Feedback control optimization of counter-flow simultaneous heat and mass exchange

Patent metadata

Field	Value
Publication number	US-11052326-B2
Application number	US-202016882608-A
Country	US
Kind code	B2
Filing date	May 25, 2020
Priority date	Dec 18, 2013
Publication date	Jul 6, 2021
Grant date	Jul 6, 2021

Abstract

A counter-flow simultaneous heat and mass exchange device is operated by directing flows of two fluids into a heat and mass exchange device at initial mass flow rates where ideal changes in total enthalpy rates of the two fluids are unequal. At least one of the following state variables in the fluids is measured: temperature, pressure and concentration, which together define the thermodynamic state of the two fluid streams at the points of entry to and exit from the device. The mass flow rate of at least one of the two fluids is changed such that the ideal change in total enthalpy rates of the two fluids through the device are brought closer to being equal.

First claim

What is claimed is:

1. A humidification-dehumidification device, comprising:
a humidifier including a carrier-gas inlet, a carrier-gas outlet, a feed-liquid inlet, and a brine outlet, wherein the humidifier is configured to transfer a vaporized component from feed liquid that is input through the feed-liquid inlet to carrier gas that is input through the carrier-gas inlet in counter-flow to the feed liquid;
a condenser including a carrier-gas inlet, a carrier-gas outlet, a liquid inlet for condensing-bath liquid, and a liquid outlet for the condensing-bath liquid and condensate, wherein the condenser is configured to transfer the vaporized component from the carrier gas input through the carrier-gas inlet as a condensate to the condensing-bath liquid in counter-flow to the condensing-bath liquid;
a carrier-gas conduit connecting the carrier-gas outlet of the humidifier with the carrier-gas inlet of the condenser;
sensors, including (a) at least one flow-rate sensor configured to detect a flow rate of at least one of the carrier gas, the feed liquid, and the condensing-bath liquid and (b) sensors configured to detect at least one of the following state variables in the carrier-gas conduit at the carrier-gas inlet of the humidifier, at the liquid inlet and outlet of the condenser, and at the feed-liquid inlet and brine outlet of the humidifier: temperature, pressure and concentration;
at least one carrier-gas flow controller configured to control the flow of carrier gas in the carrier-gas conduit; and
at least one liquid-flow controller configured to control the flow of at least one of the feed liquid through the humidifier and the condensing-bath liquid through the condenser;
an automated controller comprising computer-readable memory in communication with a processor, wherein the sensors and the flow controller are in communication with the automated controller, and wherein the computer-readable memory stores software code for:
generating and communicating commands to the carrier-gas flow controller to flow carrier gas through the humidifier and condenser;
generating and communicating commands to the liquid-flow controller to control flow, in cross-flow to the carrier gas flow, of at least one of (a) feed liquid through the humidifier and (b) condensing-bath liquid through the condenser;
calculating ideal changes in total enthalpy rates of the carrier gas and at least one of the feed liquid and the condensing-bath liquid in at least one of the humidifier and the condenser based on at least one state variable communicated by the sensors to the automated controller and the difference between the ideal changes in total enthalpy rates;
identifying a change in flow rate of at least one of the carrier gas, the feed liquid, and the condensing-bath liquid in at least one of the humidifier and the condenser that will bring the ideal change in total enthalpy rates of the carrier gas and at least one of the condensing-bath liquid and the feed liquid closer to zero; and
based on at least some of the detections by the sensors and the identified change in flow rate, generating and sending commands to at least one of the carrier-gas flow controller and the liquid-flow controller to control the mass flow of at least one of the carrier gas, the feed liquid, and the condensing-bath liquid to achieve the identified change in flow rate to bring the ideal change in total enthalpy rates of the carrier gas and at least one of feed liquid and the condensing-bath liquid through at least one of the humidifier and the condenser closer to being equal.

2. The humidification-dehumidification device of claim 1 , wherein at least one liquid-flow controller is configured to control flow of the condensing-bath liquid through the condenser, the humidification-dehumidification device further comprising:
a first liquid conduit coupled with the liquid inlet of the condenser; and
a second liquid conduit coupled with the liquid outlet of the condenser, wherein sensors for detecting at least one of the variables are in at least one of the first and second liquid conduits, and wherein the software code includes instructions for calculating a heat capacity ratio based on a detected state variable in at least one of the first or second liquid conduit and generating and sending commands to the liquid flow controller to control the flow of the condensing-bath liquid as a function of the calculated heat capacity ratio.

3. The humidification-dehumidification device of claim 2 , wherein at least one of the condenser and the humidifier includes a plurality of stages, and wherein at least one sensor for detecting a state variable is mounted between stages, the device further comprising:
an intermediate exchange conduit connecting intermediate in the condenser and humidifier;
a sensor for detecting a state variable in the intermediate exchange conduit; and
a flow-rate sensor for detecting the flow rate of fluid in the intermediate exchange conduit;
a flow controller for controlling the flow of fluid through the intermediate exchange conduit between the humidifier and condenser,
wherein the software code includes instructions for calculating the heat capacity ratio based on a detected state variable in the intermediate exchange conduit.

4. The humidification-dehumidification device of claim 3 , wherein the stages comprise bubble columns through which at least one of the fluids can be bubbled.

5. The humidification-dehumidification device of claim 1 , wherein the commands generated by the software code calculate a ratio of the change in idealized enthalpy difference of water as the condensing-bath liquid and the idealized enthalpy difference of air as the carrier gas.

6. The humidification-dehumidification device of claim 5 , wherein the software code includes instructions for calculating the ratio based on the state variable measurements from the sensors and on the flow-rate measurements from the flow-rate sensors and for sending commands to change the flow rate of at least one of the fluids as a function of the calculated ratio.

7. The humidification-dehumidification device of claim 6 , wherein the software code includes instructions for iteratively calculating the ratio and sending commands to change the flow rate if the ratio is not within a specified margin of error of 1.

8. The humidification-dehumidification device of claim 1 , wherein at least one flow-rate sensor is configured to detect the flow rate of carrier gas at the carrier-gas inlet of the humidifier.

9. A method of operating a counter-flow simultaneous heat and mass exchange device, the method comprising:
directing flows of two fluids through inlets into the heat and mass exchange device and through outlets of the heat and mass exchange device at initial mass flow rates where ideal changes in total enthalpy rates of the two fluids are unequal;
measuring a flow rate of at least one of the fluids;
measuring at least one of the following state variables in the fluids at the inlets and outlets of the heat and mass exchange device: temperature, pressure and concentration, which together define the thermodynamic states of the two fluid streams at the points of entry to and exit from the device; and
changing the mass flow rate of at least one of the two fluids in response to a plurality of the measurements such that the ideal change in total enthalpy rates of the two fluids through the device are brought closer to being equal.

10. The method of claim 9 , wherein the heat and mass exchange device is a condenser that condenses a vapor from a humidified carrier gas.

11. The method of claim 10 , wherein the vapor is water.

12. The method of claim 9 , wherei

Assignees

• Gradiant Corp

Inventors

• Govindan Prakash Narayan
• St John Maximus G
• Chehayeb Karim M
• Lam Steven

Classifications

• B01F23/214

  using a gas-liquid mixing column or tower · CPC title

• C02F1/008

  Control or steering systems not provided for elsewhere in subclass C02F · CPC title

• B01D3/16

  Fractionating columns in which vapour bubbles through liquid (packing elements B01J19/30, B01J19/32) · CPC title

• C02F1/043

  Details · CPC title

• B01D3/346

  the gas being used for removing vapours, e.g. transport gas · CPC title