Heat transfer from an air current across a body of water

In summary, an expert summarizer of content provided the following: - an air mass is moving through a duct and over a water/air boundary; - the temperature of the air after it's moved parallel to the water boundary is dependent upon the variables of the air mass and the scale of the device; - the air may achieve 100% humidity if the duct is long and the flow rate is high.
  • #1
Infinitybyzero
33
3
Hello, I am looking for the general direction that I need to go to calculate the following:

The time-dependent change of temperature of a finite, but continuous, mass of air moving across a water/air boundary.

Let's say you have 150 degree F air moving at 0.007m^3/s over a relatively infinite source of water which is at 80 degrees. What sort of variables will I need to calculate the temperature of the air after it's moved parallel to the water boundary?

Thanks.
 
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  • #2
Is this ducted flow or open air flow ?
 
  • #3
Somewhat open; I'm using a natural convection setup with an infinite air mass moving through a venturi section (which has the water), into a semi enclosed container, where it will no longer be in contact with the water.

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  • #4
The scale of the device will be relevant . Thin layers of air will cool much better and be more predictable than thick layers .

Also direct flat on flat contact of air/water may not be best arrangement for effective heat transfer . At least consider a simple heat exchanger with very large surface areas exposed to air and to water .

In any case ideally need to have movement of water as well as air . This may occur naturally or could be induced .
 
  • #5
If the air is 100% RH at entry, then flows over the colder water, precipitation may occur as the air cools.
If the air is 0% RH at entry, evaporation of water over an infinite path will increase the RH to 100%.
Whatever happens, the air that exits the chamber will be saturated, 100% RH.
You must therefore consider the energy exchange due to the possible phase changes of water.
 
  • #6
Have a look at this,
https://www.ohio.edu/mechanical/thermo/Applied/Chapt.7_11/Chapter10a.html
which shows how to calculate for the adiabatic saturation temperature of a mass of air flowing over water. the duct is assumed to be very long so that the air exits at 100% humidity.

Note that the liquid pool of water has a mass flow rate m(dot)f, but you do not say if your water pool is being replenished or not.
Not to say whether your air achieves 100% humidity as that will depend upon your length of duct and flow rate.
If you have no liquid water flow, the temperature of the water will change also.

You can use that as a guide. Most surely you will have to adapt to your particular situation.
 

Related to Heat transfer from an air current across a body of water

1. How does heat transfer from an air current across a body of water?

Heat transfer from an air current across a body of water occurs through a process called convection. As the air moves over the water's surface, it absorbs heat from the water, causing it to warm up. This warm air then rises and is replaced by cooler air, creating a continuous cycle of heat transfer.

2. What factors affect the rate of heat transfer in this process?

Several factors can affect the rate of heat transfer from an air current across a body of water. These include the temperature difference between the air and water, the speed of the air current, the surface area of the water, and the humidity levels in the air.

3. How is heat transfer from an air current across a body of water important in weather patterns?

The heat transfer from an air current across a body of water plays a crucial role in weather patterns. As warm air rises from the water, it can create areas of low pressure, leading to the formation of clouds and potentially precipitation. It also contributes to the formation of ocean currents, which can impact global weather patterns.

4. Can heat transfer from an air current across a body of water be affected by human activities?

Yes, human activities such as deforestation and urbanization can impact the rate of heat transfer from an air current across a body of water. These activities can change the surface area and composition of the land, altering the temperature and humidity levels in the air and ultimately affecting the heat transfer process.

5. How does heat transfer from an air current across a body of water impact aquatic life?

The heat transfer from an air current across a body of water can affect aquatic life in several ways. For example, it can impact the water temperature, which can affect the growth and reproduction of aquatic plants and animals. It can also impact the oxygen levels in the water, which can have a significant impact on the survival of aquatic organisms.

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