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  1. #51
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    Re: Exhaust Air to Warm water Heat Pump - malt kilning



    Great thread !

    Manny, any chance your chief bean counter would release some cask strength 30yo to go DHL to NZ ?




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    Re: Exhaust Air to Warm water Heat Pump - malt kilning

    Haha olddog, not even we get to sample that stuff. F**k healthcare, I want free samples!

    You want to go for a Talisker 16yo or a Clyenlish 12yo - they must have that good stuff kicking around NZ?

    I don't know what the distribution of single malt whisky is, all i know is around 90%+ gets blended and shipped off to anywhere but Scotland!

    Fridge/Pete - got some data coming in now, hopefully within a week I can give you guys concrete numbers (/range of numbers) and you could advise on possible COPs. (if you havn't lost interest already )

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    Re: Exhaust Air to Warm water Heat Pump - malt kilning

    Whats yo in 16 yo ?
    That invoice I found on the net was from 1932. At the end - must be around 1980, it was then already a very old building, ready to demolish it. But it's situated along a nice canal in Bruges...if you know Bruges of course.

    I haven't lost interest yet, far to interesting.

    Don't forget to search if funds in Scotland are give for such a projects.
    Last edited by Peter_1; 11-08-2010 at 07:03 PM.
    It's better to keep your mouth shut and give the impression that you're stupid than to open it and remove all doubt.

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    Re: Exhaust Air to Warm water Heat Pump - malt kilning

    Good morning folks, hope your week is going excellently.

    Data is coming in: soon i will know most of what i need to i think, and also i will try and upload a rough schematic of the situation.

    Getting specs for the current HX and radiators at the moment. I will keep you posted.

    Manny

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    Re: Exhaust Air to Warm water Heat Pump - malt kilning

    Looking forword to it.

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    Re: Exhaust Air to Warm water Heat Pump - malt kilning

    Fridgy/Pete,

    Thats a rough scetch of the setup attached. The dotted unit is what i reckon might be the most controllable option.

    Splitting the hot water in, and using one fractions heat to bolster the remaining flow, which is then thermally better off and that heats the glycol. If the scetch isnt clear let me know.

    Numbers to come.

    Manny
    Attached Files Attached Files

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    Re: Exhaust Air to Warm water Heat Pump - malt kilning

    Quote Originally Posted by MannyCalavera View Post
    Fridgy/Pete,

    Thats a rough scetch of the setup attached. The dotted unit is what i reckon might be the most controllable option.

    Splitting the hot water in, and using one fractions heat to bolster the remaining flow, which is then thermally better off and that heats the glycol. If the scetch isnt clear let me know.

    Numbers to come.

    Manny
    Do you want to put some numbers on the lines
    temps, flows (include the glycol)

    cheers

    mad

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    Re: Exhaust Air to Warm water Heat Pump - malt kilning

    Absolutely. This week I am going to collect the observed data and will ping that onto the diagram.

    I will include the range of flows and temperatures of streams that are relevant.


    Ta

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    Re: Exhaust Air to Warm water Heat Pump - malt kilning

    Hi manny check your calculations.
    A couple of points to assist.
    The bigger the compression ratio on a refrigeration plant the less efficient.
    The larger the number of stages of heat exchangers, the greater the original driving force has to be.
    As a "VERY" basic rule, for every 1C you drop your refrig evap temp (SST) you disadvantage the system by 3.5%, for every 1C you increase the refrig cond temp (SCT) you disadvantage the system by 3%.

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    Re: Exhaust Air to Warm water Heat Pump - malt kilning

    Fridgie, I was away to ask;

    If i did use ammonia, would i not have to compress it to 23bar for it to condense at 55 deg C? See link.

    http://webbook.nist.gov/cgi/fluid.cg...s&STUnit=N%2Fm

    I have been taught that roughly a compression ratio of around 3 is good. I.e. to get to 9 bar, want 2 compressions. 1-3, 3-9. etc. 23+ bar? That seems high to me, but i am not experienced with this. Could you have say 1-3, 3-9, 9-27, i.e. 3 stage?

    Could you elaborate on the dropping of cond/evap temperatures? I thought the evaporating temperature would be the fluids boiling point at 1atm, or can you regulate the expansion valve to control this?

    Much obliged.

