Development of measurement technology for surface heat fluxes and temperatures

伝熱面表面熱流束・温度計測技術の開発; 沸騰における伝熱面温度・熱流束の計測

Liu, W.; 高瀬 和之

Liu, W.; Takase, Kazuyuki

沸騰メカニズムを把握するために、流れを乱す伝熱面上へのセンサーの設置が不要で、伝熱面温度・熱流束を同時計測できるシステムを開発した。本計測システムは、高速度で伝熱体内部温度を計測する一次系と、多チャンネルで計測される伝熱体内部温度データをもとに伝熱面温度と熱流束の変化を逆問題解析によって求める二次系から構成される。本研究では、逆問題解析を用いて現象の早い非定常沸騰サイクルを追従できるように、共同陽極を持つ微細熱電対群を導入することによって、伝熱面表面から数ミクロンの深さに温度計測用温度接点を配置することができた。本報では、開発したシステムを用いて、半無限体逆問題解析を適用して沸騰サイクルにおける気泡直下の伝熱面表面熱流束と表面温度を計測した。本開発の計測システムによって、大きな変形した気泡の形成に伴う伝熱面温度の低下や熱流束の上昇を計測できることがわかった。

A system for measuring the surface temperature and the surface heat flux of a heating block was developed that has no need for a sensor set on the surface. The system consisted of two parts: (1) inner block temperatures were measured using micro-thermocouples; (2) using the measured temperatures, an inverse heat conduction problem was solved to get the surface heat flux and surface temperature. For the inner block temperature measurement, special T-type micro thermocouples with a common positive pole were developed. A total of 10 thermocouples were set at a depth of 3.1 m beneath the boiling surface, in a circle with a radius of 5 mm. The developed system was used to measure the change of surface heat flux and surface temperature in a pool nucleate boiling process. Experiments were performed at atmospheric pressure. The experiments showed that the developed special T-type micro thermocouples can successfully measure the temperature change in a boiling process. By using the measured temperature, a semi-infinite inverse heat conduction problem was solved to get the surface heat flux and surface temperature. The change in surface heat flux and surface temperature in a bubble cycle was derived.