From the actual data collected from the DWHR units at the site, the two coefficients for the NTU vs.
The temperature drop from the shower heads/faucets to the DWHR's inlet was found to be approximately 4[degrees]C (39.2[degrees]F).
The annual heat recovery by the DWHR units from TRNSYS models were calculated to be 824.9 kWh (2.8 MBtu) which showed a 4.6% difference from the experimental approach.
For this case, the annual heat recovery by the DWHR units was obtained to be 792.8 kWh (2.7 MBtu).
The annual cost savings by the evacuated tube solar thermal collector and DWHR were concluded to be $240 and $136.8, respectively.