Abstract:
An improved dryer ( 10 ) and drying methods are provided which increase overall dryer efficiency by maintaining substantially constant output air stream adiabatic saturation ratio and temperature values during the course of drying, notwithstanding the occurrence of upset conditions. The dryer ( 10 ) includes a dryer body ( 12 ), an input air heater assembly ( 14 ) including an air heater ( 32 ), and a control assembly ( 18 ). The dryer body ( 12 ) has a drying zone ( 30 ), with product inputs and outputs ( 20, 22 ) as well as an input ( 26 ) for a heated air stream and an output ( 28 ) for the cooled, moisture-laden output air stream. The dryer control assembly ( 18 ) includes temperature and humidity sensors ( 48, 50 ) coupled to controllers ( 54, 60 ) and a PLC ( 66 ). The controller ( 54 ) is coupled with an exhaust fan/damper unit ( 46 ) while controller ( 60 ) is connected with a fuel valve ( 36 ). In operation, the temperature and humidity of the output air stream are continuously measured by the sensors ( 48, 50 ), and the controllers ( 54, 60, 66 ) are operable to adjust the exhaust fan/damper unit ( 46 ) to regulate the relative proportion of output air exhausted to the atmosphere and recycled via conduit ( 52 ) for mixing with the input air stream, and also regulate the energy input to the dryer. Maintaining a substantially constant output air stream adiabatic saturation ratio and temperature allows dryer operation at significantly higher efficiencies as compared with prior systems.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention is broadly concerned with improved dryer apparatus and drying methods which maximize dryer efficiency and product exist moisture control, notwithstanding the occurrence of upset conditions such as differences in input air temperature and/or humidity, or the moisture content of incoming product to be dried. More particularly, the invention is concerned with such methods and apparatus wherein the adiabatic saturation ratio (ASR) and the temperature of the output air stream from the dryer are maintained at predetermined, substantially constant levels during drying; such ASR and output air temperature maintenance involves determination of the temperature and humidity of the output air stream and adjustment of recycle and exhaust portions of the output air stream and energy input to the dryer, to maintain the ASR and output air stream temperature.  
           [0003]    2. Description of the Prior Art  
           [0004]    A variety of continuous dryers have been proposed in the past for drying of agricultural products or processed pellets (e.g., feed pellets). Such dryers include rotary drum dryers, single or multiple-stage conveyor dryers, and staged, vertical, cascade-type dryers. In all such dryers, an initially wet product is contacted with an incoming heated air stream in order to reduce the moisture level of the product; as a consequence, the dryers emit a cooled, moisture-laden output air stream.  
           [0005]    Regardless of the type of dryer selected for a particular application, operators are always interested in maximizing drying efficiency, i.e., obtaining the maximum drying effect per pound of fuel consumed. A variety of control systems have been suggested in the past for this purpose. See, e.g., U.S. Pat. Nos. 1,564,566, 2,448,144, 4,513,759, 5,950,325, 5,347,727 and 6,085,443; Zagorzycki, Automatic Humidity Control of Dryers;  Chemical Engineering Progress , April 1983, and Miller, Drying as a Unit Operation in the Processing of Ready-to-Eat Breakfast Cereals:I. Basic Principles and Drying as a Unit Operation in the Processing of Ready-to-Eat Breakfast Cereals:II. Selecting a Dryer;  Cereal Foods World,  33:267-277 (1988). However, the problem of maintaining maximum dryer efficiency while controlling product exit moisture, during the course of a dryer run, which commonly may experience upsets, has not heretofore been satisfactorily resolved.  
           [0006]    A known drying parameter is the adiabatic saturation ratio of an air stream, typically the exhaust air stream from a dryer. The ASR is the ratio of air moisture in a given air stream, divided by the saturated air moisture at the same enthalpy. It is usually expressed as a percent, even though referred to as a ratio. An equivalent definition of ASR is the degree of saturation of an air stream when holding enthalpy constant. The humidity ratio for the air stream is divided by the humidity ratio at the intersection of the total enthalpy curve with the saturation curve, using appropriate psychrometric data.  
