Experimental research of the cross walls effect on the thermal performance of wet cooling towers under crosswind conditions

Chen, Youliang; Sun, Fengzhong; Wang, Hongguo; Mu, Nasi; Gao, Ming

doi:10.1016/j.applthermaleng.2011.08.001

Cited by 51 publications

(10 citation statements)

References 20 publications

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“…Kapas [8] found that cooling capacity first increases and then decreases as the crosswind speed rises according to numerical simulation and experimental results. Chen et al [9] indicated that heat transfer efficiency can decline due to inhomogeneous intake air around the tower inlet, the influence of which is greater than the air flow rate. Previous studies have suggested that a wind deflector can reduce the impact of crosswind on heat transfer and enhance the heat transfer rate in cooling tower radiators.…”

Section: Introductionmentioning

confidence: 99%

“…While extensive studies have explored air-cooled heat exchangers [4,[15][16][17][18][19][20][21] and air-cooling towers [7,[22][23][24][25][26], few have looked at air-cooling towers with rotating wind deflectors. To investigate the effects of rotating wind deflectors on the air flow and heat transfer performance in air-cooling towers, an experimental system based on a surface condenser aluminum exchanger (SCAL)-type indirect air-cooling tower has been established with a 1:100 proportional reduction according to the similarity principle, and 3-D numerical models of the prototype indirect air-cooling tower have been built.…”

Section: Introductionmentioning

confidence: 99%

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Heat Transfer Enhancement of the Air-Cooling Tower with Rotating Wind Deflectors under Crosswind Conditions

Han

Zhu

2018

Applied Sciences

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Heat Transfer Enhancement of the Air-Cooling Tower with Rotating Wind Deflectors under Crosswind Conditions

Han

Zhu

2018

Applied Sciences

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“…For instance, a study showed that the heat transfer rate decreased by more than 30% at crosswind velocities above 10m/s [11]. Wind break walls, by using either experimental [50] or numerical method [37,51], were found to improve the thermal performance of natural draft cooling towers under windy conditions. However, all the studies above focused on either Heller-type or surface-condenser-type indirect large natural draft cooling towers with heights above 100m.…”

Section: Discussionmentioning

confidence: 99%

“…Either porous or solid windbreak walls would have similar favourable effects on cooling tower performance. Chen et al [50] ran experiments on a scaled wet cooling tower model installed with the same windbreak walls and found that improvement in the cooling performance of the tower due to the windbreak walls depended on the setting angles of the walls. As an alternative option, wind shells placed on the periphery of the tower base were investigated by Wang et al [66] using a scaled model tower in the laboratory.…”

Section: Introductionmentioning

confidence: 99%

Small natural draft dry cooling towers for renewable power plants

Lu¹

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In thermal power plants using variety of heat sources, the redundant heat needs to be removed through cooling devices such as heat exchangers and cooling towers. Natural draft dry cooling towers (NDDCTs) feature no water loss and no parasitic power consumption during operation and are widely used in thermal power plants around the world, especially in arid areas. The Queensland Geothermal Energy Centre of Excellence (QGECE) is focusing on developing small-or mediumscale engineered geothermal system (EGS) geothermal and concentrated solar thermal (CST) power plants for Australia. The proposed renewable power plants are most likely to be located in arid remote areas where dry cooling is the only cost-effective option. These power plants may initially be introduced to supply remote communities away from the national grid. Such off-grid applications are expected to be relatively small reflecting the size of the demand. The aim of this Thesis project is to investigate whether natural draft dry cooling towers (NDDCTs) can be used for these small-or medium-scale renewable power plants.Crosswind is the most common factor affecting the cooling performance of natural draft cooling towers. But current NDDCT design procedures do not take the crosswind effect into account. It is probably not a critical impediment for large towers as the negative influence of the crosswind is negligible when the draft heights are above 100 m. On the other hand, in small NDDCTs with total heights less than 30 m, the crosswind effect could be substantial.A numerical study was carried out to investigate the thermal performance of the horizontally arranged heat exchangers in small NDDCTs under various crosswind conditions. In particular, a 15 m-high CFD NDDCT model was constructed and simulated to examine the crosswind actions in detail. It was found that at certain crosswind speeds the cooling tower performance can be considerably reduced. A very effective mitigation device, a tri-blade-like windbreak wall, has been found to dramatically improve the cooling performance of the small tower. The effect of the windbreak was sensitive to its orientation with respect to the crosswind direction.An experimental study was conducted with a 1:12.5 scaled natural draft dry cooling tower model in the wind tunnel. The thermal performance of the scaled tower was measured with and without the windbreak wall. The experimental results verified the numerical predictions for the small tower cooling performance and the effectiveness of the windbreak wall.The most important finding of this study is that the total heat transfer in a small natural draft cooling tower is a combination of the heat transfer by both natural convection and forced convection, with the contribution of the latter increasing at higher crosswind speeds. A simple correlation between II the heat transfer and the crosswind speed was proposed to estimate the crosswind-affected thermal performance of natural draft dry cooling towers at different sizes and with horizontal heat exchanger arrang...

