# Tag Info

14

The possibilities of transforming heat into any other form of energy are limited by the second law of thermodynamics. Essentially, you cannot simultaneously lower the entropy in a closed system (e.g your house) by transforming heat into a different form of energy, and transferring heat from a colder object to a hotter one requires work, so that more heat is ...

12

Watercooled , if you don't count sewer as "outdoors".

10

Use a (largish) water tank. I've never seen a water tank used as a heat sink for an air conditioner, but they were used for stationary engines some time ago. Typical air conditioners can produce about 2 kW of heat. If that heat is released in a 500 litter water tank: \frac {2 kW}{500 kg}\cdot\frac{1 kJ/s}{1 kW}\cdot\frac{0.24 kJ}{1 kcal}\cdot\frac{0.24 K\...

8

Surprised they haven’t been mentioned yet because they seem to be all the rage in the spammy ads you see on a lot of sites, but depending (very heavily) on the general atmospheric conditions, an evaporative cooler (sometimes called a swamp cooler) might work. Evaporative cooling in general is based around the idea of latent heat of vaporization. In short, ...

8

Nobody specifically mentioned geothermal yet but this is exactly the principal used here. Rather than exchanging heat with the outdoor air, heat is exchanged with the ground a meter or two below the surface. I suppose one could make the argument that this is still "outside" but the heat does not make it to the atmosphere and if you have a heating/...

8

This question reminds of the concept of a heat bank, a form of heating I experienced in the 1970s. The type of heat bank I am familiar with consisted of a metal box which contained an electric radiator and large quantities of steel which were heated by the radiator. The concept was the radiator was energized during the night when cheaper off peak electricity ...

7

There are phase change materials (Similar to the cold pack for injuries) that at some point in time was the all the rage. Basically what they did was storing and releasing heat energy. However, they have a limited capacity. Figure: Phase change material in the form of a cold pack The idea is (or was because it never caught on) that the phase change ...

4

We need the pressure of the mixture to know the latent heat of vaporization, but since we are using 100 C, we'll assume it's at 1 atmosphere. Convert the liquid to steam using latent heat of vaporization. If your energy input isn't enough to turn it all into vapor, the final temp is 100 C. If you have energy left over it will go into the next step. Using ...

4

Heat can be converted to electricity only according to the second law of thermodynamics: you need in this case a hot reservoir and a cold reservoir. The heat engine takes heat from the hot reservoir and puts it into the cold reservoir. That's the way all heat-based electricity generation works. In gas-fired generation, the hot reservoir is very hot (it's ...

3

Edit 1 based on the current version of the question "Where can heat be vented from an air conditioner that isn't outside, in the attic, or into the ground?" Answer: It is possible to put the heat into something like a large water tank. The problem is that you have to take the heat out of the water tank eventually. This is the heat battery ...

3

When situated in the old industrial building, once we had a "cooling system" that was simply sucking in the air through the hole in the floor from the accessible there labyrinth of the industrial underground tunnels. I do not know how productive this would be in a large scale but worked well enough for a small server room, using electricity only to ...

3

This is because the valve timing is optimized for a certain RPM, which represents the design point of the engine. In the case of a piston engine for use in an airplane, the opening and closing of the intake and exhaust valves is timed for optimum performance (i.e., maximum work extracted from the combustion process) at 2400-2600 RPM, while on a Suzuki GS1000 ...

2

Copper sheet with an absorbing and poor emitting coating is available which is easy to solder copper pipe to the untreated reverse side. Guess why many flat plate collectors are made like this… As for spacing you can get full details from Duffie & Beckmann Solar Thermal Engineering (can’t remember exact title, but it is a really good book) but panels I ...

2

Your assumption that the force acting on the crankshaft for a given crank angle $δ$ is constant regardless of the rpm of the engine is false. A primary reason why this is the case is, unlike what we generally assume, the intake and exhaust valves don't open or close exactly at TDC (top dead center) or BDC (bottom dead center). The timing of the opening and ...

2

Answers to some of your queries: I bought this in a hardware store a few months ago and tried to use it in my car bc my AC would take 20 mins to cool the interior (98' F weather). Your car AC is faulty. The air was sortof cool but it seemed like it wasn't any cooler than what I had in my car and it said it works better when you freeze some of the ...

2

Theoretically? Sure. From a practical standpoint? No. At least, it's pretty hard to see that working in any feasible way. Regardless of what you do with the waste heat, you would need an inexhaustible supply of fresh air to cool the hot refrigerant. So the question is what to do with that hot air. As someone suggested, you could cool that with, say, ...

2

Tip: 'KW' is a kelvin-watt (which I don't think is useful for anything). Use 'kW' for kilowatt. (Capitals matter!) You could really simplify the problem by using the energy density of the fuel. If you look it up you should find that it's about 10 kWh/kg of petrol or diesel. 10 kWh/kg × 3600 s/h = 36000 kWs/kg = 36000 kJ/kg = 36 MJ/kg. My diesel VW does about ...

2

I think this will lead to an overestimation because you are assuming the load is 100% during the whole time (I would expect it to be somewhere 40 and 50% on average). Assuming 35 MJ/L, your calculation as it is would yield about 15 L per 100 km, which is too much. Given the average ratio of load, it would yield something between 7.5 and 6 lit per 100 km ...

1

Can you not simply take the miles per gallon value times the Heating Value of the fuel?

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