Moonwards

kim holder

01:40

@MolbOrg i don't follow what you are doing there

MolbOrg

02:05

dot lines are flow of EM radiation aka light an IR

the curve in bottom is moon surface

each dot on the surface which is between object and horison for the object will illuminate the object with reflected light and IR of its temperature

stick is radiator

reversed hat on the stick is your mirror

black triangles are a percentage of radiation which is emitted from dot on the surface

it does not look like a lot so probably needs take integral to know the real value

but I'm ok just assuming it will be some

dot lines from the hut is the shadow created by the hut mirror

dots in the shadow do not emit or emit less fo the scattered EM

so basically you need trace light in the scene

it is not that big of a problem those scattered light - you can just ignore it, to some extent, because there are simple solutions to solve it. aluminum foil and let it reflect in a slightly different direction.

kim holder

02:49

i don't know why you picked the particular tracks you picked. sun doesn't fall on the radiator, for instance.

@MolbOrg that's exactly what i did

MolbOrg

yep sun is a bit offset ))

kim holder

it seems i followed what your diagram meant, but don't get the message. the reflector under the final rad prevents most of the light from the ground from touching that rad. A fringe on the edges of the reflector would remove all of that light.

do you recall that this radiator turns over the course of the day? it is always edge-on to the sun, the sun's rays fall parallel to it and don't touch it, all day.

since that final rad is there to get the heat carrier down to 300 K, that seems important

MolbOrg

radiator is just top part of the thing?

*all these calculations all this geometry could be avoided by heat field, especially if the target 300K

*just solve heat eqaution and dynamics of the system ))

*reflectivity, relief, geometry of surface all those variables would be irrelevant

kim holder

13:07

the radiator is the whole thing, but the heat carrier is sent up from one rad to the next, each of which cools the fluid more. The final one is the one that is lowering the fluid to below the surface temperature of the moon, so in its case i thought the protection from that heat might be significant

the heat field may be an interesting solution. if it can ever be mapped out for me in a way that allows me to see how it all works

MolbOrg

13:23

probably

MolbOrg

13:46

@kimholder how high is the upper section, and where is the focal point

kim holder

i haven't sized anything yet. it is probably a lot larger than it needs to be.

the focal point is marked by the blue dot in the image above, except that it would actually be a line

the top radiator starts about 35 m above the ground right now

MolbOrg

so it is at least 10 m height, then 20m wide span of the hat is a minimum

kim holder

14:29

the hat? you mean the reflector?

MolbOrg

14:41

yes, reflector

kim holder

yeah, so that's how it is

MolbOrg

yes, reflector is a good smart thing

kim holder

yaayyy!

that makes me feel better. it is really awkward designing an entire moon colony with no training....

MolbOrg

but have a grain of salt, just in case

kim holder

wow... what am i looking at?

MolbOrg

14:46

if interpreted the thing incorrectly, not important what it depicts, it might happened that I made some error

kim holder

but you are going to tell me, right?

MolbOrg

you looking at the angle of a tangent line to parabola scaled 10 (arct/10), normals to the parabola in respective points, parabola itself with the focal point of (0,10)

I was interested in reflection of light from radiator where it goes after reflection from parabola

wonderful thing is that parabola so beautiful - seem it cooperated with what should be done

in any point

kim holder

ah. i made the parabola by cutting through a cone at the proper angle, so it is definitely the right shape

then i got an image of a parabola showing the focal point, because blender isn't made for things like that

and i mapped that onto the model i'd made

MolbOrg

a shape is not important, properties of the shape are important

kim holder

sez you. what happened to the beauty thing you were talking about?

also, if physics was set up in this model, the focal point of the mirrors would be in the right spot.

MolbOrg

14:52

its beauty is in its soul aka properties

kim holder

[rolls eyes]

MolbOrg

)))

because else it just a curve of second order

kim holder

but this is a mathematical shape. are its properties really separate from its shape? hm?

