Deterioration in heat transfer of endothermal hydrocarbon fuel

Abstract

Numerical studies under supercritical pressure are carried out to study the heat transfer characteristics in a single-root coolant channel of the active regenerative cooling system of the scramjet engine, using actual physical properties of pentane. The relationships between wall temperature and inlet temperature, mass flow rate, wall heat flux, inlet pressure, as well as center stream temperature are obtained. The results suggest that the heat transfer deterioration occurs when the fuel temperature approaches the pseudo-critical temperature, and the wall temperature increases rapidly and heat transfer coefficient decreases sharply. The decrease of wall heat flux, as well as the increase of mass flow rate and inlet pressure makes the starting point of the heat transfer deterioration and the peak point of the wall temperature move backward. The wall temperature increment induced by heat transfer deterioration decreases, which could reduce the severity of the heat transfer deterioration. The relational expression of the heat transfer deterioration critical heat flux derives from the relationship of the mass flow rate and the inlet pressure.

Numerical Study on Heat Transfer Deterioration of Supercritical n-Decane in Horizontal Circular Tubes

“…The previous studies of deterioration phenomena in heat transfer to supercritical fluids indicated that: at a certain inlet temperature, the onset of HTD depends on the combined effects of pressure, mass flux and heat flux [9,15,16,30,31]. For supercritical inorganic substances, such as water and carbon dioxide, Yamagata et al [30], Styrikovich et al [31], Kim et al [9] developed respectively a series of corrections for critical heat flux of HTD, and concluded that it was only related to the mass flux.…”

“…For supercritical inorganic substances, such as water and carbon dioxide, Yamagata et al [30], Styrikovich et al [31], Kim et al [9] developed respectively a series of corrections for critical heat flux of HTD, and concluded that it was only related to the mass flux. However, the related studies for organic substances, including the methane [15] and pentane [16], have also been conducted by Urbano et al [15] and Zhou et al [16], both of which further considered the effect of pressure. The details of these empirical expressions are in Table 2.…”

“…So far, very few studies about HTD of supercritical hydrocarbon fuels have been reported in the open literature [11][12][13][14][15][16][17][18]. Wang et al [11] and Hua et al [12] performed a numerical study of supercritical turbulent heat transfer of methane [11] and n-heptane [12] inside a horizontal miniature tube, respectively.…”

“…Results indicated that the heat transfer performances of both were good under a higher pressure, but the HTD could occur once the wall temperature reached the pseudo-critical temperature due to a rapid decrease in the volumetric heat capacity when the pressure was close to the corresponding critical pressure. Urbano et al [13][14][15], Zhou et al [16] carried out operational parametric numerical studies of the HTD in supercritical light hydrocarbon fuels, including the methane [13][14][15] and pentane [16], in horizontal circular channels. Moreover, critical conditions for the occurrence of HTD were developed [15,16].…”

“…Urbano et al [13][14][15], Zhou et al [16] carried out operational parametric numerical studies of the HTD in supercritical light hydrocarbon fuels, including the methane [13][14][15] and pentane [16], in horizontal circular channels. Moreover, critical conditions for the occurrence of HTD were developed [15,16]. Hitch and Karpuk [17] studied experimentally the supercritical convective heat transfer of JP-7 aviation kerosene in vertical circular tubes, and they observed deteriorated heat transfer along with significant temperature and pressure oscillations, when the reduced pressure (p/pc) was below 1.5 and the wall temperature was over the pseudo-critical temperature.…”