         SUMMARY OF THE INVENTION  
         [0007]    The present invention overcomes the problems outlined above and provides greatly improved drying methods and apparatus which are capable of maintaining high dryer efficiency notwithstanding the occurrence of upsets. Broadly speaking, the drying methods of the invention involve provision of a stream of input air having initial temperature and humidity levels, heating such input air stream to a desired temperature and contacting the heated air stream with an initially wet product in a drying zone to give a dried product and an output air stream. Control of the process is obtained by determining the temperature and humidity of the output air stream on a continuous basis, and using such information to maintain the adiabatic saturation ratio and the temperature of the output air stream at predetermined, substantially constant levels during the drying process, notwithstanding changes in one or more dryer parameters such as input air temperature and/or humidity levels, initially wet product moisture level and combinations thereof. In practice, maintenance of the adiabatic saturation ratio involves recycling a first portion of the output air stream back to the input air stream for mixing therewith, and exhausting a second portion of the output air stream to the atmosphere, in response to the determination of output air stream temperature and humidity. Additionally, the control typically involves adjusting the energy input to the dryer; in most cases, such energy input adjustment includes regulation of the temperature of the heated input air stream, but other energy inputs to the dryer, if any, may also be regulated.  
           [0008]    The invention is applicable to virtually all types of convection dryers where a wet product and a heated air stream are contacted for drying purposes. This includes but is not limited to rotary, conveyor, cascade-type, fluid bed and counterflow dryers. To this end, the dryers may incorporate indirect or direct heating of the input air stream; in the latter case, the effects of direct combustion must of course be taken into consideration.  
           [0009]    In preferred practice, the dryer is equipped with an exhaust fan/damper unit which serves to draw output air from the drying zone. The control apparatus is coupled with the damper so as to continually adjust as necessary the relative proportions of the output air stream which are recycled and exhausted to the atmosphere. Alternately, in lieu of an exhaust fan/damper unit, a variable speed exhaust fan can be employed. Conventional programmable logic controllers are used in such preferred systems to regulate dryer operation so as to maintain substantially constant ASR and output air stream temperatures. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    [0010]FIG. 1 is a schematic representation of a preferred dryer in accordance with the invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0011]    Turning now to the drawing, a dryer  10  in accordance with the invention broadly includes a dryer body  12  adapted to receive and dry initially wet product, with an input air heater assembly  14 , output air handling assembly  16  and control assembly  18  coupled to the dryer body.  
         [0012]    The dryer body  12  is schematically illustrated in the Figure, and includes a wet product inlet  20  and a dried product outlet  22 , as well as a heated air input line  26  and an air output line  28 . It will be understood that the body  12  can take the form of a wide variety of known dryers, such as rotary drum dryers, single or multiple-stage conveyor dryers or staged, vertical cascade-type dryers such as those disclosed in pending U.S. patent application Ser. No. 09/543,596 filed Apr. 5, 2000, incorporated by reference herein. In each case, the body  12  defines an internal drying zone  30  designed for contacting a heated input air stream and initially wet product.  
         [0013]    The input air heater assembly  14  includes a heater  32  having a fuel inlet line  34  coupled thereto, the latter being controlled by valve  36 . In addition, the assembly  14  includes an ambient air intake  38  and input line  40  for delivering a stream of input air to the heater  32 . The overall assembly further includes a recirculation fan  42  coupled with heater output  43  and line  26  as shown. A temperature sensor  44  is operatively coupled with line  26 . The heater  32  in the embodiment shown is an indirect heater, but if desired a direct heater could be used.  
         [0014]    The output air handling assembly  16  includes an exhaust fan/damper unit  46  made up of a conventional exhaust fan together with a selectively movable damper. The line  28  extends from dryer body  12  to the inlet of the unit  46 , and has temperature and humidity sensors  48 ,  50  coupled thereto. Finally, a recycle line  52  is coupled between the lines  28  and  40  for purposes to be explained.  
         [0015]    The control assembly  18  includes a humidity controller  54  with an input line  56  from sensor  50 , and an output line  58  to exhaust fan/damper unit  46 . Also, the assembly has a temperature controller  60  with an input line  62  from sensor  48  and an output line  64  leading to valve  36 . A programmable logic controller  66  is operatively coupled to the controllers  54  and  60  via lines  68  and  70 . Finally, a line  72  extends between temperature sensor  44  and PLC  66 .  
