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It was a rough sem but I throughly enjoyed it Prof! Hoping to have you as my profs for future semesters!

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Hello Prof, can I clarify that excel is banned during the finals? Even to use goal seek to find values?

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before finding distribution of fine product

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For Feed distribution of cyclone if given the distribution of Coarse product and asked to find distribution of Fine product do we use the dF/dx= Et(dfc/dx)+(1-Et)dFf/dx equation or just mass balance based on dF/dx- dFc/dx 

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For Feed distribution of cyclone if given the distribution of Coarse product and asked to find distribution of Fine product do we use the dF/dx= Et(dfc/dx)+(1-Et)dFf/dx equation or just mass balance based on dF/dx- dFc/dx 

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prof, are the pressure drop across the 1st cyclone different from the 2nd cyclone arranged in series?

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prof, are the pressure drop across the 1st cyclone different from the 2nd cyclone arranged in series?

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So the Characteristic velocity are different for the 2 cyclones arranged in series?
The EU and STK no. is different for the 2 cyclones in series right?

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Prof, do we always assume no evaporation of solvent when the qn didnt state the E? Like in tut 12 q1, we assumed E=0 & R=1

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Prof, do we always assume no evaporation of solvent when the qn didnt state the E? Like in tut 12 q1, we assumed E=0 & R=1

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Hi Prof, is there by chance you have like the softcopy of the questions from midterm on packed beds and fluidized beds? cause i want to do them for practice purposes. we only have the solutions but its hard to check the solution without the question. Thanks

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Prof, will we be required to use the Bo eqn? Primary and sec nucleation?

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Prof, will we be required to use the Bo eqn? Primary and sec nucleation?

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Prof, at Umf, do we alr actually consider the bed to be fluidized bed? or it is similar to pack bed still?

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Prof, at Umf, do we alr actually consider the bed to be fluidized bed? or it is similar to pack bed still?

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Are the cyclones arranged in series or parallel assumed to be all identical? 

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Are the cyclones arranged in series or parallel assumed to be all identical? 

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So we usually account eg Dcyc for just one cyclone in the arrangement and it will be the same for the rest?
In series arrangemnet, the Dcyc will be the same too for each and every cyclones?

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Hi Prof, how else can we prepare for Cyclone Chapter? Cause the tutorial was pretty much excel intensive, but the use of excel is not within the requirement of finals. I got still understand the tutorial but yeah just wondering if there's any other possible advice? thanks

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Prof for the last part of q3, the mean voidage we calculated is lower than the prev part when using larger particles and you wrote 'large particles expand less' but doesnt lower voidage mean that the particles take up more space so = particles expand more ?

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Hi prof, this might sound lame but can i ask if i can use pencil for the final exams. Cause your email didnt say so. Just checking cause i used pencil for finals before and got marks deducted cause prof wanted pen

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Prof, since we are not allowed to use excel, qns like tutorial 8 qn 3 unlikely to be tested?

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Hi prof, do you have extra practice qns for cyclone? Or the qn in finals will be similar to that of tutorials?

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Hi prof for the Cyclone Tutorial if I just set 2 equations- 1 for Stk50 and 1 for Eu and try to solve simultaneously for n and Dcyc I get the wrong answer. Could you please tell me why this method is wrong

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Hi prof for the Cyclone Tutorial if I just set 2 equations- 1 for Stk50 and 1 for Eu and try to solve simultaneously for n and Dcyc I get the wrong answer. Could you please tell me why this method is wrong

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prof, how to choose whether to arrange in parallel or series in a qn ? do I default choose parallel and calc like in tut?

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Prof, not sure if can ask this, but would we be tested on calculations for cyclones in series? There was no worked example so do we need to know?

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Hi Prof, may I ask when do we use the mass balance equations for solute and solvent? So far we have only used the combined equation without 𝜔2. So we only use the main equations when we have the value for 𝜔₂?

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Hi prof, can I check if we are allowed to use tablets to refer to notes??

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Hi prof, how do I know whether it is the cumulative distribution or the frequency/probability distribution? for eg in tut, they state "size distribution" and it was frequency distribution?
will cumulative have a 1 for the last number?

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seperators in series, do the Eu increase for subsequent cyclones? 
For each of these cyclones, the pressure drop is taken from the top to the bottom that cyclone only? Or does it include the pressure drop of previous cyclones above?
Also, we will need to be given the individual pressure drop, V or Dcyc to calculate the final cut size correct?

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Prof, how do we know if to arrange the cyclnes in series or parallel, is it by their volumetric flow rate ?
do we by default choose parallel?

