my question is that let's say the water temperature in the chamber is Tf ... is it possible to have T2 < Tf ? is Tf the minimum temperature that can be achieved by air? or is T2 completely unrelated to Tf and can be lower than Tf
If the humidity ratio is defined as the mass of water vapor per the mass of dry air then based on what can you conclude that the humidity ratio is also defined as the mass flow of water vapor per the mass flow of dry air? Do they flow at the same rate? If so, why?
It might be easier to understand starting with the mass flow rate of dry air, ṁₐ. At any given point or region, the humidity ratio, ω, represents the ratio of water vapor to that. If you assume that the humidity ratio is constant through that control volume, then the mass flow rate of vapor is the dry air flow rate multiplied by the humidity ratio or ṁ_v = ṁₐ ω. You can rearrange from there to get the form that I showed.
Because there are no sources or sinks of heat, when you evaporate water into air, to cool it to its wet bulb temperature. All energy to evaporate the water vapor from the feedstock of coolant water, will come from the thermal energy of the airmass being cooled, as it mixes with newly evaporated water vapor. Due to no sources or sinks of heat, we call it an adiabatic process.
No, it is the adiabatic saturation temperature -- the dew point temperature is another important related concept. Essentially, given the normal temperature of air that you are used to measuring with a thermometer, the wet-bulb (and nearly equal adiabatic saturation temperature) is the limit to how cold the air can get just by evaporating water, while the dew point temperature is how cold the air must be just before it starts condensing out, with no change in the mass of water in the air.
I think I understand your question now, you are correct in that when the air is fully saturated, the dew point temperature, wet bulb temperature, and dry-bulb temperature are all the same value and so T2 will also equal the wet bulb/adiabatic saturation temp. However, we are generally interested in what the dew point temperature and wet bulb temperature are when the air is not saturated. Hope that helps clarify.
@@bashamsk1288 The dew point is based on only heat transfer. The wet bulb temperature is based on only mass transfer as the liquid water source is evaporated by the heat from the air. The wet bulb temperature is what you would experience, cooling dry air in a swamp cooler. It can be an energy efficient alternative to an air conditioner in a dry climate like Las Vegas, but it has its limitations. The dew point is what you would experience, cooling any air in an air conditioner duct. The evaporator cannot suck water out of the air, or inject water into it; the evaporator can only suck heat out of the air. The air cools until it gets to its dew point, and then condenses onto the evaporator coil. The evaporator coil continues to generate condensate as it de-humidifies the air.
my question is that let's say the water temperature in the chamber is Tf ... is it possible to have T2 < Tf ? is Tf the minimum temperature that can be achieved by air? or is T2 completely unrelated to Tf and can be lower than Tf
Do you mean we could cool down the air using hot water?
If the humidity ratio is defined as the mass of water vapor per the mass of dry air then based on what can you conclude that the humidity ratio is also defined as the mass flow of water vapor per the mass flow of dry air? Do they flow at the same rate? If so, why?
It might be easier to understand starting with the mass flow rate of dry air, ṁₐ. At any given point or region, the humidity ratio, ω, represents the ratio of water vapor to that. If you assume that the humidity ratio is constant through that control volume, then the mass flow rate of vapor is the dry air flow rate multiplied by the humidity ratio or ṁ_v = ṁₐ ω. You can rearrange from there to get the form that I showed.
Thanks a a lot for your big help
Can i use steam table for the data ? psychrometric chart?
or what table should i use to find the values needed?
For the water vapor terms, the most accurate source of information would be the steam tables as you first suggested.
Why adiabatic saturation temperature is equal to wet bulb temperature in air -water system?
Because there are no sources or sinks of heat, when you evaporate water into air, to cool it to its wet bulb temperature. All energy to evaporate the water vapor from the feedstock of coolant water, will come from the thermal energy of the airmass being cooled, as it mixes with newly evaporated water vapor. Due to no sources or sinks of heat, we call it an adiabatic process.
thanks so much , sir\
thanks man, it makes a difference :D
is t2 is due point temperature?
No, it is the adiabatic saturation temperature -- the dew point temperature is another important related concept. Essentially, given the normal temperature of air that you are used to measuring with a thermometer, the wet-bulb (and nearly equal adiabatic saturation temperature) is the limit to how cold the air can get just by evaporating water, while the dew point temperature is how cold the air must be just before it starts condensing out, with no change in the mass of water in the air.
Mitchell Paulus whats the difference between both i mean air is completely saturated if we decrease temperature future dew will form
I think I understand your question now, you are correct in that when the air is fully saturated, the dew point temperature, wet bulb temperature, and dry-bulb temperature are all the same value and so T2 will also equal the wet bulb/adiabatic saturation temp. However, we are generally interested in what the dew point temperature and wet bulb temperature are when the air is not saturated. Hope that helps clarify.
@@bashamsk1288 The dew point is based on only heat transfer. The wet bulb temperature is based on only mass transfer as the liquid water source is evaporated by the heat from the air.
The wet bulb temperature is what you would experience, cooling dry air in a swamp cooler. It can be an energy efficient alternative to an air conditioner in a dry climate like Las Vegas, but it has its limitations.
The dew point is what you would experience, cooling any air in an air conditioner duct. The evaporator cannot suck water out of the air, or inject water into it; the evaporator can only suck heat out of the air. The air cools until it gets to its dew point, and then condenses onto the evaporator coil. The evaporator coil continues to generate condensate as it de-humidifies the air.
good
Thanks a a lot for your big help
Thanks a a lot for your big help