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A point heat sink is produced by impinging a high frequency microscale droplet stream onto a superheated copper substrate. Although the overall target surface area is larger than the liquid-solid interface by two or three orders of magnitude, the thermal energy is mainly removed through the point heat sink rather than the rest dry area. Therefore, the spherical conduction patterns in the solid materials are observed with a "nozzle-shifting" method which requires only two temperature probes. The temperature gradient in the vicinity of the impingement stagnation point is tremendously high, suggesting that the liquid-solid interface temperature is significantly lower than the far-field bulk temperature of the substrate. Moreover, the liquid-to-solid heat transfer is measured, which agrees well with the theoretical prediction. The maximum interface heat flux can reach around 80W/mm². It is insensitive to the substrate temperature in a relatively wide temperature range, which brings conveniences to the potential industrial applications. [ABSTRACT FROM AUTHOR]

A two-dimensional numerical simulation model for a membrane-based heat and mass exchanger was developed. The system model equations were used to determine the coupled heat and moisture transfer from the humid air to the high concentrated liquid desiccant solution (LiCl, lithium chloride) by means of a parallel stack hydrophobic permeable membrane. The two streams of air and liquid desiccant solution were arranged in cross-flow directions. The fourth-order Runge–Kutta method was employed to solve these system model equations in a steady-state condition. This model enables one to predict the latent effectiveness of a membrane-based parallel cross-flow exchanger for dehumidification purpose in response to air to liquid mass flow ratio and the mass transfer unit number. [ABSTRACT FROM AUTHOR]

Exergy analyses provide to investigate the available work performance of thermal cycles. In this study, exergy analyses have been conducted for the conventional micro-cogeneration system and the Liquefied Natural Gas (LNG) cold utilized micro cogeneration system, respectively to detect exergy destruction and loss ratios which are related to second law analyses. In the LNG cold utilized micro-cogeneration system, the exhausted gas of micro turbine is supplied to the LNG vaporizer to change the phase of LNG from liquid to gas. Due to fact that exergy destruction and loss rates, exergetic efficiency decreases with the ambient air temperature increment by nearly 28%. Owing to the application of exhausted gas in the LNG vaporizer in the LNG cold utilized micro-cogeneration system, the exergy loss ratio decreases by approximately 81% when it is compared to the conventional micro-cogeneration system. At the same time, the exhausted gas temperature decreases nearly 2.93 K. Exergy destruction ratio is another evaluation criterion for exergy analyses and it is seen that the combustion chamber had a significant impact on the overall exergetic performance of both systems. The minimum exergy destruction rate belongs to the LNG pump and also the LNG vaporizer does not have a significant exergy destruction ratio. [ABSTRACT FROM AUTHOR]

Few studies have been studied on the LNG cold utilization with micro-cogeneration systems while many studies were related to large scale power generation systems. This study proposes a combined LNG cold utilized micro-cogeneration system which includes an LNG pump, an LNG vaporizer, a combustion chamber, a recuperator, a compressor, a gas turbine and a heat exchanger. Economic, energetic and environmental analyses are conducted according to various ambient air temperatures and the results are compared with overall performance of the conventional micro c-generation system. The generated electricity rate and the thermal efficiency are found the same for both investigated cycles. However, the payback period is approximately 6% higher than the conventional cycle. The mean environmental payback period was found approximately 4.8 years. [ABSTRACT FROM AUTHOR]

Transition phenomena are observed when a water droplet train (with up to 18.9 m/s in velocity and 39.20 kHz in frequency) impinges onto a heated copper surface (up to 250 C). The hydrodynamic flow pattern strongly depends on the wall temperature. The surface temperature does not apparently influence the spreading speed when the wall temperature is less than the boiling temperature, but it enhances the spreading rate significantly at higher surface temperatures. A "steady-state" wetting surface area can be reached when the water supply rate equals the water consumption rate. The time-independent spreading diameter decreases with an increase in the wall temperature until an ultimate diameter of the "steady-state" wetting area is observed at around 0.4 mm, 3.4 times the droplet diameter, when the surface temperature is higher than 190 °C. Moreover, unlike the random direction splashing when wall temperature is less than 180 °C, a stable splashing angle is established at higher wall temperatures. However, the angle reduces apparently with the increase in the wall temperature. [ABSTRACT FROM AUTHOR]

The field study was conducted under All India network Research Project on Onion and Garlic, at Department of vegetable science, C.S. Azad University of Agriculture and Technology, Kalyanpur Kanpur (U.P.) during Rabi season 2010-11 to 2012-13 to recognized the effective, ecofriendly IPM modules for management of onion thrips (Thrips tabaci Lindeman) in onion. The treatment consisted of M1: IPM module, M2: Farmer's Practices and M3: Control, laid out in CRD. The result indicated that both M1 and M2 not only significantly reduced the thrips population (9.59 and 7.56 thrips/ plant) but also increased total marketable yield (29.36 and 29.67 t/ ha), respectively. Higher B: C Ratio was recorded in M1 (12.66) than M2 (8.47). It may be concluded that adoption of IPM module not only reduces thrips infestations but also produces better yield with higher B: C Ratio in onion. [ABSTRACT FROM AUTHOR]

Current commercial photovoltaic (PV) conversion efficiency (flat plate modules) is about 6--20%, depending on the materials used for the module construction. Since only a small fraction (<10%) of the incident solar energy is reflected and/or transmitted, a large fraction of the solar radiation is converted into heat. If this heat can be harvested as well, the overall energy efficiency of such an integrated photovoltaic thermal (PVT) hybrid system will be greatly improved. At the same time, pumping water through the PV modules will cool (if Twater< Tmodule) the solar cells and improve their electricity production efficiency. This article describes the design and numerical simulation of a PVT system for producing electricity and hot water in a student hostel in Singapore. The nominal electrical power output is 10 kWp(kilowatt peak). Thermal models were developed based on basic energy balance equations and average climatic conditions for Singapore over a typical year were used. A survey of the hot water usage pattern over a typical week was carried out and used in the simulation. The optimum mass flow rate in the collectors is found to be 0.039 kg/(s m2) and the optimum storage tank capacity for hot water is 2500 kg for a showering load of around 6000 kg/day. The average thermal and electrical efficiency of the system are 43% and 12%, respectively. The requirement of auxiliary electric energy for water heating is predicted to be reduced by 94%. [ABSTRACT FROM AUTHOR]

Unlike the traditionally reported Leidenfrost droplet which only floats on a thin film of vapor, we observe a prominent jump of the impinged droplets in the transition from the contact boiling to the Leidenfrost state. The vapor generation between the droplet and the substrate is vigorous enough to propel the spreading droplet pancake to an anomalous height. The maximum repellent height can be treated as an index of the total transferred energy. Counterintuitively, a stronger vaporization and a higher jump can be generated in the conditions normally considered to be unfavorable to heat transfer, such as a lower substrate temperature, a lower droplet impact velocity, a higher droplet temperature, or a lower thermal conductivity of the deposition on the substrate. Since the total transferred energy is the accumulation of the instantaneous heat flux during the droplet contacting with the substrate, it can be deduced that a longer contact time period is secured in the case of a lower instantaneous heat flux. The inference is supported by our experimental observations. Moreover, the phase diagrams describe the characteristics of the high repellency under different substrate temperatures, droplet subcooling temperatures, and Weber numbers. It allows us to manipulate the droplet jump for the relative applications. [ABSTRACT FROM AUTHOR]