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prof, is G(x) curve fixed for a particular type of cyclone no matter the particle sized distribution?

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Prof, will all calculations can be done using calculators(by hand), or will there be qns where excel is needed ?

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Hi prof is it possible to change the final exam timing to earlier timing on 26 April?

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Some questions on Cyclone seperators in series

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Some questions on Cyclone seperators in series

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Hi prof, for seperators in series, do the Eu increase for subsequent cyclones?
For each of these cyclones, the pressure drop is taken from the top to the bottom that cyclone only? Or does it include the pressure drop of previous cyclones above?
Also, we will need to be given the individual pressure drop, V or Dcyc to calculate the final cut size correct?

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Prof, for tutorial 12 qn2 part 2, I didn’t get it right cuz I simply used the w1c1=w2c2 +y/R to calculate. But I don’t get what this result means if it is not hydrated salt? Can you please explain what this y means here ?

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Hi Prof, regarding the additional qn u gave us during the final tutorial, so how do i go about solving this? u told us to use mass balance of solute eqn, so based on that eqn, i need to find w2 and R first is it? like how do i go about doing that?

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Prof, the Rhode book does not have the crystallization chapter so can you provide more practice questions for this chapter?

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Hi prof, how many questions total will there be for the final exam?

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I have some FAQ on CRYSTALLIZATION via email so id like to share them here:
1) how come method to find w1 in question 1 is different from question 2?
ANS:
In question 1:

When we say SOLUTION, it Is made up of 120 kg of SOLUTION = w1 kg water + (120-w1)kg of salt (NaCl)

Since we are given that the concentration c1 = 0.3899 (0.3899 kg salt will dissolve in 1 kg water)

Therefore, we know that every 1.3899kg SOLUTION will contain 1kg water, and 0.3899kg of SALT.

Therefore, by proportion, for 120kg SOLUTION, w1 = 120 * (1/1.3899) kg

In question 2:

You are given the 1000kg of salt, and that the solution concentration (saturated) is 0.838kg in every kg water.

Hence here, to calculate w1, you will use w1 =1/0838 * 1000kg

The way to calculate is always using material balance. Key is understanding the question statement.

2) Does solubility has the same meaning as concentration? Since we have assigned solubility as c1 and c2 in the questions.

Solubility is the saturation concentration at that particular temperature. We have assigned CONCENTRATION as c1 as solubility because they question defined the solution as SATURATED. (i.e. at saturation concentration)

HOPE THIS HELPS! :)

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Hi prof, may I ask if there are additional resources to practise for finals or is it just tutorials or rhodes textbook?

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Hi Prof!!

For the finals, isit all structured questions or will there be MCQ like in the quiz?

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Prof when you mentioned that MSMPR wont be tested, does this mean the crystal size distribution and the industrial crystallisers portion also will not be tested?

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hi prof will you be able to provide any questions w solutions / worked examples for nucleation?

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prof, in the excel sheet for cell M15 which calculates the pressure for 1 metre of vertical, the formula used is divided by 10. but in the homework the vertical length is 20 so we are supposed to change it to 20 right?

also, when we do goalseek for ev and f(ev), the answer changes slighlty depending on the initial assumption of ev. can we just assume ev to be 0.5?

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Hi Dr Cindy,

Will we be returned our graded hwk(s) before finals?

Thank you.

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Hi prof, could you please upload the solutions for tutorial 11?

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Hi prof just wanna clarify how you will grade us for our Uch value found using excel solver since using diff initialising values will give different values.. Is it if we use reasonable values to initialise the iteration that thats acceptable already? Thanks !

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Hi prof, is it possible to extend the deadline of HW4? There are too many submissions next week already :-(

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Hi for those who are Excel Savy, could you enlighten me on what values do i use for Excel Solver. (Max, Min, Value) .... my solver only gives me corresponding  value of Ech when Uch is 0 or 1 so how do i do the iteration???
-from a currently lost coursemate

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Hello prof, for your lecture 10 slides for the rizk equation you wrote 1400x+1.96 but in the tutorial and the textbook it was 1440x+1.96 can you clarify which is correct? Also you used d in your slides but in the tutorial and the textbook you used x to represent particle size which i found slightly confusing as d could mean diameter.

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Prof, for the Usalt, Pressure drop and gas to solid ratio can just state the answers directly from excel right? Dont need to show working?

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Equation for Choking Velocity and Alpha Clarification

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Equation for Choking Velocity and Alpha Clarification

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Hi prof,

The constants of the second equation for Choking Velocity and Alpha in the textbook is different from your slides, so could I seek your clarification on which values to use? Attached are the images for both equations for your comparison.

