13. Cooling Towers and Spray Pondsconversion
Power plants are not always located adjacent to a plentiful supply of condensing water. At other times the source of supply found to be contaminated by the prence of foreign matter which would prove injurious to the pumps, condenr ,and circulating systems through which the water must pass. The cost of placing this water in a satisfactory condition for u would prove prohibitive. Yet if the turbines are to be operated condensing, cold water is required.
Hence cooling tower and spray ponds are provided where sufficient water is not available, their purpo being to discharge the heat absorbed in the condenr. In order to do this in the shortest possible time , the water must be broken up into very fine spray to prent to the atmosphere as much water surface as possible!
Both the spray and the cooling tower enjoy advantages depending upon the specific installation for which they are intended and must be evaluated accordingly. The factors to be considered in choosing between a cooling power and a spray pond ate the amount of w
homelandater to be cooled, the amount of degree of cooling desired, the cost of water makeup, piping, space available for installation, pumping cost, water-treatment cost, fixed charges, maintenance and operation.怎样提高写作能力
Cooling ponds and spray ponds are usually less expensive to install and maintain than cooling towers. However, better results are obtained with a properly designed cooling tower, since it can provide water at lower temperature, which in turn can produce a better or lower vacuum in the condenr. The cooling tower is very compact and can be located almost anywhere that space permits, such as the top of buildings, etc. It is usually installed where land is expensive. By comparison, a spray pond requires considerably less area than cooling pond.
stimulate
The principle of cooling applied in both cooling pond and tower is that of transferring nsible heat in the condensing water to the atmosphere, thereby lowering the water temperature. Most of the cooling is due to exchange of latent heat resulting from evaporation of a small portion of the water. In cooling(evaporation) some water is lost; it amounts to approximately 1 percent for each 6℃ to 8℃ of actual cooling.
工程结算
pope
terminals
Influencing factors which must be taken into consideration are wind direction and velocity. The extent of cooling is also depended upon the air of water expod to atmosphere and the temperature of the water when it enters the basin. Cooling is brought about by evaporation and conduction.
The degree to which the temperature of the water approaches the air wet-bulb temperature is a measure of performance for the pond and cooling water.
The wet-bulb temperature of the surrounding atmosphere is the theoretical point to which water can be cooled. Usually it is not economical to approach clor than 3℃of the wet-bulb temperature .The temperature drop(cooling range) will vary from 6℃ to 7℃ for a spay pond versus 7 to 10 for a mechanical-draft cooing tower. Since the wet-bulb temperature of air varies geographically, it follows the performance of a cooling tower will also vary with its location. So the wet-bulb temperature record for a given location must receive consideration when a tower is being desired.
The cooling pond is employed where space adjacent to the power plant is plentiful and where land is relatively inexpensive. Cooling ponds are also employed in certain parts of the country where atmosphere conditions are favorable. As an example, a cooling pond located in an area where the relative humidity is usually low would prove more effective than one installed in an area where the humidity approaches 100percent.迈克尔杰克逊歌曲
Occasionally the decision to u a cooling or spray pond is bad on the fact that it is possible to take advantage of a natural water hole or depression in which water can be stored and cooled and which could be ud at little or no expen.
The advantages of the force-draft tower are that it is suitable for corrosive waters; that the fan can be mounted, firmly, clo to the ground; and that the fan is accessible. Its disadvantage are recirculation of air with reduction in tower efficiency (air leaving the tower exits at low velocity), higher fan power requirements and hence incread operating cost, and incread maintenance. Also since the size of the fan is limited, more fans and foundations may be required.
sars怎么读
The induced-draft tower discharges the air at a high velocity, thereby avoiding recirculation; induced-draft fans are usually quiet in operation and permit more uniform air distribution. They have, however, veral disadvantages: the require a heavy superstructure, they must be perfectly balanced, and they are some what difficult to rvice when major repairs are required.
>jaggad