         [0016]    In the use of dryer  10 , a stream of input air having input temperature and humidity levels is generated at intake  38  and passed through input line  40  to heater  32 . At the same time, fuel is directed through inlet line  34  to the heater. Combustion within the heater  32  serves to heat the input air stream to a desired temperature. The fan  42  draws the heated input air stream through lines  43  and  26  in order to deliver such air to dryer  12 . The temperature of the heated input air stream is measured by sensor  44 . Initially wet product is delivered to the dryer via input  20  and, within the drying zone  30  the initially wet product is dried, leaving by way of output  22 . The output air stream from the dryer body  12  is conveyed by means of exhaust fan/damper unit  46  through line  28 , with the temperature and humidity thereof being determined by sensors  48  and  50 . Depending upon the position of the damper within unit  46  (or alternately the speed of the exhaust fan), first and second portions of the output air stream are recycled through line  52  and exhausted to the atmosphere. The recycled output air is mixed with the input air stream and reheated in heater  32 .  
         [0017]    During operation of the dryer  10  as described, the control assembly  18  comes into play in order to maintain the adiabatic saturation ratio (ASR) and the temperature of the output air stream at predetermined, substantially constant levels. This result obtains notwithstanding dryer system upsets such as caused by changes in a parameter selected from the group consisting of the temperature and/or humidity of the input air at intake  38 , the initially wet product moisture level (which can occur by a wetter starting product or an increase in the flow rate of wet product through dryer body  12 ), and combinations thereof. In particular, the control assembly  18  preferably serves to maintain the ASR within the range of about ±2 ASR percentage points (e.g., if the predetermined ASR is 90%, the maintenance should be from about 88% to 92%); more preferably, this range should be about ±0.5 ASR percentage points. In the case of output air temperature, the assembly  18  should maintain the temperature within the range of from about ±10% of the predetermined temperature, more preferably from about ±2%.  
         [0018]    Assuming a constant ASR, T 6  controls the moisture level of the dried product. Thus, an increase in T 6  will lower the dried product moisture and vice-versa. In practice, an operator will initially experimentally determine the value of T 6  that gives the desired product moisture content, and thus T 6  will then become the set point value.  
         [0019]    The control assembly  18  performs these functions by two primary system adjustments, namely an adjustment of the exhaust fan/damper unit  46  to alter the relative proportions of the output air stream which are recycled via line  52  and exhausted to the atmosphere, and adjusting the energy input to the dryer by controlling fuel to the heater  32  using valve  36 . The connection between sensor  44  and PLC  66  is a protective measure; if the sensor  44  detects an unacceptably high or low temperature, the PLC will shut down the entire system or permit the operator to lower the temperature through operation of valve  3   6 .  
         [0020]    For example, if the dryer  10  is operating in steady state conditions and the water content of the product to be dried is lowered (or a lower flow rate of the moist product occurs), the assembly  18  would typically reduce the heat input to the system by adjusting valve  36 , and also adjust exhaust fan/damper unit  46  so as to exhaust to the atmosphere a smaller proportion of the output air stream (which therefore increases the proportion of the output air stream recycled through line  52 ). Such adjustments are carried out until the predetermined ASR and output air stream temperatures are again substantially returned to their predetermined levels. Alternately, if the water content of the incoming product is increased (or a higher flow rate occurs), more heat would be added and a greater proportion of the output air stream would be exhausted to the atmosphere.  
         [0021]    Control of the ASR and output air stream temperature leads to greater dryer efficiencies. Generally speaking, for most dryers the predetermined ASR level should be in the range of from about 80-95%, more preferably from about 88-92%. Of course the output air stream temperature is extremely variable, depending upon the type of product being dried and desired final product moisture levels.  
         [0022]    As explained above, ASR is a description of the extent of saturation of air, and is directly related to overall energy efficiency (a higher ASR means a higher energy efficiency). As the output air is exhausted from the dryer it will lose heat in the ducting. This is an undesirable condition. Therefore, the operator will set the ASR low enough to avoid condensation in the dryer ducting during normal operating conditions, but otherwise as high as possible in order to maximize dryer efficiency. The advantage of using ASR as a primary control variable stems from the fact that dryer efficiency will remain essentially constant as long as the ASR is unchanged, regardless of what other variables may change.  
         [0023]    The following hypothetical examples set forth exemplary dryer operating conditions at steady state and these operating conditions after four different types of system upsets have been accommodated and the dryer is again at steady state. It is to be understood, however, that these examples are provided by way of illustration and nothing therein should be taken as a limitation upon the overall scope of the invention.  
