Patent Publication Number: US-3969829-A

Title: Dehydration

Description:
This device consists of a thin sheet of metal in which has been cut small openings, raised a short distance above and parallel to the ground by props of material of low thermal conductivity. Also part of the device is a thin sheet of black flexible plastic which is placed over solid organic material to be dehydrated, which has previously been placed on the thin sheet of metal. Also part of the device are suitable rigid strips of material for holding the plastic sheet down around the edges of the area of the organic material. Also, if necessary, part of the device are suitable weights, to hold down the rigid strips of material. 
    
    
     In the drawing: 
     FIG. 1 is an enlarged cutaway section of the metal sheet, showing the arrangement of the openings. 
     FIG. 2 is a top view of the device completely assembled. 
     FIG. 3 is a transverse section taken on line 3--3 of FIG. 2. 
    
    
     The metal sheet 1 used is 28 gauge galvanized steel. The openings 2 are rectangular slots approximately 0.15 cm. by 4.0 cm. arranged lengthwise in rows such that the edge of each slot is 4 cm. from the corresponding edge of the slot in the next row. Each slot is 4 cm. from the next in its row. The slots are not staggered. This slot design covers practically the entire surface of the metal sheet 1 (34 inches by 261/2 inches). 
     The metal sheet 1 is held off the ground by four wood boards 3 whose cross sections are 3/4 inch by 1 3/4 inches. In cross section, they stand upright. Alongside each end of each board 3 is nailed a short board 4 of the same cross section to increase stability. 
     The plastic sheet 5 is 0.0038 cm. thick black flexible plastic. It is held down around the edges of the area of the organic material 6 by four thin metal strips 7. The metal strips are each held down by one small brick 8. 
     When in operation, sunlight falling upon the black plastic sheet 5 is converted to heat, which vaporizes water in the organic material 6. The resulting vapor is expelled from the device through the small openings 2 in the thin metal sheet 1. 
     In the two following experiments, because of shading from trees, the periods of potential sunlight were, respectively, approximately 10:15 AM to 5:50 PM and 10:20 AM to 5:55 PM Eastern Daylight Time. The device was placed at 30° 18&#39; 9&#34; North Latitude. Except when raining, during the period of potential sunlight, every hour on the hour was taken measurements of air temperature, temperature under the plastic sheet, and solar intensity. The temperature under the plastic sheet was measured by a thermometer which was kept inserted partway through a snug hole in the plastic sheet, the bulb of the thermometer being kept approximately halfway between the metal sheet and the plastic sheet. This thermometer is not part of the invention, but merely an instrument used to obtain experimental readings. An asterisk (*) following a time indicates that the hour following the time had overcast sky, which is here defined as an hour of time in which the solar intensity is reduced to less that 550 candles per square foot for a total of more than 10 minutes. 
     In order to illustrate this invention but without being limited thereto, the following examples are given. 
     EXAMPLE 1 
     970.8 gm. of waste corn material (This consists of the husk and the silk from ten ears of sweet corn and also the cobs, after the shucked ears of corn have been boiled in water for approximately fifteen minutes and have had the kernels eaten from them.) was cut into 1 - 2 gm. pieces and placed in the solar dehydration device to a depth of approximately 3 cm., to form a rectangle approximately 43 cm. by 56 cm., at approximately 11:00 AM June 20, 1974. The material was left in the solar dehydration device June 20, 21, 22, 23, and 24, 1974. During that time, the following data was obtained. 
     
         __________________________________________________________________________
Time (EDT)                                                                
       Air       Temperature under                                        
                            Solar intensity                               
       Temperature (°C)                                            
                 plastic sheet (°C)                                
                            (candles/ft..sup.2)                           
__________________________________________________________________________
June 20,                                                                  
1974                                                                      
Noon   35        61         600                                           
1:00 PM                                                                   
       39        67         600                                           
2:00 PM                                                                   
       37        66         600                                           
3:00 PM                                                                   
       37        65         600                                           
4:00 PM                                                                   
       35        60         600                                           
5:00 PM                                                                   
       33        53         600                                           
June 21,                                                                  
1974                                                                      
11:00 AM                                                                  
       31        52         600                                           
Noon   33        60         600                                           
1:00 PM                                                                   
       35        63         600                                           
2:00 PM                                                                   
       37        66         600                                           
3:00 PM                                                                   
       38        61         600                                           
4:00 PM                                                                   
       38        56         600                                           
5:00 PM*                                                                  
       36        53         600                                           
June 22,                                                                  
1974                                                                      
11:00 AM                                                                  
       32        53         600                                           
Noon   33        58         600                                           
1:00 PM                                                                   
       36        60         600                                           
2:00 PM                                                                   
       37        62         600                                           
3:00 PM                                                                   
       38        61         600                                           
4:00 PM                                                                   
       35        48         600                                           
5:00 PM                                                                   
       36        55         550                                           
June 23,                                                                  
1974                                                                      
11:00 AM                                                                  
       31        46         600                                           
Noon   32        55         600                                           
1:00 PM                                                                   
       33        62         600                                           
2:00 PM*                                                                  
       36        63         400                                           
3:00 PM*                                                                  
       29        44         275                                           
4:00 PM                                                                   
       33        53         600                                           
5:00 PM*                                                                  
       32        47         300                                           
June 24,                                                                  
1974                                                                      
1:00 PM*                                                                  
       24        26         325                                           
__________________________________________________________________________
 
