Question

A carnot's engine . with a perfect gas acting as the working substance , is operated backwards and is employed to freeze water at 0 ° C the engine is driven by a 200 W electric motor . find the amount of water frozen per minute . the outside temperature is 20 ° C. specific latent heat of fusion of ice = 80 cal /g and j = 4.2 j/cal

Answer 1

HELLO PARI : - ) 

coefficient  performance of the refrigerator , being ideal , is given by 

ω= > T2/( T1- T2)  

=> 273 K/ [ (273 + 20 K) --273 K ] 
 
= > 273/20 

Now , if W be the average work done on the working substance per second

and Q2 , be the average heat extracted from a body at lower temperature,

during that time , then 

ω = > Q2/W 

Q2 = > ωW  = > 273 ×200 /20 = > 2730 j/s = > 650 cal/s 

Now, if m be the mass of water frozen per minute , then , heat needed to be

extracted will be Q = > mL = > 80×m cal / g

But the actual heat extracte per minute 

= > 650 cal/s   ×  60s/min  -> 39 ×10^3 cal/min 

80m cal/g = >  39 ×10^3 cal/min 

and here we get m = > 487.5 g / min 

HOPE THIS HELPS YOU 

@ ENGINEER