Thermal Deviation Research Articles

Model for the Viscosity and Thermal Conductivity of Refrigerants, Including a New Correlation for the Viscosity of R134a

We present modifications to an extended corresponding states (ECS) model for thermal conductivity and viscosity originally developed by Ely and Hanley (Ind. Eng. Chem. Fundam. 1981, 20, 323-332). We apply the method to 17 pure refrigerants and present coefficients for the model and comparisons with experimental data. The average absolute viscosity deviation for the 17 pure fluids studied ranges from a low of 0.56% for R236ea to a high of 5.68% for propylene, with an average absolute deviation for all fluids of 3.13% based on a total of 3737 points. The average absolute thermal conductivity deviation for the 17 pure fluids studied ranges from a low of 1.37% for R116 to a high of 6.78% for R115, with an average absolute deviation for all fluids of 3.75% based on a total of 12 156 points. We also present a new correlation for the viscosity of R134a (1,1,1,2-tetrafluoroethane), which is used as a reference fluid for the description of properties of some refrigerants. The new correlation represents the viscosity to within the uncertainty of the best experimental data.

338 High Efficient Evaluation Method for Z Directional Thermal Deviation of Machine Tool Caused by Spindle Rotation

A measurement and evaluation method for thermal deviations caused by machine tool spindle rotation was standardized in ISO 230-3,then it began to be widely used. However, the method is not efficient since many cold start tests must be carried out. Therefore, a more efficient method is proposed in the study that the Z directional thermal deviation is modeled as first order lag, and this model parameters are identified using only one spindle pattern operation to evaluate the thermal characteristics. The effectiveness of the method is made clear form comparing the results from some cold start tests and two spindle pattern operation tests.

Thermal power estimation by fouling phenomena compensation using wavelet and principal component analysis

A small percentage of reactor thermal power can be overestimated because of fouling phenomena in a secondary feedwater flowmeter. This study proposes a signal processing technique for the compensation of a degraded flowmeter such a secondary feedwater flowmeter in nuclear power plants. The technique proposed is mainly focused on noise classification and step-by-step noise reduction. The noises focused are classified into the rapid distortion caused by environmental interference, the flow fluctuation according to plant state transition and the degradation by fouling phenomena qualitatively. The multi-step de-noising technique reduces each noise by three techniques step-by-step. The wavelet analysis as a low frequency pass filter to remove the rapid distortion, the linear principal component analysis (PCA) to predict a steady-state value from the fluctuation, and the non-linear PCA implemented as an autoassociative neural network (AANN) to predict an original value from the signal including fouling phenomena are developed. The main purpose of this approach is to make an AANN concentrate on compensating the degradation by fouling phenomena itself. For the demonstration the signals from a simulator and signal modeling were used so that the role and the performance of each noise removal step was represented. In addition a thermal power deviation estimator is proposed to recognize the degradation effect of each operating parameter for reactor thermal power calculation.

Thermal load deviation model for superheater and reheater of a utility boiler

The extreme steam temperature deviation experienced in the superheater and reheater of a utility boiler can seriously affect its economic and safe operation. This temperature deviation is one of the root causes of boiler tube failures (BTF), which causes about 40% of the forced power station outages. The steam temperature deviation is mainly due to the thermal load deviation in the lateral direction of the superheater and reheater. This variation is very difficult to measure in situ using direct experimental techniques. In this paper, we propose a thermal load model that is based on the power plant thermodynamic parameters, thermal deviation theory, and flow rate deviation theory. It is found that the calculated results from our model agree well with the in situ experimental results. The predicted BTF positions are the same as that in the reheater of a 300 MW utility boiler at Wujing Power Plant. The proposed model has been used to improve the design of utility boiler in Boiler Works, predict the possible BTF in the design stage, and assess the existing designs. This model can also be applied to utility boilers of different manufactures, and has been successfully applied to the BTF prediction and prevention in the Power Station.

Implications of the oceanic thermal skin temperature deviation at high wind speed

Extensive oceanographic and atmospheric observations obtained during three independent experiments in the Atlantic Ocean are used to demonstrate the relationship between wind speed and the temperature deviation ΔT, which is defined as the sea surface skin temperature (SSST) minus the subsurface bulk sea surface temperature (BSST). At wind speeds <6 m s−1, the variability of ΔT increases because thermal stratification complicates the measurement and interpretation of ΔT: extreme ΔT magnitudes of >1.5 K are common during periods of high insolation. The variability of ΔT at night is reduced and extreme cool skin temperatures of < −0.5 K are recorded. In all cases, at wind speeds >6 m s−1, the variability of ΔT is diminished and the mean value of ΔT approximates a cool bias of −0.14 K±0.1 K. We conclude that BSST measurements obtained at wind speeds >6 m s−1, when corrected for a small ( −0.14 K) cool bias, are representative of the SSST and can be used with confidence to validate satellite derived SSST. When the wind speed is <6 m s−1 and the magnitude of ΔT is high, in situ radio metric SSST measurements are mandatory to validate satellite derived SSST.

