3 replies to this topic

[bittu]

Hello,

I have been assigned to design an ammonia refrigeration system as a final year class project. The refrigeration load is 1,000 KW. The evaporator temperature is 2 0C. The condensing temperature is 25 0C. I already calculated the compressor power required for this design condition and now, I would like to design evaporator condensing system. I appreciate if someone can help me in calculating the fan and pump power required for the above design conditions and also help me in calculating the amount of bleed stream and water make-up required. I know that the amount of bleed stream and water make-up is a function of cycle of concentration but I don't have the water data available (we can assume any reasonable chloride, TDS, TSS, etc information). Also, can someone please let me know how to calculate the surface area for the evaporative condenser for the above design conditions?

Thanks in advance for your help.

Edited by bittu, 26 December 2009 - 09:06 PM.

[Andres Valencia Michaud]

Hello,

I have been assigned to design an ammonia refrigeration system as a final year class project. The refrigeration load is 1,000 KW. The evaporator temperature is 2 0C. The condensing temperature is 25 0C. I already calculated the compressor power required for this design condition and now, I would like to design evaporator condensing system. I appreciate if someone can help me in calculating the fan and pump power required for the above design conditions and also help me in calculating the amount of bleed stream and water make-up required. I know that the amount of bleed stream and water make-up is a function of cycle of concentration but I don't have the water data available (we can assume any reasonable chloride, TDS, TSS, etc information). Also, can someone please let me know how to calculate the surface area for the evaporative condenser for the above design conditions?

Thanks in advance for your help.

Well, If I were you, I would simulate the cycle in Hysys (a cooler, a pump, a valve do I miss anything?). If the refrigeration takes place at constant pressure, then the heat balance is easy. You might want to read "Steam, Air and Gas Power" by W. H. Severns. It's a very old book but it happens to talk about old mechanical refrigeration systems like yours (come'on Ammonia isn't exactly the next step in refrigeration!).

[Art Montemayor]

Bittu:

You are probably confusing most of your readers by not explicitly stating WHAT type of refrigeration cycle or process you are employing. For example, you employ terms like "I would like to design evaporator condensing system" without making a distinction between the evaporator or the condenser. There is no such thing as "evaporator condensing system". There are evaporators, and then there are condensers. They are not one and the same.

You also write of "pump power, bleed stream and water make-up, cycle of concentration, water data, chloride, TDS, & TSS" so I strongly suspect you are trying to describe an ABSORPTION refrigeration system - and NOT A MECHANICAL refrigeration system as Andres Valencia is guessing. There is no pump, bleed steam, or water make-up involved in an ammonia mechanical refrigeration system. Nor is there any need to employ a simulation program to design the entire process. The entire design can easily be done by conventional, proven hand or spreadsheet calculations - with as much accuracy (or better!) than any simulator. Both the mechanical and absorption refrigeration cycles are fully explained in classical and well-known thermodynamic text books such as Faires, etc.

I suggest you concentrate on the thermodynamic text book description and explanation of the cycle you are dealing with and proceed to apply the thermodynamic calculations appropriately.

Good luck.

[Ramiz]

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