Tangwongsan Chanchana, Chachati Louay, Webster John G, Farrell Patrick V
Department of Electrical Engineering, Chulalongkorn University Phaya-Thai Road, Bangkok 10330, Thailand.
Biomed Eng Online. 2006 Oct 26;5:57. doi: 10.1186/1475-925X-5-57.
We need a sensor to measure the convective heat transfer coefficient during ablation of the heart or liver.
We built a minimally invasive instrument to measure the in vivo convective heat transfer coefficient, h in animals, using a Wheatstone-bridge circuit, similar to a hot-wire anemometer circuit. One arm is connected to a steerable catheter sensor whose tip is a 1.9 mm x 3.2 mm thin film resistive temperature detector (RTD) sensor. We used a circulation system to simulate different flow rates at 39 degrees C for in vitro experiments using distilled water, tap water and saline. We heated the sensor approximately 5 degrees C above the fluid temperature. We measured the power consumed by the sensor and the resistance of the sensor during the experiments and analyzed these data to determine the value of the convective heat transfer coefficient at various flow rates.
From 0 to 5 L/min, experimental values of h in W/(m2.K) were for distilled water 5100 to 13000, for tap water 5500 to 12300, and for saline 5400 to 13600. Theoretical values were 1900 to 10700.
We believe this system is the smallest, most accurate method of minimally invasive measurement of in vivo h in animals and provides the least disturbance of flow.
我们需要一种传感器来测量心脏或肝脏消融过程中的对流换热系数。
我们构建了一种微创仪器，使用类似于热线风速仪电路的惠斯通电桥电路来测量动物体内的对流换热系数h。其中一个臂连接到一个可操纵的导管传感器，其尖端是一个1.9毫米×3.2毫米的薄膜电阻温度探测器（RTD）传感器。我们使用循环系统在39摄氏度下模拟不同流速，使用蒸馏水、自来水和盐水进行体外实验。我们将传感器加热到比流体温度高约5摄氏度。我们在实验过程中测量了传感器消耗的功率和传感器的电阻，并分析这些数据以确定不同流速下的对流换热系数值。
在0至5升/分钟的范围内，蒸馏水的h实验值（单位为W/(m2.K)）为5100至13000，自来水为5500至12300，盐水为5400至13600。理论值为1900至10700。
我们认为该系统是测量动物体内h的最小、最准确的微创方法，并且对血流的干扰最小。
