Patent Application
20240426556
The present invention relates to hybrid condensers and fluid coolers having both direct and indirect heat exchangers.
Hybrid cooling equipment with both direct and indirect heat exchangers can be designed in either a counterflow or crossflow arrangement. In a conventional crossflow arrangement, the indirect heat exchanger circuits are perpendicular to the air inlet of the direct heat exchanger as shown in expired U.S. Pat. No. 5,816,318. This arrangement creates a long, narrow circuit arrangement that results in a high fluid pressure drop across the heat exchanger. Traditional methods used to reduce the pressure drop focus on revised coil headering and return bends designs, as shown in U.S. Pat. No. 11,150,037 B2. This leads to large diameter headers that are complicated and costly to manufacture and can create compliance concerns with industry components such as ASME. Customary designs also necessitate intricate bending which requires specialized manufacturing equipment for these parts and reduces the overall capacity of the heat exchanger.
The design of the present invention features a novel arrangement for cooling towers having a center plenum with flanking concurrent flow indirect and cross-flow direct heat exchanges in which the tube coils of the concurrent flow indirect heat exchangers are arranged so that the tube lengths are parallel to the to the air inlet of the crossflow direct heat exchanger. The new design, which consists of elongated fluid headers combined with multiple shortened circuits, creates a compact design that results in a lower fluid pressure drop across the heat exchanger. The design of the present invention also creates an increased turbulence in relation to fluid flow, resulting in an increase in thermal performance.
Preferably, the combined length of the inlet headers of a particular indirect heat exchange section across the end face of a unit exceeds the circuit length (parallel to the side face) of the unit. According to various advantages of the invention, the increased number of circuits per header work to reduce the fluid pressure drop; the multiple short circuits create a more fully developed boundary layer in the tube, maximizing the internal heat transfer coefficient of each tube and resulting in an increased thermal performance of the design; the simplified compact design does not require specialized manufacturing equipment, and the tube circuiting arrangement does not require a header larger than 6″ in diameter which meets the requirements of ASME B31.5 for pressure vessels
In the drawings:
Elements shown in the drawings may be identified by the following numerical labels:
According to preferred embodiments of the invention, one or more top-mounted fans are situated above a central plenum, flanked by two indirect heat exchange sections, each situated above or below a direct heat exchange section, the direct heat exchange sections preferably containing water dispersion media (“fill”), with a water distribution system located above each indirect heat exchange section, and a basin at the bottom of each direct heat exchange section. The water basins may be joined in a single section with a single return to the water distribution systems, or the water basins may be separate, each with a separate return to the water distribution systems. Each indirect heat exchange section may include at least one, and preferably two or more coil bundles, each coil bundles having a respective set of input and output headers. The device does not require, has no, and explicitly excludes, any additional indirect heat exchanger(s) laterally adjacent the direct heat exchanger sections. The tubes in the indirect heat exchange section may be round or elliptical serpentine tubes and may optionally include fins, including plate fins, flat fins, or spiral fins. The device may be arranged so that the return bends of the tube bundle(s) are always facing the air inlet of the direct heat exchanger (whether situated above or below the indirect heat exchange section).
An exemplary embodiment will now be described with reference to the figures. A hybrid condenser/fluid cooler 1 according to the invention has a generally rectangular footprint having two side walls 3a, 3b and two end walls 5a, 5b, the side walls longer than the end walls, typically although not necessarily by around 50% or more. Two indirect heat exchange sections 7a, 7b are provided, each located adjacent a respective end wall 5a, 5b, extending generally the entire distance between the two side walls 3a, 3b. Two direct heat exchange sections 9a, 9b are also provided, each located adjacent a respective end wall 5a, 5b, extending generally the entire distance between the two side walls 3a, 3b. The direct heat exchange sections 9a, 9b may be located above or below their respective indirect heat exchange sections 7a, 7b. According to the most preferred arrangement, the direct heat exchange sections 9a, 9b are located below their respective indirect heat exchange sections 7a, 7b. The indirect heat exchange sections 7a, 7b include one or more tube coils 11, each tube coil including a plurality of serpentine tubes 13 connected at one end to an inlet header 15 and at another end to an outlet header 17. Between the inlet header 15 and outlet header 17, each length or segment of the serpentine tubes 13 is connected to adjacent lengths/segments of the same tube by a tube bend 19. Process fluid to be cooled enters the tubes via the inlet header(s) 15 and leaves the tubes via the outlet header(s) 17.
