US 4,436,674 A · Vapor mass flow control system

Abstract

In a system for delivering vapor from a container partially filled with liquid to be vaporized by bubbling a carrier gas therethrough, the flow of the vapor is precisely regulated by a controller so as to provide a uniform mass flow rate of vapor. The controller is programmed to receive signals representing the sensing of the total gaseous pressure, temperature and liquid level in the container and to use the signals in a computation according to the following formula: m*=AF.sub.c (1+B.DELTA.T-C.DELTA.P-DF.sub.c +E.DELTA.L) wherein m*=Approximate vapor mass flow F.sub.c =Carrier gas mass flow .DELTA.T=Temperature variation from nominal (T-T.sub.o) .DELTA.P=Pressure variation from nominal=(P-P.sub.o) .DELTA.L=Charge in liquid level=-.intg.m*dt A,B and C=Positive constants computed for each chemical and nominal operating conditions; and D and E=Positive or negative constants computed for each chemical and nominal operating conditions. A, B and C=Positive constants computed for each chemical and nominal operating conditions; D and E=Positive or negative constants computed for each chemical and nominal operating conditions.

Claims10

Dependent claims

In a chemical vapor delivery system including a container partially filled with material to be vaporized and applied to a system which uses the vapor, means for ducting a carrier gas through said material to transport said vaporized material, a valve for controlling the flow of said carrier gas to said container, and means for controlling the temperature of the material in said container, an improved method comprising:

providing a continuous, uniform mass flow of said vaporized material to said using system by:
sensing the total gaseous pressure (P) in said container;
comparing said sensed pressure (P) with a reference pressure (P.sub.o) to provide a pressure differential (.DELTA.P=P-P.sub.o);
generating a signal in a vapor mass flow controller utilizing said pressure differential (.DELTA.P) in a computation by the controller wherein, as the differential becomes more positive, said computation demands an increase in carrier gas flows;
and
transmitting said signal to said flow control valve, said signal adjusting said flow control valve to control the carrier gas flow to provide said continuous uniform mass flow of said vaporized material.

3 more elements

A chemical vapor delivery system comprising:

a bubbler container for holding a quantity of high purity liquid to be vaporized and applied to a using system;
means for transporting a carrier gas through said liquid to transport the vaporized material to the using system;
means for sensing the carrier gas flow rate;
valve means for controlling the flow of said carrier gas;
means for sensing and controlling the temperature of said liquid;
means for sensing the total gaseous pressure in said container;
and
controller means connected to receive the sensed carrier gas flow rate, the sensed temperature and the sensed pressure and to compare the sensed pressure (P) with a reference pressure (P.sub.o) to provide a pressure differential (.DELTA.P=P-P.sub.o), said controller generating a signal in a computation wherein, as the differential (.DELTA.P) becomes more positive, said computation demands an increase in carrier gas flow rate, said signal for controlling said carrier gas flow control valve means in a manner to produce a continuous, uniform mass flow of said vaporized liquid to said using system.

5 more elements

Dependencies are inferred from the claim text.

Vapor mass flow control system

Life of this patent

Vapor mass flow control system

Life of this patent

Abstract

Claims10