MolbOrg

and beauty in the case it creates a cone of shadow and itself is a section of a cone. however, hm needs to think about that it is 3d structure, hm

@kimholder it's true, but beauty in mind of the beholder, it needs to see it first

I'm not so in math to see it right away or know it, so it just reflection of my imperfection

and I have to work to see

kim holder

it's all fuzzy to me, but i still enjoy it

MolbOrg

15:02

*end of philosophy

the thing changes a bit when we thing about the hat as 3d shape

and it does it not in useful way if I'm correct

kim holder

yes. it will need walls on the end that block light from the sides

i don't see other problems though

MolbOrg

maybe you are correct, I'm not sure yet

kim holder

i still struggle a great deal to see things in 3d, but i am getting better.

modeling helps a great deal

MolbOrg

yes, seems to be ok, but it is not 100% I may be mistaken in the case.

a simplest simulation in 3d could be useful in the case

kim holder

well, once i have the thing done, i can post the model, and you can take a look at it

if you look at it in sketchfab, you can rotate it around and see what the perspective is like

MolbOrg

15:11

I have no problem to imagine the model, I'm not sure about reflection angles in the model and which shapes those reflections are forming according to radiator emitting surface

kim holder

there won't be anything that reflects sun onto it at any time, or that reflects the radiator emissions back onto the radiator

since it rotates, that is fairly easy

MolbOrg

how the conclusion is made?

it seems to be correct, I just not sure if I didn't made some error, but I'm more and more certain, but I would like to have crossvalidation

kim holder

the radiator is always parallel to the sun's rays. the curve of the parabola is always perpendicular to them.

the curve can't reflect the sun towards the radiator because it is never even slightly facing the sun

MolbOrg

no, with sun everything is clear

there is a second source of EM - radiator itself

kim holder

well, if you take the rays as perpendicular to its surface, they all reflect out too

MolbOrg

15:19

and roughly speaking there is 3rd (space), and 4th - end you mentioned - but they are no concern

yes, in 2d. but each point in radiator surface emits in direction of all points of a half sphere with center in the point

but ok, not important seems to be legit - good enough

kim holder

yeah, but if you try to think about that, it will just make you crazy

MolbOrg

I past the point 15 years ago )))

kim holder

bottom line, most of it reflects out

@MolbOrg that explains everything

MolbOrg

@kimholder yep, that I meant, legit

@kimholder you need to exceed any expectation to get 5/5 in geometry from a professor, they like that and very much love their subject of math

yep and all of them this or another way a bit crazy

kim holder

i really like a quote i read, but i can't remember from where

all mathematicians secretly believe that in some way math is real. it has to actually exist somewhere.

there have been far too many pipes in my recent past. i'm sick of making pipes.

(that part isn't a quote.)

MolbOrg

16:15

math is real. there is no question about that, it's everywhere. so the quote is good in that regard.
no one hides that but it is related to properties of knowledge - it can't be stolen and it can't be given, it can be only taken and no one can take more than he deserves.

kim holder

16:32

yeah, but the quote was referring to there being a dimension or connected universe or something where math literally exists. that is, that the formulas that describe reality are themselves actually real somewhere.

it was the opening of a book by a mathematician that was about the nature of reality. but i can't remember his name, or the book's name.

i was thinking of getting it.

kim holder

17:40

ok, all the pipes are in place, and i'm ready to try to approximate size of the radiators

@MolbOrg so, now i've looked over the WB answer you referenced before, with the section on radiators, and i've looked at your additions to the spreadsheet, and i'm trying to figure out how i adapt that to what i'm doing here.

this system has 4 radiators, each one using a different fluid in the heat pipes running to the radiator surfaces, and the coolant goes from one heat exchanger to the next so that each radiator can cool it more, and then circulates back to the cold end of the Stirling engines

so, on the spreadsheet you consider pretty small changes in the temperature of the coolant, and i don't know what you were doing there. My understanding is that this system has to take the heat of the hot end, which is 1450 K, and cool it to the cold end temperature, which is 300 K

since the heat is never going to be cleanly one temperature on the inlet, is it that the thing to do is take the average?

