Questions tagged [humidity]

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1answer
19 views

How to maintain moisture on a substrate?

I know that different materials absorb water differently and dry differently. The simplest example is when washing clothes and putting them in the dryer they take different amounts of time to ...
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1answer
29 views

How exactly does air accommodate water vapor?

I would like to have clarity on how air accommodates water. When water vaporises, does the water molecules just squeeze into the space between already existing molecules of nitrogen and oxygen? From ...
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1answer
162 views

What does 'saturated' air actually mean?

I'm having some problem in getting an insight on what 'saturation with vapor' actually means. The question is asked in the context of atmospheric air becoming saturated with water vapor and beginning ...
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0answers
37 views

Coffee quality and temperature

The question is about adjusting the size of particles of coffee powder to temperature. It is said that properly grinding the coffee grains is cricual for making good coffee (I have an espresso ...
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1answer
18 views

Can someone point me in the right direction about isothermal compression process

I am reading book about compressors and I have a question about isothermal process and water condensation. Is it true that during actual compression process water vapor will condense? I was always ...
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4answers
398 views

Doubts related to speed of sound in different mediums

since childhood we have been taught that sound travels faster in solid (most dense) as compared to liquids (less dense). and speed of sound is greater in liquids as compared to gases (least dense), ...
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2answers
212 views

Why do fireproof safes “capture and hold in moisture”?

From The Best Fireproof Document Safe | Reviews by Wirecutter: Humidity can be an issue with these safes, as they tend to capture and hold in moisture, which can damage their contents. Someone ...
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1answer
36 views

Why adding fan to dry cabinet not improve dry performance? [closed]

My dry cabinet is basically rubber sealed cabinet with peltier module to condense moisture and drain it out. The drying process run quit slow from ambient humidity around 50% to 70% it take about 3 ...
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2answers
28 views

How can the moisture of a peace of wood can be reduced to below 10% if the surrounding air humidity is over 50%

This question just came to my mind and I hope this is the right Stack Exchange to ask it. How can the moisture of a peace of wood can be reduced to below 10% by storing it outside surrounded by air ...
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1answer
29 views

Calculating indoor humidity — do I need to account for pressure?

I'm developing a calculation that converts an outdoor temperature, pressure and relative humidity into an indoor relative humidity (for a given indoor temperature). E.g. if it's 39°F outdoors at 87% ...
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1answer
69 views

Why does humidity helps keeping heat?

When I turn on the AC to heat my living room, it usually takes a long time, but when I also boil some water in the kitchen(The rooms are connected), the living room heats very quickly. I ran a small ...
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2answers
46 views

Relative Humidity Problem

I have been assigned to solve the problem: the ongoing temperature of the room $T_1 = 7$; RH is 85% and I am asked to figure out how much the temperature must be increased in order that RH would drop ...
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1answer
44 views

What spreads faster - temperature or relative humidity?

Let's say you open a window. There is difference in temperature and relative humidity between inside and outside air. Which room quantity will equalize faster with the outside - temperature or ...
2
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1answer
32 views

What might cause water vapor to move against the flow of air in an enclosed space?

I have a rectangular tent that I'm planning to use as a mushroom fruiting chamber. It measures approximately 120 x 60 x 150 cm and has two duct fans installed--an intake fan near the top of the left ...
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0answers
59 views

Variation of dielectric constant (relative permittivity) of air with humidity or rain days

I would like to know a value of the air dielectric constant on a rainy day or the relationship of its variation to humidity. Thank you.
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1answer
21 views

How can I calculate vapor pressure from temperature and relative humidity?

I have a datalogger that records temperature and relative humidity in a room. Can I use that to calculate vapor pressure?
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1answer
90 views

Calculation of humidity ratio by vapor partial pressure

I've been looking around for a way to calculate the humidity ratio by the partial vapor pressure and the atmospheric pressure of the environment. I found a procedure for such calculation on ...
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1answer
25 views

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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2answers
647 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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0answers
18 views

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
157 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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0answers
57 views

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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0answers
35 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
225 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
61 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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0answers
42 views

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
49 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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1answer
32 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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0answers
17 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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0answers
52 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 ...
17
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1answer
245 views

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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2answers
113 views

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
1k views

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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1answer
356 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
167 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
55 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
85 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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0answers
27 views

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
216 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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1answer
200 views

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
51 views

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
1k 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
357 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
61 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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0answers
136 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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0answers
31 views

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
218 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
345 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
635 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
380 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,...