An experimental study on the subcooled flow boiling pressure drop of R141b in the system of two microchannels

An experimental study of the pressure drop under subcooled flow boiling of the refrigerant R141b in a system with two slotted microchannels was carried out. A copper block with two microchannels 2 mm wide, 0.4 mm deep, and 16 mm long was used as an experimental section for testing. The mass flow rate varied in the range from 1 to 4 g/s, the initial subcooling from 20°C to 50°C. Experimental data show a significant decrease in the pressure drop when the critical heat flux is reached. The experimental data are compared with the model known from the literature. Experimental data show that the occurrence of nucleate boiling incipience at subcooled boiling corresponds to a larger heat flux than that given by the recommended correlation.

Microstructure of Archaeological 17th Century Cast Copper Alloys

In Poland, researchers have a very strong interest in archaeometallurgy, which, as presented in classical works, focuses on dating artefacts from the prehistoric and early medieval periods in the form of cast iron and copper castings. This study, extending the current knowledge, presents the results of a microstructure investigation into the findings from the Modern era dating back to the late Middle Ages. The investigated material was an object in the form of a heavy solid copper block weighing several kilograms that was excavated by a team of Polish archaeologists working under the direction of Ms Iwona Młodkowska-Przepiórowska during works on the marketplace in the city of Czestochowa during the summer of 2009. Pre-dating of the material indicates the period of the seventeenth century AD. The solid copper block was delivered in the form of a part shaped like a bell, named later in this work as a “kettlebell”. To determine the microstructure, the structural components, chemical composition, and homogeneity, as well as additives and impurities, investigations were carried out using light microscopy, scanning electron microscopy including analysis of the chemical composition performed in micro-areas, and qualitative X-ray phase analysis in order to investigate the phase composition. Interpretation of the analytical results of the material’s microstructure will also help modify and/or develop new methodological assumptions to investigate further archaeometallurgical exhibits, throwing new light on and expanding the area of knowledge of the use and processing of seventeenth-century metallic materials.

Transient Analysis of Microchannel Heat Sink during Single Phase and Flow Boiling Conditions

In the present work, an experimental investigation has been made to analyze the performance of microchannel heat sink under transient operating conditions. The transient analysis has been made by estimating the response time for different input heat flux and coolant mass flow rate. Analysis has been made for rectangular cross-section microchannels fabricated on a copper block of size 25.7 × 12 × 10 mm3. Twelve (12) numbers of microchannels are fabricated in the copper block. The width and depth of individual channels are 400 μm and 750 μm respectively. Performance analysis has been made for both single phase and flow boiling conditions of the coolant flow using deionized water as coolant. Experiments have been performed for coolant mass flux (G) range of 90 - 250 kg/m2s and input heat flux (q) range of 20 - 300 kW/m2 respectively. It has been observed that at constant input heat flux, response time decreases with the increase in coolant mass flux during single phase cooling. However this trend is not strongly followed during the two-phase or flow boiling cooling condition.

Physics Learning Based on Practicum: Factors that Affecting Expansion

An object when heated will undergo expansion. Expansion of an object is affected by the expansion coefficient, temperature, and type of object substances that cause the length, area, and volume of the object and other objects differently. Based on these concepts, to investigate the comparative increase in the size of the object that is affected by factors that affect the expansion by heating the body until it reaches the equilibrium temperature. As the object under study will use a block of copper and water with each volume to be measured 10-5 m3 added volume ratio. With the initial temperature of each object 20 oC, both substances will be heated up to a temperature of 30oC, 35oC, 40oC, 45oC, dan 50oC. Both substances are then calculated and compared to the increase in volume experimentally and theoretically. After calculation, a score which indicates that the copper block and the water volume is different. Increase the volume of water is greater than the increase in the volume of copper block in each temperature increment. Both these substances are two different substances that have different volume expansion coefficient as well. So we get that expansion coefficient, temperature, and type of object substances have an affect on the expansion that occurs on an object.

CHIRALITY-ASYMMETRY MACROSCOPIC FORCE INDUCED BY AXION BETWEEN THE α-QUARTZ AND COPPER BLOCK

A macroscopic force induced by the effective potential suggested by Moody and Wilczek between α-quartz crystal and copper block is studied in detail. The matrix elements in the force formula are analyzed according to representations of the non-symmorphic space group P 3121 of α-quartz crystal. The asymmetry distribution of valence electrons and the selection rules do not cancel the force. We conclude that there exists a CP-violating macroscopic force. According to the limit of the production of the axion coupling constants gs gp/ℏc ≤ 10-26 at the Compton wavelength λ = 10-3 m, the macroscopic force between a 0.08 × 0.08 × 0.02 m3 block of α-quartz and a 0.08 × 0.08× 0.01 m3 copper block with a separation being 0.5 × 10-3 m in between, is estimated at less than 3.09 × 10-26 N.