I think the attached paper will help you.

Hello

When you inject a pulse to a gas-solid fluidized bed at first pressure increases and bubble starts to form. at this point pressure decreases until the injection is stopped. When the bubble is passing through the bed pressure at the orifice reaches the previous condition. So pressure can not be fixed during injection.

If you want to have a constant volume flow rate, I think you should better use a controller and adjust it to open the valve of the orifice for a specific time. (use a mass flow meter to adjust the flow rate)

Hi Nimvari

Thanks for your suggestion. I am still not completely clear. Please see the attachment .JPEG for the air flow arrangement to the fluidized bed. (Primary air supply in blue colour, secondary air supply to the central jet in red colour).

I am setting a particular flow rate and pressure in the single jet line using flow meters and pressure regulator. But as soon as the bubble is injected when timer is ON, the volume of pressurized air present in the hose between the throttle valve and the solenoid valve gets injected into the bed irrespective of whatever flow rate I set at the upstream. 

It will be same for every pulse of gas bubble injected. I can only achieve constant flow rate when I inject a continuous stream of bubbles through orifice.

But, I need to focus my attention only on the behaviour of individual single bubble from the orifice to the bed surface. Inorder to know the jet velocity at which I am injecting the bubble, I need to apply the conservation of mass flow rate equation which require the volume flow rate of air supplied. Can I still consider the same volume flow rate that I set in the flowmeter? Instead, should I calculate flow rate based on the fixed air volume in the hose and the injection time?

Any help for anyone in this regard will be appreciated?

Hi Md. Islam,

Thanks for your reply too. I studied these papers but the fundamental calculation of jet velocity which requires the air flow rate and the pressure is still unclear as these properties keep changing with bubble pulse.

Please share your thoughts on this.  

Hi Panangipalli 

You should use two different flow meters separately. One for injection and another for fluidizing. I don't know how your flow meters are arranged.

See the attached file.

Hi Nimvari

Thanks once again. I am using same flow meters essentially for both injection and fluidizing studies but both air lines can be operable separately using control valves.

I mean to say I will do experiments following these steps:

(1) Pass air through flowmeters for fluidizing the bed. And find out the flowrate for minimum fluidization. 

(2) Maintain the bed now at minimum fluidization flow rate by visual observation. (So, here, fluidizing air will by pass the flowmeters).

(3) Now, pass the air for bubble injection through flowmeters at multiples of minimum fluidization flow rate.

Is that make sense or should I use separate flow meters still? Will this arrangement make any difference in the bubble injection flow rate and pressure?

Please anyone respond to this as early as they can as it will be greatly helpful in my research.

Thanks

Vishwanath