Increase In Mass Flow Rate Research Articles

Innovative cinque rib-roughened stimulators on performance improvement in triangular channel solar air heater

Abstract Present study investigates application of cinque-faced rib roughening to improve the efficiency of solar air heaters (SAHs). Research focuses on a novel design, the cinque-faced rib-roughened triangular channel SAH (CFRTCSAH), which incorporates five-faced wire ribs on the absorber plate’s underside. By breaking down the laminar sublayer and enhancing flow separation and reattachment, - ribs significantly enhance heat transfer. It establishes a comprehensive theoretical model to analyze the thermal and hydraulic performance of the CFRTCSAH. The study considers the influence of parameters such as relative roughness pitch (P/e) and relative roughness height (e/Dh) on thermal efficiency and heat removal factor. The results demonstrate that the CFRTCSAH achieves remarkable thermal efficiency, reaching up to 80.7% under optimal roughness parameters (P/e = 12, e/Dh = 0.05). It is found that an increase in mass flow rates positively impacts thermal efficiency but should not exceed 0.09 kg/s for maximum effective efficiency. Additionally, it has observed that the CFRTCSAH performs most effectively when the relative roughness pitch ratio (P/e) is set to 12. A higher relative roughness height (e/Dh) promotes convective heat transfer, enhancing thermal performance, especially at lower mass flow rates. Conclusion presents a novel approach to improving the thermal performance of SAHs by introducing cinque-faced rib roughening. The CFRTCSAH design exhibits significant potential for achieving high thermal efficiency and can contribute to more efficient solar energy utilization in various applications. These findings offer valuable insights for the development of SAHs, promoting sustainable and energy-efficient technologies.

Mass flow rate prediction of a direct-expansion ice thermal storage system using R134a based on dimensionless correlation and artificial neural network

Accurately predicting the refrigerant mass flow rate through the electronic expansion valve (EEV) is crucial for improving the system's performance and achieving intelligent control. However, the refrigerant mass flow rate model applicable to the direct-expansion ice thermal storage (DX-ITS) system for a wide range of flow rates is rare in the open literature. In this study, Buckingham-π theorem and artificial neural network (ANN) are adopted to predict the refrigerant mass flow rate through the EEV of the DX-ITS system using R134a. The dimensionless π-groups and optimal number of neurons in hidden layers of ANN model are obtained. The obtained ANN model shows good accuracy, and over 95.7 % of the predicted data are within the 15 % error band. Results indicate that the EEV outlet pressure has a significant impact on the refrigerant mass flow rate compared with the inlet pressure, the average increase in refrigerant mass flow rate is 43.76 kg/h with an outlet pressure increase of 0.05 MPa. Moreover, the refrigerant mass flow rate gently rises with the increase of superheat temperature under fixed EEV inlet and outlet pressure. On average, every 2 °C increase in superheat temperature leads to an approximately 3.98 kg/h increase in refrigerant mass flow rate.

Numerical and experimental analysis of instability in high temperature packed-bed rock thermal energy storage systems

Due to heat losses of preferential areas of packed-bed energy storage systems, transverse temperature variations may occur during the charging, discharging and standby processes. Furthermore, the heat losses of preferential areas of the storage tank cause a lower pressure drop in these areas resulting in an increased mass flow rate and further cooling, and thereby an enhanced transverse temperature variation, in a positive feedback loop – a phenomenon called instability. The transverse temperature variations may deteriorate the performance and thereby the economic feasibility of packed-bed energy storage systems. In this paper, numerical and experimental investigations of an air-based packed-bed rock thermal energy storage system for large-scale high temperature applications are presented. The objective of the study is to predict the instability and to analyze the effect of different standby durations and storage size on the instability of the air-based packed-bed system. Transient axisymmetric computational fluid dynamics models were developed for the standby and discharging processes of the packed-bed thermal energy storage systems. In addition, experimental investigations were carried out at a test facility located at Stiesdal Storage, Denmark, using magnetite rocks as heat storage material and air as heat transfer fluid. The results suggest that the numerical predictions are in good agreement with the test data. The instability phenomenon is found to increase with the standby duration, resulting in a maximum difference of 161 K between the maximum rock temperature and the outlet air temperature for a standby period of 10 h followed by a discharging process. Moreover, the results indicate that the maximum difference between the rock temperature and outlet temperature is 73 K and 56 K for a reduced-scale and a full-scale system (no standby period), respectively.

