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Heat is indirectly transferred between a process fluid and ambient air in apparatus that includes an evaporative heat transfer cell operative in a wet mode or a dry mode, a dry heat transfer cell and a fan. The air may bypass the dry heat transfer cell to flow through a first air passage or may flow

Heat is indirectly transferred between a process fluid and ambient air in apparatus that includes an evaporative heat transfer cell operative in a wet mode or a dry mode, a dry heat transfer cell and a fan. The air may bypass the dry heat transfer cell to flow through a first air passage or may flow through a second air passage through the dry heat transfer cell and in either event, then through the evaporative heat transfer cell. The air may partially flow through and partially bypass the dry heat transfer cell, and then through the evaporative heat transfer cell. The evaporative heat transfer cell optionally may include a direct contact evaporative heat exchanger.

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1. A hybrid heat exchange apparatus for indirectly transferring heat between a process fluid and ambient air, the apparatus comprising an evaporative heat transfer cell operative in a wet or dry mode; an indirect dry heat transfer cell that is only operable in a dry manner and is located upstream in

1. A hybrid heat exchange apparatus for indirectly transferring heat between a process fluid and ambient air, the apparatus comprising an evaporative heat transfer cell operative in a wet or dry mode; an indirect dry heat transfer cell that is only operable in a dry manner and is located upstream in an air flow when air flows through the indirect dry heat transfer cell and the evaporative heat transfer cell; and a fan for causing air to flow from the ambient atmosphere through the apparatus; the apparatus being manually or automatically controllable for turning on or off a distributor assembly of cooling liquid in the evaporative heat transfer cell and for controlling air flow through a first air passage to bypass the dry heat transfer cell to flow through the evaporative heat transfer cell, or through a second air passage through the dry heat transfer cell and then through the evaporative heat transfer cell, or to partially bypass the dry heat transfer cell through the first air passage and partially flow through the second air passage, any air flowing through the first or second air passage then flowing through the evaporative heat transfer cell, the dry heat transfer cell being upstream of the evaporative heat transfer cell; the evaporative heat transfer cell comprising an indirect evaporative heat transfer cell with a first process fluid coil assembly through which the process fluid flows internally within the first process fluid coil assembly and which air must flow externally through in all modes and including a first process fluid inlet header and a first process fluid outlet header; the distributor assembly for selectively distributing cooling liquid from a source externally over the first process fluid coil assembly; and the fan for moving air externally through the first process fluid coil assembly and the apparatus;the dry heat transfer cell comprising a second process fluid coil assembly through which the process fluid may selectively flow internally within the second process fluid coil assembly and air may selectively flow externally through the second process fluid coil assembly, the second process fluid assembly including a second process fluid inlet header and a second process fluid outlet header;the apparatus being operable in first, second, third and fourth modes;wherein in the first mode, selectively openable and closeable air inlet dampers are open, such that the ambient air bypasses the dry heat transfer cell and flows directly through the evaporative heat transfer cell with the distributor assembly of cooling liquid turned on;wherein in the second mode, the air inlet dampers are closed, such that the ambient air flows first through the dry heat transfer cell and then directly through the evaporative heat transfer cell with the distributor assembly of cooling liquid turned off;wherein in the third mode, the air inlet dampers are closed, such that the ambient air flows first through the dry heat transfer cell, increasing the temperature of the ambient air to provide heated air, and then directly through the evaporative heat transfer cell with the distributor assembly of cooling liquid turned on; andwherein in the fourth mode, the air inlet dampers are partially open, such that first, some of the ambient air passes through the dry heat transfer cell and some of the ambient air bypasses the dry heat transfer cell, and such that the ambient air passing through the dry heat transfer cell, when mixed with the ambient air bypassing the dry heat transfer cell, increases the temperature of the mixed ambient air to provide heated mixed ambient air, and the heated mixed ambient air then directly flows through the evaporative heat transfer cell with the distributor assembly of cooling liquid turned on. 2. The hybrid heat exchange apparatus of claim 1, further comprising a plurality of evaporative heat exchange cells. 3. The hybrid heat exchange apparatus of claim 1, further comprising a plurality of dry heat exchange cells. 4. The hybrid heat exchange apparatus of claim 1, further comprising a plurality of dry heat exchange cells and a plurality of evaporative heat exchange cells. 5. The hybrid heat exchange apparatus of claim 1, wherein the dry heat transfer cell and the evaporative heat transfer cell are within a housing. 6. The hybrid heat exchange apparatus of claim 5, wherein the housing comprises a housing of the evaporative heat transfer cell in fluid communication within a housing of a plenum chamber for the first and second air passages where the fluid communication is substantially airtight except for air flow inlets and air flow outlets. 7. The hybrid heat exchange apparatus of claim 5, wherein the dry heat transfer cell is mounted within a top portion of a housing for a plenum chamber that comprises front and rear walls, top and bottom walls, a side wall and an open side opposite the side wall, the second process fluid coil assembly of the dry heat transfer cell being located below the top wall, wherein the top wall has openings for an inlet to the second air passage for air to flow through the openings and externally through the second process fluid coil assembly the side wall contain ng the openable and closeable air inlet dampers for controlling the air flow through the first air passage which bypasses the second process fluid coil assembly; and wherein the evaporative heat transfer cell is mounted in a housing having an upper portion and a lower portion the first process fluid coil assembly being located in the upper portion, the evaporative heat transfer cell housing comprising front and rear walls, opposed side walls and top and bottom walls, the top wall of the evaporative heat transfer cell housing including an air outlet above the first process fluid coil assembly, one of