Heating Cost

File: 574 KB, 1536x2048, IMG_20150314_003042.jpg [View same] [iqdb] [saucenao] [google]

Heating Cost Anonymous Fri Mar 13 23:55:37 2015 No.7128749 [Reply] [Original]

Well, /sci/?

Is she right?

Below was my response. Am I just retarded or something?

>>	Anonymous Fri Mar 13 23:57:50 2015 No.7128752 I can't read your response.

>>	Anonymous Sat Mar 14 00:00:04 2015 No.7128755 I said "Oh really? Didn't know the furnace being on stopped heat from escaping the water tank. Good to know! :)"

>>	Anonymous Sat Mar 14 00:04:25 2015 No.7128756 >>7128755 you are retarded

>>	Anonymous Sat Mar 14 00:05:26 2015 No.7128758 >>7128755 thermal inertia

>>	Anonymous Sat Mar 14 00:07:34 2015 No.7128759 Your mom is paying the bill and you are her retarded son. This is enough said

>>	Anonymous Sat Mar 14 00:11:12 2015 No.7128765 >>7128756 >>7128758 >>7128759 indeed. >>7128749 >>7128755 Your poor fucking roommates.

>>	Anonymous Sat Mar 14 00:16:04 2015 No.7128771 >>7128749 A little retarded. Anyway's its unclear on how much energy it takes to heat up the tank entirely or how much heat escapes when the furnace is on.

>>	Anonymous Sat Mar 14 00:18:32 2015 No.7128776 >>7128771 >u cant kno nuffin OP is a dumb gay faggot and wrong

Anonymous Sat Mar 14 00:18:58 2015 No.7128777

In my defense, I turn it off at night because they leave the heat on full blast and it's costing us hundreds more than it should be. My room also heats up because of the universal thermostat so I'd either be turning it off or opening my window at night. No I don't live with my parents.

>>	Anonymous Sat Mar 14 00:26:58 2015 No.7128788 You're right, but I can't think of any way to explain it that doesn't use differential equations.

>>	Anonymous Sat Mar 14 00:27:27 2015 No.7128790 >>7128788 no.

>>	Anonymous Sat Mar 14 00:28:16 2015 No.7128791 >>7128749 She is correct and you are a retard. It's the same reason that you get better mileage on the highway than you do in the city.

>>	Anonymous Sat Mar 14 00:28:58 2015 No.7128792 And why would thermal inertia make the furnace work harder? Don't they heat at constant rates? It's not like a car engine that has to produce torque and heat as a byproduct.

Anonymous Sat Mar 14 00:35:03 2015 No.7128799 [DELETED]

ffs. Newton's law of cooling from intro calculus:

<span class="math"> \frac{dT}{dt} = -kT <span class="math"> for some positive constant k, temperature T, and time t. The higher the temperature, the faster the temperature decreases. Lowering temperature equates to losing heat, thus a body at a higher temperature looses energy faster than a body at a lower temperature. Energy = money.

OP is correct.[/spoiler][/spoiler]

Anonymous Sat Mar 14 00:36:41 2015 No.7128801

ffs. Newton's law of cooling from intro calculus:

<span class="math"> \frac{dT}{dt} = -kT [/spoiler] for some positive constant k, temperature T, and time t. The higher the temperature, the faster the temperature decreases. Lowering temperature equates to losing heat, thus a body at a higher temperature looses energy faster than a body at a lower temperature. Energy = money.

OP is correct.

>>	Anonymous Sat Mar 14 00:39:37 2015 No.7128807 >>7128801 this entire post is so fucking wrong.

>>	Anonymous Sat Mar 14 00:40:03 2015 No.7128808 >>7128801 This is correct.

>>	Anonymous Sat Mar 14 00:41:41 2015 No.7128810 >>7128807 You are an idiot. Provide specific objections or get out.

>>	Anonymous Sat Mar 14 00:42:48 2015 No.7128813 >>7128807 I'll take Burden of Proof for 400, please.

