Heat transfer tube for heat exchanger

1. A heat exchanger for a heating ventilation, air conditioning and refrigeration (HVAC/R) system comprising:

a heat exchanger housing; and

a plurality of heat exchanger tubes extending through the heat exchanger housing, the plurality of heat exchanger tubes conveying a first fluid therethrough for thermal energy exchange with a second fluid outside of the plurality of heat exchanger tubes, each heat exchanger tube of the plurality of heat exchanger tubes including:

a tube inner surface; and

a tube outer surface radially offset from the tube inner surface, the tube outer surface including patterned porosity with a plurality of high porosity regions of the tube outer surface having relatively high porosity to promote flow of the second fluid radially inwardly via capillary flow, and a plurality of low porosity regions of the tube outer surface having relatively low porosity to facilitate vapor departure from the tube outer surface;

wherein the plurality of high porosity regions and the plurality of low porosity regions are arranged about a circumference of the tube outer surface in a circumferentially alternating arrangement of a high porosity region of the plurality of high porosity regions and a low porosity region of the plurality of low porosity regions; and

wherein the plurality of high porosity regions and the plurality of low porosity regions alternate radially in a circumferential direction about the tube;

wherein the plurality of high porosity regions and the plurality of low porosity regions are arranged in a plurality of rows along a tube axis, and

wherein each high porosity region of the plurality of high porosity regions has a circumferential center, and

wherein a circumferential center of each high porosity region of the plurality of high porosity regions in a first row of the plurality of rows is located angularly offset relative to the tube axis from a circumferential center of each high porosity region of the plurality of high porosity regions of an axially adjacent second row of the plurality of rows.

2. The heat exchanger of claim 1 , wherein the low porosity regions are defined by spaces between adjacent high porosity regions of the plurality of high porosity regions.

3. The heat exchanger of claim 1 , wherein a high porosity region of the plurality of high porosity regions has a triangular cross-sectional shape.

4. The heat exchanger of claim 1 , wherein a ratio of an axial length of a high porosity region of the plurality of high porosity regions along a tube axis to a radial height of the high porosity region of the plurality of high porosity regions is between about 0.1 and 10.0.

5. The heat exchanger of claim 1 , further comprising a cylindrical porous cover layer disposed radially outboard of the tube outer surface and over the plurality of high porosity regions and the plurality of low porosity regions, the porous cover layer extending circumferentially around the tube.

6. The heat exchanger of claim 5 , wherein the porous cover layer comprises a plurality of cover layer segments with an axial cover layer gap between axially adjacent cover layer segments of the plurality of cover layer segments.

7. The heat exchanger of claim 1 , wherein the plurality of high porosity regions are formed from a plurality of microspheres.