Cooling tower with indirect heat exchanger
A heat exchange apparatus is provided with an indirect evaporative heat exchange section. The indirect evaporative heat exchange section includes a series of serpentine tubes, and an evaporative liquid is passed downwardly onto the indirect heat exchange section. The evaporative liquid is collected in a sump and then pumped upwardly to be distributed again across the indirect heat exchange section. An improved heat exchange apparatus is provided with a top and a bottom indirect evaporative heat exchange section including a series of serpentine tubes A secondary system to distribute evaporative liquid below the first indirect heat exchange section and a direct heat exchange section may be provided between the two indirect heat exchangers.
1. A method of exchanging heat comprising the steps of:
providing a first indirect evaporative heat exchange section, the first indirect heat exchange section conducting a fluid stream within a plurality of pathways,
the first indirect heat exchange section comprising a top and a bottom, providing a direct heat exchange section, the direct heat exchange section comprising a top and a bottom and a fill section, the direct heat exchange section being located under the first indirect heat exchange section,
and providing a second indirect evaporative heat exchange section,
the second indirect heat exchange section conducting a fluid stream within a plurality of pathways,
the second indirect heat exchange section comprising a top and a bottom, the second indirect heat exchange section being located under the direct heat exchange section,
distributing an evaporative liquid generally downward onto and through the first indirect heat exchange section such that indirect heat exchange occurs between the fluid stream within the plurality of pathways and the evaporative liquid,
moving air through the first indirect section,
the air moving through the first indirect heat exchange section exchanging heat with the evaporative liquid moving through the first indirect heat exchange section and hence indirectly exchanging heat with the fluid stream within the plurality of pathways in the first indirect section,
distributing the evaporative liquid generally downward onto and through the direct heat exchange section such that direct heat exchange occurs between the fluid stream and air moving through the direct section,
distributing the evaporative liquid generally downward onto and through the second indirect heat exchange section such that indirect heat exchange occurs between the fluid stream within the plurality of pathways and the evaporative liquid,
moving air through the second indirect section,
the air moving through the second indirect heat exchange section exchanging heat with the evaporative liquid moving through the second indirect heat exchange section and hence indirectly exchanging heat with the fluid stream within the plurality of pathways in the second indirect section,
wherein the first indirect heat exchange section is comprised of a first series of serpentine coils and the second indirect heat exchange section is comprised of a second series of serpentine coils, and wherein
a secondary system is provided to distribute the evaporative liquid downwardly and through the second indirect heat exchange section from a position above the top of the second indirect heat exchange section.
2. The method of exchanging heat of claim 1 , further comprising:
collecting substantially all of the evaporative liquid that exits the first indirect heat exchange section, the direct heat exchange section and the second indirect heat exchange section, and
pumping the collected evaporative liquid upwardly such that it can be distributed generally downward onto and through the first indirect heat exchange section, the direct heat exchange section and the second heat exchange section.
3. The method of exchanging heat of claim 1 wherein the air moving through the first indirect heat exchange section moves generally counter-current to the direction of flow of the evaporative liquid through the first indirect heat exchange section.
4. The method of exchanging heat of claim 1 wherein the air moving through the first indirect heat exchange section moves generally cross-current to the direction of flow of the evaporative liquid through the first indirect heat exchange section.
5. The method of exchanging heat of claim 1 , wherein the air moving through the direct section moves counter current to the generally downward evaporative liquid.