Heat transfer total condenser design

N,n = Minimum theoretical stages at total reflux Q = Heat transferred, Btu/hr U - Overall heat transfer coefficient, Btu/hrfP"F u = Vapor velocity, ft/sec U d = Velocity under downcomer, ft/sec VD(js = Downcomer design velocity, GPM/fL Vioad = Column vapor load factor W = Condensate rate, Ibs/hr Xhk = Mol fraction of heavy key component Xlk = Mol fraction of the light key component a, = Relative volatility of component i versus the heavy key component... 

TWO liquid phases. When a single liquid phase condenses, the liquid exerts it own vapor pressure. When two liquid phases are present, each exerts its own vapor pressure. The net effect will be a higher total vapor pressure at the same temperature conversely, at the column pressure, both components will condense at a lower temperature. If the condenser is designed to handle only a single liquid phase, an imex-pected appearance of the second liquid phase will lower the heat transfer. The author is familiar with one experience where as a result of an upstream energy-saving revamp, an eu omatics separation column received a lot more water in the feed. The water distilled up and formed a second liquid phase upon condensation. The condenser was not revamped and was unable to achieve its duty when the two phases... 

Calculation of the required condenser surface is not trivial. In contrast to the common applications where saturated vapors are condensed the permeate is a superheated vapor mixture. For design calculations the selection of appropriate heat-transfer coefficients has to consider the cooling to saturation conditions, the presence of noncondensable gases, and the partial condensation of the components along the respective dew lines. Total condensation of the more volatile components of the permeate vapor will often not be possible, but any losses of permeate vapor through the vacuum pump have to cope with the respective emission control regulations. An important factor is the solubility of the components of the permeate in the liquid phase. An additional condenser at the high-pressure side of the vacuum pump is a feasible option. 

These total condensers are designed on a heat transfer basis using the relationship ... 

A test with the NOKO facility has confirmed that the Emergency Condensers as proposed for the SWR 1000 from SIEMENS can transfer decay heat produced in the core region to an outside water pool. The capacity, however, is not high enough to cope with the total amount of decay heat immediately after scram. However, after some time - depending on the actual design - this heat transfer mode is effective. 

If the no-phase-change restriction does not rigorously apply, a simple design procedure can be formulated based on the results discussed in Section III, where it is shown that thermal equilibrium is quickly achieved in gas-liquid systems because of the large heat effects associated with evaporation or condensation. Although the total mass transfer between the phases may be small, it is not unrealistic to assume that the gas and liquid phases have the same temperature at each axial position. 

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