       EXAMPLE  
       [0024]    The following Table  1  sets forth a series of computer-generated mass and energy balances for a dryer in accordance with the invention and as depicted in FIG. 1. In all of the upset cases 1-5 the mass and energy balances are taken after the control assembly  18  has reacted to the upset and returned the dryer to steady state conditions. In this Example, the ASR is selected as 90%, and the output air stream temperature measured by the sensor  48  (position 6) is 80° C. In FIG. 1, the boxed numerals and letters refer to the discrete positions within the dryer system, whereas the legends T 4 , T 6  and W 6  refer to sensors as described previously.  
         [0025]    In particular, the initial or start case is varied by lowering the moisture content of the incoming product from 0.23 to 0.22 kg H 2 0/kg product (Case 1); the moisture content of the incoming product is raised from 0.23 to 0.24 kg H 2 0/kg product (Case 2); the temperature of the input air stream at intake  38  is elevated from 21° to 35° C. (Case 3); the absolute humidity of the input air stream at intake  38  is elevated from 0.0080 to 0.0170 kg H 2 0/kg air (Case 4); and the moisture content of the incoming product is raised from 0.23 to 0.24 kg H 2 O/kg product, together with elevation of the temperature and absolute humidity of the input air stream at intake 38 to 35° C. and 0.0170 kg H 2 O/kg air, respectively (Case 5).  
         [0026]    As can be seen from Table 1, in each case the control assembly  18  serves to return the dryer to the desired 90% ASR, 80° C. output air stream temperature by appropriate adjustment of the heat input to the system via heater  32  and/or the ratio of exhausted to recycled output air from the dryer body  12 . Thus, in Case 1, the adjustment results in changes in the calculated values for GDP 1 , GDP 2 , GP 2 , CP 1 , GWP 1 , GPW 2 , HP 1 , HP 2 , GD 6 , C 6 , GW 6 , GW 2 , GD 2 , H 6 , H 2 , Q, Eff, GD 2 , W 4 , GD 4 , GD 5 , H 5 , H 4 , T 4 , and V 4 . This stems from the fact that, in returning to the steady state condition with predetermined ASR and output air stream temperatures, less input heat is delivered to heater  32  (position Q) resulting in a lower temperature T 4  (position 4).  
         [0027]    In a similar fashion, the remaining upset cases can be analyzed to ascertain the alterations effected by the control assembly  18 , as set forth in Table 1.  
                                                                                                                                                                                                                         TABLE 1                           MASS &amp; ENERGY BALANCES                    CASE 1   CASE 2   CASE 3                   INITIAL   less   more   hotter   CASE 4   CASE 5           start   water   water   amb   wetter amb   combination                        GIVEN (either outside variables or       control variables)            GP1   kg/hr   12,000   12,000   12,000   12,000   12,000   12,000       WP1   kg/kg   0.23   0.22   0.24   0.23   0.23   0.24       WP2   kg/kg   0.09   0.09   0.09   0.09   0.09   0.09       TP1   ° C.   80   80   80   80   80   80       TP2   ° C.   75   75   75   75   75   75       T2   ° C.   21   21   21   35   21   35       W2   kg/kg   0.0080   0.0080   0.0080   0.0080   0.0170   0.0170       T6   ° C.   80   80   80   80   80   80       ASR       90%   90%   90%   90%   90%   90%       Z4   m/s   0.63   0.63   0.63 0.63   0.63   0.63       