    
     The declination of the sun on the days of this experiment was, respectively, +23° 25&#39; 52.1&#34;, +23° 26&#39; 23.6&#34;, +23° 26&#39; 30.4&#34;, +23° 26&#39; 12.4&#34;, and +23° 25&#39; 29.6&#34;. Therefore, the closest approaches of the sun to zenith on these days were, respectively, 6° 52&#39; 16.9&#34;, 6° 51&#39; 45.4&#34;, 6° 51&#39; 38.6&#34;, 6° 51&#39; 56.6&#34;, and 6° 52&#39; 39.4&#34;. 
     The device was subjected to a light drizzle from approximately 2:30 PM to 2:43 PM June 23, 2974. Immediately after the drizzle stopped, practically all the water was wiped from the plastic sheet with a paper towel. 
     The device was subjected to light showers and drizzle approximately 11:00 AM to 11:45 AM, 11:55 AM to 12:45 PM, and 1:00 PM to after 6:00 PM June 24, 1974. Therefore, the entire span of time for readings that day had overcast sky, and the only readings taken were for 1:00 PM. 
     At approximately 6:00 PM June 24, 1974, the plastic sheet was lifted and the partly dried waste corn material was removed from the device. It weighed 456.2 gm. Therefore, the loss of weight, representing water driven off, was 53%. The heat of combustion of the material was 3.253 kilocalories/gm. (5,856 B. T. U./pound). 
     EXAMPLE 2 
     1,966.7 gm of freshly shelled dent corn (field corn) kernels containing 53.6% by weight water were placed in the solar dehydration device to a depth of approximately 3 cm., to form a rectangle approximately 37 cm. by 50 cm., at approximately 11:55 AM July 13, 1974. The kernels were left in the solar dehydration device July 13, 14, 15, 16, and 17, 1974. During that time, the following data was obtained. 
     
         __________________________________________________________________________
Time (EDT)                                                                
       Air Temperature                                                    
                 Temperature under                                        
                            Solar intensity                               
       (°C)                                                        
                 plastic sheet (°C)                                
                            (candles/ft..sup.2)                           
__________________________________________________________________________
July 13,                                                                  
1974                                                                      
1:00 PM                                                                   
       35        56         600                                           
2:00 PM                                                                   
       35        62         600                                           
3:00 PM*                                                                  
       32        57         400                                           
4:00 PM                                                                   
       33        56         500                                           
5:00 PM                                                                   
       30        52         600                                           
July 14,                                                                  
1974                                                                      
11:00 AM                                                                  
       31        40         600                                           
Noon   34        55         600                                           
1:00 PM                                                                   
       33        61         600                                           
2:00 PM                                                                   
       34        65         600                                           
3:00 PM                                                                   
       35        63         600                                           
4:00 PM                                                                   
       34        62         600                                           
5:00 PM                                                                   
       31        57         600                                           
July 15,                                                                  
1974                                                                      
11:00 AM                                                                  
       29        45         600                                           
Noon   29        47         550                                           
1:00 PM                                                                   
       32        56         600                                           
2:00 PM                                                                   
       34        63         600                                           
3:00 PM                                                                   
       34        61         600                                           
4:00 PM                                                                   
       35        61         500                                           
5:00 PM                                                                   
       35        56         550                                           
July 16,                                                                  
1974                                                                      
11:00 AM                                                                  
       32        46         550                                           
Noon   33        56         600                                           
1:00 PM                                                                   
       35        61         600                                           
2:00 PM                                                                   
       37        60         600                                           
3:00 PM                                                                   
       38        63         600                                           
4:00 PM                                                                   
       38        62         600                                           
5:00 PM                                                                   
       36        56         550                                           
July 17,                                                                  
1974                                                                      
11:00 AM                                                                  
       32        49         600                                           
Noon   33        58         600                                           
1:00 PM                                                                   
       37        63         600                                           
2:00 PM                                                                   
       36        65         600                                           
3:00 PM                                                                   
       38        66         600                                           
4:00 PM                                                                   
       39        63         600                                           
5:00 PM                                                                   
       35        58         550                                           
__________________________________________________________________________
 
    
     The declination of the sun on the days of this experiment was, respectively, +21° 55&#39; 2.6&#34;, +21° 46&#39; 22.0&#34;, +21° 37&#39; 19.0&#34;, +21° 27&#39; 53.8&#34;, and +21° 18&#39; 6.7&#34;. Therefore, the closest approaches of the sun to zenith on these days were, respectively, 8° 23&#39; 6.4&#34;, 8° 31&#39; 47.0&#34;, 8° 40&#39; 50.0&#34;, 8° 50&#39; 15.2&#34;, and 9° 0&#39; 2.3&#34;. 
     At approximately 6:00 PM July 17, 1974, the plastic sheet was lifted and the partly dried dent corn kernels were removed from the device. They weighed 1,416.9 gm. therefore, the loss of weight, representing water driven off, was 28.0%. The partly dried kernels contained 38.8% by weight water. The percentage of broken or damaged kernels was negligible. Very little, if any, mustyness, sourness, or commercially objectionable foreign odor could be detected. No heating could be detected. 
     It is understood that the above detailed examples are given merely by way of illustration and that many variations may be made therein without departing from the spirit of this invention. For example, it would be within the spirit of this invention to use the solar dehydration device to dehydrate any solid organic material.