Abstract
Using circulating groundwater to cool air-conditioning is not new in high latitude regions but difficult in subtropical areas. Different from only using fans to remove the heat from indoor air for drier air in the high latitude region, the latent heat inside the humid air in subtropical areas makes the operation more difficult. Latent heat inside the humid air must remove away by air-conditioning including compressor and fan for cooling indoor air, which means more electrical power is required for the operation. To save total electrical power for the air-conditioning system is the main goal of this study. To use the advantage of groundwater with lower temperature to lower down the work of compressor, this research compared two ways, close/open types of water/groundwater circulation, both using groundwater to remove the heat generated by a 15RT (45 kW) air-conditioning. Full-scale tests and simulations were performed in this study to evaluate the efficiency of transferring the heat produced by air-conditioning systems to stably flowing groundwater in a grave stratum under Taipei Basin. With a closed circulating cooling water system, this study found that a 15RT air conditioner could only operate continuously for 4 h before it had to be shut down due to overheating. Additionally, groundwater must carry the heat away within the following 20 h. In changing the closed circulating water system to an open one, a system that uses a circulatory method to extract groundwater upwards and conduct heat exchange with an air conditioning system can enable the continuous operation of such a system with the same heat production condition. Numerical simulations for the heat dissipation behavior of two circulatory systems were performed herein. The results verified the aforementioned phenomena observed from both tests. The result showed both systems can provide air-conditioning working well. The total electrical power for a 15RT air-conditioning in sub-tropical areas can be reduced by 22% using circulating groundwater. Considering the system optimization, the total power consumption can be reduced by about 28%.
Highlights
Due to its basin topography, the metropolitan area of Taipei must rely on air conditioning systems to reduce indoor temperatures to a comfortable level
Calculations based on experiment results suggest that if cooling tower relative to the conver servation, a decrease in circulating groundwater aflow rate would occur, elevation of the air conditioner is at an equivalent height to the lift head of the pump creasing cooling water temperature, which is disadvantageous to energyofconserva the proposed method, the approach adopted by this study would conserve more energy
Even if different models of heat exchangers are used, the plate heat exchanger + circulating groundwater well can save more than 98.1% (=1 – 56,672 × 1.34/4,171,510) of installation space compared with cooling tower, meaning about 8.7% (=1 − 9.35/10.24) of electricity can be saved after system optimization
Summary
Due to its basin topography, the metropolitan area of Taipei must rely on air conditioning systems to reduce indoor temperatures to a comfortable level. Sustainability 2022, 14, 364 airflow within basins, cooling tower operation can prompt the surrounding air to quickly reach dynamic heat saturation This rapidly increases temperature and reduces the heat dissipation efficiency of cooling towers. The relatively large temperature difference can be leveraged to achieve cooling without the flow of groundwater because the temperatures of strata are sufficiently low Many urban such as Taipei city in Taiwan are located between subtropical and tropical zones that have relatively high temperatures and humidity during summer. Taipei Basin contains about 85 billion tons of groundwater [15] This water has a low temperature of 24–28 ◦ C [16] and could be harnessed to replace the recycling water of cooling towers for the original central air conditioning systems. To evaluate the feasibility of using circulating groundwater to cool air-conditioning and the behavior of dissipated heat carried by groundwater in a gravel aquifer, this study performed a series of numerical simulations and full-scale experiments
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