Measurement Method for the Simultaneous Determination of Thermal Resistance and Temperature Gradients in the DeterMination of Thermal Properties of Textile Material Layers

The thermal properties of most clothing products are still not designed according to engineering science due to the lack of simple and acceptable measuring equipment and methods; the type of thermal insulation material, the number of layers of clothing and their thickness are thus chosen empirically. The novelty of this study was the development of a new measuring device and method for simultaneous measurements in the determination of the thermal resistance in one or more textile material layers, such as in multilayer composite clothing. Temperature gradients of textile material layers are presented, as well as the theoretical principles of operation and practical results. Four materials for the production of protective jackets were selected, from which different combinations of composite clothing were constructed and the thermal parameters were measured with a new method and a new device, both individually for the built-in materials and for the composites. Subsequently, five test jackets with the same arrangement of textile material layers as the previously tested composites were produced, and measurements of important thermal parameters were recorded with a thermal mannequin. The determined temperature gradients and measurement results are presented, and based on these it was determined that the total thermal resistance was not equal to the algebraic sum of the resistances of the individual textile material layers in the horizontal position; it was, however, higher, increasing from 30% to 94% due to small air layers caused by crimping and protruding fibres of yarn in the textile fabrics. The same textile material layers built into clothing in the vertical position allowed the formation of significantly wider air layers that increased the thermal resistance by between 2.5 and 9 times.

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Thermal Properties of Thin Metallic Layer Deposited on Insulators: Effect of the Interface on the Independent Determination of the Thermal Diffusivity and Conductivity of the Layer

ASME 2008 First International Conference on Micro/Nanoscale Heat Transfer, Parts A and B ◽

10.1115/mnht2008-52298 ◽

2008 ◽

Author(s):

Danie`le Fournier ◽

Jean Paul Roger ◽

Christian Fretigny

Keyword(s):

Thermal Conductivity ◽

Thermal Properties ◽

Thermal Diffusivity ◽

Thermal Resistance ◽

Thermal Contact ◽

Heat Diffusion ◽

Metallic Layer ◽

Good Thermal Contact ◽

Lateral Heat

Lateral heat diffusion thermoreflectance is a very powerful tool for determining directly the thermal diffusivity of layered structures. To do that, experimental data are fitted with the help of a heat diffusion model in which the ratio between the thermal conductivity k and the thermal diffusivity D of each layer is fixed, and the thermal properties of the substrate are known. We have shown in a previous work that it is possible to determine independently the thermal diffusivity and the thermal conductivity of a metallic layer deposited on an insulator, by taking into consideration all the data obtained at different modulation frequencies. Moreover, it is well known that to prevent a lack of adhesion of a gold film deposited on substrates like silica, an intermediate very thin (Cr or Ti) layer is deposited to assure a good thermal contact. We extend our previous work: the asymptotic behaviour determination of the surface temperature wave at large distances from the modulated point heat source for one layer deposited on the substrate to the two layers model. In this case (very thin adhesion coating whose thermal properties and thickness are known), it can be establish that the thermal diffusivity and the thermal conductivity of the top layer can still be determined independently. It is interesting to underline that the calculus can also be extended to the case of a thermal contact resistance which has often to be taken into account between two solids. We call thermal resistance a very thin layer exhibiting a very low thermal conductivity. In this case, the three parameters we have to determine are the thermal conductivity and the thermal diffusivity of the layer and the thermal resistance. We will show that, in this case, the thermal conductivity of the layer is always obtained independently of a bound of the couple thermal resistance – thermal diffusivity, the thermal diffusivity being under bounded and the thermal resistance lower bounded. Experimental results on thin gold layers deposited on silica with and without adhesion layers are presented to illustrate the method. Discussions on the accuracy will also be presented.