A central plenum 21 is centrally located in the unit between heat exchangers 7a and 9a on one side of the central plenum 21 and heat exchangers 7b and 9b on the other side of the central plenum 21. A fan 23 is located on top of the central plenum.
A water distribution system 25a and 25b is located above each respective indirect heat exchange section 7a and 7b. The water distribution system 25a and 25b may be any kind of known water distribution system, including perforated water troughs, an array of perforated water tubes, an array of water tubes fitted with nozzles, or any other combination of structures that are known, or which may be arranged, to deliver water over the area occupied by the indirect heat exchange section for evaporative cooling of the process fluid.
Two top air inlets 27a and 27b rest at the top of each side of the unit, adjacent opposite sides of the fan 23, above respective heat exchangers and water distribution systems.
Two side air inlets 29a and 29b are formed in respective end walls 5a and 5b, adjacent respective direct heat exchangers 9a and 9b. Direct heat exchanges 9a and 9b preferably contain water dispersion media 31a and 31b, respectively.
A bottom wall 33, together with the lowest portion of side walls 3a, 3b and end walls 5a and 5b form water collection basins 35a and 35b below heat exchangers 7a, 9a on one side of the unit and 7b, 9b, on the other side of the unit, respectively. One or more water pumps 37 are located in or adjacent the water collection basins 35a and 35b to return water collected in the water collection basins 35a and 35b to the water distribution systems 25a and 25b via return pipes 39.
Prior art devices of similar arrangements have indirect heat exchanger having have a single tube coil on each side of the central plenum, each tube coil featuring long tubes that extend the length of the end faces of the unit, with perpendicular inlet and outlet headers that extend the considerably shorter distance across a tube bend face of the coils, parallel to the side faces of the unit.
According to the present invention, however, the single tube coils with long tubes of the prior art are replaced with two, three or more tube coils 11 with shorter tubes, where the longitudinal axes of these shorter tubes are arranged parallel to the side walls 3a and 3b and perpendicular to the end walls 5a and 5b. According to this arrangement, the set of tube bends 19 at one end of the coil 11 are generally located above the respective side air inlets 29. The inlet headers 15 and outlet headers 17 are located adjacent and parallel to the end walls 5a and 5b. Contrary to prior art designs, the cumulative length of each set of inlet headers 15 and outlet headers 17 is longer the lengths of each tube in the tube coils. The unexpected result of this arrangement is increased heat capacity at lower pressure drop.
In operation, a hot process fluid enters the inlet headers 15, travels through the tube coils 11, exits the tube coils 11 via the outlet headers 17 and returns to the process. Fan 23 draws air in through both top air inlets 27a and 27b and both side air inlets 29a and 29b. A first air flow 41 enters the unit through top air inlets 27a and 27b, travels down through indirect heat exchanger sections 7a and 7b, into the plenum 21 through the bottom of indirect heat exchanger sections, up through the plenum 21 and out the top of the device through the fan 23. A second air flow 43, enters the unit through side air inlets 29a and 29b, travels across the direct heat exchange sections 9a and 9b into the central plenum, up through the central plenum 21 and out the top of the device through fan 23.
In warm or hot weather, the evaporative mode may be used wherein water distribution systems 25a and 25b distribute water over the indirect heat exchangers 7a and 7b, concurrent with the direction of the first air flow over the coils 11. The falling water, warmed by indirect contact with the process fluid passing through the tubes 13, enters the direct heat exchange sections 9a and 9b where it is cooled by the air passing in a cross-current direction through the direct heat exchange sections. The falling water collects in the basins 35a, 35b, where it is recirculated to the water distribution systems 25a and 25b via pumps 37 and return pipes 39.
In cold and especially in freezing temperatures, the water pumps 37 are turned off, the basins 35a and 35b preferably drained, and the unit is run in dry mode, with cooling of the process fluid occurring exclusively via the first air flow 41 passing downward over the coils 11.
It will be appreciated by those skilled in the art that changes could be made to the preferred embodiments described above without departing from the inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as outlined in the present disclosure and defined according to the broadest reasonable reading of the claims that follow, read in light of the present specification.
| Number | Date | Country | |
|---|---|---|---|
| 63509524 | Jun 2023 | US | |
| 63509758 | Jun 2023 | US |
