Questions tagged [humidity]

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How does the temperature and humidity of air affect the water consumption of a humidifier?

We can model the water consumption $\dot{m}_{w}$ of a simple humidifier using the following equations: \begin{align} \eta_{hum} & = {T_{db,i} - T_{db,o} \over T_{db,i} - T_{wb,i}} \\ h_{o} & = ...
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32 views

How to calculate Water Vapor Pressure?

So, we know that $$\text{Relative Humidity(%)}=\frac{\text{Actual Water Vapor Pressure}}{\text{Saturation Vapor Pressure}}$$ Now, we can find saturation vapor pressure only from the ambient ...
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Amount and percentage of water in air

I was wondering about the relationship between the amount of water in the air, and the percentage. Is the following correct? Let's take an example of 20⁰C. According to this page air at that ...
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1answer
26 views

How exactly does a (capacitive) humidity sensor work?

How exactly does a humidity sensor work? For example, how can it differentiate between a relative humidity of 30 % and 35 %? I know how a capacitance works but for me that principle is way too high ...
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How does humidity affect the dielectric constant of a material?

I'm trying to figure out how a humidity sensor using a Capacitor works, and every document I have managed to find seems to come to the conclusion that an increase in humidity causes the capacitance to ...
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32 views

Quickest way to dry wet floor

I have spilled around one liter of water to wooden floor. I'm afraid wood will deform and pop out. What would be quickest way to dry it? I have wiped out what I could, but some water passed between ...
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2answers
79 views

Why is cold air drier than warm air?

I know this has been asked before but i could not understand the replies. If someone has a simpler answer please do so. My simple Geog lesson just said that warm air molecules are further apart ...
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1answer
15 views

Relative humidity problem: definition of specific volume in terms of kg dry air

I'm working on a thermodynamics problem which is as follows: "Saturated humid air at 200 kPa and 15C is heated to 30C as it flows through a 4-cm diameter pipe with a velocity of 20 m/s. Disregarding ...
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How to calculate moisture content from relative humidity values?

I want to know the soil moisture content. However, these moisture probes are expenive. Instead, I have a relative humidity data logger that I want to use for the soil experiment. How can I obtain the ...
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1answer
33 views

To calculate the dewpoint ºC increase in a compressed air line

Good afternoon, I am really not a physics guy but I am trying to calculate the effect that pressure has in the dewpoint value. So I have a machine that refrigerates atmospheric air and dries it. ...
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30 views

How does a shower contribute to the humidity inside a bathroom?

I would like to know the exact process behind the humidity in a bathroom increasing due to a hot/cold shower.
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13 views

What's the speed of change of the relative humidity of air inside a greenhouse [closed]

The propagation speed of air humidity is an important variable affecting climate and sanity inside a greenhouse. High relative humidity of internal air is a typical phenomenon of many greenhouses ...
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58 views

What is the purpose of hollow tubes in the Regnault's hygrometer?

Regnault's hygrometer (a type of Chilled mirror dew point hygrometer) is a device used to measure the relative humidity by determining the dew point of the surrounding medium. The following quote ...
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51 views

Does heating an air permeable container affect the dew point inside it?

I know that the dew point is only affected by pressure and amount of water in the air so temperature should not affect it. However, I was wondering about a situation where there was a container with ...
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1answer
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Why does pepper not stick to the glass with print inside my pepper shaker?

So I have this pepper shaker made of glass with a print on it: One fine dinner, it ran out of pepper, so I opened the lid to fill it up and noticed a peculiar thing – small particles of pepper dust ...
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Moisture diffusion in air

Moist air is less dense than dry air. Additionally hot air is less dense than cold air. If we have moist hot air packets above dry cold air packets. How can the mixture of these air layers be ...
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4answers
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Preventing fog inside snow goggles

I understand that goggles fog up because of a rapid temperature change. In other words, goggles that have been sitting on a table outside (i.e., are very cold), when you put them on your face which ...
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What is relation between Absolute humidity and frost formation?

We see frost formation on our car glass when ambient temperature is really low. I believe this frost formation comes from water vapour from the air. So should there be more frost formation with ...
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1answer
182 views

Why is sound attenuation greater in dry air than humid air?

I have just learned the surprising fact that the attenuation coefficient of sound in air depends strongly on relative humidity: at any given frequency, it can be several times larger in very dry air (...
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2answers
104 views

Estimation of relative humidity

Assume that we have a box of $1\ \mathrm{m^3}$ with a constant wall temperature of $15\ \mathrm{^\circ C}$. The box was filled with air. The temperature of the air was $30\ \mathrm{^\circ C}$ and the ...
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1answer
54 views

Heating outside air - how much humidity can it take?

I am trying to figure out this problem - maybe it is simple for someone of you but I can't figure it out. I have known variables of outside air temperature and relative humidity (RH), I am taking ...
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1answer
73 views

How does sweat evaporate even when the relative humidity is 100%

Recently I entered a room at my workplace with sweaty clothes.The thermostat read 5°C and the humidity was 100%.The outside temperature was close to 20°C.Also the AC was switched off.In about ten ...
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Vacuum test in the laboratory

If I put some water in a plastic container and apply a vacuum pressure of -0.20bar the water comes out of plastic container which should not as per design and material of container. This is called ...
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3answers
64 views

Warm or cold air

Which air can be used to dry out food or clothes? Warm or cold air? I've read that keeping food in the fridge makes it dry out. Blowing hot air to the hair also dries the hair out. I'm confused.
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How does my body temperature stay lower than ambient air temperature if it goes over 37°C?