AB   m 2     52   52   52   52   52   52       C&amp;R   kcal/hr   80,000   80,000   80,000   70,000   80,000   70,000            CALCULATED            W6 =   f(ASR,T6)   kg/kg   0.1075   0.1075   0.1075   0.1075   0.1075   0.1075       GDP1 =   GP1*(1-WP1)   kg/hr   9,240   9,360   9,120   9,240   9,240   9,120       GDP2 =   GDP1   kg/hr   9,240   9,360   9,120   9,240   9,240   9,120       GP2 =   GDP2/(1-WP2)   kg/hr   10,154   10,286   10,022   10,154   10,154   10,022       CP1 =   f(WP1)   kcal/° C./-   0.846   0.844   0.848   0.846   0.846   0.848               kg       CP2 =   f(WP2)   kcal/° C./-   0.818   0.818   0.818   0.818   0.818   0.818               kg       GWP1 =   GP1 − GPD1   kg/hr   2,760   2,640   2,880   2,760   2,760   2,880       GPW2 =   GP2 − GPD2   kg/hr   914   926   902   914   914   902       HP1 =   GP1*CP1*TP1   kcal/hr   812,160   810,240   814,080   812,160   812,160   814,080       HP2 =   GP2*CP2*TP2   kcal/hr   622,938   631,029   614,848   622,938   622,938   614,848       C4 =   Z4*AB   m 3 /s   32.5   32.5   32.5   32.5   32.5   32.5       h2 =   0.241*T2 + W2*   kcal/kg   9.85   9.85   9.85   13.27   15 23   18.72           (−589 + 0 45*T2)       V2 =   f(T2,W2)   m 3 /kg   0.830   0.830   0.830   0.881   0 853   0.893       V6 =   f(T6,W6)   ft 2 /lb   0.999   0.999   0.999   0.999   0.999   0.999       h6 =   0.241*T6 + W6*   kcal/kg   86 47   86.47   86.47   86.47   6.47   86.47           (−589 + 0.45*t6)       GD6 =   (GPW1 −   kg/hr   18,554   17,229   19,880   18,554   20,399   21,857           GPW2)/(W6 − W2)       CS =   V6*GD6/3600   ft 2 /min   5.15   4.78   5.52   5.15   5 66   6.07       GW6 =   W6*GD6   kg/hr   1,995   1,852   2,137   1,995   2,193   2,350       GW2 =   GW6 + GPW1 −   kg/hr   148   138   159   347   148   372           GPW2       GD2 =   GD6   kg/hr   18,554   17,229   19,880   16,554   20,399   21,857       H6 =   GD6*h6   kcal/hr   1,604,345   1,489,749   1,718,941   1,604,345   1,763,893   1,889,885       H2 =   GD2*h2   kcal/hr   182,734   169,682   195,786   246,271   310,779   409,063       Q =   HP2 − HP1 + H6 − H2   kcal/hr   1,232,389   1,140,856   1,323,923   1,168,852   1,263,892   1,281,591       Eff =   Q/(GPW1 − GPW2)   kcal/kg   668   665   669   633   685   648       T5 =   T6   ° C.   80   80   80   80   80   80       W5 =   W6*GD6   kg/kg   0 1075   0.1075   0.1075   0.1075   0.1075   0.1075       h5 =   h6   kcal/kg   86.47   86.47   86.47   86.47   86.47   86.47       W7 =   W6*GD6   kg/kg   0.1075   0.1075   0.1075   0.1075   0 1075   0 1075       GD2 =   GD6   kg/hr   18,554   17,229   19,880   18,554   20,399   21,857       T7 =   T6   ° C.   80   80   80   80   80   80            Assume W4 1     kg/kg   0.0877   0.0892   0.0861   0.0877   0.0877   0.0861            GD4 =   (GPW1 − GPW2)/(W5 −   kg/hr   93,146   93,677   92,431   93,240   93,240   92,431           W4)       GD5 =   GD4   kg/hr   93,146   93,677   92,431   93,240   93,240   92,431       H5 =   GD5*h5   kcal/hr   8,054,102   8,100,000   7,992,272   8,062,238   8,062,238   7,992,272       H4 =   H5 + HP2 − HP1   kcal/hr   7,864,881   7,920,789   7,793,040   7,873,016   7,873,016   7,793,040       T4 =   (H4/GD4-   ° C.   116.9   113.9   120.1   116.9   116.9   120.1           589*W4)/(0.241 + 0.4           5*W4)       V4 =   f(T4,W4)   m 3 /kg   1.256   1.249   1.264   1.256   1.256   1.264       C4 =   V4*GD4/3600   m 3 /s   32.5   32.5   32.5   32.5   32.5   32.5                       less heat   more heat   less heat   more