20 September 2011

STANDING COLUMN HEAT PUMP WITHOUT BLEED IN A COLD CLIMATE


Typical cold climate houses generally require one 160 m deep vertical closed-loop heat exchanger for ground-source heat pumps. The cost of such a ground heat exchanger is relatively high. The scope of this study was to determine if standing column heat pump systems without bleed are technically and economically feasible in cold climates. Two 150 mm diameter boreholes, 25% and 60% shallower respectively than conventional vertical wells for closed-loop heat exchangers have been designed and tested. The results show that, in the heating mode without bleed, the heat pump shuts-down after 8 to 29 hours of continuous operation depending on the well depth and whether the water is withdrawn from
the top or bottom. To recover the initial temperature of the groundwater, the circulating pump has to run for at least 15 additional hours. On the other hand, system performance is high in
mechanical cooling and dehumidification mode with both standing column wells. However, the system is unable to provide dehumidification and efficient air cooling in free cooling mode.