Patent Description:
Condensers are used in power plants to condense the motive fluid exhausted from turbines. They are also used in refrigeration plants to condense refrigeration vapors such as ammonia or fluoridate hydrocarbons, and in the petroleum and chemical industries such as for use in a fuel distillation apparatus to condense a variety of chemical vapors.

Air-cooled condensers (ACCs) are used in those geographical regions where cooling water for reducing the temperature of heat depleted vapor is scarce. <CIT>, <CIT>, <CIT>, <CIT> and <CIT> describe ACCs in the form of a cooling tower.

In some types of ACCs, heat is rejected from the hot fluid that flows through the tubes to the ambient air by passive or forced air flow, generally in counterflow by means of a fan, on the external side of the heat exchanger tubes. Axial fans often having a diameter of greater than <NUM> ft, e.g. <NUM><NUM> ft are often installed above the ACC tube bundles to induce air across the bundles. In addition to the plentiful nature of air serving as the condensing medium, an additional advantage of an ACC is that air will not freeze as opposed to water. The inherently low heat transfer coefficient is compensated for by high fin areas.

The thermal performance of ACCs during windy periods, however, is reduced due to cross winds, as a result of a decreased flow of air through the fans, causing in turn a decreased cooling capacity. In addition, ACC performance can also be degraded due to the recirculation of warm outlet air that is mixed with ambient air, resulting in increased air inlet temperature and in increased turbine back pressure.

One prior art method to reduce the influence of cross winds and of air recirculation involves the use of porous wind screens. These wind screens are expensive to manufacture and install, and usually involve a reduction in static pressure underneath the ACC structure.

Another method involves positioning the ACC so that the long edge of the ACC structure is parallel to the prevailing wind direction. However, such ACC positioning is often infeasible due to topographical constraints.

<CIT>, <CIT> and <CIT>, disclose wind guiding vanes or deflectors that are mounted for rotation about a vertical axis, so that their pivot angle or height is changeable in response to sensor readings. The need for controlling displacement of the wind guiding vanes or deflectors unduly adds costs to the system.

It is an object of the present invention to provide stationary wind guiding vane apparatus for increasing the thermal performance of ACCs during windy periods.

The present invention provides wind guiding vane apparatus for mitigating a detrimental influence of cross winds flowing in the vicinity of an air-cooled condenser (ACC) and through one or more fans, positioned in lateral direction of the ACC, to which ambient air is directed and discharged to the atmosphere after cooling condenser tubes of said ACC, comprising one or more stationary wind guiding vanes positioned along at least a portion of an air flow streamline and below a plurality of condenser tubes of said ACC, wherein said one or more wind guiding vanes are configured to redirect air flow during windy conditions towards a portion of said plurality of condenser tubes and at least one of said fans at such an angle that significantly deviates from perpendicular, fairly horizontal inflow.

The one or more wind guiding vanes are also suitable to maintain a nominal flow rate of air during quiescent wind conditions.

Some geothermal resources and fluids desired to be exploited have such a low energy content, for example extracted at a temperature of <NUM>-<NUM> (<NUM>-<NUM>°F) that a power plant utilizing a motive fluid, to which heat is transferred from the geothermal resource, is economically viable particularly when the turbine discharge is condensed by an air-cooled condenser (ACC). As described above, the thermal efficiency of an ACC is dependent upon the performance of the ACC fans through which ambient air is directed and discharged to the atmosphere, after cooling the motive fluid present in the condenser tubes. During windy conditions, however, according to one explanation, perpendicular inflow to the ACC causes the dynamic pressure below the ACC to increase, and the static pressure which is reflective of resistance to airflow decreases. The differential static pressure between the inlet and outlet of the ACC fans increases, and the mean velocity of air exiting the ACC fans is consequently caused to decrease, and at times can even decrease to stalled conditions, resulting in a decreased cooling capacity and a reduced effective heat exchange area used due to a reduced flow rate of air across the condenser tubes. Under such conditions, the ACC fans find it difficult to perform at nominal conditions and their air intake drops. As a consequence of this, the air velocity under the upstream portion of the ACC structure is low so that the performance, i.e. the outlet air flow rate of the upstream fan, as well as, to some extent, the second upstream fan, is reduced. Use of the wind guiding vanes, described herein, positioned, in accordance with the present invention, beneath the ACC structure and advantageously, under the first upstream fan, causes a lesser reduction in the performance of the first two upstream fans. The economic viability of an ACC-based power plant is therefore dependent upon the reliable reduction of the influence of cross winds or winds having a component in the cross wind direction, so that cooling air will reliably flow across the condenser tubes prior to being discharged through an ACC fan even during windy conditions.

