Introduction Air Flow System Performance and Energy Relationships Grain depth vs. fuel efficiency Grain depth vs. air flow Air flow resistance vs. air velocity Grain depth vs. static pressure Static pressure vs. fan type Fan Performance Data Packing factor Fan efficiency Determining specific fan performance Air flow guidelines Using the Bin Drying Performance Tables Dryeration and Bin Cooling Performance Table and Guidelines Using the performance table Estimating required horsepower and surface area Plotting Air Flow System Performance Factors Affecting Fan Performance Drying capacity vs. grain depth Fines and air flow uniformity Unusual fan horsepower ratings Bin Drying Air Flow Rate Performance Tables Crop-Fan-Match Computer Program Input Form
The sizing and application of fans are important in determining how much time is needed to dry and cool grain, what these jobs will cost and, in the final analysis, how much energy you will use. The less time involved in drying and cooling, the less your energy requirement will be. This, of course, will be reflected in a lower dollar cost for fan operation.
This publication presents data and tables for determining the air flow, system performance and energy relationships in bin drying and cooling. This will help you (1) to select the fan(s) for your particular application, and (2) through the use of example problems, to calculate the type and size of fans needed for your own grain facility.
From the information presented here, you should be able to answer such questions as:
The data presented cover fans that range in air flow delivery capacity from 0.33 to 10.0 or more cubic feet per minute per bushel (cfm/bu.) for drying and cooling shelled yellow corn and soybeans. The data are applicable to fans for (1) dryeration or simple cooling, using air flow rates in the range of 0.5 to 1.0 cfm/bu., and (2) bin drying systems normally operating in the range of 1.0 to 10.0 cfm/bu. (No data are included for the air flow range normally used in aeration--typically 0.1 to 0.5 cfm/bu. for farm installations--and as low as 1/50th cfm/bu. for some elevator facilities.)
It is important to understand the relationship between grain depth and air flow resistance, velocity and static pressure conditions that occur in a bin. These relationships, in turn, have a marked effect on proper drying performance. If we understand the principles that make for efficient grain drying, we can best select the proper fan needed for operation--and thus conserve energy.
A common error in operating bin dryers is to place too much grain in the bin. This is especially true in bin drying procedures that use partial fills but can occur in full-bin drying also.
All bin drying processes are energy efficient for bed depths 2 1/2 feet and above, in terms of using the heat applied to the drying air. Fuel efficiency does not change much as the bed depth increases above the minimum, but air flow efficiency does. Proper fan selection and application are prime contributors to overall dryer efficiency.
A common misconception among users of bin dryers is that air flow resistance through a bed of grain is independent of air velocity. Indeed it is not. Consider this: If you have 1000 bushels of grain to dry, there is a very great difference between drying it "1000 bushels wide and one bushel deep" and drying it "one bushel wide and 1000 bushels deep!"
The wider and thinner grain can be spread out, the less fan capacity-required to dry it in a given period of time. This principle is illustrated in Figure 1. The column of grain in the center of the bin has a cross-sectional area of exactly 1.25 square feet (sq. ft.). Each foot of column height contains one bushel (one bushel equals 1.25 cubic feet).
Assume that an air flow rate of 2 cfm/bu. is applied to the bin, flowing upward through the column of grain. A 12-foot depth, then, requires 24 cfm (2 cfm/bu. x 12 bu.). The air flow entering the column has a velocity of 24 cfm/1.25 sq. ft. of floor area or 19.2 feet per minute (fpm).
Adding 4 feet of grain and maintaining the same 2 cfm/bu. air flow level requires a velocity of 25.6 fpm (32 cfm ÷ 1.25 sq. ft.). Adding another 4 feet of grain and maintaining the same 2 cfm/bu. air flow level requires 32 fpm (40 cfm ÷ 1.25 sq. ft.).
These grain depth/air flow relationships and their effect on horsepower are seen in Table 1. The table shows the fan horsepower required to deliver air flow through 10-, 12-, 16- and 20-foot depths of grain in a 30-foot diameter grain bin.
Power needed to deliver air flow thru grain depth of-- Air flow ------------------------------------------------------------- rate 10 feet 12 feet 16 feet 20 feet -------------------------------------------------------------------------- cfm/bu 1.0 --- 2.5 hp 6.7 hp 14.2 hp 2.0 7.1 hp 13.2 hp 36.2 hp 80.6 hp (16.0 cfm.sq ft) (19.2 cfm/sq ft) (25.6 cfm/sq ft) (32.0 cfm/sq ft) 3.0 --- 36.8 hp 103.5 hp ---- ------------------------------------------------------------------------------
Note how much the horsepower has to increase to sustain a 2 cfm/bu. air flow delivery as the grain depth increases. Doubling the depth from 10 to 20 feet requires over 10 times more horsepower! Also notice that holding the grain depth constant at 16 feet and doubling the air flow from 1 to 2 cfm/bu. increases the fan horsepower required by more than 5 times,
In neither case does the bin diameter or amount of open space between the kernels change. But in both cases, the air flow rate per square foot or bin floor area doubles. This means the air velocity has to double.
These relationships suggest two rules of thumb for sizing fans for drying systems: (1) doubling the grain depth at the same cfm/bu. air flow rate requires 10 times more horsepower; and (2) doubling the cfm/bu. air flow rate on the same depth of grain requires 5 times more horsepower.
Resistance to air flow is closely related to air bvelocity. Air flow resistance increases exponentially (increases at an increasing rate) as velocity increases. Doubling fan size from 10 to 20 horsepower (hp), for example, does not double the air volume. To double the air volume, the power must be increased from 10 to over 50 hp!
It makes little difference what brand or type of fan you use within the range of correct application for that fan. Although there are small differences in the performance of competing manufacturers' fans of the same general horsepower and size, their overall performance will be similar to the generalized data included in this publication.
Static pressure is the force required to overcome the resistance to air flow through grain and is usually expressed in inches of water column. It is also the measure used to rate a fan's performance under load conditions such as drying, cooling and aerating grain.
Static pressure is measured with a simple instrument known as a manometer (Figure 2), which is connected to the air plenum of a grain bin (air space below the false floor). An operating fan creates a pressure in the plenum great enough to push air up through the grain. This pressure also pushes on the open end of the manometer tube, causing the fluid in the manometer to move down one leg of the U-shaped tube and up the other. The difference in the level of the two columns (measured in inches of water) is the static pressure supplied by the fan.
The easier the air moves through the grain, the lower the static pressure. Thus, as a grain bin is filled with the fan "on," air flow is restricted and the static pressure increases. Increasing the air flow rate for a given depth of grain will increase the static pressure rapidly.
This relationship of static pressure and grain depth is presented graphically in Figure 3. To use the graph, follow the 16-foot depth line from the bottom of the graph, projecting upward to intersect the 1 and 2 cfm/bu. curves. Project these intercepts across to the static pressure scale on the left side of the graph. You will read approximately 2.4 and 6.4 inches of water column static pressure.
As you see, static pressure nearly triples when the air flow doubles. Pressure values for other combinations of fill depths and air flow levels can be estimated similarly.
Table 2 compares typical air performance data for a vane-axial fan and a centrifugal fan, each with a 10 hp motor. Air flow capabilities of the two types of fan differ significantly above and below the equal-performance point, which is about 4.0-4.5 inches of static pressure.
Air flow at static pressures of-- Type of fan ------------------------------------------------------------------------------ fan diameter 1.0" 1.5" 2.0" 2.5" 3.0" 3.5" 4.0" 4.5" 5.0" 5.5" 6.0" --------------------------------------------------------------------------------------------------- inches cubic feet per minute Vane axial 28 19,000 18,100 17,000 16,200 14,900 13,800 12,700 -- 9,400 -- -- Centrifugal 24 13,200 __ 12,700 -- 12,100 -- 11,300 -- 9,000 -- 8,500 -----------------------------------------------------------------------------------------------------
Vane-axial fans (Figure 4a) supply more cfm per horsepower at static pressures below 4.0-4.5 inches of water than centrifugal units. For this reason, these fans are generally better adapted to shallow-depth bin drying systems, such as batch-in-bin and continuous-in-bin systems, and to deep bin drying up to 20-foot depths requiring 1 cfm/bu. air flow or less. They are generally lower in initial cost, but operate at a higher noise level than centrifugal fans.
Centrifugal fans (Figure 4b) supply more cfm per horsepower at static pressures above 4.0-4.5 inches of water than vane-axial fans. They are especially advantageous when the application requires relatively high air volumes through deep grain levels (12-20 feet), and where low noise is important.
The tables and charts in this publication can help you estimate fan performance for bin drying or cooling. The data, although based on shelled yellow-dent corn, are also generally applicable to soybeans. Fan performance is based on a packing factor of 1.5 times that of clean shelled corn and an installed fan efficiency typical of commercial fans.
Packing factor is an index or ratio of the air flow resistance of a given grain depth to the resistance of the same grain when cleaned and piled in a loose fill. Loose fill occurs when grain is introduced into a bin at nearly zero velocity (without dropping), flowing into a cone-shaped pile. The descending grain then rolls or slides slowly down the coned grain surface.