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Calculation and Experimental Evaluation of the Thermal Resistance of a Structure with Reflective Insulation

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.899.374 ◽

2014 ◽

Vol 899 ◽

pp. 374-380 ◽

Cited By ~ 1

Author(s):

Jiří Kalánek ◽

Libor Šteffek ◽

Milan Ostrý

Keyword(s):

Thermal Properties ◽

Thermal Resistance ◽

Thermal Insulation ◽

Experimental Methods ◽

Test Element ◽

Normative Requirements ◽

Box Method ◽

Insulation Performance ◽

Heat Transfer By Radiation

As reason of increasing requirements of thermal insulation properties of the exposed envelope, reflective insulation are among kind of modern thermal insulation materials ones, which can significantly increased thermal insulation performance if their application is correct. Thermal insulation performance is caused by reduction of the heat transfer by radiation. Conjunction of low-emissivity surface of the reflective insulation and air layer is important to account. This article is focused on the determination of thermal properties of reflective insulation and the results of measured values thermal resistance of determination by hot box method using heat flow meter are presented here. As part of determination of thermal properties of reflective insulation by experimental methods, the test element used to measure the thermal resistance of an insulated air cavity had to be created for concordance with the normative requirements. The part of this article is determination of the thermal resistance by the calculation of derived physical relations and comparison with values of the laboratory measurement.

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Thermal Properties of Mannitol Derivative

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1126.181 ◽

2015 ◽

Vol 1126 ◽

pp. 181-186 ◽

Cited By ~ 5

Author(s):

Lucie Trhlikova ◽

Oldrich Zmeskal ◽

Radek Prikryl ◽

Pavel Florian

Keyword(s):

Thermal Properties ◽

Heat Exchangers ◽

Food Industry ◽

Fractal Model ◽

Thermal Parameters ◽

Crystalline Powder ◽

Sample Heating ◽

Potential Applications ◽

Change Temperature

Mannitol is an alcoholic sugar that is commonly used in the food industry. It is a white, odorless crystalline powder. Its melting temperature is about 168 °C. It is possible to be used also for the accumulation of energy in the heat exchangers based on oils. On its basis is sold a product PlusICE A164 of company PCM Products Ltd. (T = 164 °C, cp = 2.42 kJ.K-1 kg-1). Thermal properties of the material in both, solid and liquid phase were investigated for this purpose in terms of potential applications. Temperature dependence of thermal parameters (thermal diffusivity, thermal conductivity, and specific heat) were determined using a transient (step-wise) method. Fractal model of heat transport was used for the determination of thermal parameters. This model is independent on the geometry and on the type of the sample heating, and includes heat losses too. The experiment confirms the phase change temperature about 168 °C.

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In Situ Testing and Analysis of Thermal Properties of the Ground Formation in Jiangsu, China

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.933.477 ◽

2014 ◽

Vol 933 ◽

pp. 477-481

Author(s):

Shuai Chen

Keyword(s):

Thermal Conductivity ◽

Thermal Properties ◽

Thermal Resistance ◽

Thermal Response ◽

Geological Structure ◽

Ground Source ◽

In Situ Conditions ◽

Thermal Conductivity Λ

Ground source heat pump (GSHP) systems exchange heat with the ground, often through a closed-loop, vertical, borehole heat exchanger (BHE). The performance of the BHE depends on the thermal properties of the ground formation, as well as soil or backfill in the borehole. The design and economic probability of GSHP systems need the thermal conductivity of geological structure and thermal resistance of BHE. Thermal response test (TRT) method allows the in-situ determination of the thermal conductivity (λ) of the ground formation in the vicinity of a BHE, as well as the effective thermal resistance (Rb) of this latter. Thermal properties measured in laboratory experiments do not comply with data of in-situ conditions. The present article describes the results of thermal properties of the BHE whose depth is 100m in Yancheng City, Jiangsu Province, China. As shown in these results, λ and Rb of borehole are determined as 1.84(W·m-1·K-1) and 0.121 (m·K·W-1) respectively.

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