CFD Analysis of the Effect of Mass Flow Rate in a Shell and Tube Heat Exchanger Design

Heat exchangers are often found in the chemical process industry, but of all types of heat exchangers, the Shell and Tube Heat Exchanger (STHE) are the most used. The design of shell and tube heat exchangers are continually evolving because of it reduce production costs. A computational fluid dynamics (CFD) simulation was employed using SOLIDWORKS Flow Simulation version 2022 to model the effect of operating parameter such as the mass flow rate on the pressure drop, heat transfer coefficient and the turbulence intensity. The turbulence model adopted for the simulation was the k–ɛ turbulence model incorporating the boundary conditions. Three conditions were studied increasing both shell and tube side mass flow rate, maintaining either the shell or tube constant and then varying the other. The results obtained showed that an increase in mass flow rate have tremendous effect on the pressure drop, heat transfer and turbulence intensity.

Numerical study of a composite cooling method for hypersonic aircraft

Thermal protection is a crucial issue for a long-flying hypersonic aircraft. In this work, a composite cooling method is proposed and implemented on a hypersonic blunt cone. The composite cooling method combines impinging and convective cooling at the cone head with transpiration cooling employed downstream to produce an overall cooling effect of the cone. Using computational fluid dynamics, the influences of the cooling gas and different attack angles on the cooling effect are examined. The results indicate that the combined cooling method can effectively reduce the overall outer wall temperature of the cone. In particular, with the combined cooling method, an increase in mass flow rate of the cooling gas has been observed in numerical tests, which results in a decrease in the head temperature. The maximum temperature decrease can reach 77.0% on the wall when the mass flow rate of the cooling stream is 1.1 kg/m2 s. The cooling performance on the leeward side can be better than that on the windward side for a fixed cooling gas mass flow rate. This gap in cooling performance between the two sides can be further amplified by a larger attack angle. Quantitatively, when using the combined cooling method, the temperature difference between the windward and leeward sides increases from 106 to 270 K when the attack angle increases from 4° to 8°. The numerical results in this study could provide theoretical and statistical guidance for the design of novel active thermal protection methods for hypersonic aircraft.

Numerical study on heat transfer deterioration of n-decane during pyrolysis under supercritical pressure in a vertical tube

For accelerating hypersonic vehicles, it is important to understand the effects of various factors on heat transfer deterioration. The heat transfer characteristics of supercritical n-decane with pyrolysis were numerically simulated inside a vertical tube. The effects of flow direction, mass flow rate, heat flux, inlet temperature, and flight acceleration on the heat transfer characteristics were investigated. When the inlet temperature was relatively low or the fluid was decelerated vertically upward, a typical M-shaped velocity distribution was formed, indicating the heat transfer deterioration (HTD). Furthermore, the decrease in wall heat flux, as well as the increase in mass flow rate, inlet temperature and flight acceleration in the same direction as the flow makes the HTD gradually disappear. Finally, a new relationship was established between the heat flux and the flight acceleration and inlet temperature to determine critical heat flux under which HTD developed in the upward flow.

Numerical study for effect of injection parameters on reservoir: A case study for Lahendong, Indonesia

A single-flash cycle of thermodynamic model coupled with a reservoir of numerical model has been developed through the COMSOL Livelink module to investigate the impact of the geofluid mass flow rate and injection temperature on production temperature and net output power of the power cycle. The geothermal reservoir model was established by using a thermal–hydraulic–mechanical (THM) module in COMSOL Multiphysics. Moreover, the single-flash cycle of the thermodynamics model was constructed in MATLAB. The geothermal reservoir conditions of Lahendong, North Sulawesi, Indonesia was adopted to simulate the geothermal power plants’ actual operation. The results revealed that the variation in geofluid mass flow rate and injection temperature impacted production temperature and net output power. The production temperature considerably decreased with an increase in the geofluid mass flow rate. However, the difference in production temperature between geofluid mass flow rates of 50 kg/s and 250 kg/s at 1st and 30th years were 0.23 K and 0.41 K, respectively. The net output power differences were also 16.204 MW and 15.349 MW, respectively. Finally, increasing the injection temperature correspondingly led to an increase in production temperature and net output power, even though the increment did not exceed 1 K and 0.002 MW, respectively.

