Development of Numerical Experimental Model for Heat Transfer in High Quality Region of Flow Boiling in Tube Evaporator with Twisted Tape-Insert

本研究的目标是开发一种数字实验模式，其中可以模拟管道蒸发器后区域的滴液的行为，在订购找到一种通过扭曲的胶带插入有效地降低该区域热量转移的方式，以减少所需的管道长度。使用计算机进行热转移和关键热通量（CHF）的研究。在refrigerant HFC 134 a were obtained for the horizontal flow conditions （mass flux 100-600 kg/m D12-D1 s）。以下结果已确定： （1）热转移特性和CHF之间的关系以及平滑管的关键质量（O.）D. D. 7毫米， I。D. D. 6. 34 mm）showed the similar tendencies to the results which had been obtained previously for the different flow conditions and refrigerants by the investigators。（2）Twi的热量转移增强的强度 ... More 胶带插入到饮用后区域内的光滑管中，符合质量的实验结果，其中一些被头部调查者发现用于制冷剂CHF 113。在数字分析中，一个模拟的行为是一个模拟的一个单一滴液在蒸汽机流动的一个带加热墙的碰撞通过修改后的VOF方法传送出来的相位变化是在蒸汽机液体接口上使用一个相位变化的帐户。结果显示，计算可以模拟水滴直到它与墙壁碰撞时的行为，以及细胞温度的定义，其中包含了接口影响到计算复杂性之外的计算的复杂性。在哪个水滴部形成墙壁没有找到的最相关的条件下，在添加中，一个使用热漆（温度感应漆）的简单方法，用温度改变了它的颜色，被提议测量管子外的表面温度剖面，并通过另一个实验确认它的可用性。Less（低）

This research aimed to develop a numerical experimental mode which can simulates behavior of droplets in the post-dryout region of flow boiling in tube evaporator, in order to find the way to the heat transfer enhancement in this region effectively by twisted tape-insert, which contributes to reducing the tube length required. The research was performed by experimental studies on heat transfer and critical heat flux(CHF)of the flow boiling, and by numerical analysis using computer.In the experiments data for refrigerant HFC134a were obtained for the horizontal flow conditions (mass flux 100-600 kg/mィイD12ィエD1s). The following results were clarified : (1)The heat transfer characteristics and the relation between CHF and the critical quality for a smooth tube(O. D. 7mm, I. D. 6.34mm)showed the similar tendencies to the results which had been obtained previously for the different flow conditions and refrigerants by the investigators. (2)Magnitude of the heat transfer enhancement by the twi … More sted tape inserted into the smooth tube in the post-dryout region agreed qualitatively with the experimental results which had been obtained for refrigerant CHF113 by the head investigator.In the numerical analysis a simulation of behavior of a single droplet in vapor flow which collides with heated wall was carried out by the modified VOF method which is taking account of phase change at the vapor-liquid interface. The results showed that the calculation could simulate behavior of the droplet until it collided with the wall, and the definition of temperature of the cell which included the interface affected the complexity of calculation beyond the investigators' expectation. However the most relevant condition at which the droplet departs form the wall has not been found.In addition, a simple method using Thermo-Paint(temperature sensing paint), which changes its color with temperature, was proposed to measure the surface temperature profile outside the tube, and was confirmed its usefulness by another experiment. Less