Nonstationary heat transfer in an inhomogeneous thermally insulated timber sample

A mathematical model and numerical methods to calculate the thermal state of a fragment of the exterior timber wall of a building are suggested. The character of the distribution of temperature fields in homogeneous and inhomogeneous (thermally insulated) timbers and the influence of the thermophysical and geometrical characteristics of a homogeneous timber sample and warmth-keeping lagging on it are determined. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 79, No. 3, pp. 20–25, May–June, 2006.     

On the cathodic protection of thermally insulated pipelines

Thermal insulation and corrosion protection of heated pipelines used in moving oil/gas and heated products are accomplished industry-wide by using protective and insulating coatings supplemented by cathodic protection to protect any defected coating areas. A series of tests are carried out to study how the resistivity of the applied insulating layer polyurethane (PUR) can be affected by its specific gravity (as function of its porosity), as well as, the salt (NaCl) concentration in the surrounding electrolyte (water). The current densities required for cathodic protection of insulated steel pipe at the worst condition (i.e., lower resistivity of the insulating material) at ambient and elevated temperatures were determined. The results have showed: that a lower PUR foam density has lower percentage closed cells which lead to a decrease in the PUR foam resistivity. An increase in the salt concentration up to about 3.5% NaCl leads to about 40% increase in the current intensity required for CP of the insulated steel sheets. In this investigation zinc wire of diameter 5 mm was used as a sacrificial anode in two different manners parallel and spiral. The sacrificial anode was fixed adjacent directly to the electrical insulation under the PUR foam shows a complete protection of the pipes, i.e., about – 920 mV vs. Cu/CuSO₄, in the salty water with about 3.5% NaCl; this method guarantees optimum protection. The experiments performed at different temperatures up to 60 °C showed that increasing the temperature has a slight positive effect.     

Contact conductivity of cryogenic heat insulation materials

Results are presented of an experimental investigation by the method of the electrothermal analogy for the contact heat transfer in different kinds of cryogenic thermal insulation and empirical dependences are obtained that permit execution of a qualitative, and in a number of cases, even a quantitative estimate of the contribution of the contact conductivity to the total heat transport through heat insulation.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 60, No. 1, pp. 121–127, January, 1991.     

Measurement of the heat conductivity of semiconductors by the bridge method

Journal of Engineering Physics and Thermophysics -     

Determining the thermal conductivity of thin-layer materials by the interpolation method

The interpolation method is outlined, by which the thermal conductivity of thin-layer materials can be determined without measuring the specimen thickness and with the effect of thermal contact resistances eliminated.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 22, No. 3, pp. 456–459, March 1972.     

Generalized nomogram for finding approximate temperature of a thermally insulated cylindrical or flat wall

A generalized nomogram is obtained from Grover's nomogram [2] by changing the flat wall parameter to a generalized cylindrical wall parameter. Formulas are given for computing this parameter, and examples of calculations with the nomogram are presented.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 19, No. 6, pp. 1100–1103, December, 1970.     

Use of the grover nomogram for the approximate calculation of the temperature of a thermally insulated cylindrical wall

It is proposed to use the temperature no,mogram constructed for a flat two-layer (metal-insulation) wall to determine the temperature of a cylindrical wall. Formulas for the correction factors are presented together with examples of wall temperature calculations for various combinations of the thermal parameters.     

Measurements of temperature conductivity by the method of radial temperature waves in a cylinder

Summary The analysis of errors, confirmed experimentally, shows that, for measurements under optimum conditions, the absolute value of temperature conductivity can be easily obtained by the radial temperature wave method with an accuracy of 3% over a very wide temperature range. These optimum conditions consist in providing that Pd_r9 and that the ratio of the diameter to the length of the sample 13. The experiment is not complicated and can be made completely automatic. This method can be recommended for badly conducting materials which can be easily machined (for instance, plastics).     

Determination of thermal flux density,medium temperature and heat liberation coefficient by solution of the converse thermal conductivity problem

The converse thermal conductivity problem of determining temperature of the hot medium, heat liberation coefficient, and thermal flux density for asymmetic heating is solved using results of wall temperature measurements at three points located different distances from the hot surface.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 56, No. 3, pp. 395–398, March, 1989.     

Low temperature thermal conductivity of some composite materials

Thermal conductivity data are presented for several samples: Gd₂(SO₄)₃ 8H₂O pressed powders with and without copper fibres, pressed powders of NaCl and KCl, cloth base phenolic sheet, epoxy resin-bonded glass fibre laminate, and AGOT graphite in the presence of helium gas. Measurements on all samples were made in the 1–4 K range and on the phenolic sheet and glass fibre laminate at 70 K as well.     