but then, do we have to think in terms of the watts that need to be shed, or something?

even though this is 0th degree, it would be nice if the radiators weren't clearly off in a way a good engineer would spot.

so, i don't know how much i need to work through this and understand it better right now, but maybe i need to know a bit more in order to take your input and size the damn thing

i need to figure out j - that seems to be my task right now for each level of the rad

MolbOrg

18:27

"My understanding is that this system has to take the heat of the hot end, which is 1450 K, and cool it to the cold end temperature, which is 300 K" - if you need such big difference in cooling of waste heat you doing something wrong

how the heat engine system works.

let's take steam turbine as an exmple

kim holder

well, i'm sure i'm saying it wrong. What i'm trying to do is get the cold end of the heat engine down to 300K

MolbOrg

steam gets in inlet of the turbine under pressure and 550C temperature and gets out of the turbine with a temperature below 100C (about 60C) but with pressure below 1 bar

kim holder

that includes a phase change...

MolbOrg

and for what they cool down the thing - to condense the vapor - hidden heat capacity(?) - the energy they have to get rid of. it might be at the same temperature all along

yes, phase change and its heat - then they pump the water back in the system

the main cooling from hot end to cold end happens in the engine itself - by making the work

that is the whole point of particular cycles (not all of them)

when there is not phase change - you cool the output while compressing it

so the output can have the same temperature during the whole process of compressing the thing back.
then they heat the compressed thing and let it do the work - which cools it down

and you get those paralelargamm like plots on P-V graph

kim holder

ah yes - the compression. i've seen that on the diagrams, but haven't known how to put it in the system

or does the compression that happens in the engine do that?

MolbOrg

18:38

you can heat the working carrier all time during its work in the engine - and can get the output at the same temperature as the hot end temperature. But usually, it is in engines which do not reuse heat carrier(roughly speaking)

kim holder

[opening 'heat engine' on wikipedia again]

MolbOrg

different types of engines and approach to deal with temperatures is the reason to select working media

kim holder

Stirling cycle

The Stirling cycle is a thermodynamic cycle that describes the general class of Stirling devices. This includes the original Stirling engine that was invented, developed and patented in 1816 by Robert Stirling with help from his brother, an engineer. The ideal Otto and Diesel cycles are not totally reversible because they involve heat transfer through a finite temperature difference during the irreversible isothermal heat-addition and heat-rejection processes. The irreversibility renders the thermal efficiency of these cycles less than that of a Carnot engine operating within the same limits of...

MolbOrg

kim holder

so, the expansion of the working fluid helps with the cooling, sort of?

at least, it is turned into work, right?

MolbOrg

18:46

in this simplistic diagram your coolant will change temperature slightly, if not then the gas in cylinder will not reach 300K and will make less work and will be less efficient

kim holder

the connection between the two piston chambers of a stirling engine does mean that some of the heat of the hot chamber is always being pushed to the cold chamber

MolbOrg

and the 300K coolant is what you should cool in radiators - and less the difference of temperatures of the coolant then better, but not realistick because it needs infinite supply of it or very rapid movement in cooling system

@kimholder yes, not in all cases, as example jet engines - but they have infinite supply of fresh cold air so they do not care

@kimholder yes

kim holder

so, am i dealing with the amount of heat the cold chamber absorbs in a certain amount of time, that has to be shed on the radiators?

MolbOrg

@kimholder Stirling is mind bending thing

@kimholder yes

the goal is to keep cold chamber at given temperature

kim holder

ok, now i'm back to the situation that i have no idea how to estimate that...

