Minimum discharge pressure for ammonia systems

[US Iceman]

Regarding to wet bulb approach. Idea of wet bulb approach is to balance capacities of compressors and evaporator condensers keeping total power(compressors + condensers) at minimum level. This feature is useful when outside temperature over 10C. If ambient temperature is lower than 10C, we usually run the plant at minimum allowable condensing pressure. It is very important to keep wet bulb approach at optimum level. Assume that optimum wet bulb approach is 10F. If we try to keep 6F( 4F or 2C difference), our condenser capacity should double. We can spend additional 200HP for condensers and we save just 50HP for compressors. We overspent 150HP.

That's the very point I'm talking about with clients right now. In a similar thought as the optimum suction pressure we were discussing, the optimum discharge pressure is not the lowest discharge pressure you can achieve.

It is the lowest discharge pressure which uses the least amount of total energy (condenser fans + compressor motors).

You raise a very good point that all should consider Sergei. Energy savings should be based on the total use, not the individual components.