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    Re: Exhaust Air to Warm water Heat Pump - malt kilning

    Quote Originally Posted by MannyCalavera View Post
    Fridgie, I was away to ask;

    If i did use ammonia, would i not have to compress it to 23bar for it to condense at 55 deg C? See link.

    http://webbook.nist.gov/cgi/fluid.cg...s&STUnit=N%2Fm

    I have been taught that roughly a compression ratio of around 3 is good. I.e. to get to 9 bar, want 2 compressions. 1-3, 3-9. etc. 23+ bar? That seems high to me, but i am not experienced with this. Could you have say 1-3, 3-9, 9-27, i.e. 3 stage?

    Could you elaborate on the dropping of cond/evap temperatures? I thought the evaporating temperature would be the fluids boiling point at 1atm, or can you regulate the expansion valve to control this?

    Much obliged.
    You pick your compression ratio to suit the process application.
    Where did 55C come from?
    Focus on the process not the heat pump
    1 What is the fresh air flow through each preheater on each kiln. (range if controlled) primary load
    2 What is the air entering temps(s) range to the kilns. primary load
    3 What is the glycol flow (total and to each pre heating coil)
    4 What is the glycol return temp (range)
    5 What would be the ideal glycol supply temp to the kiln coils (this is likely to be design variable)
    6 What is your distillary water flow third stage
    7 What is you dist. water flow temp (from)
    8 water back to dist temp, will be a function of the above energy mass balance
    9 You then need to undertake a load profile, to cover the diversity.
    10 and only after the other 9 steps have been completed do you then design/concept the heat pump (for performance, duty and control method)
    11 look into the practical aspects of the installation.
    12 re-look at 10, to see how this is effected by 11.
    Last edited by mad fridgie; 19-08-2010 at 08:01 AM.

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    Re: Exhaust Air to Warm water Heat Pump - malt kilning

    This sketch hasn't the needed figures to make a correct estimate.
    We need numbers all over the drawing.
    Gathering the basic information is your first task now. Th better you do it, the better you can calculate everything afterwards.
    Regarding your NH3 compression.
    I haven't read teh article about NH3 compression but far more important is the COP you get.
    You again forget your superheat. If you want 55°C, then you don't need to compress at 55°C, more 35°C (discharge of 100°C) or 40°C (113°C)
    Like MadFridgie explained you some posts ago - I think - can you use a lot of water at a more lower temperature or do you need higher water temperatures at a lower flow? You can't have both (high flow and temperature) But what is high flow and temperature?

    Therefore, what exactly do you need, where and how much at what temperatures.
    Again, figures are very important and I don't understand the process like you drawn it.
    And I worked some time in malt plants like you know, years ago

    Another point, selecting the refrigeration system, let it now NH3, R744 or any other refrigerant will be not that easy. You only can make rough estimate to what this will cost.
    Last edited by Peter_1; 19-08-2010 at 06:24 AM.
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    Re: Exhaust Air to Warm water Heat Pump - malt kilning

    Ok thanks folks. Some more data to get today - tomorrow i will fully annotate that diagram and upload. Hopefully with all the values and ranges of flows and variables in place you might be able to advise on step 11 as you pointed out fridge.

    I have most of 1-8 will provide this tomorrow.

    I will re-draw the setup so it doesn't look like stevie wonder drew it.

    Cheers

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    Re: Exhaust Air to Warm water Heat Pump - malt kilning

    Quote Originally Posted by MannyCalavera View Post
    Ok thanks folks. Some more data to get today - tomorrow i will fully annotate that diagram and upload. Hopefully with all the values and ranges of flows and variables in place you might be able to advise on step 11 as you pointed out fridge.

    I have most of 1-8 will provide this tomorrow.

    I will re-draw the setup so it doesn't look like stevie wonder drew it.

    Cheers
    You can not look at 11 until you have completed 10,
    remember on your drawing, to include all existing heat exchangers (how the glycol is heated now and to what temps).
    I thought a snail had crawled across the page? lol.

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    Re: Exhaust Air to Warm water Heat Pump - malt kilning

    I am a heat pump novice fridgie but that hurts.

    Hopefully get a scan in tomorrow for you guys to peruse if you got a spare minute with all info i currently have.

    Manny

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    Re: Exhaust Air to Warm water Heat Pump - malt kilning

    Right sirs,

    Find an annotated and hopefully clearer description of what i'm dealing with.

