Thermodynamic balancing of combined heat and mass exchange devices

Patent metadata

Field	Value
Publication number	US-9416800-B2
Application number	US-201313924732-A
Country	US
Kind code	B2
Filing date	Jun 24, 2013
Priority date	Jul 16, 2012
Publication date	Aug 16, 2016
Grant date	Aug 16, 2016

Abstract

A carrier-gas mixture is directed through a fluid flow path in a combined heat and mass transfer device, which can be operated at sub-atmospheric pressure. Heat and mass are transferred from or to the carrier-gas mixture via interaction with a liquid composition that includes a vaporizable component in a liquid state to substantially change the content of the vaporizable component in the carrier-gas mixture via evaporation or condensation. The mass flow rate of the carrier-gas mixture is varied by extracting or injecting the carrier-gas mixture from at least one intermediate location in the fluid flow path, and/or the mass flow rate of the liquid composition is varied by extracting or injecting the liquid composition from at least one intermediate location in the fluid flow path; and the flow of the carrier-gas mixture or the liquid composition is regulated to reduce the average local enthalpy pinch in the device.

First claim

What is claimed is:

1. A method for reducing thermodynamic irreversibilities in a combined heat and mass transfer device, the method comprising:
directing a flow of a carrier-gas mixture through a fluid flow path in a combined heat and mass transfer device operating at a pressure at about ambient atmospheric pressure and at least as great as ambient atmospheric pressure;
transferring heat and mass from or to the carrier-gas mixture by a direct or indirect interaction with a liquid composition that includes a vaporizable component in a liquid state to substantially change the content of the vaporizable component in the carrier-gas mixture via evaporation of the vaporizable component from the liquid composition or via condensation of the vaporizable component from the carrier-gas mixture, producing a flow of carrier-gas mixture having a concentration of the vaporizable component that differs from the concentration of the vaporizable component in the carrier-gas mixture before the heat and mass transfer process;
varying the mass flow rate of at least one of (a) the carrier-gas mixture by extracting or injecting the carrier-gas mixture from at least one intermediate location in the fluid flow path in the combined heat and mass transfer device and (b) the liquid composition by extracting or injecting the liquid composition from at least one intermediate location in the fluid flow path in the heat and mass transfer device; and
regulating the flow of the carrier-gas mixture or the liquid composition in the combined heat and mass transfer device to reduce the average local enthalpy pinch in the device.

2. The method of claim 1 , wherein the minimum local enthalpy pinch in the device is less than about 27 kJ/kg dry air.

3. The method of claim 1 , the flow of the carrier-gas mixture or the liquid composition is dynamically varied.

4. The method of claim 1 , wherein the liquid composition is heated to a temperature not exceeding the precipitation temperature of scaling components in the liquid composition.

5. The method of claim 1 , wherein the vaporizable component is water.

6. The method of claim 1 , wherein the combined heat and mass transfer device is operating at a pressure that is no more than 5% greater than ambient atmospheric pressure.

7. A method for reducing thermodynamic irreversibilities in a humidification-dehumidification system, the method comprising:
directing a flow of a carrier-gas mixture comprising a vaporizable component and a carrier gas through a fluid-flow path in a packed bed humidifier;
transferring heat and mass to the carrier-gas mixture by a direct interaction with a liquid composition comprising the vaporizable component in a liquid state as one of its components to substantially increase the content of the vaporizable component in the carrier-gas mixture via evaporation of vaporizable component from the liquid composition;
directing the carrier-gas mixture from the humidifier to a dehumidifier operating at a pressure at about ambient atmospheric pressure and at least as great as ambient atmospheric pressure, wherein heat and mass are transferred from the carrier-gas mixture by an indirect interaction with the liquid composition in a fluid-flow path in the dehumidifier, reducing the content of the vaporizable component in the carrier-gas mixture and preheating the liquid composition;
varying the mass flow rate of at least one of (a) the carrier-gas mixture by extracting the carrier-gas mixture from at least one intermediate location in the fluid-flow path in the humidifier and injecting the extracted carrier-gas mixture at a corresponding location in the dehumidifier and (b) the liquid composition by extracting the liquid composition from at least one intermediate location in the fluid-flow path in the humidifier and injecting the liquid composition at a corresponding location in the dehumidifier; and
regulating the flow of the carrier-gas mixture or of the liquid composition between the intermediate locations of the fluid flow paths in the humidifier and the dehumidifier to reduce the average local enthalpy pinch in the dehumidifier.

8. The method of claim 7 , wherein the humidifier and the dehumidifier operate with a minimum enthalpy pinch less than about 27 kJ/kg dry air.

9. The method of claim 7 , wherein the extractions and injections of the carrier-gas mixture or liquid composition occur along one or more discrete conduits extending between intermediate locations in the fluid-flow paths in the humidifier and in the dehumidifier.

10. The method of claim 7 , wherein the extractions and injections of the carrier-gas mixture or the liquid composition between the fluid-flow paths in the humidifier and in the dehumidifier occur along intermediate locations extending continuously across a majority of the fluid-flow paths in the humidifier and in the dehumidifier.

11. The method of claim 7 , wherein the humidifier and the dehumidifier are operated in a state of thermodynamic balancing that is closer to a state of constant local-humidity-ratio difference than to a state of constant stream-to-stream temperature difference.

12. The method of claim 7 , wherein the rate of flow of carrier-gas mixture or liquid composition between intermediate locations is dynamically varied.

13. The method of claim 7 , wherein the liquid composition is heated to a temperature not exceeding the precipitation temperature of scaling components in the liquid composition.

14. The method of claim 13 , wherein the pressure of the humidifier and the dehumidifier is selected and established based on the vapor pressure of water at the temperature of the liquid composition.

15. The method of claim 14 , wherein the liquid composition is heated to a temperature no greater than 65° C.

16. The method of claim 13 , wherein the scaling components include at least one of calcium sulphate and magnesium sulphate.

17. The method of claim 13 , wherein the scaling components include at least one of calcium carbonate and bicarbonate.

18. The method of claim 7 , wherein the vaporizable component is water.

19. The method of claim 7 , wherein the dehumidifier is operating at a pressure that is no more than 10% greater than ambient atmospheric pressure.

20. The method of claim 7 , wherein the dehumidifier is operating at a pressure that is within no more than within 5% greater than ambient atmospheric pressure.

Assignees

• Govindan Prakash Narayan
• Thiel Gregory P
• Mcgovern Ronan K
• Lienhard John H
• Das Sarit K
• Chehayeb Karim M
• Zubair Syed M
• Antar Mohammed A
• Massachusetts Inst Technology
• King Fahd Univ Of Petroleum Minerals

Inventors

• Govindan Prakash Narayan
• Thiel Gregory P
• Mcgovern Ronan K
• Lienhard John H
• Das Sarit K
• Chehayeb Karim M
• Zubair Syed M
• Antar Mohammed A

Classifications

• B01D1/0058 Primary

  Use of waste energy from other processes or sources, e.g. combustion gas (for water treatment C02F1/16) · CPC title

• B01D1/0082

  Regulation; Control · CPC title

• B01D1/14

  with heated gases or vapours {or liquids} in contact with the liquid · CPC title

• B01D5/0051

  Regulation processes; Control systems, e.g. valves · CPC title

• C02F1/12

  Spray evaporation · CPC title