In contrast, the grain in your bins usually has greater resistance to air flow than loose-fill grain. This is because it contains `fines,' is often dropped some distance onto the pile or is thrown by a distributor to the grain surface. As grain is distributed from above onto a surface of accumulated grain, the impact of the dropping, skipping kernels agitates the surface of the grain already in place. This agitation tends to orient the grain kernels into tightly-compacted positions, and causes fines to sift into the open spaces between kernels. The result is a "compacted fill."
The amount and the distribution of fines in grain for drying or aeration are very important. A high level of fines sharply increases the grain resistance to air flow. And the uneven distribution of fines prevents uniform air flow through various sections of the grain mass.
A packing factor is usually applied to grain in designing air flow systems in order to compensate for normal packed fill, fines deposit and air duct losses. A packing factor of 1.5 is a good design value for shelled corn and assumes a 50 percent increase in overall air flow resistance compared to loose fill.
Fan efficiency for crop-drying and aeration fans will typically range from a high of 55-60 percent down to 40 percent. The installed efficiency depends on: (1) the quality of the fan and (2) the static pressure of the load in relation to the fan's performance curve. If the load very nearly matches the high performance range of the fan's output curve, the installed fan efficiency will be high. Conversely, if the fan output curve and load characteristics match poorly, the installed fan performance may be low.
The fan performance data in this publication are based on fan curves for each horsepower size, derived by averaging the data from a number of commercial fans. These fans, when applied correctly, will normally operate in an efficiency range of 50-60 percent.
In selecting or evaluating fans for grain drying and bin cooling systems, the guidelines in Table 3 may be used.
Rate max. and min. or Recommended System grain moisture level air flow rate ------------------------------------------------------------------ Dryeration & bin cooling Minimum 0.5 cfm/bu. Good design 0.75 cfm/bu. Maximum 1.0 cfm/bu. ------------------------------------------------------------------ Deep bed bin drying* Corn 20-22% moisture 1.0 cfm/bu. 22-24% moisture 2.0 cfm/bu. 24-26% moisture 3.0 cfm/bu. ---------------------------------------------------------------- Soybeans 17% moisture 1.0 cfm/bu. 19% moisture 2.0 cfm/bu. 21% moisture 3.0 cfm/bu. ------------------------------------------------------------------- * 12-16 feet deep preferred, 20 feet maximum recommended.
The air flow rates listed for dryeration and bin cooling are adequate. But the question is, how fast do you wish to cool the grain? At 0.5 cfm/bu. air flow rate, the cooling time will be roughly 10-15 hours of fan operation. A 1.0 cfm/bu. rate will cut this time roughly in half-to 6-8 hours.
Dryeration air flow rates should not exceed the maximum recommended design level of 1.0 cfm/bu. to avoid exhausting the warm air from the corn before it can pick up a full load of moisture. The air flow rate is not critical during bin cooling if there is no heat-soak or tempering period prior to cooling. But grain that is bin-cooled immediately (with the higher air flow rates used for bin drying) could suffer a reduction in quality.
The air flow rates listed for corn and soybean drying are only for deep-bed bin drying systems. Partial-fill systems using batch-in-bin or continuous-in-bin methods run at much higher air flow and drying rates.
This publication provides air flow rate performance tables for bin drying with selected tan sizes and grain depths in bins 14, 18, 21, 24, 27, 30, 33, 36, 40, 42 and 48 feet in diameter (Tables 6-16). For purposes of illustration here, Table 4 (repeated later as Table 11) presents the performance data for a 30-foot bin.
In the table, grain depth and corresponding bushel volume are shown across the top of the columns, while fan horsepower is arranged down the left-most column. The data in the body of the table are air flow rates in cfm/bu. All grain fills are assumed to be level (not peaked).
Now, let's apply this example table to several typical, practical situations:
How do I choose fan horsepower for an existing or new bin?
Assume that you wish to dry 16 feet of shelled corn in a 30-foot diameter bin at a 1.5 cfm/bu. air flow rate. Enter Table 4 at the 16-foot depth heading at the top of the chart. Follow down the air flow values until you find one of at least 1.5 cfm/bu. (1.55 cfm/bu.). Then move left to the first column and read the required horsepower (15).
Air flow rate needed for a grain depth (and corresponding bushel volume) of-- ---------------------------------------------------------------------------------------- Fan 2 ft. 4 ft. 6 ft. 8 ft. 10 ft. 12 ft. 14 ft. 16 ft. 18 ft. 20 ft. 22 ft. 24 ft. hp (1131) (2262) (3393) (4524) (5655) (6786) (7917) (9048) (10179) (11310) (12441) (13572) -------------------------------------------------------------------------------------------------- cfm/bushel ** 0.33 1.38 .68 .45 .34 .27 .22 .19 .16 .14 .13 .12 .11 0.5 1.80 .89 .59 .44 .35 .29 .25 .21 .19 .17 .15 .14 0.75 1.94 .97 .64 .48 .38 .32 .27 .24 .21 .19 .17 .16 1.0 2.58 1.29 .85 .64 .51 .42 .36 .31 .28 .25 .22 .20 1.5 3.75 1.86 1.23 .92 .73 .60 .51 .44 .39 .35 .31 .28 2.0 4.58 2.25 1.48 1.09 .86 .70 .60 .51 .45 .40 .36 .32 3.0 5.83 2.89 1.90 1.41 1.11 .92 .77 .66 .58 .51 .45 .41 4.0 7.31 3.62 2.37 1.74 1.36 1.10 .92 .78 .68 .59 .53 .47 5.0 9.43 4.63 3.00 2.18 1.69 1.36 1.13 .96 .83 .72 .64 .57 7.5 11.39 5.54 3.57 2.58 1.99 1.60 1.33 1.12 .97 .85 .75 .66 10.0 13.51 6.58 4.23 3.02 2.32 1.86 1.53 1.28 1.10 .96 .84 .75 12.5 15.43 7.37 4.71 3.36 2.56 2.04 1.67 1.39 1.19 1.04 .92 .81 15.0 19.76 9.18 5.64 3.92 2.93 2.30 1.86 1.55 1.32 1.14 .99 .88 20.0 22.46 10.20 6.25 4.30 3.18 2.46 1.99 1.65 1.39 1.20 1.05 .93 25.0 25.93 11.31 6.77 4.66 3.44 2.65 2.12 1.76 1.49 1.27 1.10 .97 ---------------- 30.0 29.53 12.66 7.45 5.02 3.68 2.86 2.28 1.87 1.57 1.34 | 1.18 1.06 ------------------------ 40.0 33.00 13.78 7.97 5.33 3.89 2.99 2.38 | 2.04 1.63 1.56 1.39 1.25 50.0 39.39 15.57 8.92 5.87 4.26 3.27 2.58 | 2.21 1.92 1.70 1.52 1.36 -------------------------------------------------------------------------------------------------- * Fan performance based on an average of a number of commercial fans for each hp. Packing factor assumes 1.5 x Shedd's data for clean, loose-filled grain (10.0). See reference section for source details. **Cfm values below stepped line are centrifugal fans; above line are van axial designs. Change normally occurs between 4 and 5 inches static pressure.
How do I determine the air flow with an existing fan and bin combination?
Assume that you have a 10-hp fan and a 12-foot grain depth. Enter the 10-hp row on the left column of Table 4. Follow this row to the right until you come to the column headed by a 12-foot depth, and read the estimated fan air delivery (1.86 cfm/bu.).
Should I have a vane-axial or centrifugal fan for the above bin reference?
Referring to Figure 3, enter the 12-foot grain depth line (along the bottom of the graph), and follow it upward till it intersects with an air flow curve that would correspond to 1.86 cfm/bu. (estimated point between the 1.5 and 2.0 cfm/bu. curves). Follow the intersect point horizontally to the left margin, and read the static pressure (2.8 inches).
You should choose a vane-axial fan because the static pressure is below 4.0-4.5 inches of water. The fan should deliver at least 12,622 cfm at 2.8 inches static pressure (1.86 cfm x 6786 bu., as listed for a 12-foot depth in Table 4).
How will a change in grain depth affect the air delivery of my existing fan?
Again assuming a 10-hp fan and a 12-foot grain depth in a 30-foot diameter bin, let's compare the total air flow with that required for grain depths of 6 feet and 16 feet. Table 4 shows the following values for a 10 hp fan:
Grain depth 6 ft. 12 ft. 16 ft. Grain volume 3,393 bu. 6,786 bu. 9,048 bu. Est. air flow 4.23 cfm/bu 1.86 cfm/bu. 1.28 cfm/bu. Total air flow 14,352 cfm 12,622 cfm 11,581 cfm
The total air flow values are simply grain volume multiplied by cfm/bu. Note that total air flow increases as the grain depth and volume decrease. In this way, air flow per bushel and-drying potential are sharply increased.
What effect would doubling horsepower have on air flow?
Looking at the same 6-, 12- and 16-foot grain depth columns in Table 4, we see that doubling the fan horsepower from 10 to 20 hp increases the air delivery-- both per bushel and total--by only about one-third. Thus, roughly two-thirds of the horsepower (energy) is expended with no increase in air flow.
