Abstract
Cooling towers are equipment generally used to dissipate waste heat from process fluids used in petrochemical, mining, power stations and air conditioning units. They are classified based on the air and water flow pattern, structure, construction material, shape or heat transfer method. The heat transfer method is the most used factor for designing cooling towers.
The problem addressed by this study is the performance of Hybrid cooling towers in terms of energy and water consumption in comparison with separate traditional dry and wet cooling towers, as reported by Hu et al. (2018). For example, high water consumption in wet cooling towers requires constant make-up water due to evaporation. In contrast, the high energy usage in dry cooling towers generates huge electricity costs. Though a few studies were done regarding Hybrid cooling tower performance, water and energy consumption, most of them were based on simulation and modelling, as suggested by Palenzuela et al. (2022). The data from the current literature models don’t offer a better understanding of the mass flow patterns and evaporation rates without experimental validation of modelled results as noted by (Graaff et al., 2017). In addition, (Asfand et al., 2020), reported that tests must validate all theoretical analyses, and currently no CSP plants have integrated hybrid cooling system technology.
The study methodology was theoretical and experimental. First, a literature review of current hybrid cooling systems was presented to familiarise with the concept related to the research. A theoretical model was derived from existing literature equations to predict performance, energy, and water consumption. At the same time, a working prototype hybrid cooling tower was designed and built for the experimental investigation. Finally, an experiment was conducted to study the cooling tower parameters at different modes of operation. Using sensors and measuring meters, the cooling tower parameters were measured. The measured data was either logged on the data logger or read and recorded in tabulated form.
The analysed data indicated that the hybrid cooling tower performance is higher than that of dry and wet modes operating separately. The heat transfer rate of the hybrid tower was much higher than the dry and wet modes when operated at the same fan
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speed setting. This indicated that the hybrid cooling tower has a lower power consumption concerning heat transfer and power consumption ratio than the other cooling mode options. In addition, the water consumption was lower compared to the wet mode at the same power setting. The results showed that the hybrid ratio reduces water consumption significantly more than the wet mode. The experimental results indicated a 55% reduction of water consumption between hybrid ratios 0.2 and 0.8 when operating at 100% full fan speed. The findings agreed with the theoretically predicted results and conclusions of the literature.
In conclusion, the study indicated that the hybrid cooling tower performs better using less energy than the traditional separate dry and wet modes. Depending on the application and ambient conditions, the hybrid tower operated using a hybrid ratio offers lower water consumption than a separate wet cooling mode. The theoretical model will assist significantly in cooling tower selections and hybrid cooling tower performance prediction.
This study aimed to develop a theoretical model and build a prototype hybrid tower to evaluate a hybrid cooling tower's performance, water and energy consumption. The prototype hybrid tower was tested at different mass flow configurations and fan speeds to validate the theoretical model analyses and obtain accurate conclusions.