Determination of thermal contact resistances using the spectral functions of boundary effects

A method is proposed for determining thermal contact resistances by solving the inverse heat-conduction problem.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 58, No. 1, pp. 135–140, January, 1990     

精密离心机热变形多物理场耦合数值计算

离心机是惯性导航系统加速度计的标定设备,转盘变形将严重影响标定精度.综合考虑离心机机室内空气流动、流动传热以及机箱和转盘的导热,结合CFD和FEM方法,对精密离心机的热变形进行流-热-固多场耦合计算.分析了多物理场耦合计算原理,采用流固耦合换热整场求解法计算离心机温度场,采用顺序耦合法计算转盘热变形.计算结果表明:在300r/min转速下,转盘最大温升为1.23℃;越远离转盘中心,温升越大;加速度计安装位置的温度计算值与实测值一致,验证了本方法的正确性;转盘安装加速度计位置的径向热变形为7.89μm,热变形是变形累积的结果且随着转盘转速增加而增大.     

Effect of thermal processes on the accuracy of precision fiber-optic inertial sensors

A mathematical model of thermal processes and temperature errors is constructed for a promising sensor to determine the angular position and angular velocity of moving objects—a fiber-optic gyroscope (FOG). Methodological, algorithmic, and program supports are developed making it possible to carry out an automatic investigation of the functioning of an FOG exposed to temperature effects. Computational experiments and computer analysis of thermal processes and thermal drift are performed for specific design versions of the FOG, and recommendations for decrease in the temperature errors of the FOG are developed.Branch of the A. A. Blagonravov Institute of Mechanical Engineering, Saratov. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 66, No. 1, pp. 61–68, January, 1994.     

Identification of boundary thermal perturbations using spectral functions

A method is proposed for solving the external inverse heat-conduction problem in a parametric formulation.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 53, No. 3, pp. 480–486, September, 1987.     

Increasing the accuracy of the process of estimating thermal deformations of precision parts and junctions

Based on results of studies, it is established that the temperature errors of measurements may be reduced through improvements in the measurement methods and in the measuring devices. __________ Translated from Izmeritel’naya Tekhnika, No. 3, pp. 15–19, March, 2008.     

Determination of the thermal conductivity of foam aluminum

We present calculations and experimental data on determination of the thermal conductivity of porous foam aluminum materials. We analyze the possibility of their use for thermal insulation.     

On temperature determination of opaque materials through the spectral maximum of thermal radiation

For the thermal radiation spectral maximum of an opaque freely radiating body, an equation relating the wavelength, the emissivity, and the thermodynamic (the true) temperature of the body is derived. Also a nondimensional parameter bounding the emissivity, its derivative, and the wavelength is identified in the radiation spectral maximum. A value range of this parameter where use of the obtained equation reduces the required temperature uncertainty is determined. Furthermore, a dimensionless parameter characterizing the deviation of the thermal radiation of the real materials from the Wien displacement law is found. The interconnection of the obtained parameters is revealed. By means of a computer experiment, it is shown that, for selectively radiating materials such as tungsten at 2600–3000 K, determination of the true temperature according to the Wien displacement law results in deviations from the true temperature by more than 200 K.     

Importance of spectral measurement errors in the radiometry of thermal and quasimonochromatic radiations

A metrological analysis has been performed of how errors in spectral measurements affect the errors of radiometric calibrations of sources and radiometers for thermal radiation and quasimonochromatic radiation. In order to provide small values for the radiometric errors, one needs to use highly sensitive photoelectric radiometric comparators whose spectral sensitivity is constant in the working range. Translated from Izmeritel'naya Tekhnika, No. 3, pp. 31–35, March, 1999.     

Determination of the contact thermal resistance from the solution of the inverse problem of thermal conductivity

The contact resistance at the boundary between an orthropic reinforcing rod and an isotropic matrix is determined from the solution of the inverse probblem of thermal conductivity, using the gradient method. The suggested modification of the computational algorithm as the initial calculation of the initial period of the thermal process is shown to enhance the resolving power of the method and the choice of zeroth approximations from below is shown to ensure monotonic convergence of the solution.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 56, No. 3, pp. 423–427, March, 1989.     

An analysis of factors influencing precision of thermal property values during freezing

An unfrozen water fraction prediction equation is proposed that compensates for both unfreezable water (M_b) and the equivalent molecular weight of solids (MW_s) during the food freezing process. The parameters (M_b and MW_s), when obtained from published unfrozen water content data, demonstrate that the proposed equation describes the data very well. When unfrozen water content data is not available, MW_s can be obtained from the initial freezing point (T_f) of the food product, and M_b can be obtained using calorimetric methods. The precision of MW_s is shown to be very dependent on the precision of T_f for a frozen food with medium (75%) to high (95%) moisture content. The precision of the input variables required in the proposed equations (temperature, M_b, MW_s, solids content) along with other physical parameters of the unfrozen food product (density, specific heat, and thermal conductivity) were investigated in an effort to determine the predictability of the frozen food density, apparent specific heat, enthalpy, thermal conductivity and unfrozen water content.     

Determination of the thermal conductivity of amorphous metallic alloys

Two techniques are suggested for identifying the temperature dependence of the thermal conductivity of a new class of materials. The results have been obtained for the metallic glass Co₇₇Fe₄Cr₇Si₈B₄.Institute for the Problems of Mechanical Engineering, Kharkov. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 63, No. 3, pp. 314–320, September, 1992.     

Determination of the thermal conductivity and thermal diffusivity of solids by unilateral sounding of the surface

The article analyzes the possibility of determining thermophysical characteristics by nondestructive unilateral sounding of a flat surface. Curves are presented for selecting the optimum regime of the experiments in dependence on the dimensions of the sounded body.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 49, No. 3, pp. 463–466, September, 1985.     

Role of error in spectral measurements in the photometry of thermal and quasimonochromatic radiation

A metrological analysis of the influence of errors in spectral measurements on the error of light calibrations of thermal and quasimonochromatic radiation sources and photometers is presented. It is shown that quasimonochromatic light-emitting diodes, rather than thermal filament lamps, should be used as primary sources in order to maintain low errors in the measurement of the luminous quantities of quasimonochromatic radiation. Translated from Izmeritel'yana Tekhnika. No. 9, pp. 9–14, September, 1998.     

Enhancement of the precision of fiber-optic interferometers by using couplers with high spectral power or antisymmetric supermode cutoff

It is shown that in 2×2 single-mode optical-fiber directional couplers operating with cutoff of the antisymmetric normal mode of a composite waveguide, the additional stray phase shift of the waves in the forward and cross channels (found in normal couplers) vanishes. Thus, by using these couplers (instead of the usual ones) in various interferometers, the precision can be enhanced substantially. It has also been shown that the precision of interferometers with wide-band radiation sources (such as white-light interferometers and fiber-optic gyroscopes) can be improved by replacing the usual couplers with couplers of high spectral power whose splitting ratio can execute a large number of oscillations within the radiation line width, efficiently eliminating the afore-mentioned stray phase shift. Pis’ma Zh. Tekh. Fiz. 23, 76–80 (July 26, 1997)