Experimental investigation on a rotating detonation combustor with the pulse operating frequency of 10 Hz

The rotating detonation rocket engine has certain advantages in propulsion performance and is expected to develop into a new type of attitude/orbit control power device. In this paper, an experimental investigation on the detonation propagation characteristics during the short-time pulse operating process of rotating detonation combustor (RDC) was performed. A 60-mm RDC was employed, and the H2 and oxygen-rich air were used as the reactant. The results show that the experiment can successfully achieve rotating detonation mode when the RDC is operating with a 10-Hz pulse frequency. With the increase of oxidizer mass flow rate, the velocity and pressure of the detonation wave will increase. The average propagation frequency of the detonation wave shows a trend of first increasing and then slightly decreasing as increasing the equivalence ratio. There is a large velocity fluctuation in the RDC pulse operation, and the stability of the detonation wave is significantly affected by the equivalence ratio. The propagation velocity and stability of the detonation wave can be improved by increasing the supply mass flow rate or equivalence ratio with a certain condition. When the equivalence ratio is larger than 0.7, the establishment time of the detonation wave is less than 1 ms, which can meet the requirement of the fast response when the RDC is applied to attitude control engine.

A numerical and experimental analysis of a novel highly-efficient water-based PV/T system

New materials and designs have been developed and proposed to enhance the thermal and electrical performance of photovoltaic-thermal (PV/T) systems in recent years. Despite the significant attention received by PV/T technology, the available PV/T modules are scarce due to complex system designs, environmentally unfriendly working fluids, and low thermal efficiency. In this paper, a highly efficient water-based PV/T system is proposed by combining an innovatively designed cooling system with a PV module. An experimental evaluation of the designed PV/T system was carried out in laboratory conditions. The test results of the PV/T system showed that when the inlet mass flow rate and temperature were 0.0458 kg/s and 11.90 °C, the PV/T system reached the maximum thermal efficiency of 96.47 ± 1.40 %. The increase in mass flow rate from 0.0042 kg/s to 0.0375 kg/s and the decrease in inlet temperature from 17.70 °C to 11.40 °C led to a 12 % improvement in thermal efficiency of the PV/T system showing that the inlet mass flow rate and temperature have a significant influence on thermal efficiency. The developed 3-D numerical model accurately estimated the outlet temperature of the PV/T system. A maximum of 3.43 % error occurred between the experimental results and model output.

Flow and heat transfer characteristics of water in eccentric micro annuli

Considering the few studies on eccentric micro annuli, in view of the extensive use of microchannels, experimental and numerical studies on the thermal–hydraulic performances are conducted. Results show that the flow is turbulent in the Reynolds number range of 992–3491. The velocity and temperature distributions at cross-section are nonuniform and two or four vortexes are formed. As the mass flow rate and heat flux increase, the friction factor decreases and the Nusselt number increases. As the eccentricity increases, the friction factor and Nusselt number decrease. When the buoyancy is negligible, the local Nusselt number for peripheral surface declines rapidly at first and then steadily declines. The larger mass flow rate and smaller eccentricity cause the quasi-stationary state local Nusselt number to occur early. When the buoyancy is not negligible, the local Nusselt number for peripheral surface drops quickly at first and then rises. The larger heat flux causes an increase in the local Nusselt number at a shorter heating length. The flow and thermal entropy production rates in most flow regions are small. The thermal entropy production rate far outweighs the flow entropy production rate. Finally, the correlations for the Nusselt number and friction factor are presented.

Heat transfer characteristics of R-1234yf, an eco-friendly alternative refrigerant in condenser for semiconductor chiller

This study aims to optimize a semiconductor chiller condenser that uses R-1234yf refrigerant, focusing on its flow pattern and heat transfer characteristics during condensation while considering the tube diameter. The heat transfer coefficient (HTC) decreases as the pressure of R-1234yf increases. This decline is attributed to changes in its physical properties, such as the density ratio between the liquid and gas phases and the thermal conductivity of the liquid phase, according to the change in saturation pressure. The HTC of R-1234yf increases with the mass flow rate (MFR) because the Reynolds number in the tube increases as MFR increases, enhancing heat transfer. Furthermore, the local condensation HTC (CHTC) of R-134a exceeds that of R-1234yf across the entire vapor quality range, primarily due to the higher liquid-phase density of R-1234yf. The correlations by Dobson–Chato [21] and Bashar et al. [10] were found to be suitable for predicting CHTC values for R-1234yf. The predicted values closely align with the experimental values, with an error range of less than ± 10 %, thus indicating that the correlations by Dobson–Chato and Bashar et al. can be directly applied to the design of condensers that use R-1234yf refrigerant.

