Experimental Study on Heat Transfer of Supercritical Kerosene in a Vertical Upward Tube

2013 ◽  
Author(s):  
Dan Huang ◽  
Wei Li ◽  
Wei Zhang ◽  
Guo-Qiang Xu ◽  
Zhi Tao
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Critical Temperature ◽  
Physical Properties ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Supercritical Pressure ◽  
Fluid Temperature ◽  
Thermo Physical Properties

A research on the heat transfer performance of kerosene flowing in a vertical upward tube at supercritical pressure is presented. In the experiments, insights are offered on the effects of the factors such as mass flow rate, heat flux and pressure. It is found that increasing the mass flow rate could enhance the heat transfer performances, while increasing the working pressure will deteriorate the heat transfer. Besides, the effect of heat flux on heat transfer is complicated. Based on the analysis of experimental data, enhancement of heat transfer occurs when the inner wall temperature of tube is higher than pseudo-critical temperature while the bulk fluid temperature is lower than the pseudo-critical temperature. At the supercritical conditions, heat transfer is influenced by the significant changes in thermo-physical properties, thus accurate evaluations of the thermo-physical properties become the key for the supercritical heat transfer calculations. The extended corresponding-state principle could be used for evaluating the density and the transport properties of kerosene, including its viscosity and thermal conductivity, at different temperatures and pressures. In order to obtain the numerical values of the heat capacity, a Soave–Redlich–Kwong (SRK) equation of state is used. The correlation for predicting heat transfer in kerosene at supercritical pressure is established, the calculation results from this correlation are in good agreement with the experimental results.

Two-phase natural circulation loop behaviour at atmospheric and subatmospheric conditions

2018 ◽  
Vol 233 (4) ◽  
pp. 687-700
Author(s):  
S Venkata Sai Sudheer ◽  
K Kiran Kumar ◽  
Karthik Balasubramanian
Keyword(s):  
Heat Flux ◽  
Physical Properties ◽  
Spatial Variation ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Natural Circulation ◽  
Two Phase ◽  
Natural Circulation Loop ◽  
Thermo Physical Properties

This paper aims to present the steady-state behaviour of two-phase natural circulation loop at atmospheric and sub-atmospheric conditions. One-dimensional numerical approach is adopted to evaluate various system parameters, with special emphasis on spatial variation of thermo-physical properties and flashing. Homogeneous equilibrium model is applied for two-phase flows. An in-house code is developed in MATLAB to solve numerical model iteratively. It is observed that consideration of spatial variation of thermo-physical properties can precisely predict the loop behaviour. The evaluated results are validated with the open literature and reasonably good agreement is observed. The heater inlet temperature, inlet pressure and heat flux are found to have significant influence on spatial variation of pressure, temperature and enthalpy. As system pressure decreases from atmospheric to sub-atmospheric (1–0.8 atm), it is observed that the sub-atmospheric loop gives a higher mass flow rate compared to atmospheric loop at lower heat fluxes. However, as the heat flux increases in the sub-atmospheric loop, the mass flow rate is reduced due to increased drag force in the loop.

Heat Transfer and Flow Friction Characteristics for Compact Cold Plates

2003 ◽  
Vol 125 (1) ◽  
pp. 104-113 ◽  
Author(s):  
Chang-Yuan Liu ◽  
Ying-Huei Hung
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Nusselt Number ◽  
Thermal Resistance ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Average Nusselt Number ◽  
Cold Plate ◽  
Air Mass

Both experimental and theoretical investigations on the heat transfer and flow friction characteristics of compact cold plates have been performed. From the results, the local and average temperature rises on the cold plate surface increase with increasing chip heat flux or decreasing air mass flow rate. Besides, the effect of chip heat flux on the thermal resistance of cold plate is insignificant; while the thermal resistance of cold plate decreases with increasing air mass flow rate. Three empirical correlations of thermal resistance in terms of air mass flow rate with a power of −0.228 are presented. As for average Nusselt number, the effect of chip heat flux on the average Nusselt number is insignificant; while the average Nusselt number of the cold plate increases with increasing Reynolds number. An empirical relationship between Nu¯cp and Re can be correlated. In the flow frictional aspect, the overall pressure drop of the cold plate increases with increasing air mass flow rate; while it is insignificantly affected by chip heat flux. An empirical correlation of the overall pressure drop in terms of air mass flow rate with a power of 1.265 is presented. Finally, both heat transfer performance factor “j” and pumping power factor “f” decrease with increasing Reynolds number in a power of 0.805; while they are independent of chip heat flux. The Colburn analogy can be adequately employed in the study.

