An important issue of "Refrigeration Discharge Pressure"

[Rahju]

Hi Fellows

Refrigeration discharge temperature is determined by the condenser's capacity to reject heat. When the condensing pressure goes below a minimum pressure setting, selected by operators, condenser fans turn off. This reduces condenser capacity and prevents the temperature and associated pressure from going below the set point. Compressors require less energy to operate against low discharge pressures, but to reduce this discharge pressure, the condenser fans must operate more frequently. As condenser fans typically use significantly less energy than the compressor, reducing compressor use can lead to significant energy savings. Reducing compressor discharge pressure saves approximately 1% of compressor energy consumption for each degree Fahrenheit reduction of condensing temperature. ButOften there are specific applications that drive the need for high pressure set points. Below is a list of four common reasons for having such set points and how they can be fixed.

1. Liquid Injection Cooling typically consumes 5-15% of the compressor power to recompress injected refrigerant and is used to cool the compressor. Install thermosyphon oil cooling to avoid power and energy costs associated with liquid injection oil cooling. Thermosyphon cooling does not consume compressor power.

2. Expansion Device Design can lead to higher required discharge pressures. By looking into different designs, having your system evaluated and selecting components that operate well with lower discharge pressure, the efficiency of your refrigeration system can be improved.

3. Moving Refrigerant to Distant Endpoints can lead to a need for higher discharge pressures to ensure refrigerant can reach its destination. By installing liquid pumps in the system, discharge pressure can be reduced while still serving the entire refrigeration system.

4. Hot Gas Defrost is sometimes used to defrost evaporators as needed and requires a high discharge pressure. We suggest only raising the discharge pressure when needed for hot gas defrost and letting the discharge pressure drop lower otherwise, or using another defrost strategy such as applying warm process water. Check to make sure your facility does not require high pressure set points for special applications before making alterations to your process or equipment.

Good Luck.

[Rahju]

I wrote pretty regularly, but unfortunately this was the case.

This may be due to being a novice.

Excuse...

[Coorsman777]

Lot's of good points in this. There is always a lot of misconceptions
around low condensing temp.

[The MG Pony]

yup and the head aches of keeping a well tuned system, I use balanced port txv's which allow for lower head pressure while maintaining good function, and then use the VG47-AA head modulating valves to fix the head pressure to the ideal level, or a transducer driven vfd to drive the condensing fan at optimum.

higher initial cost but superior year round unit efficiency, but most penny wise pound foolish, they just want the cheapest plant now and running cost is ignored totally!

That is the hardest part of our jobs, to explain why the initial cost all be it high will save them the most money in the long run by being much more efficient energy wise, and due to lower pressures easier on the mechanical systems resulting in a higher mean time between failure rating!

[Josip]

I wrote pretty regularly, but unfortunately this was the case.

This may be due to being a novice.

Excuse...

Sorted ... I do believe ...


Best regards, Josip

[Rahju]

Sorted ... I do believe ...

Thank you so much.