JP2006517647A - Cooling system - Google Patents

Abstract

It is possible to quickly switch between a wet operation and a dry operation as required, and to be substantially flexible so that there is no drawback when a drainage reservoir is provided at a remote location. To provide a closed circuit evaporative heat exchange device with advantages.
A closed circuit evaporative heat exchange device includes an air distribution plenum (4), means for spraying water into the plenum (4) and a collecting surface for collecting non-evaporated water sprayed into the plenum (4). 22). The water is drained into a sump (16) in the plenum (4) without remaining on the collection surface (22).

Description

  The present invention relates to a cooling system, and more particularly to a cooling system having a closed-circuit evaporative heat exchange device with a forced draft structure.

  Closed circuit evaporative heat exchangers are used in various industrial settings for cooling and refrigerant condensation. In general, cooling is accomplished by using a cooling fluid that extracts heat from the area to be cooled and conveys this heat to a heat exchanger. In the heat exchange device, the fluid is cooled again. In the case of a refrigerant condensing system, refrigerant vapor enters the heat exchanger as part of the cooling process. In this heat exchange device, the refrigerant vapor is condensed and remains as a liquid in the heat exchange device. In both cases, air is sent to the heat exchange coil to remove heat from the liquid or vapor. The cooling process is facilitated by spraying water onto the coil and a proportion of the water is evaporated by the air stream.

  In such a system, most of the water sprayed on the heat exchange coil in the air distribution plenum is drained into a drainage reservoir provided at the bottom of the air distribution plenum without evaporating. Water is pumped up from the drainage reservoir through the strainer, returned to the spray nozzle, and reused. Typical evaporative heat exchanger products are designed to use components common to both closed circuit and open cooling towers. The drainage reservoir in the conventional closed circuit tower has a sufficiently large capacity that can be used for the open tower as well as the closed circuit structure.

  As described above, the cooling performed by the heat exchange device is facilitated by spraying water onto the coils of the heat exchange device. However, such accelerated cooling is not always necessary. For example, in winter, sufficient cooling can be performed without using the water evaporation effect. That is, a so-called “drying operation” is possible.

  However, a drainage reservoir for draining is also required in the drying operation, otherwise water is frozen by the forced flow of cooling air to the system and damages the system. This is a problem because the draining and replenishment process in the sump is time consuming and usually takes several hours. In addition, the cooling system should normally be turned off at least during a portion of the drain or refill period to prepare each drainage reservoir for dry or wet operation by installing float valves, level controllers, etc. Is required. For this reason, practical or economic feasibility for daily drainage and replenishment of the sump is not considered. This means that the drying operation can only be performed in a short period of time every year, even during the daytime, when the temperature is sufficiently low as expected and a “wet” operation is not required. As a result, it will be appreciated that the possibility of saving water and the power required for the operation of the water pump or drainage heater is greatly reduced.

  It is also known in some closed circuit evaporative heat exchanger systems to place a sump far from the air distribution plenum. During the wetting operation, most of the water that has not evaporated (non-evaporated) is drained or pumped continuously to a remote sump, pumped back from this remote sump and sprayed back onto the heat exchange coil. The The advantage of such a remote drainage reservoir is that only a small amount of water remains in the air distribution plenum and drains relatively quickly, so that the entire water is drained in the air distribution plenum for drying operations. There is no need to drain from. The water in the remote sump does not come into contact with the cooling air flow in the air distribution plenum, and refrigeration can be prevented by a suitable heater.

  However, there are several problems with remote drainage reservoirs. First, additional space is required to fit in this sump and is generally expensive. Secondly, more powerful pumps are needed to accommodate the additional static height required for water to be pumped. Thirdly, the total number of components required and the installation costs also increase. These complex factors may outweigh the costs saved by operating a more efficient system with respect to water consumption and spray pump power. However, a remote sump is required to perform a drying operation to prevent overcooling under various circumstances.

  Another problem with the configuration of the conventional closed circuit evaporative heat exchange device is that the system must be interrupted in order to perform periodic maintenance such as inspection, functional test, and cleaning of components in the air distribution plenum. This is particularly problematic for conventional systems that do not have a remote sump. This is because the equipment in the sump and the water assembly system are affected. Obviously, such periodic interruptions in system operation are prone to failure and costly.