The apparatus of the present invention is advantageously able to mitigate the detrimental influence of cross winds by carefully positioning one or more stationary wind guiding vanes along at least a portion of au air flow streamline, below the ACC structure. The windy air flow, after contacting the wind guiding vanes, is redirected towards the condenser tubes and fans at such an angle that significantly deviates from the perpendicular, fairly horizontal inflow. The wind guiding vanes are also suitable to maintain a nominal flow rate during quiescent wind conditions.

The actual location of the wind guiding vanes along the streamlines, as well as their size and orientation, have been determined with use of computational fluid dynamics (CFD) analysis, based on a numerical Navier-Stokes equation solution to model the general air flow in and around the ACC structure, together with shear stress transport (SST) turbulence model to evaluate the turbulent flow in the boundary layer of air within the ACC structure, near the wind guiding vanes, finned tubes and ACC fans.

Reference is first made to <FIG>, which schematically illustrates an ACC designated ACC <NUM>. typically located outdoors. ACC <NUM> comprises condenser tube section <NUM>, each of which may be finned, and a plurality of fans <NUM>. Usually three fans are used, while sometimes two or even more fans, located in the lateral or width direction W of ACC <NUM>, can be used. The spaced tubes through which motive fluid to be condensed flows are arranged so that cooling air can flow over the tubes and dissipate the thermal energy of the motive fluid flowing therein. ACC <NUM> is arranged as a rectangular array with a length L, width W and height H. ACC <NUM> is installed above the level of ground at a distance PH from the ground to allow free flow of air underneath the ACC. In order to increase the rate of heat dissipation, fans <NUM> are installed above tube section <NUM> to induce the flow of air from the area beneath ACC <NUM> up through tube section <NUM>. In addition, such an arrangement reduces to a large extent the possible recirculation of air exiting the fans being drawn into the inlet flow of air under ACC <NUM>.

The efficiency of heat dissipation of ACC <NUM> depends on various ambient conditions, such as the amount of exposure to direct sun light, the ambient temperature and the actual wind conditions (direction and magnitude) at the given location of ACC <NUM>. For large ACCs with a high aspect ratio (L/W) figure, wind blowing parallel to its length dimension has a negligible effect. In contrast, wind blowing parallel to its width dimension has a substantial effect due to the perpendicular inflow.

<FIG> illustrates wind guiding vane apparatus <NUM>, according to one embodiment of the present invention. Wind guiding vane apparatus <NUM> comprises two vertically spaced, elongated and stationary wind guiding vanes <NUM> and <NUM> that are fixed in place below one widthwise and <NUM> of the schematically illustrated ACC <NUM>, i.e. the condenser tube section for condensing the motive fluid, such as organic motive fluid, present in the finned tubes. The wind guiding vanes are preferably straight to reduce their cost by virtue of the relative ease in manufacturing, but curved wind guiding vanes are also in the scope of the invention. wind guiding vanes <NUM> and <NUM> are generally inclined with respect to horizontal support elements <NUM> in the vicinity of widthwise end <NUM>, such that the downstream edge <NUM> of each wind
guiding vane is located at a greater height than the corresponding upstream edge <NUM> thereof, to ensure that wind-derived air flow will be redirected thereby towards the condenser tubes and fans at an angle that significantly deviates from perpendicular, fairly horizontal inflow. The wind guiding vanes are sufficiently sturdy to withstand the relatively high forces associated with the kinetic energy in high-velocity wind, and are made for example from stainless steel to resist corrosion when exposed to precipitation.

The upstream edge <NUM> of upper wind guiding vane <NUM> may be connected to three spaced columns 15A-15C, spaced in the longitudinal direction, adapted to support the underside of ACC <NUM>. The downstream edge <NUM> of upper wind guiding vane <NUM> may be connected to braced wind guiding vane support structure 27A-27C. The downstream edge <NUM> of lower wind guiding vane <NUM> may be connected to each brace 18A-18C extending upwardly from the bottom of a corresponding column 15A-16C to a top region of a corresponding intermediate column 27A-27C. The upstream edge <NUM> of lower wind guiding vane <NUM> may be connected to an additional support structure, for example one connected to upper wind guiding vane <NUM>.

