Is the temperature difference between the gas and liquid phases in the vacuum evaporation chamber large?
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In my laboratory, we conduct experiments in which an electric furnace is used to heat the mother liquor in a flask; the flask is connected to a condenser, which is in turn connected to a vacuum pump. Vacuum is created while heating, and when the vacuum level reaches 0.032 MPa, the mother liquor begins to evaporate. The temperature of the mother liquor is measured to be 113°C, while the temperature of the steam above the surface of the mother liquor is 110.2°C. However, in actual production, when the vacuum level reaches 0.032 MPa and the mother liquor starts to evaporate, the temperature of the mother liquor is still 113°C, but the temperature of the steam coming from above its surface is only 85°C. What is the reason for this? Theoretically, in vacuum evaporation, is there a difference in temperature between the gas and liquid phases in the evaporation chamber? Is that difference significant? I hope to receive your guidance; thank you!
What is the insulation performance of the equipment in actual production? Is there heat dissipation?
This post was last edited by symc on 2019-10-7 13:20: Your experiment question! It’s only the formality... If you want to obtain accurate results, you need to calculate how much the mother liquor in your flask has evaporated Then, based on this amount of evaporation, it is necessary to determine the size of the condenser required... If the evaporation rate of the mother liquor is high and the condenser is small, a very large initial temperature difference will occur! ——This is normal. And if the heat load on the condenser is high while the heat load for the evaporation of the mother liquor is low, you can draw the usual conclusion.
Thermal diffusion: Insulation performance: Experiments were conducted in the north during summer and winter, with the influence of environmental factors
I wonder whether, under ideal conditions – with environmental influences and heat losses excluded – there is a difference between the boiling point temperature in the evaporation chamber and the temperature of the secondary steam exiting the chamber during vacuum evaporation, and to what extent that difference is. The temperature of the secondary steam is certainly lower than the boiling point temperature, but I’m not sure by how much
The vapor that emerges from the mother liquor is superheated steam; the vaporization rate in the laboratory may be higher than that in actual production. Moreover, the flask acts as a heat source, which can cause the steam temperature to exceed the temperature of the liquid. In actual production, the vaporization rate is lower, heat dissipation is more significant, and the steam temperature can drop to the dew point temperature. The specific values need to be determined based on clear process conditions
:It’s definitely not a problem related to the environment; it’s most likely related to your equipment. First, there are your two temperature measurement points, and then there’s the issue of whether there is any change in diameter in the connection between those two points, which could lead to uneven pressure (similar to what happens when compressed gas expands and its temperature drops), resulting in significant variations in the boiling points. This is also somewhat related to the efficiency of the vacuum pump and the condenser