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The high-performance supercritical CO2 heat exchanger is the key core equipment to realize the efficient and compact S-CO2 Brayton cycle system. S-CO2 has a low heat transfer coefficient in the smooth channel, and seeking high heat transfer performance and low-resistance heat transfer structure is the key to the development of efficient and compact heat exchangers. Five-axis EDM was used to fabricate the straightly ribbed tube, and the heat transfer behaviors of S-CO2 in the four-headed straight rib tube was experimentally studied, the effect of flow parameters on the heat transfer characteristics of the straight rib tube was systematically analyzed, and the difference in the heat transfer performance between the straight rib tube and the smooth tube was quantitatively evaluated. The influence of structural parameters on the enhanced heat transfer and resistance characteristics was studied by numerical simulation method, and the optimal straight rib tube structure was obtained. The results show that increasing the pressure and mass flow rate can reduce the wall temperature, improve the convective heat transfer coefficient, and the average heat transfer capacity of straight rib tube is about 1.96 times that of smooth tube. Compared with smooth tubes, straight ribbed tubes can effectively delay the occurrence of heat transfer deterioration, the ability to delay the occurrence of heat transfer deterioration by using straightly-ribbed tubes is increased by 0.3~1.8 times. When the fixed rib width W=0.5 mm and the rib height H=2.5 mm, the PEC is the best, and the value of PEC is1.58. However, the fixed rib height is H=0.5 mm, ε=0.33, and PEC of the straightly-ribbed tube is the best, with the value of PEC is 1.22.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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