Anonymous Sat Mar 14 00:44:45 2015 No.7128816

>>7128801
>>7128810
>>7128813
ok fucking retards
newtons law of cooling is for convective heat transfer only and is
q'' = h(Ts-Tinf). do a proper energy balance and with heat equation, and get some initial conditions before you start talking about some shit you know fuck all about

>>	Anonymous Sat Mar 14 00:48:10 2015 No.7128821 >>7128749 I CANT READ YOUR SHITTY HANDWRITING

Anonymous Sat Mar 14 00:50:02 2015 No.7128825

>>7128816

A furnace losing heat *is* governed by convection, you retard. The object will approach the temperature of it's environment, and seeing as how it's a furnace, it will be higher than the air it is supposed to be heating.

The diffEQ's are the fucking same. Go pretend to know what you're taking about on /pol/ or something.

Anonymous Sat Mar 14 00:51:11 2015 No.7128827

>>7128801
>completely disregarding the amount of energy required to heat the body of water back up to the required temperature and not making a comparison between the two scenarios.

Congrats on typing out a bunch of shit that does absolutely nothing to prove either side of the debate right or wrong.

>>	Anonymous Sat Mar 14 00:53:26 2015 No.7128830 >>7128825 >once it's reached equilibrium with surrounding you have to heat it up again entirely maybe you should take an actual heat transfer class dickhead

Anonymous Sat Mar 14 00:56:22 2015 No.7128831

>>7128827

You are incorrect. The amount of energy it takes to heat the furnace back up is less than the energy it takes to incrementally heat it up overnight and maintain the temperature because the heat lost from keeping it high all night is greater than the heat lost from a single cooldown.

>>	Anonymous Sat Mar 14 00:57:28 2015 No.7128833 >>7128831 >here is my intuition, without quantitative proof brilliant

>>	Anonymous Sat Mar 14 00:58:04 2015 No.7128834 >>7128830 What are you on about? Of course you do.

>>	Anonymous Sat Mar 14 00:59:12 2015 No.7128836 >>7128833 >what are differential equations Graduate high school and get back to me.

Anonymous Sat Mar 14 01:00:50 2015 No.7128839

>>7128836
holy fuck you're literally retarded. you spouting bullshit (without any equations that you keep bullshitting about) with no numbers or boundary conditions mean fucking nothing. you are literally retarded and have no clue what you're talking about

>>	Anonymous Sat Mar 14 01:03:35 2015 No.7128844 >>7128839 I have justified that assertion over and over in this thread. I'm done arguing with retards on the internet, just fucking google it and find that every single source supports turning the damn system off over night.

>>	Anonymous Sat Mar 14 01:03:52 2015 No.7128845 If you can't see that turning the furnace off saves energy intuitively you're a fucking idiot who believes in magic.

Anonymous Sat Mar 14 01:08:23 2015 No.7128855

>>7128831
So you're saying that you know what the insulation value of the tank is, the rate at which it loses heat, the size of the tank, how much energy it takes to heat it up to operating temperature, and how much energy is required to maintain constant operating temperature? Because that's the only way you could possibly make that claim and have it not be a complete ass-pull.

>>	Anonymous Sat Mar 14 01:11:25 2015 No.7128861 >>7128844 holy fuck you're so fucking stupid.

>>	Son of man Sat Mar 14 01:12:04 2015 No.7128862 Do you have a personal relationship with our Lord and Saviour Jesus Christ? The Son of God. For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life. - John 3:16

Anonymous Sat Mar 14 01:14:27 2015 No.7128863

>>7128855
Why are you on /sci/? Hopefully it is to learn...

Let's think about this quick. Let's say you have two cups of water at 100ºC... Now you let both cups cool to 95ºC. Cup #1 you heat back to 100ºC and you repeat this process for 24 hours while cup #2 slowly cools to room temperature.

24 hours later, cup #1 is still 100ºC, and you heat cup #2 to 100ºC as well. Which cup required more energy input?

>>	Anonymous Sat Mar 14 01:17:34 2015 No.7128865 >>7128863 why dont you calculate it since you know so much about heat transfer guy

>>	Anonymous Sat Mar 14 01:23:50 2015 No.7128870 File: 2 KB, 244x226, 1348764844816.png [View same] [iqdb] [saucenao] [google] >>7128865 Is it time for this?

Anonymous Sat Mar 14 01:26:25 2015 No.7128875

Generally, keeping it running when you're not using it would require more energy than simply turning it on when you need it, since some amount of heat generation is needed to maintain the water at that high temperature. If the tank is well-insulated, as modern tanks should be, the heat loss would be minuscule but it would still be something.