    Hard to know exact flow of air - 90,000kg/hr is a good approximation. 5-8 at any one time have 2 batches between them, 3&4 are twice capacity and therefor have 2 between them at any time also.

    Air requirement at all times, roughly 360,000kg/hr (it doesn't get much more accurate than this i am afraid). Clearly air temp is going to change alot, fuel used in winter will be much more than in summer, thats the nature of the process.

    Glycol properties given. An interesting point, what is desired air (and therefore glycol) temperature. Kilning temps range from 65 - 85 over the kiln period. This is a question of how easy it is to "regulate" the amount of heating the pump supplies. For the sake of a target, i would say preheating the glycol to 65-70 degC would be sound. (i assume this is what you meant by kiln diversity, i.e. profile).

    Hot water - yes, large fluctiation there. Nature of the batch process. However, work is being done currently to smooth this out. Average is around 250m3/hr, and hopefully with tuning the variation will drop.

    Kiln 3/4, glycol loop is just twice the capacity of glycol and PHE is twice the area.

    I guess from a control point of view, the glycol return temperature is one of the biggest variables, depending on ambient air conditions. I.e. in summer when it returns alot warmer, will it have the driving force to perform the condensation of refrigerant? That kind of thing? Glycol can generally be heated to within 2degC of the hot water temp, and returns as indicated on diagram.

    Thoughts gentlemen? Some friday afternoon reading

    Regards
    Attached Files Attached Files

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    Re: Exhaust Air to Warm water Heat Pump - malt kilning

    your present heat reocvery, is saving aprrox 2500Kws (suspect air flow is wrong or wrong TD) Number do not quite add up but close enough.
    The figures indicate, 3 out of the 6 kilns are operating in the same mode, at all times.
    Total airflow 800K to 1200KM3/hr
    Total Glycol 180M3/hr
    You should be able to get approx another 5000Kw heating with heat pump power and pumps 1100kw,
    COP of 4.5
    or
    6000Kw heating with heat pump and pumps 1875kw
    COP 3.2.
    To achieve these results it is a process/system. not just a heat pump
    Last edited by mad fridgie; 21-08-2010 at 02:39 AM.

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    Re: Exhaust Air to Warm water Heat Pump - malt kilning

    The next question before any stage of the feasability, is do you have the electrical infrastruture, for this level of increased of electrical load.

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    Re: Exhaust Air to Warm water Heat Pump - malt kilning

    Good point MF about needed power to run this, you will need +/- 600 to 700 kW electrical power to recover 2500 kW.
    Giving this, you have to make calculations/decissions if you will use NH3 and spill the absorbed power from the net (open compressors) or use semi-hermetic screws and recover also the consumed power of the net.
    It's better to keep your mouth shut and give the impression that you're stupid than to open it and remove all doubt.

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    Re: Exhaust Air to Warm water Heat Pump - malt kilning

    Quote Originally Posted by Peter_1 View Post
    Good point MF about needed power to run this, you will need +/- 600 to 700 kW electrical power to recover 2500 kW.
    Giving this, you have to make calculations/decissions if you will use NH3 and spill the absorbed power from the net (open compressors) or use semi-hermetic screws and recover also the consumed power of the net.
    Already allocated some losses into the calculation, 5000Kw addtional process energy, additional power draw for upgraded process 1100KW. Equipment selection, is not even worth looking into at this stage.

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    Re: Exhaust Air to Warm water Heat Pump - malt kilning

    Good point Fridgie,

    That is info I can get on monday. This is an important feasibility study, so even if it turns out to be uneconomical I still need to assess everything. Will reply with info on Monday.

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    Re: Exhaust Air to Warm water Heat Pump - malt kilning

    If your figures are correct, then according to my calculations, then this is very viable!
    But there is a lot more work to be done.
    I am in the UK (first 2 weeks in September) I offer my services to assist you in developing a required process. This would come at cost!
    It would 100% need a site visit.

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    Re: Exhaust Air to Warm water Heat Pump - malt kilning

    A lovely thread, lads. Apologies for my late entry - been moving countries, of late.

    I'll go back & re-read the earlier part of the thread to check - but, what kind of process uptime is to be expected from the Process Radiators (24/7?). If not 24/7, this may be something to factor into the overall scheme i.e. a modular system approach may assist.
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    Re: Exhaust Air to Warm water Heat Pump - malt kilning

    Folks,

    More numbers coming. Fridgie, unlikely funding would be provided for this "pie in the sky" I, a naive b*stard student, am working on with your guys help. Still, i shall ask .