MolbOrg

18:52

so you spray it with 300K, collect the coolant back at 320K or 350K - cool the coolant back to 300K repeat

effective temperature will be something in between of those both let's 310-330K

it will be average temperature of your cold end

effective temperature of a cold end for the engine

@kimholder you estimate it by heat capacity of the working medium/(volumetric flow of the coolant*heat capacity of coolant)

kim holder

MolbOrg

if your question about estimating how much heat you have to emit - its simple

kim holder

so, the volume of the piston chambers has one working fluid, that is passing heat to the coolant passed around the chamber, which is probably a different fluid

MolbOrg

you have an electric power you need (10MW) you have an efficiency of the engine ((Thot-Tcold)/Thot

if efficiency is 50% as an example - you supply 20MW heat power from your heat reservoir, you get 10MW electric power, 10MW heat power which you need to get rid of

kim holder

well, this is a modular unit now. i need to figure out how much power it can be expected to produce, and then set up a bunch of them, so they add to 10 MW

i worry now too much about things melting or being insanely hard to pump fast enough, since you have started talking to me about this

so i made the heat store much smaller so the problem is manageable

MolbOrg

19:00

you have cold end temperature thus you have power which can be emitted from 1 square meter
Waste heat / that -> amount of square meters required

kim holder

alright - the thing is i was thinking in terms of the heat coming in much hotter. it didn't seem right, but the definition of efficiency is hot end vs. cold end, so i thought that had to be part of the calculation somehow

MolbOrg

so to estimate surface area you need it is required - power, efficiency, cold end temp - three variables

kim holder

hm...

MolbOrg

@kimholder it is part of the calculation - in efficiency and in amount of heat you have to dissipate

kim holder

ok. when i look at the work you were doing on the spreadsheet about that, i can't figure out how it applies to that

it doesn't seem to have any relation to the figures for the hot end and the cold end i had established - mostly in consultation with you

MolbOrg

19:07

power, efficiency, cold end temp - those are freeing you from defining working fluids, those variables are independent of that.
However, in fact, cold end temperature is dependent on working fluids and design of the system.

it will be defined by the limitation of the system and which materials it uses, which gases/liquids it uses etc

but you can select the temperature arbitrary in hope that there will be a design which satisfies the requirement

kim holder

the design system here is different. it starts with the best numbers that can be reasonably expected, and then figures out what the system needs to be.

@MolbOrg exactly

that is what i've spent quite a lot of time doing, figuring out the best reasonable numbers.

i really don't think they are excessive, i tried my best to put them where they can be done. and sized the system with that consideration too.

MolbOrg

I doubt there is such system(I'm sure it isn't) or which might be designed to meet the 300-1400K temperature range on single heat media

kim holder

who said there was a single heat media?

you're the person who likes single heat medias

MolbOrg

I'm not the person, I just admire simplicity, because it allows to not stick in too much details

kim holder

moonwards can't use simplicity, it has to use something that good engineers look at and see the potential in. they want those details.

MolbOrg

19:15

and show that some system can work and if one will offer a better system I will be much happier, but I aware about my limitations and do not try to bite more than I can chew )

kim holder

well, i said that because i recall that one of the keys to your heat field system is that it uses one heat medium

MolbOrg

it uses one because a range of temperatures is not high, and because it relays on a way to extract the heat media from ISRU and because it requires a lot of it. - those are reasons for that. Another reason it is just simpler to estimate things when such systems are can be considered independantly

kim holder

yes, but i can't model it. that's why i set it aside. and that brings me back to the need to estimate heat the radiators need to shed, which requires me to estimate how much power this thing is producing

i put a guess of 380 KW on the spreadsheet, but i don't know if that was good or not

MolbOrg

"estimate how much power this thing is producing" - if you mean radiator then it does not produce and how much it is from - PowerElectrical/efficiency - Power electrical = how much radiator has to dissipate

Electrical power is assumed value - based on requirements of the base

kim holder

> so to estimate surface area you need it is required - power, efficiency, cold end temp - three variables

no, the unit is modular, it has been sized so the system works.

