Introduction to gas pressure and heat leakage at low temperature of vacuum valve

Calculating the partial pressure of hydrogen in the interlayer according to the volume percentage of the hydrogen component of the interlayer at normal temperature, and then calculating the specific volume of hydrogen in the interlayer according to the partial pressure, and the specific volume of hydrogen in the interlayer at the normal temperature and the temperature of the liquid oxygen is the same, and then Based on the condition that the specific volume of hydrogen is constant, the pressure of hydrogen in the interlayer at the liquid oxygen temperature is calculated. Because only hydrogen is in the gas state in the interlayer at this time, the pressure of hydrogen is the pressure of the vacuum valve interlayer under the liquid oxygen temperature.

Then, according to the pressure and structure size of the vacuum valve interlayer under the liquid oxygen temperature, the solid heat conduction, radiation heat transfer and convective heat transfer of the vacuum valve are calculated, and the heat exchange capacity of the vacuum valve under different initial vacuum degrees is finally obtained. .

When the vacuum valve interlayer is at a temperature of 0.1 Pa or less, the heat loss caused by the convective heat transfer of the residual gas is in the same order of magnitude as the heat conduction and the radiant heat. When the vacuum valve is pumped to 0.01 Pa, the heat loss caused by the gas convection heat transfer is only It accounts for less than 10% of the total heat loss. At this time, the heat loss caused by the radiation becomes the main factor of the vacuum valve leakage heat. The vacuum is continuously pumped, and the total heat leakage of the vacuum valve is hardly reduced, so when the vacuum interlayer is pumped to 0.01 Pa. Continued vacuuming has little improvement on the thermal insulation performance of the valve. The hydrogen content of the interlayer has an effect on the total heat leakage of the vacuum valve. With the increase of the hydrogen content, the leakage heat of the vacuum valve at low temperature increases, and the vacuum valve interlayer is at normal temperature. When the pressure is above 1 Pa, the total heat leakage of the vacuum tube is basically proportional to the hydrogen content. When the vacuum valve interlayer is at a temperature of 0.1 Pa or less, the total leakage heat of the vacuum valve has little to do with the hydrogen content.