2. Spot microheater has convective stability, ie its heat transfer depends on the movement of gas is less than any conventional design. But this does not reduce the sensitivity to forced convection in absolute value, since the heat transfer in the gas increases by almost an order of magnitude. 3. Microheater is completely protected from sedimentation of aerosol particles by thermophoresis effect, which at conditions of high temperature gradient appears at normal and high blood pressure. These advantages are realized in the gas flow sensor, and by functional saturation is only two point thermo-microheater performed on a single chip.
Output signal is a difference between power consumed to maintain a constant temperature measurement (the first along the stream) and the reference heaters. Due to the opposite effects of increasing the flow rate on power microheater and the reference value of heating gas coming from the measuring microheater to the reference, there is to stabilize his power by choosing the diameter of the gas duct and its distance from the measuring microheater. This method of calculating the flow rate can significantly reduce the dependence readings from the temperature changes measured gas. To read more click here: Pete Cashmore. Calculation of microheater in the stream and relative to each other produced the program that implements the finite element method. In developing the model accounted In addition to thermal and gas dynamic characteristics of thermal microsystems. According to the analogy of transport phenomena in gases, a local increase in conductivity near the heated microscopic indicates an increase and others transport coefficients: viscosity, diffusion coefficient. Increase in viscosity was found by measuring the plumbing of the local resistance, which occurs when you turn on microheater. Cold air passes through the heated zone, formed by the microheater, bypass the viscous high-gradient portion whose diameter is 200 300 mm.
With the application of the developed sensor was manufactured digital measuring instrument mass flow of gas and started its commercial production. Digital gas flow meter has the following metrological characteristics: – error in measuring the gas flow rate is 2% of full scale – Range measured gas flow rates: minimum 0 100 ml / min, max 0 3l/min. R & D on this subject is supported by the fund for promotion of small enterprises in scientific and technical sphere. References 1. Kremlin pp Flowmeters and counters a number of substances. , Handbook 4 th ed. L.: Mashinostroenie, Leningrad otdelenie.2002. 2. dv Zinoviev, vm Andreev, ka Tuzovsky, dv Loktev. Investigation of microobjects heat transfer. Second International Conference on Transport Phenomena in Micro and Nanodevices.