MolbOrg

19:23

hm, I do not get the question/problem here

in modularity of things

kim holder

it isn't arbitrarily a certain power, it has been set up so that the aluminum heat carrier can be pumped reliably fast enough to keep the pipes in the mirrors at a good temperature

alright, forget the damn modularity, look at the sizes in the spreadsheet

(she says, to the person who convinced her it was necessary to make it modular in the first place.)

MolbOrg

if you have surface area for mirrors of collector - you have the maximum possible electrical output for the system

kim holder

yes, but of course that isn't the actual output.

and i put in the Carnot number based on the hot cold end

and then i took a third of that, which was just a plain guess

MolbOrg

yes it isn't - you estimate efficiency - make the best guess

kim holder

seriously man. the numbers are all there

let me rearrange them so they are clearer

MolbOrg

19:28

trow a link - I lost it and it moved from faworites of the chat

kim holder

ok, let me just fix it a little more

MolbOrg

I will need time to find what you addressing - so it is better that I get the link earlier )

docs.google.com/spreadsheets/d/…

kim holder

yeah, in consideration of that, i thought i'd try to label things better before actually sending you there

but it's too late :))

MolbOrg

fote for link - I can't do it for my message

*vote

kim holder

it is pinned in the sidebar

at least, it was pinned... now it is just on the list. hm.

MolbOrg

19:32

exactly!

now break for a minute

You can and must state the electrical power of the base

let it be arbitrary number

kim holder

no, i can't and i won't

you know that number would be insanely arbitrary

MolbOrg

on based on the number you do the sizes for mirror system and for tank

kim holder

sure, i picked 10 MW before, and i'm still okay with that, even though it is a total guess which will almost certainly change drastically

but it doesn't matter. there will be many of these units. as many as it takes.

MolbOrg

@kimholder I tried to get reasonable estimation of it with you a long time ago, but they you said - 10MW is enough for me period.

kim holder

not as many as your heat field, because they are still supposed to be a lot more efficient than that, but many

MolbOrg

19:35

I said ok, 10MW than 10MW it is not important at the end

kim holder

the population of the colony changes, it is a growing thing

there is no final population, and the population over the course of the phase this colony shows

grows from i believe it is 500 in the beginning to 20,000 at the end

at some point in there, it will be drawing 10 MW

MolbOrg

true, so you do not calculate the sizes for a total 10MW base consumption - but you just calculate systems for a 10MW of electricity production.
If they need more 100MW they will just build another 9 systems like that and that all - not problem there in assuming some number.

kim holder

and then they will add more industry, and change things around, and there is no freaking way i can possibly tell you how much power they need

what difference does it make? the unit is modular. if they need more, they build more. it makes absolutely no difference to what we are talking about.

MolbOrg

@kimholder exactly. they will build as much as needed - why it is a problem then to assume some number.

kim holder

because it has nothing to do with what i'm asking you about. aaaaahhhhhhhhhh

MolbOrg

19:41

@kimholder you asking about how much radiator should emit power

kim holder

dear god

MolbOrg

I guessed right?

kim holder

and yet you understand it completely wrong....

MolbOrg

hm

kim holder

look. i have designed a unit. we don't need to talk about how many we are going to need. we need to talk about how much power that one unit - which, i feel a need to comment, i have spent like 6 weeks building - is going to produce.

if you don't see how the spreadsheet is working, the thing is the heat store receives about 3 MW of heat all through the day

there is probably something connected wrong, that is why it doesn't make sense to you...

let me check it

E5 and H5 are showing the heat coming in per square meter, and the heat shed

look at G9

that is that 3 MW times the efficiency, divided by 2 as a really simple consideration of the night

which comes to 384 KW

kim holder

20:02

i don't know how to do all that formatting. i've looked for that a couple of times.

oh, it's in the toolbar... i was looking in the menu...

MolbOrg

borders the button with suare, merge cells - two row button etc

yes tool bar

kim holder

the formula in I4 is counting the number of mirrors twice

F4 is total area, it already counts the number of mirrors

it's true there should be a field for the area of one mirror

i'm going to go ahead and fix that

MolbOrg

hm

SA per m - ?

