6 replies to this topic

[betty]

dear all
what is the benefit of backwash lines in heatexchangers that using water as a cooling fluid.
thanks

[ankur2061]

Betty,

Following questions before an answer can be provided:

1. What type of heat exchangers are we discussing - Shell & Tube, Plate Heat Exchangers?

2. Is there any specific application which you want to discuss since any backwash benefits or disadvantages would depend on what you want to cool in your heat exchanger and the quality of the water used as a cooling medium and / or for backwash?

Please answer the questions above before we can provide some meanigful response.

Regards,
Ankur.

[betty]

Dear,
1-Shell and tube heatexchanger

2-Crude oil industry

[ankur2061]

Dear,
1-Shell and tube heatexchanger

2-Crude oil industry

When I said application I was asking about the process fluid that you are cooling and not the industry.

Anyway the general response to your query is:

A backwash system allows the flushing of the heat exchanger of scales and deposits formed on the cooling water side. Please note that as the cooling water flows from inlet to the outlet of the heat exchanger its temperature rises. Most scales and deposits in cooling water form at elevated temperatures, which means, that the maximum scaling or deposits occur at the cooling water outlet side. A back wash system is connected at the oulet end of the cooling water from the heat exchanger. The backwash system flushes (cleans) the cooling water side from cooling water outlet towards the cooling water inlet using water which is at a higher pressure than the normal cooling water inlet pressure.

If the backwash system is designed correctly and the backwash procedure is effective there will be a definite improvement in the heat transfer coefficients on the cooling water side due to reduced fouling on the cooling water side. Ultimately you will notice that the heat exchanger is working more efficiently after a backwash then it was before the backwwash.

Hope this helps.

Regards,
Ankur.

[betty]

Thanks, so helpful...

[ashrafnew2001]

Dear,
1-Shell and tube heatexchanger

2-Crude oil industry

When I said application I was asking about the process fluid that you are cooling and not the industry.

Anyway the general response to your query is:

A backwash system allows the flushing of the heat exchanger of scales and deposits formed on the cooling water side. Please note that as the cooling water flows from inlet to the outlet of the heat exchanger its temperature rises. Most scales and deposits in cooling water form at elevated temperatures, which means, that the maximum scaling or deposits occur at the cooling water outlet side. A back wash system is connected at the oulet end of the cooling water from the heat exchanger. The backwash system flushes (cleans) the cooling water side from cooling water outlet towards the cooling water inlet using water which is at a higher pressure than the normal cooling water inlet pressure.

If the backwash system is designed correctly and the backwash procedure is effective there will be a definite improvement in the heat transfer coefficients on the cooling water side due to reduced fouling on the cooling water side. Ultimately you will notice that the heat exchanger is working more efficiently after a backwash then it was before the backwwash.

Hope this helps.

Regards,
Ankur.

Mr. Ankar you mentioned that the deposites and scales are removed by the backwash process by high pressure water from outlet side of the tube (assume that cooling water is on the tube side) will the scales and deposites accumlate on the front hear of the heat exchanger on the inlet side i mean? and what about the water that carries the deposites and scales where it will go after then?

[ankur2061]

ashrafnew2001,

Nowhere I have mentioned about 'CW' on tubeside. It could be anyside. Backwash can be tailored to suit the needs of the particular application. For example you could mix descaling chemicals with water used for backwash to effectively clean the CW side. You can install a temporary strainer (filter) at the inlet of heat exchanger before the backwash to capture all the scale and dirt. You could also disconnect the inlet CW line to the heat exchanger, and provide a temporary connection to a drain from the CW inlet connection to the HE for open flushing of the heat exchanger. Many, many ways of doing the backwash operation depending on the application and established plant operating procedures for backwash.

Regards,
Ankur.

Edited by ankur2061, 24 December 2011 - 11:46 PM.