US 2003/0110853 A1Published application

Critical gas flow measurement apparatus and method

AssigneeCalAmerica Corp.

InventorPierre R. Delajoud

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Abstract

A gas mass flow meter includes an elongated channel extending through a high thermal mass body and a critical flow nozzle in a downstream portion of the channel. A heat exchanger is provided upstream in the channel. Gas is forced through the heat exchanger and the critical flow nozzle at a flow rate of up to 5000 slm and at sufficiently high-pressure to ensure critical flow of the gas through the critical flow nozzle. The heat exchanger brings the gas close to the temperature of the high thermal mass body. The pressure of the gas is measured upstream and downstream from the nozzle and the temperature of the gas emerging from the heat exchanger is measured. The mass flow rate of gas through critical flow nozzle is computed from the upstream pressure, downstream pressure, temperature of the high thermal mass body, density of the gas, and a dimensional characteristic of the critical flow nozzle.

Claims58

Dependent claims

A method for measuring gas flow, comprising:

(a) providing an integrated unit including
i. an elongated fluid flow channel extending through a high thermal mass body,
ii. a nozzle in a downstream portion of the channel in close thermal contact with the high thermal mass body,
iii. a heat exchanger in an upstream portion of the channel in close thermal contact with the high thermal mass body,
iv. structure associated with the heat exchanger for straightening flow of gas in the upstream portion of the channel,
vi. a temperature probe associated with the upstream portion of the channel, a pressure probe in the upstream portion of the channel, and a pressure probe downstream from the nozzle;
(b) forcing gas to flow into an upstream portion of the channel and through the gas straightening structure and the heat exchanger to ensure flow of the gas through the nozzle, wherein the heat exchanger brings a temperature of gas emerging from the heat exchanger close to a temperature of the high thermal mass body;
(c) measuring a pressure of the gas in the upstream portion of the channel, and measuring a pressure of the gas in the channel downstream from the nozzle;
(d) determining a temperature of gas upstream from the nozzle;
and
(e) computing the mass flow rate of gas through the nozzle from the upstream pressure and upstream temperature of the gas, the difference between the pressure of the gas in the upstream portion of the channel and the pressure of the gas in the channel downstream from the nozzle, and a throat diameter of the nozzle.

8 more elements

A method for measuring gas flow, comprising:

(a) providing an integrated unit including
i. an elongated fluid flow channel extending through a high thermal mass body,
ii. a critical flow nozzle in a downstream portion of the channel,
iii. a heat exchanger in an upstream portion of the channel in close thermal contact with the high thermal mass body,
iv. structure associated with the heat exchanger for straightening flow of gas in the upstream portion of the channel,
vi. a temperature probe associated with the upstream portion of the channel, a pressure probe in the upstream portion of the channel, and a pressure probe downstream from the critical flow nozzle;
(b) forcing gas to flow into an upstream portion of the channel and through the gas straightening structure and the heat exchanger at a sufficiently high pressure to ensure critical flow of the gas through the critical flow nozzle, wherein the heat exchanger brings a temperature of gas emerging from the heat exchanger close to a temperature of the high thermal mass body;
(c) measuring a pressure of the gas in the upstream portion of the channel;
(d) determining a temperature of gas emerging from the heat exchanger upstream from the critical flow nozzle by means of the temperature probe;
and
(e) computing the mass flow rate of gas through the critical flow nozzle from the upstream pressure, the temperature of the gas emerging from the heat exchanger, and a throat diameter of the critical flow nozzle.

8 more elements

A device for measuring gas flow, comprising:

(a) an integrated unit including
i. an elongated fluid flow channel extending through a high thermal mass body,
ii. a critical flow nozzle in a downstream portion of the channel,
iii. a heat exchanger in an upstream portion of the channel in close thermal contact with the high thermal mass body,
iv. a flow straightener associated with the upstream portion of the channel,
vi. a temperature probe in the upstream portion of the channel, a pressure probe in the upstream portion of the channel, and a pressure probe downstream from the critical flow nozzle;
(b) means for forcing gas to flow into an upstream portion of the channel and through the heat exchanger at a sufficiently high pressure to ensure critical flow of the gas through the critical flow nozzle, wherein the heat exchanger brings a temperature of gas emerging from the heat exchanger close to a temperature of the high thermal mass body;
(c) means for measuring a pressure of the gas in the upstream portion of the channel;
(d) means, including the temperature probe, for determining a temperature of gas emerging from the heat exchanger upstream from the critical flow nozzle;
and
(e) means for computing the mass flow rate of gas through the critical flow nozzle from the upstream pressure, the temperature of the gas emerging from the heat exchanger, and a throat diameter of the critical flow nozzle.

