Thermodynamic Analysis of Supercritical Carbon Dioxide Cycle for Internal Combustion Engine Waste Heat Recovery

Abstract

Waste heat recovery of the internal combustion engine (ICE) has attracted much attention, and the supercritical carbon dioxide (S-CO2) cycle was considered as a promising technology. In this paper, a comparison of four S-CO2 cycles for waste heat recovery from the ICE was presented. Improving the exhaust heat recovery ratio and cycle thermal efficiency were significant to the net output power. A discussion about four different cycles with different design parameters was conducted, along with a thermodynamic performance. The results showed that choosing an appropriate inlet pressure of the compressor could achieve the maximum exhaust heat recovery ratio, and the pressure increased with the rising of the turbine inlet pressure and compressor inlet temperature. The maximum exhaust heat recovery ratio for recuperation and pre-compression of the S-CO2 cycle were achieved at 7.65 Mpa and 5.8 MPa, respectively. For the split-flow recompression cycle, thermal efficiency first increased with the increasing of the split ratio (SR), then decreased with a further increase of the SR, but the exhaust heat recovery ratio showed a sustained downward trend with the increase of the SR. For the split-flow expansion cycle, the optimal SR was 0.43 when the thermal efficiency and exhaust heat recovery ratio achieved the maximum. The highest recovery ratio was 24.75% for the split-flow expansion cycle when the total output power, which is the sum of the ICE power output and turbine mechanical power output, increased 15.3%. The thermal performance of the split-flow expansion cycle was the best compared to the other three cycles.

Performance comparison of organic Rankine cycles integrated with solar based combined cycle: A thermodynamic and exergoenvironmental analysis

“…After the compressor-2 a part of sCO 2 stream goes to LTR (state 4-10) and then passing through the HTR (state 10-11) it was expanded in low temperature turbine (LT) (state 11-12) and remaining part of the stream goes to HEX1 (state 4-5), through the HEX2 the waste heat was absorbed by the ORC by working fluid R1234yf (state . This stream was expanded through the organic turbine (OT) (state 13-14) and passing through the condenser (state [14][15] where heat was rejected it was passed by the pump (state [15][16]. Finally, similarly this repeats again and again.…”

“…They also proposed future studies on the merging of two cycles. Yu et al 16 investigated four configurations of CO 2 cycle such that recompression cycle, flow split recompression cycle, pre-compression and simple recuperated cycle to recover the waste heat from internal combustion engine. In addition, the waste heat recovery ratio and thermal efficiency of the four systems were calculated.…”

Thermodynamic Analysis of a Novel Combined Supercritical Co2 and Organic Rankine Cycle

“…[9]. Yu et al, They said that the internal combustion engine (ICE) with waste heat recovery and S-CO2 cycle is considered a promising technology [10]. Casanova et al, Transcritical carbon dioxide cycles and the Rankine cycle have arised as alternatives for power generation in lowtemperature applications.…”

A visualization study on flat plate heat pipe (FPHP)

“…Flat plate heat pipes (FPHP) are widely used in the field of thermal applications. 1–3 The heat dissipation of a heating element is still a challenge, for which the heat generation is increasing with technological development. The method of forced air circulation for cooling and heat dissipation cannot meet the requirements of heating elements with high heat flux.…”