According to Dalton's gas law, the pressure of a mixed gas is equal to the sum of the pressures of the various components that make up the gas, the performance of a vacuum pump must be influenced by the pressure of saturated water vapor. Especially if the water temperature is higher, at high vacuum the effect on pump performance is more significant. Since the performance of a liquid ring vacuum pump in the technical documents is obtained under the condition that the water temperature at the pump inlet is 15 C, when choosing a water ring vacuum pump, it is necessary to take into account the effect of the actual water temperature on the pump performance.
The effect of water temperature on the performance of a liquid ring vacuum pump can be calculated and illustrated. According to GB/T 13929 "water ring vacuum pump test method and water ring pressure compression test", the K1 water temperature influence coefficient on water ring vacuum pump performance can be calculated by the following formula. If the supply water temperature is 30 C, the saturation vapor pressure is 42.42 hPa. At an inlet pressure of 400 hPa, the water temperature coefficient K1 = 1.07, which means that when comparing performance at an inlet water temperature of 15 C, the real performance is reduced by 7%, if the inlet pressure is lower and the higher the water temperature, the greater the impact on performance. Therefore, we must lower the temperature of the water in the liquid ring vacuum pump. The flow rate of the working fluid also has some effect on the performance of the vacuum pump. If there is too much working fluid, this may not greatly affect the performance of the vacuum pump, but it will increase the power on the shaft. If there is too little working fluid, the gap will not seal fully, performance will decrease, and the water temperature will rise too quickly.
Thus, maintaining the correct amount of working fluid is also a key factor in ensuring the correct operation of the vacuum pump. The water supply pressure is usually from 0.06 MPa·g. up to 0.10 MPa g You can also determine the correct amount of water supply by the water temperature. Under normal operation, the temperature difference between the discharge temperature and the outlet water temperature is preferably 5 to 10C. If it is higher than 15C, the water supply amount is too small, and the water supply amount should be increased.
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