Estimation of wetted surface area

The heat input into a liquid wet vessel depends upon the wetted area of the vessel. The following guidelines are used to estimate the wetted surface area  

Surge drums, knockout drums, process vessels Fractionating column 

Normal operating level up to the height of 7.62 m Normal liquid level at bottom plus liquid holdup from all trays — up to the height of 7.62 m Average inventory level up to the height of 7.62 m Up to the maximum horizontal diameter or up to the height of 7.62 m, whichever is greater 

Level of the reboiler must be included if the reboUer is an integrated part of the column 

A = surface area D = outer diameter of shell L = tube length 

---

Venting requirements due to fire depend upon the wetted surface area of the tank. The following methods are used to estimate the wetted surface area of the tank ... 

The wetted surface area of the 2 m3 reactor during two-phase relief has been estimated as 8.6 m2. This is the full surface area of the bottom and the sides of the reactor because, if two-phase relief occurs, this whole area will be wetted inside the reactor with liquid. The heat input rate from the fire is estimated as 252 kW l For a closed reactor containing 793 kg of material, and using the average, specific heat capacity of 2.25 kJ/kg K, the effective rate of temperature rise due to the fire is given by ... 

The silica release rate and flow-rate mass ratio of Figure 18 depend on estimations of the wetted surface area of reacting minerals and the mass of wetted soil. As discussed by Paces (1983), there is much uncertainty in estimating wetted surface areas of reacting minerals. In Figure 18 and Table 3, it was assumed that 40% of the surface area of soil was weatherable minerals the soil surface area was 0.5 m2 g 1 (except at Coweeta, where Velbel s (1985) procedure was used), the bulk density of the soil was 1.5 kg L-1, and the equivalent saturated water depth was 0.5 m (except at Coweeta and Cristallina, where it was taken to be 0.1 m). All of these parameters were measured at Bear Brook Watershed and applied to the other sites. 

S is the ratio of the surface area of the medium to its pore volume and stands for equivalent diameter of the pores. The hydraulic (mean) radius m is defined as the ratio of the average pore cross-sectional area to the average wet perimeter, in line with the concept of the equivalent loads (as explained in Section III). All the geometrical parameters from Eq. (19) can be estimated for particulars of the porous media. For example, in the case of aligned fibers, hydraulic radius and equivalent diameter can be expressed by ... 

The vessel.exe program has been developed to estimate the total and filled-liq-uid volumes and dry and wet surface areas for horizontal, vertical, and inclined (e.g., slug catcher) vessels. For horizontal and vertical vessels, the program also calculates the weight of the material and the hydro test weight. 

For vapor relief from columns (other than fire relief), the rate of vapor relief and the fluid properties must be determined by simulation at relieving pressure. The relieving will be 110% or 116%, depending on the requirement. For a fire case, the relief rate depends upon the latent heat and wetted surface area. The latent heat shall be estimated at 121% relieving pressure and for the average liquid composition within the column. 

For the shell side of a shell and tube heat exchanger, the wetted surface area is estimated as follows ... 

Fig. 6. Surface area of coals as estimated from (o) neon sorption at 25°C and (x) methanol heat of wetting.

To test for PKU disease, use four Phenistix strips, one for each urine sample. Immerse the test area of the strips into the urine samples and remove them immediately. Remove the excess urine by tapping the strips against a clean, dry surface. Read the color after 30 sec. of wetting, and match them against the color charts provided on the bottle. Record your estimated phenylpyruvate content negative or 0.015 to 0.1%. 

---