Grain depth 6 ft. 12 ft. 16 ft. Grain volume 3,393 bu. 6,786 bu. 9,048 bu. 10-hp fan 4.23 cfm/bu. 1.86 cfm/bu. 1.28 cfm/bu. 20-hp fan 6.25 cfm/bu. 2.46 cfm/bu. 1.65 cfm/bu.
What, then, happened to this two-thirds of the additional 10 horsepower? It was converted into heat, because of the "churning" of the air that the fan produced as it worked to force the increased air flow through "the same size hole" (i.e., the bin diameter which did not change). Although this loss reflects a loss in air flow efficiency, it is not a total loss, since the added heat is useful in drying grain.
Performance data for two fans having the same horsepower and air flow capabilities can be added to estimate total system performance. Two smaller fans may actually deliver slightly more or less air flow than a larger fan of the same total horsepower, depending on the combined air flow characteristics of the two smaller units compared with the larger one. But the difference will usually be small.
Since air flow rates for dryeration and bin cooling are below that required for bin drying, greater depths of grain (up to 50 feet) may be processed when air flow rates are 0.5 cfm/bu. Also, cooling fronts traverse the grain bed roughly 50 times faster than drying fronts. Thus, whereas grain spoilage is the limiting criterion for any drying bed over 20 feet deep (involving more than a point or two of moisture removal), the upper limits of cooling depths are determined largely by the cost of owning and operating the horsepower required to push air through the grain mass.
Table 5 presents data to help estimate the horsepower required for dryeration and bin cooling structures. The data apply to both hopper- and flat-bottom storages. The critical consideration is to make sure that the air supply system is adequate--i.e., has sufficient perforated floor area, supply duct cross-sectional area and fan horsepower.
All static pressure values for a given air flow rate are the same for each corresponding grain depth, regardless of bin size. For instance, the static pressure for the 0.5 cfm/bu. air flow rate is 4.4 inches of water for a 30-foot grain depth at all bin diameters. The reason is that the air flow per bushel and grain depth are the same in all cases.
Doubling a bin's floor area doubles its bushel capacity for the same grain depth. But if twice the number of bushels is to be aerated at the same 0.5 cfm/bu., the total amount of air flow must also double. However, the velocity of air flowing through any one column of grain will be constant, so static pressure will also be constant.
In contrast, increasing the air flow rate from 0.5 to 0.75 cfm/bu. in the 30-foot diameter bin for a 30-foot grain depth, for instance, increases the static pressure from 4.4 to 7.5 inches. Pushing more air through the "same size hole" sharply increases air velocity, resulting in greater air drag and resistance. In this case, a centrifugal rather than a vane-axial fan should be used.
For example, consider a 24-foot diameter bin, filled to a 20-foot level. The holding capacity is shown in Table 5 to be 7238 bushels--a big day's run for a large grain farm. Reading across the 24-foot diameter, 20-foot grain depth line, note that 2.3 hp is required to deliver 0.5 cfm/bu. Doubling the air flow rate to 1.0 cfm/bu. requires 10.2 hp-almost a five-fold increase!
The amount of perforated surface area needed to deliver the required air into the grain is shown in the three righthand "duct area" columns of Table 5. If the perforated area shown for your cooling bin is too small, increase it to bring the air distribution system into the recommended range. If this is not possible, shift to a lower air flow rate or lower grain depth to reduce air flow to the capacity of the perforated surface area.
If the size of your cooling bin is not listed in Table 5, you can estimate the horsepower and perforated surface areas as follows:
1. Calculate the holding capacity of your bin for the grain depth desired, using a factor of 1.25 cu.ft./bu.
2. Select the bin diameter from Table 5 closest in bushel capacity for the same storage height, but larger than your unit.
3. Divide the bushel capacity of your bin by that of the bin in Table 5. (Remember, the bushel capacities of the two bins must be for the same fill height.) The result is the ratio of your bin size to the slightly larger unit of Table 5.
4. Read the horsepower and perforated surface area values for the larger bin from Table 5.
5. Multiply these larger bin horsepower and surface area values by the ratio in step 3 to find the values for your bin. The only restriction is that your bin must have a uniform cross-sectional area for its full height.
Air volume Static pressure Fan power Duct area Bin Grain Grain ------------- ------------- ------------- ---------- dia. depth volume 1/2 3/4 1 1/2 3/4 1 1/2 3/4 1 1/2 3/4 1 -------------------------------------------------------------------------------------------------- ft. ft. bu. cu.ft./min. in. water sq.~. sq.in. 14 2.5 308 154 231 308 0.52 0.53 0.54 0.03 0.04 0.05 5 8 10 5.0 616 308 462 616 0.57 0.62 0.67 0.06 0.09 0.13 10 15 21 7.5 924 462 693 924 0.67 0.77 0.89 0.10 0.17 0.26 15 23 31 10.0 1232 616 924 1232 0.83 1.03 1.28 0.16 0.30 0.50 21 31 41 12.5 1539 770 1155 1539 1.03 1.36 1.80 0.25 0.49 0.87 26 38 51 15.0 1847 924 1385 1847 1.31 1.85 2.17 0.38 0.81 1.26 31 46 62 17.5 2155 1078 1616 2155 1.60 2.34 3.65 0.54 1.19 2.48 36 54 72 20.0 2463 1232 1847 2463 2.06 3.08 4.40 0.80 1.79 3.41 41 62 82 30.0 3695 1847 2771 3695 4.40 7.50 11.30 2.56 6.54 13.14 62 92 123 40.0 4926 2463 3695 4926 8.30 14.90 **** 6.43 17.32 **** 82 123 *** 50.0 6158 3079 4618 6158 14.00 **** **** 13.56 **** **** 103 *** *** 18 2.5 509 254 382 509 0.52 0.53 0.54 0.04 0.06 0.09 8 13 17 5.0 1018 509 763 1018 0.57 0.62 0.67 0.09 0.15 0.21 17 25 34 7.5 1527 763 1145 1527 0.67 0.77 0.89 0.16 0.28 0.43 25 38 51 10.0 2036 1018 1527 2036 0.83 1.03 1.28 0.27 0.49 0.82 34 51 68 12.5 2545 1272 1909 2545 1.03 1.36 1.80 0.41 0.82 1.44 42 64 85 15.0 3054 1527 2290 3054 1.31 1.85 2.17 0.63 1.33 2.09 51 76 102 17.5 3563 1781 2672 3563 1.60 2.34 3.65 0.90 1.97 4.09 59 89 119 20.0 4072 2036 3054 4072 2.06 3.08 4.40 1.32 2.96 5.64 68 102 136 30.0 6107 3054 4580 6107 4.40 7.50 11.30 4.23 10.81 21.72 102 153 204 40.0 8143 4072 6107 8143 8.30 14.90 **** 10.63 28.63 **** 136 204 *** 50.0 10179 5089 7634 10179 14.00 **** **** 22.42 **** **** 170 *** *** 21 2.5 693 346 520 693 0.52 0.53 0.54 0.06 0.09 0.12 12 17 23 5.0 1385 693 1039 1385 0.57 0.62 0.67 0.12 0.20 0.29 23 35 46 7.5 2078 1039 1559 2078 0.67 0.77 0.89 0.22 0.38 0.58 35 52 69 10.0 2771 1385 2078 2771 0.83 1.03 1.28 0.36 0.67 1.12 46 69 92 12.5 3464 1732 2598 3464 1.03 1.36 1.80 0.56 1.11 1.96 58 87 115 15.0 4156 2078 3117 4156 1.31 1.85 2.17 0.86 1.81 2.84 69 104 139 17.5 4849 2425 3637 4849 1.60 2.34 3.65 1.22 2.68 5.57 81 121 162 20.0 5542 2771 4156 5542 2.06 3.08 4.40 1.80 4.03 7.67 92 139 185 30.0 8313 4156 6235 8313 4.40 7.50 11.30 5.75 14.71 29.56 139 208 277 40.0 11084 5542 