CFD CFD modelling EnergyPlus GAHE History of engineering & technology adsorption air-side Nusselt number borehole heat exchangers buildings chiller cooling technology distributed temperature response test dual source heat pump empirical heat transfer equation energy saving for HVAC exergy transfer performance experimental results g-Function graphene nanoparticles ground coupled heat pumps ground heat exchanger ground source heat pump ground-to-air heat exchangers grouting material heat exchanger heat pump heat pumps hydration heat release marine seawater source models for calculating the thermal efficiency of ground-to-air heat exchangers