heat   more heat                       less exh   more exh   same exh   more exh   more exh                       lower temp   higher   same   same temp   higher                           temp   temp       temp                       same eff   same eff   better eff   worse eff   worse eff                      1 W4 is ascertained by trial and error, until C4 calculated as Z4*AB = C4 calculated as V4*GD4/3600            VARIABLE   Description       AB   Area of product bed [m 2 ]       ASR   Adiabatic saturation ratio (see explanation below)       C   Volumetric air flow [m 3 /s]       CP   Specific heat of product (kcal/° C./kg]       C&amp;R   Convection &amp; radiation losses (kcal/hr)       Eff   Energy efficiency (kcal/kg water evaporated)       GD   Mass flow of dry air [kg/hr]       GP   Total mass flow of product [kg/hr]       GDP   Mass flow of bone dry product [kg/hr]       GWP   Mass flow of water portion of product [kg/hr]       GW   Mass flow of water vapor in air [kg/hr]       h   Specific enthalpy of moist air above ° C. [kcal/kg/° C.]       H   Total enthalpy of moist air above 0° C. [kcal/hr]       Q   Total heat added to dryer [kcal/hr]       T   Temperature of air (dry bulb) [° C.]       TP   Temperature of product [° C.]       W   Absolute humidity (mass of water vapor per unit mass of dry air) [kg/kg]       WP   Moisture content of product (wet basis) [kg/kg]       V   Specific volume of moist air [m 3 /kg]       Z   Air velocity through bed [m/s]          
 
         [0028]    [0028]                                   VARIABLE   Description                   AB   Area of product bed [m 2 ]       ASR   Adiabatic saturation ratio (see explanation below)       C   Volumetric air flow [m 3 /s]       CP   Specific heat of product (kcal/° C./kg]       C&amp;R   Convection &amp; radiation losses (kcal/hr)       Eff   Energy efficiency (kcal/kg water evaporated)       GD   Mass flow of dry air [kg/hr]       GP   Total mass flow of product [kg/hr]       GDP   Mass flow of bone dry product [kg/hr]       GWP   Mass flow of water portion of product [kg/hr]       GW   Mass flow of water vapor in air [kg/hr]       h   Specific enthalpy of moist air above ° C. [kcal/kg/° C.]       H   Total enthalpy of moist air above 0° C. [kcal/hr]       Q   Total heat added to dryer [kcal/hr]       T   Temperature of air (dry bulb) [° C.]       TP   Temperature of product [° C.]       W   Absolute humidity (mass of water vapor per unit mass of           dry air) [kg/kg]       WP   Moisture content of product (wet basis) [kg/kg]       V   Specific volume of moist air [m 3 /kg]       Z   Air velocity through bed [m/s]                    
         [0029]    As indicated, a goal of the invention is to achieve maximum possible dryer efficiency while controlling product exit moisture. In general, this obtains when the predetermined ASR is from about 80-95%, more preferably from about 88-92%. Table 2 below illustrates hypothetical, computer-generated dryer conditions and efficiencies at selected ASR&#39;s (88, 90, 92, 94%) and output air stream temperatures T 6  (150-210° C.), where the table symbols are explained in the legend below. A review of Table 2 confirms that as the ASR is increased, the energy efficiency improves. Moreover, when the ASR is held constant, the efficiency (EFF) varies only slightly with large changes in exhaust air stream temperature (T 6 ). Moreover, efficiencies (Eff) vary slightly with exhaust air stream temperatures (T 6 ), but vary more significantly with small ASR changes.  
