a) Effective volume flow Volume flow at the inlet of the adsorber has to be converted on the basis of reference values to obtain the effective volume flow Ve . 
Formula 7.2.1.1 b) Operating volume flow Based on effective volume flow Ve and minimum operating pressure po, maximum operating flow Vo is calculated. 
Formula 7.2.1.2 c) Operating volume per cycleAdsorber design is also significantly influenced through the operating volume per unit of time. Operating volume Vocper cycle is established in accordance with 
Formula 7.2.1.3 d) Moisture load per cycle An important parameter for establishing dryer size arises from the moisture load per cycle. Humidity content h, referred to inlet temperature Ti , can be read from Diagram 7.2.1.1 (h/1000 = kg/m3) and inserted into Formula 7.2.1.4. Multiplied by the operating volume per cycle Voc , the moisture load per cycle hc is determined. 
Formula 7.2.1.4 
Diagram 7.2.1.1 e) Load factor The load factor Kl for the design calculation of adsorption dryers with heatless regeneration should be smaller than 0.5 kgH2O/kgdr , depending on the type of desiccant utilised, as the danger of oversaturation when loading otherwise arises. For a reliable and safe design specification, for adsorption drying of compressed air, the loading factor referred to the cycle is : Kl < 0.5 kgH2O/kgdrf) Quantity of drying material (desiccant) The quantity of mdr per adsorber depends on the maximum moisture loading and the reliable determination of the load factor Kl The quantity of desiccant per adsorber should always be established when comparing adsorption dryers. 
Formula 7.2.1.5 g) Adsorber volume After establishing the quantity of desiccant mdr , the adsorber volume Vdr is determined. The packed density (dr of commercially available drying media (see Section 6.0) varies in its effect on the adsorber volume with the type of desiccant utilised. For adsorption dryers with heatless regeneration, molecular sieves are frequently used and these have a packed density in line with table 6.1.1. 
Formula 7.2.1.6 h) Flow velocity The effective flow velocity we for air can be obtained from diagram 7.2.1.2 in relation to operating pressure po . The value of flow velocity read from the diagram should not be exceeded by more than 25% in the unfilled adsorber. At high flow velocity (see Section 5.2), the danger arises that the drying medium in the adsorber bed is agitated and thus subjected to strong mechanical strain or even damage. Alternatively, at low flow velocity, an undesirable laminar flow can lead to channelling and thus preperential flow through the adsorber.
Diagram 7.2.1.1 i) Adsorber cross sectioned surface area Using the operating volume flow Vo and the effective flow velocity we from Diagram 7.2.1.2, the adsorber cross sectioned surface area Adr is calculated, taking units into account and using the following formula : 
Formula 7.2.1.7 With the adsorber surface, the adsorber diameter ddr (m) is also established. It is rarely necessary to correct these values. j) Filling height The geometric filling height Fh of adsorbers is determined from the already calculated values of the adsorber volume Vdr and the adsorber surface Adr , in accordance with Formula 7.2.1.8. 
Formula 7.2.1.8 k) Dwell time The quality of the compressed air to be dried depends on a theoretically sufficient dwell time td . Provided that the minimum dwell time is adhered to, the required pressure dewpoint Pdp is achieved easily in the course of operation. Dwell time td is obtained from Formula 7.2.1.9 and Diagram 7.2.1.3. If the dwell time is insufficient, the adsorber surface Adr and filling height Fh have to be re-determined. If the required minimum dwell time is not adhered to, the reliable achievement of the pressure dewpoint throughout operating life becomes suspect. 
Formula 7.2.1.9 For a certain pressure dewpoint of Pdp-40°C, the dwell time should on no account fall belowt of td = 4.5 s. Deviating pressure dewpoints with the corresponding dwell times can be obtained from Diagram 7.2.1.3 and should be taken as guide line values. Because of the dwell time in the adsorber, the adsorption dryer must be given larger dimensions for lower pressure dew points, compared to a dryer design from which a pressure dewpoint of lower quality would be considered sufficient. The effect of pressure dewpoint on dryer size is frequently underestimated in practice. Targeting a specific pressure dewpoint Pdp must, therefore, be based on the realistic requirement and not on the possible maximum performance limit of the adsorption dryer. The overriding aim is always the determination of the most economical adsorber size. 
Diagram 7.2.1.3 l) Pressure loss In order to obtain the theoretical pressure loss of the adsorption dryer between the inlet and outlet the basis of theory, far reaching and complicated calculations are necessary (see Formula 7.2.1.13), as the air flow through the adsorption dryer is complex, the pressure loss has to be established separately for each part. The sum of the individual pressure losses results in the overall pressure loss. 
Diagram 7.2.1.4 Diagram 7.2.1.4 helps to obtain the pressure loss in the adsorber bed. The relevant flow velocity we from Diagram 7.2.1.2 has to be utilised in order to determine the differential pressure. Diagram 7.2.1.4 presents pressure losses as a function of operating pressure and at differing flow velocities through the adsorber, referred to 1 m of filling height. To determine the pressure loss, the value established from the diagram has to be multiplied by the filling height Fh obtained.