Martin Rhodes:
2250, 1440

Slides:
2550, 1400

(P.S. In the excel sheet, the constant used for alpha is 1440, which is using the textbook value)

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I would like to clear a doubt. If we decide to use either Ergun's or the Carman-Kozeny equation, in finding both Umf and pressure drop, we should be consistent right? (i.e use either equation throughout to find Umf and pressure drop instead of, for example, using Carman-Kozeny equation to find Umf given that Re' < 2 and then find the corresponding pressure drop using Ergun's?

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Prof, for HW4 part II, I encountered a problem when using Excel Solver. If using the Excel solver to solve simultaneous equations, the final values of U(ch) and ε(ch) will always change for different initial values. For example, if I put 1 and 0.9 for U and ε, the U will be very close to 1. But if I input 7 and 0.9, the value of U will change to 7 instead. May I know why this would happen (I have checked the formula many times, it's correct :<)

But if I don't solve the simultaneous equations, I use ε to represent U and then solve the values of ε which lead to the change of U. Then here the outputs will stabilize. So we should use this method instead?

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Prof, I initialize ech as 0.9 and Uch as 1, when i use excel solver to set the 2 equations to zero by constraining and all, it gives " not able to find a feasibl

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hi prof, for part 1d, how do you know that the same grade efficiency can be used as the previous parts despite a different distribution? is it because its the same device?

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Why are we required to find gas to solid liquid ratio first then pressure drop then U salt? I thought Usalt is needed for part i and ii... or the order doesn't matter?

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Hi Prof, can you do an announcement on LumiNUS when the submission folder is open? Thanks!

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Prof, could you explain why heat removed from the solution equals to heat lost from the solution?

Heat removed is the heat of vaporization while heat lost is the heat of crystallization + sensible heat. I get it for sensible heat = vaporization since sensible is a change of temperature and vaporization produce a cooling effect to the solvent. But why heat of crystallization is in this equation? Isn't heat loss from crystals remains in the solvent?

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Prof, is this the formula to calculate the gas to solids feeds ratio?

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Hi prof, may I check if there was an error in your lecture since you mentioned the D in this eqn is for ds but the HW4 states the D as dtube?

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Prof, can I check how we should write down the workings for the part II of the HW4 as we just simply use the excel solver? Or do we need to briefly write down the steps of how we perform the solving function?

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Hi prof, do we need to determine the gas to solids ratio, pressure drop and Usalt for both sand and catalyst, for BOTH 78 and 63mm?

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Prof, for part 2 of the HW, do we need to do for the two pipe diameters if I choose sand as the target particle or we just need to find one type of particle and do for one pipe diameter?

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Prof, may I know where we can get the F(fw)L formula? Is it same as the formula that is used to calculate F(pw)L but why don't we need to multiply by (1-voidage) if we are using the same formula?

Also, are we supposed to show one sample calculation for one of the materials?

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Hi prof, for G in this chapter, is it  solid flux instead of solid feed rate ? Or are they both the same ? As I know that for flux, it contain a m2 so its quite confusing.

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Dear Prof
is it possible if you can extend the dateline of HW 4 to 19 April 2021 as many of us have tests on week 13.

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Prof, how to find gas to solid feed ratio? Don't recall seeing it in lect notes..

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Hi Prof, is it possible to just submit the excel file for HW4?

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Hi prof, for excel solver to find Uchoke, is there any reference initializing values to use for Uch and Ech? Cos if we use different initializing values to iterate with solver we get very different answers... Just wanted to check for consistency thanks!

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Hi Prof, can I check that the U calculated in tutorial 10 is the superficial gas velocity? In this case, Usalt is the superficial gas velocity that is so slow that it causes saltation to occurs?

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Hi Prof, Pressure drop (bar) across the pneumatic conveying line includes horizontal, vertical and bend?

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Hi Prof, do we have to submit the excel file that shows the data points that we used to plot the graph?

Or we don't have to submit the excel file plus the table of data point because I used 40 data points and I think it cannot fit on a single page....

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Hi prof, we are supposed to determine either a) b) or c) for both sand and catalyst right?

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Hi Prof, when is the HW 4 deadline?

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Hi Prof, could you upload the number of marks awarded for each question in the quiz?

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Hi prof, sorry just wanted to double check:
By the definition of solids loading, the gas to solids feed ratio is its inverse right (according to units)?

