Henrik Karlsson

Embedded Water-based Surface Heating Part 1: Hybrid 3D Numerical Model

A numerical simulation tool that assesses the transient operation of embedded water based surface heating systems is developed. Embedded surface heating systems and especially floor heating systems are, by far, the most common heat supply system in newly built residential buildings in, for example, Scandinavia and central Europe. The thermal system operation is influenced by the transient interaction between embedded elements, zones, construction elements, systems, gains, and weather. Thus, an integrated modeling principle, based on the International Building Physics Toolbox in Simulink©, is applied where the embedded surface heating model is represented by a module. The integrated tool is suitable for thermal system analysis of whole buildings. In particular, the embedded surface heating model simultaneously calculates the transient heat conduction that occurs within the embedded element, based on the finite control volume method, and the fluid temperature decline based on a local quasi steady state assumption. The numerical model, which represents a section plane of the embedded construction, is verified against a commercial 2D heat transfer software in the case of a typical floor heating application.

Embedded water-based surface heating part 2: experimental validation

The transient operation of an embedded water-based floor heating system has been studied by means of a numerical simulation tool. Prior to this study, Caccavelli and Richard (Caccavelli D, Richard P (1994) Etude portant sur le dimensionnement d’un plancher chauffant à eau chaude en CIC. Rapport n°2, n° GEC/DST-94.050R, CSTB, France.) experimentally derived reference data for the specific setup. This article constitutes an attempt to experimentally validate the numerical simulation tool that was recently developed by Karlsson (Karlsson H (2010) Embedded water-based surface heating, part 1: hybrid 3D numerical model. Journal of Building Physics 33: 357—391). The thermal response of the system is tested in both long (16 h) and short (30 min) cycle experiments where the water flow alters between on and off. Temperature distribution, within the floor construction, and the heat exchange process are studied throughout the test cycles. The model underestimates the steady-state heat exchange from the pipe loop by 16% when boundary conditions and thermal properties according to the reference case are applied. Temperatures at the floor surface are assessed with good precision while temperatures at the core of the concrete slab are underestimated by up to 1.5°C. Amplitudes, phase shifts, rise, and delay times at different measurement points are simulated with good precision. A sensitivity analysis is performed where material parameters and boundary conditions are analyzed. None of the tested parameters can independently explain the observed general trend in temperature deviations between simulations and measurements.