    Greetings desA. 24/7, yep. (aside from a few weeks every summer for annual maintance of site).

    There is recicrulation of kiln air (as is convention) - i will have to suss out in my head how this effects the quantity of 'fresh' air used during this time.

    I have a few more months working here, my aim by the end is to compile a fairly sound report on the feasibility of said heat pump - and I would like it to be fairly worst-case-scenario and as realstic as possible, so that the economic feasibility will not be over stated.

    Time for me to call it a day - communix shortly.

    Manny.

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    Re: Exhaust Air to Warm water Heat Pump - malt kilning

    Quote Originally Posted by MannyCalavera View Post
    Greetings desA. 24/7, yep. (aside from a few weeks every summer for annual maintance of site).
    Ok. Good. Makes things a bit easier.

    There is recicrulation of kiln air (as is convention) - i will have to suss out in my head how this effects the quantity of 'fresh' air used during this time.
    You may want to estimate fouling factor on the air-side (kiln), as this will impact the radiator design area.
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    Re: Exhaust Air to Warm water Heat Pump - malt kilning

    "You may want to estimate fouling factor on the air-side (kiln), as this will impact the radiator design area."

    The radiator in question is a pre-heater, before main steam radiators. Fouling? Don't think this is an issue - fresh air (no sulpherous components, etc) in, glycol solution through tubes.

    It is finned - the only fouling i can think of is due to birds sh*tting all over it. (that what you meant?)

    I am in the process of finding the specs for these radiators. Currently I am not thinking about replacement of these, more focusing on boosting the glycol temperature which is the working fluid within them. So from that point of view, yes I would have to estimate their effectiveness with different operating conditions to what they were designed for.

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    Re: Exhaust Air to Warm water Heat Pump - malt kilning

    Quote Originally Posted by MannyCalavera View Post
    "You may want to estimate fouling factor on the air-side (kiln), as this will impact the radiator design area."

    The radiator in question is a pre-heater, before main steam radiators. Fouling? Don't think this is an issue - fresh air (no sulpherous components, etc) in, glycol solution through tubes.

    It is finned - the only fouling i can think of is due to birds sh*tting all over it. (that what you meant?)
    If your air is fresh feed (not re-circulated), then you should at least consider dust & general clogging of the fins - unless a pre-filter is used.

    This crud will reduce heat-transfer a fair bit & should be allowed for in your calculations/specifications.

    You may also want to consider the radiator fin material - copper, or aluminium (coated) etc.
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    Re: Exhaust Air to Warm water Heat Pump - malt kilning

    Welcome DesA, I was wondering when you were going to join in.
    To gain the efficiencies stated, there are many items that need to be studied, not just the heat pump.
    An Annual load profile needs to completed with the diversity of the kilns and the distilling process included (changes in required inputs and out puts and how they correspond to each other)
    Manny, if your figures are correct, and they seem to be, then please do not think of this as a "Pie in the Sky" project. There may well be limits on, performance, capital cost. It is only a question of finding the balance.
    You are in a position to save as much energy as upgrading a 1000 homes, and likely at a fraction of the cost.
    I would be that confident on making substantional savings, that i would install for free, for 60% of the annual savings.

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    Re: Exhaust Air to Warm water Heat Pump - malt kilning

    desA, you are right - probably worth checking more frequently the condition of the radiators, as maximising heat transfer across them is crucial.

    "I would be that confident on making substantional savings, that i would install for free, for 60% of the annual savings."

    Is this a hypothetical scenario whereby you would do work and you are using this as an example of how much potential there is?
    To reiterate as a student it is my role to investigate feasibility and as far as any capital being spent, not a bean until I manage to persuade a few higher up people that this is something that can be economical and operable.

    Fridgie regarding available electric, i believe there is somewhere in the region of a MW. Awaiting conformation.

    Regards.

