Document ID: chunk:federal_register_of_legislation:F2023L01530:body:0:p45
Version: federal_register_of_legislation:F2023L01530
Segment Type: other
Provision Reference: 
Character Range: 126731–129262

+ 0.75 x P0' + 0.5789
         Mo = ρo' x VCHSS
         The final mass of hydrogen in the storage system, Mf, at the end of the time interval, Δt, is calculated as follows:
         Pf' = Pf x 288 / (273 + Tf)
         ρf' = –0.0027 x (Pf')2 + 0.75 x Pf' + 0.5789
         Mf = ρf' x VCHSS
         where Pf is the measured final pressure (MPa) at the end of the time interval, and Tf is the measured final temperature (°C).
         The average hydrogen flow rate over the time interval (that shall be less than the criteria in paragraph 7.2.1.) is therefore
         VH2 = (Mf-Mo) / Δt x 22.41 / 2.016 x (Ptarget /Po)
         where VH2 is the average volumetric flow rate (NL/min) over the time interval and the term (Ptarget /Po) is used to compensate for differences between the measured initial pressure, Po, and the targeted fill pressure Ptarget.
         1.2. Post-crash leak test: Compressed hydrogen storage system filled with compressed helium
         The helium gas pressure, P0 (MPa), and temperature T0 (°C), are measured immediately before the impact and then at a predetermined time interval after the impact. The time interval, Δt, starts when the vehicle comes to rest after the impact and continues for at least 60 minutes. The time interval, Δt, shall be increased if necessary in order to accommodate measurement accuracy for a storage system with a large volume operating up to 70MPa; in that case, Δt is calculated from the following equation:
         Δt = VCHSS x NWP /1,000 x ((-0.028 x NWP +5.5) x Rs – 0.3) – 2.6 x Rs
         where Rs = Ps / NWP, Ps is the pressure range of the pressure sensor (MPa), NWP is the Nominal Working Pressure (MPa), VCHSS is the volume of the compressed storage system (L), and Δt is the time interval (min). If the value of Δt is less than 60 minutes, Δt is set to 60 minutes.
         The initial mass of helium in the storage system is calculated as follows:
         Po' = Po x 288 / (273 + T0)
         ρo' = –0.0043 x (P0')2 + 1.53 x P0' + 1.49
         Mo = ρo' x VCHSS
         The final mass of helium in the storage system, Mf, at the end of the time interval, Δt, is calculated as follows:
         Pf' = Pf x 288 / (273 + Tf)
         ρf' = –0.0043 x (Pf')2 + 1.53 x Pf' + 1.49
         Mf = ρf' x VCHSS
         where Pf is the measured final pressure (MPa) at the end of the time interval, and Tf is the measured final temperature (°C).
         The average helium flow rate over the time interval is therefore
         VHe = (Mf-Mo) / Δt x 22.41 / 4.003 x