OBJECTIVES:Students will be able to:1. Understand energy waste due to improper filter sizes2. Properly size return air filters.LESSON / INFORMATION:All of the air which enters the HVAC system enters through the return air filter. The filter must be theoretically sized according to the cfm (cubic feet per minute) requirement of the system. A filter that is too small will cause a number of problems. The filter will clog very rapidly if undersized and reduce air flow. Air velocity also becomes critical with reduced size and dirt will pass through instead of staying in the filter. The dirt will eventually get to the blower wheel and reduce surface area or on the evaporator coil and restrict air flow. A filter and grill that are too small will vibrate and whistle, which can be annoying. The system is trying to draw in the designed air quantity and if the filter will not allow flow, air will be drawn in from any possible crack. Every system, no matter how air tight you construct it, will have small cracks through which dirty, warm air will enter the system as static pressure increases. A large surface area filter will negate the effect of these cracks by having a lower static pressure and lower air velocity.The recommended minimum filter surface area is 2.50 cubic feet per minute (cfm) per square inch of filter area.Example 1:2000 cfm ÷ 250 inches = 800 square inches or 20" X 40" filter grill.The maximum allowable filter velocity is 300 feet per minute (fpm) on disposable filters. The above example would yield 360 fpm and a disposable filter could not be used. For best results, use 2.00 cubic feet per minute per square inch of filter area.Example 2:2000 ÷ 200 inches = 1000 square inches of 40" X 24" filter. Usually two grills 20" X 25" each would be used.The second formula works in all residential applications. Using 2.00 cfm per square inch the velocity of air across the filter will not exceed 300 fpm in 1 through 5 ton units. In applications of limited space, the disposable filter may be located in the return duct. When using duct mounted filters, consult the manufacturer's literature on the return grill sizing to prevent noise and reduce restrictions.In residential applications, we find many types of air filters:Figure 1. Disposable Filter Figure 2. Washable Permanent Filter Figure 3. Media Type Filter Figure 4. Electronic Air Filter The Media type is more efficient than the disposable and the electronic type removes particles to .1 micron.ACTIVITY:Demonstrate effects of reduced filter area with a 1200 cfm blower connected to a 20" X 30" filter grill housing with a standard 20" X 30" disposable filter.1. Set up blower, measure and record motor RPM amp draw.2. Measure and record air velocity and volume.3. Block off surface area of filter grill with cardboard or comparable material - 20" X 20".Measure and record:A. Motor RPM ________B. Motor Amp Draw ________C. Air Velocity ________D. Air Volume ________E. Noise Level ________4. Block off the surface area as in step 3 to 20" X 15".Measure and record:A. Motor RPM _______B. Motor Amp Draw ________C. Air Velocity ________D. Air Volume ________E. Noise Level _________5. Block off the surface area as in step 3 to 20" X 10".Measure and record:A. Motor RPM _______B. Motor Amp Draw ________C. Air Velocity ________D. Air Volume ________E. Noise Level _________Comments or questions to: TechAsmt@LA.GOV
New serial number system independent of CINEMA 4D : license management and entry directly into X-Particles with no more need for serial number updates with new CINEMA 4D releases or having to add X-Particles to the MAXON license server.
Air sampling is used to detect aerosols (i.e., particles or microorganisms). Particulate sampling (i.e., total numbers and size range of particulates) is a practical method for evaluating the infection-control performance of the HVAC system, with an emphasis on filter efficiency in removing respirable particles (
2.1.1 Soil compositionWhen dry soil is crushed in the hand, it can be seen that it is composed of all kinds of particles of different sizes.Most of these particles originate from the degradation of rocks; they are called mineral particles. Some originate from residues of plants or animals (rotting leaves, pieces of bone, etc.), these are called organic particles (or organic matter). The soil particles seem to touch each other, but in reality have spaces in between. These spaces are called pores. When the soil is "dry", the pores are mainly filled with air. After irrigation or rainfall, the pores are mainly filled with water. Living material is found in the soil. It can be live roots as well as beetles, worms, larvae etc. They help to aerate the soil and thus create favourable growing conditions for the plant roots (Fig. 26).Fig. 26. The composition of the soil2.1.2 Soil profileIf a pit is dug in the soil, at least 1 m deep, various layers, different in colour and composition can be seen. These layers are called horizons. This succession of horizons is called the profile of the soil (Fig. 27).Fig. 27. The soil profileA very general and simplified soil profile can be described as follows:a. The plough layer (20 to 30 cm thick): is rich in organic matter and contains many live roots. This layer is subject to land preparation (e.g. ploughing, harrowing etc.) and often has a dark colour (brown to black).b. The deep plough layer: contains much less organic matter and live roots. This layer is hardly affected by normal land preparation activities. The colour is lighter, often grey, and sometimes mottled with yellowish or reddish spots.c. The subsoil layer: hardly any organic matter or live roots are to be found. This layer is not very important for plant growth as only a few roots will reach it.d. The parent rock layer: consists of rock, from the degradation of which the soil was formed. This rock is sometimes called parent material.The depth of the different layers varies widely: some layers may be missing altogether.2.1.3 Soil textureThe mineral particles of the soil differ widely in size and can be classified