RURAL ENGINEERING. 283 



condensers, especially the effect of design and operaUon upon tlie iinioimt of 

 injection water required and the vacuum obtained. 



In the evaporator tests there was much variation in the temperature fall, even 

 in evaporators of the same type, and there was little regularity in the variation 

 of the temperature fall in the different bodies. The results as regards the 

 effect of density and head on temperature of boiling were somewhat iri'egular, 

 and observations of head were possible only in a few cases although the tem- 

 perature rise is in all cases attributed to head as well as to density. 



A great variation in the coefficient of heat transmission in the different bodies 

 was found although the coefficient was always less for the last than for the 

 lu-eceding bodies. The greatest variation in the relative coefficients for quad- 

 ruples, that of the last body being 1, was with the standard type of evaporator, 

 that in the first being 5.09, in the second G.95, and in the third 6.03. The San- 

 born type was next in the amount of variation and the least variation was 

 found in the Kestner type. The highest actual coefficients were obtained from 

 the Webre atmospheric double effect. The film evaporators gave coefficients 

 considerably higher than did the submerged tube evaporators. The average 

 actual coefficient for the horizontal evaporators was some 13 per cent greater 

 than the average for the standard. 



The initial juice temperature was found to affect more or less the evaporating 

 capacity, and data are also given showing the so-called self-evaporation due to 

 the juice entering the first body at a temperature higher than that of boiling. 



The heating efficiency was found to vary from a minimum of 85.06 to a maxi- 

 mum of 9S.33 per cent, the average being about 94 per cent for all the tests, 

 including different types and different numbers of bodies. It was also found 

 that a multiple evaporator with a small number of bodies has a smaller loss 

 due to radiation in percentage of the total heat supplied than one with a larger 

 number of bodies. The effect of high rates of evaporation in increasing heat 

 efficiency are also brought out. 



In tests of vacuum pans, the coefficient of heat transmission for the coil 

 pans with straight strikes was found to vary from a minimum of 76.28 to a 

 maximum of 174.8, with the heating surface in fairly good condition. It is 

 pointed out that although there is no definite relation between the highest ratio 

 of length to diameter of coil and the coeflicient of heat transmission, the length 

 of the coil had much to do with the variation of the coefficients. Varying kinds 

 cf product were found to affect more or less the coefficient. 



The temperature rise was found to vary from a minimum of 11.9 to a maxi- 

 mum of 27.5 degrees, the average being 19.7 degrees. The minimum rise was 

 obtained with a calandria pan and the maximum with a 10-ft. coil pan. The 

 effect of purity upon the temperature rise is clearly shown. " The capacity of 

 a pan decreases with the purity, not only because of the low coefficient of heat 

 transmission, but because of the reduced temperature fall due to rise of the 

 boiling point as well." 



The average coefficient of heat transmission for the Expre.ss type of calandria 

 pan was 40 per cent greater than that in the coil pans and the temperature 

 rise of boiling due to hydrostatic head, density, etc., was less in the calandria 

 pans. 



As regards rate of vapor formation it is stated that "for all practical pur- 

 poses it may be assumed that the rate of vapor formation is proportional to 

 the rate of steam condensation . . . and the velocity of vapors in a coil pan 

 may be assumed to be the same at all times during a strike." The heat effi- 

 ciency in vacuum pans was found to vary from 90.9 to 9(5.95 per cent and the 

 tests did not show any difference in economy for coil and calandria pans. 



