5 replies to this topic

[mhamdi khaled]

Dear all,

 

The depressurization in a condenser of turbo-generator is created only by the decreasing of the fluid volume or it is achieved also with the ejector ? 

[Pilesar]

In general, a condensing exchanger changes the phase of a stream from vapor to liquid and the liquid is removed from the system. Because the equipment volume remains the same, more vapor is pushed toward the condenser to fill the volume. The bubble point pressure of the liquid is the lower limit of the total vapor pressure in the condenser. Any uncondensed vapor in the system takes up some of the total vapor pressure. Also, hydraulic pressure losses in the transport lines and within the equipment can be significant. Because the liquid being removed from the system does not also carry much uncondensed vapor, noncondensible components have a tendency to accumulate and make the condenser ineffective unless these components are removed. Ejectors are often used after condensing exchangers to remove the components that were not condensed to keep them from accumulating in the system. If you have a specific question about the equipment you are looking at, you may want to provide additional description and clarification.

[fallah]

 

The depressurization in a condenser of turbo-generator is created only by the decreasing of the fluid volume or it is achieved also with the ejector ? 

 

Hi mhamdi,

 

It is mostly created by ejectors while in parallel can remove any noncondensable gases remained after low pressure steam condensation...

[Saml]

If you had perfect vacuum to start, zero air leak and steaw was ultrapure without any molecule of non condensibles (an ideal case, akin to a 100% isentropic efficiency)  then you would not need an ejector. Only the water temperature of the condenser would produce the vacuum.

 

You need the ejectors to remove the non condensibles the enter the system mainly from air leaks and small amounts in steam. The majority of the volume is removed by condensation. A small fraction that includes what cannot be condensed is removed by the ejectors.

 

You cannot pull vacuum lower than the condensing temperature, that is governed by the CW temperature and the condenser approach.

[fallah]

"The depressurization in a condenser of turbo-generator" mentioned by OP mostly implies thinking about the provision of start up conditions during which the ejector should be getting started to establish the required vacuum and then to maintain such vacuum in the normal operation; the matter which was mostly the basis of my previous post.

 

It's obvious after start up, the function of the operating ejectors would be mostly limited to non condensible gases removal to maintain the created vacuum otherwise the steam condensing action can even maintain the vacuum as long as there are not excessive non condensible gases present.

[mhamdi khaled]

Hi,

 

thank you all for the explanation and the important informations