as follows:Name of the particlesSize limits in mmDistinguisable with naked eyegravellarger than 1obviouslysand1 to 0.5easilysilt0.5 to 0.002barelyclayless than 0.002impossibleThe amount of sand, silt and clay present in the soil determines the soil texture.In coarse textured soils: sand is predominant (sandy soils).In medium textured soils: silt is predominant (loamy soils).In fine textured soils: clay is predominant (clayey soils).In the field, soil texture can be determined by rubbing the soil between the fingers (see Fig. 28).Farmers often talk of light soil and heavy soil. A coarse-textured soil is light because it is easy to work, while a fine-textured soil is heavy because it is hard to work.Expression used by the farmerExpression used in literaturelightsandycoarsemediumloamymediumheavyclayeyfineThe texture of a soil is permanent, the farmer is unable to modify or change it.Fig. 28a. Coarse textured soil is gritty. Individual particules are loose and fall apart in the hand, even when moist.Fig. 28b. Medium textured soil feels very soft (like flour) when dry. It can be easily be pressed when wet and then feels silky.Fig. 28c. Fine textured soil sticks to the fingers when wet and can form a ball when pressed.2.1.4 Soil structureSoil structure refers to the grouping of soil particles (sand, silt, clay, organic matter and fertilizers) into porous compounds. These are called aggregates. Soil structure also refers to the arrangement of these aggregates separated by pores and cracks (Fig. 29).The basic types of aggregate arrangements are shown in Fig. 30, granular, blocky, prismatic, and massive structure.Fig. 29. The soil structureWhen present in the topsoil, a massive structure blocks the entrance of water; seed germination is difficult due to poor aeration. On the other hand, if the topsoil is granular, the water enters easily and the seed germination is better.In a prismatic structure, movement of the water in the soil is predominantly vertical and therefore the supply of water to the plant roots is usually poor.Unlike texture, soil structure is not permanent. By means of cultivation practices (ploughing, ridging, etc.), the farmer tries to obtain a granular topsoil structure for his fields.Fig. 30. Some examples of soil structures GRANULAR BLOCKY PRISMATIC MASSIVE 2.2 Entry of water into the soil 2.2.1 The infiltration process 2.2.2 Infiltration rate 2.2.3 Factors influencing the infiltration rate
FIGURE 12. Rock sample with microcracks (A) with estimated coordination number (CN) maps for four different-radius measuring windows. (B) Rw2R=1.5. (C) Rw2R=1.0. (D) Rw2R=0.9. (E) Rw2R=0.8.
Fluid catalytic cracking, or FCC, is the last step in the evolution of cat cracking processes-- also introduced in 1942, just like TCC or Thermafor Cat Cracking, during the Second World War in an effort to make high-octane number gasoline. Remember that high-octane number relates to high power as you can have higher compression ratios in the combustion engines.FCC really shows an excellent integration of the cracking reactor, an endothermic reactor, with the catalyst regenerator and exothermic reactor for very high thermal efficiency. FCC is now used universally in oil refineries throughout the world-- has replaced all the previous cat cracking processes.Now, in FCC, in the feed, that is gas oil preheated to about 300 degrees Fahrenheit-- is introduced into the reactor with steam. The riser part of the reactor where the hot catalyst particles-- as you see, the green line coming from the catalyst regenerator-- are full of dyes. The particles are full of dyes because they're smaller particles. They are full of dyes and flowing gases and vapors. So they have a huge surface area to meet the incoming feed at temperatures that are close to 1,000 degrees Fahrenheit.So cracking reactions on these very fine particles that are full of dyes and flowing with the reactants takes place in a very short space of time, something that could be measured with seconds. And the products are sent to a fractionator after going through a series of cyclones, obviously, to separate the small fluid dyes, the particles of the catalyst.In the fractionators, the products, as usual, are separated into gas, gasoline, light cycle oil, heavy cycle oil, and, finally, the heaviest fractions, decant oil.Remember that LCO is used in the US for making diesel fuel through hydrocracking and hydrogenation. And decant oil could be used as fuel oil or as feedstock for making carbon black or white coking to make needle coke for graphites, electrodes.Coming back to the reactors, the cat cracking reactor, the coked catalyst now, the end of the riser where this cracking reaction takes place, are sent through the regenerator. It's not fully coked on the surface, lost its activity. Through the red line, it's sent to the regenerator where air is introduced to burn off the coke.The temperatures in the regenerator could reach to 1,300 to 1,400 degrees Fahrenheit. You should remember that the catalysts now are much improved, as well. It may include zeolites that would take high temperatures and very controlled reactivities through pore size distribution and so forth.So the combustion products or flue gases from this catalyst regenerator could be sent to a CO boiler because the gas may contain significant amount of carbon monoxide, which could be burned to CO2 to provide additional heat or to generate additional heat.So the catalysts that are now regenerated are sent to the reactor to close the catalyst cycle through that green line, as you see, to meet the incoming feed. So our catalyst cycle is pretty much complete at this point.But note this excellent integration, thermal integration, of the catalyst regeneration, the exothermic process, with the cracking reactions where the catalysts that are heated in the regenerator are sent in a very effective manner to the reactor without much heat loss. So that is the ultimate, if you will, thermal efficiency of a process. And that's why FCC is now the universally accepted catalytic cracking process. 2b1af7f3a8