Characterizing the performance of alternative evaporative cooling pad media in thermal environmental control applications

Liao, Chung‐Min; Singh, Sher; Wang, Tin Sen

doi:10.1080/10934529809376795

Cited by 48 publications

(49 citation statements)

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“…Many researchers showed characteristics of various types of evaporative cooling pads in their works (Dagtekin et al, 2009;Setekleiv et al, 2008;Dai and Sumathy, 2002;Liao et al, 1998;Simmons and Lott, 1996;Koca et al, 1991;Dowdy et al, 1986). Soponpongpipat and Kositchaimongkol (2011) studied saturation efficiency and pressure drop across wetted pad of recycled High-Density Polyethylene (HDPE) and rice husk as a wetted pad in evaporative cooling system.…”

Section: Wwwgjournalsorgmentioning

confidence: 99%

Review on Evaporative Cooling Systems

Okafor¹

2017

GJSETR

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Section: Wwwgjournalsorgmentioning

confidence: 99%

Review on Evaporative Cooling Systems

Okafor¹

2017

GJSETR

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“…Dowdy et al [13,14] experimentally determined the heat and mass transfer coefficients in aspen media and rigid impregnated cellulose media. Liao et al [15,16] carried out the same analyses for fine and coarse fabric PVC sponge media, nonwoven fabric and coir fiber media. A comprehensive experimental study of cellulose pads was carried out by Malli et al [17] to investigate the effects of medium type, medium thickness and air velocity on evaporative cooling performance (including pressure drop, humidity variation, evaporated water and cooling efficiency).…”

Section: Introductionmentioning

confidence: 99%

Selection of wetted media for pre-cooling of air entering natural draft dry cooling towers

Zhang

et al. 2017

Applied Thermal Engineering

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HighlightsFour wetted media were comparatively studied for future pre-cooling design.Characteristics of wetted media suitable for pre-cooling were summarized.Media with middle efficiencies and pressure drops are superior for pre-cooling.Cellulose7060 is most promising for pre-cooling the 120m-high NDDCT. AbstractThe performance of natural draft dry cooling towers (NDDCTs) can be improved by wetted-medium evaporative pre-cooling. However, the pre-cooling benefit is season dependent and is significantly affected by wetted media. To further investigate the effect of wetted medium type on pre-cooling performance, the current study simulates a pre-cooled NDDCT using two typical types of wetted media, i.e., film (Cellulose7060 and PVC1200) and trickle (Trickle125 and Trickle100). A MATLAB program was developed and was validated against published data. The model was then used to carry out case study of a 120m-high NDDCT pre-cooled using the selected wetted media with fixed thickness of 300mm. Both the medium performance and pre-cooled NDDCT performance were compared to recommend the characteristics of wetted media promising for evaporative pre-cooling. Simulation finds that the media with high or low cooling efficiencies and pressure drops are not promising for the studied pre-cooling case while those media with middle cooling efficiencies and pressure drops intend to produce much performance enhancement and Cellulose7060 is a representative of such kind of medium. For the 120m-high NDDCT, the wetted-medium pre-cooling can raise the heat rejection rate of the tower without pre-cooling from 45MW to 92 MW, 76 MW, 68 MW and 65MW by Cellulose7060, PVC1200, Trickle125 and Trickle100, respectively at ambient temperature of 50℃ and humidity of 20%.

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“…Liao et al [13,55] used similar model as Dowdy et al's model [103,104], however, there is a slight difference. In Liao's model, the water vapour of inlet air was considered to be straightly treated to the dry-bulb temperature of the outlet air, but Liao et al still used the item X 2 (h v2 Àh wb ) to counteract the part of overestimated heat transfer.…”

Section: Mathematical Modelsmentioning

confidence: 99%

“…3a) has served as the cooling pad for quite a long time, and even now aspen pads are still on the market [60,61]. Except for aspen, the following materials have also been tried: coconut fibres [10,55,[62][63][64][65], jute fibres [9,66,67], date fibres [66,68], luffa fibres [66], palash and khus fibres [64], composite fibres [69], sheathy leaf pads [63], nonwoven fabric pads [55], cardboard and hazelnut rind pads [70], ground sponge, stem sponge and charcoal pads [9], straw pads and sliced wood pads [71] and rice husk pads [72]. (2) Rigid media…”

Section: Cooling Padsmentioning

confidence: 99%

“…Both the cooling performance and the extra pressure drop are a strong function of the wetted media, and as a consequence, it is essential to select proper wetted media for this pre-cooling enhancement. Various criteria for the selection of wetted media were suggested by many researchers [9,55,56]. A good medium should be porous enough to allow air flow and to retain water.…”

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Performance improvement of natural draft dry cooling towers using wetted-medium evaporative pre-cooling

He¹

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A cooling tower is a heat rejection device which extracts waste heat to the atmosphere. A Natural Draft Dry Cooling Tower (NDDCT) is an alternative cooling method when large quantities of water are not available. Examples of the proposed applications are the enhanced geothermal and concentrated solar thermal (CST) power plants in Australia and the rest of the world, most of which are expected to be constructed in dry climates. Unfortunately, the performance of a NDDCT is severely reduced when the ambient air is hot, which is because the NDDCT is driven by buoyancy effect and relies solely on air to cool the working fluid.Reduced cooling tower performance lowers the efficiency of the thermal power stations they are serving. The conventional solution is to use wet cooling towers but this solution consumes large quantities of water. The present project introduces inlet air pre-cooling using wetted media, which limits water consumption only to the periods when the system is used at high ambient temperatures. However, wetted-medium cooling introduces extra pressure drop which reduces the air flow passing through the tower and thus impairs the tower heat rejection. To this end, this project takes into account the trade-off between the wettedmedium cooling and the extra pressure drop, aiming to optimize the performance of a proposed NDDCT when evaporatively pre-cooled using different types of wetted media.An extensive literature review was conducted and the promising wetted media were selected for further study. Four wetted media, i.e., two film media (Cellulose7060 and PVC1200) and two trickle media (Trickle125 and Trickle100), were selected and were experimentally studied in UQ Gatton wind tunnel under different working conditions that represented NDDCT's operation. The medium performance correlations, i.e., the cooling efficiency, heat transfer coefficient and pressure drop, were obtained based on the experimental study. The test results were then used to simulate the operations of pre-cooled NDDCTs to investigate the alterations of tower performance (A MATLAB program was developed to fulfil this task).Finally, the most promising wetted medium together with its performance characteristics were recommended for future pre-cooling application.The main findings of the thesis are:(1) Choosing a suitable wetted medium for a specific application requires knowledge of different working parameters. Not only the balance between the cooling potential and the extra pressure drop, but also the consideration of medium cost, service life, type of process to be cooled, environmental conditions, water quality, space availability, locations and economic requirements are absolutely necessary, and some trade-offs have to be made.(2) The experimental studies of the four selected media found that: (a). Film media (e.g., Cellulose7060 and PVC1200) offer higher cooling efficiencies and pressure drops when compared with trickle media (e.g., Trickle125 and Trickle100). Cellulose7060 is found no water entrainment, however, care must b...

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Characterizing the performance of alternative evaporative cooling pad media in thermal environmental control applications

Cited by 48 publications

References 4 publications

Review on Evaporative Cooling Systems

Review on Evaporative Cooling Systems

Selection of wetted media for pre-cooling of air entering natural draft dry cooling towers

Performance improvement of natural draft dry cooling towers using wetted-medium evaporative pre-cooling

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