what does HIGH COMPRESSOR LIFT mean?

[hvacers]

what does HIGH COMPRESSOR LIFT mean?

I get alot of different explanations from different people and it is starting to become confusing.


please share insights

 

[willard3]

Compressor lift is compressor pressure.

Lift = pressure

 

[KiwiMace]

I would say pressure difference to be more exact, suction and discharge.

People often talk about lift in the same sense as cycle work, power and energy.

 

[hvacers]

some says its the difference of the evap and condensser temperature...???

 

[KiwiMace]

Therein lies the confusion. Inside the saturation curve, the temperature at a given pressure is constant. ie. Know the pressure, you know the temperature. People often speak condensing/evaporating pressure and temperature in the same context.

Note that discharge temperature of the compressor is typically higher than the condensing temperature due to superheat. The majority of the condenser coil is at the condensing temp tho.

 

[hvacers]

i reviewed the PH diagram of the system and noticed that the discharge superheat is quite high.

My assumption: Since the discharge superheat is high it gives the compressor a hard time and it needs to exert extra power to reach the superheat temp. By needing extra power it triggered the high compressor lift.


what do you think about my assumption kiwimace?

 

[MintJulep]

Compressor lift is simply the saturated condensing pressure minus the saturated evaporator temperature.

It's a mostly useless term, since almost no real systems operate at saturation on either side of the compressor.

Measure actual system pressures and superheat. Look at the PH diagram.

Don't worry about meaningless jargon.

 

[KiwiMace]

Usually this works the other way around.

Because of a warmer outdoor air temp or condenser water temp, you get a high condensing temp, which requires more lift, which uses more compressor energy.

 

[imok2]

Here is another explanation:

Lift (or head pressure) is the difference between condenser refrigerant pressure and evaporator refrigerant pressure. Using defined pressure-temperature relationships, lift can also be measured with the LCHWT and the leaving condenser-water temperature. Further, when the LCHWT and condenser-water flow are constant, the ECWT can be used as a metric for lift. Because most condenser water systems are designed for constant flow, ECWT is the most common metric for lift. In comfort-cooling applications, lower ECWT indicates lower lift, which lowers the compressor work . The relationship can be summarized as: lower ECWT = lower lift = lower compressor work = lower energy usage. In comfort-cooling applications, ambient weather conditions often allow facility owners to take advantage of ECWT as low as 50? (at AHRI conditions). The capability to use lower ECWT significantly improves chiller efficiency. In fact, greater chiller efficiency can be achieved by lowering lift than by lowering load. The efficiency improvements due to lower lift can be realized in both single-chiller and multiple-chiller installations.