Turn-down ratios

Hot water basins are used to distribute water in crossflow towers. Here, water is pumped to an open pan over the wet deck fill. The bottom of the pan has holes through which water is distributed. Manufacturers will fit specially shaped plastic drip orifices into the holes to give the water an umbrella shape for more uniform distribution. Different size orifices are used for different flow rates. Ideally, the basin will be almost full at maximum flow. This way, sufficient depth is retained for good water distribution as turn down occurs. The turn down ratio can be extended by the addition of hot water basin weirs- a pattern of baffles perhaps 2... 

Turn-down ratio The lowest percentage of capacity at which a fluid flow device can be set in order to obtain suitable design flow conditions. 

Summary. Sieve plates are the cheapest and are satisfactory for most applications. Valve plates should be considered if the specified turn-down ratio cannot be met with sieve plates. Bubble-caps should only be used where very low vapour (gas) rates have to be handled and a positive liquid seal is essential at all flow-rates. 

Calculate the maximum and minimum vapour and liquid flow-rates, for the turn down ratio required. 

Legislative restrictions on pollutant emissions have motivated the combustion community to seek new low-emission combustion techniques that are practical industrial energy sources. However, to meet the needs in most industrial applications, a combustion source needs to be able to maintain low-emission output over a range of heat release rates, occupy minimal volume, and have low operating costs per unit energy produced. One would like to maximize the turn-down ratio, volumetric heat release, and overall thermal efficiency while minimizing NOa , CO, and hydrocarbon emission levels. The ultra-low NO, emission performance of the CSC has been previously documented by the authors and its... 

Due to strict environmental regulations, turbine engine manufacturers and users are facing great challenges in reducing NO, SO , CO, and hydrocarbons to meet the compliance limits. To date, several innovative methods have been developed and introduced into the market to combat these problems. However, often, while reducing NOj, or other pollutants, new problems arise. These problems are lower turn-down ratio, poor thermal efficiency, flame instability, uneven temperature distribution in the combustor, and noise. These problems are even more pronounced in a liquid fuel fired turbine combustor. Therefore, the present research... 

To increase the turn-down ratio while producing low levels of emissions. 

Stable operating range). Some flexibility will always be required in an operating plant to allow for changes in production rate, and to cover start-up and shut-down conditions. The ratio of the highest to the lowest flow rates is often referred to as the turn-down ratio. Bubble-cap plates have a positive liquid seal and can therefore operate efficiently at very low vapour rates. 

The maximum turn-down ratio for an operating system is three-to-one. Operation in an on-off mode can also be employed to effectively increase this ratio. Another approach is the use of modular units. However, this latter option will increase capital costs considerably. 

Phosgene generation is automatically controlled by the downstream demand, with a turn-down ratio of 15 1 (production range of 40-600 kg h ). 

Because of extremes in gas volume processed (turn-down ratio), the desige basis in (his case represents only half (be anticipated peak volume. A second distillation plant will be required. With membraues, however, additional membrane capecity at the from end can be added as needed withom additional equipment required in (he distillation section. Aanlyses of sevami associated ges forecasts indicate the exit ges from lhe first stage of membranes lo be remarkably stable in composition and flow rate. This flexibility is not shown in a single case economic comparison,"... 

Energy balance thermal mass meters require one heating element located between two temperature sensors as illustrated in Figure 4.21 [24]. Although several design variations exist, their operation is basically similar. As the fluid flows past the heating element, it absorbs heat. This heat is carried downstream where it is transferred to the downstream temperature sensor. The temperature difference between the upstream and downstream sensor is detected. This output signal is then converted into a mass flow rate. These meters typically have a turn down ratio of 10 1 while the constant temperature and constant power meters have a turndown ratio of 1000 1 and 100 1, respectively. 

Turn Down Ratio - The ratio of a boiler s or gasifier s maximum output to its minimum output. 

A valve tray is shown in figure 6.12. Each hole contains a valve and the extent of opening varies with the vapour flowrate. Thus these trays can be operated over a wider range of flowrates than sieve trays of a similar size. They are said to have a high turn-down ratio which means that they can be operated at a small fraction of design capacity. A figure of 10 1 has been quoted for valve trays, while the turn-down ratio of sieve trays is less than 4 1. 

The turn-down ratio and/or the cut size of a hydrocyclone can be altered by changing the size of the inlet. Some small-diameter cyclones are available... 

Highly scalable operation with turn-down ratio of 95%... 

Cooper reported on development work by the former dbb Company aimed at developing a methanol-fiielled bus [581]. Two NECAR 3 fuel processors switched in parallel were coupled to six Ballard Mark 7 stacks resulting in 100 kW of net continuous power. A turn down ratio of 8 1 could be achieved. A two stage air compressor with heat and pressure energy recovery was used as the air supply. 

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