# Tag Info

17

A yahkchal is an example of a type of passively cooled building in Iran They utilise a combination of passive evaporative cooling and thick thermally insulating walls in order to keep the interior temperatures low enough. First, wind is directed into underground aquifers known as qanat. They are then cooled due to the low humidity desert air causing water ...

10

In dry/arid areas a wind catcher tower in conjunction with a qanat is a great way to keep buildings cool. The underground water stays cool and cools the air passing over it that is drawn in through the wind catcher. However, in a humid climate you would want to isolate the incoming warm/moist air from the cool underground water. You could pass pipes through ...

9

Insulation, shade, the use of low thermal conductivity materials and utilising any cool breeze at any time of the day are going to be key to passively cooling buildings in a hot climate. Different solutions will be more applicable to houses than non residential buildings. The other thing to consider is whether the climate hot and dry or hot and humid. In ...

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

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 ...

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. ...

5

You did not specify what materials you are working with and neither the dimensions. I made some assumptions. First of all, the coolant circuit is likely driven by a pump. Therefore you need to know the flow rate $\dot{Q}$ the pressure needed on the pressure side. You can get more information here. For your specific setup to cool the PSU you have pressure ...

5

Hopefully some helpful observations: Both fans have the same power rating Blade size differs I would have thought given the power rating this would equate to the smaller blades having a faster rpm, the larger blades can have a lower rpm for the same air flow. Rotational speed can be a factor in noise as faster generally equates to noisier, I say generally ...

5

Diurnal swings, i.e. temperature differences between day and night, are also an important consideration in hot climates. If the temperature at night drops to something acceptable, you can use night purge to cool a thermal mass (e.g. concrete slabs or walls, phase change materials if you'd like to get fancy). This works well together with a well insulated ...

5

The capacity of an evaporative cooler depends on the relative humidity. The lowest theoretical temperature that the cooler can reach is the wet bulb temperature. The wikipedia article has some discussion on the design and shows how it works with psychometric charts. For the design you'd look at a 'typical' hot day, compare wet bulb to dry bulb for that day ...

4

Farther from the equator, a passive house is mainly a very well insulated house with good exposure to solar lighting for passive solar heating. However in hot climate, one has to rethink completely the design. Here what matters more is the way you can use the night "cool" air to cool the house. Also you have to take great care to shading as best as you ...

4

The temperature of evaporated refrigerant gas is constant as a property of refrigerant material. And usually it is considerably below the thermostat setting in the controlled space. The design of the system relies on the circulation of cooled air and its gradual warming up to deliver the cool air at desired temperature so that it is still cool enough to be ...

4

A Peltier cooler would fit the requirements you set out. They can be compact enough to fit the 'wristwatch sized' requirement and use electrical power to achieve the cooling effect. You do still need some way of shedding heat from the hot side of the cooler and this may require either a passive heat exchange, heat pipe etc depending on the application. ...

4

What you first need to establish is your temperatures. Body temp min and max; ambient min and max. Select the worst case. Then take some guesses as to how much heat you have to pump. Is the vest insulated on the outside or does it have to cool the ambient as well? I would blind guess that you will need about 200 watts of cooling by the time you figure your ...

4

The pressure requirement could also be to raise the temperature at which the water boils. The boiling point of water depends on the pressure it's at; higher pressure raises the boiling point, as the following image shows. As you can see, water at atmospheric pressure boils at 100 C, but water at 3 bars boils at about 130 C. When water starts to boil, it ...

4

The air coming out of the fan will be highly turbulent, wheras the air being sucked into the fan is less so. Hence blowing at the target will increase heat transfer. On the other hand, if you are looking at a casing, a fan blowing into the case will also blow dust into the case. A fan blowing out of the case will typically suck in less dust, as the fluid ...

3

Based on the available data it looks like it will perform well: efunda.com - (4) Good, both for static and dynamic seals pspglobal.com - 1 = Recommended Temperature and additives may change this, however.

3

Factors determining fan airflow (heat reduction): Blade pitch. Blade shape and size. Motor power and RPM. In your case 3 is the same, 1 and 2 in the "newer version are bigger", so it will cool better. Main source of noise in fans is coming from the bearing and the electromotor (same in both cases) and from the blades which are slightly larger. ...

3

Just out of curiosity, if the enclosure is sealed what will an oxigen sensor measure. I would conduct the heat outwards via a metal structure. But cosidering the heat your sensor generates, I would reconsider the polycarbonate choice. Polycarbonate max operating temperature is about $115\,^\circ C$. A metal enclosure would conduct the heat much faster to ...

3

Since your enclosure is IP66 you can pour a steady stream of water over it to absorb and carry the heat away.

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I think it would depend on the enclosure. In an open environment, it would be better to blow cool air at the target. For closed cases, it seems more common to blow hot air out if there are not fans in both directions.

3

There is a big difference in the resulting flow during blowing and suction. Blowing creates a reasonably well directed jet of air, while suction pulls air from all around. Therefore blowing is better if you want to cool a small region or object (which is your case), because you can direct the flow there. In the case of two fans, I am not sure what the best ...

3

The key technical term you're looking for here is convective cooling. Either you allow the air to rise through the chimney on its own accord (natural convection cooling) or you pump it through with a fan (forced convection cooling). The second is obviously more effective at pulling heat out of the system. The amount of heat removed will be a factor of the ...

3

keep it under 30 degrees Celcius but everyday the temperature will goes above that No amount of ventilation when it's hot out is going to fix that. In fact, more ventilation will make that worse. Ventilation will only cool the warehouse when the outside temperature is less than the inside temperature. One way ventilation can help, if it's managed ...

3

No, this will not work well (as I read your plans). You should configure your fans (of any size) to draw air from inside the chassis and expel it outside the chassis. This will require vents on the perimeter of the chassis to allow air in. No 'blocking' is necessary except that the outflow face of the fan should be sealed around the outflow vent ...

3

The motors used in inexpensive, occasional-use appliances often do not have cooling fans in them because they are not designed for continuous operation. This means that cutting holes in the top case of your mixer might not help get the heat out of the motor windings- unless you added a fan for this purpose. That would be a time-intensive proposition, ...

3

There can be differences between ice packs, but in practice the differences seem pretty small, and you'll have a hard time finding hard data on different ice packs' cooling abilities. How much ice/ice packs cool is determined by three things: First, the specific heat capacity of a material tells you how much energy it takes to raise 1g of the material by 1 ...

3

All (car) radiators are parallel, it is the only way to get the flow rate and reduce the fluid velocity in each tube sufficiently to allow the time for heat transfer. However, some radiators are series parallel where each section is in series and the section has the small tubes in parallel. Not seen that in a car though. If you can carefully « extract » ...

2

Could you mount Peltier cooling units to the outside to pull heat out of the enclosure? I would think you'd want to have cooling fins inside the unit to increase the rate of heat absorption.

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