Patent ID: 6964279

Claim:
A pressure-type flow rate control apparatus comprising: a pipe having a supply-side portion and a control-side portion; an orifice provided between the supply-side portion and the control-side portion of the pipe; a fluid flow rate calculation means for calculating a fluid flow rate Qc by Qc=KP 2 m ( P 1 −P 2 ) n , wherein K is a proportional constant; and m and n are constants having values of 0.40<m <0.50 and 0.50<n<0.65, respectively; P 1 is pressure upstream of the orifice and P 2 is pressure downstream of the orifice; an upstream pressure sensor provided on the supply-side portion of the pipe and between a control valve and the orifice, wherein the upstream pressure sensor is disposed to detect the pressure upstream P 1 and to send input to the fluid flow rate calculation means; and a downstream pressure sensor provided on the control-side portion of the pipe, wherein the downstream pressure sensor is disposed to detect the pressure downstream P 2 and to send input to the fluid flow rate calculation means; wherein the fluid flow rate calculation means is connected to send input used for controlling the control valve so as to adjust the actual flow rate of fluid passing through the orifice.