The impact factors of the heat exchange
The heat transfer area of the condenser must be sufficient, otherwise it is difficult for the secondary steam entering the condenser to be completely cooled to increase the evaporation temperature, thereby reducing the production capacity of the tubular condenser.
Here, in addition to the heat transfer coefficient of the condenser should be selected properly, some factors that directly affect the heat transfer effect when calculating the heat transfer area of the condenser are not negligible.
3.1, the effect of the heat released by the condensate on the condenser effect
The condensed water in the shell side of the multi-effect evaporation equipment is generally discharged from the condenser together with the condensed water in the shell side of the condenser (this is not only simple in structure, but also mainly energy saving). Since the condensed water temperature in the shell side of the effect body is higher than the shell side temperature of the condenser, the degree of vacuum is high, and when the condensed water enters the shell side of the condenser, the condensed water releases a certain amount of heat due to self-evaporation. Therefore, this part of the heat should be included in the calculation when calculating the heat transfer area of ‹the condenser.
3.2. Effect of steam extracted from various non-condensable ports on the condenser
The multi-effect evaporation device generally has two upper and lower non-condensing air ports for each shell side to extract non-condensable gas in the shell side. The upper and lower condenser ports are directly connected to the inlet of the condenser. Each effect body takes steam from the shell side, and the material is taken away from the tube. It is often extracted from the non-condensable gas interface and a certain amount of heating steam is taken out. This is because the theoretical heating process is based on the heat balance. There is no remaining heat in the shell side. In fact, each effect can be seen as a condenser heating steam can not be absolutely no surplus, because heat loss should also be considered in the calculation process.
3.3, the influence of material preheater on the condenser
The temperature of the material before entering the evaporation equipment is relatively low, and it needs to be preheated step by step to reach the temperature above the boiling point or boiling point. For materials with lower temperature, it is generally divided into four levels for preheating. The preheating on top of the final effect separator provides a coiled material preheater for the first stage of preheating. The preheater preheats the material with secondary steam that is not produced. The other three stages of preheating were completed in three shells of the shell. Therefore, this part of the heat should be subtracted when calculating the heat transfer area of the condenser.