CLOSED CIRCUIT HEAT EXCHANGE SYSTEM AND METHOD WITH REDUCED WATER CONSUMPTION

摘要

A system and methods of extracting heat are disclosed. The system may be arranged as a fluid cooler or as a fluid condenser. Three heat exchange sections are provided: a dry indirect contact heat exchange section; a second indirect contact heat exchange secti on that is operable in either a wet or dry mode; and a direct contact heat exchange section. As a fluid cooler, a connecting flow path connects the dry indirect contact heat exchange section to the second indirect contact heat exchange section. A bypass flow path extends from the dry indirect contact heat exchange section to the process fluid outlet. A modulating valve is at the outlet so that process fluid can be selectively drawn from the dry indirect contact heat exchange section alone, from the second indirect contact heat exchange section in series with the dry indirec t contact heat exchange section, or from both the dry and second indirect contact heat exchange sections and mixed. Separate air streams pass through the second indirect and direct contact hea t exchange sections before entering the dry indirect contact heat exchange section. As a condenser, process fluid is directed to the dry indirect contact heat exchange section alone or to the d ry and second indirect contact heat exchange sections in parallel by valves in the process fluid supply lines. In another embodiment, the process fluid flows in series from the dry to the second indirect contact heat exchange section. The system is operable in different modes to extract heat from the process fluid in the most efficient way with respect to annual water consumption. At low temperatures, the system operates dry with primary heat extraction performed by the dry indirect contact heat exchange section. At higher temperatures, the air streams may be adiabatical ly saturated with evaporative liquid to pre-cool them below the dry bulb temperature before entering the dry indirect contact heat exchange section. At still higher temperatures, the apparatus may be operated in a wet mode with the primary heat extraction performed by the second indirect contact heat exchange section. Heat is extracted from the process fluid while selectively distributing or not distributing the evaporative liquid over the second indirect contact hea t exchange section. Plume formation is prevented since discharge air is heated in contact with t he dry indirect contact heat exchange section before leaving the heat exchange apparatus.