8313 11084 8.30 14.90 **** 14.47 38.97 **** 185 277 *** 50.0 13855 6927 10391 13855 14.00 **** **** 30.52 **** **** 231 *** *** 24 2.5 905 452 679 905 0.52 0.53 0.54 0.07 0.11 0.15 15 23 30 5.0 1810 905 1357 1810 0.57 0.62 0.67 0.16 0.26 0.38 30 45 60 7.5 2714 1357 2036 2714 0.67 0.77 0.89 0.29 0.49 0.76 45 68 90 10.0 3619 1810 2714 3619 0.83 1.03 1.28 0.47 0.88 1.46 60 90 121 12.5 4524 2262 3393 4524 1.03 1.36 1.80 0.73 1.45 2.56 75 113 151 15.0 5429 2714 4072 5429 1.31 1.85 2.17 1.12 2.37 3.71 90 136 181 17.5 6333 3167 4750 6333 1.60 2.34 3.65 1.59 3.50 7.27 106 158 211 20.0 7238 3619 5429 7238 2.06 3.08 4.40 2.35 5.26 10.02 121 181 241 30.0 10857 5429 8143 10857 4.40 7.50 11.30 7.52 19.22 38.61 181 271 362 40.0 14477 7238 10857 14477 8.30 14.90 **** 18.90 50.90 **** 241 362 *** 50.0 18096 9048 13572 18096 14.00 **** **** 39.86 **** **** 302 *** *** 27 2.5 1145 573 859 1145 0.52 0.53 0.54 0.09 0.14 0.19 19 29 38 5.0 2290 1145 1718 2290 0.57 0.62 0.67 0.21 0.34 0.48 38 57 76 7.5 3435 1718 2577 3435 0.67 0.77 0.89 0.36 0.62 0.96 57 86 115 10.0 4580 2290 3435 4580 0.83 1.03 1.28 0.60 1.11 1.84 76 115 153 12.5 5726 2863 4294 5726 1.03 1.36 1.80 0.93 1.84 3.24 95 143 191 15.0 6871 3435 5153 6871 1.31 1.85 2.17 1.42 3.00 4.69 115 172 229 17.5 8016 4008 6012 8016 1.60 2.34 3.65 2.02 4.43 9.21 134 200 267 20.0 9161 4580 6871 9161 2.06 3.08 4.40 2.97 6.66 12.68 153 229 305 30.0 13741 6871 10306 13741 4.40 7.50 11.30 9.51 24.32 48.86 229 344 458 40.0 18322 9161 13741 18322 8.30 14.90 **** 23.93 64.43 **** 305 458 *** 50.0 22902 11451 17177 22902 14.00 **** **** 50.45 **** **** 382 *** *** 30 2.5 1414 707 1060 1414 0.52 0.53 0.54 0.12 0.18 0.24 24 35 47 5.0 2827 1414 2121 2827 0.57 0.62 0.67 0.25 0.41 0.60 47 71 94 7.5 4241 2121 3181 4241 0.67 0.77 0.89 0.45 0.77 1.19 71 106 141 10.0 5655 2827 4241 5655 0.83 1.03 1.28 0.74 1.37 2.28 94 141 188 12.5 7069 3534 5301 7069 1.03 1.36 1.80 1.15 2.27 4.00 118 177 236 15.0 8482 4241 6362 8482 1.31 1.85 2.17 1.75 3.70 5.79 141 212 283 17.5 9896 4948 7422 9896 1.60 2.34 3.65 2.49 5.46 11.37 165 247 330 20.0 11310 5655 8482 11310 2.06 3.08 4.40 3.67 8.22 15.66 188 283 377 30.0 16965 8482 12724 16965 4.40 7.50 11.30 11.74 30.03 60.32 283 424 565 40.0 22620 11310 16965 22620 8.30 14.90 **** 29.54 79.54 **** 377 565 *** 50.0 28274 14137 21206 28274 14.00 **** **** 62.28 **** **** 471 *** *** 33 2.5 1711 855 1283 1711 0.52 0.53 0.54 0.14 0.21 0.29 29 43 57 5.0 3421 1711 2566 3421 0.57 0.62 0.67 0.31 0.50 0.72 57 86 114 7.5 5132 2566 3849 5132 0.67 0.77 0.89 0.54 0.93 1.44 86 128 171 10.0 6842 3421 5132 6842 0.83 1.03 1.28 0.89 1.66 2.76 114 171 228 12.5 8553 4277 6415 8553 1.03 1.36 1.80 1.39 2.75 4.84 143 214 285 15.0 10264 5132 7698 10264 1.31 1.85 2.17 2.12 4.48 7.01 171 257 342 17.5 11974 5987 8981 11974 1.60 2.34 3.65 3.01 6.61 13.75 200 299 399 20.0 13685 6842 10264 13685 2.06 3.08 4.40 4.44 9.95 18.95 228 342 456 30.0 20527 10264 15395 20527 4.40 7.50 11.30 14.21 36.33 72.99 342 513 684 40.0 27370 13685 20527 27370 8.30 14.90 **** 35.74 96.24 **** 456 684 *** 50.0 34212 17106 25659 34212 14.00 **** **** 75.36 **** **** 570 *** *** 36 2.5 2036 1018 1527 2036 0.52 0.53 0.54 0.17 0.25 0.35 34 51 68 5.0 4072 2036 3054 4072 0.57 0.62 0.67 0.37 0.60 0.86 68 102 136 7.5 6107 3054 4580 6107 0.67 0.77 0.89 0.64 1.11 1.71 102 153 204 10.0 8143 4072 6107 8143 0.83 1.03 1.28 1.06 1.98 3.28 136 204 271 12.5 10179 5089 7634 10179 1.03 1.36 1.80 1.65 3.27 5.77 170 254 339 15.0 12215 6107 9161 12215 1.31 1.85 2.17 2.52 5.33 8.34 204 305 407 17.5 14250 7125 10688 14250 1.60 2.34 3.65 3.59 7.87 16.37 238 356 475 20.0 16286 8143 12215 16286 2.06 3.08 4.40 5.28 11.84 22.55 271 407 543 30.0 24429 12215 18322 24429 4.40 7.50 11.30 16.91 43.24 86.86 407 611 814 40.0 32572 16286 24429 32572 8.30 14.90 **** 42.53 **8* **** 543 *** *** 40 2.5 2513 1257 1885 2513 0.52 0.53 0.54 0.21 0.31 0.43 42 63 84 5.0 5027 2513 3770 5027 0.57 0.62 0.67 0.45 0.74 1.06 84 126 168 7.5 7540 3770 5655 7540 0.67 0.77 0.89 0.79 1.37 2.11 126 188 251 10.0 10053 5027 7540 10053 0.83 1.03 1.28 1.31 2.44 4.05 168 251 335 12.5 12566 6283 9425 12566 1.03 1.36 1.80 2.04 4.03 7.12 209 314 419 15.0 15080 7540 11310 15080 1.31 1.85 2.17 3.11 6.58 10.30 251 377 503 17.5 17593 8796 13195 17593 1.60 2.34 3.65 4.43 9.72 20.21 293 440 586 20.0 20106 10053 15080 20106 2.06 3.08 4.40 6.52 14.61 27.84 335 503 670 30.0 30159 15080 22620 30159 4.40 7.50 11.30 20.88 53.38 **** 503 754 *** 40.0 40213 20106 30159 40213 8.30 14.90 **** 52.51 **** **** 670 *** *** 42 2.5 2771 1385 2078 2771 0.52 0.53 0.54 0.23 0.35 0.47 46 69 92 5.0 5542 2771 4156 5542 0.57 0.62 0.67 0.50 0.81 1.17 92 139 185 7.5 8313 4156 6235 8313 0.67 0.77 0.89 0.88 1.51 2.33 139 208 277 10.0 11084 5542 8313 11084 0.83 1.03 1.28 1.45 2.69 4.46 185 277 369 12.5 13855 6927 10391 13855 1.03 1.36 1.80 2.25 4.45 7.85 231 346 462 15.0 16625 8313 12469 16625 1.31 1.85 2.17 3.43 7.26 11.35 277 416 554 17.5 19396 9698 14547 19396 1.60 2.34 3.65 4.88 10.71 22.28 323 485 647 20.0 22167 11084 16625 22167 2.06 3.08 4.40 7.18 16.11 30.69 369 554 739 30.0 33251 16625 24938 33251 4.40 7.50 11.30 23.02 58.85 **** 554 831 *** 40.0 44334 22167 33251 44334 8.30 14.90 **** 57.89 **** **** 739 *** *** 48 2.5 3619 1810 2714 3619 0.52 0.53 0.54 0.30 0.45 0.61 60 90 121 5.0 7238 3619 5429 7238 0.57 0.62 0.67 0.65 1.06 1.53 121 181 241 7.5 10857 5429 8143 10857 0.67 0.77 0.89 1.14 1.97 3.04 181 271 362 10.0 14477 7238 10857 14477 0.83 1.03 1.28 1.89 3.52 5.83 241 362 483 12.5 18096 9048 13572 18096 1.03 1.36 1.80 2.93 5.81 10.25 302 452 603 15.0 21715 10857 16286 21715 1.31 1.85 2.17 4.48 9.48 14.83 362 543 724 17.5 25334 12667 19000 25334 1.60 2.34 3.65 6.38 13.99 29.10 422 633 844 20.0 28953 14477 21715 28953 2.06 3.08 4.40 9.38 21.05 40.09 483 724 965 30.0 43430 21715 32572 43430 4.40 7.50 11.30 30.06 76.87 **** 724 *** *** 40.0 57906 28953 43430 57906 8.30 14.90 **** 75.62 **** **** 965 *** *** ---------------------------------------------------------------------------------------------------- * Airflow resistance is based on ASAE standard data for clean shelled corn, increased 50 percent for fire material and compaction plus 0.5 inches of water column allowance for duct and entrance loss. Fan horsepower is calculated on the basis of 50 percent "installed" fan efficiency.
Figure 5 relates fan performance, grain depth and air flow rate simultaneously for a particular fan. The instructions for plotting the performance curve for your present or proposed fan are given with the graph.
The cfm-vs.-static-pressure data for the two 10-hp fans listed in Table 2 have been converted in Figure 5 into cfm/sq.ft. values for each static pressure level, assuming a 30-foot diameter bin. These values have been plotted in Figure 5 for both fans.
The two fan curves cross at about 4.6 inches of static pressure--the equal performance point--forming the basis for selecting fan type. The intersection of either fan curve with the grain depth and air flow rate curve specifies the system performance at that combination.
