Performance Analysis Of Standing Column Well Groundwater Heat Pump Systems

In recent years, groundwater heat pump systems that use groundwater drawn from and returned to the same well in a semi-open loop arrangement were proposed abroad, commonly known as Standing Column Well (SCW) systems. It's a promising technology with low cost, high efficiency, low energy consumption and environmental benefit. A number of authors have reported on it in America, and it has been used in the Northeast of America. However, recent researches are presented to the modeling and affections of standing column wells. No effective, reliable and detailed Design Method is proposed. Few researches were reported about this system in our country. And no research was reported about its adaptability or possibility of use in China.The model of seepage field and the model of heat transfer for standing column well are established. Finite difference method is used to discrete and solve the equations. On this condition, characteristics of seepage flow are studied to analyze the effects of circulating water flow rate, bleed rate and depth of well on the seepage flow of SCWS. And characteristics of heat transfer are studied to analyze the effects of rock thermal conductivity, rock hydraulic conductivity, bleed rate, ground-water initial temperature and etc. on the heat transfer of SCWS. And the effects of well depths on heat transfer are also analyzed to cmpare operation effects of different depths of wells, in order to find out the feasibility of using shallow SCWS.Conclusions can be drawn as follows. With more circulating water flow or higher bleed rate, SCWS have higher seepage flow rate. And the effect of circulating water flow rate is more significantly. With the increasing of mass rate of circulating water, all seepage flow rates along the borehole are increased. However, with the increasing of bleed rate, few groundwater flow in, on the base of more circulating water flowing out of the borehole. On heat transfer, the minimum well temperature in winter increases with rock thermal conductivity, hydraulic conductivity, roughness height of the borehole, borehole diameter, bleed rate, and ground-water initial temperature, and decrease with dip tube diameter. Among these affections, the effects of bleed rate and rock thermal conductivity are more significantly, while, roughness height of the borehole has little effect on heat transfer. Changing deep wells into shallow wells is feasibal, with good heat thansfer effect and low initial cost. The effect of intermittent operation is better than continuous operation.