Numerical Study on Enhanced Heat Transfer of Downhole Slotted-Type Heaters for In Situ Oil Shale Exploitation.

Abstract

In order to improve the flow state of the heater shell side and enhance the performance evaluation of the heater, this paper proposes a perforated plate-type heater model. Based on Fluent, numerical studies are conducted on the heat transfer performance and shell-side fluid flow characteristics of a perforated plate-type heater. The variations of the heat transfer factor Nu, friction factor f, and evaluation parameter Nu/f1/3 are analyzed for different helix angles β and ratios of the long and short semiaxes of the circular holes on the heating plate under different Reynolds numbers Re. The results reveal that under the same shell-side Reynolds number Re, the heat transfer factor Nu shows an increasing trend with the increase in the proportion of the helix angle β. The heat transfer factor Nu for the heating plate with the hole shape ratio a/b = 1 does not exhibit significant improvement compared to hole shape ratios a/b = 0.8 and a/b = 0.6, but it increases by 4.87 to 7.07% compared to the hole shape ratio a/b = 0.4 in the perforated plate-type heater. On the other hand, the friction factor f decreases as the helix angle β and the ratio of hole shapes on the heating plate increase. The lowest friction factor f is observed for the helix angle β of 25° and the hole shape ratio a/b = 1 in the perforated plate-type heater. When the helix angle β is 25° and the hole shape ratio is a/b = 1, the evaluation parameter Nu/f1/3 reaches its highest value, indicating the optimal overall performance of the perforated plate-type heater.