Patent Application
20190049163
The present invention relates to evaporative refrigerant condenser coils.
A conventional evaporative refrigerant condenser is comprised of a fan system, water distribution system and heat exchanger. The heat exchanger is generally comprised of multiple circuits of tube. Individual circuits are formed into serpentines with a specified number of passes, typically by bending a continuous length of tube. Individual circuits are joined in parallel by common inlet and outlet manifolds.
The predominant methods of increasing heat rejection capacity for a given plan area are to increase the airflow rate over the heat exchanger by increasing the fan speed and power, and to increase the heat exchanger surface area by creating serpentines with more passes from longer lengths of tube.
Manufacturers of conventional evaporative refrigerant condensers have largely applied the aforementioned methods up to the practical physical limitations concerning power consumption, fan blade speed, and material cost and weight. In addition to the physical limitations mentioned above, there exist significantly diminishing returns on thermal performance and efficiency for conventional serpentine coil evaporative condensers. For example in a given plan area, a 350% increase in surface coupled with a 400% increase in fan power results in only 300% increase in heat rejection capability. Table 1 further illustrates the limitations and diminishing returns of increasing circuit length as a means of increasing heat transfer surface area and thermal performance. The capacities provided are normalized for plan area and fan power.
An analysis of the data used to create Table 1 indicates thermal capacity gains can be realized for a given heat exchanger when the circuiting is simply modified to create more parallel circuits of shorter length compared to a conventional serpentine coil. For all intents and purposes, the factors of tube geometry, tube spacing, external coil surface area, air flow rate, and spray flow rate would be unchanged between the conventional coil and the improvement described above.
A simplified version of this concept is shown on the right in
The improved circuiting concept, when applied to the fullest extent, can result in a heat exchanger consisting of entirely one-pass circuits as shown in
Increasing the number of circuits and reducing the circuit length has several benefits. First, it reduces the potential travel distance required for condensate to exit the coil. For example, refrigerant that condensed at the mid-point of the first pass must travel through the remaining passes in order to exit the coil, potentially occupying internal tube wall area that could otherwise be used for further condensing.
Second, the presence of additional circuits at the inlet of the heat exchanger will improve the distribution of vapor throughout the coil. This is clearly evident when comparing a conventional four-pass serpentine coil circuit to the equivalent coil with the proposed improvements in
The improved coil circuiting design will increase the available internal tube wall area available for condensation and decrease the pressure drop through the coil. The result is an increase in condensing capacity, a reduction in compressor power and an overall increase in system efficiency. These benefits may be most notable for high mass flow, low enthalpy refrigerants, which typically exhibit very high pressure drops in longer, narrower serpentine coils comprised of a small number of long, multi-pass circuits. Unit configurations and coil sizes applicable exclusively to low pressure drop refrigerants may now be expanded into new applications when the improved circuit design is implemented.
The circuiting improvements described above can be applied to all currently available evaporative refrigerant condensing equipment designs with minimal modifications to the existing structure, fan system or spray water distribution system, regardless of the tube geometry or the orientation of the heat exchanger with respect to the airflow and spray water flow direction.
This inventions relates particularly to condenser coil bundles used in evaporative refrigerant condensers 10 of the type shown in
The apparatus 10 includes a fan 100 for causing air to flow through the apparatus, and as shown schematically in
Prior art refrigerant coil assemblies 20 have a generally parallelepiped overall shape of six sides retained in a frame 21 and has a major/longitudinal axis 23, where each side is in the form of a rectangle. The coil assembly 20 may be made of multiple horizontal closely spaced parallel, serpentine tubes connected at their ends to form a number of circuits through which the refrigerant flows. Each individual circuit within the coil assembly may be a single, continuous length of coil tubing that is subjected to a bending operation which forms the tubing into several U-shaped rows that are in a generally vertical and equally-spaced relationship from each other, such that each circuit has a resultant serpentine shape. Finned tube coil assemblies are preferred.
The coil assembly 20 has an inlet 22 connected to an inlet manifold or header 24, which fluidly connects to inlet ends of the serpentine tubes of the coil assembly, and an outlet 26 connected to an outlet manifold or header 28, which fluidly connects to the outlet ends of the serpentine tubes of the coil assembly. The assembled coil assembly 20 may be moved and transported as a unitary structure such that it may be dipped, if desired, if its components are made of steel, in a zinc bath to galvanize the entire coil assembly.
The refrigerant gas discharges from the compressor into the inlet connection of the apparatus. Heat from the refrigerant dissipates through the coil tubes to the water cascading downward over the tubes. Simultaneously, air is drawn in through the air inlet louvers at the base of the condenser and travels upward over the coil opposite the water flow. A small portion of the water evaporates, removing heat from the system. The warm moist air is drawn to the top of the evaporative condenser by the fan and discharged to the atmosphere. The remaining water falls to the sump at the bottom of the condenser where it recirculates through the water distribution system and back down over the coils.
The invention constitutes a change and improvement over the prior art as illustrated in
Accordingly, where the tube bundle/coil assembly 20 of
The inlet for both tubes in each pair of nested tubes may be attached to the same inlet header. Alternatively, the outer tubes 104 of each nested pair of tubes may be connected to a first inlet header 105, and the inner tubes 106 of each nested pair of tubes may be connected to a second inlet header 106. Similarly, the outlet for both tubes in each pair of nested tubes may be attached to the same outlet header, or the outer tubes 104 of each nested pair of tubes may be connected to a first outlet header 108, and the inner tubes of each nested pair of tubes may be connected to a second outlet header 109.
Manufacturing of coil assemblies according to this embodiment of the invention has attendant material and labor cost increases, but the efficiencies achieved by such configuration over the life of the device are expected to far exceed the increased manufacturing cost.
According to an alternative embodiment, the coil assembly may be constructed entirely of one pass circuits as shown in
| Number | Date | Country | |
|---|---|---|---|
| 62456830 | Feb 2017 | US |