the side walls having an opening in the lower portion in fluid communication with the first and second air passages through the open side of the plenum chamber housing, the front and rear walls of the plenum chamber housing being coextensive with the front and rear walls, respectively, of the evaporative heat transfer cell housing; whereby when the air inlet dampers are closed, air flows through the top openings of the plenum chamber housing the dry heat transfer cell, through the inlet for the second air passage, through the second process fluid coil assembly, through the open side of the plenum chamber housing, through the opening in the side wall lower portion of the evaporative heat transfer cell housing, through the first process fluid coil assembly and out the outlet of the evaporative heat transfer cell housing; andwhereby when the air inlet dampers are open, air flows through the air inlet dampers for the first air passage, bypassing the second process fluid coil assembly, through the open side of the plenum chamber housing, through the opening in the side wall lower portion of the evaporative heat transfer cell housing, through the first process fluid coil assembly and out the outlet of the evaporative heat transfer cell housing. 8. The heat exchange apparatus of claim 7, wherein the fan for the apparatus is an induced draft air fan located upstream of the air outlet and downstream of the first process fluid coil assembly in the evaporative heat transfer, cell to induce air flow through at least one of the first and second air passages of the plenum chamber, into the evaporative heat transfer cell, through the first process fluid coil assembly and out the air outlet. 9. The hybrid heat exchange apparatus of claim 1, wherein the second process fluid coil assembly of the dry heat transfer cell 1 comprises a finned tube coil assembly. 10. The hybrid heat exchange apparatus of claim 1, wherein the evaporative heat transfer cell further comprises: an air outlet downstream of the first process fluid coil assembly;the fan for the apparatus in the form of an induced draft air fan located upstream of the air outlet to induce air flow through at least one of the first and second air passages;drift eliminators located between the first process fluid coil assembly and the fan to reduce mist of the cooling liquid from flowing through the air outlet;a sump to contain the cooling liquid;a conduit connecting the sump to the distributor assembly, anda pump to pump the cooling liquid from the sump to the distributor assembly through the conduit connecting the sump to the distributor assembly. 11. The hybrid heat exchange apparatus of claim 10, wherein the evaporative heat transfer cell further comprises direct contact heat transfer media for intermixing the cooling liquid and the air flowing through the evaporative heat transfer cell, the heat transfer media being located below the distributor assembly and above or below the first process fluid coil assembly. 12. The hybrid heat exchange apparatus of claim 1, wherein the fan is located downstream of the air inlet dampers and the second process fluid coil assembly and upstream of the first process fluid coil assembly, whereby the air is drawn through the air inlet dampers when the air inlet dampers are open and through the second process fluid coil assembly when the air inlet dampers are closed, and whereby the air is thereafter forced through the first process fluid coil assembly. 13. The hybrid heat exchange apparatus of claim 1, operating as a condenser of the process fluid, wherein the process fluid is separated to flow in parallel through the first process fluid coil assembly of the evaporative heat transfer cell and through the second process fluid coil assembly of the dry heat transfer cell. 14. The hybrid heat exchange apparatus of claim 1, operating as a cooler of the process fluid, wherein the process fluid is separated to flow in parallel through the first process fluid coil assembly of the evaporative heat transfer cell and through the second process fluid coil assembly of the dry heat transfer cell. 15. The hybrid heat exchange apparatus of claim 1, operating as a cooler of the process fluid, wherein the process fluid flows first through the second process fluid coi assembly of the dry heat transfer cell and then through the first process fluid coil assembly of the evaporative heat transfer cell. 16. The hybrid heat exchange apparatus of claim 1, wherein the first process fluid coil assembly comprises a plurality of tubes, where the tubes have at least one generally straight section with a generally elliptical cross-sectional shape and with an outer surface, wherein fins are located on the outer surface of the generally straight section of at least some of the tubes. 17. The hybrid heat exchange apparatus of claim 16, wherein the generally straight section of the tubes has a longitudinal axis and a nominal tube outside diameter, wherein the fins have a spacing of 1.5 to 3.5 fins per inch (2.54 cm) along the longitudinal axis of the straight section of the tubes, the fins having a height extending from the outer surface of the straight section of the tubes a distance of substantially 23.8% to substantially 36% of the nominal tube outside diameter, the fins having a thickness of substantially 0.007 inch (0.018 cm) to substantially 0.020 inch (0.051 cm), the tubes having a center-to-center spacing generally horizontally and generally normal to the longitudinal axis of the straight section of the tubes of substantially 100% to substantially 131% of the nominal tube outside diameter, and the horizontally adjacent straight section of the tubes having a generally vertical center-to-center spacing of substantially 110% to substantially 300% of the nominal tube outside diameter. 18. The hybrid heat exchange apparatus of claim 16, wherein the plurality of tubes are serpentine tubes wherein, except for the inlet and outlet ends, the straight sections are connected to each other by return bends, and wherein fins are located on the outer surface of the generally straight sections of at least a majority of the tubes. 19. The hybrid heat exchange apparatus of claim 18, wherein the generally straight sections of the tubes have a longitudinal axis and a nominal tube outside diameter, wherein the fins have a spacing of 1.5 to 3.5 fins per inch (2.54 cm) along the longitudinal axis of the straight sections of the tubes, the fins having a height extending from the outer surface of the straight sections of the tubes a distance of substantially 23.8% to substantially 36% of the nominal tube outside diameter, the fins having a thickness of substantially 0.007 inch (0.018 cm) to substantially 0.020 inch (0.051 cm), the tubes having a center-to-center spacing generally horizontally and generally normal to the longitudinal axis of the straight sections of the tubes of substantially 100% to substantially 131% of the nominal tube outside diameter, and the horizontally adjacent straight sections of the tubes having a generally vertical center-to-center spacing of substantially 110% to substantially 300% of the nominal tube outside diameter.