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    Re: Exhaust Air to Warm water Heat Pump - malt kilning

    Hi Manny, no was not a hypothetical scenario, I would sign a contract tommorrow. (of course due diligance required, i would need to check your numbers "Sorry") I would design, supply and install all equipment required for free to your client, then I would then take 60% of the annuall savings each year (based upon agreed load profile, or in other words your malting production constant).
    As you get older you start to look for passive incomes, because young wipper snappers like your self, should and hopefully become the masters of these types of design leaving us old farts (present masters) dealing with past out dated designs and thought patterns.
    One benefit of being a student, is that you have all to gain and nothing to loose.
    If you remember earlier in the post we talked about commercial reality (payback period), so when calculating these types of situation, it becomes sort of second nature, to inbuild fiscal and engineering principles when calculating (unfortunately this only comes with experience)
    PS you would have a job as well!!!!

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    Re: Exhaust Air to Warm water Heat Pump - malt kilning

    Ah, well your confidence in the system I have described can only be a good thing.

    Hoping to get elec. avaiable today at the maltings.

    May I ask what setup you are currently basing your calcs on fridgie?

    Spliting hot water, recovering heat from one fraction to input into the remaining stream to heat the glycol?

    Or recovering heat from the warm return stream to put back into the full flow incoming hot stream?

    For sake of I will from now on call 50-55deg C water hot, and 40-45 deg C water warm.

    Merci

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    Re: Exhaust Air to Warm water Heat Pump - malt kilning

    @ Manny:

    MadFridgie knows what he is talking about. If your company does become serious about your proposal, you would do well to have him come over & work through the finer details with you.

    Energy recovery on a large scale requires skillful system designers, with a lot of experience in the game. On this thread you have been privileged to tap into the brains of some of the best practitioners in the field. Peter is top class.

    Saving so much energy translates to an extraordinary amount of potential savings - especially if HFO (heavy furnace oil) is being used as a fuel source. In today's world, HFO should be fast moving towards a three-letter swearword.
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    Re: Exhaust Air to Warm water Heat Pump - malt kilning

    Quote Originally Posted by MannyCalavera View Post
    Ah, well your confidence in the system I have described can only be a good thing.

    Hoping to get elec. avaiable today at the maltings.

    May I ask what setup you are currently basing your calcs on fridgie?

    Spliting hot water, recovering heat from one fraction to input into the remaining stream to heat the glycol?

    Or recovering heat from the warm return stream to put back into the full flow incoming hot stream?

    For sake of I will from now on call 50-55deg C water hot, and 40-45 deg C water warm.

    Merci
    Bon jour,

    You may have gathered by now, that all I am really interested is the process. the process determines the solution.(concept at this stage "10") Now you need to look at the practical application "11", for example you have a spare MW of power, this less than either of the 2 possible options I have given, so we have re-look at the concept, and see how we can get the best use of the max MW of electrical power (more than likely less total heating output, but a higher COP). This continues all through the stages, but it is very difficult to pass on experience gained. thats why you need someone who can look at the practical implications.
    Apart from you air airflows, figures are starting to balance (which will actually balance to meet the airflow load)
    The actual heating process (in my mind) is non of the above, as there are to many losses in efficiency in the above system.

    I do not think my french is up to scratch, and my english is not much better (Lancashire schooling for you)
    Last edited by mad fridgie; 24-08-2010 at 10:04 AM.

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    Re: Exhaust Air to Warm water Heat Pump - malt kilning

    Excellent cheese.

    From a "green" and efficient point of view, and if one accepts that fuel oil will always be burned en mass (more or less), the highest COP choice would seem to be the most logical. I guess if i were to start writing a report in it now (which i aint, dont worry) the objective would read

    "Heat pump feasibility: investigation into significantly increasing air pre-heat temperatures using a heat pump to recover energy and boost the thermal quality of the hot water loop and therefore glycol runaround".

    I just read - you are thinking of another setup? I suppose there will be a whole range of different options. In terms of utilising exhaust air, i dont think that's worth looking into - far away from glycol unit, high up, exhaust stack, all sorts of pish.

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    Re: Exhaust Air to Warm water Heat Pump - malt kilning

    Just saw your post there desA - I am aware I am extremely lucky to get the input of Fridgie and Pete - refrigeration engineers are not in abundance here from what i can tell, and university folks have no practical perspective.

    I realise it is a relatively specialist area of engineering, and although i would like to be able to do the theoretical calulations etc myself, there is clearly much more thought required than a simple vapour compression cycle. Searched high and low for textbooks / literature on industrial heat pump design, to no avail - it seems to be in your folks heads.

