Liquid-to-air membrane energy exchanger

Patent metadata

Field	Value
Publication number	US-9234665-B2
Application number	US-201113702596-A
Country	US
Kind code	B2
Filing date	Jun 22, 2011
Priority date	Jun 24, 2010
Publication date	Jan 12, 2016
Grant date	Jan 12, 2016

Abstract

An energy exchanger is provided. The exchanger includes a housing having a front and a back. A plurality of panels forming desiccant channels extend from the front to the back of the housing. Air channels are formed between adjacent panels. The air channels are configured to direct an air stream in a direction from the front of the housing to the back of the housing. A desiccant inlet is provided in flow communication with the desiccant channels. A desiccant outlet is provided in flow communication with the desiccant channels. The desiccant channels are configured to channel desiccant from the desiccant inlet to the desiccant outlet in at least one of a counter-flow or cross-flow direction with respect to the direction of the air stream.

First claim

What is claimed is:

1. An energy exchanger comprising:
a housing constructed to meet a predetermined exchanger aspect ratio;
a plurality of panels extending through the housing, the panels having a semi-permeable membrane forming an energy exchange area of the panel, the panels forming desiccant channels and air channels that are separated by the semi-permeable membranes to facilitate contact between an air stream flowing through the air channels and desiccant flowing through the desiccant channels within the energy exchange areas of the panels, the energy exchange area of each panel having a top and a bottom, a height of the energy exchange area defined between the top and the bottom, the energy exchange area of each panel having a front and a back, a length of the energy exchange area defined between the front and the back, the exchanger aspect ratio being defined by the height of the energy exchange area of each panel divided by the length of the energy exchange area of each panel;
a desiccant inlet in flow communication with the desiccant channels; and
a desiccant outlet in flow communication with the desiccant channels, the desiccant channels configured to channel the desiccant from the desiccant inlet to the desiccant outlet in at least one of a counter-flow or cross-flow direction with respect to the direction of the air stream to facilitate heat and water vapor transfer through the semi-permeable membranes, the exchanger aspect ratio selected to provide at least one of a predetermined membrane area, a predetermined length, or a predetermined duration of exposure of the air stream to the desiccant.

2. The energy exchanger of claim 1 , wherein the exchanger aspect ratio is within a range of 0.5 to 2.

3. The energy exchanger of claim 1 , wherein the desiccant inlet is offset from the desiccant outlet along the direction of the air stream.

4. The energy exchanger of claim 1 , wherein the desiccant flows through the desiccant channels along a non-linear flow path between the inlet and outlet.

5. The energy exchanger of claim 1 , wherein the desiccant flows through the desiccant channels along a flow path, the flow path having a cross-flow segment and a counter-flow segment, the cross-flow segment extending in a flow direction substantially perpendicular to the flow direction of the air stream, the counter-flow segment extending in a direction approximately 180° from the flow direction of the air stream.

6. The energy exchanger of claim 1 , wherein the desiccant flows along a flow path in a flow direction that is at least partially counter-flow with respect to the flow direction of the air stream.

7. The energy exchanger of claim 1 , wherein a flow rate of the desiccant with respect to a flow rate of the air stream is controlled to achieve predetermined exchanger performance ratios that at least partially define a sensible and latent energy exchange between the desiccant and the air stream.

8. The energy exchanger of claim 1 , wherein the semi-permeable membrane is selected based on at least one of a water vapor transfer resistance ratio, a liquid break through pressure ratio, or an elastic tensile yield limit ratio of the membrane.

9. The energy exchanger of claim 1 , wherein the plurality of panels include support structures to limit deformation of the panel membrane.

10. The energy exchanger of claim 1 , wherein a characteristic Reynolds number for the air stream through the air channels is greater than a critical Reynolds number for turbulent flow in the air channels.

11. The energy exchanger of claim 1 , wherein the air channels include turbulence enhancing surface roughness features to facilitate increasing energy transfer that exceeds an additional air pressure drop energy loss when convective heat and latent energy transfer increase.

