Evaluation of the Hot Air Recirculation Effect and Relevant Empirical Formulae Applicability for Mechanical Draft Wet Cooling Towers

Abstract

<jats:p>Due to the hot air recirculation, the inlet air enthalpy h1 of mechanical draft wet cooling towers (MCTs) was usually greater than the ambient air enthalpy ha. To realize the cooling performance and accurate design of MCTs, this paper clarified the feasibility of the inlet air enthalpy empirical formula presented by the Cooling Technology Institute (CTI) of the USA. A three-dimensional (3D) numerical model was established for a representative power plant, with full consideration of MCTs and adjacent main workshops, which were validated by design data and published test results. By numerical simulation, the influence of different wind directions and wind speeds on hot air recirculation (HAR) and the influence of HAR on the cooling performance of the MCTs were qualitatively studied based on the concept of hot air recirculation rate (HRR), and the correction value of HRR was compared with the calculated value of the CTI standard. The evaluation coefficient ηh, representing the ratio of the corrected value to the calculated value was introduced to evaluate the applicability of the CTI formula. It was found that HAR was more sensitive to ambient crosswind, and an increase in HRR would deteriorate the tower cooling performance. When the crosswind speed increased from 0 to 15 m/s, ηh, changed from 2.42 to 80.18, and the calculation error increased accordingly. It can be concluded that the CTI empirical HRR formula should be corrected when there are large buildings around the MCTs, especially under high-speed ambient crosswind conditions.</jats:p>

Comparative Study on the Cooling Characteristics of Different Fill Layout Patterns on a Single Air Inlet Induced Draft Cooling Tower

“…In the water spray zone, the initial velocity of water droplet is 3.5 m/s with a diameter of 3 mm. Below the fill zone, the water droplet has an initial velocity of 0.4 m/s with the diameter of 5 mm [34,35].…”

Study on the Influence of Circulating Water Bypass on the Thermal and Anti-Freezing Characteristics of High-Level Wet Cooling Tower

“…The heat released from the turbine exhaust steam in the condenser varies slightly in a stable wet cooling unit. When the unit operates at a stable power and circulating water flow rate, the cooling tower can be considered to be operating under a fixed heat load condition, and the temperature drop of the circulating water throughout the cooling tower can be considered to be constant [21,22]. Therefore, increasing the inlet water temperature of the cooling tower can increase the outlet water temperature, thereby preventing the circulating water from freezing due to a too-low temperature in the cooling tower.…”