Modeling Heat Transfer in Mass Concrete Floors with Radiant Heat from Ground Source System

Thermal properties of concrete have been extensively studied for the design of mass concrete structures regarding cracking and stress development considerations. The rise in blended cement with limestone and fly ash as a sustainable building material is one approach to reducing the exothermic release from cement and significantly reducing the greenhouse gas signature of the building materials while maintaining the technical properties needed for building design. Concrete containing limestone blended cement with limestone and fly ash have noticeably different thermal properties that are not well predicted by commercially available software. The purpose of first phase of this project is to provide thermal property data for designers or software developers. The second phase of the research demonstrates the sustainability and energy savings of a ground source system paired with a mass radiant floor constructed of concrete containing blended cement. This phase built and conducted controlled experiments on an instrumented 33,000 square foot industrial facility. The scope of second phase of this project is improving the efficiency of radiant floor in the buildings with a geothermal system. Large areas of heated slab can provide sufficient heat flux needed to maintain the indoor temperature at a comfortable level. The Cooper Laboratory features a strong floor, which is a massive concrete element that can store heat due to its large heat capacity and low thermal conductivity. Stored heat can later be released to the laboratory atmosphere through convective transfer. Using the mass heated radiant floor in the covered structures such as laboratories with large bay area with controlled condition of internal air temperature can moderate the air conditioning need at cool or warm seasons. For both parts of this project, a finite element (FE) model was applied to simulate the temperature rise due to cement hydration in the mass floor and thermal behavior of the radiant floor in different loading conditions of the piping system. The third phase of the research was to optimize the electricity used by utilizing an off-peak rate structure for the radiant heating and cooling the mass concrete floor during low cost times and use the convective transfer from the mass concrete to the air during peak rate hours with the radiant system shut off.