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“…They claimed that the variation in the wall's porosity did not significantly degrade the thermal performance. In the wet cooling tower, Chen et al [104] proposed that the porous wall is even better than the solid wall. As discussed in section 2.2.6, the crosswind could increase the heat transfer performance in the rain zone.…”

Section: Internal Windbreak Wallmentioning

confidence: 99%

Numerical and experimental study of small natural draft dry cooling tower for concentrating solar thermal power plant

Li¹

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The typically arid climates in the likely locations for renewable thermal power plants such as Concentrating Solar Thermal (CST) power plants provide the motivation for dry cooling technology applications. Natural draft dry cooling tower (NDDCT) with low maintenance cost and no parasitic power consumption offers a feasible and cost effective option for such applications. Compared with the conventional coal fired and nuclear power plants, the size of the CST power plant proposed for Australian regional communities is much smaller. However, the existing cooling tower design is optimised for large steam power plants, and is not optimal for these renewable power plants. (2) The performance of the experimental tower was tested at two constant heat loads of 600 kW and 840 kW, respectively, with various ambient temperatures. The 1D numerical model was refined and validated with the experimental data. The thermodynamic model of a 1 MW CST power plant running with sCO2 cycle was developed and integrated with the updated cooling tower model. Significant differences were observed between the steam Rankine and sCO2 cycles in terms of the effect of the ambient temperature on power generation. The differences between steam Rankine and sCO2 Brayton cycle in this context were analysed and discussed.(3) Two potential cooling issues with small NDDCT, the crosswind and the cold inflow, were identified and the detail experimental data were presented. The crosswind effect on small cooling tower is different from the conventional big cooling towers. With the increase of the crosswind speed, the overall cooling performance of the small NDDCT first decreases and then increases. The mixed convection theory and the Richardson Number were proposed to explain this phenomenon. On the other hand, repeated cold inflow events were observed during the tests, which cause a significant decrease of the air temperature inside the cooling tower. The water outlet temperature can be increased up to 3°C as a result of the cold inflow effect. Further analysis of the mechanism shows that the cold air incursion at the top of the cooling tower could decrease the driving force and also form an extra flow resistance for the airflow through the heat exchanger.(4) Based on the working mechanism of the air-cooled heat exchanger and the crosswind effect on NDDCT, this study proposed a new method to increase the cooling performance of NDDCT under crosswind conditions by optimizing the water mass flow rate in the air-cooled heat exchangers. By optimising the water distribution, the water outlet temperature of each heat exchanger is more uniform and the adversely influence of the crosswind can be effectively relieved.The findings in this paper can lay an important foundation for future small cooling tower design and operation.

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Experimental research of the cross walls effect on the thermal performance of wet cooling towers under crosswind conditions

Cited by 51 publications

References 20 publications

Heat Transfer Enhancement of the Air-Cooling Tower with Rotating Wind Deflectors under Crosswind Conditions

Heat Transfer Enhancement of the Air-Cooling Tower with Rotating Wind Deflectors under Crosswind Conditions

Small natural draft dry cooling towers for renewable power plants

Numerical and experimental study of small natural draft dry cooling tower for concentrating solar thermal power plant

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