Method for lubricating screw expanders and system for controlling lubrication

Abstract

A method for lubricating a screw expander includes condensing a mixture of working fluid and lubricant fed from the screw expander, through a condenser. At least a portion of the mixture of working fluid and lubricant fed from the condenser is pressurized from a first pressure to a second pressure through a pump. The method also includes separating the lubricant from the condensed working fluid of the at least portion of the mixture via a separator and feeding the lubricant to the screw expander; or separating the lubricant from the working fluid of the at least portion of the mixture via an evaporator and feeding the lubricant to the screw expander; or feeding the at least portion of the mixture of condensed working fluid and lubricant to the screw expander; or combinations thereof.

Description

BACKGROUND[0001]The embodiments disclosed herein relate generally to the field of a rankine cycle system and, more particularly, to a system and method for lubricating a screw expander in a rankine cycle system.[0002]Unlike the traditional steam rankine cycle, the organic rankine cycle (ORC) uses a higher molecular mass organic fluid. ORC allows heat recovery from low temperature sources such as industrial waste heat, geothermal heat, solar ponds, or the like. The low temperature heat is converted into useful work, that can itself be converted into electricity. In ORC, the working fluid is pumped to an evaporator where working fluid is evaporated, passes through a turbine and is finally re-condensed.[0003]In an ideal organic rankine cycle, the expansion is isentropic and the evaporation and condensation processes are isobaric. In real organic rankine cycle, the presence of irreversibilities lowers the cycle efficiency. The irreversibilities may occur in expanders and also in heat ex...

AI Technical Summary

Problems solved by technology

In real organic rankine cycle, the presence of irreversibilities lowers the cycle efficiency.

In the heat exchangers, the sinuous path flow of the working fluid ensures a better heat exchange but causes pressure drops, and lowers the amount of power recoverable from the cycle.

Such systems are complex and have a large footprint.

However such passive control leads to an excessive lubrication at operating conditions other than design-point operation causing reduction in cycle efficiency.

Images