GRAPHICAL SOLUTION FOR SEEKING THE OPTIMUM SHAPE OF ADSORPTION ISOTHERM IN HONEYCOMB ROTOR TSA DEHUMIDIFIERS

摘要

When the cycle time is selected properly in a well-designed dehumidifier operated with TSA, each step ofadsorption/desorption can be divided into two different time zones, i.e. a transition stage appearing just afterswitching the step and a subsequent thermal equilibrium stage. The thermal equilibrium stage was analyzedextensively in terms of a short cycle time approximation and the HETP(height equivalent to a theoreticalplate) concept was applied in an analogy to the conventional countercurrent membrane separator. A modifiedhumidity chart in terms of the relative humidity? Φ against the absolute humidity x with the constant enthalpyline h is prepared to show the air conditions in the thermal equilibrium stage. The number of theoretical platesand the humidity change flx in each theoretical plate is sought graphically by the conventional stage-wiseoperation between the constant enthalpy lines of adsorption and desorption steps. After some simplification,the bed height of each theoretical plate is given by the reciprocal of average gradient of isotherm mn=flqn/flxnweighted with a ratio γn=flxn/flxn+1 of the humidity change to that in the next plate. The optimum shape ofisotherm to minimize the total bed height can be sought by increasing the gradient of isotherm mn in the nextplate by a factor of square root of the ratio of humidity change γn. A graphical method was developed to getsuch an optimal adsorption isotherm and the proposed optimization policy was verified by a samplecalculation of the dehumidification performance.