3 replies to this topic

[siroos]

I simulate propylene(3STAGE)ðylen(2STAGE) refrigeration cycle in hysys.by chang the duty of evaporatorse ,we have different flow of refrigerant.for compressors in ethylen i used curve plus 1st & final stage pressures and 2nd stage suction pressure is calculated,but for propylen i used polytropic efficiency for each stage plus all pressures.use the curve instead of (efficiency plus pressure) gives different result at each discharg condition.why?what are the variables we can change in these system to see the effects on the compressor work OR THE PERFORMANCE OF SYSTEM?
we know that in multistage refrigeration system the 1st stage pressure and the final stage pressure are constant.but how we can optimize the intermediate pressures when the duty of evaporatorse are fixed.i want to know are existing intermediate pressures are the best or not?I USED COOLER AND HEATER INSTEAD OF EXCHANGER AND TEMPERATURE LEVEL OF PROCESS SIDE IS NOT INCLOUDED.
HOW CAN I UPLOAD THIS FILE?THANKS

[Art Montemayor]

Siroos:

Your written English is terrible. It is difficult to understand what you have written when you disobey the fundamental rules of English grammar:

• Always capitalize the first letter in a sentence;
• Always capitalize the personal pronoun, "I";
• Separate all sentences by 2 spaces;
• Use the symbol for a question (?) at the end of a sentence.

I have had to rewrite your post as follows:

"I simulated a propylene (3-STAGE) and an ethylene (2-STAGE) refrigeration cycle in Hysys. By changing the evaporators’ duty, we have different flow of refrigerant for the compressors. In ethylene I used curve plus 1st & final stage pressures and 2nd stage suction pressure is calculated. But for propylene i used polytropic efficiency for each stage plus all pressures. I used the curve instead of (efficiency plus pressure) and it gives a different result at each discharge condition. Why? What are the variables that we can change in these systems in order to see the effects on the compressor work OR THE PERFORMANCE OF SYSTEM?

We know that in a multistage refrigeration system the 1st stage pressure and the final stage pressure are constant. But, how can we optimize the intermediate pressures when the evaporators’ duties are fixed? I want to know if the existing intermediate pressures are the best or not. I USED A COOLER AND A HEATER INSTEAD OF an EXCHANGER AND THE TEMPERATURE LEVEL OF THE PROCESS SIDE IS NOT INCLUDED. HOW CAN I UPLOAD THIS FILE?"

Is the above what you intended to submit? If so, then confirm it. DO NOT USE "TEXTING" or texting language in our Forums. I personally will not respond to any member submitting a texting message. It is un-needed, hard to interpret, childish, illogical, and shows a lack of respect for all the work our members do in generating adult, serious, and experienced replies.

If you are trying to upload a Hysis file, read the Forum instructions. If you can operate Hysis, you should surely be able to follow the Forum instructions.

Thank you.

[Zilpa Varindravada]

Hi,

1. Check efficiency and outlet pressure predicted by curve. Are they fit to your value? If you want to make a comparison, check if inputs match each other.

2. Basically, the fridge compressor is driven by the same shaft. Interstage pressure is dictated by load of each stage. Anyway, you can do something to change the fridge pressure different from suction to compressure suction by throttling the suction valve but this gives you higher pressure/temperature of the stage. If too low temperature is not an issue, it would be better not to control let it be what it is.

ZV

[siroos]

Art Montemayor:

Hi. Thanks for your advice on written English and for rewriting the post.

Yes, it is the case. I need advice on this post.