Conjugate Flow and Heat Transfer Investigation of a Turbo Charger: Part II — Experimental Results

2003 ◽  
Author(s):  
Dieter Bohn ◽  
Norbert Moritz ◽  
Michael Wolff
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Inlet Temperature ◽  
Total Heat Flux ◽  
Turbine Inlet Temperature ◽  
Turbine Inlet ◽  
Turbo Charger

In this paper the results of experimental investigations are presented that were performed at the institute’s turbo charger test stand to determine the heat flux between the turbine and the compressor of a passenger car turbo charger. A parametric study has been performed varying the turbine inlet temperature and the mass flow rate. The aim of the analysis is to provide a relation of the Reynolds number at the compressor inlet and the heat flux from the turbine to the compressor with the turbine inlet temperature as the parameter. Thereto, the analysis of the local heat fluxes is necessary which is performed in a numerical conjugate heat transfer and flow analysis which is presented in part I of the paper. Beyond the measurements necessary to determine the operating point of compressor and turbine, the surface temperature of the casings were measured by resistance thermometers at different positions and by thermography. All measurement results were used as boundary conditions for the numerical simulation, i.e. the inlet and outlet flow conditions for compressor and turbine, the rotational speed, the oil temperatures and the temperature distribution on the outer casing surface of the turbo charger. The experimental results show that the total heat flux from turbine to compressor is mainly influenced by the turbine inlet temperature. The increase of the mass flow rate leads to a higher pressure ratio in the compressor so that the compressor casing temperature is increased. Due to the turbo charger’s geometry heat radiation has a small influence on the total heat flux.

Numerical and Experimental Investigations on Heat Transfer Phenomena of an Aluminium Microchannel Heat Sink

2011 ◽  
Vol 145 ◽  
pp. 129-133 ◽  
Author(s):  
Thanhtrung Dang ◽  
Ngoctan Tran ◽  
Jyh Tong Teng
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Heat Sink ◽  
Inlet Temperature ◽  
Outlet Temperature ◽  
Microchannel Heat Sink ◽  
Maximum Heat

The study was done both numerically and experimentally on the heat transfer behaviors of a microchannel heat sink. The solver of numerical simulations (CFD - ACE+software package) was developed by using the finite volume method. This numerical method was performed to simulate for an overall microchannel heat sink, including the channels, substrate, manifolds of channels as well as the covered top wall. Numerical results associated with such kinds of overall microchannel heat sinks are rarely seen in the literatures. For cases done in this study, a heat flux of 9.6 W/cm2was achieved for the microchannel heat sink having the inlet temperature of 25 °C and mass flow rate of 0.4 g/s with the uniform surface temperature of bottom wall of the substrate of 50 °C; besides, the maximum heat transfer effectiveness of this device reached 94.4%. Moreover, in this study, when the mass flow rate increases, the outlet temperature decreases; however, as the mass flow rate increases, the heat flux of this heat sink increases also. In addition, the results obtained from the numerical analyses were in good agreement with those obtained from the experiments as well as those from the literatures, with the maximum discrepancies of the heat fluxes estimated to be less than 6 %.

scholarly journals Numerical Study on Regenerative Cooling Characteristics of Kerosene Scramjets

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Xuan Jin ◽  
Chibing Shen ◽  
Xianyu Wu
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Fluid Velocity ◽  
Regenerative Cooling ◽  
Outlet Pressure

The use of kerosene-based regenerative cooling for scramjet has been found widespread attention due to its inherent nature of high energy utilization efficiency and good thermal protection performance. In order to provide a reference for the later design and experiments, three-dimensional turbulence simulations and sensitivity analysis were performed to determine the effects of three operating mode parameters, heat flux, mass flow rate, and outlet pressure, on the regenerative cooling characteristics of kerosene scramjets. A single rectangular-shaped channel for regenerative cooling was assumed. The RNG k-ε turbulence model and kerosene cracking mechanism with single-step global reaction were applied for the supercritical-pressure heat transfer of kerosene flows in the channel. Conclusions can be drawn that as the kerosene temperature rises along the channel, the decrease of fluid density and viscosity contributes to increasing the fluid velocity and heat transfer. When the kerosene temperature is close to the pseudocritical temperature, the pyrolysis reaction results into the rapid increase of fluid velocity. However, the heat transfer deterioration occurs as the specific heat and thermal conductivity experience their turning points. The higher heat flux leads to lower heat transfer coefficient, and the latter stops rising when the wall temperature reaches the pseudocritical temperature. The same rising trend of the heat transfer coefficient is observed under different outlet pressures, but the heat transfer deterioration occurs earlier at smaller outlet pressure for the reason that the corresponding pseudocritical temperature decreases. The heat transfer coefficient increases significantly along with the rise of the mass flow rate, which is mainly attributable to the increase of Reynolds number. Quantitative results indicate that as the main influence factors, the heat flux and mass flow rate are respectively negatively and positively relative to the intensification of heat transfer, but outlet pressure always has little effects on cooling performance.

