Heat transfer deterioration in upward and downward pipe flows of supercritical n-decane for actively regenerative cooling
Introduction
Hypersonic vehicles are considered as a new aerial combat platform due to perfect stealth, a high Mach number flight and a wide range of strikes. The scramjet, which uses a hydrocarbon fuel as a propellant, is widely regarded as the core component of hypersonic vehicles [1]. The heat load of the combustor increases sharply due to the action of supersonic combustion and aerodynamic heating. The temperature and heat flux at a Mach number of 8 are 4000 K, 10–20 MW/m2, respectively, and the temperature exceeds the limits of existing materials [2]. An active regenerative cooling system can perfectly solve this problem [[3], [4], [5]] and the hydrocarbon fuel, e.g., RP-3 is used as a refrigerant in cooling channels. Generally, the critical pressure of the hydrocarbon fuel, e.g., RP-3, is 2–3 MPa and these always work at supercritical condition due to the operating pressures of 3.0–7.0 MPa of the combustor [6,7]. The thermophysical properties of supercritical hydrocarbon fuels change drastically and abnormal heat transfer phenomena can be observed such as a heat transfer deterioration (HTD) [[8], [9], [10], [11]]. Thus a large number of research works has paid attention to the convection heat transfer characteristics of supercritical hydrocarbon fuels. Because the components of hydrocarbon fuels are numerous and it is not realistic to consider them all in numerical simulations. Thus, surrogate models of hydrocarbon fuels are receiving much more attention [[12], [13], [14]]. In this work, supercritical n-decane is considered to be the refrigerant in the cooling channels of the active regenerative cooling system.
In addition to the studies on supercritical hydrocarbon fuels, supercritical water and carbon dioxide (CO2) in pipes with different types and orientations, i.e., vertical [15,16], horizontal [17,18] and helically coiled [19,20] pipes have also attracted attention, in particular for supercritical CO2, which has been poven to be a promising working fluid to be used in heat-to-power systems [[21], [22], [23]]. An abnormal heat transfer phenomenon can be found collectively in the thermal performance of these supercritical fluids. Fu et al. [24] and Jiang et al. [25] experimentally studied the different influence factors on the heat transfer of supercritical RP-3 and carbon dioxide such as system pressure, heat flux, mass flow rate, flow direction, etc. They reported that the sharp variation of the thermophysical properties plays an important role in the deteriorated heat transfer zone. Furthermore, Pioro et al. [26] deemed that the occurrence of the HTD can be accurately evaluated by one correlation. Li et al. [27] used the Shear-Stress Transport (SST) k-ω model to investigate the flow and heat transfer of supercritical water flowing in internally ribbed tubes. They reported that ribbed geometries hardly work but mixed ones play an important role by suppressing the buoyance force. Jackson [28] studied the flow and heat transfer in the presence of a buoyance force in a vertical tube and found that the forced convection turns into free convection with an increase of the buoyancy force. He et al. [29] experimentally researched the heat transfer of supercritical R245fa flowing vertically upward in a circular tube and it was observed that the phenomenon of heat transfer deterioration appeared at moderate heat and mass fluxes. Liao and Zhao [30] numerically explored laminar convection of CO2 in a vertical mini/micro tube and it was revealed that the buoyancy effect plays an important role in a small tube even for high Reynolds numbers. Bovard et al. [31] numerically investigated the heat transfer of supercritical CO2 and water and it was demonstrated that the increase of mass flux and operating pressure can decrease the effect of thermal-induced acceleration and buoyance force. These conclusions are consistent with Ref. [32]. Pucciarelli et al. [33] used LES (Large Eddy Simulation) to analyse the coupling effect of fluid heat transfer and wall heat conduction. It was suggested that the function of wall heat conduction should be considered explicitly. Tao et al. [34] proved that the buoyancy, density fluctuation and variation profoundly influence the accuracy of turbulence models. By modifying the LS (Launder-Sharma) model, the precision was improved by 41% compared to the experimental data. Kline et al. [35] experimentally explored the onset of HTD for CO2 flowing upward in electrically heated vertical tubes and the minimum heat flux was given. Jaromin and Anglart [36] investigated heat transfer of supercritical water in a vertical tube at deteriorated conditions and they also found that the wall temperature is greatly affected by the Prandtl number. Sun et al. [37] proposed a prediction model based on artificial neural network (ANN) to predict the heat transfer characteristics under various conditions and the results revealed that the model was capable of capturing the underlying heat transfer mechanism compared to traditional heat transfer correlations.