Determination of ionisation energies and attempt-to-escape factors using thermally stimulated conductivity

A procedure for determining an arbitrary distribution of activation energies (E) and attempt-to-escape frequencies (s) from overlapping contributions to thermoluminescence (TL) or thermally stimulated conductivity (TSC) is described. For the case of no retrapping, i.e. first order kinetics, the glow curve can be described by a two-dimensional Fredholm equation representing a superposition of Randall-Wilkins first-order peak shapes. The solution to this equation gives the distribution of trapping energies and attempt-to-escape-frequency factors necessary to obtain the TL or TSC peak shape. Analysis of simulated TL/TSC data for trap distributions distributed in both E and s demonstrates that the arbitrary E and s values can be determined from the solution of the Fredholm equation. The procedure is demonstrated for experimental TSC data from gamma-irradiated Al2O3:C.     

Determination of the temperature and density of a heat flux from the solution of the inverse heat conduction problem for a thermally destructible material

The problem of determination of a heat flux density from the state of a material after heating is considered.Research Production Amalgamation Énergiya. Moscow Forestry and Timber Processing Institute. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 65, No. 6, pp. 652–656, December, 1993.     

低温热导率的热扫描法测量

介绍了一种利用热扫描技术测量低温热导率的新方法.实验利用计算机自动采集数据并实时处理给出测量结果,测量温度范围为10 K-300 K.热扫描方法降低了各种漏热影响,修正了因温差测量的困难而带来的实验误差.通过金属铜、铝的测量值与标准数据的比较,发现10 K-300K范围有较好的吻合,相对误差小于5%,温度越低,误差越小.     

Micromachined silicon electrolytic conductivity probes with integrated temperature sensor

Electrolytic conductivity measurements of fluids currently require sample volumes greater than a milliliter. Many applications would benefit from accurate measurements of nano- to microliter sample volumes. However, polarization and nonlinear electrode impedance effects, along with stray impedance and temperature effects, strongly affect measurements of the solution conductance for microliter and smaller sample volumes. MEMS-based silicon electrolytic conductivity probes, down to 100-/spl mu/m wide, with integrated temperature sensors, have been designed and fabricated to overcome these effects. Several electrode configurations were tested: plain electrode pairs, electrode pairs plated with platinum black, plain four electrode sets, and four electrode sets plated with platinum black were investigated. The same accuracy as normal scale probes has been achieved with these sensors over almost three orders of magnitude in solution concentration and electrolytic conductivity ranges.     

Group method for temperature analysis of thermally stagnant lakes

Summary The transformation group theoretic approach is applied to present an analysis for the problem of time dependent vertical temperature distribution in a stagnant lake during the yearly cycle of solar heating and cooling. The application of a one-parameter group reduces the number of independent variables by one, and consequently the governing partial differential equation with the boundary and initial conditions to an ordinary differential equation with the appropriate corresponding conditions. The obtained differential equation is solved, for some special forms of the water parameters, analytically, whenever possible, and in some other cases numerically using the shooting technique. The temperature distribution across the lake is plotted against the lake depth.     

Unsteady heat conduction of a thin rod with a uniformly moving fusion boundary or a thermally insulated boundary

A solution is obtained to the problem of unsteady heat conduction of a semi-infinite thin rod, thermally insulated along its generators, or a plate, with a uniformly moving fusion boundary, or a thermally insulated boundary. The results are presented of a numerical calculation for a copper rod with various rates of motion of the boundary.     

固体材料低温热导率测试系统

研制出工程材料低温热导率测试系统.测试采用稳态纵向热流法,高真空绝热恒温器,并利用热开关装置,解决了传统测试方法降温速率慢的问题.通过与标准样品比对,证明测试误差在5%以内.利用该测试系统研究了不锈钢、钛合金及镁合金的低温热导率.     

A method for quantitative risk assessment of temperature control in insulated boxes

The domestic transport of low volume perishable products is commonly conducted with the use of insulated boxes and non-refrigerated commercial courier networks. The temperature of the product during transport is governed by the balance of the environmental temperature and the protection provided by the box's insulation and accompanying coolant (e.g. ice). While the box, product and coolant properties may be constant, the ability of that package to maintain appropriate product temperatures will be different due to the day-to-day variation in environmental conditions. This paper presents a method that uses historic climatic data to estimate environmental temperatures during transport and subsequently provides a quantitative estimate of the likelihood of package temperature control failure. Three packages travelling by road from Sydney to Melbourne are compared as an example of the use of the methodology.     

Determination of the thermal conductivity and diffusivity of thin fibres by the composite method

It is suggested that the thermal conductivity of very fine fibres can be evaluated indirectly with the aid of composite theory using the experimental data for the heat transport properties of an appropriate composite which contains the fibres. The feasibility of this approach was investigated by determining the thermal conductivity and diffusivity of fibres of amorphous silicon carbide from 25° C to 1000° C contained within a lithium aluminosilicate glass-ceramic using the laser-flash technique for measurement of the thermal diffusivity of the composite. Due to the amorphous nature of the fibres, values for their thermal conductivity and diffusivity were found to be far less than the corresponding data for crystalline silicon carbide. The positive temperature dependence of the thermal conductivity, coupled with the independent observation of an increase in thermal conductivity with specimen thickness, suggests that radiative heat transfer makes a significant contribution to the total heat transferred. A number of advantages and limitations of the composite method for the evaluation of thermal transport properties of fibres are discussed.