Experimental Study on the Heat Release Operational Characteristics of a Soil Coupled Ground Heat Exchanger with Assisted Cooling Tower

Hybrid ground source heat pump systems (HGSHPS) with assisted cooling towers is one of the most efficient cooling and heating technologies for buildings with cooling-dominated loads. For the system, the coupled heat release mode between the ground heat exchanger (GHE) and cooling tower is vital for underground soil temperature recovery characteristics and system operation performance. In order to obtain the heat release operation characteristics with different coupled modes of the GHE and cooling tower, a set of multi-functional heat release experimental systems of soil coupled GHE with assisted cooling tower was constructed. The experimental investigations on the system heat release operation characteristics operated in the separate GHE heat release mode, combination heat release mode and day and night alternate heat release mode were undertaken based on the experimental system. The results show that for the separate GHE heat release mode, the heat release rate of GHE rises rapidly during the first two hours of operation, then, gradually tends to be steady, and the soil excess temperatures at various depths gradually rise with time. For the combination heat release mode with continuous operation of cooling tower, in view of reducing soil heat accumulation and accelerating soil temperature recovery, it is more conducive to the heat release by opening the cooling tower on sunny days. For the combination heat release mode with intermittent operation of cooling tower, when the total time ratio of cooling tower running to stop is constant, the intermittent time is longer, the better the effect of soil temperature recovery. Additionally, the soil temperature recovery rate can be improved greatly by the release heat operation of cooling tower during night, and the longer the cooling tower runs, the closer the soil temperature is to the initial temperature