Fan curves for other sized units may be plotted similarly using the worksheet. Use thin paper or clear plastic overlay sheets to protect the original and reduce confusion.
It should be apparent from the previous examples and from Tables 6-16 that grain depth has a marked influence on drying system performance and, therefore, on drying capacity. If you are having drying capacity or grain spoilage problems in bin drying systems, reduce the grain depth! This reduces the static pressure and allows the fan to deliver more total air to a smaller quantity of grain. The higher air volume will then permit you to use higher temperatures (for the same limits on moisture), thereby further increasing your drying rate.
Many farmers don't like to batch dry in a bin at shallow depths, because their handling methods are not sized or convenient for frequent transfers of grain. However, in a given period of time and with the same equipment, you can dry roughly twice as much grain doing it in 4-foot deep batches as you could in 8-foot batches. Rather than assuming the drying system is at fault, maybe you should re-evaluate your grain transfer system to increase drying capacity.
Distribution of fine material in grain influences the rate and distribution of air flow. Paradoxically, a perfect distribution of fines causes the highest air flow resistance, because particles of fine material are in every open space between all adjacent kernels throughout the bin. Such perfect distribution may result in as much as a 200-400 percent increase in air flow resistance, compared with grain distributed as loose fill. This does not mean, though, that the fan air volume will be halved or quartered.
We noted earlier from Table 2 that fan delivery drops off as air flow resistance (static pressure) increases, but not on a one-to-one basis. Most high-pressure grain drying fans do not drop off rapidly in air volume capacity until the static pressure becomes high enough that the fan begins to "stall out."
Non-uniform air distribution, caused by uneven deposit of fines, means non-uniform drying or cooling. The fan must operate longer to accomplish drying or cooling in high resistance areas--requiring extra energy, time and cost. Bin drying and cooling performance is very dependent on air flow. The management and distribution of fine materials should not be taken lightly.
Manufacturers' horsepower listings on grain drying fans are sometimes confusing. For example, some fans show a dual rating, such as "10.0-12.5 hp." This stems from three practices.
First, some electric power suppliers restrict motor size on their lines to a maximum 7.5 or 10 hp, while others permit installing a dual-rated motor, as long as the lower rating falls within the prescribed restriction.
Second, axial-flow crop drying fans are "air-over" motor designs that generally supply added freedom in motor rating because of the increased cooling provided by the flowing air.
Third, fan horsepower depends on the pounds of air a fan moves per unit of time at a specified temperature. A fan moves the same volume of air in cold weather as in warm weather. But since cold air is denser than warm air (weighs more per cubic foot), the fan pumps more pounds of air in winter, requiring more power than in summer.
Thus, a fan may demand only 10 hp under one set of operating conditions early in the season, but may increase its demand to 12.5 hp as air becomes colder and drying circumstances change.
The two fan curves in the chart were developed from fan performance data similar to that supplied by all fan manufacturers. You may plot similar curves for your own specific fan(s) characteristics by following these instructions:
(Suggestion: Plot fan curves on clear overlay sheets to preserve the master chart for repeated use.)
Example: Fan horsepower = 10 hp
Floor area of 30 foot diameter bin = (30)2(3.1416)/4
= (900)(3.1416)/4
= 706.86 sq ft
Static pressure (inches water) ------------------------------------------------------------------------------------------------------------------------------------------- 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 ------------------------------------------------------------------------------------------------------------------------------------------- cfm cfm/ cfm cfm/ cfm cfm/ cfm cfm/ cfm cfm/ cfm cfm/ cfm cfm/ cfm cfm/ cfm cfm/ cfm cfm/ cfm cfm/ sq.ft. sq.ft sq.ft sq.ft. sq.ft. sq.ft. sq.ft. sq.ft. sq.ft. sq.ft. sq.ft. --------------------------------------------------------------------------------------------------------------------------------------------------- Vane- 19,400 27.4 18,400 26.0 17,300 24.5 16,300 23.1 15,100 21.4 14,000 19.8 12,800 18.1 - - 9,500 13.4 - - - - axial -------------------------------------------------------------------------------------------------------------------------------------------------- Centri- fugal 13,600 19.2 - 13,000 18.4 - 12,000 17.0 - 11,000 15.6 - 10,000 14.1 - 8,500 12.0 ---------------------------------------------------------------------------------------------------------------------------------------------------
Your Calculations: Fan Horsepower =
Floor area of _____ - foot diameter bin =
Static pressure (inches water) ------------------------------------------------------------------------------------------------------------------------------------------- 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 ------------------------------------------------------------------------------------------------------------------------------------------- cfm cfm/ cfm cfm/ cfm cfm/ cfm cfm/ cfm cfm/ cfm cfm/ cfm cfm/ cfm cfm/ cfm cfm/ cfm cfm/ cfm cfm/ sq.ft. sq.ft sq.ft sq.ft. sq.ft. sq.ft. sq.ft. sq.ft. sq.ft. sq.ft. sq.ft. --------------------------------------------------------------------------------------------------------------------------------------------------- Vane- axial -------------------------------------------------------------------------------------------------------------------------------------------------- Centri- fugal ---------------------------------------------------------------------------------------------------------------------------------------------------
Air flow rate needed for a grain depth (and corresponding bushel volume) of-- ------------------------------------------------------------------------------------ Fan 2 ft. 4 ft. 6 ft. 8 ft. 10 ft. 12 ft. 14 ft. 16 ft. 18 ft. 20 ft. 22 ft. 24 ft. hp (246) (493) (739) (985) (1232) (1478) (1724) (1970) (2217) (2463) (2709) (2956) ----------------------------------------------------------------------------------------------- cfm/bushel** 0.33 6.09 2.92 1.87 1.34 1.03 .83 .68 .57 .49 .42 .37 .33 0.5 7.95 3.81 2.36 1.65 1.24 .97 .78 .64 .54 .46 .40 .35 0.75 8.75 4.24 2.65 1.88 1.39 1.08 .86 .71 .60 .52 .45 .39 1.0 11.59 5.46 3.39 2.36 1.76 1.36 1.08 .87 .73 .61 .53 .46 1.5 16.18 7.20 4.29 2.94 2.17 1.68 1.35 1.12 .94 .81 .70 .61 2.0 18.66 8.26 5.02 3.42 2.52 1.95 1.57 1.30 1.09 .93 .81 .71 ---------------------------- 3.0 23.68 10.17 5.99 4.02 2.93 2.25 1.79 1.47 | 1.26 1.10 .97 .87 4.0 27.43 11.31 6.51 4.34 3.13 2.39 1.89 1.54 | 1.29 1.11 .98 .88 ----------------------------| 5.0 32.50 13.03 7.44 4.89 | 3.53 2.74 2.21 1.84 1.56 1.34 1.18 1.04 ------------- 7.5 36.85 14.47 | 8.45 5.79 4.25 3.29 2.64 2.18 1.83 1.59 1.40 1.24 ------ 10.0 41.17 | 16.97 9.87 6.66 4.88 3.77 3.02 2.51 2.13 1.84 1.61 1.42 12.5 44.25 | 17.84 10.39 7.03 5.18 4.03 3.24 2.70 2.30 1.99 1.74 1.54 | 15.0 47.66 | 18.41 10.90 7.40 5.46 4.27 3.47 2.89 2.45 2.13 1.88 1.67 ------------ 20.0 50.03 20.81 12.08 8.21 6.05 4.70 3.81 3.17 2.69 2.32 2.04 1.82 25.0 52.57 21.96 12.95 8.79 6.48 5.12 4.19 3.51 3.00 2.61 2.29 2.03 30.0 57.18 23.83 13.94 9.52 7.08 5.55 4.51 3.77 3.21 2.77 2.43 2.16 40.0 66.06 26.58 15.51 10.61 7.85 6.10 4.95 4.13 3.53 3.08 2.70 2.39 50.0 72.49 29.09 16.86 11.46 8.46 6.61 5.37 4.49 3.83 3.31 2.89 2.55 -------------------------------------------------------------------------------------------- *and ** See footnotes accompanying Table 4.