  An object of the present invention is to provide an evaporative heat exchange device that can at least partially solve the above-described problems.

  According to a first aspect, the present invention provides an air distribution plenum, means for spraying water into the plenum, and a collection surface for collecting non-evaporated water sprayed onto the plenum, the water comprising A closed circuit evaporative heat exchange apparatus comprising: a collection surface adapted to be drained to a sump within the plenum without substantially remaining on the collection surface.

  For those skilled in the art, a sump is provided in the main air distribution plenum, but this sump is not used to collect non-evaporated water, but instead the collection surface drains into the sump. Can understand. This means that the sump is at least partially thermally isolated from the main part of the plenum. As a result, water can be prevented from freezing even when the temperature of the surrounding air falls below the freezing point. In contrast, this cannot be achieved with a conventional drainage arrangement that contacts the airflow within the plenum. In such a configuration, it is possible to quickly switch between the wet operation and the dry operation as required, and substantially without any disadvantages when the drainage reservoir is provided at a remote location. There is an advantage of flexibility.

  The sump is configured to prevent water from freezing during operation in cold weather. This can be achieved by ensuring sufficient heat isolation and by providing heating means, preferably thermostatically controlled. This also makes it possible to change the ambient temperature.

  The collection surface is simply configured to allow drainage into a drainage reservoir below the collection surface. That is, the arrangement is substantially the same as that of the conventional configuration, but a lid or the like that covers the drainage reservoir and has one or more drain holes is provided. In this case, the upper surface of the lid forms the collection surface.

  However, it is a drain joint provided between the collection surface and the sump, forming a liquid lock between the collection surface and the sump, and maintaining different air pressures between the two. It is preferable to further include a drain joint portion configured as described above. The advantage of this feature is that the sump is maintained at substantially atmospheric pressure, whereas the main part of the plenum is increased in pressure by an externally applied air flow. By physically isolating the interior of the sump from the interior of the main air distribution plenum, contact with water sprays can also be avoided. Due to these two factors, even if the system is in operation by operating the fan, at least the drainage reservoir can be accessed for maintenance. It will be appreciated that such performance provides a significant advantage over prior art systems that must be deactivated during routine maintenance.

  The amount of water used for spraying and circulating through the system via the sump was approximately the same in the prior art as for the sump used for the open tower cooling system. However, although the applicant loses the small benefit of the commonality between the modules of the sump with the present invention, the use of a common sump no longer requires a reduction in capacity and requires less water. We have found that using this means that additional benefits are actually achieved.

Thus, in a more preferred embodiment, the evaporating water spray system is configured to operate with just enough water to be used for the wetting operation. In one exemplary embodiment, the system is adapted to operate with about 90 liters of water per square meter of coil area. This is in contrast to conventional systems where a water volume of about 240 liters / m ² is used (as is constant when using a standard size sump).

  A sufficient reduction in the amount of water not only saves water, but also reduces the sump compared to other cases, and heating required to prevent water from freezing. The performance of the vessel can be reduced, less chemical water treatment is required, and all of these matters can reduce costs.

  It will be appreciated that the preferred embodiment of the present invention described above involves the use of the minimum amount of water required in the evaporation process. In practice, this minimum amount of water is needed to properly operate the capacity of the water distribution system, including piping, the fraction of water falling through the air distribution plenum at any given time, and the pump system. It is determined based on the minimum amount of water. This is in contrast to the prior art where an amount of water sufficiently larger than the minimum amount of water for a wetting operation is used, but this minimum amount of water is not actually taken into account.

  It will be appreciated that in the present invention, means are provided for actually replenishing water lost due to evaporation. Various means known from the prior art such as float operated valves, electronic sensors, optical sensors etc. can be used. Such water replenishment has an inherent history phenomenon that the actual amount of water in the system at any point in time circulates between preset maximum and minimum amounts.

  Preferred embodiments of the invention are described below by way of example only with reference to the accompanying drawings.