I know it's because of sweat, but why should the sweat over my skin get heat from the body, cooling it under the ambient temperature, instead of getting it from the hotter air all around me? If I ...
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0answers
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Doubts on conductor and insulator

I read on Stephen Gray's discovery of conductor and insulator. From that I came across a question that how cork, wood, rope can act as conductor being an insulator but then I got the answer that it is ...
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1answer
585 views

How does an ultrasonic humidifier / atomizer affect temperature?

Evaporative cooling is a technique used to cool air by using the evaporation of a liquid. My google research on evaporative cooling shows a ubiquitous concept of forcing air through a pad/membrane/...
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1answer
232 views

(Why) does wet air contain more oxygen?

I've heard the fact wet air contains more oxygen is the reason experts recommend to humidify the air. Intuitively, I'd say wet air should contain water of a greater density and thus, make less space ...
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3answers
57 views

Blowing smoke out of the clean air - can someone explain?

Yesterday my wife and I were out walking. The weather was cloudy and humid (it had been raining a few hours before). Around 15 C. Suddenly, with no apparent reason, both of us had smoke coming out ...
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77 views

Is there an effect on condensation when the elevation is changed?

So, I'm working on a test for a project and we want to see if any condensation occurs. The relative humidity temperature are fixed. From this we can find the dew point, which will give us a good ...
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Understanding relative humidity

I am having some trouble understanding relative humidity. If I have a vacuum chamber in which I place a hygrometer to measure relative humidity. In case I am able to achieve full vacuum, will the ...
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2answers
82 views

How to achieve a desired relative humidity in a sealed environment

I need to find out how much water to add (in milliliters) to a sealed test tube (which has a volume of 53 milliliters) to achieve a relative humidity of 60% when the temperature is heated 80 degrees ...
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2answers
258 views

Relative humidity, definition and its dependence on state variables

Relative humidity ($RH$) is defined by the following equation: $$ RH = \frac{p_{vap}}{p_{sat}} $$ Where $p_{vap}$ is the vapour pressure and $p_{sat}$ is the saturation vapour pressure. VAPOUR ...
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1answer
336 views

The minimum temperature that water can reach at a cooling tower

I have read this sentences at a paper and I can't understand the reason: Consider a cooling tower and read the following sentence: "When the water enters hotter than the air, the ideal condition ...
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1answer
357 views

Why do we sweat on a hot and humid day but the clothes are able to dry?

I know that on a humid day,water vapour content is high in air and as a result evaporation of sweat is lesser and hence we feel hotter. What I am not able to get is, if water vapour content is high,...
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26 views

How is steam affected by a fan?

Scenario Consider a humidifier with a fan behind it. Assume same room, moderate temperature, low fan speed. ...
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3answers
2k views

Will water in a vacuum evaporate continously?

Will a vacuum chamber that is maintained at 0.1 Atmospheres with an open water container inside ever reach 100% humidity of the remaining air, so that no more water evaporates or will water ...
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1answer
1k views

Does dew point change with change of ambient temperature?

I know dew point is the temperature at which air becomes saturated with vapor that was already in the air. So if I take some unsaturated air in a container and lower it's temperature, eventually at ...
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1answer
39 views

Diminished receptivity of paper to pencil during periods of humidity

Why does paper become less receptive to pencil when it is humid out? I have generally experienced this with a 4B pencil.
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2answers
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Why Does Charging and Discharging Happen in Low Humidity, but not High?

If one rubs a neutral glass rod with cat fur will cause it to have excess negative charge in low humidity, but not in highly humid conditions. Why not? How does the water neutralise the rod? Why ...
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Closed System Pressure Rise due to temperature & relative humidity

Consider a closed system E.g. a lighting wellglass equipment like this: (Why this is a closed system? Because it is made air-tight through use of sealants - which seals the two components - an ...
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1answer
2k views

How to add the relative humidity percentage to molar mass of air?

The higher the relative humidity percentage, the higher the molar mass of air, right? So then how do I add the higher amount of water in the air to the molar mass of air? For example, let's take a ...
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253 views

Can water boil at 100% absolute humidity?

The definition of absolute humidity is the amount of water that can exist in solution with air as a gas. My question is, in a closed vessel that contains a flask and a burner or heat source below it ...
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how to influence RH and air presure to resistance of air

For example higher RH (relative humidity of air) provide lower air electrical resistance. But how I can calculate with this relation? Moreover air pressure (between 1500 and 500 hpa) can influence ...
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2answers
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Does air have to be oversaturated in order to make resublimation possible?

I am writing a pre-scientific work about the chemtrail conspiracy theory. A part of that is the exact process of contrail formation. There is one more puzzle piece missing. Hopefully the answer to ...
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3answers
206 views

Where is humidity?

During hot and humid weather, we sweat incessantly due to high humidity. But when we sit under a fan, we feel cold and comfortable. Why do we feel cold and chilled? Why don’t we feel the humidity?
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Why doesn't the moisture freeze out of the air when the air temperature is below freezing?

I would think that there would be zero humidity outside right now and it's 21 degrees. The weather site says there is 71% humidity.
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Propagation speed of air humidity

I'm currently playing with relative air humidity and temperature sensor that makes measurements in my living room once every 60s. When plotted the data on a chart I noticed that spikes and dips of ...
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Efficiency of a dehumidifier with respect to temperature [closed]

I have just bought a dehumidifier to decrease humidity in my bedroom. I'm wondering if it takes more energy to work (assuming same liters of water condensed) in winter with cold temperatures or in ...
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3answers
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What law or formula discusses the relationship between pressure and dew point?

A lot of times, dew point is focused primarily upon temperature and relative humidity. However, that same point of saturation is affected by the pressure, but I can't find a formula, or law even, that ...