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# Absolute Humidity in Two Rooms

06/22/2014 7:35 PM

I have two bedrooms that are connected by a door. One room has a wall heater and the other has not.

If the door is open and the heater is power on, I measured the absolute humidity (AH)for both rooms. The AH1 of the room with heater is higher than AH2 of the room without heater.

This is because higher temperature air has higher capability to hold much vapour. I don't know how to verify it theoretically. Does anyone can help me? Thanks!

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#1

### Re: Absolute Humidity in Two Rooms

06/22/2014 8:33 PM
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#2

### Re: Absolute Humidity in Two Rooms

06/22/2014 10:51 PM

What is absolute humidity?

How do you measure it?

Get yourself documented with psychometric charts, apparatus, thermometer wet and dry bulb and/or black ball thermometer.

Relative humidity is expressed in %RH.

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#3

### Re: Absolute Humidity in Two Rooms

06/22/2014 11:41 PM

Absolute humidity is the total amount of water vapour present in a given volume of air (mg/L)

I measured the AH(mg/L), RH(%) and T(deg C) with a calibrated hygrometer.

I want to calculate how much vapour is transfer from one room to another at different temperature.

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#4

### Re: Absolute Humidity in Two Rooms

06/23/2014 1:23 AM

How do you know it transfers and does not simply condensate in the colder room?

It will be more complicated to calculate what you are trying to know!

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#5

### Re: Absolute Humidity in Two Rooms

06/23/2014 3:07 AM

The reality is more complex than the two temperature and two humidity measurements will to be usefully modeled. Temperature gradients between the source and sink. Where the temperature falls below saturation, water is removed from the air.

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If you have lower absolute humidity in the room that does not have the heater in it, the likely reason is that moisture is being lost to the colder walls of the room faster than air mixing with the warmer room replenishes the moisture.

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Sources of water, such as sinks, washing machines, toilets, live plants, or people, in the warmer area would accentuate the above effect.

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#6

### Re: Absolute Humidity in Two Rooms

06/23/2014 7:41 AM

Since there is no access to the rooms from outside, it should stabilize eventually!

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#7

### Re: Absolute Humidity in Two Rooms

06/23/2014 4:27 PM

You are right. Finally the two rooms should be thermal stabilized.

But if we keep T1>T2, is there any equation for AH1=f(T1, T2, AH2)? or we can treat room2 as infinite ambient.

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#8

### Re: Absolute Humidity in Two Rooms

06/23/2014 6:31 PM

A couple possibilities:

- 1. The absolute humidity in room two is lower because the the humidity in room one is greater than the temperature will allow, i.e. greater than saturation, at room two's temperatures.

- 2. The absolute humidity in room two is lower because water is being removed from the air in room two, as would be the case with water condensing on a cold window or increasing the moisture of a cold wall or an open container of calcium chloride.

- 3. The absolute humidity difference is due to something as of yet undescribed, such as the heater burns natural gas and does not vent to the outside and was just recently started, or bunny rabbits were recently brought into room one.

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If possibility #1, of room two being in a saturated condition, is the reality then AH2=f(T2) is a viable option. Furthermore, as long as there is reasonable air exchange and room two temperature is below room 1, minimum room 1 absolute humidity would be available from AH1min=f(T2, AH2)

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If possibility #2 is a reality then you would need to know how quickly water is being removed from the air and how quickly it is being add, if at all.

.

But really, both of those are gross oversimplifications, for a number of reasons. One reason is that a single temperature reading does not describe the temperature of the air in each entire room.

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#10

### Re: Absolute Humidity in Two Rooms

06/23/2014 7:11 PM

Here I provide the measured air parameters:

Room1: T1=34.9°C, RH1=25.93%, AH1=10.187mg/L

Room2: T2=23.0°C, RH2=43.40%, AH2=8.96mg/L

The air conditions were far from condensation. Also the heater in room1 is electrical heater. Because the room2 is very big, so it could be treated as infinite ambient.

I'd like to know the relationship between some parameters:

AH1=f(T1, T2, AH2); or AH1=f(T1,T2,RH2)?

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#11

### Re: Absolute Humidity in Two Rooms

06/23/2014 7:49 PM

So there are air conditioners in room 2?

Are you certain that air through the air conditioners is not reaching conditions for condensation? How have you verified this?

What types of walls, floors, ceiling are in room 2?

Are these spaces regularly or periodically inhabited by plants, animals or other things that would regularly change the humidity?

.

Unfortunately the measurements you note are not close enough to saturation to easily know something about what is likely driving the difference. Perhaps a more detailed survey of temperatures and humidity is warranted.

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#9

### Re: Absolute Humidity in Two Rooms

06/23/2014 6:37 PM

IMO it is important to know how close you are to saturation. In principle, if the air is moving, both rooms should measure the same %RH, since this is temperature compensated. i.e. relative to the saturation (100%)

Your situation will be different when working with dry air, since when there is not enough moist in the air, an equilibrium will not be attained. Here you will be "drying" the materials (walls, floor ceiling etc..) also more moist air will be attracted to the dry air and depending on how the rooms are build, or what is inside that can give a different moisture content for the time there is no stability yet.

You measure with lots of apparatus but do not tell us your findings. We are in a guess game this way.

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