    I see it my job to present them with a decent amount of info which explains the benefits a heat pump would bring - and the fact it would save x thousand litres of oil per month, CO2 tonnage saved, etc.

    Then from there in the future they would decide to seek consultancy on the subject. So i feel i need to gain an insight into design and operation, given the process parameters, that would be the starting point for trying to present the idea to anyone in control of capital expendature.

    But yes - extremely grateful for all help thus far

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    Re: Exhaust Air to Warm water Heat Pump - malt kilning

    Quote Originally Posted by MannyCalavera View Post
    Excellent cheese.

    From a "green" and efficient point of view, and if one accepts that fuel oil will always be burned en mass (more or less), the highest COP choice would seem to be the most logical. I guess if i were to start writing a report in it now (which i aint, dont worry) the objective would read

    "Heat pump feasibility: investigation into significantly increasing air pre-heat temperatures using a heat pump to recover energy and boost the thermal quality of the hot water loop and therefore glycol runaround".

    I just read - you are thinking of another setup? I suppose there will be a whole range of different options. In terms of utilising exhaust air, i dont think that's worth looking into - far away from glycol unit, high up, exhaust stack, all sorts of pish.
    The air is an option, and you could use a stacked packed tower, but no I have not gone down this track.
    Just better use of the energy available.
    Your feasability statement would be incorrect.
    "Heat pump feasibility: investigation into significantly increasing air pre-heat temperatures using a heat pump to recover energy"
    would read correctly

    I have given you all you need to come up with the process (just not in a single description) Giving you the direct answer does not help you learn (An argument i have with my wife when doing the kids homework, learn the method, not just the answer)
    I will give you a clue, start with the air (even though I think your figures are wrong)and work backwards.
    Keep up the good work, look at the process not the individual parts.

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    Re: Exhaust Air to Warm water Heat Pump - malt kilning

    Quote Originally Posted by MannyCalavera View Post
    Just saw your post there desA - I am aware I am extremely lucky to get the input of Fridgie and Pete - refrigeration engineers are not in abundance here from what i can tell, and university folks have no practical perspective.

    I realise it is a relatively specialist area of engineering, and although i would like to be able to do the theoretical calulations etc myself, there is clearly much more thought required than a simple vapour compression cycle. Searched high and low for textbooks / literature on industrial heat pump design, to no avail - it seems to be in your folks heads.
    What you'll find on RE are experienced folks who know how to both design & implement a heat-pump system solution.

    The university folks generally only have theoretical solutions - good on paper only. People who have spent many years implementing RHVAC systems will be able to provide an operating, safe, robust solution.

    In MadFridgie & Peter, you have two of the best around, in my view - combining both a solid theoretical knowledge with extensive experience.

    Enjoy the learning experience.
    Engineering Specialist - Cuprobraze, Nocolok, CD Technology
    Rarefied Technologies ( SE Asia )

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    Re: Exhaust Air to Warm water Heat Pump - malt kilning

    Righto, I am going to take a day or two off from the heat pump study so's i can view it with fresh eyes all of next week. I will re-read the thread and your suggested method of process selection, and let you know my findings and thoughts fridgie.

    Cheers

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    Re: Exhaust Air to Warm water Heat Pump - malt kilning

    Quick friday afternoon question.

    In a heat pump the working fluid is going to be cold after it is passed through expansion valve, or similar device - very cold, oui?.

    Aim of, say, the PHE with your heat source is to evaporate the refrigerant.

    My question: if you have the choice of 40 or 52 degC water at equal flowrates, does it make a huge difference which flow you would choose to provide the evaporation?

    My thoughts being the driving force for evaporation (temperature wise) would be so large anyway an extra 10 degC in source temperature wouldn't effect it that much.

    Also, what determines how cold you can get your heat source? E.g., due to the very low temperature of your saturated liquid refrigerant, could you take a warm stream of 40 degC down to the likes of 10 degC, providing you had enough flowrate of warm water?

    That is all for now - have an excellent weekend

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    Re: Exhaust Air to Warm water Heat Pump - malt kilning

    In reverse, travelling for 42 hours to your neck of the woods, I hope I have good looking air hostesses (if not, then weekend will not be so excellent),
    generally the limit on evaporation temps from the comp manufactures (without the need for a special machine)
    Not very cold, where the energy mass balance reaches equalibrium.
    The design determines the temperature. (you pick it).
    List your requirements,
    One was 25C returned back to the process (no need for the cooling tower)
    Look at the process not the heat pump. (The heat pump is designed around the process and the capital cost verses running cost)
    NOT best engineering.

