Fluid temperature in a piping system can be accurately determined non-intrusively with pipe surface temperature and its correction factor. A new technique, called flux augmented surface temperature (FAST) method is proposed to determine the correction factor directly in real time, in situ. The correction factor is directly proportional to a heat flow through pipe wall. In FAST method, the proportional coefficient is directly calculated from 2 sets of surface temperature and heat flux measurements. Innovation in FAST method is a technique which creates 2 different thermal environments. These environments produce significantly different surface temperature and heat flow from each other, but they will leave no residual thermal disturbance to fluid or pipe. In FAST method, there are 2 heat flux sensors, both which can measure surface temperature and heat flux simultaneously. These sensors are equipped with heater and/or cooler, which are dynamically controlled in such a way that no heat will be generated or absorbed as net. FAST method is expected to produce response time and temperature accuracy comparable to a direct immersion method. FAST method and its heat flux sensor can be used many commercial applications as well as NASA rocket test facility, because of its easy installation.Three different types of non-intrusive fluid temperature sensors for piping systems with different ranges of price, accuracy and response time for hazardous waste treatment, pharmaceutical and biomedical industries and up-grading for general chemical, process and food-processing industries. New resistance type heat flux sensors with better accuracy and sensitivity for general industrial applications.temperature, surface, heat, flux, sensor, measurement, detector, fluid
