AT-01-08-4 -- Field Validation of a Short Time Step Model for Vertical Ground-Loop Heat Exchangers

The field validation of a short time step temperature response factor model is presented using actual operational data from an elementary school building in Lincoln, Nebr. The short time step model is used to predict hourly temperature changes of vertical ground-loop heat exchangers as used in ground-source heat pump applications. The model was based on an analytically validated numerical borehole model that simulates the heat transfer in and around the ground heat exchanger, using its thermal response to unit heat pulses. The short time step model was cast as a modular component and used to simulate the thermal behavior of the borefield using the TRNSYS environment. In order to assess the potential influence of errors associated with predicted temperatures, a series of sensitivity analyses are also presented. The sensitivity analyses focus on the impact of the heat pump entering fluid temperature on the system energy consumption, since the uncertainty in the predicted temperature is expected to have a corresponding uncertainty in the system energy use. System energy consumption, based on predicted and measured heat pump entering fluid temperatures, is compared and discussed.

Units: Dual