Temperature Based Determination of Volume Flow Rates in Pipes as a Low-Cost Option for Energy Measurements of Solar Thermal Systems
Abstract
The aim of the scientific investigations presented here is the development of a new method for cost effective determination of volume flow rates in pipes, which can be used for energy measurement of solar thermal systems. The main advantage of this approach is that relatively expensive measurement technology for determining volume flows can be dispensed with. This newly developed method analyses the course of temperature propagation delay between two temperature profiles, when volume flow occurs in the hydraulic loop considered. This is achieved by installing a measurement track with two temperature sensors placed at a known distance apart in the hydraulic loops associated with the thermal system. Once the volume flow in each loop of the thermal solar system (i.e. solar collector loop, auxiliary loop, heating loop, domestic tap water) is determined by analyzing the temperature profiles recorded at the temperature sensors in the measurement track, the heat quantities associated with the corresponding loop could also be determined. With respect to the volume flows determined, the newly developed method achieves an accuracy of approx. ±10 %. When it comes to small solar thermal systems, conventional heat meters are expensive, especially considering the total cost of the thermal plant. The measurement principle for the determination of heat quantities using the newly developed temperature-based method for the determination of the flow rated is very robust and cheap, Hence the it can be easily integrated into the hydraulic loops of the thermal systems and now, failures and yield reductions can be detected and suitable measures can be taken. Thus, it is e. g. also possible to determine the useful solar heat supplied to the domestic hot water systems. This can create the prerequisite for yield-oriented promotion, especially for relatively small solar thermal systems.