Air flow rate needed for a grain depth (and corresponding bushel volume) of-- ------------------------------------------------------------------------------------ Fan 2 ft. 4 ft. 6 ft. 8 ft. 10 ft. 12 ft. 14 ft. 16 ft. 18 ft. 20 ft. 22 ft. 24 ft. hp (407) (814) (1221) (1629) (2036) (2443) (2850) (3257) (3664) (4072) (4479) (4886) ----------------------------------------------------------------------------------------------- cfm/bushel** 0.33 3.76 1.84 1.20 .88 .69 .56 .47 .40 .35 .31 .27 .25 0.5 4.90 2.40 1.56 1.15 .88 .71 .59 .50 .43 .37 .33 .29 0.75 5.34 2.64 1.74 1.27 .98 .79 .66 .56 .48 .42 .36 .32 1.0 7.10 3.51 2.27 1.65 1.28 1.02 .84 .70 .60 .52 .45 .40 1.5 10.23 4.93 3.15 2.22 1.68 1.33 1.08 .90 .76 .65 .57 .50 2.0 12.11 5.70 3.58 2.54 1.94 1.55 1.27 1.07 .91 .78 .68 .60 3.0 15.62 7.28 4.49 3.14 2.37 1.87 1.51 1.26 1.07 .92 .80 .71 4.0 19.20 8.54 5.13 3.52 2.61 2.03 1.64 1.36 1.15 .99 .86 .75 -------------- 5.0 23.53 10.26 6.06 4.09 3.03 2.34 1.87 1.54 1.29 1.10 | .97 .86 ------------------------------------- 7.5 27.61 11.80 6.89 4.63 3.37 | 2.63 2.16 1.81 1.54 1.33 1.16 1.03 ------------- 10.0 31.92 13.30 7.74 | 5.40 4.04 3.15 2.55 2.11 1.79 1.54 1.34 1.18 12.5 34.96 14.34 8.32 | 5.73 4.26 3.33 2.70 2.24 1.90 1.64 1.43 1.27 | 15.0 39.44 15.54 8.93 | 5.91 4.41 3.48 2.84 2.37 2.01 1.73 1.52 1.34 ------ 20.0 42.19 16.36 | 9.63 6.74 5.01 3.90 3.17 2.64 2.25 1.94 1.70 1.50 25.0 45.08 17.15 |10.12 7.05 5.30 4.18 3.41 2.84 2.42 2.09 1.83 1.62 -------- 30.0 48.22 | 18.06 11.07 7.69 5.74 4.52 3.68 3.08 2.62 2.28 2.01 1.78 40.0 50.24 | 21.10 12.58 8.62 6.40 5.03 4.10 3.43 2.94 2.56 2.25 1.99 50.0 54.46 | 22.95 13.81 9.46 7.01 5.49 4.46 3.73 3.18 2.76 2.43 2.16 ----------------------------------------------------------------------------------------------- *and ** See footnotes accompanying Table 4.
Air flow rate needed for a grain depth (and corresponding bushel volume) of-- ------------------------------------------------------------------------------------ Fan 2 ft. 4 ft. 6 ft. 8 ft. 10 ft. 12 ft. 14 ft. 16 ft. 18 ft. 20 ft. 22 ft. 24 ft. hp (554) (1108) (1663) (2217) (2771) (3325) (3879) (4433) (4988) (5542) (6096) (6650) ------------------------------------------------------------------------------------------------ cfm/bushel** 0.33 2.78 1.37 .90 .66 .52 .43 .36 .31 .27 .24 .22 .20 0.5 3.63 1.79 1.17 .87 .68 .56 .47 .40 .35 .30 .27 .24 0.75 3.94 1.96 1.29 .96 .77 .62 .52 .45 .39 .34 .30 .27 1.0 5.24 2.60 1.72 1.27 .99 .81 .68 .58 .50 .44 .39 .35 1.5 7.58 3.73 2.42 1.76 1.36 1.08 .89 .75 .64 .56 .49 .44 2.0 9.12 4.38 2.82 2.03 1.56 1.25 1.04 .88 .76 .66 .58 .51 3.0 11.70 5.67 3.61 2.57 1.97 1.57 1.29 1.09 .94 .81 .71 .62 4.0 14.56 6.85 4.25 2.97 2.24 1.77 1.44 1.20 1.03 .89 .78 .69 5.0 18.37 8.35 5.11 3.56 2.63 2.05 1.67 1.39 1.18 1.02 .89 .78 ----------------------------- 7.5 21.84 9.80 5.92 4.07 3.00 2.33 1.87 1.55 | 1.31 1.15 1.02 .91 ---------------------- 10.0 25.82 11.34 6.72 4.59 3.38 | 2.70 2.22 1.86 1.58 1.37 1.20 1.06 12.5 28.69 12.43 7.27 4.96 3.64 | 2.88 2.35 1.96 1.67 1.45 1.27 1.13 | 15.0 33.74 13.87 8.01 5.38 3.93 | 2.97 2.43 2.03 1.74 1.52 1.34 1.19 -------- 20.0 37.04 14.73 8.47 5.64 | 4.26 3.39 2.79 2.34 1.97 1.71 1.50 1.33 ------ 25.0 39.75 15.66 8.96 |5.93 4.48 3.56 2.92 2.46 2.11 1.83 1.61 1.44 | 30.0 43.20 16.79 9.41 |6.44 4.92 3.92 3.20 2.68 2.29 1.99 1.75 1.56 ------ 40.0 45.74 17.42 |10.66 7.49 5.62 4.43 3.61 3.02 2.57 2.23 1.96 1.75 50.0 50.42 18.72 |11.56 8.20 6.17 4.86 3.96 3.32 2.83 2.45 2.15 1.91 ------------------------------------------------------------------------------------------------ *and ** See footnotes accompanying Table 4.
Air flow rate needed for a grain depth (and corresponding bushel volume) of-- ------------------------------------------------------------------------------------ Fan 2 ft. 4 ft. 6 ft. 8 ft. 10 ft. 12 ft. 14 ft. 16 ft. 18 ft. 20 ft. 22 ft. 24 ft. hp (724) (1448) (2171) (2895) (3619) (4343) (5067) (5791) (6514) (7238) (7962) (8686) ------------------------------------------------------------------------------------------------ cfm/bushel** 0.33 2.14 1.06 .70 .52 .41 .34 .29 .25 .22 .19 .17 .16 0.5 2.79 1.38 .91 .68 .53 .44 .37 .32 .28 .25 .22 .20 0.75 3.02 1.50 1.00 .74 .59 .49 .42 .36 .31 .28 .25 .22 1.0 4.02 2.00 1.32 .99 .78 .64 .54 .47 .41 .36 .32 .29 1.5 5.83 2.88 1.90 1.39 1.09 .89 .74 .63 .54 .48 .42 .38 2.0 7.07 3.43 2.22 1.62 1.26 1.02 .85 .73 .63 .55 .49 .44 3.0 9.04 4.44 2.90 2.11 1.63 1.31 1.08 .92 .79 .69 .61 .54 4.0 11.33 5.48 3.50 2.50 1.91 1.52 1.25 1.06 .90 .78 .68 .60 5.0 14.48 6.81 4.27 3.02 2.29 1.82 1.48 1.24 1.05 .91 .80 .71 7.5 17.33 8.08 5.01 3.51 2.64 2.08 1.69 1.41 1.19 1.03 .90 .80 ------------------------------------- 10.0 20.56 9.46 5.81 4.01 2.99 2.35 1.90 | 1.59 1.38 1.21 1.07 .95 12.5 23.03 10.51 6.38 4.36 3.25 2.54 2.05 | 1.71 1.47 1.28 1.13 1.00 | 15.0 28.49 12.21 7.18 4.85 3.56 2.76 2.22 | 1.76 1.52 1.32 1.17 1.04 -------| 20.0 31.51 13.32 7.68 5.15 3.77 2.90 | 2.38 2.01 1.73 1.52 1.34 1.19 25.0 34.62 14.36 8.23 5.50 3.99 3.04 | 2.51 2.12 1.82 1.59 1.41 1.26 ------- 30.0 38.41 15.32 8.84 5.84 4.20 | 3.31 2.75 2.33 2.01 1.75 1.55 1.38 --------------| 40.0 42.54 16.16 9.18 | 6.34 4.86 3.89 3.18 2.67 2.29 1.99 1.75 1.55 50.0 46.69 17.59 9.91 | 6.86 5.28 4.25 3.51 2.95 2.52 2.19 1.93 1.71 ------------------------------------------------------------------------------------------------ *and ** See footnotes accompanying Table 4.
Air flow rate needed for a grain depth (and corresponding bushel volume) of-- ------------------------------------------------------------------------------------ Fan 2 ft. 4 ft. 6 ft. 8 ft. 10 ft. 12 ft. 14 ft. 16 ft. 18 ft. 20 ft. 22 ft. 24 ft. hp (916) (1832) (2748) (3664) (4580) (5497) (6413) (7329) (8245) (9161) (10077) (10993) ------------------------------------------------------------------------------------------------ cfm/bushel** 0.33 1.70 .84 .56 .41 .33 .27 .23 .20 .18 .16 .14 .13 0.5 2.21 1.10 .72 .54 .43 .35 .30 .26 .23 .21 .18 .17 0.75 2.39 1.19 .79 .59 .47 .39 .33 .29 .26 .23 .21 .19 1.0 3.18 1.58 1.05 .79 .63 .52 .44 .38 .33 .30 .27 .24 1.5 4.62 2.29 1.51 1.13 .89 .73 .61 .53 .46 .41 .36 .32 2.0 5.63 2.75 1.80 1.32 1.03 .84 .71 .61 .53 .47 .42 .37 3.0 7.18 3.54 2.32 1.72 1.35 1.09 .91 .77 .67 .59 .52 .47 4.0 9.00 4.43 2.88 2.10 1.62 1.30 1.08 .91 .78 .68 .60 .53 5.0 11.61 5.59 3.57 2.56 1.97 1.58 1.30 1.10 .92 .82 .72 .63 7.5 13.94 6.67 4.23 3.01 2.30 1.83 1.50 1.26 1.08 .94 .82 .73 -------- 10.0 16.52 7.92 4.94 3.50 2.64 2.09 1.70 1.43 1.22 1.06 .93 | .83 12.5 18.77 8.81 5.49 3.85 2.89 2.26 1.85 1.55 1.32 1.14 1.00 | .89 | 15.0 23.66 10.63 6.38 4.38 3.24 2.51 2.03 1.68 1.43 1.23 1.07 | .92 -----------------------| 20.0 26.69 11.76 6.98 4.72 3.45 2.67 2.15 1.78 | 1.50 1.32 1.17 1.05 25.0 30.23 12.78 7.56 5.07 3.69 2.86 2.28 1.87 | 1.58 1.39 1.23 1.10 -------| 30.0 33.89 14.02 8.11 5.44 3.97 3.03 2.41 | 1.99 1.73 1.52 1.35 1.22 ---------------| 40.0 37.25 14.95 8.58 5.71 4.13 | 3.33 2.77 2.35 2.03 1.77 1.56 1.39 50.0 43.54 16.70 9.33 6.26 4.45 | 3.61 3.01 2.57 2.23 1.96 1.73 1.54 ------------------------------------------------------------------------------------------------ * and ** See footnotes accompanying Table 4.
