tailieunhanh - Handbook of Water and Wastewater Treatment Plant Operations - Chapter 9

Lưu lượng đo lường điều chỉnh. Đo lưu lượng chính xác là một yếu tố quan trọng trong bất kỳ nỗ lực để xác định, chính xác, và ngăn ngừa các vấn đề hoạt động. Vì vậy, điều quan trọng là các nhà khai thác được giao nhiệm vụ vận hành nhà máy hiệu quả tối ưu. Trong chương này, chúng tôi một thời gian ngắn thảo luận về phương pháp đo dòng chảy, nhiều người trong số các tính toán được sử dụng để xác định dòng chảy, và các vấn đề đo lưu lượng khác nhau. . | 9 Flow Measurement Water is the best of all things. Pindar C. 522-C. 438 Olympian Odes Flow is cannot afford not to the competitive environment dictates that one does not have the luxury of producing wastefully. Someone is always watching if not the plant manager then the vice-president of finance if not the plant neighbors then the EPA and of course there are laws of physics to keep everyone INTRODUCTION Flow is one of the most difficult variables to measure accurately. If we wanted to use an approximate but very simple method to determine open channel discharge we would measure the velocity of a floating object moving in a straight uniform reach of the channel. If we know the cross-sectional geometry of the channel and the depth of flow is determined we can compute the flow area. From the relationship Q A X V we can estimate the discharge Q. The average velocity of flow in a reach is approximated by timing the passage of the floating object along a measured length of channel. While it is a useful way to obtain a ballpark estimate for the flow rate as part of a preliminary field study this technique is not suitable for routine measurements required in water and wastewater treatment plant operations. Another simple but impractical method of determining flow is the weight per unit time method. This method assumes a basic premise of fluid mechanics mass is a conserved quantity. Simply the mass entering a system is equal to the mass leaving the system when both are measured over the same time interval. Using the weight per unit time method to measure flow requires catching the flow in a container and weighing it over a given interval of time. The impracticality of using this method in water and wastewater operations can be seen in closed-loop processes commonly associated with chemical applications. Consequently other methods must be used to obtain flow measurements. Any seasoned water and wastewater operator knows that