Heat Transfer Enhancement of Falling Film Evaporation of HFO-1233zd(E) and HFC-134a on a Horizontal Tube by Thermal Spray Coating

A falling film evaporator can reduce the amount of refrigerant compared with a flooded evaporator. Required functions for the heat transfer surface in falling liquid film evaporation are thin liquid film formation without breaking at low heat flux, nucleate boiling promotion in liquid film, and suppression of liquid entrainment at high heat flux. In this study, a porous thermal spray coating using copper as the coating material was made on a copper cylinder. The heat transfer performance of falling film evaporation and pool boiling was evaluated using HFO1233zd(E) as the refrigerant, and the obtained results were compared with those for HFC-134a. The test cylinder was heated by a cartridge heater inserted at the center. Falling film evaporation experiments had been conducted with a film mass flow rate of 3.3×10-2 kg/(m·s), heat flux of 10 to 85 kW/m2, and a saturation temperature at 20 ºC. The effects of the thermal spray coating, heat flux and thermo-physical properties of the refrigerants on heat transfer performance were investigated. The heat transfer coefficient increased with increasing heat flux. For the thermal spray coating, a large hysteresis effect according to the heating procedure with increasing or decreasing heat flux was observed in the characteristics of the heat transfer coefficient. The heat transfer enhancement factor by the thermal spray coating was up to 4.8. The value was higher than that for HFC-134a, especially under high heat flux condition. In the comparison between pool boiling and falling film evaporation heat transfer, falling film produced higher heat transfer coefficients for the thermal spray coating while the heat transfer on the smooth surface deteriorated due to partial dryout. The fine porous structure enhanced liquid spreading by the capillary force and evaporation from the liquid film surface by vapor bubble agitation

Effect of Flow Direction of Heating Medium on Boiling Heat Transfer Characteristics in a Single-Channel Plate-Fin Heat Exchanger

This study deals with evaporative heat transfer characteristics of vertically upward flows in single-channel plate-fin heat exchangers. R-134a was used as the refrigerant. The refrigerant channel was sandwiched by two water channels with the same channel shape. The refrigerant was heated by hot water from the both side. In this experiment, pressure of the working fluid was maintained at 0.665 MPa (saturation temperature is 25 °C)．Subcooled liquid with the subcooling of 5 and 10 K, or wet vapor with the quality of 0.1 was supplied to the evaporator. Two kinds of offset fin, Fin A and B, whose fin pitch were 1.95 and 3.175 mm, respectively, were used. The channel hydraulic diameter with Fin A and Fin B were 1.78 and 2,89 mm, respectively. Effects of the fin pitch and flow direction of the heating water, such as counter and parallel flow arrangements, on the heat transfer rate, pressure drop, and wall temperature distribution on the outside of the water channel were examined. The wall temperature was visualized by an IR camera. As the results, it was shown that the effects of the flow direction of water and the fin pitch on the heat transfer rate were a little due to a dryout in the refrigerant flows. However, a large difference in the wall temperature distribution between the counter and parallel flow was observed. The difference might be caused by the phase distribution of refrigerant, and lead to the increase in the pressure drop for the parallel flow. For the parallel flow arrangement, the temperature on the right side with the water inlet port was quite higher than the right side. The temperature distribution was kept over the heat exchanger. The tendency was weaker for Fin B with the larger fin pitch due to phase separation caused by gravity

Development of Track Condition Monitoring System Using Onboard Sensing Device

Monitoring the conditions of railway tracks is essential for ensuring the railway safety. In-service vehicles equipped with sensors and GPS systems can act as probes to detect and analyse real-time vehicle vibration. Recently, a compact on-board sensing device has been developed. This chapter describes the track condition monitoring system that uses a compact on-board sensing device and diagnosis software. The diagnosis software provides the function of detecting track faults using the root mean square (RMS) of the car-body acceleration. It also allows analysis in the time-frequency domain using wavelet transform. A monitoring experiment in a local railway line showed that the system is effective for practical application

高齢者福祉の実証的研究 : 豊かな高齢期に向けて

関西学院大

Gene expression changes during caste-specific neuronal development in the damp-wood termite Hodotermopsis sjostedti

<p>Abstract</p> <p>Background</p> <p>One of the key characters of social insects is the division of labor, in which different tasks are allocated to various castes. In termites, one of the representative groups of social insects, morphological differences as well as behavioral differences can be recognized among castes. However, very little is known about the neuronal and molecular bases of caste differentiation and caste-specific behavior. In almost all termite species, soldiers play defensive roles in their colonies, and their morphology and behavior are largely different from workers (or pseudergates). Therefore, we predicted that some genes linked to defensive behavior and/or those required for neuronal changes are differentially expressed between workers and soldiers, or during the soldier differentiation, respectively.</p> <p>Results</p> <p>Using the brain and suboesophageal ganglion (SOG) of the damp-wood termite <it>Hodotermopsis sjostedti</it>, we first screened genes specifically expressed in soldiers or during soldier differentiation by the differential display method, followed by quantitative real-time polymerase chain reaction. No distinctive differences in expression patterns were detected between pseudergates and soldiers. In the course of soldier differentiation, however, five genes were found to be up-regulated in brain and/or SOG: 14-3-3epsilon, fibrillin2, beta-tubulin, ciboulot, and a hypothetical protein containing a SAP motif. Some of these genes are thought to be associated with cytoskeletal structure or motor-associated proteins in neuronal tissues.</p> <p>Conclusion</p> <p>The identified five genes could be involved in soldier-specific neuronal modifications, resulting in defensive behaviors in termite soldiers. The temporal expression patterns of these genes were consistent with the neuronal changes during soldier differentiation, suggesting that molecular machineries, in which the identified factors would participate, play important roles in behavioral differentiation of termite soldiers.</p