  First, FIG. 1 shows a prior art closed circuit evaporative heat exchanger. A sealed heat exchange coil A through which the cooling liquid passes is provided in an air distribution plenum (air distribution chamber) B. A fan system C driven by a motor D is provided at one end of the plenum B. A plurality of nozzles E are provided at the top of the plenum B, and these nozzles E are configured to spray water on the heat exchange coil A. A drainage reservoir F is provided at the bottom of the plenum B. The drainage reservoir F has a processing capacity of 240 liters per square meter of coil area, and a pump G for pumping water from the drainage reservoir F to the spray nozzle E is installed. ing. A water replenishment system H that uses a float valve maintains a minimum amount of water in the sump.

  As is well known from the prior art, when performing an operation, a cooling liquid or refrigerant vapor is supplied to the heat exchange coil A and cooling or condensation is performed before the heat is removed and returned to its original state. Fan C supplies rapid air to heat exchange coil A in air dispersion plenum B to extract heat from the cooling fluid or steam. Evaporative cooling is performed by a water spray system in which water is pumped from the drainage reservoir F using the pump G. A part of the water sprayed from the nozzle E evaporates. The remaining water is collected in the drainage reservoir F, returned to the spray nozzle E, and reused. Water lost due to evaporation is replenished by a water replenishment system H.

  In order to access the drainage reservoir F for inspection or maintenance, it is necessary to interrupt the system and switch off the fan C. This limits the number of times the operation can actually be performed. In addition, if the ambient temperature is such that it no longer requires the additional cooling effect of the water spray system, all of the water can be prevented from freezing due to the cooling effect of the forced cooling air flow. Water must be drained from the sump F. This is very time consuming and can only be done for a significant period of time (eg a period of one day or more) only when the operator is convinced that the temperature will not rise sufficiently again until a moistening action is required. .

  An embodiment of the present invention will be described with reference to FIGS. 2a and 2b. Similar to the device described with reference to FIG. 1, the closed circuit evaporative heat exchange device comprises a heat exchange coil 2 arranged in an air distribution plenum (air distribution chamber) 4, this heat exchange coil 2. Is adapted to transport a cooling fluid or refrigerant to or from a region to be cooled (not shown) via a pipe connector 6. A fan 8 driven by a motor 10 via a belt 12 is disposed at one end of the air distribution plenum 4. The rotor blades of the fan 8 are accommodated in the casing 14 and cannot be seen in FIG. 2a.

  Unlike the system shown in FIG. 1, the bottom of the air distribution plenum 4 is not provided with an open sump. Instead, a sump 16 is defined by an inclined baffle wall 18 at a lower portion of one end of the air distribution plenum 4. In this embodiment, the sump has a capacity of 90 liters per square meter of coil area, but this is merely exemplary and this number is determined by, for example, the length of the coil. The baffle wall 18 extends downward from the rear end wall 20 of the plenum 4. The end point of the baffle wall 18 is determined so as to leave a gap between the end portion of the baffle wall 18 and the base portion of the drainage reservoir 16. The baffle wall 18 extends between two opposing side walls of the plenum 4. In other words, it extends perpendicular to the page of FIG. 2a or from left to right in FIG. 2b.

  An inclined base portion 22 is formed in a region of the lower portion of the air distribution plenum 4 that is not pumped by the drainage reservoir 16. The base portion 22 is inclined toward the baffle wall 18, but the end point is determined so as to leave a small gap 24 extending from one side wall of the plenum 4 to the other. The base also extends between the two sidewalls and the gap 24 extends along the width of the plenum 4. The baffle wall 18 and the base portion 22 each form a collection surface on which water dropped from the heat exchange coil 2 lands.

  A float operation valve 26 is provided in the drain 16 and is connected to a water inlet 28 for maintaining a minimum height level of water in the drain 16. This water level is set to maintain the minimum amount (considering pipe capacity, etc. in the rest of the system) required for the wet operation of the heat exchanger.

  A strainer 30 is provided at the base of the drainage reservoir 16, and water is drawn from the drainage reservoir through the strainer 30 by a pump 32 and pumped to a vertical pipe 34 outside the rear end 20 of the plenum. The vertical pipe 34 reenters the plenum 4 to supply water to the distribution pipe 36.

