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I can think of three ways you could solve this problem: Insulate the device Add thermal mass to the device, e.g. make the case overly large and dense. Use some kind of cooling system, like a simple coil of tubing inside the device with coolant circulated through it. Insulation and thermal mass will slow the rate of heating. If the device has a finite ...


4

Insulating against thermal conduction can be represented as an R-value because it is a linear calculation. I can add two or more R-values together and I will see a linear benefit. Insulating against thermal radiation is more complex: You can't add two radiation barriers and get one that is twice as good. Insulation is based on the temperature of the barrier ...


4

The reason your utility company recommends to let the sunshine in is not to save on lighting energy. it is to take advantage of solar radition energy. a window can let the solar radiation in two ways, direct radiation and scatter radiation. The calculation of radiation energy has to do with many factors such as the geographical altitude and azimuth of the ...


3

If you really want to use the copper pipe, insert a thin strip of closed-cell foam into the length of the pipe. The ice expansion will crush it rather than the pipe, and unlike leaving an air gap, it will remain positioned along the entire interior. But this might actually be an instance of "the X Y Problem". One possible alternative (I'm sure there are ...


3

As a practical and cost effective solution, I'd advise using aluminium foil, or tin foil as it's also called. Please realise that it's rather fragile, so it's best to glue it to a plastic foil or something to keep the wind from ripping it apart. It doesn't really matter if cracks get in the foil. Use the most shiny, reflective side of the foil as the outside....


3

The aluminum can barely support itself at 400 C."Lightweight castable" refractory ( can be handled like concrete) should do the job; but you would need to find a supplier .It is what a petrochemical or power-plant might use . Portland cement/concrete type material will not tolerate temperatures of 400 C. Johns-Manville and Harbison-Walker made product like ...


3

No, it's not meaningful to express it as a ratio. The best insulation is deep insulation everywhere. You also need to consider convection losses, and your ventilation strategy. The attic is usually targetted first, for a combination of several reasons. It's cheap, it's easy, and heat rises, so thoroughly insulating the attic cuts down a lot of conduction ...


3

I'm assuming that you want to know why we use the heat capacity at constant pressure, $c_p$, instead of at constant volume, $c_v$, in analyzing heat exchangers. The main reason is that the pressure drop through most heat exchangers will be minimal, so a constant-pressure assumption works well. This is especially true for liquids, whose thermodynamic ...


3

I expect the same material as the coils would be the easiest answer ; nichrome ,Inconel ( 600, 601 or other number) , chromel. There are small differences but any one you can find would be good. That would also be practical as it would be readily available to the manufacturer. Stainless like 304 will probably work but I am uncertain of the many cycles into ...


2

Plastics have a thermal expansion rate of approximately 5 to 10 times that of metals. The PTFE will expand the most and the brass expansion is about 50% more than a steel heater, so the assembly will get looser. Here is a link to a chart of linear expansion coefficients. For a 9.5 mm part with 80 °C temperature change, the steel extends .0082 mm, brass ....


2

To borrow from a certain Brit physician, "I think it's a bit more complicated than that." For example, you could build/buy a double-walled box with a vacuum between the layers. That's esssentially what a thermos bottle is; there are varieties of drinkware that are built this way. But if you were to build a double-walled glass enclosure that's not ...


2

Attics are much hotter than the outside air when the sun is shining on them (say 120F in an attic). When the air conditioning system is running the internal air temperature is less than the outside (lets say 72F in the house and 85F outside). The ceiling temerature might be warmer than the floor, but both will be much cooler than the attic (say 73F for the ...


2

in the summer, the outside of the house- especially its roof- is hotter than the inside of the house. In this case, attic insulation does not physically "cool" the house- it just impedes heat transfer from the attic to the inside of the house.


2

First off, the design problem is not trivial and it looks like you have done your homework. On high temperature, small vessels like this you need to consider the 3 dimensional transfer of heat (the wall area is increasing as you move out). Or you can be conservative and much more easily calculate it with all the insulation acting at the outside dimensions. ...


