Airvate Blog

  Introduction The performances of all the hoods in the whole system normally decide the success of industrial ventilation and dust collection systems from the point of a system owner’s view. The appropriate hood design and its needed airflow rate require the application of good ventilation practice, mastery of the technical knowledge and the ability and patience to do the mathematical calculations. When more than one hood is connected to one ventilation system, the design engineer has to assure that each hood can and will receive the volume of airflow equal or above its designed value and the whole system operates with the minimum possible airflow rate to save energy. This task is termed air balancing of the system or duct balancing. Unbalanced systems cause problems On the contrary, examine the case where one or more hoods are unable to receive desired volume of airflow from an unbalanced ventilation system. It is not uncommon that many hoods are receiving airflow volumes...

  Introduction Most baghouse users are confused why their baghouses suffer moisture condensation problems in winter. This blog post tabulates the dew-point temperatures of the airflows with different Relative Humidity (RH) at three different airflow temperatures of 68 o F, 120 o F and 250 o F to show why moisture problems in baghouses or cartridge collectors occur   in winter. Definitions of dew-point and Relative Humidity Dew-poin t is defined as the temperature at which condensation begins when the air is cooled at constant pressure. Relative Humidity (RH) expresses the moisture content of air as a percent of what it can hold when the air is saturated. The temperature of the airflow from a process will likely remain fairly constant and warm year round. However, a temperature differential (approximately 15 o F or more) between the dust collection point and the dust collector may indicate a potential condensation risk. Condensation in a baghouse causes problems When wate...

The pressure loss of a cyclone separator is divided into three main contributions from: the cyclone inlet, cyclone body, and vortex finder (gas outlet). The gas swirl inside the cyclone body is very useful for particle separation, but as this swirl exits the cyclone through the gas outlet, the rotational energy which is stored within is actually lost. This is the main source of the pressure loss of a cyclone separator. A lot of studies have been conducted trying to reduce the pressure loss caused by this rotational energy in the exiting gas flow through modifications on the gas outlet: Modify the length and diameter, Change its shape from cylinder-shape to cone-shape. These modifications can indeed reduce the pressure loss, but cannot be done to existing cyclones inexpensively. Some studies looked outside of a cyclone separator. Here are two examples. In one study, in order to minimize the cyclone’s pressure loss, a pressure recovery type diffuser known as a radial diffuse...

  Outline of this blog post Introduction   Comparison of Standard and Oversized cyclone performances (calculations by Airvate) Recommended applications of oversized cyclone Summary and conclusions Introduction Cyclone separators are widely used in many industrial applications where it is necessary to remove the dust or particles from gasses. These devices are simple with no moving parts and are easy to maintain. Although the construction of these devices is simple, the physics governing the flow process in them is complex. Normally cyclone designers follow two procedures to size a cyclone. Classical Cyclone Design process, and Texas A&M Cyclone Design method The results from these procedures are usually called standard cyclones, while an oversized cyclone is the one from the same family but with a bigger body diameter and, consequently, with a lower inlet velocity at the same air flowrate. Normally, an oversized cyclone can have a lower pressure loss at t...

  Introduction Cyclone separators have been applied in industrial fields for over a century to separate particles from gas streams. They have an inherent simplicity of design that usually encompasses no moving parts with the ability to collect fine particulates. Current designs of industrial high-efficiency cyclones can provide collection efficiency of 90 percent and higher for particles with diameters as small as 2 microns with specific gravity of 1. The inlet flow features used in design are the mean velocity and mixed mean dust concentration at the inlet, and the type of inlet. Based on these assumptions, flow patterns inside of a cyclone and its performance (pressure loss and grade collection efficiency) are developed and calculated. However, all design procedures appear to treat the cyclone as a device which operates independently from the flow configuration upstream. In particular, for a cyclone collecting dust from a gas flow, the orientation of elbows in the inlet duct...

  Introduction Particle size distribution data of a material to be collected is very important for the selection and sizing of a dust collector. If a population of particles is represented by a single number (or mean), there can be many different measures of mean sizes (or central tendency): arithmetic, geometric, quadratic, cubic, biquadratic, and harmonic to name just a few, each appropriate to specific uses. The mean particle size is rarely quoted in isolation: it is usually related to some application and used as a single number to represent the full size distribution. It represents the distribution by some property which is vital to the application or process under study; if two size distributions have the same mean, the two materials are likely to behave in the process in the same way. The arithmetic mean The arithmetic mean is the measure of central tendency most widely used in general statistics, and is essential to a few procedures (such as defining a normal prob...