Mechanism of the heat exchange promotion by superimposing the external sound wave in standing-wave thermoacoustic system

For improvement of energy conversion efficiency, sound wave is superimposed with a loudspeaker to the working fluid in the stack. By using this method the work-flow generation of the stack was enhanced. To analyze this enhancement mechanism, the thickness of the boundary layer and the heat exchange area in the stack are calculated from the view point of heat exchange circumstance. The effect of the heat exchange circumstance on the particle displacement and heat flow is investigated. As a result, it is confirmed that the superimposed sound wave improves the heat exchange circumstance and then the thermoacoustic phenomenon is enhanced.

Conditional Mutation of Hand1 in the Mouse Placenta Disrupts Placental Vascular Development Resulting in Fetal Loss in Both Early and Late Pregnancy

Congenital heart defects (CHD) affect approximately 1% of all live births, and often require complex surgeries at birth. We have previously demonstrated abnormal placental vascularization in human placentas from fetuses diagnosed with CHD. Hand1 has roles in both heart and placental development and is implicated in CHD development. We utilized two conditionally activated Hand1A126fs/+ murine mutant models to investigate the importance of cell-specific Hand1 on placental development in early (Nkx2-5Cre) and late (Cdh5Cre) pregnancy. Embryonic lethality occurred in Nkx2-5Cre/Hand1A126fs/+ embryos with marked fetal demise occurring after E10.5 due to a failure in placental labyrinth formation and therefore the inability to switch to hemotrophic nutrition or maintain sufficient oxygen transfer to the fetus. Labyrinthine vessels failed to develop appropriately and vessel density was significantly lower by day E12.5. In late pregnancy, the occurrence of Cdh5Cre+;Hand1A126fs/+ fetuses was reduced from 29% at E12.5 to 20% at E18.5 and remaining fetuses exhibited reduced fetal and placental weights, labyrinth vessel density and placenta angiogenic factor mRNA expression. Our results demonstrate for the first time the necessity of Hand1 in both establishment and remodeling of the exchange area beyond early pregnancy and in patterning vascularization of the placental labyrinth crucial for maintaining pregnancy and successful fetal growth.

MULTI-FACTOR HEAT EXCHANGER DESIGN MODELS

Compressed air is widely used in enterprises, and it is possible to reduce air consumption on pneumatic devices by heating. Most often, heating is carried out in shell-and-tube heat exchangers. To increase the area of heat exchange between the heating medium and the air, finned tubes are used, which can significantly reduce the volume occupied by the heater. The design of the heater is influenced by many factors, and the importance of the influence of each of them can differ significantly. It is advisable to use the overall characteristic in the form of a compactness factor, which shows the ratio of the heat exchange area to the volume of the heater. The work developed a method for determining the optimal design of heaters by such a parameter as the compactness factor. The obtained regression equations make it possible to determine the influence of such factors as the number of rows of tubes across the flow and the length of one tube on the volume occupied by the heat exchanger and the compactness factor. According to Fisher's criterion, the equations of the model are adequate to the true dependence with a confidence level of 95%. Most of all, the volume of the heat exchanger and the compactness are affected by the number of tubes transverse to the air flow. Changing the length of one tube does not fundamentally affect the obtained values of the output parameters. With an increase in the length of one tube and their number across the flow, it is possible to achieve the highest values of the compactness coefficient, the dependence of which on the main factors has a pronounced maximum. Using the developed technique, it is possible, in a fairly simple formulation, to analyze the value of the compactness factor for various combinations of the above factors and to optimize the design of the heater.

TEMPERATURE MEASUREMENT OF POLYMERS UNDER INTERMITTENT HEATING THROUGH USE OF THERMOCOUPLE AND ARDUINO® MICROCONTROLLER

The combination of relatively low production costs and a versatility makepolymers one of the most used classes of engineering materials. Thecomplexity of their chemical bounds, however, make the thermomechanicalprocessing of these materials a challenge since thermal flux frommanufacturing might significantly alter their properties. In this paper wasevaluated the use of thermocouple with Arduino® compatible hardware formeasurement and control of an intermittent heating system for processing ofNylon-6 and polycarbonate thermoplastics. A 2² factorial design was createdfor using K-type thermocouple for the two polymers at two different surfacefinishes obtained by sanding with mesh #80 and #600 abrasives. The resultsindicate that the Arduino interface has satisfactory processing capacity formonitoring heating cycles and temperature logging, making it possible toknow how temperature variated and at what level it stabilized for the heatingconditions presented. The difference in material specific heat capacity andthermal conductivity will affect the observed temperature profile. Roughnessmight present a considerable effect on the material heating since it is linkedto the heat exchange area of the process.

Anatomy and physiology

This chapter covers some fundamental aspects of the respiratory tract, and describes the structure and function of both the upper and lower airways, processes by which air is moved from the external environment to the gas exchange area of the lungs, and some of the aspects of the normal respiratory tract which are affected by the more common respiratory diseases. Its functions in terms of respiration are to facilitate the uptake of oxygen; eliminate carbon dioxide; and maintain the pH of the blood. Conventionally the tract is divided into upper and lower parts. The upper tract is composed of the mouth, nasal passages, and behind these a wide tube termed the pharynx. This receives inhaled air from the nose and mouth and accordingly is termed the naso- and oropharynx, respectively.

Numerical Simulation of The Effect of Baffle on Heat Transfer Performance of Shell-and-Tube Heat Exchanger

Baffle heat exchanger is widely used in various production activities because of its simple design and strong adaptability, so the structural optimization of baffle heat exchanger is of great significance to engineering practice. COMSOL software was used to simulate the shell-and-tube heat exchanger with baffles. By comparing and analyzing the simulation results, we find that the temperature field and pressure field of baffle plate are distributed evenly; The existence of baffles leads to the transverse flow of air, which increases the heat exchange area. Another advantage of using baffles is that vibration due to fluid flow can be reduced.

Performance Evaluation of Photovoltaic/Thermal (PV/T) System Using Different Design Configurations

This study summarizes the performance of a photovoltaic/thermal (PV/T) system integrated with a glass-to-PV backsheet (PVF film-based backsheet) and glass-to-glass photovoltaic (PV) cells protections. A dual-fluid heat exchanger is used to cool the PV cells in which water and air are operated simultaneously. The proposed PV/T design brings about a higher electric output while producing sufficient thermal energy. A detailed numerical study was performed by calculating real-time heat transfer coefficients. Energy balance equations across the dual-fluid PV/T system were solved using an ordinary differential equation (ODE) solver in MATLAB software. The hourly and annual energy and exergy variations for both configurations were evaluated for Cheonan City, Korea. In the case of a PV/T system with a glass-to-glass configuration, a larger heat exchange area causes the extraction of extra solar heat from the PV cells and thus improving the overall efficiency of the energy transfer. Results depict that the annual electrical and total thermal efficiencies with a glass-to-glass configuration were found to be 14.31% and 52.22%, respectively, and with a glass-to-PV backsheet configuration, the aforementioned values reduced to 13.92% and 48.25%, respectively. It is also observed that, with the application of a dual-fluid heat exchanger, the temperature gradient across the PV panel is surprisingly reduced.