                                                                           TABLE 2                           T6   Ts6       V6   h6   hs6   dew pt   T2       GD6   delta GP   Q   Eff   to dew   WBD       ASR   ° F.   ° F.   W6   ft 3 /lb   Btu/lb   Btu/lb   ° F.   ° F.   W2   lb/hr   lb/hr   Btu/hr   Btu/hr   Btu/hr   ° F.                   94%   210   153.30   0.23224   23.12   318.97   299.37   151.48   70   0.0078   15,792   3.216   3,956,750   1,230   309,528   57           200   149.70   0.20566   22.07   284.91   268.14   147.85   70   0.0078   17,920   3,216   3,971,186   1,235   300,515   50           190   145.78   0.18060   21.08   252.85   238.60   143.91   70   0.0078   20,527   3,216   3,989,679   1,241   292,517   44           180   141.48   0.15697   20.15   222.64   210.64   139.60   70   0.0078   23,793   3,216   4,013,601   1,248   285,511   39           170   136.77   0.13489   19.27   194.40   184.38   134.89   70   0.0078   27,946   3,216   4,043,853   1,257   280,018   33           160   131.67   0.11467   18.46   168.48   160.19   129.79   70   0.0078   33,261   3,216   4,079,883   1,269   275,736   28           150   126.10   0 09613   17.71   144.64   137.84   124.23   70   0.0078   40,284   3,216   4,124,049   1,282   273,932   24       92%   210   147.55   0.18744   21.92   267.20   246.88   145.07   70   0.0078   19,801   3,216   4,108,510   1,278   402,352   62           200   144.15   0.16764   21.06   241.15   223.48   141.66   70   0.0078   22,261   3,216   4,123,755   1,282   393,361   56           190   140.43   0 14857   20.24   216.13   200.87   137.93   70   0.0078   25,289   3,216   4,144,073   1,289   385,914   50           180   136.37   0.13040   19.46   192.30   179.22   133.87   70   0.0078   29,055   3,216   4,169,937   1,297   380,036   44           170   131.98   0.11340   18.73   169.96   158.86   129.49   70   0 0078   33,756   3,216   4,200,716   1,306   374,695   38           160   127.21   0.09751   18.03   149.04   139.70   124.73   70   0.0078   39,770   3,216   4,237,956   1,318   371,451   33           150   122.03   0.08281   17.38   129.60   121.82   119.55   70   0.0078   47,613   3,216   4,282,192   1,332   370,427   28       90%   210   142.92   0.15761   21.11   232.72   211.80   139.79   70   0.0078   23,828   3,216   4,260,977   1,325   498,481   67           200   139.32   0.14006   20.33   209.41   190.96   136.14   70   0.0078   27,008   3,216   4,290,561   1,334   498,304   61           190   135.96   0.12496   19.63   189.06   172.99   132.59   70   0.0078   30,505   3,216   4,313,198   1,341   490,220   54           180   131.92   0.11059   18.95   169.68   155.69   128.75   70   0.0078   34,792   3,216   4,340,383   1,350   486,738   48           170   127.75   0.09692   18 31   151.21   139.19   124.60   70   0.0078   40,159   3,216   4,373,583   1,360   482,717   42           160   123.25   0 08409   17.70   133.84   123 59   120.10   70   0.0078   46,956   3,216   4,412,475   1,372   481,295   37           150   118.38   0.07213   17.12   117.54   108.90   115.29   70   0.0078   55,744   3,216   4,457,652   1,386   481,625   32       88%   210   138.67   0.13412   16.98   205.58   184.09   134.83   70   0.0078   28,372   3,216   4,433,011   1,378   609,713   71           200   135.48   0.12109   19 93   187.58   168.51   131.64   70   0.0078   31,650   3,216   4,453,682   1,385   603,571   65           190   132.04   0.10854   19.20   170.23   153.43   128.21   70   0.0078   35,614   3,216   4,478,840   1,393   598,314   58           180   128.33   0.09650   18.59   153 59   138.89   124.52   70   0.0078   40,477   3,216   4,509,272   1,402   595,006   52           170   124.35   0.08512   18.01   137.80   125.04   120.54   70   0.0078   46,471   3,216   4,543,981   1,413   592,973   46           160   120.04   0 07431   17.45   122.75   111.79   116.29   70   0.0078   54,076   3,216   4,585,408   1,426   592,673   40           150   115.40   0.06419   16 92   108.59    99.25   111.72   70   0.0078   63,850   3,216   4,632,583   1,440   596,361   35                  
 
         [0030]    [0030]                                   VARIABLE   Description                   ASR   Adiabatic saturation ratio       delta GP   Mass of water evaporated from product [lb/hr]       dew pt   dew point (temperature of saturated air) [° F.]       Eff   Energy efficiency (Btu/lb water evaporated)       GD   Mass flow of dry air [lb/hr]       h   Specific enthalpy of moist air above 0° F. [Btu/lb/° F.]       H   Total enthalpy of moist air above 0° F. [Btul/hr]       hs   Saturation enthalpy of moist air above 0° F. [Btu/lb/° F.]       T   Temperature of air (dry bulb) [° F.]       to dew   Energy removed from air to lower it to dew point [Btu/hr]       Ts   Saturation temperature of air (wet bulb) [° F.]       V   Specific volume of moist air [lb 3 /lb]       W   Absolute humidity (mass of water vapor per unit mass of           dry air) [lb/lb]       WBD   Wet Buld Depression (dry bulb-wet bulb) [° F .]