Etsuro Yamada

Numerical simulation of the effective thermal conductivity of wet clothing materials

Clothing materials may be considered composite materials composed of fiber, air, and moisture. For this paper, effective thermal conductivities of wet clothing materials were analyzed numerically using a proposed heat transfer model. The following simplifications were introduced. The clothing material fiber is woven with a single yarn, there is no air movement between fibers, and mass transfer is neglected. Numerical calculations were made using finite difference equations for steady three-dimensional heat conduction for several composite materials representing wet clothing materials. The main results obtained were as follows. The effective thermal conductivity of wet clothing material increases as the thermal conductivity of the yarn and the moisture content increase. We found that our numerical results agree qualitatively with those previously measured. The effective thermal conductivity of a wet layered material depends on the distribution of moisture and attains a maximum in the wet layer.

Thermal Energy Storage, Heat Pump and Thermal Energy Transportation Technologies. Measurement of Thermal Diffusivity of Foods by Unsteady Hot-Wire Method. Effect of Dispersion Conditions to the Dispersed Mixture.

本報は前報に引き継いで, 分散系混合物の粒子の分散状態を定量的に表現し, 温度伝導率に対する影響を明らかにすることを目的とした.実験方法は前報と同様な方法で温度伝導率を計測した試料から切片を採取し, その顕微鏡写真を取り, 画像解析を行った.粒子の分散状態はフラクタル次元を用いて評価し, 温度伝導率との関連について検討した.フラクタル次元は, 粒子の分散状態を表すには有効な手段であった.また, 温度伝導率への影響は, フラクタル次元の変化は勿論のこと, 母材の温度伝導率αcと分散材の温度伝導率αdとの比 (αd*=αc/αd) が1.0との大小によっても大きく変化した.

Effective Thermal Conductivity of Clothing Materials Coexisted with Conduction and Moisture Diffusion.

The effective thermal conductivity of the clothing materials in which heat flows accompany with mass transfer has been studied.The condition of this measurement may be more similar to practical use of the cloths.The experimental apparatus based upon the steady state comparison method is slightly modified in this study.The water tank is put on the heater and heat is flowed through the sample cloths upward from the heater that is placed at the bottom of the apparatus.The ordinary clothing materials used widely are selected as the sample.If the heater and the room temperature are kept constant, vapourizing rate η is scarcely independent of the number and the kind of cloths.The η, however, depends on the temperature difference between the heater and room temperature and relative humidity of the room.On the other hand, the temperature difference between upper and bottom surface of sample is nealy proportional to the number of cloths.Therefore, the effective thermal conductivity coexisting with heat conduction and mass diffusion may be evaluated by obtaining the sum of the thermal conductivity in the case that heat or mass transfers alone through the cloths.