In this fashion, the support structures sufficiently immobilize wind guiding vanes <NUM> and <NUM> without appreciably interfering with the wind-derived air flow in the vicinity of the wind guiding vanes.

Although ACC <NUM> is shown to be configured as a rectangular array, it will be appreciated that the ACC may be configured in other ways as well.

<FIG> and <FIG> schematically illustrate the utility of the wind guiding vanes to adequately direct an air flow to the condenser tubes and to the ACC fans during both quiescent conditions and windy conditions. As referred to herein, windy conditions are considered to be those environmental conditions that induce the speed of winds to be greater than <NUM> mis, for example between <NUM>-<NUM> mls. Such windy conditions may occur on a seasonal basis, such as during continued periods in the summer season, or even during a shortened period, such as one hour or a period of six hours. Even so, the wind guiding vanes described herein also bring about an improvement of performance of the first two fans even when winds of about <NUM>/s prevail.

The vertical cross section of wind guiding vane apparatus <NUM> illustrates a unit of three laterally or width spaced fans 26A-C, each of which surrounded by a corresponding shroud 27A-27C. Fans 26A-C, usually of the axial type but which may be configured in other ways as well, are supported by fan deck <NUM> located above ACC <NUM>, so as to be in fluid communication with a corresponding region of ACC <NUM> in order to induce the flow of air across the condenser tubes. Alternatively, a forced-draft arrangement can also be used.

Vertically spaced wind guiding vanes <NUM> and <NUM> are positioned below ACC <NUM>, and are inclined with respect to, and located above, underlying ground surface <NUM>. The inclination of wind guiding vanes <NUM> and <NUM> is arranged such that their downstream edge <NUM> is inclined upwards towards the direction of second lateral end <NUM> of ACC <NUM> and away from first widthwise and <NUM> thereof. Wind guiding vanes <NUM> and <NUM> may be connected to a support structure as illustrated in <FIG>, or may be connected in other ways to wind guiding vane apparatus <NUM>. Wind guiding vanes <NUM> and <NUM> may be positioned directly below the first upstream fan 26A, to achieve more direct control of the wind-derived air flow towards the condenser tubes and ACC fans.

Apparatus <NUM> is shown to include in one embodiment a diffuser <NUM> for receiving organic motive fluid vapor from the outlet of an organic vapor turbine and supplying it to the internal volume of the condenser tubes of ACC <NUM>. Apparatus <NUM> also comprises collector <NUM> for collecting liquid organic motive fluid condensate produced by ACC <NUM>, to supply the same by a steady and continuous flow to the inlet of the cycle pump.

<FIG> illustrates the air flow during quiescent conditions to fans 26A-26C, and <FIG> illustrates the air flow during windy conditions. Fans 26A-26B are considered as upstream fans as their operation is affected by the wind guiding vane-influenced, wind-derived air flow, while fan 26C is considered as a downstream fan as its operation is to a large extent unaffected by the wind guiding vane-influenced, wind-derived air flow.

It will be appreciated that wind guiding vane apparatus <NUM> may comprise additional fans, longitudinally and/or laterally or width spaced from the fan unit of fans 26A-26C, e.g. <NUM> laterally adjacent ACC structures, and in fluid communication with a corresponding region of ACC <NUM>, whether by repeating the sequence of fans 26A-26C or by providing any other desired sequence, depending on the amount of heat to be dissipated. The number of fan units, present in the longitudinal direction L of ACC <NUM> (see <FIG>), may vary from e.g. <NUM>-<NUM> to <NUM>-<NUM>, depending also on the type of motive fluid used.

As shown in <FIG>, air flow <NUM> during quiescent wind conditions is equally drawn into each of the fans 26A-26C, and from all directions. Wind guiding vanes <NUM> and <NUM> do not disturb air flow <NUM> as far as operation of ACC <NUM> is concerned, while flowing across the condenser tubes towards fans 26A-26C, because the wind guiding vanes are positioned on the streamlines of air flow <NUM>. Consequently, the nominal power of the fans is maintained under quiescent conditions even with the presence of wind guiding vanes <NUM> and <NUM>.

