Oil management
WITT oil management returns refrigerant oil where it belongs
Compressors in refrigeration systems need sufficient lubrication with appropriate refrigerant oil. Some oil is always carried over with the refrigerant into the refrigeration system - even the latest compressors cannot avoid this.
To prevent the oil is not causing capacity losses, i.e. blocking heat exchanger surfaces, it needs to be removed from the refrigeration cycle. By occupying the evaporator surfaces with refrigerant oil, the COP of the system drops by approx. 3% per Kelvin.
With the automatic WITT oil management, valuable refrigerant oil is returned from the collection point back to the compressors in a controlled manner.
That way it does not need to be manually drained, which is not only time saving, but also prevents accidents related to this kind of maintenance.
In addition returning and re-using the oil saves operating costs (maintenance, disposal, refill of oil) and protects the environment.
A comparison
Efficiency with automatic oil recovery
| refrigerant | ammonia |
| performance [Qo] | 500 kW |
| refrigeration system | floated evaporator |
| inlet temperature of glycol [T ein] | -3°C |
| outlet temperature of glycol [T aus] | -6°C |
| operating hours | 6.000 h per year |
| electricity | 6 € provision per month | 0,12 € per kWh |
read more...
| clean evaporator | oily evaporator | |
| evaporation temperature [To] | -10°C | -12°C |
| compressor power consumption | 156 kW | 166 kW |
| COP | 3,20 | 3,01 |
| operating costs per year | 112.392 € | 119.592 € |
| savings | 7.200 € | |
An oil management saves based on that example 7.200 € per year just for electricity. Thus it makes sense to install an oil circle to your system.
With an automatic oil management from WITT you will have further benefits: Also the regular costs for maintenance and material will decrease.
economics
| refrigerant | ammonia |
| performance [Qo] | 500 kW |
| mass flow of compresser [kg/h] | 2.809,45 |
| oil discharge to system | 0,1 ppm of volume flow |
| oil volume flow [l/h] | 0,038 |
| evaporation temperature [To] | -10°C |
| condensing temperature [Tc] | +35°C |
| operating hours | 6.000 h per year |
| disposal costs for used oil | 0,60 € per liter |
| new refrigeration oil | 6,50 € per liter |
| monthly maintenance costs | 120,00 € |
| manual oil drain | WITT oil management | |
| oil discharge per year | 228 liter | |
| disposal costs | 137 € | --- |
| new oil | 1.482 € | --- |
| maintenance costs per year | 1.440 € | 240 € (2x per year) |
| installation (incl. material) | --- | approx. 4.500 € |
| amortization within | 1,5 years (4.500 / 3.059) | |
Already after approx. 18 month you will save in this example another 2.800 € per year.
That is a representive example using a WITT BDP incl. piping to one compressor. The exact savings could vary at your refrigeration system.
How the WITT oil management works
The WITT oil management is initiated right where the majority of refrigerant oil is collected in the refrigeration system. For ammonia system this is the lowest spot in the surge drum. Since refrigerant oil is insoluble in common ammonia systems and the densities differ (oil is heavier than ammonia) it settles at the bottom of the surge drum. The WITT oil management is also possible with soluble oils, i.e. in CO2 systems.
The WITT BDP oil recovery unit is installed at the lowest point of the ammonia surge drum and collects that way the refrigerant-oil-mixture entering the BDP vessel. With hot gas that is either time-controlled or demand controlled with the optional oil sensor the refrigerant-oil-mixture is pushed to a heat exchanger (WITT DWR). Inside the WITT DWR remaining liquid refrigerant is evaporated. An optional oil filter (WITT OF) at the outlet is making sure only clean oil is returned to the compressor.
In refrigeration systems with multiple compressors it is recommended to use a HDB3 stainless steel oil receiver to collect and distribute the oil to the compressors.
You can find above mentioned optional equipment such as sight glasses, oil filters or oil sensors under Accessories.
BDP oil recovery unit
HDB3 stainless steel oil receiver
