Comprehensive investigation on lighting and energy-saving performance of lighting/heating coupled tubular daylighting devices integrated with nanofluids

•A nanofluid-based lighting-heating coupled tubular daylighting device is developed.•The chromaticity formulas are adopted to quantize visual effects of lighting.•Energyplus is applied for daylighting and energy consumption simulation.•It’s proved that nanofluids’ filtration can hardly decrease lighting quality.•The proper nanofluids can improve total energy-saving amount by at most 43.6%.