Air flow rate needed for a grain depth (and corresponding bushel volume) of-- --------------------------------------------------------------------------------- Fan 2 ft. 4 ft. 6 ft. 8 ft. 10 ft. 12 ft. 14 ft. 16 ft. 18 ft. 20 ft. 22 ft. 24 ft. hp (1131) (2262) (3393) (4524) (5655) (6786) (7917) (9048) (10179) (11310) (12441) (13572) ----------------------------------------------------------------------------------------------- cfm/bushel** 0.33 1.38 .68 .45 .34 .27 .22 .19 .16 .14 .13 .12 .11 0.5 1.80 .89 .59 .44 .35 .29 .25 .21 .19 .17 .15 .14 0.75 1.94 .97 .64 .48 .38 .32 .27 .24 .21 .19 .17 .16 1.0 2.58 1.29 .85 .64 .51 .42 .36 .31 .28 .25 .22 .20 1.5 3.75 1.86 1.23 .92 .73 .60 .51 .44 .39 .35 .31 .28 2.0 4.58 2.25 1.48 1.09 .86 .70 .60 .51 .45 .40 .36 .32 3.0 5.83 2.89 1.90 1.41 1.11 .92 .77 .66 .58 .51 .45 .41 4.0 7.31 3.62 2.37 1.74 1.36 1.10 .92 .78 .68 .59 .53 .47 5.0 9.43 4.63 3.00 2.18 1.69 1.36 1.13 .96 .83 .72 .64 .57 7.5 11.39 5.54 3.57 2.58 1.99 1.60 1.33 1.12 .97 .85 .75 .66 10.0 13.51 6.58 4.23 3.02 2.32 1.86 1.53 1.28 1.10 .96 .84 .75 12.5 15.43 7.37 4.71 3.36 2.56 2.04 1.67 1.39 1.19 1.04 .92 .81 15.0 19.76 9.18 5.64 3.92 2.93 2.30 1.86 1.55 1.32 1.14 .99 .88 20.0 22.46 10.20 6.25 4.30 3.18 2.46 1.99 1.65 1.39 1.20 1.05 .93 25.0 25.93 11.31 6.77 4.66 3.44 2.65 2.12 1.76 1.49 1.27 1.10 .97 ------------------ 30.0 29.53 12.66 7.45 5.02 3.68 2.86 2.28 1.87 1.57 1.34 | 1.18 1.06 ----------------------| 40.0 33.00 13.78 7.97 5.33 3.89 2.99 2.38 | 2.04 1.63 1.56 1.39 1.25 50.0 39.39 15.57 8.92 5.87 4.26 3.27 2.58 | 2.21 1.92 1.70 1.52 1.36 ----------------------------------------------------------------------------------------------- *and ** See footnotes accompanying Table 4.
Air flow rate needed for a grain depth (and corresponding bushel volume) of-- ------------------------------------------------------------------------------------ Fan 2 ft. 4 ft. 6 ft. 8 ft. 10 ft. 12 ft. 14 ft. 16 ft. 18 ft. 20 ft. 22 ft. 24 ft. hp (1368) (2737) (4105) (5474) (6842) (8211) (9579) (10948) (12316) (13685) (15053) (16422) -------------------------------------------------------------------------------------------------- cfm/bushel** 0.33 1.14 .57 .38 .28 .22 .18 .16 .14 .12 .11 .10 .09 0.5 1.49 .74 .49 .37 .29 .24 .21 .18 .16 .14 .13 .12 0.75 1.60 .80 .53 .40 .32 .26 .23 .20 .17 .16 .14 .13 1.0 2.13 1.06 .71 .53 .42 .35 .30 .26 .23 .21 .19 .17 1.5 3.10 1.54 1.02 .76 .61 .50 .43 .37 .33 .29 .26 .24 2.0 3.80 1.88 1.23 .91 .72 .59 .50 .43 .38 .34 .31 .28 3.0 4.83 2.40 1.58 1.18 .93 .77 .65 .57 .50 .44 .39 .35 4.0 6.06 3.00 1.98 1.46 1.15 .95 .79 .68 .59 .52 .46 .42 5.0 7.81 3.88 2.53 1.85 1.44 1.17 .98 .83 .72 .63 .56 .50 7.5 9.43 4.65 3.03 2.22 1.73 1.40 1.17 .99 .86 .75 .66 .59 10.0 11.23 5.51 3.60 2.63 2.03 1.63 1.36 1.15 .99 .87 .77 .68 12.5 12.88 6.25 4.02 2.92 2.26 1.81 1.50 1.27 1.09 .95 .83 .74 15.0 16.50 7.87 4.97 3.50 2.64 2.09 1.71 1.43 1.22 1.05 .92 .82 20.0 18.94 8.88 5.51 3.87 2.91 2.28 1.84 1.53 1.30 1.12 .98 .87 25.0 22.21 10.09 6.08 4.21 3.14 2.48 1.99 1.64 1.39 1.20 1.05 .93 30.0 25.76 11.37 6.79 4.65 3.42 2.65 2.13 1.77 1.50 1.28 1.11 .98 ------------------------ 40.0 29.02 12.57 7.38 4.98 3.64 2.81 2.25 1.85 1.56 | 1.36 1.22 1.10 50.0 35.76 14.74 8.37 5.61 4.04 3.09 2.48 2.03 1.69 | 1.47 1.32 1.19 -------------------------------------------------------------------------------------------------- *and ** See footnotes accompanying Table 4.
Air flow rate needed for a grain depth (and corresponding bushel volume) of-- ----------------------------------------------------------------------------------- Fan 2 ft. 4 ft. 6 ft. 8 ft. 10 ft. 12 ft. 14 ft. 16 ft. 18 ft. 20 ft. 22 ft. 24 ft. hp (1629) (3257) (4886) (6514) (8143) (9772) (11400) (13029) (14657) (16286) (17915) (19543) ------------------------------------------------------------------------------------------------- cfm/bushel** 0.33 .96 .48 .32 .24 .19 .16 .13 .12 .10 .09 .08 .08 0.5 1.25 .62 .41 .31 .25 .20 .17 .15 .13 .12 .11 .10 0.75 1.35 .67 45 .33 .27 .22 .19 .17 .15 .13 .12 .11 1.0 1.79 .90 .60 .45 .36 .30 .25 .22 .20 .18 .16 .15 1.5 2.61 1.30 .86 .64 .51 .43 .36 .32 .28 .25 .23 .20 2.0 3.20 1.58 1.05 .78 .61 .51 .43 .37 .33 .29 .26 .24 3.0 4.07 2.02 1.34 1.00 .79 .66 .56 .48 .43 .38 .34 .31 4.0 5.10 2.53 1.68 1.25 .99 .81 .69 .59 .52 .46 .41 .37 5.0 6.57 3.27 2.15 1.58 1.24 1.01 .85 .73 .64 .56 .50 .45 7.5 7.93 3.95 2.58 1.90 1.49 1.21 1.02 .87 .75 .66 .59 .53 10.0 9.48 4.67 3.07 2.26 1.78 1.44 1.20 1.02 .89 .78 .69 .61 12.5 10.85 5.33 3.46 2.53 1.98 1.61 1.34 1.14 .98 .86 .76 .68 15.0 13.95 6.79 4.33 3.12 2.38 1.89 1.56 1.31 1.12 .98 .86 .76 20.0 16.20 7.72 4.86 3.46 2.63 2.09 1.71 1.43 1.21 1.05 .92 .81 25.0 19.13 8.88 5.47 3.81 2.87 2.26 1.85 1.55 1.31 1.13 .98 .87 30.0 22.27 10.12 6.16 4.26 3.17 2.47 2.00 1.65 1.40 1.21 1.06 .94 40.0 25.52 11.32 6.79 4.64 3.41 2.64 2.12 1.76 1.48 1.27 1.11 .97 50.0 32.36 13.52 7.94 5.26 3.86 2.96 2.35 1.93 1.63 1.40 1.21 1.05 ------------------------------------------------------------------------------------------------- *and ** See footnotes accompanying Table 4.
