Hydraulic properties of capillary mats used for low-energy cooling and heating of buildings

Abstract

The article deals with the hydraulic behaviour of capillary mats most often used for high-temperature cooling or low-temperature heating of buildings. On the basis of experimental measurements, the dependences of the pressure loss of the capillary mats on the water flow rate in relation to their geometrical arrangement were obtained. The measured values were compared with the manufacturer's data and it was found that the measured values differ significantly. The CFD simulation method was used to model the pressure losses of the capillary mats. The main emphasis was placed on the friction losses in the capillary during laminar fluid flow and local losses during the branching and coupling of the flows for the changing flow regime. Based on the simulation calculations, the dependences of the local loss coefficient during the flow diverging and converging and the relationship for the calculation of the coefficient of friction in the unsteady region of laminar flow were obtained. Based on the obtained results, an analytical computational model was built to determine the pressure losses of the capillary mats based on an iterative and approximate solution. The example shows the differences between the different approaches to the solution. The results of the presented model are compared with the experimentally obtained data. The article presents the share of partial components in the total pressure loss of the mats.