# Tag Info

37

Trees increase the turbulence of the air that reaches the turbines. That creates all sorts of uneven, rapidly-shifting loads on the blades and structure. That increases the maintenance costs, decreases availability, decreases the capacity factor, and decreases the life expectancy of the turbine. So, higher costs, lower revenue. One of the ways we measure ...

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Adding more fuel doesn't permit an arbitrarily high combustion temperature because of an unavoidable intrinsic limitation: The reaction has to heat its products. (In the case of wood, this is mostly carbon dioxide and water.) In the most efficient flame, we might mix the reactants in perfect proportion and eliminate heat losses as best we can, but we can't ...

15

If furnished in a thin, polished sheet, aluminum will reflect infrared radiation, as for instance in a so-called "space blanket" which consists of a thin sheet of plastic on which a thin and smooth layer of aluminum has been deposited. In this context, the aluminum can prevent heat losses by reflecting infrared radiation. But if that thin sheet of ...

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

There are a lot of questions in your question, and it should probably be broken up into multiple different questions. I don't want to wait until that happens though so I'll address the ones that I know the answers to. How is heat converted to an electrical signal (current or voltage)? A microbolometer is just a special case of a bolometer which ...

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

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If you can replicate what you report above under controlled conditions then you can retire for life next year. Really. The overwhelming opinion by all reputable test houses or suitably competent careful and honest individuals is that for combustion improvement by treating the **fuel* with magnets you'd be just as well off rubbing on snake oil - or drinking ...

10

In a similar vein to my answer about calculating the lever force in a continuous situation; you need to use integration. You start by taking the standard heat law that you are familiar with $$\Delta Q=c\ m\ \Delta T$$ and replacing the $\Delta$s with differentials: $$dQ=c(T)\ m\ dT.$$ This new equation reads: For an infinitesimal (very tiny) change in ...

10

Yes, there are indeed combined PV-T (photovoltaic-thermal) hybrid panels that turn some of the incident light into electricity, and have a circulating fluid and heat exchanger to put some of the heat into a heat store. There's very little take-up of them, because they're just not economic in most circumstances. The theory looks great: PV panels are more ...

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: $$\frac {2 kW}{500 kg}\cdot\frac{1 kJ/s}{1 kW}\cdot\frac{0.24 kJ}{1 kcal}\cdot\frac{0.24 K\... 9 I am guessing, you are solving the following system:$$\partial_t T = \alpha_i \partial_x^2 T$$with \alpha_i=\kappa_i/\rho_i c_{p,i} for material i, subject to the conditions:$$T\left(x,0\right)=T_\infty\quad T\left(0,t\right) = T_h \quad -\kappa\partial_xT\left(L,t\right)=h\left[T\left(L,t\right)-T_\infty\right]$$Now you can approach simulating ... 9 I agree with Chemodynamics, and I will try to add a different perspective (or maybe two). The fire process is a process where you add a fuel (i.e. energy in the system), and that fuel is gradually consumed. The rate at which it is consumed releases the chemical energy. An interesting thing here is that: the log is a three dimensional object the fire will ... 9 It really depends on what you are trying to do with it. And thermal "conductors" and "insulators" are not a hard and fast distinction in properties like electric conductors or insulators. Every material just has a certain thermal conductivity, so compared to say diamond, aluminum has low conductivity. With foil, wrapping it with air ... 8 Illuminate the room indirectly via dichroic reflectors at 45 degrees to each transparent wall. These will reflect light at 90 degrees (i.e. into the room) but allow the heat to pass straight through. (NB you may want watercooled heatsinks behind the reflectors, or some other adequate arrangement to dispose of the heat.) 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 ... 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 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, ... 7 Considering the three methods of moving heat: Convection - To keep the IP66 rating of the enclosure, you can't add any holes for exhaust fans. Radiation - At the temperatures that you are talking about, radiation will not be removing much heat. Conduction - This is a viable alternative since it could work through the walls of the enclosure. You can add ... 7 A simple approach would be to just consider the heat added. The specific heat equation gives the temperature change due to heating as$$Q=mc\Delta T where $Q$ is heat added, $m$ is mass. $c$ is the specific heat of the material in question (~1.005kJ/kgK for air at room temperature) and $\Delta T$ is the temperature change. A 5x5x5 cm box will have an ...

7

If a process is both isothermal and adiabatic, it is implied that the work done on the system is being stored somewhere other than the internal energy of the working fluid. (Or conversely, if the system is doing work, the energy is coming from somewhere other than internal energy.) The classic example of such a process is free expansion of an ideal gas (...

7

Heat pipes are very useful when you have limited space to work with or you want an entirely sealed and self contained unit. An interesting example of this is that heat pipes are used to cool the legs of oil pipelines which run through permafrost areas, the cooling is required to stop the heat generate by friction in the pipe and solar heating from ...

7

The efficiency of any radiator (heat exchanger) is a function of the temperature difference between the two fluids in question. All else being equal, a heat exchanger with a greater temperature differential will transfer more heat. Each radiator will have a temperature gradient across it. (Here I'm talking about how much the temperature of each fluid ...

7

Mainly cost difference. And also, a fan is sufficient for the job. The problem being solved is thermal stratification. That's caused by a lack of vertical mixing; the warm air rises to the top, the cold air sinks. Normally, there's quite a bit of movement in the first two metres or so from the ground - thermal stratification starts when the ceiling gets to ...

7

Because they're two completely different systems that have, in some circles, accidentally been given the same names. The things that are sometimes (particularly in the USA) called home geothermal systems are ground-source heat pumps. The energy for these comes from sunlight on the ground over the year. Electricity is used to move heat from a source ...

7

They are very nearly equal for typical four-stroke non-turbo diesels under load. A turbo diesel under load should have slightly more radiator loss than exhaust loss. At the bottom is a link to the technical spec sheet for a Cat 3412 powered genset. It's a probably a bit bigger than what you had in mind. It is a turbo with aftercooler (A/C in the doc below). ...

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 ...

6

This will depend very much on the heat flow around the enclosure. There is a thing called the H factor which describes the heat transport properties between a surface and a fluid. The value of H varies with surface properties and flow. So to do your calculation you need a few different assumptions. Let's simplify. 1) the air in the box is uniformly heated ...

6

Neither. In this sort of situation, there's no "simple" linear solution; you need to use integral calculus to add up the incremental heat absorbed at each temperature along the way. The only time that this calculation becomes a simple multiplication is when the quantity being integrated (the specific heat) is a constant over the range of the integration.

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Those two holes by themselves will have little effect. The pressure difference between the two ends of the holes will be so small that only a little air will flow. If you want to go thru all this trouble, then put a hole at the bottom too, with a fan that actively blows cold air from the bottom of the living room into the bedroom. Hot air will then find ...

6

Orientation does often matter. As Carl's answer mentions, the liquid can get from the condenser to the hot interface via capillary action, but most common heat pipes are designed assuming gravity will do the job. Capillary action is much more effective in space where there is no gravity, but produces very little flow when it has to work against gravity. ...

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