Air flow rate needed for a grain depth (and corresponding bushel volume) of-- --------------------------------------------------------------------------------------- Fan 2 ft. 4 ft. 6 ft. 8 ft. 10 ft. 12 ft. 14 ft. 16 ft. 18 ft. 20 ft. 22 ft. 24 ft. hp (2011) (4021) (6032) (8042) (10053) (12064) (14074) (16085) (18096) (20106) (22117) (24127) --------------------------------------------------------------------------------------------------- cfm/bushel** 0.33 .78 .39 .26 .19 .15 .13 .11 .09 .08 .08 .07 .06 0.5 1.01 .50 .34 .25 .20 .17 .14 .12 .11 .10 .09 .08 0.75 1.09 .55 .36 .27 .22 .18 .15 .13 .12 .11 .10 .09 1.0 1.45 .73 .48 .36 .29 .24 .21 .18 .16 .14 .13 .12 1.5 2.12 1.05 .70 .52 .42 .35 .30 .26 .23 .21 .19 .17 2.0 2.60 1.29 .85 .63 .50 .42 .35 .31 .27 .24 .22 .20 3.0 3.30 1.64 1.09 .81 .65 .54 .46 .40 .35 .31 .28 .26 4.0 4.13 2.06 1.37 1.02 .81 .67 .57 .49 .43 .39 .35 .31 5.0 5.32 2.65 1.76 1.31 1.03 .85 .72 .62 .54 .48 .43 .39 7.5 6.43 3.20 2.12 1.57 1.24 1.01 .85 .73 .64 .57 .51 .46 10.0 7.70 3.81 2.52 1.87 1.47 1.21 1.02 .87 .76 .67 .59 .53 12.5 8.79 4.37 2.87 2.11 1.66 1.35 1.14 .98 .85 .75 .66 .59 15.0 11.37 5.60 3.64 2.65 2.06 1.66 1.37 1.16 1.00 .88 .77 .69 20.0 13.34 6.40 4.14 2.97 2.29 1.84 1.52 1.29 1.10 .96 .85 .75 25.0 15.72 7.48 4.74 3.35 2.53 2.02 1.65 1.39 1.19 1.04 .92 .81 30.0 18.49 8.67 5.38 3.78 2.84 2.24 1.83 1.52 1.30 1.12 .98 .87 40.0 21.49 9.80 6.01 4.17 3.11 2.43 1.96 1.63 1.38 1.19 1.04 .92 50.0 28.39 12.15 7.19 4.92 3.57 2.76 2.22 1.83 1.53 1.31 1.14 1.01 --------------------------------------------------------------------------------------------------- *and ** See footnotes accompanying Table 4.
Air flow rate needed for a grain depth (and corresponding bushel volume) of-- ------------------------------------------------------------------------------------- Fan 2 ft. 4 ft. 6 ft. 8 ft. 10 ft. 12 ft. 14 ft. 16 ft. 18 ft. 20 ft. 22 ft. 24 ft. hp (2217) (4433) (6650) (8867) (11084) (13300) (15517) (17734) (19950) (22167) (24384) (26601) ---------------------------------------------------------------------------------------------------- cfm/bushel** 0.33 .70 .35 .23 .17 .14 .12 .10 .09 .08 .07 .06 .06 0.5 .92 .48 .30 .23 .18 .15 .13 .11 .10 .09 .08 .07 0.75 .99 .49 .33 .25 .20 .16 .14 .12 .11 .10 .09 .08 1.0 1.32 .66 .44 .33 .26 .22 .19 .16 .14 .13 .12 .11 1.5 1.92 .96 .64 .48 .38 .32 .27 .24 .21 .19 .17 .15 2.0 2.36 1.17 .78 .58 .46 .38 .32 .28 .25 .22 .20 .18 3.0 2.99 1.49 .99 .74 .59 .49 .42 .36 .32 .29 .26 .24 4.0 3.75 1.87 1.24 .93 .74 .61 .52 .45 .40 .35 .32 .29 5.0 4.83 2.41 1.60 1.19 .94 .78 .66 .57 .50 .44 .40 .36 7.5 5.83 2.91 1.93 1.43 1.13 .93 .79 .68 .59 .53 .47 .42 10.0 6.99 3.47 2.29 1.70 1.35 1.11 .94 .80 .70 .62 .55 .50 12.5 7.98 3.98 2.62 1.93 1.52 1.24 1.05 .90 .79 .69 .62 .55 15.0 10.33 5.10 3.35 2.44 1.90 1.55 1.29 1.10 .95 .83 .73 .65 20.0 12.17 5.87 3.80 2.76 2.13 1.72 1.43 1.21 1.05 .91 .81 .72 25.0 14.33 6.89 4.39 3.15 2.39 1.90 1.57 1.32 1.13 .99 .87 .78 30.0 16.94 8.03 5.02 3.56 2.69 2.13 1.74 1.46 1.24 1.08 .94 .84 40.0 19.77 9.11 5.64 3.95 2.96 2.33 1.88 1.57 1.33 1.15 1.00 .89 50.0 26.34 11.45 6.84 4.71 3.47 2.66 2.14 1.77 1.49 1.28 1.11 .97 ---------------------------------------------------------------------------------------------------- *and ** See footnotes accompanying Table 4.
Air flow rate needed for a grain depth (and corresponding bushel volume) of-- ------------------------------------------------------------------------------------- Fan 2 ft. 4 ft. 6 ft. 8 ft. 10 ft. 12 ft. 14 ft. 16 ft. 18 ft. 20 ft. 22 ft. 24 ft. hp (2895) (5791) (8686) (11581) (14476) (17372) (20267) (23162) (26058) (28953) (31848) (34744) ---------------------------------------------------------------------------------------------------- cfm/bushel** 0.33 .54 .27 .18 .13 .11 .09 .08 .07 .06 .05 .05 .04 0.5 .70 .35 .23 .17 .14 .12 .10 .09 .08 .07 .06 .06 0.75 .76 .38 .25 .19 .15 .13 .11 .09 .08 .08 .07 .06 1.0 1.01 .50 .34 .25 .20 .17 .14 .13 .11 .10 .09 .08 1.5 1.47 .73 .49 .37 .29 .24 .21 .18 .16 .14 .13 .12 2.0 1.81 .90 .60 .45 .35 .29 .25 .22 .19 .17 .16 .14 3.0 2.29 1.14 .76 .57 .45 .38 .32 .28 .25 .22 .20 .18 4.0 2.88 1.43 .95 .71 .57 .47 .40 .35 .31 .28 .25 .23 5.0 3.70 1.85 1.23 .92 .73 .61 .52 .45 .39 .35 .32 .29 7.5 4.47 2.23 1.48 1.11 .88 .73 .62 .54 .47 .42 .38 .34 10.0 5.37 2.67 1.77 1.32 1.05 .87 .74 .64 .56 .50 .45 .41 12.5 6.11 3.05 2.03 1.50 1.19 .98 .83 .72 .63 .56 .50 .46 15.0 7.94 3.94 2.60 1.93 1.52 1.24 1.04 .90 .78 .69 .61 .55 20.0 9.40 4.60 3.00 2.21 1.73 1.41 1.18 1.01 .88 .77 .68 .61 25.0 11.09 5.43 3.52 2.56 1.99 1.61 1.33 1.13 .97 .85 .76 .67 30.0 13.26 6.36 4.10 2.94 2.26 1.82 1.50 1.27 1.09 .95 .84 .75 40.0 15.59 7.36 4.65 3.32 2.53 2.02 1.66 1.39 1.19 1.03 .91 .80 50.0 21.18 9.73 5.87 4.09 3.05 2.41 1.96 1.61 1.36 1.17 1.03 .91 ---------------------------------------------------------------------------------------------------- *and ** See footnotes accompanying Table 4.
Single copies of the following Purdue Extension publications dealing with grain drying and handling are available to Indiana residents from their county Cooperative Extension Service offices or by writing to the CES Mailing Room, 310 S. Second St., Lafayette, IN 47905-1232:
AE-90, "Managing Grain (or Year-Round Storage"
AE-91, "Temporary Corn Storage in Outdoor Piles"
AE-93, "Adapting Silage Silos for Dry Grain Storage"
AE-107,"Dryeration and Bin Cooling tor Grain"
AE-108,"Solar Heat tor Grain Drying"
AED-20,"Managing Dry Grain in Storage"
ID-96, "Double Cropping Winter Wheat and Soybeans in Indiana"
The following Midwest Plan Service publications are available at the cost indicated from the Farm Building Plan Service, Agricultural and Biological Engineering Building, Purdue University, West Lafayette, IN 47907:
MWPS-13, "Planning Grain-Feed Handling ($2.50) MWPS-22, "Low Temperature and Solar Grain Drying ($3.00) For more information, contact Dirk Maier, Agricultural and Biological Engineering, phone: 317-494-1175 or e-mail: maier@ecn.purdue.edu
New 7/80
Cooperative Extension work in Agriculture and Home Economics, State of Indiana, Purdue University and U.S. Department of Agriculture cooperating: H.A. Wadsworth, Director, West Lafayette, IN. Issued in furtherance of the acts of May 8 and June 30, 1914. The Cooperative Extension Service of Purdue University is an equal opportunity/equal access institution.