Irrigation uniform

C. Liquid Distributor (see Figures 4-9). According to Strigle, This is the most important column internal from a process standpoint. A liquid distributor is required at all locations in the tower where an external liquid stream is introduced. High-performance distributors provide a flow rate variation per irrigation point that is a maximum of 5% of the average flow. The geometric uniformity of... 

The number of irrigation or drip-points or entrance points per square foot of flat surface of the tower should be uniform for orifice, weir-type gravity, or pressure distributors, and need not exceed 10 points/ft [82]. This imiformity must not be disturbed by support rings for supporting the distributor itself. The distribution must include the area adjacent to the wall, and the design must not force more liquid at the wall where it contacts the packing. Uniformity of points of distribution to the packing surface is extremely important. The volume flow per point must be carefully calculated. 

Trial sites must be selected on the basis of uniformity (soil characteristics, areas of sunshine, etc.), and areas that are susceptible to erosion or areas where drift of chemicals from neighboring fields might occur should be avoided. Irrigation sources are supplied, preferably nearby. 

At the top of the packed bed a liquid distributor of suitable design provides for the uniform irrigation of the packing which is necessary for satisfactory operation. Four... 

Micropropagated raspberry is less tolerant to simazine, probably because of the shallow roots picking up more herbicide than the deeper rooting cuttings (Neal et al, 1990). When simazine was used in a New York study, weed control was excellent. However, with rainfall plus supplemental irrigation, there was less plant establishment and growth in herbicide-treated vines compared to mulched plants (Trinka and Pritts, 1992). It was determined that mulching provided a more uniform microclimate (moisture) than the plots with no weeds or cover. 

In collaboration with the University of Wageningen, magnetic resonance imaging (MRI) was used to visualize the film flow in the monoliths [15], As shown in Fig. 8.8, liquid (water) was fed onto a complete piece of monolith from which four channels then were prolonged for measurement. In Fig. 8.9, the liquid is represented as light areas in the corners of the four channels. Clearly, the channel walls are not uniformly irrigated. In the corners, the gas-liquid interface is shaped like an arc, whereas between the pockets, only a thin liquid film remains ( 70 pm). This retraction of the film into the corners can be attributed to the high surface tension of the liquid used (water). Additionally, the liquid pockets of one channel have different sizes, and this leads to channel scale maldistribution. 

The main variables that dictate the uniformity of catalyst irrigation are the liquid velocity, the particle diameter and the kinematic viscosity of the liquid Figure 8 gives the maximum allowable particle diameters for several reactor lengths as a function of the kinematic viscosity. 

Fig. 11. Condition for uniform irrigation in trickle flow. Maximum particle size as a function of liquid kinematic viscosity for different bed lengths and different space velocities.

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