Tham khảo tài liệu 'industrial ventilation episode 7', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | UFC 3-410-04N 25 October 2004 Figure 8-1. Ventilation system for battery maintenance facilities. Where C Hydrogen generated in cubic feet per hour cfh . FC Float current per 100 ampere-hour. FC varies with battery types battery condition and electrolyte temperature. It will double halve for each 15 degrees F 8 degrees C rise fall in electrolyte temperature. AH Ampere hour. K A constant of cubic feet of hydrogen per 1 ampere-hour per cell at sea level and 77 degrees F ambient temperature . N Number of battery cells. 8-2 UFC 3-410-04N 25 October 2004 Q Minimum required ventilation airflow rate in cubic feet per minute cfm . PC Percent concentration of hydrogen allowed in room PC to keep the hydrogen concentration at 1 percent . Formula 2 assumes complete mixing of the air inside the battery maintenance facility. In most cases use a safety factor k to determine the actual ventilation rate. See Figure of the ACGIH IV Manual to select a k value. Qa Q x k 3 Qa The actual volumetric ventilation rate in cubic feet per minute cfm which can be expressed in air change per hour ACH using the following formula ACH Qa x 60 Room Volume 4 Example. Per manufacturer specification one fully charged lead calcium cell at 77 degrees F 25 degrees C will pass amperes of charging current for every 100 ampere-hour cell capacity measured at the 8-hour rate when subject to an equalizing potential of volts. Calculate the required rate of ventilation for a battery bank consisting of 182 cells. Each cell has a nominal 1 360-amphere hours capacity at the 8hour rate and being equalized at an electrolyte temperature of 92 degrees F 30 degrees C . At 92 degrees F 30 degrees C FC is doubled FC amp x 2 amp AH 1360 amp hr ft3 amp hr cell amp - x 13 60 amp hr 100 amp hr ft3 x ---------- x 182 cell 19 amp hr cell hr ft3 ft3 1 hr 19 x 3 hr 60 min 32 ft min 5 Assume a room size of 8 000 cubic feet cubic meters with a safety factor of k 2 .