Energy efficiency indicators of cooling towers

For selecting optimal regimes and design characteristics, an energy efficiency criterion of a mass transfer apparatus is considered, and on its basis, some particular cases of energy efficiency criteria for cooling towers, including the cases with a structured counter-current film-type packing, are obtained. The criteria include heat transfer efficiency in the gas and liquid phases, as well as kinetic characteristics of the process of cooling the water in blocks of film-type packings. Expressions are given for determination of thermal efficiencies in the gas (air) and liquid (water) phases of the cooling tower. Three notations for the energy efficiency criterion of cooling towers are obtained. In the first notation, the efficiency criterion is written down using the thermal efficiency of cooling the water; in the second notation, it is written down using the thermal efficiency of heating the air; in the third notation, it is written down via the transfer coefficient (mass transfer) and mean driving force in the form of an enthalpy difference. A notation of writing down the energy efficiency criterion for a film-type packing in the cooling tower with a volumetric mass transfer coefficient is presented. Irrigator blocks filled with structured film-type contact devices of various designs having an irrigation density of 12 m³/m²h and an air speed of 1.5 m/s are considered. Results of calculations of five types of structured packings are presented: tubular packing made of polyethylene net; metal packings VACU-PAK, PIRAPAK G, “Inzhekhim” IRG and segmentary-structured packing “Inzhekhim”. Values are obtained of the criterion of energy efficiency of these packings for cooling the water as well as the required height of irrigator blocks for a given temperature regime and hydraulic load. Values of the power expended for supplying the air to the irrigator blocks are determined and a histogram is plotted. It is concluded that modern domestic and foreign metal packings have high thermal and hydraulic efficiency and are recommended for use in mini-cooling towers (except for tubular packings made of polyethylene net). For reducing the cost of irrigator blocks, these can be made of polymer materials. Then such blocks of irrigators are recommended for creating a contact between the phases in large-scale cooling towers, which will significantly improve the efficiency of cooling the water at thermal power plants and industrial enterprises.

1. Gortyshov Yu. F., Olimpiev V. V., Baigaliev B. E. Thermohydraulic calculation and design of equipment with intensified heat transfer. Kazan: Kazan A. N. Tupolev State Technical University Press 2004: 432.

2. Antufiev V. M. Efficiency of various forms of convective heating surfaces. – Moscow: Energiya Publishing House 1966;: 1–184.

3. Basharov M. M., Laptev A. G. Integrated assessment of heat and mass transfer and power characteristics of contact devices. Nadezhnost’ i bezopasnost’ energetiki 2014; 4(27): 50–54. (in Russ).

4. Ostrovsky G. M., Lapteva T. V., Ziyatdinov N. N. Optimization of technological systems. – Moscow: KNORUS 2012;: 432.

5. Sokolov V. N., Domanskii I. V. Gas-liquid reactors. – Leningrad: Mashinostroenie Publishing House 1976;: 216.

6. Zhou Y., Zhu X., Ding X. Theoretical investigation on thermal performance of new structure closed wet cooling tower // Heat transfer engineering. vol. 39, 2018;: 460–472. (in Eng).

7. Ponomarenko V. S., Arefiev Yu. I. Cooling towers of industrial enterprises and power plants. Reference manual; under the general editorship of V. S. Ponomarenko. Moscow: Energoizdat Publishing House 1998;: 1–376.

8. Laptev A. G., Vedgaeva I. A. Designs and calculations of industrial cooling towers. – Kazan: Kazan State Power Engineering University press 2004;: 180.

9. Laptev A. G., Farakhov M. I., Basharov M. M. et al. Energy- and resource-saving technologies and apparatuses for cleaning of fluids in petrochemistry and power engineering. Kazan: Otechestvo 2012;: 1–410.

10. Lapteva E. A., Laptev A. G. Applied aspects of transport processes in apparatuses of chemical and heat-power engineering (hydromechanics and heat and mass transfer). Kazan: Pechat-Servis-XXI vek 2015;: 1–236

11. Ramm V. M. Absorption of gases. Moscow: Khimiya Publishing House 1976;: 1–655

12. Sokol B. A., Chernyshev A. K., Baranov D. A. Packings of mass transfer columns. Moscow: Galleya-print 1976;: 1–655

13. Kagan A. M., Laptev A. G., Pushnov A. S., Farakhov M. I. Contact packings of industrial heat and mass transfer apparatuses. Kazan. Otechestvo 2013;: 1–454