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how to calculate quantity of hot air to wipe off water
Last Post 03 Mar 2013 09:03 PM by Surender Thakur. 3 Replies.
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Surender Thakur
New Member
New Member
Posts:6

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28 Feb 2013 07:11 PM
    how to calculate quantity of hot air to wipe off water over a running strip (In strip processing line?

    Actually i have to calculate the capacity of a centrifugal blower in terms of flow and pressure required for a dryer which is to be used to dry strip running at some certain speed. The air from blower is to be heated up with the help of a Heat Exchanger (using steam).

    Let us consider the strip is 1mm thk X 1250mm wide and running at 25 Meters per Minute (MPM). Considering blower is distant at 10 meter away with a height difference of 5 Meter from the dryer body. That Means air is to be delivered up to dryer by means of ducts.

    The dryer body dimensions is to be calculated. Please help for the same or provide some useful links.


    Thanks in advance

    Surender Thakur
    Surender Thakur
    New Member
    New Member
    Posts:6

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    28 Feb 2013 07:29 PM
    Actually i have tried this as below :-

    Weight of water over strip (1250mm Wide X 1000 mm long (taking unit length for calculations) X 0.1mm thk of water over strip) = (1.25*1*0.0001*1000)*2 = 0.25 Kg/mtr.

    Line speed = 25 Mtr. / Min.

    Total Flow of water = 0.25 X 25 = 6.25 Kg/min. = 375 Kg/hr. = 0.375 Cub. M / Hr.

    Now,

    Flow rate (M3/hr) = 0.375
    Density @ 30 Deg C (Kg/M3) = 1000
    Specific heat (CP)(kj/kg deg k) = 4.2
    Temp. Difference (deg K) = 100-40 = 60
    Heat Load (KW) = 26.25 (By M x S x delta T)

    Here i have calculated the heat load required for the water to be wiped off but i am not sure that i am correct or not. And also does not know what to do now to have blower capacity. By using heat load we can design heat exchanger but dimensions of dryer body is still unknown to me.

    Niel
    Basic Member
    Basic Member
    Posts:193

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    02 Mar 2013 02:49 AM
    If you are blowing / wiping the water off the surface or trying to evaporate it?

    Heat will evaporate it. You can wipe it off the surface with the simple flow of air. The device in question is called an air knife.

    Companies who produce these types of products have information on the amount of air required to perform different tasks.

    Niel Leon
    engineering.com
    Surender Thakur
    New Member
    New Member
    Posts:6

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    03 Mar 2013 09:03 PM
    Sir, The running strip after this process will enter in furnace. So, if it will be having water traces, then would be leaving with marks on strip surface & will decrease the strip quality. So, the water should be wiped off and after that trail of that must be evaporated.

    You are right that the wiping is done by means of air knifes so in order to that the air exit point inside the dryer body from blower's duct would be in knife shape so as to produce both effect as it would be heated also simultaneously.

    I need the guidance towards calculation of air quantity required to produce known value of heat. like if i heat air with some known KW, how much it will produce heating effect on the next surface to be heated.
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