Analysis of formulas for computing coefficients of heat and mass transfer derived on the basis of results of laboratory tests of 22 sprinklers is used to show that the classification of sprinklers into film and drop ones can be based on a physically grounded parameter m, i.e., the exponent in the formula for the evaporation number K ev = A p ë m (or for the Merkel number Me = A x ë m ). A generalized formula describing the dependence of the coefficients of heat and mass transfer on the height of the sprinkler is derived, which makes it possible to determine the optimum sprinkler height in cooling tower design. The accuracy of the formulas for computing the coefficients is confirmed by a comparison of experimental and computed values of the temperature of cooled water in the cooling tower of the Novo-Ryazanskaya cogeneration plant.A sprinkler is an important component of a cooling tower, which determines the efficiency of cooling of the circulating water. The thermal efficiency of a sprinkler is primarily determined by the coefficients of heat and mass transfer. In order to evaluate the thermal efficiency of a cooling tower designers perform process computations, the accuracy of which depends on the quality of determination of these coefficients from data of laboratory tests.According to a contract between the RAO EÉS Rossii ("UPS of Russia") Company and the Vedeneev All-Russia Research Institute for Hydroengineering we have updated a test bench for determining the coefficients of heat and mass transfer and aerodynamic drag of sprinklers. At present, a great number of current-technology polymer sprinklers have been tested, their main characteristics determined, and recommendations given on their use [1]. In the present paper we will show that the formulas for computing the coefficients of heat and mass transfer used in [1] are physically grounded and ensure enough accuracy of process computations.In order to determine the coefficients of heat and mass transfer, the intensities of flow of water and air, the temperatures of hot and cooled water, the temperature and the relative humidity of air, and the barometric pressure are measured on a laboratory bench in every test. The equipment for measuring these quantities on the bench has passed metrological examination and the latter has proved the accuracy of the measurements. However, the accuracy of determination of individual quantities does not ensure the correctness and accuracy of the final result, i.e., of the values of the coefficients of heat and mass transfer, because the latter are computed with the help of a rather intricate mathematical method. The errors of measurement of some quantities have a complex and uncertain influence on the correctness and accuracy of the computed coefficients.The method developed at VNIIG determines the coefficients of heat and mass transfer by solving an inverse problem for systems of differential equations of heat and mass transfer in a sprinkler [2]. The sought-for coefficients in every test are such that the design temperature...
In any explanation of cooling tower operation, it is shown that the ambient wet bulb temperature is a physical limit for water cooling. The main advantage of the Maisotsenko cycle (Mcycle) is the possibility to have the cold water temperature lower than the ambient wet bulb temperature, without violation of any physical principle. The idea is based on the fact that the ambient wet bulb temperature depends not only on the absolute humidity value, but also on a current air temperature. On the contrary, the dew point temperature depends only on the absolute humidity value. If we can provide lower temperature of the air (with the same absolute humidity) at the air inlet of the cooling tower, then the wet bulb temperature for such air will be lower. Therefore, if we can cool the air entering the cooling tower, without the change of its absolute humidity, it will be possible to cool the water more and, for some conditions, its temperature could be lower than the wet bulb temperature of the surrounding air at some distance from the cooling tower. However, the main problem is how to cool the air entering the cooling tower, very simply and without significant energy consumption. A theoretical possibility to solve this problem by application of the M-cycle is under analysis in this paper.
Various forms of standard temperature nomograms for cooled water are analyzed. It is recommended to use a single standard form of computed nomograms for chimney, mechanical-draft, and ejection cooling towers. The nomogram makes it possible to determine the temperature of cooled water during operation of a cooling tower in both closed and open cycles. The working nomogram is readily corrected by data derived from full-scale tests. For mechanical-draft and ejection cooling towers, the nomogram makes it possible to construct an operational nomogram, which determines the temperature of the cooled water as a function of the temperature as read from a wet-bulb thermometer.The characteristics of any cooling tower can be represented in the form of nomograms permitting determination of the cooled water as a function of parameters of the ambient air, and also the hydraulic and heat loads on the tower. The existence of these nomograms makes it possible to predict operating conditions of a turbine-driven set, or other water-cooled equipment, and to monitor the technical in-service status of the cooling tower.There are two basic types of evaporative cooling towers: chimney and mechanical-draft. Evaporative ejection cooling towers have recently come into use. This paper analyzes two graphic forms of nomogram representation for cooling towers, which are cited in regulatory documents, and substantiates the recommended form.In the nomograms, parameters of the ambient air are given by the temperature è 1 and relative humidity ö 1 . The barometric pressure for which the nomogram is calculated and constructed is determined by the elevation where the tower is located from the barometric formulawhere P b is the pressure, MPa, and Ñ is the elevation of the tower's location, m.In regulatory documents on cooling towers, it is accepted to present plots and nomograms calculated and constructed for P b = 0.0993 MPa (745 mm Hg), i.e., for a value Ñ = = 160 m, which corresponds to the elevation of the median zone of Russia.The hydraulic load on the cooling tower is assigned as the flow rate of water Q. The flow rate determines the specific load -the water concentration q 1 , which enters into the nomogram as a regime parameter. A second regime parameter entering the nomogram is the temperature differential Ät. The product of the flow rate and temperature differential defines the heat load on the cooling tower.Two basic graphic forms are currently used to present characteristics of cooling towers.One form is a nomogram of the type shown in Fig. 1. The values of è 1 , ö 1 , q 1 , and Ät are parameters input to the nomogram for determination of the temperature t 2 of the cooled water.This type of working nomograms for the "new series" of standard chimney cooling towers with an irrigated area of 1100, 1600, 2300, and 3200 m 2 and a two-tier asbestos-cement ATs-25 sprinkler 2.45 m high are cited in [1]. The analyses were performed by the VNIIG with consideration of cooling only within the limits of the sprinkler. The coefficients of heat and mass ...
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