  A plurality of nozzles 38 are arranged at intervals along the water distribution pipe 36, and the pressure applied by the pump 32 pushes water to spray toward the heat exchange coil 2 in a conical shape. An example of such a nozzle 38 is more clearly shown by a detailed view of the upper cutout. Above the water distribution pipe 36, a plurality of rectifiers 40 are provided, and an example of this rectifier is likewise shown more clearly in the cutout detail. These separated water droplets can be trapped in the air stream and remain in the heat exchange device, preventing these water droplets from being lost from the system.

  Finally, a pair of access doors 42 are provided in the lower portion of the plenum end wall 20 to allow external access to the interior of the sump 16.

  The operation of such a device is described below. As shown in the prior art system, the fan 8 blows air onto the heat exchange coil 2 and extracts heat from the cooling fluid in the coil 2. When additional cooling is required, the pump 32 is activated to pull water from the drain 16 through the strainer 30 and push water into the nozzle 38 to provide sufficient spray to the heat exchange coil. A sufficient cooling effect is obtained by evaporating a part of the water. The water that has not evaporated (non-evaporated water) falls towards the bottom of the air distribution plenum 4 and reaches the collection surface formed by the baffle wall 18 or the inclined base 22. The water that falls on these parts does not remain there, but is drained into a small gap 24 between them.

  As can be seen from FIG. 2a, the level of water in the sump is such that the gap 24 is at least partially filled with water. This forms a water lock between the air distribution plenum 4 and the drainage reservoir 16. By this water lock, different air pressures are maintained between the main part of the plenum 4 and the drainage reservoir 16, and the reservoir 16 can be accessed for inspection or maintenance. During this time, the operation of the main fan 8 can be continued and the system can be operated.

  During the drying operation, the pump 32 is stopped and the remaining water flows into the drainage reservoir 16 through the gap 24. Within the sump 16, the water is no longer in direct contact with the air flow generated by the fan 12. It can be seen that the water is no longer left in the main part of the air distribution plenum 4, i.e. it does not come into contact with the cooling air flow, so that the possibility of water freezing is greatly reduced.

  Although not shown in FIG. 2a, a thermostat controlled heater is provided to maintain the temperature of the water in the sump 16 above the freezing point. However, because the sump 16 is relatively small compared to the distribution plenum 4 and the sump 16 is isolated from the cooling air flow by the baffle wall 18, the power required for such a heater is relatively low. Get smaller.

  Further, it will be understood that the amount of water in the drainage reservoir 16 is sufficiently smaller than the amount of water in the drainage reservoir F of FIG. This not only saves the amount of water required to fill the device, but also reduces the cost of chemical treatment required and the amount of heat required to prevent the water from freezing. Can be saved.

  Such an embodiment has the overall advantage of being flexible enough to be able to operate in wet or dry modes as required and to switch between these modes very quickly. can get.

  A prototype device similar to that described above as referenced by FIGS. 2a and 2b was assembled and tested. The test machine drainage water capacity was 860 liters and the fan sent an air flow of 27 cubic meters per second to the heat exchange coil. However, the normal atmospheric pressure inside the drainage reservoir was maintained by the water lock function.

  When the pump of the evaporative cooling system is switched off and the ambient temperature drops to -10 ° C, the sump and water lock are completely frozen by the heat sent from the sump heater with moderate power of 4KW. It never happened.

1 is a cross-sectional view of a conventional closed circuit evaporative heat exchange apparatus shown for reference only. 2a and 2b show a longitudinal section and an end view, respectively, of a closed circuit evaporative heat exchanger according to the invention.

Claims (4)

An air distribution plenum;
Means for spraying water into the plenum;
A collection surface for collecting non-evaporated water sprayed into the plenum, wherein the water is drained to a sump located within the plenum without substantially remaining on the collection surface. Like a collecting surface,
A closed circuit evaporative heat exchange apparatus comprising:   A drain joint portion provided between the collection surface and the drainage reservoir, wherein a liquid lock is formed between the collection surface and the drainage reservoir, and different air pressures are maintained between the two. The heat exchange apparatus according to claim 1, further comprising a drain joint portion.   3. A heat exchanger according to claim 1 or 2, wherein the means for spraying water is configured to operate with just enough water to be used for the wetting operation of the heat exchanger.   4. A heat exchanger according to claim 3, wherein the heat exchanger is configured to operate with about 90 liters of water per square meter of coil area.

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