为Why is the RTD temperature sensor installed behind the orifice plate?

The position RTD temperature sensor (thermocouple), so the turbulence generated by it will not create additional turbulence in the orifice plate and be positioned downstream of the orifice plate. Industry standards allow placement of thermowells upstream, provided they are at least three feet upstream of the flow regulator.
One of the main reasons for this is vortex shedding, which is caused by the gas must flow around the width of the heat pipe. Unless the vortex cannot reach the orifice through the flow regulator or by placing the thermowell downstream, the vortex "street" generated by the thermowell will cause severe pressure fluctuations at the orifice.