxidation showed different results. These results indicate that the simulated materials of the alloys without Rh: Mo-Ru-Pd were not appropriate to simulate the thermophysical characteristics of the typical simulated materials with undissolved residue Mo-Ru-Rh-Pd alloys. Therefore, in the spent nuclear fuel reprocessing, the mock test of reprocessing without to use Rh is difficult to carry out.

Heat transfer to deep tissue: the effect of body fat and heating modality

The purpose of this study was to quantify the thermal transfer characteristics of the skin in relation to body composition as assessed by the ability of water immersion and hot and cold packs with different thicknesses of towels layers to heat or cool deep tissue. Two sets of experiments were conducted to determine the interrelationships between body fat content and muscle temperature after immersion of the limb in water or the application of hot and cold packs. In the first series of experiments, subjects immersed their lower body in water at 42, 37, 34, 27, 24 and 0 °C for 20 minutes. Muscle temperature was measured in the skin above and in the belly of the quadriceps and medial gastrocnemius muscles by a thermistor on the skin and one implanted with a 20-gauge needle 25 mm below and perpendicular to the skin. To see the effect of circulation, a series was conducted with the circulation occluded. In the second series, hot or cold packs were used with different thicknesses of towel layers. The muscle temperature after immersion in water approached that of the packs within approximately 20 minutes. In contrast, when hot and cold packswere used with various thickness or towels ranging from 2 to 10 mm in thickness, the change in muscle temperature was much less and it was still changing at the end of a 20 minute period. Subjects with high body fat changed their deep tissue temperatures much more slowly with a time constant nearly double that of the thin subjects with all modalities. Even after water immersion, if the body fat exceeded 25% of the subject's weight, 20 min of immersion was not enough to either warm the muscle or cool it down substantially. Cold packs and hot packs were very ineffective in changing muscle temperature under these same conditions. Body fat plays a major role, as did limb blood flow in controlling the movement of heat across the limb.

Thermal simulations of three-dimensional integrated multichip module with GaN power amplifier and Si modulator

A finite-element simulation was used to quantitatively estimate the heat transfer in a three-dimensional multichip module (MCM) consisting of a GaN power amplifier with solder-bump-bonded Si modulator and integrated antenna on a high-resistivity SiC substrate under various conditions of power density and substrate and epi thicknesses via wire thickness and effective heat transfer coefficient. The maximum temperature in the integrated-antenna approach occurred in the center of the MCM. At a GaN power amplifier power level of 3W∕mm, a steady-state temperature of ∼125°C was reached in ∼20s. Bulk GaN substrates were also found to provide good thermal transfer characteristics, while sapphire produced an increase in temperature almost a factor of 3 higher than for SiC. At a power density of 10W∕mm, the steady-state operating temperature was ∼400°C even with SiC substrates.

Performance of a new high-intensity silicon solar cell

A new silicon solar cell, designed to have improved electrical, optical, and thermal transfer characteristics at very high incident light intensities, has been fabricated and provides experimental verification of the basic design concepts. The AM1 efficiency for nonoptimized cells is 12.8% at 25 °C. At 300 suns the efficiency increases to 19%. It is shown that efficiencies of over 25% are possible for this type of cell in a more-optimized form at intensities of ∼500–1000 suns.

High Power CW Operation of GaAs Injection Lasers at 77° K

Continuous-wave operation of GaAs injection lasers depends critically upon the junction temperature <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sup> , <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> which, in turn, depends critically upon the heat flow from the laser body. <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> , <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> There are two instances in thel iterature in which continuous operation at 77° K was achieved at very low output power levels. In one, both mirror-ends of a Fabry-Perot structure were partly silvered; <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> in the other, stimulated emission was observed from a unit with four cleaved sides. <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup> The purpose of this communication is to report that continuous-wave operation at 8400 Å of unsilvered GaAs lasers at 77° K has been consistently achieved at power levels near 0.65 watt and to describe the heat sink structure which has afforded the necessary thermal transfer characteristics