Study On The Bactericidal Treatment Room With High Voltage Pulsed Electric Field

Traditional pasteurization could kill bacteria on appropriate temperature and heating preservation time, on the basis of Pathogen’s thermolability. With the increasing material and culture needs, non-thermal inactivation (Cold sterilization) becomes more and more important in the society. Out of all existing cold sterilization, pulsed electric field (PEF) sterilization is one of the most reliable ways to kill bacteria in a short time with a high efficiency. It has many advantages, such as the high bactericidal, little temperature rise and it also can keep the colour, nutritionist, and the taste of the food..There are some typical high-voltage pulses, such as exponential decay pulse, square wave pulses, sasser pulse and high-power electromagnetic pulses.The high-power electromagnetic pulses include:nuclear explosions electromagnetic pulse (NEMP), pulse generated by the non-nuclear electromagnetic pulse weapons, lightning electromagnetic pulse (LEMP), Electrostatic discharge (ESD) pulse. Electromagnetic pulse (EMP) is a transient electromagnetic phenomena. Seen from time domain, the rising edge of nanosecond pulse is very steep. Meanwhile the band-width of nanosecond pulse is very wide in frequency domain. Based on transmission line theory and pulse bactericidal mechanism, this paper designed two PEF process chamber to do the sterilization experiment.The chamber works with nuclear electromagnetic pulse field of sterilization and the specific work as follows:The paper introduced the PEF sterilization at home and abroad, described the components and the mechanism of the PEF, and also elaborated the factors of PEF sterilization. In order to avoid reflections during the pulse signal transmission, this paper introduced the computing method of characteristic impedance and the fundamental of impedance match.On the condition of field strength and characteristic impedance, this paper designed two PEF process chamber. The first one is coaxial, with non-inductive resistance as the load. The second one is using copper-bath as the water resistance. During the experience, we made the models according to actual sizes. With the HFSS and MAXWELL software, we analyzed the standing-wave and the field intensity distribution.After the analysis, we do different experiments at two PEF process chamber.The first experiment (water resistance) shows great effect on wave form because of the high equivalent capacity of the water resistance load. The max amplitude decreased, the fall time becomes longer.The second one is coaxial, with non-inductive resistance as the load. We first measured the pulsed voltage and pulse width, and then do the sterilization. At last, we also should measure the pulsed voltage, pulse width and the influence of holding period. The results show that, when the number and fall time of pulses were given, as the voltage increases, the sterilization efficiency gradually become larger. When given certain voltage and pulse fall time, the sterilization become larger with the increase of the number of pulses at first, when the pulse number reaches a certain level, the sterilization rates were stable. When the voltage and pulse number were given, change the pulse fall time is no use of the sterilization rate.