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ABSTRACT
In this article, the heat transfer performance of a syngas cooler with membrane helical-coil heat exchanger was numerically studied. A method of combining piecewise simulation and full-scale simulation was proposed, and the influence of fly ash was considered. The models and the proposed method were validated by comparing simulation results with data from industrial test. The simulation results show that radiation accounts for 10–20% of the total heat transfer in the syngas cooler. The surface of inner channel is characterized with high convective heat-transfer coefficient and heat flux. In addition, the quality of produced steam could be significantly enhanced as the heat exchanger of upper group was changed from evaporating surface to superheating surface, and the cooling performance for syngas was hardly affected.
Nomenclature
| A | = | area, m2 |
| D | = | diameter of center line for helical-coil, mm |
| d0 | = | external diameter of tube, mm |
| di | = | internal diameter of tube, mm |
| h | = | convective heat-transfer coefficient, W/(m2 · K) |
| h0 | = | h at outside of helical coil, W/(m2 · K) |
| hi | = | h at innerside of helical coil, W/(m2 · K) |
| L | = | length of heat exchanger, mm |
| m | = | amount of tube for a membrane helical coil |
| Pc | = | perimeter of cross section, mm |
| q | = | heat flux, W/m2 |
| s1 | = | screw pitch, mm |
| T | = | temperature, K |
| T0 | = | inlet temperature, K |
| tf0 | = | local syngas temperature, K |
| tfi | = | local working medium temperature, K |
| tw0 | = | local wall temperature, K |
| ΔT | = | temperature difference, K |
| Greek symbols | = | |
| δ | = | thickness of the fins, mm |
Nomenclature
| A | = | area, m2 |
| D | = | diameter of center line for helical-coil, mm |
| d0 | = | external diameter of tube, mm |
| di | = | internal diameter of tube, mm |
| h | = | convective heat-transfer coefficient, W/(m2 · K) |
| h0 | = | h at outside of helical coil, W/(m2 · K) |
| hi | = | h at innerside of helical coil, W/(m2 · K) |
| L | = | length of heat exchanger, mm |
| m | = | amount of tube for a membrane helical coil |
| Pc | = | perimeter of cross section, mm |
| q | = | heat flux, W/m2 |
| s1 | = | screw pitch, mm |
| T | = | temperature, K |
| T0 | = | inlet temperature, K |
| tf0 | = | local syngas temperature, K |
| tfi | = | local working medium temperature, K |
| tw0 | = | local wall temperature, K |
| ΔT | = | temperature difference, K |
| Greek symbols | = | |
| δ | = | thickness of the fins, mm |