>>	Anonymous Sat Mar 14 01:26:26 2015 No.7128876 >>7128870 yeah go through with your little calculations guy, this should be quite entertaining.

Anonymous Sat Mar 14 01:31:09 2015 No.7128881

>>7128863
>not heating it for 24 hours

Do you even understand the scenario in question? PROTIP: it won't be off for 24 hours, and it won't be room temperature when it is turned back on because the tank is insulated. They lose so little heat that you can put your hand on the outside of a water heater and it feels pretty much room temperature. As such it uses very little heat so long as you're not actually pulling hot water from the tank which gets replaced with cold water.

Anonymous Sat Mar 14 01:39:34 2015 No.7128888

>>7128881
Do you understand how the scenario in the OP relates to the scenario I posed? Apparently not. There's only one scenario where energy output is equal - and that's when the water tank never cools below the thermostat's set point.

Protip: insulation doesn't matter, even if it were 100% insulated there's no way to save energy by leaving it on. You''re retarded.

Anonymous Sat Mar 14 01:48:14 2015 No.7128894

>>7128875
I didn't word this correctly. If the water in the tank would otherwise reach thermal equilibrium with its surroundings, the energy needed to maintain it at a high temperature is greater than the energy needed to heat it from room temperature. If the tank is very well-insulated to the point that it can keep the water at a temperature greater than the room temperature over any conceivable time interval when it is not being used, then there is essentially no difference; you're simply choosing between heating it over a short period of time or a long period of time. You're safest bet is to only heat it up when you need it; it can't hurt.

Anonymous Sat Mar 14 01:48:54 2015 No.7128895

On a long timescale heat-in = heat-out for your house, because it is neither increasing nor decreasing in temperature in the long term.

Heat-in comes from your furnace. Heat-out comes from losing heat to the outside. Now the higher the temperature your house, the more heat your house loses. So heat-out is higher. Since heat-in = heat-out, this also means heat-out is higher.

>>	Anonymous Sat Mar 14 01:49:48 2015 No.7128896 >>7128894 >You're Your

>>	Anonymous Sat Mar 14 02:02:22 2015 No.7128907 >>7128894 Still a little wrong. You're using more energy if the heater is engaged at any point prior to use. Again the only scenario where energy is equal is when the tank is insulated well enough to never go below the set point on the thermostat.

>>	Anonymous Sat Mar 14 02:04:41 2015 No.7128912 >>7128907 you are so fucking stupid

>>	Anonymous Sat Mar 14 02:09:49 2015 No.7128918 >>7128912 Do you have an explanation or are you just a pleb without a basic understanding of science?

>>	Anonymous Sat Mar 14 02:14:06 2015 No.7128919 File: 89 KB, 716x381, learn2heattransfer.png [View same] [iqdb] [saucenao] [google] >>7128918 >pleb without a basic understanding of science? kek

>>	Anonymous Sat Mar 14 02:15:42 2015 No.7128921 >>7128907 I think we're saying the same thing. The only scenario where the energy used is equivalent is when the water temperature doesn't reach the ambient temperature when it is turned off.

Anonymous Sat Mar 14 02:25:00 2015 No.7128935

OP.
1. Your housemates are a bunch of pussies.
2. Buy them electric blankets.
3. Every post here is written by a retarded monkey, the point of a heating system is to lose heat into the radiators, so insulation is what? Defeating the point of the system.
4. Have the thermostat turn on at 3am for an hour or so, peoples sleep patterns are not so deep, that will take the chill out of the air and keep the pussies purring.

5. You are correct, waaay too fucking expensive to run all night, no insulation on radiators man!

>>	Anonymous Sat Mar 14 02:26:08 2015 No.7128936 >>7128935 >insulation >on something meant to heat your room just how stupid are you

Anonymous Sat Mar 14 02:41:35 2015 No.7128946

>>7128919
>hurr durr I'll post an equation I have no clue how to use to attempt to look intelligent

>>7128921
No. If the tank that's "on" is reheated at all overnight it requires more overall energy then the tank that's off. The tank that's off never needs to reach ambient temperature for energy savings.

>>	Anonymous Sat Mar 14 02:43:39 2015 No.7128947 >>7128946 it's from my class notes m8. give it up you're retarded.