Numerical Simulation of Immersed Liquid Cooling System for Lithium-Ion Battery Thermal Management System of New Energy Vehicles

Power batteries generate a large amount of heat during the charging and discharging processes, which seriously affects the operation safety and service life. An efficient cooling system is crucial for the batteries. This paper numerically simulated a power battery pack composed of 8 lithium-ion cells immersed in the coolant AmpCool AC-110 to study the effects of different coolants, different discharge rates, different coolant mass flow rates, different inlet temperatures and different inlet and outlet settings on the maximum temperature, the maximum temperature difference, the pressure drop, and the required pump power in the battery pack. Among the five coolants studied, W-E in water-based fluids has the best cooling effect, but because of high electric conductivity, it requires special considerations to avoid electric leakage. Increasing the mass flow rate of the coolant can significantly decrease Tmax and ΔTmax, but when the mass flow rate is already high, the decrease is limited and not obvious. Both Δp and the required pump power increase as the mass flow rate increases, and the required pump power increases faster. The inlet temperature will affect the physical properties of the coolant, and choosing the appropriate inlet temperature can not only decrease ΔTmax, but also decrease Δp and the required pump power in the battery pack. The range of 25~27 °C of the coolant AC-110 inlet temperature is recommended. For different inlet and outlet settings, the two-inlet two-outlet setting used in Case 7 has the best cooling effect, and the results indicate uniform distribution is very important to decrease temperature.

Influence of Powder Mass Flow Rates on Wear Resistance and Impact Toughness of Inconel 718 Surface Coatings

Optimum laser cladding processing parameters were obtained based on the study of various powder mass flow rates for the repair of 27SiMn steel parts using Inconel 718 powder. In this study, fusion coating process parameters were set according to the influence of powder mass flow rates on fusion coating properties. The cross-sectional microstructure, X-ray diffraction patterns, micro-hardness distribution, friction, wear properties, impact properties, and fracture morphology of the clad layers were investigated for the various process parameters. The results indicate that the volume fraction for the Ni3Fe phase increases and then decreases as the powder mass flow rate increases. The micro-hardness, friction properties, and impact properties of the samples followed the same trend as those of Ni3Fe. At powder mass flow rates up to 20 g/min, microstructures in the cladding layer tended to be uniform with microstructures with fine grains, and micro-hardness and impact toughness reached maximum values of 328.2 HV0.5 and 45.4 J/cm2, respectively, which show better mechanical properties and wear resistance.

Effect of water spray on tip leakage flow in a inlet stage of high-speed compressor

Water spray can reduce the inlet air temperature of the compressor inlet stage of the high-altitude high-speed turbine engine. In this paper, the Euler-Lagrange method is used to simulate the gas-liquid two-phase flow with droplet evaporation in NASA Stage 35. The effects of water spray on the heat and mass transfer characteristics of the stage, the tip leakage vortex structure, the unsteady characteristics of tip leakage flow and compressor performance are analyzed. The results show that the water spray increases the inlet mass flow and tip leakage flow rate of the stage, decreases the tip temperature. The inlet mass flow and tip leakage flow rate increase with the growth of inject mass flow rate and the decrease of droplet size. Water spray increases the scale of the main tip leakage vortex, and deflects the secondary leakage flow in the flow direction. Water spray increases the amplitude of pressure fluctuation at the blade tip. The frequency of pressure fluctuation at dry air condition is 0.2BPF, which decreases to 0.15BPF after water spraying. The leakage vortex weakens the strength of shock wave which causes a decline in the diffusing ability of blade; the leakage vortex is mixed with the main stream, resulting in a large aerodynamic loss. Although the injection of droplets increases the loss of tip leakage flow, it optimizes the performance of NASA stage 35 significantly. Spray increases the total pressure ratio of the R domain from 1.835 to 1.9; the total temperature ratio of the stage reduces from 1.225 to 1.203 and decreases the rotor loss coefficient from 0.12 to 0.08.