8 more elements

A method for measuring gas flow, comprising:

(a) providing an elongated fluid flow channel extending through a high thermal mass body;
(b) providing a critical flow nozzle in a downstream portion of the channel;
(c) providing a heat exchanger in the upstream portion of the channel in close thermal contact with the high thermal mass body;
(d) forcing gas to flow into an upstream portion of the channel and through the heat exchanger at a sufficiently high pressure to ensure critical flow of the gas through the critical flow nozzle, the heat exchanger bringing a temperature of gas emerging from the heat exchanger to a value essentially equal to a temperature of the high thermal mass body;
(e) measuring a pressure of the gas in the upstream portion of the channel and ensuring that the pressure of the gas in the upstream portion of the channel sufficiently exceeds a pressure of the gas downstream from the critical flow nozzle to ensure sonic flow of the gas through the critical flow nozzle;
(f) measuring a temperature of a portion of the high thermal mass body adjacent to the upstream portion of the channel;
and
(g) computing the mass flow rate of gas through the critical flow nozzle from the upstream pressure, temperature of the high thermal mass body, and a dimensional characteristic of the critical flow nozzle.

5 more elements

A method for measuring gas flow, comprising:

(a) providing an elongated fluid flow channel extending through a high thermal mass body;
(b) providing a critical flow nozzle in a downstream portion of the channel;
(c) providing a heat exchanger in the upstream portion of the channel in close thermal contact with the high thermal mass body;
(d) forcing gas to flow into an upstream portion of the channel and through the heat exchanger at a sufficiently high pressure to ensure critical flow of the gas through the critical flow nozzle, the heat exchanger bringing a temperature of gas emerging from the heat exchanger close to a temperature of the high thermal mass body;
(e) measuring a pressure of the gas in the upstream portion of the channel, and ensuring that the pressure of the gas in the upstream portion of the channel sufficiently exceeds a pressure of the gas downstream from the critical flow nozzle to ensure sonic flow of the gas through the critical flow nozzle;
(f) measuring a temperature of gas emerging from the heat exchanger upstream from the critical flow nozzle;
and
(g) computing the mass flow rate of gas through the critical flow nozzle from the upstream pressure, the temperature of the gas, and a dimensional characteristic of the critical flow nozzle.

5 more elements

A device for measuring gas flow, comprising:

(a) an elongated fluid flow channel extending through a high thermal mass body;
(b) a critical flow nozzle in a downstream portion of the channel;
(c) a heat exchanger in the upstream portion of the channel in close thermal contact with the high thermal mass body;
(d) a gas source forcing gas to flow into an upstream portion of the channel and through the heat exchanger at a sufficiently high pressure to ensure critical flow of the gas through the critical flow nozzle, the heat exchanger bringing a temperature of gas emerging from the heat exchanger to a value essentially equal to a temperature of the high thermal mass body;
(e) a first pressure transducer connected in fluid communication with the upstream portion of the channel to measure a pressure of the gas in the upstream portion of the channel;
(f) a temperature transducer connected to measure a temperature of a portion of the high thermal mass body adjacent to the upstream portion of the channel;
and
(g) a processor programmed for computing the mass flow rate of gas through the critical flow nozzle from the upstream pressure, temperature of the high thermal mass body, and a dimensional characteristic of the critical flow nozzle.

5 more elements

A device for measuring gas flow, comprising:

(a) an elongated fluid flow channel extending through a high thermal mass body;
(b) a critical flow nozzle in a downstream portion of the channel;
(c) a heat exchanger in the upstream portion of the channel in close thermal contact with the high thermal mass body;
(d) a gas source forcing gas to flow into an upstream portion of the channel and through the heat exchanger at a sufficiently high pressure to ensure critical flow of the gas through the critical flow nozzle, the heat exchanger bringing a temperature of gas emerging from the heat exchanger close to a temperature of the high thermal mass body;
(e) a first pressure transducer connected in fluid communication with the upstream portion of the channel to measure a pressure of the gas in the upstream portion of the channel;
(f) a temperature transducer connected to measure a temperature of gas emerging from the heat exchanger upstream from the critical flow nozzle;
and
(g) a processor programmed for computing the mass flow rate of gas through the critical flow nozzle from the upstream pressure, the temperature of the gas, and a dimensional characteristic of the critical flow nozzle.

5 more elements

Dependencies are inferred from the claim text.