>>	Anonymous Sat Mar 14 02:51:53 2015 No.7128953 >>7128947 Then explain your position... You don't seem to have even basic grasp of Newton's law of cooling if you can't understand this scenario.

Anonymous Sat Mar 14 03:01:16 2015 No.7128965

>>7128755
You're right. I had to convince some coworkers last summer that we should turn off the heater. You don't get a free pass on insulation just because the heater is on; do a control volume analysis with heat flow in from the burner and heat flow out by conduction through the walls. This is A*k*(T_water - T_room)/d, where Ak/d is constant, so heat flow is just proportional to the temperature difference. Blah blah blah conservation of energy, so this equals the heat flow in from the burner at steady state. More energy from the burner the higher the temp is held.

Same idea approached differently: you can show how the integral of heat flow out the walls over any given time T is less if the tank is cooling down than if you keep the temp up.

>>	Anonymous Sat Mar 14 03:05:25 2015 No.7128972 >>7128965 >conduction through the walls you mean convection. also k isn't constant, it varies with temperature, but that doesn't even matter because it's not conduction you're worried about

Anonymous Sat Mar 14 03:09:10 2015 No.7128974

>>7128972
Nope, I mean conduction. Through the walls of the water heater. And k is either basically constant or increasing with temperature anyway, which wrecks the insulation even further and supports my point even further.

http://en.wikipedia.org/wiki/Thermal_conductivity#Temperature

>>	Anonymous Sat Mar 14 03:10:11 2015 No.7128975 >>7128974 >Through the walls of the water heater how do you think the heat gets out of the heater. convection.

>>	Anonymous Sat Mar 14 03:12:10 2015 No.7128976 >>7128975 How do you think heat travels through solids?

>>	Anonymous Sat Mar 14 03:14:37 2015 No.7128981 >>7128976 applying an energy balance to the surface of a furnace/heater there is no conduction, only energy generation in heating the tank, and energy loss via convection

>>	Anonymous Sat Mar 14 03:14:46 2015 No.7128982 >>7128976 Public transit.

>>	Anonymous Sat Mar 14 03:17:12 2015 No.7128984 >>7128981 The energy balance is on the water. Sure, heat convects away from the outside walls, but it conducts from the hot water inside to the outside surface of the water heater. The conduction is the limiting function.

>>	Anonymous Sat Mar 14 03:22:05 2015 No.7128989 >>7128984 no because the inside of the heater is hot just like the water. it's the outside that's cold. and regardless of where you do the energy balance, the heat flux is going to be the same

>>	Anonymous Sat Mar 14 03:25:06 2015 No.7128992 >Telus Canadian detected

>>	Anonymous Sat Mar 14 03:30:31 2015 No.7128998 >>7128989 .... Yeah, so there's a temperature difference from the inside to outside walls of the heater, inducing... conduction. Which was my point. In the first place.

>>	Anonymous Sat Mar 14 03:33:12 2015 No.7129000 >>7128998 which is minimal and doesn't even come into an energy balance. conduction is not a factor in this problem at all

>>	Anonymous Sat Mar 14 03:35:49 2015 No.7129004 >>7129000 What the feck dude? Then where the heckerooni does all the energy go when the tank cools? This is assuming no water is being used. You gotta learn some heat transfer, man

>>	Anonymous Sat Mar 14 03:36:25 2015 No.7129005 Turning off the heater does save energy. Kind of sad that some people on /sci/ don't understand that. It doesn't save that much money though, it's probably not worth the inconvenience of not having hot water on command.

>>	Anonymous Sat Mar 14 03:36:36 2015 No.7129006 >>7129004 out of the fucking tank via convection

>>	Anonymous Sat Mar 14 03:42:10 2015 No.7129012 >>7129006 Convection... Through the wall? You need a fluid to convect the heat away, you're not making any sense

>>	Anonymous Sat Mar 14 03:45:46 2015 No.7129015 >>7129012 from the wall to the outside you mong

>>	Anonymous Sat Mar 14 04:26:31 2015 No.7129029 >>7128982 Underrated post.

>>	Anonymous Sat Mar 14 05:06:41 2015 No.7129048 >>7128749 I am confused. I have a furnace for heating my home that uses oil to heat water and I have a separate hot water heater. Running hot water from a faucet has nothing to do with my furnace. Is there like 2 in 1 units or some shit ?