As shown in <FIG>, wind guiding vanes <NUM> and <NUM> remain physically located below the first upstream fan 26A, being in the same position during windy conditions as during quiescent wind conditions. Although wind guiding vanes <NUM> and <NUM> do not disturb the air flow during quiescent wind conditions, they cause redirection of the air flow during windy conditions when the wind-derived air flow <NUM> blows in the direction shown in <FIG>. Following interaction with wind guiding vanes <NUM> and <NUM>, the direction of wind-derived air flow <NUM> is caused to change, being directed to a specific region of condenser tubes and to a specific fan, at an angle that significantly deviates from virtually horizontal inflow. Upper wind guiding vane <NUM> is configured to direct the air flow to the first upstream fan 26A, while lower wind guiding vane <NUM> influences to a greater extent the air flow to the second upstream fan 26B.

The deflection of air flow <NUM> provided by each of wind guiding vanes <NUM> and <NUM> is a function of the wind guiding vane inclination relative to underlying ground surface <NUM>, the horizontal and vertical distance to an outer edge of the portion of the condenser tubes to be cooled by the redirected air flow, and the length and width of the wind guiding vane.

As to downstream fan <NUM>, its operation has been found to be virtually unaffected by the residual air flow flowing downstream to wind guiding vanes <NUM> and <NUM>, insignificant disturbance apparently remaining in this residual air flow following the influence of wind guiding vanes <NUM> and <NUM>. Consequently, a third wind guiding vane to redirect the air flow to downstream fan 26C is unnecessary. Thus, apparatus <NUM> achieves a cost-effective solution since only two wind guiding vanes are needed for a unit of three fans, although three, or any other number of wind guiding vanes, may also be employed.

<FIG> illustrates wind guiding vane apparatus <NUM> for use in conjunction with environmental conditions that are characteristic of wind direction shifts, which can sometimes be sudden, such as winds that change direction with respect to a median direction to produce air flow <NUM> oppositely directed to air flow <NUM>.

Apparatus <NUM> is identical to apparatus <NUM> of <FIG>, but with the addition of wind guiding vanes <NUM> and <NUM> positioned directly beneath fan 26C. wind guiding vanes <NUM> and <NUM> may be connected to a support structure as illustrated in <FIG>, or may be connected in other ways to wind guiding vane apparatus <NUM>. The inclination of wind guiding vanes <NUM> and <NUM> is arranged such that their downstream edge <NUM> is pointing in the direction of first longitudinal end <NUM> ofACC <NUM> and away from second widthwise end <NUM> thereof. In this fashion, apparatus <NUM> is capable of suitably redirecting air flow <NUM> toward fans 26A-26B, and, following a wind shift, of suitably redirecting air flow <NUM> toward fans 26B-26C, to further increase the thermal performance of a power plant provided with apparatus <NUM>.

<FIG> illustrates the positioning of curved wind guiding vanes <NUM>-<NUM> that are used to redirect the air flow <NUM> during windy conditions towards fan shrouds 27A and 27B of wind guiding vane apparatus <NUM>, which are mounted above ACC <NUM> to produce an induced flow. Each of wind guiding vanes <NUM>-<NUM> is mounted one below the other, below first widthwise end <NUM> of ACC <NUM>, such that the projected horizontal dimension b and the distance c from the wind guiding vane to the bottom plane of AA <NUM> of each wind guiding vane progressively increases from the uppermost wind guiding vane <NUM> to the lowermost wind guiding vane <NUM>. Dimension a is the projected vertical dimension of each wind guiding vane, dimension d is the horizontal distance of the wind guiding vane from the upstream edge of ACC <NUM>, and R refers to the radius of each wind guiding vane.

Each of wind guiding vanes <NUM>-<NUM> is shown to coincide with a different streamline <NUM> that is produced as a result of the interaction of air flow <NUM> with a corresponding wind guiding vane. Wind guiding vanes <NUM>-<NUM> redirect air flow <NUM> towards the fan mounted within shroud 27A, and wind guiding vanes <NUM>-<NUM> redirect air flow <NUM> towards the fan mounted within shroud 27B.

