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Re: Exhaust Air to Warm water Heat Pump - malt kilning
Quote:
Originally Posted by
MannyCalavera
I am going to have to give this some thought Mad - l'm ignoring kiln 9 for now.
3&4 = a pair = 60 te / batch
5&6, 7&8 = a pair = 30 te / batch
Mad I am speaking total dross - there are seven kilns - (one and two have been redundant for years). So it is 3-9.
So there is quite a load - I firstly need to get the data on WHEN the saturated air is available, how constant it is across the 7 kilns, and also the demand. As I have said, I am assuming un-varying warm water supply.
As I say, later in this week I get to see the sequences of the kilning.
83% efficiency i believe for the boiler. 90% efficiency in the steam radiators.
On a related note, what kind of compressors are usually used for refrigeration?
Cheers guys.
As you can gather, there are many options open on the refrigeration side, what refrigerant and what type of compressor and the number of stages, really depends upon evaporating and condensing pressures, which directly relate where your energy stream is coming from (suction pressures) and what temperatures you will require or what is the best use of the absorbed energy and what levels of turn down and limits on extremes.
For this reason, is why total understanding of the process becomes paramount. I have seen many systems that have been well designed for steady state conditions, but become a total balls up when changes happen in the process variables.
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Re: Exhaust Air to Warm water Heat Pump - malt kilning
Say a system does change, say the warm water flowrate / temperature decreases, what are the knock-on effects on the refrigeration system?
Could you just list a few things that would go tits up? I.e. would the compressors die if there was liquid in there that hadnt evaporated?
My next step now is to do some quantifying of availablilty of heat sources, as you suggest. Hopefully within a week I can give you some concrete flowrates, etc, and I myself can do some calculations on the energy saved with hypothetical glycol temperature increase.
Regards
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Re: Exhaust Air to Warm water Heat Pump - malt kilning
Quote:
Originally Posted by
MannyCalavera
Say a system does change, say the warm water flowrate / temperature decreases, what are the knock-on effects on the refrigeration system?
Could you just list a few things that would go tits up? I.e. would the compressors die if there was liquid in there that hadnt evaporated?
My next step now is to do some quantifying of availablilty of heat sources, as you suggest. Hopefully within a week I can give you some concrete flowrates, etc, and I myself can do some calculations on the energy saved with hypothetical glycol temperature increase.
Regards
There are no real problems, if you know the extremes, you design around potential problems, but this does have a factor on the capital cost.
Basically you control the load by many different methods, but when unloaded care has to be taken with other factors, it just a question of balance, protection and retaining efficiency. many of the threads on this forum relate to poor equilbrium.
Its time to go for kip.
look forword to future info
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Re: Exhaust Air to Warm water Heat Pump - malt kilning
Alright Fridgie cheers for your help thus far.
I will keep checking the forums incase there are further posts, but later in the week I will get in touch with some concrete numbers.
I feel I am slowly becoming more aware of the wider picture of heat pumps which is most excellent.
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Re: Exhaust Air to Warm water Heat Pump - malt kilning
"This is a very interesting thread. I will ask some NH3 experienced guys joins this one. They perhaps can help."
Just saw this Pete - would be very much appreciated.
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Re: Exhaust Air to Warm water Heat Pump - malt kilning
I thought I would help with the correct thought process.
1 What is the problem (excessive fuel use)
2 Analize the problem (In the case the malting process, this needs to be indepth)
3 Set the criteria for the selection of the possible solutions. This is as important as the solution its self!
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Re: Exhaust Air to Warm water Heat Pump - malt kilning
just some theoretical interesting facts (not a great deal to do with the practical application and installation)
it is possible to reject more heat out of the heat pumps than the process requires, which is typical for drying processes. (heat absorbed from both the dist. water and the kiln air, Direct)
If the process could be completed with 75C glycol, then COP would be approx 4, which indeed would reduce the running cost by 50%, or a million quid or year.
If we look at any drying process there are 4 main loads
1;Thermal losses
2;Heating of mass (product and building)
3;Water vapourizing
4;Heating of make up air. (this is required to carry the moisture away, warmer air has a higher water vapour carry capacity)
When a product is drying, the product and the "air passing over" drops in temp, whilst pickup moisture, increaseing the RH by the two changes, how ever the energy in the air remains the same (exclude any losses) This is expelled
So it would seem that we should just reclaim all the energy from the process, and introduce it into the in coming air (looks like the simplest of solutions) BUT dry air does not have good energy carry abilities, therefore the air would need to heated to a very high temperature to reach equalbium (balance), this then becomes the achillies heel of a refrigeration heat pump, to achieve these high temps the condensing temperature would also need to be very high. Which means our COPs drop dramicatically (never mind the other technical issues), Would you then buy one?
