COMMON-LINE CALORIMETRY OF A TWO-BRANCH SOLAR RADIANT FLOOR: WHY SYSTEM ENERGY IS ROBUST AND BRANCH ENERGY IS NOT

Abstract

Abstract. In many laboratory radiant-floor rigs a single flowmeter serves several parallel floor circuits. We show, for a solar-driven rig with a conventional and a PCM-integrated branch, how this hydraulic arrangement limits water-side calorimetry. Treating the unmeasured branch split  as a parameter, the system charging energy changes only between  and  for , whereas the PCM-minus-control difference changes sign at . Continuous overnight pumping turns the night into a circulating-recovery regime with  returned to the water by 06:00. System-level energy is therefore a reliable result; branch-level energy is not, unless each branch is metered.