China
Africa
Explore chapters and articles related to this topic
Determination of Ground/Soil Effective Thermal Conductivity
Published in Vasile Minea, Heating and Cooling with Ground-Source Heat Pumps in Cold and Moderate Climates, 2022
The working principle of a thermal response test is the following: (i) the thermal response test rig is connected to the borehole heat exchanger and water will be circulated in the system (Figure 6.1); (ii) a constant heat injection is provided by a heater (electric resistance, gas, or heat pump); (iii) the thermal energy is transported with the water and introduced into the ground/soil; and (iv) from the development of the temperatures thermal conductivity can be calculated.
Vertical Closed-Loop (Indirect, Secondary Fluid) Ground-Source Heat Pump Systems
Published in Vasile Minea, Heating and Cooling with Ground-Source Heat Pumps in Cold and Moderate Climates, 2022
The main input geometrical parameters are as follows: (i) borehole radius and active length; (ii) U-tube radius, number, and wall thickness; and (iii) physical properties of the ground/soil and filling material (grout) (e.g., heat capacity, the heat conductivity, and the density), of the brine (e.g, thermal conductivity and freezing point), as well as the ground/soil annual mean temperature and the borehole resistances from thermal response test(s).
Thermal interactions in large irregular fields of geothermal boreholes: the method of equivalent boreholes
Published in Journal of Building Performance Simulation, 2021
Carlos Prieto, Massimo Cimmino
Mathematical models of heat transfer are used in all phases of GCHP system planning, design and operation. These mathematical models allow us to predict temperature changes in the fluid and the ground due to fluctuations in the heat extraction and rejection into the borefield. In site characterization applications, physical parameters (e.g. soil thermal conductivity, borehole thermal resistance) can be inferred by fitting mathematical models to measurements from a thermal response test (Spitler and Gehlin 2015). In the design phase of the system, mathematical models can be used to estimate the required borehole size to satisfy the operation parameters of the equipment, for example, lower and upper fluid temperature limits for the operation of the heat pump (Ahmadfard and Bernier 2019). Heat pump and borefield heat transfer mathematical models can be coupled to predict the energy consumption of the system. Also, these models could allow successfully posing an optimization strategy for the system design and the development of model-based control strategies (Cupeiro Figueroa, Cimmino, and Helsen 2020). Accurate predictions of fluid and ground temperatures require the modelling of both of the long-term and short-term heat transfer effects in geothermal boreholes (Li and Lai 2015). Long-term heat transfer effects are characterized by the three-dimensional heat transfer in the soil and the thermal interactions between boreholes. Short-term heat transfer effects are characterized by the transit of the fluid through the boreholes and the thermal capacitance of the borehole materials.
Application of linear superposition theory in successive thermal response tests without ground temperature recovery
Published in Science and Technology for the Built Environment, 2018
Shiyu Zhou, Wenzhi Cui, Kuan Gao
The thermal response test (TRT) is an important way to obtain the underground thermal properties for the design of a ground-source heat pump (GSHP) system. Two classical analytical solution models of a ground heat exchanger (GHE; a “line source model” and a “cylindrical source model”) are mainly used in the data processing of the TRT. The line source model is more widely used because of its simplicity (Austin et al. 2000). Linear superposition theory in TRT data processing was first proposed based on the composite line source model (Beier and Smith 2003a; Marcotte and Pasquier 2008).
Insights into parameter estimation for thermal response tests on borehole heat exchangers
Published in Science and Technology for the Built Environment, 2019
For a specific installation the design of a GSHP system requires estimates of the ground thermal properties, including the thermal conductivity. Also, the borehole thermal resistance is used in the design for the selected borehole configuration. For commercial installations a thermal response test (TRT) is often performed on a test borehole to estimate the ground thermal conductivity and borehole thermal resistance.