Investigations on an organic Rankine cycle system coupled with a trilateral cycle using quasi two stage single screw expander

The waste heat of internal combustion engines mainly come from exhaust gas and cooling water. Usually, the exhaust gas can be recovered and utilized by organic Rankine cycle (ORC), and it is hard for simple ORC to recovery heat from exhaust gas and cooling water simultaneously. An ORC system coupled with a trilateral cycle was proposed. Compared with a single loop ORC system, it can improve the exergy recovery efficiency of waste heat by absorbing both the waste heat from the cooling water and the exhaust gas from internal combustion engines. The expander is a key component of the system. In order to adapt to the new system and alleviate the problem of under expansion, a quasi two stage expansion single screw expander is used. It is found that the exergy recovery efficiency of waste heat can be increased by 2.81%-5.19% and the temperature of organic fluid at the expander outlet can be decreased by 31.23 degrees C-40.53 degrees C compared to a single loop system under the exhaust gas temperature of 300 degrees C and the cooling water temperature of 95 degrees C.