Abstract
Ground thermal energy is a sustainable source that can substantially reduce our dependency on conventional fuels for heating and cooling of buildings. To exploit this source, foundation sub-structures with embedded heat exchanger pipes are employed. Diaphragm wall heat exchangers are one such form of ground heat exchangers, where part of the wall is exposed to the basement area of the building on one side, while the other side and the further depth of the wall face the surrounding ground. To assess the thermal performance of diaphragm wall heat exchangers, a model that takes the wall geometry and boundary conditions at the pipe, basement, and ground surfaces into account is required. This paper describes the development of such a model using a weighting factor approach, known as Dynamic Thermal Networks (DTN), that allows representation of the three-dimensional geometry, required boundary conditions, and heterogeneous material properties. The model is validated using data from an extended series of thermal response test measurements at two full-scale diaphragm wall heat exchanger installations in Barcelona, Spain. Validation studies are presented in terms of comparisons between the predicted and measured fluid temperatures and heat transfer rates. The model was found to predict the dynamics of thermal response over a range of operating conditions with good accuracy and using very modest computational resources.
Highlights
Exploiting sustainable sources of energy with the potential to contribute to the heating and cooling of buildings—the major contributing factor to energy consumption in developed countries [1]—is one of the major challenges of the world today, so reduction in such demands is a key element of most national emission reduction strategies
This paper describes the development of such a model using a weighting factor approach, known as Dynamic Thermal Networks (DTN), that allows representation of the three-dimensional geometry, required boundary conditions, and heterogeneous material properties
The concept of representing heat transfer as a network of nodal temperatures and resistances is extended in the Dynamic Thermal Network (DTN) approach to deal with transient conduction in heterogenous solid bodies where the heat fluxes are driven by time-varying boundary temperatures
Summary
Ida Shafagh 1, *,‡ , Simon Rees 1 , Iñigo Urra Mardaras 2 and Marina Curto Janó 3 and Merche Polo Carbayo 4. IGSHPA Research Conference, Stockholm, Sweden, 18–20 September 2018; pp. Current address: School of Civil Engineering, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, UK
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