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Dear Prof,
May I check how should we arrive at the ans for part (b) of this qn? I modified your excel to use their given equation for the friction factor. But, i still obtained an answer of 0.492bar instead of 0.55 bar...
Thank you

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Hello prof, is it okay if I just show one sample calculation since the procedure for all 3 beds are rather similar for all 2 air temperatures?

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Hi prof, since you stated to use the spreadsheet, do we directly state the values obtained from it (or do we need to write the working)? E.g Usalt

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Hi Prof,

Could you upload the answers for the quiz?

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Hi Prof,
are we making the same assumption of 1. U=1.5xUsalt
2. pressure for bends = 7.5x vertical pressure drop?
3. bends are 90 degree
4. properties of gas = air?
5. mass flow rate = 900kg/h?

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Hi prof, sorry to rush you but will you be releasing the solutions for the quiz and hw 4 this week?

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Dear Prof

Pneumatic calculations will not be tested for exam and only the concept of it will be tested for exam right?

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Is it just me or do some of the graphs look like straight lines even when using Ergun's? But when u do the math they are just really subtle curves. Will we get penalized if our ergun graph looks too linear?

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Prof, I wanna check on the design and operation of the reverse flow gas cyclones. In the video, you mention the high efficiency cyclone has a higher velocity and the higher rate means higher velocity as well. So may I know what exactly is the difference between these two cyclone types?

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Prof may I ask why is it necessary to plot the graph and not sketch? I have already plotted the graph on excel (only have 4 points) but I realize that it can easily be sketched too since there are no curves involved. So I would like know why is it as such. Thank you :)

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Hi prof,

I understand that if I use ck eqn or ergun eqn, the answers would be slightly different. But its okay if I choose to use ergun for the entire hw right? Would I be penalized if I use ergun for laminar region even though I know ck more accurate?

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Hi Dr Cindy,

I am a bit confused and was wondering how the drag coefficient was calculated in the excel sheet. The formula used was 18.5*Re^-0.6. I can't seem to find any formula for this; I can only find the CD equations from chapter 2 of the Rhodes textbook. Is there a page or slide that this relation is from?

Also I do not know where the formula to calculate pressure drop due to fluid-pipe friction was obtained from for the horizontal section and also the f(e) for the vertical section.

Thank you!

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HW4: Hi Prof, can you release HW4 earlier? We may need time to study for the upcoming exams, and may need to complete our assignments earlier.

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HW4: Hi Prof, can you release HW4 earlier? We may need time to study for the upcoming exams, and may need to complete our assignments earlier.

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Why do we get a different answer when solving this problem by equating the pressure drop equation for fluidized beds to the Ergun’s Eqn (as shown below)?

Is fundamentally incorrect to use this method?

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Hi prof,
is there a specific format to name the file? thank you!

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Hi prof,
Since we are required to plot ΔP for u =0 to 3umf, at some point the bed should fluidise meaning voidage will change too. can we just assume that the bed is fixed hence voidage is constant to plot the graph?

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Are we allowed to just follow the table in L9

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Hi prof, will questions like tut 10 come out in exams? i am not sure if i can solve it within 2 hours

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Hi Prof, we have to assume a voidage and L of bed to obtain the umf? Then from there calculate the flowrates?

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Prof, do we need to submit the excel file tgt with the word as most of the pressure drop calculations were done on excel?

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Prof, for HW3 part 2, do we also need to show the working for pressure drop?

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Prof, may I know how many HW left are after HW3?

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Hi Prof, how did you obtain the (UpH-UfH) in the equation for the Reynold's number? Shouldnt it just be x*UpH*pf/miu ?

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Hi Prof, can you upload the solution to Q3 for tut 9? I can't seem to get the same value when I calculate n

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Prof, is homework 3 similar to tutorial 9 qn 1?

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Prof, is homework 3 similar to tutorial 9 qn 1?

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Dear Prof,

For the Hw i can do the calculations on pen and paper right? I don't have to do the calculations on word/excel right?Then for the graph i just use excel seperately.

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Hi prof,
for my hw i wrote the workings on paper and the graphs are in excel, so would it be ok if i submit 2 separate files put into one folder (one file is pdf of my workings and another is word/excel with all my graphs)?
Or should everything be in one file?
Thank you!

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Hi Prof, I saw that the slides had S = ½DB + 1⁄8DB, which seems to be a typo.
The notes have the correlation as S = 2DB+1/8 DB instead. (I double checked with the textbook)

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Prof, hw3 is just purely using calculations and plotting of graphs right? No explanations needed?

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Prof, hw3 is just purely using calculations and plotting of graphs right? No explanations needed?