Numerical study of thermal-hydraulic and structural parameters effects on CHF in subcooled forced convection flow during external reactor vessel cooling

Advanced nuclear reactors employ External Reactor Vessel Cooling (ERVC) as a crucial measure to safeguard the structural integrity of the Reactor Pressure Vessel's (RPV) lower head and to confine molten material within it during severe accidents. The ERVC technique effectively mitigates severe accidents by efficiently dissipating decay heat from the molten pool located within the lower head, utilizing coolant flow boiling. The key determinant of the upper limit of ERVC cooling capability is primarily contingent on the Critical Heat Flux (CHF). In this study, flow boiling in downward heating curved flow channel under forced convection is numerically investigated using the Eulerian-Eulerian two-fluid model and realizable k-ε turbulence model. Compared with the experiment, the maximum deviation of numerically predicted CHF is less than 5%, indicating that the numerical method is reliable. A thorough analysis is conducted on the impact of variable structure and thermal-hydraulic operating conditions on CHF. The results indicate that as the coolant mass flow rate, system pressure, and inlet subcooling increase, the CHF exhibits a corresponding increase. The CHF increases by 56.6% when the mass flow rate increases from 400 to 1000 kg/(m2·s). The CHF at the pressure of 0.3 MPa is 16% higher than that of 0.1 MPa. The CHF increases from 1.14 to 1.84 MW/m2 as the inlet subcooling escalates from 10 to 20 K, with a 60% growth rate, while the CHF increases to 2.03 MW/m2 when the inlet subcooling increases from 20 to 50 K, with a 10.33% increase. The maximum difference in CHF for the three flow channel widths (120, 150, and 170 mm) is only 1.7%, indicating that the influence of flow channel widths is insignificant. This study can provide theoretical guidance for the design and optimization of ERVC in advanced nuclear reactors.

Fast Calculation of Supercritical Carbon Dioxide Flow, Heat Transfer Performance, and Mass Flow Rate Matching Optimization of Printed Circuit Heat Exchangers Used as Recuperators

Printed circuit heat exchangers (PCHEs) are widely used as recuperators in the supercritical carbon dioxide (S-CO2) Brayton cycle design. The variation of heat sources will have a great impact on the heat transfer effect of the recuperator. It is of interest to study the fast calculation of flow and heat transfer performance of PCHEs under different operating conditions to obtain the optimal comprehensive performance and provide guidance for the operation control strategy analysis. Herein, a fast calculation method is established through a one-dimensional model of a PCHE based on Modelica. The effects of working medium mass flow rate and inlet temperature on the flow and heat transfer process are analyzed from the three aspects of heat transfer rate, flow pressure drop, and comprehensive performance, and the mass flow rate matching optimization is realized. The results show that increased mass flow rate increases heat transfer rate and flow pressure drop. The efficiency evaluation coefficient (EEC) has a maximum value at which the mass flow rate values of the cold and hot channels are best matched, and the comprehensive performance is optimal. When the mass flow rate of the heat channel is 4.8 g/s, the maximum EEC is 1.42, corresponding to the mass flow rate of the cold channel, 4.2 g/s. Compared with the design condition, the heat transfer rate increases by 62.1%, and the total pump power increases by 14.2%. When the cold channel inlet temperature increases, EEC decreases rapidly, whereas EEC increases when the hot channel inlet temperature increases. The conclusions can provide theoretical support for the design and operation of PCHEs.

Numerical and experimental investigation on condensation inside a turbine designed for an 100 kW polymer electrolyte membrane fuel cell system

This work presents mathematical modelling of moist air condensation process in a fuel cell turbine. A condensation model based on the classical nucleation theory and the Hertz–Knudsen droplet growth model is established. The numerical approach is validated through experimental results of the MS nozzle and a fuel cell turbine, and the simulation fits the experimental data well. Influences of inlet temperature and pressure on condensation process in the turbine is examined. Results show that increase of inlet temperature apparently weakens condensation and inlet heating can be realized by arranging a gas-to-gas heat exchanger in the air supply subsystem without consuming additional energy. Moreover, at the same mass flow rate increase of inlet pressure reduces the expansion ratio, thereby curbing the condensation. Compared with the matching scheme of a bypass valve, turbocharger matching with a back-pressure valve allows higher inlet pressure to be achieved and can effectively suppress the condensation.