Anonymous Sat Mar 14 06:30:22 2015 No.7129104

>>7128749
it depends how fast the tank loses heat and how much water is in the tank. First semester physics will let you calculate how much energy it takes to heat up X amount of water from some temperature to another, and how much energy it takes to sustain the temperature given the rate at which it loses temperature. At that point you just need to figure out how much time it would spend if it was off, and how much energy you would gain or lose by doing so.

Anonymous Sat Mar 14 08:09:51 2015 No.7129198
File: 13 KB, 511x399, 2015-03-14_20-08-13.png [View same] [iqdb] [saucenao] [google]

>>7129015
Not that dude, but I think this is the point you're trying to make?

I get that the k value is extremely small, but you should really put some effort into illustrating your point like a gangstangineer, instead of trying to word it out.

>>	Anonymous Sat Mar 14 08:33:58 2015 No.7129215 >>7128935 >the point of a heating system is to lose heat into the radiators, so insulation is what? Defeating the point of the system. you are retarded heat lost to the boiler room is not useful work done

Anonymous Sat Mar 14 09:02:48 2015 No.7129235
File: 7 KB, 200x182, 1382242243029.png [View same] [iqdb] [saucenao] [google]

>>7129104
To expand in this, this can also be solved by taking some simple as fuck measurements.

How engineers would initially (assuming a non-similar model) usually look into this is...

1. Record how fast the temp loss from highest heater temp to surrounding temp. From the temp difference alone, you can get a Q (heat transfer) value. From the time, we have the rate of energy lost to surrounding, which is also the power needed to be provided by the heater to COVER BACK this drop in temp. Then, just scale the values into a per hour basis (easiest time unit for this case) for continuous operation. That will be your Q_cont.

2. For a comparable value, record the time taken to bring the heater from room temp all the way to the arbitrary "comfortable high temp" value. Here, we have the Q required to bring it up to the required temp , as well as the time required for it (noted as t_max).
Therefore, the heater power used for this method, Q_timely would be:

Q_timely = Q_cont*(24 - t_turnedoff) + Q_turnon*(t_max)

Where t_turnedoff is the length of time you would leave it off.

Is Q_timely > Q_cont?

If it is, you save more. Is it less? If it is, just leave it on all the time.

The equation is flexible, since you can make it into 61320 hours, to see if you would save money in the long run for a year.

For a more complex model, some diffEQ is needed.

THERE. A POST THAT DOESN'T CLAIM TO BE SMARTER/MORE KNOWLEDGEABLE, AND SHOWS THE STEPS FOR MODELLING THIS SHIT.

>>	Anonymous Sat Mar 14 09:34:29 2015 No.7129259 >>7129235 >THERE. A POST THAT DOESN'T CLAIM TO BE SMARTER/MORE KNOWLEDGEABLE, AND SHOWS THE STEPS FOR MODELLING THIS SHIT. You did it, anon... you really, really did it.

>>	Anonymous Sat Mar 14 10:08:02 2015 No.7129295 >>7129259 That's because engineers get shit done rather than whining about it like scientists do.

Anonymous Sat Mar 14 10:16:35 2015 No.7129304

>>7129235
The energy required to leave it on all the time can never be less then the energy required to heat it up from an off position. It violates thermodynamics, bro.

In the case of gas powered heaters there would always be a monetary gain for turning the heater off at night, because eventually the heater will run at least once overnight and that energy would be wasted. We're talking pennies though.

In the case of an electric heater, you would actually have more monetary gain by running the heater at night and turning it off during the day, as electricity is substantially cheaper at night time.

In short, the dude turning off the heater at night is a little bitch because fuck you if I wake up and have a cold shower.

Anonymous Sat Mar 14 10:28:55 2015 No.7129321

>>7129304
>The energy required to leave it on all the time can never be less then the energy required to heat it up from an off position

I... never said it would? Why did you ever try to equate Q_turnon with Q_cont?

>In the case of x...
>In the case of y...

This does not take into account tariff during different periods of the day. Hell, it doesn't even take into account costing. It just takes into account rate of energy transfer. It's very bare-bones, and simplistic. Seeing the conversation in this thread, I thought I really needed to dumb it down to that point.