12. The energy exchanger of claim 1 , wherein a characteristic Rayleigh number for desiccant flow in the desiccant channels is less than a critical Rayleigh number for thermally induced liquid density instability causing non-uniform mal-distributed flow at a Reynolds number for desiccant flow.

13. The energy exchanger of claim 1 , wherein desiccant channels include turbulence enhancing surface roughness features when a Rayleigh number is less than a critical Rayleigh number at a Reynolds number for the flow.

14. The energy exchanger of claim 1 , wherein a thermal insulation surrounding the panels is such that a heat exchange rate between the panels is less than 5% of a heat rate between supply and exhaust air flow streams during a standard summer or winter test with AHRI 1060 air inlet operating conditions.

15. An energy exchanger comprising:
a housing;
a plurality of panels forming desiccant channels air channels separated by at least one semi-permeable membrane, the air channels configured to direct an air stream through the housing, the plurality of panels spaced apart based on predetermined air to desiccant mass flow rates that define an air channel width and a desiccant channel width;
a desiccant inlet in flow communication with the desiccant channels; and
a desiccant outlet in flow communication with the desiccant channels, the desiccant channels configured to channel desiccant from the desiccant inlet to the desiccant outlet in at least one of a counter-flow or cross-flow direction with respect to the direction of the air stream to facilitate heat and water vapor transfer between the desiccant in the desiccant channels and the air stream in the air channels, the air to desiccant mass flow rates selected to provide a predetermined mass or volume of air stream flowing through the air channels or a predetermined mass or volume of desiccant flowing through the desiccant channels.

16. The energy exchanger of claim 15 , wherein the desiccant channels have an approximately constant desiccant channel width through the housing and the air channels have an approximately constant air channel width through the housing.

17. The energy exchanger of claim 15 , wherein a ratio of the average air channel width divided by the average desiccant channel width is within a range of 1 to 5.

18. An energy exchanger comprising:
a housing;
a plurality of panels forming desiccant channels and air channels extending through the housing, the air channels configured to direct an air stream through the housing;
a desiccant inlet in flow communication with the desiccant channels;
a desiccant outlet in flow communication with the desiccant channels, the desiccant channels configured to channel desiccant from the desiccant inlet to the desiccant outlet in at least one of a counter-flow or cross-flow direction with respect to the direction of the air stream; and
a semi-permeable membrane extending through each panel to facilitate heat and water vapor transfer between the desiccant in the desiccant channels and the air stream in the air channels, the air stream and the desiccant causing the semi-permeable membrane to deflect during operation, the desiccant membrane selected based on predetermined channel deflection ranges that are defined to limit the amount of membrane deflection.

19. The energy exchanger of claim 18 , wherein a standard deviation of a hydraulic diameter of at least one of the air channels and desiccant channels divided by a mean value of a hydraulic diameter for one of the air channels or desiccant channels is within a range 0.0 to 0.2.

20. The energy exchanger of claim 18 further comprising:
an air channel support screen having a solid area that is a fraction of a total area of the ai

Assignees

• Erb Blake
• Besant Robert W
• Simonson Carey J
• Hemingson Howard
• Nortek Air Solutions Canada Inc
• Univ Saskatchewan

Inventors

• Erb Blake
• Besant Robert W
• Simonson Carey J
• Hemingson Howard

Classifications

• F24F2003/1435

  comprising semi-permeable membrane · CPC title

• F28D15/00

  Heat-exchange apparatus with the intermediate heat-transfer medium in closed tubes passing into or through the conduit walls {; Heat-exchange apparatus employing intermediate heat-transfer medium or bodies (F28D17/00, F28D19/00, F28D20/00 take precedence)} · CPC title

• F24F3/1417

  with liquid hygroscopic desiccants · CPC title

• F28D21/0015

  Heat and mass exchangers, e.g. with permeable walls · CPC title

• F24F12/006

  using an air-to-air heat exchanger (F24F12/002 takes precedence) · CPC title