Experimental study on heat transfer and flow pattern transition for R1233zd/FC72 mixtures across tube bundles

An experimental investigation was conducted to study the heat transfer and two-phase flow patterns of pure R1233zd and non-azeotropic R1233zd/FC72 mixtures (0.75/0.25, 0.5/0.5, and 0.25/0.75 by mass) across tube bundles. The test section of tube bundles was transparent to observe the flow pattern. The flow boiling heat transfer was measured. The experiments were carried out with vapor qualities of 0.1–0.9, mass flow rates of 3–5 kg/h and heat fluxes of 3000–7000 W/m2. Falling film flow, bubbly flow, bubbly-shear flow, and shear flow were observed. The flow pattern transition maps were presented for various conditions. Increasing the mass fraction of the volatile component R1233zd causes the flow pattern transitions occurring at lower vapor qualities. The heat transfer coefficient of mixtures is lower than that of pure R1233zd. With increasing vapor quality, the heat transfer coefficient increases for both pure R1233zd and the mixture with a R1233zd mass fraction of 75 %. However, for mixtures with R1233zd mass fractions of 50 % and 25 %, the heat transfer coefficient initially increases and then decreases with increasing vapor quality. For vapor qualities higher than 0.5, increasing the volatile component, R1233zd, significantly enhances heat transfer. The heat transfer coefficient increases with increasing mass flow rate and heat flux. The experimental data were compared with correlations in the literature with poor agreement. An improved heat transfer correlation for non-azeotropic mixtures flowing across tube bundles was proposed, which effectively predicted the experimental data.

Power generation gas turbine performance enhancement in hot ambient temperature conditions through axial compressor design optimization

The output power and efficiency of gas turbines are profoundly influenced by ambient temperatures, with higher temperatures resulting in a notable decline in power output. This issue becomes particularly critical during periods of heightened power demand in hot climates. There are two common ways to solve this problem: incorporating auxiliary systems, such as inlet air cooling, or undertaking a comprehensive redesign of the gas turbine core engine. However, these methods sometimes are costly and unfeasible, particularly in regions characterized by arid conditions or constrained budgets for engine modifications. An alternative strategy has been developed to optimize axial compressor performance in order to improve gas turbine power in high-temperature environments, through an innovative approach. This approach centers on the concept of “re-staggering” the stator blades as a retrofit upgrade for existing gas turbines, enabling an increase in compressor inlet mass flow rate while maintaining peak efficiency at 45 °C. An in-house optimization tool was developed, incorporating a genetic algorithm and artificial neural network, to ascertain the optimal configuration of the re-stagger angles. This optimization process was initially coupled with a mean-line solver and subsequently refined using a through-flow model to enhance the preliminary design. The refined compressor design was then subjected to a comprehensive 3D Computational Fluid Dynamics analysis. Additionally, “end-bend” and “elliptical leading edge” techniques were employed to sustain compressor efficiency and ensure stability across various design and off-design operating conditions. Following a thorough structural analysis, the newly designed compressors were manufactured and tested at two distinct sites in Iran (Yazd and Bampur). The measured data demonstrated the commendable performance and stability of the redesigned compressors, aligning closely with numerical predictions. Notably, the results showcased a substantial increase in gas turbine power output ranging from 7.0% to 8.0% at hot ambient conditions, all while preserving efficiency and stability. Encouragingly, the upgraded compressor also exhibited superior performance even at lower temperatures, such as 15 °C. Consequently, this uprating concept presents a practical and cost-effective solution for power plant operators seeking a significant boost in power output, especially during hot weather conditions or in arid regions prone to drought.

Experimental study on the mechanism of water on heat sink variation in catalytic partial steam reforming of supercritical n-decane

Regenerative cooling is an effective method for heat management of hypersonic vehicles and faces a problem of insufficient cooling capacity under higher flight Mach number. Water-assisted hydrocarbon fuels thermal conversion can effectively increase heat absorption and inhibit carbon deposition. The mechanism of water on the variation of heat sink is unclear. In this study, experimental study was conducted to investigate the effect of different water contents, pressure and mass flow rates on the variation of heat sink and the distribution of gaseous products in a continuous experimental system. The results show that catalytic partial steam reforming reaction consists of catalytic steam reforming and catalytic thermal cracking in the low temperature stage (T＜490 ℃), and non-catalytic thermal cracking is activated and gradually dominate in the high temperature stage (T＞490 ℃). The contribution of water to total heat sink is mainly caused by physical heat sink. Increasing mass flow rate mainly suppress the cracking reaction in the high temperature section by reducing reaction residence time. The flow rate has little effect on the chemical reaction equilibrium. Higher pressure has little effect on heat sink, but accelerates carbon deposition by promoting the formation of olefin products.