Quote Originally Posted by Segei View Post
First. Liquid pump for LPI into discharge side. It can be done and it can be helpful to reduce condensing pressure and a lot of energy can be saved.
Second. Use economize port for the suction of vapor from economizer. This improve energy efficiency as well, because in this case vapor will be compressed from intermediate pressure to the condensing pressure instead of from suction pressure to the condensing pressure.
Third. Liquid injection into economize port is not efficient, because cooling refrigerant will evaporate and additional compressor work should be done to compress this vapor to condensing pressure. Better solutions. Inject refrigerant in LRI port. Every compressor manufacturer located this ports at later stage of compression to minimize work of the compressor that required to compress vapor to the condensing pressure.
Larger oil cooler. Usually, thermosyphon oil cooler have overfeed 3:1 and it will be able to handle load from superheated refrigerant.
First: if you want LRi on the LRI port of the compressor, wich is at the end of the compression, you NEED TO HAVE A PUMP, to supply the refrigerant to the TEAT valve, because the pressure at the end of the compressor compression is higher than the condenser pressure if you have a "normal system with a PM valve between the compressor and the condenser... you can have a discharge pressure of 30C, and a condensing pressure of 20C on a system with a VFD controlled condenser pump...
Second: I don't get this... if I am supplying "evaporated liquid" from the condenser as compared to gas from the economizer tank, what is the difference? there will be extra work on the compressor no matter what... So normally the economizer supplies the economizer port with gas at around -10C... There is extra load on the compressor in either case, how is the load from the LRI introduced in the economizer port different from the gas introduced to the LRI port?
I have seen a howden 255 with an economizer fitted, where the economizer valve opened when the compressor was at 100% and it was injected with -10C gas where the compressor almost took a bow and called it a night... so we had to introduce the economizer at -25 and slowly raise it to -10.
Third: The LRI port only works if you have a pump feeding refrigerant to the TEAT
if you want an economically working LRI, you have to use the economizer port... because the condensing pressure is lower than the pressure at the compressors "LRI stage"