Through the above-mentioned literature survey, the parametrical variation, buoyancy effect, heat transfer correlation, heat transfer of enhanced structures, prediction models of heat transfer deterioration, modifications of the turbulence models on the abnormal heat transfer of supercritical fluids were widely studied. However, the mechanism of heat transfer deterioration is still unclear and this point was confirmed in Ref. [38]. In this context, the motivation here is to study the fundamental mechanism of heat transfer deterioration. It is well known that the effect of the flow field on the temperature field is very strong but a more detailed analysis of the flow field was not mentioned in the open literature. In this paper, the information of flow behaviour is used to illustrate the heat transfer characteristics, since the velocity distribution and flow structure demonstrate the heat transfer intensity in some certain areas, and the velocity fields and velocity gradients are used to indicate the global velocity structures and velocity trends, respectively. The velocity vector is applied to show the flow direction and the effect of secondary flow on the abnormal heat transfer, particularly for heat transfer deterioration, is also explained.
Section snippets
Active regenerative cooling
As described above, the active regenerative cooling technique of interest to the present work is regarded as a particularly effective approach for absorbing the combustor-generated heat as shown in Fig. 1. The hydrocarbon fuel firstly flows into channels and the heat in the combustor wall is taken up by the hydrocarbon fuel. The heated fuel inters the combustion chamber to participate in the combustion and generate thrust. In addition, heated fuel is used as a heat source in the power
Thermophysical properties of n-decane
Before the numerical calculations are conducted, the physical properties of the supercritical fuel should be determined and these data can be calculated by NIST (National Institute of Standards and Technology) [48]. The variations of the thermophysical properties of n-decane with the change of fluid temperature can be found in Refs. [49,50] and are also plotted in Fig. 3. Herein, the function of piecewise-linear in the commercial software Fluent was applied and 30 points were embedded. It
Heat transfer partitions
Fig. 6 shows how the inner wall temperature is changing along the flow direction for the upward-flowing and downward-flowing cases. There is a large difference between the two cases in terms of the inner wall temperature and this means that the heat transfer behaviour is inconsistent for different flow directions. For the upward-flowing case, an HTD (a typical form of heat transfer) can be observed. Generally, the heat transfer can be separated in the following regions: inlet region, normal
Conclusions
In order to cool effectively the combustion chambers of scramjets, turbulent flows of supercritical n-decane are used to absorb the heat in cooling channels. Abnormal flow and heat transfer behaviour is always observed in such flows due to the dramatic variation of thermophysical properties of supercritical fuels, particularly near the pseudo-critical point. To understand the physical mechanisms of unconventional flow and heat transfer, the SST k-ω and RNG k-ϵ turbulence models were used to
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgments
This work was sponsored by the National Natural Science Foundation of China (51676163), the National 111 Project (Grant No. B18041), the Fundamental Research Funds of Shenzhen City (JCYJ20170306155153048), and the Innovation Foundation for Doctor Dissertation of Northwestern Polytechnical University (Grant No. CX202029), and was financially supported by the China Scholarship Council (CSC) who gave Mr. Y. Li the opportunity to perform part of his PhD studies at Lund University. The work was also
References (54)
- et al.
Experimental investigation of convective heat transfer of hydrocarbon fuels at supercritical pressures within rotating centrifugal channel
Appl. Therm. Eng.
(2019) - et al.
The comprehensive study on hydrocarbon fuel pyrolysis and heat transfer characteristics
Appl. Therm. Eng.
(2017) - et al.
Conjugate heat transfer, endothermic fuel pyrolysis and surface coking of aviation kerosene in ribbed tube at supercritical pressure
Int. J. Therm. Sci.
(2018) - et al.