Thermal conductivity and heat capacity of ABS resin composites

Thermal conductivity and heat capacity of composites of ABS resin with glass beads and/or titania were measured. For ABS-glass-beads composites, the thermal conductivity data are in good agreement with values calculated by the Maxwell and Bruggeman equations in a temperature range above a critical temperature, but much deviation was observed below this temperature. Similarly for the heat capacity, the measured data are in excellent agreement with the calculated values assuming additivity above the critical temperature, while the measured data are clearly less than the calculated values below this temperature. On the other hand, for the ABS-titania the measured data of heat capacity are higher than the additivity in the whole temperature range, though linearity was found among titania and the composites also in the whole temperature range. The thermal conductivity observed for this composite is in good agreement with the theoretical value calculated by the Maxwell and Bruggeman equations except in a low temperature range. By dynamic viscoelastic observation, it was found that a new dissipation occurs around 95°C in the composite of the glass beads. These facts suggest that interaction exists between the resin and the fillers, and this interaction causes the deviation from the Maxwell and Bruggeman equations in the thermal conductivity and deviation from the additivity in the heat capacity below the critical temperature. For the composite of titania no new dissipation was found, but a small dissipation originally observed for the resin was not seen. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1279–1286, 1997

Geological prognosis ahead of a tunnel face

The locations of a specific geological boundary and aquifer were predicted, prior to reaching them, by a reflection method and the measurement of geothermic temperature. The determination was performed during tunnelling work which passed through the Median Tectonic Line in central Japan. The reflection method procedure was as follows. A P-wave was produced on the tunnel face by a small blasting. The location of the velocity layer boundary was predicted by the travel time of the direct wave and the reflected wave. The geothermic temperature was measured by a thermocouple which was set in the borehole at the face. The location of the aquifer was predicted by the thermal deviation between the measured value and the theoretical value that was determined from a mean geothermal gradient. Also, a water quality survey is performed, discussing the quality of the fissure water. In addition, we were able to confirm, using the Seismic Tomography method, that the sheared zone found, was the layer including lens-shaped low-velocity zone. The methods considered proved to be simple and effective for geological prognosis from within the tunnel.

The aluminium thermal conductivity and deviation from matthiessen's rule

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Local magnetizations in impure two-dimensional antiferromagnets

The local magnetizations near dilute substitutional impurities in the quadratic-layer antiferromagnet ${\mathrm{K}}_{2}$Mn${\mathrm{F}}_{4}$ are studied both experimentally and theoretically. The impurities considered are the nonmagnetic Zn and Mg, as well as Ni. The magnetizations are probed through the positions of the impurity-associated satellites in the nuclear magnetic resonance of the out-of-layer and in-layer $^{19}\mathrm{F}$ nuclei adjacent to the magnetic ions. It is discussed in which way the effects of lattice deformations can be eliminated in order to obtain the variations of the local magnetizations with temperature. The theoretical treatment is based on Green's-function techniques. The decoupling employed is within the local spin-deviation operators and accounts for correlation between nearest neighbors. It reduces the renormalized spin-wave Hamiltonian to an effective quadratic form, rendering decoupling of Green's functions unnecessary. The spectral distributions of the excitations are calculated including local modes. The theory is subsequently applied to the 13-site cluster consisting of the impurity and the first three shells of Mn around it. Good agreement is found. The magnetization is significantly modified in the first shell. The further shells are only weakly affected, however somewhat stronger than in comparable three-dimensional systems. For nonmagnetic impurities the thermal spin deviation in the first shell is about $\frac{1}{3}$ larger than that of the host; in the Ni-doped system the additional deviations are within 1%. The zero-point deviation of the Ni is 0.11 units of spin, as compared to 0.17 in the host. A further experimental result is a uniform shift, increasing with concentration, of the sublattice magnetization at large distance from the impurity. It must be related to the finite density of states near the zone center in two-dimensional systems. Finally, some data are presented on the local susceptibilities.

Thermoelastic Effect Caused by Longitudinal Collision of Two Bars

According to the one-dimensional elastic theory, it is well known that step waves of stress and strain propagate when two semi-infinite bars collide with each other. However, to describe precisely, the adiabatic deformation causes a thermal deviation along the bars. Consequently, the heat flow thus produced has an effect on the stress and strain waves. In this paper, the problem is formulated as a coupled transient phenomenon using the one-dimensional equation of motion, the thermal stress-strain relations and the equation of heat flow. The strain and temperature distributions are obtained. It is found that the wave front propagates with velocity c0=√(E<SUB)T/ρ> (ET: isothermal Young's modulus). the strain is observed even in the region ahead of the wave front, and the magnitude of the strain behind the wave front is nearly constant but a little smaller compared with that of the ordinary elastic theory.

Absorption and extraction

The density and viscosity of the pure monoethylethanolamine (EMEA), diethylethanolamine (DEEA), H2O components and the binary EMEA (1) +DEEA (2) and EMEA (1) +H2O (2) mixtures were measured from (293.15–333.15) K. The physical and thermodynamic properties of excess molar volume (VE), thermal expansion coefficient (α), viscosity deviation (Δh), activation enthalpy (ΔH), activation entropy (ΔS) and activation molar Gibbs free energy (ΔG) were calculated. The density and viscosity of the pure components as well as the binary mixtures decreased with temperature increasing. The density and viscosity of EMEA, DEEA and H2O followed the orders of H2O > EMEA > DEEA and EMEA > DEEA > H2O, respectively. The density and viscosity decreased with DEEA concentration increasing for EMEA (1) +DEEA (2). In EMEA (1) +H2O (2), the density increased with H2O concentration increasing, while the viscosity increased and then decreased with H2O concentration increasing.