In this paper, the EHD coupled heat transfer systems have been investigated using a double electrodes' cylinder heat transfer model. Freon-11 is selected as working fluid. The condensation coefficient, the boiling heat flux and the saturation pressure are measured in this investigation. According to the experimental results, it is found that the electrical field can enhance both boiling and condensation heat transfer. The enhancement of condensation heat transfer is more obvious than that of only one electrode heat transfer model. The experimental results have been discussed.

In this study, the surface charge distribution on insulators in vacuum has been investigated under an impulse voltage (0.7/4μS) with a non-uniform field electrode system. The insulators studied were 99.9% alumina specimens with the shape of right circular cylinders about 5mm thick and 20mm in diameter. Using an electrostatic probe with shield in the form of capacitive voltage divider that was connected to an electrometer, the surface charge distribution on insulators were measured. The applied impulse voltage, and the corresponding current waveforms, the signal of luminosity were also observed during the voltage application. We investigated the surface charge distributions at different impulse voltage levels, at different shot number with a same voltage level, at the situations after a flashover occurred. Based on the experimental results, we found that the surface charge density on insulators is increased with the increase of the applied voltage, the shot number has a little influence at the same voltage level, and the charge density is decreased a lot after a flashover occurs. It's also found that the increase of charge density is often accompanied by the preflashover events.

This paper presented some new experimental results observed in our investigation. Based on the experiments, it was found that the different voltage application sequence on the test samples could influence the flashover voltage of the tested samples. Three kinds of voltage application sequences were compared and three kinds of Alumina samples were involved in this paper. In general, the flashover voltage is the lowest if the applied voltage started from a lower voltage (-2kV) at a -2kV step; the flashover voltage could be the highest if the applied voltage started from -22kV. The surface charge distributions were observed after the voltage was applied. According to the experimental results, the change of the flashover voltage of the test samples could be attributed to the state of surface charge distribution with different voltage application sequence.

This paper reports on the infuence of sintering conditions on the flashover/preflashover characteristics of alumina insulators in vacuum under an impulse voltage. Four kinds of alumina insulator were studied, which were prepared using the same formula with different sintering conditions. The surface pre-flashover and flashover phenomena of different samples in vacuum have been observed under impulse voltage. Based on the experimental results, the characteristics of pre-flashover and flashover vary with different kinds of test samples. It was found that the insulators with a higher sintering temperature had a lower flashover voltage, and more active pre-flashover. From a scanning electron microscope (SEM) analysis of alumina insulators, we conclude that the methods of preparing alumina samples can affect their microstructure resulting in a change in the pre-flashover and flashover performance as alumina insulators.

In this paper, the Influences of electrical field on boiling-condensation heft transfer system have been investigated using a cylinder beat transfer model Freon-ll is selected as working fluid. The condensation heat transfer coefficient, the boiling heat flux the saturation pressure are meassured in this investigation. According to the experimental results, it is found that the electrical field can influence best transfer system. The boiling heat transfer is enhanced by the applied voltage, and the saturate vapor of working fluid is condensed on the high voltage electrode directly when the applied voltage is higher than 6kv. The experimental results have been discussed, and it is considered that the high electrical field strength change the thermal properties of working fluid.