Design and Performance of a Constant Temperature and Humidity Air-Conditioning System Driven by a Ground Source Heat Pump in Summer

A constant temperature and humidity air-conditioning system driven by a ground source heat pump was designed and constructed in an archives building in Shanghai. The system consists of a water-to-water heat pump and 280 boreholes with 80 m in depth. During the operation in summer, the heat extraction from the condenser of the heat pump was divided: Part was rejected to the soil, while another was used to reheat the air in air handling units (AHUs). According to the experimental results under a typical summer weather condition of Shanghai, the average coefficient of performance of the heat pump was 5.4. The average indoor temperature and relative humidity of the archives house were $22.8°C$ and 46.6%, respectively. Since part of the heat extraction from the condenser was used to reheat the air in AHUs, the heat rejected to the soil was reduced by 23%, which was helpful for the earth energy conservation. According to the theoretical analysis, the distance between two boreholes is suggested to be 4–5 m. The deepness of the boreholes is suggested to be 80–100 m in Shanghai.