The thermophysical properties of refrigerant can be modified via adding solid materials to it. In this paper, molecular simulations and thermodynamic calculations were employed to investigate the adsorption and energy storage of ethane (R170), 1,1,1,2-tetrafluoroethane (R134a), 1,1,1-trifluoroethane (R143a), and 1,1-difluoroethane (R152a) in metal organic framework (MOF)-5 nanoparticles. The results show that the fluorine atom in the refrigerants will strengthen the adsorption of refrigerants in MOF-5. However, the fluorine-free refrigerant, R170, owns larger enthalpy difference of desorption than the other refrigerants with fluorine under high pressure. The thermal energy storage capacity of the refrigerant/MOF-5 mixture is larger than that of the pure refrigerant at low pressure. Also, the negative enhancement of the energy storage property of the mixture is found in some cases when the refrigerant experiences phase transition.
Accurate measurement of overvoltage in power grids is of great significance to study the characteristics of overvoltage and design of insulation coordination. Based on the research of D-dot voltage sensor, we designed a Dual-Differential D-dot overvoltage sensor. In order to quantify the structural parameters of the sensor, improve the performance and measurement accuracy of the sensor. The Field-Circuit Coupling method was proposed to be used in the parameter design of D-dot overvoltage sensor. The joint simulation of space electromagnetic field model and equivalent circuit model of the Dual-Differential D-dot overvoltage sensor was established with the finite element simulation software Ansoft Maxwell and circuit simulation software Simplorer. Finally, the actual sensor was manufactured. A test platform was built to verify the steady-state and transient performance of the sensor. The results show that the Dual-Differential D-dot sensor has excellent steady-state and transient performance, the error of phase and amplitude are small, and the sensor can achieve the non-contact measurement of power transmission line. Simultaneously, the rationality of the Field-Circuit Coupling method was further verified.
Currently, there are two non-contact measurement methods of the transmission line voltage based on field sensor: one is calculation with the inverse problem of electric field for the solution, and the other is to solve by the numerical integration algorithm. In general, the first one is confronted with data equation solving problems and difficulties in accurate calibration as well as low precision, while the second one is troubled by the complexity of algorithm equation and unsatisfactory integration node. In view of the above problems, this paper improves on the basis of the Gaussian integral algorithm to seek better nodes, in order to reduce the difficulty of solving and improve the measurement accuracy of the integral algorithm. First, starting from the Gaussian integral algorithm and making research to improve the Gaussian integral algorithm theory. Then, the finite element simulation of three-phase transmission line through Maxwell software is built, and the space electric field distribution data is acquired to calculate an integral node as well as its corresponding weights. Finally, the three-phase transmission line voltage measurement test platform with D-dot sensor voltage measurement system is built to test verification. The text results show that the voltage measurement method based on the improved Gaussian Integral has characteristics of a simple solution, better integral node, and higher precision, and all the measured voltage errors are less than 0.45%. INDEX TERMS Non-contact measurement, improved Gaussian integral, Maxwell software, D-dot sensor.
Generally, with the help of adding solid materials, the thermophysical behaviors of refrigerant can be modified. In this work, four kinds of organic refrigerants (i.e. ethane R170, 1-fluoroethane R161, 1,1-difluoroethane R152a, and 1,1,1-trifluoroethane R143a) mixed with metal–organic framework UIO-67 nanoparticles are selected as the objects, their thermodynamic energy, adsorption, desorption heat, and energy storage properties are investigated by means of molecular simulations and thermodynamic calculations. The simulation method and calculation details are elaborated. The results illustrate that the relationship between the change of thermodynamic energy and the temperature is linear, and the adsorption of refrigerants in UIO-67 can be reinforced owing to the fluorine atom in the refrigerants. However, R170, the fluorine-free refrigerant, has greater enthalpy variation of desorption than the other three refrigerants containing fluorine atom under some pressures. The thermal energy storage capacity of the refrigerant/UIO-67 mixture is greater than that of the pure refrigerant at low pressure. Meantime, as the refrigerant undergoes phase transition, the weakened improvement of the energy storage property of the refrigerant/UIO-67 mixture is found in some cases. This work can not only enrich the content of researches about metal–organic heat carrier nanofluids (MOHCs), but also provide guidance for the performance improvement and practical application of organic refrigerants.
This paper proposes a coil design method for the magnetically coupled resonant wireless power transfer (MCR-WPT) system. Based on the Biot–Savart law, the magnetic flux density at the observation point was derived, and the magnetic flux of the observation plane generated by the exciting coil was deduced to build the calculation model of power transfer efficiency (PTE) and power delivered to the load (PDL). The PTE and PDL curves via coil parameters could be fitted in minutes using numerical calculation. The coil was designed according to transmission objectives and dimension constraints. In addition, the calculated PTE and PDL were compared with those from finite element analysis to verify the credibility of the method. Finally, the actual curves of PTE and PDL were achieved, which showed a strong positive correlation with the corresponding curves from the calculation model. The relative average deviations of PDL curves were less than 6.11%. Meanwhile, coils designed with the numerical calculation could realize 309.80 W and 88.51%, which achieved the objectives under the constraints. The results demonstrate that the proposed method can realize a rapid and accurate coil design under constraints. It can also be applied to other coil structures or circuit topologies with strong universality.
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