Effects of hydrogen active cooling on scramjet engine performance
Int. J. Hydrogen Energy
(1996) - et al.
A brief review on convection heat transfer of fluids at supercritical pressures in tubes and the recent progress
Appl. Energy
(2016) - et al.
Heat transfer behaviour of supercritical nitrogen in the large specific heat region flowing in a vertical tube
Energy
(2017) - et al.
Asymmetric heating and buoyancy effects on heat transfer of hydrocarbon fuel in a horizontal square channel at supercritical pressures
Aero. Sci. Technol.
(2019) - et al.
Effect of channel aspect ratio on chemical recuperation process in advanced aeroengines
Energy
(2017) - et al.
Investigation of buoyancy-enhanced heat transfer of supercritical CO2 in upward and downward tube flows
J. Supercrit. Fluids
(2018) - et al.
Experimental study of flow acceleration and buoyancy on heat transfer in a supercritical fluid flow in a circular tube
Nucl. Eng. Des.
(2010)
Experimental investigation on validity of buoyancy parameters to heat transfer of CO2 at supercritical pressures in a horizontal tube
Exp. Therm. Fluid Sci.
Experimental and numerical investigation on heat transfer characteristics of supercritical CO2 in the cooled helically coiled tube
Int. J. Heat Mass Tran.
Mixed convective heat transfer of CO2 at supercritical pressures flowing upward through a vertical helically coiled tube
Appl. Therm. Eng.
Parametric optimisation of a combined supercritical CO2 (S-CO2) cycle and organic Rankine cycle (ORC) system for internal combustion engine (ICE) waste-heat recovery
Energy Convers. Manag.
Combined supercritical CO2 (SCO2) cycle and organic Rankine cycle (ORC) system for hybrid solar and geothermal power generation: Thermoeconomic assessment of various configurations
Renew. Energy
Experimental investigation on convective heat transfer of supercritical RP-3 in vertical miniature tubes with various diameters
Int. J. Heat Mass Tran.
Experimental and numerical investigation of convection heat transfer of CO2 at supercritical pressures in a vertical tube at low Reynolds numbers
Int. J. Therm. Sci.
Heat transfer to supercritical fluids flowing in channels—empirical correlations (survey)
Nucl. Eng. Des.
Effects of rib geometries and property variations on heat transfer to supercritical water in internally ribbed tubes
Appl. Therm. Eng.
Models of heat transfer to fluids at supercritical pressure with influences of buoyancy and acceleration
Appl. Therm. Eng.
Experimental investigation of heat transfer to supercritical R245fa flowing vertically upward in a circular tube
Int. J. Heat Mass Tran.
Numerical investigation of heat transfer in supercritical CO2 and water turbulent flow in circular tubes
J. Supercrit. Fluids
On the effect of conjugate heat transfer on turbulence in supercritical fluids: results from a LES application
Ann. Nucl. Energy
Correction of low-Reynolds number turbulence model to hydrocarbon fuel at supercritical pressure
Aero. Sci. Technol.
Onset of heat transfer deterioration in vertical pipe flows of CO2 at supercritical pressures
Int. J. Heat Mass Tran.
A numerical study of heat transfer to supercritical water flowing upward in vertical tubes under normal and deteriorated conditions
Nucl. Eng. Des.
Thermal characteristics of in-tube upward supercritical CO2 flows and a new heat transfer prediction model based on artificial neural networks (ANN)
Appl. Therm. Eng.
Cited by (25)
Three-dimensional CFD model for the coking of supercritical n-decane in circular and elliptical tubes
2024, Chemical Engineering ScienceComparison of heat transfer performance between liquid metal and aviation kerosene in the wall cooling channel of aero-engine
2024, International Journal of Heat and Mass TransferExperimental investigation of heat transfer and structure optimization for regenerative cooling channels using n-decane
2024, International Journal of Heat and Mass TransferEffects of horizontal self-rotation on flow and heat transfer of supercritical n-decane in regenerative circular/rectangular cooling channels
2024, International Journal of Heat and Fluid FlowThermal-mechanical coupling analysis of the ribbed channels in regenerative cooling
2024, International Journal of Heat and Mass Transfer