Question Chemical, process and energy engineering

Q Compare and contrast, with the aid of drawings, where appropriate, the design characteristics of orifice plates and venturi tubes. It is desired to measure the flow-rate of a process fluid (density 1000 kg/m3) in a 100 mm internal diameter pipe. The normal operating mass flow-rate is approximately 200,000 kg/hr and the maximum anticipated flow-rate is 250,000 kg/hr. It is proposed to use an orifice plate to measure the flow-rate, but for process reasons the pressure drop across the meter must not exceed 0.15 bar.Calculate the diameter of the orifice bore to achieve this. What is a reasonable figure for the minimum flow-rate that can be measured with this orifice plate installed? Based on your knowledge of the operating characteristics of orifice plates and venturi tubes in the measurement of flow-rate, suggest an alternative use (apart from the measurement of flow-rate) for each it. Describe the measuring principle used in the operation of electromagnetic flow- meters and vortex-shedding flow- meters. What applications are these types of instruments suitable for, and why? The measurement of flow-rate in an open channel can be determined using a rectangular notch (weir), and applying the 'Francis' formula

If Q represents the volumetric flow-rate (m3/s), what do the letters B, n and D represent? Water flows in an open channel, across a rectangular weir, which occupies the full width of the channel. The width of the weir is 0.5 m and the height of water flowing over the weir is 100 mm. Calculate the volumetric flow-rate m3/s.What would be the height of the water flowing over the weir if the water flow-rate was increased to 0.04 m3/s? Specify an instrument, which is to be installed in a fully automated plant, which is suitable for measuring the following, noting that differential pressure devices are not allowed, and in each case list the instruments features and benefits (i) Fruit juice at a flow-rate of 20m3/hour (ii) Carbon dioxide at a temperature of 50˚C, and a flow-rate of 40m3/hour (iii) Steam at 2 barg in a 25 mm ID tube (iv) Ultra pure water at a flow-rate of 180m3/hour (v) Suspensions at a flow-rate of 36m3/hour. Describe the measuring principle used in the instrument specified to measure the flow-rate of ultra pure water above. Flow switches can be used to detect the flow of liquid, describe three different devices that can be used for this purpose. In each case outline their advantages and disadvantages, their principle of operation, their typical use and point of installation. Do not include devices used downstream of bursting discs.