Energy modelling of a new co-current coaxial earth - water to air- heat exchanger. Case study: Heating of house in Biskra - Algeria

Earth to air heat exchangers are preconditioning systems designed to preheat the new air of buildings in winter. This paper suggests a study of a new horizontal coaxial earth /water/air heat exchanger (EWAHE) where hot water flows in the centre of the exchanger. After an analytical study of the exchanger in steady state regime, its coupling with the surrounding earth modeled in transient regime by spatio-temporal discretization; we obtain a very good correlation of our model under MATLAB with an equivalent three-dimensional CFD model. A parametric study, shows the influence of the ratio of inner diameter/ outer diameter, thermal conductivity of the inner tube and air flow rate/ water flow rate ratio on the energy efficiency of the system. Lastly, a case study of heating a building under Trnsys in south-eastern Algerian climate proves the energy benefits of this coaxial exchanger for cooling drinking water, naturally hot, in the region and to contribute effectively to preheating the air. We ultimately show the possibility of its use in cooling mode.