You should now be think about increasing the fresh air make up flow, to reduce those condensing temperture, More air in means more air out, The air that is expelled, is likely to have a less favouravble properities (low dew point), which then causes the evaporation temperature to fall, again reducing the COPs. This also can have a detremental effect on the product, some products skin if dryed to quickly, reducing the flow of entrapped moisture in the product, which normally has to be overcome with a higher temperature (again not so good for a heat pump)
Why not just but the heating coil in the main air stream, always sounds like a good idea, but in many drying processes the main air stream is all ready heated, so similar sets of problems occur, one of the main limitations to just increasing the air flow is the increase velocity of the air, which if to high can cause the product to leave its container (blows in the wind).
When dealing with higher temperture drying with a heat pump you tend to undersize the heat pump, which normally give excellent COPs and reliabilty and add an addional high temp heat source, which you use for control.
With low temp drying systems you normally oversize your heat pump, and reject excess heat external of the process
So when it comes to drying and heat recoevery with a new system/method it is 80% design and 20% Fudge, more info you have the better you manage the fudge. And is very product specific
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Re: Exhaust Air to Warm water Heat Pump - malt kilning
What you must do once to enlighten this a little bit and this will help you also in the future: make once a simple hand-drawn schematic of the whole system and insert on different copies - for every process phase one (germination after water immersion or spraying I suppose, then the heating) - the right numbers , temperatures ,mass flows of water, their associated temperatures, mass flow of the malt/kiln, time for every production process, mass flow and temperatures of air in's and out's,......
It's a continuous process I suppose where a kiln or several kilns are busy with germinating while others are drying and others are emptied and/or filled up.
So the better we understand clearly the production process and the production flow of it the better we can help you with our experience.
I think MadFridgie will agree with me: this project has very great potentials and can offer your client big savings but it must be very well calculated and documented first. The more precise your numbers are, the more precise you can predict the savings.
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Re: Exhaust Air to Warm water Heat Pump - malt kilning
Thanks for advice guys - I have started compiling info since it's up and running again. Hope to really understand the extent of "steady state" that it is actually operating at. Once I have all the parameters of the process fully understood and all the variables, I will see what energy is available and when, and then hopefully you might be able to advise on COPs etc. This within a week or two max I hope.
I had a slightly related question (maybe obvious). Can you control the extent of heating? E.g., if a system was designed to raise a fluid to a temp of 75degC, but for 2 hours you only required 65degC, can heat pump systems cater for this (if source parameters stay constant)?
Pete that invoice looks extremely up-to-date. That factory looks far more asthetic than the maltings I work on!
Regards
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Re: Exhaust Air to Warm water Heat Pump - malt kilning
Quote:
Originally Posted by
MannyCalavera
Thanks for advice guys - I have started compiling info since it's up and running again. Hope to really understand the extent of "steady state" that it is actually operating at. Once I have all the parameters of the process fully understood and all the variables, I will see what energy is available and when, and then hopefully you might be able to advise on COPs etc. This within a week or two max I hope.
I had a slightly related question (maybe obvious). Can you control the extent of heating? E.g., if a system was designed to raise a fluid to a temp of 75degC, but for 2 hours you only required 65degC, can heat pump systems cater for this (if source parameters stay constant)?
Pete that invoice looks extremely up-to-date. That factory looks far more asthetic than the maltings I work on!
Regards
The simple answer is yes, you have decide is just temperature change, with a similar amouny of produced energy, (reduced glycol flow) or increased temp change and increased energy produced (same glycol flow)
You are now thinking in the correct manor.
Well done
I agree with Pete, its all about understanding the process. I suspect dollar for dollar, that the greatest savings will be made by optomising the diversity of the 6-7 Kilns
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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 :rolleyes:)
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Re: Exhaust Air to Warm water Heat Pump - malt kilning
Whats yo in 16 yo ?:o
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.
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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
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1 Attachment(s)
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
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Re: Exhaust Air to Warm water Heat Pump - malt kilning
Quote:
Originally Posted by
MannyCalavera
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
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.
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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.
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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
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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1 Attachment(s)
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
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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
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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.
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Re: Exhaust Air to Warm water Heat Pump - malt kilning
Quote:
Originally Posted by
Peter_1
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
Greetings desA. 24/7, yep. (aside from a few weeks every summer for annual maintance of site).
Ok. Good. Makes things a bit easier.
Quote:
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
"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!!!!