The
dynamic viscosities of n-dodecane were measured
at temperatures between 303.3 and 693.3 K and pressures up to 10.0
MPa using a dual-capillary viscometer. The accuracy of the dual-capillary
viscometer was improved by considering centrifugal effects and the
thermal expansion of the capillary. The combined relative standard
uncertainty in the dynamic viscosity was calculated to be 0.58–2.92
%. This study provides new data to check the accuracy of Huber’s
correlations at supercritical pressures, and a small proportion of
the data points at supercritical conditions where few experimental
data have been reported. The average absolute deviation between the
experimental data and the calculated data from Huber’s correlations
is 0.97%, and the maximum absolute deviation is 6.79%. In the near-critical
and supercritical region, the accuracy of viscosities of n-dodecane needs more experimental data for verification and to extend
the theories.
Complex permittivity is one of the most important parameters to characterize the interaction between microwave and medium, especially for microwave-excited plasma. It is convenient to study plasma’s dielectric properties and microwave propagation characteristics by measuring its complex permittivity. A dynamic measurement method of equivalent relative complex permittivity of microwave-excited plasma at atmospheric pressure is proposed in this paper. Firstly, a cavity based on WR-430 at a frequency of 2.45 GHz was specially designed in COMSOL. Then, the samples with different real parts of complex permittivity and loss tangent were simulated in the designed cavity to obtain their corresponding S parameters, and they were used to train the BP neural network until the error was lower than 0.001. A two-port network was built to excite the plasma. The input power, reflected power, and transmitted power could be measured by the transmission reflection method. Finally, the measured power values were converted into S parameters and used as inputs in the BP neural network. The plasma’s real parts of complex permittivity and loss tangent were obtained by inversion. The variation of plasma complex permittivity conforms to the interaction principles between microwave and plasma, which verifies the accuracy of the method.
The isobaric specific heat capacity of a kerosene type hydrocarbon fuel was measured online using a flow calorimeter, which was based on the energy conservation theory. The test temperatures covered from (330 to 900) K and operating pressures changed from (1.96 to 4.93) MPa. The isobaric specific heat capacity data have an expanded relative uncertainty of 2.54 % with a coverage factor of 2. The reliability and accuracy of the flow calorimeter measurement was verified by the water, n-hexane, and binary mixtures of n-heptane + n-octane and methanol + acetone, respectively. Finally, the isobaric specific heat capacities of a type of endothermic hydrocarbon fuel were measured and C p −T diagrams were plotted at sub-and supercritical pressure.
■ INTRODUCTIONHydrocarbon fuel plays an important role in the heat management technology for a scramjet engine. 1−3 As a representative application, it is applied as not only a fuel in the combustion chamber but also a primary coolant in a regenerative cooling protection of the scramjet engine. In the cooling process, high heat flux, large temperature difference, and limited mass rate posed a severe challenge for heat transfer of the hydrocarbon fuel. 4 Thus, a fundamental understanding of thermophysical properties of the hydrocarbon fuel are deeply demanded. Specific heat capacity, density, viscosity, and critical parameters are the primary basis of the theoretical analysis and numerical simulation for the hydrocarbons. In this paper, the specific heat capacity measurement of hydrocarbon fuel was conducted.As an important parameter, specific heat capacity has always attracted numerous researchers' attention in the power and engineering applications. Plentiful specific heat capacities of pure and multicomponent substances were investigated experimentally and different calculation equations were summarized. Flow calorimeter, 5−9 differential scanning calorimeter (DSC), adiabatic calorimeter, radiation calorimeter, and metal-bellows calorimeter were the most common instruments for the specific heat capacity measurement. However, most of the test calorimeters were used off-line and could not apply in a high temperature process.Hydrocarbon fuel is a complex mixture, containing hundreds of components. 10 Some researchers investigated the heat capacity of different kerosene propellants. Abdulagatov 11 measured the isobaric heat capacity of rocket propellant (RP-1 fuel) at (293 to 671) K and up to 60 MPa by a vacuum adiabatic calorimeter immersed in a precision liquid thermostat. Deng et al. 9 used a vacuum flow-calorimeter to measure the isobaric specific heat capacity of kerosene RP-3 in the nearcritical and supercritical regions. The estimated uncertainty of their measurement was lower than 2.11%. The heat capacities of jet fuels JP-8 and S-8 were measured with a commercial differential scanning calorimeter by Bruno et al. 12 On the basis of test data, the least-squares generated equations of two fuels were performed for the heat capacity at ambient pressure. Bruno et al. 13 also c...
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