Abstract
This study discusses the feasibility of a non-intrusive flow measuring method, by heating the outer surface of the pipe with spot laser until steady state is reached. The flow rate is then calculated according to the temperature distribution of the pipe wall. The study includes experiment and numerical simulation. At various flow rates, the outer surface of the pipe is heated with spot laser in the experiment, then the temperature distribution around the heat spot is measured by an infrared camera. Numerical simulation is conducted and compared with the experimental results. Since the heating area and heating power are relatively small, the temperature distribution of the outer surface of the pipe is dominated by heat conduction. The effect of heat convection appears insignificant and only the slowly-moving fluid near the pipe wall is heated by the spot laser. Since the heat is not effectively carried downstream, changing flow rate exerts little effect on the temperature distribution. Experimental and simulation results show little changes of less than 3% in temperature distribution for wide variation of flow rate. Therefore the feasibility of this flow measuring method is questionable. However, improvement may be attained by using lower-thermal-conductivity wall materials, thinner pipe wall, and larger size and power of the heat source.