Colloquia

Summary

Heat pumps combined with Aquifer Thermal Energy Storage (ATES) are widely used in the Netherlands to fulfil the heating, cooling and domestic hot water demands of our housing. In general, the demand for extracting heat from the ATES, caused by the hot water demand is higher than the regeneration of heat related to (passive) cooling of buildings. Dutch regulations require the ATES systems to be regenerated with heat in such an extent that there is no significant impact on the surroundings of the ATES.

Drycoolers are air-to-water heat exchangers which can be used to extract heat from the ambient air in order to regenerate the ATES or drive the heat pump’s evaporator. Since drycoolers are originally used to blow off heat rather than extract heat, there is a lack of modelling and predicting the heating capacity and outlet water temperature of these units, which defines the research gap on this topic.

This study presents a methodology to model a drycooler thermodynamically, based on fluid mechanics and standard heat transfer relations derived and validated by other researchers, in order to construct a generic model that is feasible for simulating different v-type drycooler geometries. The model generates a set of output parameters based on relevant inputs, i.e. location-specific weather data and heat pump characteristics.

The output parameters, e.g. water outlet temperature and heating capacity, are validated based on both air-side measurements and water-side monitoring of Building Management System (BMS) data, using a real case study of the present system. The model predictions are in good agreement with both the air- and water-side measurements.

The model can be used to predict the capacity of drycooler systems and obtain insights on the effectiveness and performance of different setups and geometries, but also to select drycoolers for future ATES heat pump systems and predict the overall system performance.