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Zhao Y.B.,Shandong University | Long G.,Guangdong Electricity Power Design Institute | Sun F.,Shandong University | Li Y.,Shandong University | Zhang C.,Shandong University
Applied Thermal Engineering | Year: 2015

(Graph Presented). To study the cooling performance of a natural draft dry cooling tower with vertical two-pass column radiators (NDDCTV) under crosswind, a three-dimensional (3D) numerical model was established for NDDCTV and validated by some published results. By the numerical model, the aerodynamic field around cooling columns was computed and analyzed at 4 m/s crosswind. It was found that the large inflow air deviation angle at delta entry induced large eddy near column θ-1. With the air static pressure contours, the air mass fl ow rates through each column, delta and sector were analyzed and calculated. Based on the water temperature distribution at column exits, the exit water temperatures of each column, delta and sector were presented and analyzed. So the crosswind impact mechanism on each sector and the tower was clarified. With the increasing crosswind velocity, the cooling performance of tower deteriorates rapidly. But at high velocity crosswind, the tower performance varies gently. © 2014 Elsevier Ltd. All rights reserved. Source


Zhao Y.,Shandong University | Long G.,Guangdong Electricity Power Design Institute | Sun F.,Shandong University | Li Y.,Shandong University | And 2 more authors.
Energy Conversion and Management | Year: 2015

To study the effect mechanism of air deflectors on dry cooling tower, a three dimensional numerical model was established, with full consideration of the delta structure. The accuracy and credibility of dry cooling tower numerical model were validated. By numerical model, the average air static pressure and the average radial inflow air velocity were computed and analyzed at delta air entry, sector air entry and exit faces. By the air inflow deviation angle θd, the effect of air deflectors on the aerodynamic field around tower was analyzed. The water exit temperatures of θ-1 columns, θ+2 columns and cooling sectors were also presented to clarify the effect of air deflectors. It was found that the air deflectors improved the aerodynamic field around cooling columns. The reduced air inflow deviation degree at delta entry improved the cooling performance of deteriorated columns. Referring to the radial inflow air velocity ura and the air inflow deviation degree at delta entry, the effect mechanism of air deflectors are clarified under crosswind. © 2015 Elsevier Ltd. All rights reserved. Source


Zhao Y.,Shandong University | Sun F.,Shandong University | Long G.,Guangdong Electricity Power Design Institute | Huang X.,Guangdong Yuedian Group Co. | And 2 more authors.
Energy Conversion and Management | Year: 2016

With the rapid development of large capacity power units, high level water collecting natural draft wet cooling towers (HNDWCTs) are now attractive. To study the cooling characteristics of HNDWCT, a three-dimensional (3D) numerical model for a HNDWCT was established and validated. Combining with the verified 3D numerical models for usual natural draft wet cooling towers (UNDWCTs), the parameters such as air pressure drop, air mass flow rate, exit water temperature, cooling load percentage of each zone, air velocity, air temperature and H2O mass fraction were elaborated for HNDWCT and UNDWCTs under the same work conditions. Comparing with UNDWCTs, the cooling characteristics of HNDWCT were analyzed and highlighted. The cooling load percentage of fill zone in HNDWCT is far larger than those in UNDWCTs for the large air mass flow rate and large heat transfer potential. Under high velocity crosswind impacts, blocking the cross ventilation through HNDWCT is favorable to its cooling performance. Suggestions concerning the orientations of water collecting gutter and cross wall are presented. © 2016 Elsevier Ltd. All rights reserved. Source


Zhao Y.,Shandong University | Sun F.,Shandong University | Li Y.,Shandong University | Long G.,Guangdong Electricity Power Design Institute | Yang Z.,Guangdong Electricity Power Design Institute
Applied Energy | Year: 2015

From the view of cooling system, the natural draft dry cooling tower with vertical delta radiators (NDDCTV) under constant heat load can be studied by keeping constant water temperature drop δtw. With computed entry water temperature tw1 as the sum of tower exit water temperature tw2 and the constant δtw, a three-dimensional (3D) numerical model for NDDCTV under constant heat load was established. Through analyses about mesh-independence, sensitivity about crosswind profile index and comparison with published results, the accuracy and credibility of the established numerical model for NDDCTV were confirmed. The aerodynamic field around cooling deltas was analyzed at windless and crosswind conditions, so as to clarify the impacts of ambient air temperature and air inflow deviation angle θd on the performance of cooling columns. With constant heat load and uniform entry water temperature, the cooling performance of each sector was analyzed under crosswind impact. With increasing crosswind velocity vc, the cooling performance of NDDCTV under constant heat load deteriorates sharply at low vc, but varies slightly at high vc, which can be improved by air deflectors. © 2015 Elsevier Ltd. Source

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