The sole reason for this is the saturated steam is the best conductor of heat and as the degree of Superheat increases, the heat transfers become inefficient. In addition, the valve is typically of the balanced type with either a balancing plug or a balanced bellows arrangement to reduce the required actuator force. This means that smaller distribution pipelines can be used provided that the pressure drop is not excessive.
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The bulk of the energy is in the enthalpy of dwsuperheater, and the energy in the superheat represents a smaller proportion. This is an important parameter, as any variation in inlet pressure, temperature or flowrate will cause a variation in the requirement of cooling liquid. This change may simply be achieved by an orifice, which has the ability to change in area see Figure Steam turndown ratios of up to 5: Multiple point radial injection spray desuperheaters This is a progression of the single point radial injection spray desuperheater.
At such speeds a number of problems would occur including the generation of shock waves.
First for Steam Solutions. Any evaporated cooling water passes through the floating head and will accumulate in the outlet side of the shell. You may be trying to access this site from a secured browser on the server. The simplest type of desuperheater is an unlagged section of pipe, where desulerheater can be radiated to the environment.
A typical direct contact desuperheating station is shown in Figure Radial injection type desuperheaters have the advantage that they can be easily combined edsuperheater the pressure reducing valve to produce a single unit. Good turndown — steam turndown of up to This is referred to as the absorption length.
The cooling water injection into the steam will continue till the temperature falls to saturation. The unit usually employs a thermal sleeve.
This tutorial introduces the common types of desuperheater in regular use, their limitations and typical applications. This desuperhetaer is limited by a travel stop incorporated into the top of the cage.
Consequently, the water level will fall and therefore provision must be made to maintain this level. The desuperheating aspect will also vary depending on the application, but it is common for a multiple point radial injection type to be used.
Desuperheater - Forbes Marshall - arca
Variable spray type - The downstream temperature determines the number of exposed nozzles. Steam traps for process Equipment. The desuperheating process is carried out in two separate phases:.
A typical desuperhetaer is as below Inlet Steam Press P1: There is reduced wear in the downstream pipework compared to a spray type desuperheater, as the cooling water emerges as a mist rather than as a spray. In the second stage of desuperheating, a saturated mist or fog emerges from the internal diffuser into the main diffuser where it mixes with the remainder of the steam. Application Recommendations Optimized Process Control.
News Investors Careers Contact Us. Desuperneater the superheated steam has more energy per unit mass than the saturated steam, more steam will be evaporated than actually enters the desuperheater. This greatly assists accurate sizing and control of heat transfer equipment.
The caveatis that these units must be controlled precisely to prevent flooding of the whole system.
Pages - Basic Desuperheater Types
The cooling water pressure need only be 0. It is absolutely necessary that for such applications the outlet steam temperature should be as close as possible to its saturation temperature. Changing the area of the orifice, A - Expressing flowrate as desupreheater function of the area of the orifice:.