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    Re: Exhaust Air to Warm water Heat Pump - malt kilning

    I have looked at the diagram of the setup for a while now, not getting any major ideas. (it'll help to look at that schematic i drew)

    What seems to make sense to me is using the warm water as the heat source. There is a hold up tank of it before it is returned to the dist. It is waiting to be cooled, but it still has a large amount of energy.

    You could take out a fairly steady flowrate (close to the stream flowrate, maybe a jot less) of warm water and pass it through a PHE, then back to the tank.

    Using this energy stream to do the evaporation it would cool substantially (also a bonus).

    You would pick a desired refrigerant capacity/volume based on the minimum expected flowrate of warm water expected, to ensure it would always give the evaporation duty. This would not upset the warm water return in any way.

    Current glycol HX's have an excess flow of water (easily bringing the glycol up to hot water temp), however i suspect in winter this will not be the case and we will need all the hot water. So for that reason i think it would be best not to split the hot water as previously thought.

    Where to dump all these hundreds of kWs of energy?

    PHE in the line of the hot water directly dumping the energy. This flowrate is variable, however if this is the case and you cannot achieve 100% condensation of refrigerant, does this cause a problem?

    In this setup you could regulate the flow of warm water through the evaporation PHE which would be easily controlled. You could drop it X deg C depending on what worked out to be most efficient.

    You said start with the air flowrates - not sure why. (though i am not questioning your skill ^^) I had done some thermo calcs recently, ~ 80,000 kg/hr/batch is required. As the kilns are paired the demand for air should be constant and consistent.

    Air temperature is the biggy. % RH varies also however this just relates to kiln time. Temperature will effect the glycol return temperature. This will effect the hot water outlet temperature.

    So say in winter, air colder, glycol cooled more, warm water out is cooler, into evaporation PHE cooler, then increase flowrate of warm water through PHE.

    I think the good thing about the plant is that the demand for hot air is always there in roughly the same quantity. As i said before, air is desired at 65 C for half the kilning, and then ramped u p to 85 for the remainder. So a target air pre-heat of 60-65 should be aimed for.

    In my mind this seems to make sense and seems operable. I will try and crunch more numbers on it now. Please let me know why what I have just explained is totally inoperable and wrong.

    Manny

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    Re: Exhaust Air to Warm water Heat Pump - malt kilning

    Ok Fridge have a good journey, wont expect any feedback for a few days.

    Enjoy

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    Re: Exhaust Air to Warm water Heat Pump - malt kilning

    Sorry for the absence but I have to finish a new course for a new 1st year and the agreement was that it must be finished on 31 august. Started a little bit late with it.
    I now have +/- 100 pages, +/- 30 to go.
    I then will rejoin this thread.
    I haven't read the posts of last week.
    It's better to keep your mouth shut and give the impression that you're stupid than to open it and remove all doubt.

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    Re: Exhaust Air to Warm water Heat Pump - malt kilning

    Quote Originally Posted by MannyCalavera View Post
    I have looked at the diagram of the setup for a while now, not getting any major ideas. (it'll help to look at that schematic i drew)

    What seems to make sense to me is using the warm water as the heat source. There is a hold up tank of it before it is returned to the dist. It is waiting to be cooled, but it still has a large amount of energy.

    You could take out a fairly steady flowrate (close to the stream flowrate, maybe a jot less) of warm water and pass it through a PHE, then back to the tank.

    Using this energy stream to do the evaporation it would cool substantially (also a bonus).

    Yes Correct

    You would pick a desired refrigerant capacity/volume based on the minimum expected flowrate of warm water expected, to ensure it would always give the evaporation duty. This would not upset the warm water return in any way.

    No (but you are thinking correctly, need to control refrigeration capacity to meet minimum load)

    Current glycol HX's have an excess flow of water (easily bringing the glycol up to hot water temp), however i suspect in winter this will not be the case and we will need all the hot water. So for that reason i think it would be best not to split the hot water as previously thought.

    Correct do not split the flow

    Where to dump all these hundreds of kWs of energy?

    PHE in the line of the hot water directly dumping the energy. This flowrate is variable, however if this is the case and you cannot achieve 100% condensation of refrigerant, does this cause a problem?