2

First I recommend you use mineral wool or ceramic wool instead of fiberglass as they are rated for higher temperatures. Material Temperature Glass wool 230 - 260 °C Stone wool 700 - 850 °C Ceramic fiber wool 1200 °C https://en.wikipedia.org/wiki/Mineral_wool Second, using insulation to separate the aluminum and resistance heating wire is not a ...


2

have you considered firebrick, a product designed to be used in high temperature kilns, for example? It's light weight and easily cut with ordinary hand tools. It may not tolerate severe compression, but should bond well with aluminum and high-temperature adhesive.


2

I don't have experience with ICF houses specifically, but I do have experience with specifying concretes for outdoor use with significant frost exposure, so that is what I am basing my answer on. If you choose the concrete recipe well, 50 years should not be a problem. And with small repairs now and then, neither should 100 years. This is no worse than ...


2

This question can only be answered after many tests as to the convective properties of the box, it's geometry with respect to the geometry of the void, ignoring radiation. Because convection which is going to be the major heat transfer mechanism is basically a complex movement of air flowing up in a widening plume, and losing its temperature. Here is a link ...


2

If I get you right, there is a box having a small device that dissipates 30 Watts of heat continuously into the air. The air is blocked into a box, no way in or out. There are no fans/blowers trying to cool the device itself nor circulating the air inside the box. The size of the box is to be defined and the air temperature inside the box has to be figured ...


2

In order to assess the efficiency you need to compare the heat transfer rate $\dot{Q}$ with and without blinds. There are a few studies comparing the effect of blinds (internal/external/enclosed) on heat transfer. One of them in 2014 Effect of the roller blinds on heat losses through a double-glazing window during heating season in Central Europe, found ...


1

The best ice cream is made with the outside bucket temperature below 0 oC. See this link https://www.icecreamnation.org/science-of-ice-cream/. The common approach is the tried and true method to use ice and rock salt in the outer bucket. When you want to make a bucket-in-a-bucket, use a liquid with a freezing point below 0 oC. You could use tips from the ...


1

Radiative heat transfer will be quite high in a house fire, so not every construction made for 100°C temperature differences will be applicable here- look for constructions that have glowing-metal temperatures to contain (ceramics ovens...), and reverse the design to work for heat applied from the outside. Also put something with high heat capacity (water is ...


1

Don't consider this as an answer, but since i can't post a photo in comments, here i post it, i generated this diagram using CES, level two, i marked the most suitable and accessible materials. The disadvantage of all the materials here, is that they are brittle.


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Imagine the system below at equilibrium. The energy balances are as follows: At the ball ... $$\epsilon_b T_b^4 =\epsilon_w T_w^4$$ At the wall ... $$\epsilon_w A_w \sigma T_w^4 = h_a A_w (T_a - T_w) + \epsilon_a A_w \sigma T_a^4$$ In these balances, $\epsilon_j$ are emissivities, $A_j$ are areas, $\sigma$ is the Stefan-Boltzmann constant, $T_j$ are ...


1

White and silver are the most reflective (not absorb heat from the sun). There is some debate about which is more reflective. A white tarp is probably going to be cheaper.


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I would suggest a reflective mylar film such as those used for survival blankets. That would be the most effective single layer solution. Adding additional layers of plastic would further insulate the ground from the warmer air in the tunnel.


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You need to investigate the flammability properties of the insulating materials : wood can be a good insulator if it is dry, but it burns well etc.


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There are a lot of things wrong with the demonstration, including: The temperature of the heat gun isn’t relevant - to measure the R value you need to look at the temperature difference across the window, not from the heat gun to the far side of the window. Kind of like calculating the heat loss through your walls based on the outside temperature and the ...


1

A project makes economic sense when the return from the project exceeds the rate you can borrow money at. Usually we want a fairly large return before we concern ourselves with the project however. Lets say we want a 3 year break even or 33%APR. All aspects of that project should target that rate of return to be optimized. To calculate this you first ...


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