Question

Question 8
? Which of the following options
is true for The Dry Bulb
Temperature (TDBT), The Wet
Bulb Temperature (TWBT) and
The Dew Point Temperature
(TDPT) for a mixture of air and
water vapour?​

Answer 1

Explanation:

This discussion on Which of the following option is true for the dry bulb temperature (TDBT), the wet bulb temperature (TWBT) and dew point temperature (TDPT) for a mixture of air and water vapoura)b)c)d)Correct answer is option 'B'. Can you explain this answer? is done on EduRev Study Group by Mechanical Engineering Students. The Questions and Answers of Which of the following option is true for the dry bulb temperature (TDBT), the wet bulb temperature (TWBT) and dew point temperature (TDPT) for a mixture of air and water vapoura)b)c)d)Correct answer is option 'B'. Can you explain this answer? are solved by group of students and teacher of Mechanical Engineering, which is also the largest student community of Mechanical Engineering. If the answer is not available please wait for a while and a community member will probably answer this soon. You can study other questions, MCQs, videos and tests for Mechanical Engineering on EduRev and even discuss your questions like Which of the following option is true for the dry bulb temperature (TDBT), the wet bulb temperature (TWBT) and dew point temperature (TDPT) for a mixture of air and water vapoura)b)c)d)Correct answer is option 'B'. Can you explain this answer? over here on EduRev! Apart from being the largest Mechanical Engineering community, EduRev has the largest solved Question bank for Mechanical Engineering.

Answer 2

Answer:

The correct option is Option B

Explanation:

Temperature is the measure of average kinetic energy (KE) of a gas, liquid, or solid. Kinetic Energy is energy of motion.

Dry Bulb Temperature of Air (DBT)

• The temperature of the air measured by the ordinary thermometer is called as the dry bulb temperature of air, commonly referred as DBT. When ordinary thermometer is exposed to the atmosphere, it indicates the dry bulb temperature, which is nothing but the atmospheric temperature.
• Wet bulb temperature is the lowest temperature to which air can be cooled by the evaporation of water into the air at a constant pressure. The dry bulb temperature is the ambient temperature. The difference between these two temperatures is a measure of the humidity of the air. The wet bulb temperature is always lower than the dry bulb temperature but will be identical with 100% relative humidity

Wet Bulb Temperature of Air (WBT)

• The Wet Bulb temperature is the temperature of adiabatic saturation. The wet bulb temperature of air is also measured by the ordinary thermometer, but the only difference is that the bulb of the thermometer is covered by the wet cloth.
• Temperature of the ordinary air measured by the thermometer when it is covered by wet cloth or wick is called as the wet bulb temperature, commonly referred to as WBT.
• When the air comes in contact with the wet cloth it absorbs some moisture and gives up some heat, due to which the temperature of the air reduces. This reduced temperature measured by the thermometer is called as the wet bulb temperature. If the moisture content of the air is very low, it will give up more heat to the cloth and the wet bulb temperature of air will also be comparatively lower.
• On the other hand, if the moisture content of air is high it will loose lesser heat to the air and wet bulb temperature will be higher. The more is the moisture or water vapor content of the air more is the wet bulb temperature. Thus the wet bulb temperature indirectly indicates the moisture content present in the air or we can say that it is affected by the relative humidity of the air. The wet bulb temperature of the air is always less than the dry bulb temperature of air.
• Wet bulb temperature essentially measures how much water vapor the atmosphere can hold at current weather conditions. A lower wet bulb temperature means the air is drier and can hold more water vapor than it can at a higher wet bulb temperature. In a drier parcel of air, the dry bulb is just the air temperature which will be the warmest of the three variables. The dew point will be the lowest number, and the wet bulb will fall between those two.
• The key difference between dewpoint and wet bulb temperature is that dewpoint temperature is the temperature to which we should cool the air to saturate the air with water vapor whereas wet bulb temperature is the temperature that we get from a moistened thermometer bulb that is exposed to air flow.

Wet Bulb – The lowest temperature that can be reached by the evaporation of water only, measuring humidity.

Dew Point – the temperature to which the ambient air (Dry Bulb) must be cooled to reach 100% relative humidity – Saturation.

Dew Point Temperature of Air (DPT)

• The Dew Point is the temperature at which water vapor starts to condense out of the air, the temperature at which air becomes completely saturated. Above this temperature the moisture will stay in the air. When the temperature of the air is reduced, the temperature of the water vapor present within the air also reduces. If the dew-point temperature is close to the air temperature, the relative humidity is high, and if the dew point is well below the air temperature, the relative humidity is low.
• The water vapor within the air is similar to the superheated steam in the vapor condition, but at much lower pressure. When we reduce the temperature of the superheated steam, its sensible heat content starts reducing and at some particular temperature (100 degree C) it starts condensing. In a similar manner, when the temperature of the air is reduced continuously, the point comes when the water vapor within the air starts getting converted into dews.
• The temperature at which the water vapor within the air at some temperature starts condensing is called as the dew point temperature of the air or DPT. When the dew is formed the air is said to be in saturated condition. When any object is cooled below the dew point temperature of the air, we can see the formation of sweat on its surface.
• A glass of water filled with chilled water is can example. The dew point temperature of air depends upon its moisture content. Higher the moisture content of the air, higher is the dew point temperature. For the saturated air, the dry bulb temperature, the wet bulb temperature and dew point temperature are same.