    Not sure what you mean here, (i think what you are taliking about is load limiting)

    In this setup you could regulate the flow of warm water through the evaporation PHE which would be easily controlled. You could drop it X deg C depending on what worked out to be most efficient.

    Correct

    You said start with the air flowrates - not sure why. (though i am not questioning your skill ^^) I had done some thermo calcs recently, ~ 80,000 kg/hr/batch is required. As the kilns are paired the demand for air should be constant and consistent.

    This is the primary load, so you need to work out the best way to introduce energy into the air stream, because this can be improved, if so it then effects all other stages.

    Air temperature is the biggy. % RH varies also however this just relates to kiln time. Temperature will effect the glycol return temperature. This will effect the hot water outlet temperature.

    Correct

    So say in winter, air colder, glycol cooled more, warm water out is cooler, into evaporation PHE cooler, then increase flowrate of warm water through PHE.

    Correct

    I think the good thing about the plant is that the demand for hot air is always there in roughly the same quantity. As i said before, air is desired at 65 C for half the kilning, and then ramped u p to 85 for the remainder. So a target air pre-heat of 60-65 should be aimed for.

    Maybe (ideal), maybe not (practical)

    In my mind this seems to make sense and seems operable. I will try and crunch more numbers on it now. Please let me know why what I have just explained is totally inoperable and wrong.

    Manny
    At this stage do not determine what type of heat exchanger you are using "PHE" just call it H/E (there are other types and should be designed to suit the application, not presumed just to be PHE)

    Well done!! Now you are think of the process and how each part interacts with each other.

    cheers
    Mad
    Last edited by mad fridgie; 27-08-2010 at 09:31 PM.

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    Re: Exhaust Air to Warm water Heat Pump - malt kilning

    Excellent! Very helpful breakdown, much appreciated.

    I see what you mean about air flow and current radiators, will need to do some looking into those.

    Next week will be number crunching time based on observed flowrates and temperatures expected. Will report back then with info's.

    Cheers,

    Manny

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    Re: Exhaust Air to Warm water Heat Pump - malt kilning

    "PHE in the line of the hot water directly dumping the energy. This flowrate is variable, however if this is the case and you cannot achieve 100% condensation of refrigerant, does this cause a problem?"

    What I mean is if the hot water feed to maltings varies flowrate, say a decrease, will it have sufficient capacity to condense (& cool) vapour refrigerant? Perhaps at a reduced flowrate it would just increase in temp but still have the driving force to condense refrigerant.

    I suppose it depends on condensing temps.

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    Re: Exhaust Air to Warm water Heat Pump - malt kilning

    Quote Originally Posted by MannyCalavera View Post
    "PHE in the line of the hot water directly dumping the energy. This flowrate is variable, however if this is the case and you cannot achieve 100% condensation of refrigerant, does this cause a problem?"

    What I mean is if the hot water feed to maltings varies flowrate, say a decrease, will it have sufficient capacity to condense (& cool) vapour refrigerant? Perhaps at a reduced flowrate it would just increase in temp but still have the driving force to condense refrigerant.

    I suppose it depends on condensing temps.
    As long as we know this occurs then it can be handled in a number of ways, this then comes down the practical application and what benefits/ disadvantages may or may not occur.
    The compressor do not have infinite working pressure ratios or preesure limits (in some case these determine the control methodology)

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    Re: Exhaust Air to Warm water Heat Pump - malt kilning

    Ok so a varying hot water flowrate (the stream to recieve the heat from the heat pump) would not cause an operational tits up scenario? Excellent

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    Re: Exhaust Air to Warm water Heat Pump - malt kilning

    Quote Originally Posted by MannyCalavera View Post
    Ok so a varying hot water flowrate (the stream to recieve the heat from the heat pump) would not cause an operational tits up scenario? Excellent
    Going back to air flow, driving force for the varying stages of heat transfer, re look at you quote above, then come back, clue " do not look at heating the water with the heat pump"

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    Re: Exhaust Air to Warm water Heat Pump - malt kilning

    Ok I will re-look through and see what else I can come up with based on what you're saying fridgie. Not much mental capacity today, birthday yesterday and whisky does not sit well ontop of alot of red wine apparently.

    Will get in touch later in week.

    Cheers, Manny

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