Experimental investigation of low-temperature organic Rankine cycle using waste heat from gas turbine bearings for different conditions

Abstract

In power plants, a special type of oil is used for the lubrication and cooling of turbine bearings. The temperature of the cooling oil used for heat extraction from the bearings varies between 78 and 90 °C. Using waste heat from this oil will be a great advantage in terms of heat recovery. The overall thermal efficiency of gas turbine in power plants will also increase using this heat. In the literature, there are studies on organic Rankine cycle systems, but it has been seen that there are no studies on the use of waste heat from gas turbine bearings. In this paper, low-temperature organic Rankine cycle using waste heat from gas turbine bearings for different working conditions was investigated as experimentally. For this purpose, a prototype experiment setup was designed and thermodynamic analyses were carried out experimentally. Experimental organic Rankine cycle system was designed to operate in the temperature range of 78–90 °C using the waste heat in the lubricating oil. R134a was used as the working fluid in the prototype organic Rankine cycle system. The thermal efficiency, turbine expansion ratio and turbine power of the prototype organic Rankine cycle system were determined depending on different waste heat source temperatures and working fluid volumetric flow rates. According to experimental results for prototype organic Rankine cycle system, the highest thermal efficiency, turbine expansion ratio and turbine power are 6.84%, 1.94 and 1.22 kW, respectively, at a waste heat source temperature of 86.5 °C and volumetric flow rate of working fluid is 4.7 L/min.