F7

kim holder

i had just used SA to get a proportion, so i wasn't interested in the total for all the tubes

no, there is a gap

MolbOrg

surface - you do not need to count gaps

kim holder

20:10

that subtraction needs to be there

MolbOrg

because gaps do not reflect the light

kim holder

yes, so they need to not be counted as part of the surface reflecting light

MolbOrg

yes

kim holder

the gap was being subtracted from the area of the mirror

you didn't look at the formula

you don't believe me, do you.

the mirrors are 22.5 m wide, including the gap

so, i subtracted the gap

MolbOrg

Width (chord) - does it not the width of mirror - perpendicular to pipe?

kim holder

20:16

yes, and the pipe blocks part of the sun, and so there is a gap down the middle of that mirror

that gap is 0.75 m wide

MolbOrg

)))))

kim holder

i guess the model is so clear in my head, that is just obvious to me

i first built that mirror over a year ago

see, that formula on the end used a ratio. that ratio was based on one mirror, not all of them.

MolbOrg

red green blue - who is who

kim holder

red is 22.5

MolbOrg

length, width (chore), witdh

kim holder

20:25

the gap in the green line is 0.75

MolbOrg

is there a reason to be so big

kim holder

the blue line is covering 2 mirrors. it is hard to tell at this angle. each one is 20 m

is there a reason not to be?

MolbOrg

so blue is about 40m - ok

kim holder

no, that is a separate mirror

each mirror is 20 m long. if you want to know how long that line is, i couldn't tell you.

each one has its own pipe, connected separately to the heat store

MolbOrg

solar light is about to be parallel so the shadow will be about the size of pipe, so we loose light and od not squeeze max o the installation, however, there might be some manufacturing reason for that

kim holder

20:29

the size of the insulation protecting the top of the pipe is 0.75 m

MolbOrg

ok

kim holder

because it has a lot of layers, and i don't know how good a job it can do, but it seemed like a good place to use lots of layers.

F7 doesn't need to be multiplied by 2

B7 is already the diameter of the pipe

in fact, it needs to be divided by 2

MolbOrg

F7 is yours - idk what it is

kim holder

it's the surface area of one meter of the pipe receiving the sun

MolbOrg

google docs has its own chat in case you do not know

kim holder

20:38

oh, hey yeah

i hadn't noticed that

MolbOrg

23:11

kim holder

oh yeah! hey, he was great.

i loved that movie

so, that spreadsheet is everything i wanted now. thanks a lot for that.

MolbOrg

ok

kim holder

so there should be some losses on that from the heat tank? some estimate that would lower output a bit?

you know i keep wanting to be way more specific than is really reasonable. but since we have a number, i should reduce it a bit, shouldn't i?

MolbOrg

no until you do some estimation for heat losses for tank

kim holder

hm. ok.

MolbOrg

23:18

just keep in mind that atm it is best case scenario for tank

and that it is upper estimation for the system

kim holder

well, first i'll redo the radiator

MolbOrg

those radiators vertical horizontal - probably should go away

not needed

kim holder

yeah, it looks like what you show is only for one radiator, the one on top of the 'hat'

MolbOrg

I made copy, so feel free to shape it as you wish, I'll compare it with field solutions in same way

kim holder

(though usually hats go on top of other things)

MolbOrg

23:20

it is reverse hat )

kim holder

i'm going to save that radiator design anyhow. i don't know, maybe it has some application to cryogenics...

MolbOrg

23:37

polar regions will be good for cryogenics

MolbOrg

23:50

@kimholder check that the document is in a folder you expect it to be

a folder on google drive or where it is

kim holder

@MolbOrg that's true, but the base being worked on right now is at the equator, and it will be producing gasses that need liquifying. oxygen, at least.

the assets are all stored right now on GitHub

except for a few things that are outdated, and even some of that is there

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