<FIG> illustrates the positioning of curved wind guiding vanes <NUM>-<NUM> that are used to redirect the air flow <NUM> during windy conditions towards fan shrouds 67A and 67B of wind guiding vane apparatus <NUM>, which are mounted below ACC <NUM> to produce a forced flow. Each of wind guiding vanes <NUM>-<NUM> is mounted one below the other, below first widthwise end <NUM> of ACC <NUM>, such that the projected horizontal dimension b and the distance c from the wind guiding vane to the bottom piano of AA <NUM> of each wind guiding vane progressively increases from the uppermost wind guiding vane <NUM> to the lowermost wind guiding vane <NUM>. Dimension a is the projected vertical dimension of each wind guiding vane, dimension d is the horizontal distance of the wind guiding vane from the upstream edge of ACC <NUM>, and R refers to the radius of each wind guiding vane.

Each of wind guiding vanes <NUM>-<NUM> is shown to coincide with a different streamline <NUM> that is produced as a result of the interaction of air flow <NUM> with a corresponding wind guiding vane. Wind guiding vanes <NUM>-<NUM> redirect air flow <NUM> towards the fan mounted within shroud 67A, and wind guiding vanes <NUM>-<NUM> redirect air flow <NUM> towards the fan mounted within shroud 67B.

A determination of the streamlines along at least a portion of which the wind guiding vanes of the present invention are positioned was based on a numerical CFD analysis together with SST turbulence model, inputting the wind conditions measured at the Don Campbell geothermal power plant located in.

Nevada, USA. A <NUM>-million mesh was used to cover the ACC structure and its adjacent air flow. The size, number and location of the wind guiding vanes were designed by use of the CFD analysis, physically tested at the Don Campbell geothermal power plant, and reconfirmed by use of the CFD analysis.

The analyzed ACC structure was a bay having a length of <NUM> ft and a width of <NUM> ft, and containing three tube bundles of finned condenser tubes. The three fans used in the ACC bay all had a diameter of <NUM> ft.

The air flow streamlines were calculated according to different wind speeds and predicted the decrease in air flow rate at the exit of the ACC fans during windy conditions. These predictions were verified by actual smoke tests at the Don Campbell geothermal power plant.

Claim 1:
A wind guiding apparatus (<NUM>, <NUM>, <NUM>, <NUM>), comprising:
a) an air-cooled condenser (ACC) (<NUM>) arranged as a rectangular array with a length (L) longer than a width (W), the ACC (<NUM>) comprising:
i. a condenser tube section (<NUM>) having a plurality of widthwise spaced and lengthwise extending condenser tubes (<NUM>) and installed at a distance (FH) above an underlying ground surface (<NUM>); and
ii. a plurality of widthwise and lengthwise spaced fans (<NUM>, 26A-C) installed above said condenser tube section (<NUM>), to cause a flow of air from below the air-cooled condenser (ACC) through said condenser tube section along a fan-drawn air flow streamline (<NUM>) flowing to a corresponding one of said fans; and
b) a plurality of support structures (<NUM>, 15A-C, 18A-C, 27A-C) supporting the air-cooled condenser (ACC) from below and above the underlying ground surface; and
c) one or more stationary wind guiding vanes (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>-<NUM>, <NUM>-<NUM>) located below the plurality of condenser tubes (<NUM>), each of said wind guiding vanes is inclined with respect to the underlying ground surface (<NUM>), such that a downstream edge (<NUM>) of the wind guiding vane is located at a greater height than a corresponding upstream edge (<NUM>) thereof and is pointing towards a second widthwise end (<NUM>) of the air-cooled condenser (ACC) and away from a first widthwise end (<NUM>) thereof, and is connected to, and immobilized by, at least some of said support structures (<NUM>, 15A-C, 18A-C, 27A-C), characterized in that each of said wind guiding vanes (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>-<NUM>, <NUM>-<NUM>) is fixed in place below the first widthwise end (<NUM>) of the ACC (<NUM>) and is capable to redirect air flow from fairly horizontal inflow that is perpendicular to the length (L) of the ACC towards a portion of said plurality of condenser tubes (<NUM>) and at least one of said fans (<NUM>, 26A-C) at such an angle that deviates from perpendicular, fairly horizontal inflow.