MECHANICAL EQUIVALENT OF PRESSURE MARGULES 527 



fore the heat in this quantity of vapor is equal to 6.46 calories and 

 can do the corresponding amount of work. 



(1) The heat added to a kilogram of air during a com- Calories 



plete'cycle is 29 . 87 C p = 7 . 09 



(2) The heat withdrawn during the cycle. 26.11 C p =6.20 



(3) The heat converted into work 3-76 C p = o. 89 



(4) The efficiency of the added heat 3. 76/29 .87 =0.126 



We will now, for comparison, compute an example for dry air 

 by the first process: the h, P v P 2 , T 2 remains as before, but 7\ is so 

 chosen that the average difference of temperature of the two verti- 

 cal paths is nearly the- same as before in the example for above, i. e., 

 15° C. or 



P l = 770 1 



P, = 740 r 



Assumed data for h == 6000' 

 dT 



7\ = 273 



r, = 288 



* dz \ 



= — sIC 



(S).-'^ 



r, = 213.4 



r, = 228.4 



Computed data 

 p 1 = 330.07 mm T[ = 269.87 

 ^ 2 -333.38 r[ = 227.74 



Calories 



Added heat per kilogram 18. 13 C p = 4.31 



Abstracted heat per kilogram 14.346^, = 3.41 



Heat converted into work 3 . 7gC p = 0.90 



Efficiency 3.79/18. 13 =0.21 



In these examples of these two processes, for equal differences of 

 temperature between the two vertical columns of air we have 

 almost equal quantities of heat (0.89 and 0.90 calories) converted 

 into work; but in the second example for dry air the efficiency is 

 greater than in the first (for moist air). 



The quantity of heat converted into work in the unit of time is 

 nqjd, where n is a factor depending on the sectional area of the 