>>	Anonymous Sat Mar 14 10:33:57 2015 No.7129330 >>7129321 You said: >If it is, you save more. Is it less? If it is, just leave it on all the time. How could it ever be less?

>>	Anonymous Sat Mar 14 10:35:13 2015 No.7129331 >>7129330 Q_cont being less than Q_timely. Not Q_turnoff.

>>	Anonymous Sat Mar 14 10:45:28 2015 No.7129348 >>7129331 When you say: >Is Q_timely > Q_cont? >If it is, you save more. Is it less? If it is, just leave it on all the time. It reads "Is Q_timely less then Q_cont". Which is not possible.

>>	Anonymous Sat Mar 14 11:20:05 2015 No.7129397 >>7129348 Notation. Q_timely =/= Q_turnoff. Q_timely = Power usage to continually keep it at max temp + Power usage when you bring it back up from off temp With some time values in between, of course. You know how simple notations work, right?

>>	Anonymous Sat Mar 14 11:29:59 2015 No.7129417 >>7129397 <span class="math">\mathfrak{If\ there\ only\ was\ a\ way\ to\ write\ fully\ formatted\ equations\ on\ /sci/\ ...}[/spoiler]

>>	Anonymous Sat Mar 14 11:32:22 2015 No.7129423 >>7129417 Not used to latex, I'm afraid. I've only been using SimPy for my symbolic and numerical solvers. Excel for quick and dirty cals.

>>	Anonymous Sat Mar 14 11:52:00 2015 No.7129447 >>7128749 Obviously the greater the temperature difference between the tank and its surroundings the faster it loses heat, so yeah hes a tard.

>>	Anonymous Sat Mar 14 11:54:08 2015 No.7129449 >>7129447 So leaving the power/gas on is worse in literally every scenario except when your desired temperature is room temperature in which case your plumbing might be hurtin and you should call Burton

>>	Anonymous Sat Mar 14 14:36:11 2015 No.7129682 >>7129449 >So leaving the power/gas on is worse in literally every scenario except ...the usual use-case, in which you want hot water to be available on demand, without first waiting for it to heat up.

Anonymous Sat Mar 14 14:40:39 2015 No.7129702

Consider the possibility that the heater has a low-efficiency, high-output mode, used when the hot water tank is far below its operating temperature, so it heats the water faster but sends a larger proportion of the total heat generated out the chimney.

>>	Anonymous Sat Mar 14 14:53:00 2015 No.7129747 >>7128755 That smiley Be more passive aggressive, faggot.

>>	Anonymous Sat Mar 14 14:59:33 2015 No.7129762 I honestly thought you were a girl for a second. (It's because girls are generally more stupid, on average.)

Anonymous Sat Mar 14 15:55:29 2015 No.7129866

>>7129702
It doesn't.

Basically at this point I've made my mind up. She's a retarded women's studies grad who thinks "duh if duh watur stay hot it easier 2 stay hot".

And to all the faggots that claimed thermal inertia, that applies to ALL heat change, both negative and positive, since it's a CONSTANT. There is LITERALLY no way you could be using more oil to heat up the water tank unless it literally uses more when the water is colder, but this isn't the case because the speed at which the furnace heats the water is uniform, just like 90% of furnaces.

And newton's law of cooling does apply. It just doesn't make that much of a difference.

All in all, it uses less oil, but the difference is only marginal.

I'm still right though. And I updated my response to be less cheeky.

Advanced search
Text to find
Subject [?]Search by post subject. Leave empty for any.
Username [?]Search for user name. Leave empty for any user name.
Tripcode [?]Search for tripcode. Leave empty for any.
Email [?]Search by email. Leave empty for any.
Filename [?]Search by image filename. Leave empty for any.
From Date [?]Enter what date to start searching from. Format is YYYY-MM-DD
To Date [?]Enter what date to start searching until. Format is YYYY-MM-DD
Image hash
Search in	All Posts OPs Only
Deleted posts	Show all posts Show only deleted posts Only show non-deleted posts
Internal posts	Show all posts Show only internal posts Show only archived posts
Order	New posts first Old posts first
Capcode	All Posts Only by Users Only by Mods Only by Admins Only by Developers
Results	Posts Threads
Action	[ Simple ]

/sci/ - Science & Math