Hydrodynamics of regular packings formed from cellular inclined cylinders for heat- and mass-exchange processes

Abstract

Results are presented for investigation of the hydrodynamics of regular packings formed from cellular inclined cylinders for heat-and mass-exchange processes. Characteristics of the influence exerted by the angle of incline of the packing elements were investigated, and computational relationships for the coefficient of hydraulic resistance of the packings ascertained during the course of the study. Keywords: regular packing, heat and mass exchange, hydraulic resistance, mesh formed from polymeric material.Polymers have recently come into widespread use as a material for fabrication of packings in heat and mass exchangers. Polymers are acid and wear resistant, and durable [1,2]. Use of polymeric materials, including those in the form of a mesh, also provides for a reduction in the mass of the packing, lightening the load on the support elements of the structures in column vessels and cooling towers [3,4].This paper presents results of investigation of the hydrodynamics of regular packings formed from cellular inclined cylinders for heat-and mass-exchange processes. The present study is a continuation of tests conducted previously at the Moscow State University of Engineering Ecology (MGUIE) [5,6]. The objective of the study was to ascertain laws defining the influence exerted by geometric parameters on the specific resistance of dry and irrigated packings formed from various types of mesh.Tests were conducted on an experimental plant with a rectangular prototype unit having a cross section of 250 × 250 mm. The hydraulic resistance of the packing layer and the flow rate of air through the unit were recorded by two type-MMH micromanometers using a Pitot tube; the flow rate of water was determined with use of an RS-7 rotometer.The dry packing was tested in the air-velocity region w 0 = 0.8-3.8 m/sec in calculating the full section of the empty unit. Moreover, the Reynolds number Re g = w g d e ρ/μ (here, w g = w 0 /ε is the velocity of the gas through the apparatus with the packing, ε is the free volume, d e is the equivalent diameter of the packing, ρ is the density of the gas, and μ is the dynamic viscosity of the air) was varied from 6000 to 24000. The irrigated packing in the gas-liquid counterflow was tested at reflux densities q l = 8-16 m 3 /(m 2 ·h). The packing was constructed in the form of six layers consisting of cylinders 60 mm in diameter, which were mounted at an angle α to the vertical in the unit (Fig. 1). During the course of the experiment, the angle α was set at 5, 10, 15, 20, and 25°. Three types of mesh with cells having dimensions of 2 × 2, 3 × 3, and 4 × 4 mm in the active section were used as packing material. The design of the upper layer, which includes six centrifugal nozzles, permitted uniform irrigation of the packing. The packing was mounted on the support tray fabricated from a polymeric mesh with cell dimensions of 20 × 20 mm. The resistance of the mesh of the support tray was predetermined and calculated from the resistance of the packing.Geometric characteristics of the alternate d...

The use of industrial wastes from machine-building enterprises as packing materials for small-sized absorbers for gas emissions purification

“…The selection of well-known and the creation of new contact packing devices for technological mass transfer equipment is always associated with the need to evaluate their effectiveness for the conditions of a particular process. Work on improving mass transfer contact devices has been very active, and this has been the subject of numerous studies by many leading scientists [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. The main tasks that contact mass transfer devices are designed for are developing the inter phase surface and implementing the developed hydromechanical regimes providing mutual mixing and activation of diffusion processes between the contacting components of mass transfer processes.…”