Thermodynamic Analysis of Heat Absorption Temperature Difference of Supercritical CO2 Recompression Cycle

doi:10.12096/j.2096-4528.pgt.260204

Abstract

Abstract:

Objectives To reduce the amount of molten salt in molten salt thermal energy storage tower-type solar thermal power generation systems, it is necessary to increase the heat absorption temperature difference of supercritical CO₂, thereby enhancing the heat absorption and release temperature difference of the molten salt, therefore, modeling and analysis are carried out for the endothermic temperature difference of supercritical CO₂. Methods A supercritical CO₂ recompression cycle model is established in EBSILON, and combined with theoretical derivation to analyze the heat absorption temperature difference of the main heater (ΔT₁) and the reheater (ΔT₂). A combination of theoretical analysis and simulation is employed to investigate in detail the effects of parameters such as the maximum cycle temperature, minimum cycle temperature, total cycle pressure ratio, high-pressure turbine pressure ratio, and shunt coefficient on the heat absorption temperature difference of supercritical CO₂. Results Increasing the maximum cycle temperature, and decreasing the minimum cycle temperature, total cycle pressure ratio, high-pressure turbine pressure ratio, and shunt coefficient can increase the main heater heat absorption temperature difference ΔT₁. Increasing the maximum cycle temperature, total cycle pressure ratio, and high-pressure turbine pressure ratio can increase the reheater heat absorption temperature difference ΔT₂. When the maximum cycle temperature increases, both ΔT₁ and ΔT₂ increase. Data show that when the maximum cycle temperature rises from 400 ℃ to 700 ℃, ΔT₁ increases from 122.13 ℃ to 182.81 ℃, and ΔT₂ increases from 54.47 ℃ to 67.23 ℃. Conclusions By adjusting cycle parameters, the heat absorption temperature difference of the supercritical CO₂ recompression cycle can be effectively improved, thereby optimizing system performance. The results provide a theoretical basis for further optimization of the supercritical CO₂ recompression cycle.

Key words: supercritical CO₂ recompression cycle, main heater, heat absorption temperature difference, reheater, cycle parameters, solar thermal power generation, molten salt

CLC Number:

TK 01

Xiaofei ZHEN, Li ZHANG, Yongheng ZHANG. Thermodynamic Analysis of Heat Absorption Temperature Difference of Supercritical CO₂Recompression Cycle[J]. Power Generation Technology, 2026, 47(2): 266-273.

Figures/Tables 9

Fig. 1 Structural diagram of supercritical CO2 recompression cycle

Fig. 2 Temperature-entropy diagram of supercritical CO2 recompression cycle

Tab. 1 Basic design parameters of power cycle

参数	数值	参数	数值
主汽温度/℃	550	高压透平定熵效率/%	90
再热温度/℃	550	低压透平定熵效率/%	90
主汽压力/MPa	30	再压缩机定熵效率/%	85
循环增压比	3.90	主压缩机定熵效率/%	85
再压缩机进口温度/℃	32	高温回热器效率/%	86
分流系数/%	33.1	低温回热器效率/%	86

Tab. 2 Comparison between model results and literature[7] data

参数	工况1	工况2
主汽/再热温度/℃	550	550
主压缩机进口温度/℃	32	32
主汽压力/MPa	30	20
循环增压比	3.90	2.64
分流系数	0.331	0.312
文献[7]循环效率/%	44.83	41.92
模型循环效率/%	44.16	42.57
循环效率相对误差/%	1.49	1.53

Fig. 3 Effect of maximum cycle temperature on heat absorption temperature difference

Fig. 4 Effect of minimum cycle temperature on heat absorption temperature difference

Fig. 5 Effect of total cycle pressure ratio on heat absorption temperature difference

Fig. 6 Effect of high-pressure turbine pressure ratio on heat absorption temperature difference

Fig. 7 Effect of shunt coefficient on heat absorption temperature difference

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Thermodynamic Analysis of Heat Absorption Temperature Difference of Supercritical CO₂Recompression Cycle

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