R-12 R-23 Cascade System

[waqar]

Hi Everyone,

I m a final Year B.E student n m working on a Cascade System project to achieve -70 to -80 deg C.
But i have some constraints regarding its cost(not to exceed beyond 30000 INR i.e abt 650 $).The system need not be too large as its just used for practical purpose.
I have learned that abt 1/2 hp compressors for both LT n HT stages would be applicable.
I wanna ask that can i have a 2 stage cascade with even lesser compressor size.
Plz avoid using extreme technical terms as i am a novice in the field of Refrigeration.

Here is a sample of the stages that i have been working on.what changes need to be made to reduce compressor work.
Any help appreciated.

[waqar]

Hey Guys
Have been working on the design for past two days n thus far have been able to change the design as in the below images.Do u guys reckon dat a model as per the below design can be made up .Also i want to ask abt the cooling capacity n steps to increase it.




Any help Appreciated.