Numerical Simulations of Natural Convective Heat Transfer in Vertical Concentric and Eccentric Annular Channels

2018 ◽  
Vol 140 (10) ◽  
Author(s):  
A. A. Busedra ◽  
S. Tavoularis
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Mass Flow Rate ◽  
Convective Heat ◽  
Mass Flow ◽  
Flow Rate ◽  
Annular Channel ◽  
Diameter Ratio ◽  
Fluid Temperature ◽  
Annular Channels

Natural convective heat transfer in a concentric and a highly eccentric, vertical, open ended, annular channel has been investigated numerically. The inner to outer diameter ratio was 0.61, and the height to hydraulic diameter ratio was 18:1. Three heating modes were considered, all having uniform heat flux applied to one or both of the two walls, while the unheated wall was kept adiabatic. The wall temperature distribution, mass flow rate, and midchannel Nusselt number for the case with both walls heated were found to be in excellent agreement with available experimental results. For the same heating conditions, the heat transfer rate in the concentric annular channel was found to be greater than that in the highly eccentric channel, while the mass flow rate was higher in the eccentric channel. A novel finding for the eccentric channel was that the location of maximum velocity was intermediate between the narrow and wide gaps. Another novel observation, which was attributed to radiation effects, was that the fluid temperature in the wide gap region was lower than that of an adiabatic wall. The paper contains additional observations that would be of interest to designers of systems containing annular channels.

Effect of pre-swirl nozzle closure modes on unsteady flow and heat transfer characteristics in a pre-swirl system of aero-engine

2021 ◽  
pp. 095441002110191
Author(s):  
Gaowen Liu ◽  
Zhao Lei ◽  
Aqiang Lin ◽  
Qing Feng ◽  
Yan Chen
Keyword(s):  
Heat Transfer ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Temperature Drop ◽  
Thermodynamic Characteristics ◽  
Circumferential Direction ◽  
Temperature Changes ◽  
Air Supply ◽  
Cooling Air

The pre-swirl system is of great importance for temperature drop and cooling air supply. This study aims to investigate the influencing mechanism of heat transfer, nonuniform thermodynamic characteristics, and cooling air supply sensitivity in a pre-swirl system by the application of the flow control method of the pre-swirl nozzle. A novel test rig was proposed to actively control the supplied cooling air mass flow rate by three adjustable pre-swirl nozzles. Then, the transient problem of the pre-swirl system was numerically conducted by comparison with 60°, 120°, and 180° rotating disk cavity cases, which were verified with the experiment results. Results show that the partial nozzle closure will aggravate the fluctuation of air supply mass flow rate and temperature. When three parts of nozzles are closed evenly at 120° in the circumferential direction, the maximum value of the nonuniformity coefficient of air supply mass flow rate changes to 3.1% and that of temperature changes to 0.25%. When six parts of nozzles are closed evenly at 60° in the circumferential direction, the maximum nonuniformity coefficient of air supply mass flow rate changes to 1.4% and that of temperature changes to 0.20%. However, different partial nozzle closure modes have little effect on the average air supply parameters. Closing 14.3% of the nozzle area will reduce the air supply mass flow rate by 9.9% and the average air supply temperature by about 1 K.

Convective Heat Transfer Performance of FC-72 in a Pin-Finned Channel

2008 ◽  
Author(s):  
Liang-Han Chien ◽  
S.-Y. Pei ◽  
T.-Y. Wu
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Flow Rate ◽  
Smooth Surface ◽  
Heat Transfer Performance ◽  
Fluid Temperature ◽  
Transfer Performance ◽  
Finned Surface

This study investigates the influence of the heat flux and mass velocity on convective heat transfer performance of FC-72 in a rectangular channel of 20mm in width and 2 mm in height. The heated side has either a smooth surface or a pin-finned surface. The inlet fluid temperature is maintained at 30°C. The total length of the test channel is 113 mm, with a heated length of 25mm. The flow rate varies between 80 and 960 ml/min, and the heat flux sets between 18 and 50 W/cm2. The experimental results show that the controlling variable is heat flux instead of flow rate because of the boiling activities in FC-72. At a fixed flow rate, the pin-finned surface yields up to 20% higher heat transfer coefficient and greater critical heat flux than those of a smooth surface.

Thermal and Fluid Dynamic Behavior of a Horizontal Channel With Adiabatic Moving Lower Plate

2005 ◽  
Author(s):  
Assunta Andreozzi ◽  
Vincenzo Naso ◽  
Oronzio Manca
Keyword(s):  
Heat Flux ◽  
Reynolds Number ◽  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Horizontal Channel ◽  
Lower Plate ◽  
Stationary Condition ◽  
Moving Plate ◽  
Plate Velocity

In this study a numerical investigation of mixed convection in air in horizontal parallel walled channels with moving lower plate is carried out. The moving lower plate has a constant velocity and it is adiabatic, whereas the upper one is heated at uniform heat flux. The effects of horizontal channel height, heat flux and moving plate velocity are analyzed. Results in terms of temperature and stream function fields are given and the mass flow rate per unit of length and divided by the dynamic viscosity is reported as a function of Reynolds number based on the moving plate velocity. For stationary condition of lower plate, a typical C–loop inside the horizontal channel is detected. Different flow motions are observed in the channel and the two reservoirs, depending on the heat flux values and the distance between the heated upper stationary plate and lower adiabatic moving plate. The dimensionless induced mass flow rate presents different increase between the Reynolds number lower or greater than 1000.

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