A numerical study of heat transfer enhancement by helically corrugated tubes in the intermediate heat exchanger of a very-high-temperature gas-cooled reactor

Abstract

We numerically investigate heat transfer enhancement by helically corrugated tubes (HCTs) in the intermediate heat exchanger (IHX) of a very-high-temperature gas-cooled reactor (VHTR). A comparison with heat transfer in a smooth tube shows that HCTs have better heat transfer over the full IHX temperature range. The helical corrugations strengthen the intensity of the turbulence and create rotational flow, which better mixes the fluid and improves the synergy between the velocity field and the temperature gradient field. The effects of tube structural parameters and fluid physical properties on the Nusselt number (Nu), friction factor, and performance evaluation criterion (PEC) were also analyzed. The corrugations have optimal heights for the maximum Nu and PEC. Nu decreases as the corrugation pitch increases, whereas the PEC shows the opposite trend. The best heat transfer enhancement is 1.69 for e/d = 0.03 and p/d = 0.4, and the best overall performance is 1.13 for e/d = 0.01 and p/d = 0.8, both of which are in the high-temperature region.