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Consider the following statements for the appropriate context: 1. The Relative Humidity of air remains constant during sensible heating or cooling 2. The Dew Point Temperature of air remains constant during sensible heating or cooling 3. The total enthalpy of air remains constant during adiabatic cooling 4. It is necessary to cool the air below its Dew Point Temperature for dehumidifying Which of the above statements are correct?

Consider the following statements for the appropriate context: 1. The Relative Humidity of air remains constant during sensible heating or cooling 2. The Dew Point Temperature of air remains constant during sensible heating or cooling 3. The total enthalpy of air remains constant during adiabatic cooling 4. It is necessary to cool the air below its Dew Point Temperature for dehumidifying Which of the above statements are correct? Correct Answer 2, 3 and 4

Every psychometric chart includes vertical lines that represent the dry bulb temperatures, diagonals line represents wet bulb temperature and curved lines represent relative humidity.

Dry Bulb Temperature: Actual temperature of gas or mixture of gases.

Wet Bulb temperature: Temperature obtained by an accurate thermometer having a wick moistened with distilled water

Dew point temperature: Temperature at which the liquid droplets just appear when the moist air is cooled continuously.

Relative humidity along the saturation line is 100%.

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Following observations can be made from the psychometric chart

If relative humidity has not to change with the temperature then its specific humidity will not remain constant.

If air is saturated then its relative humidity is 100% that means it can't absorb more moisture, therefore if it will be made to pass over the water it will not absorb the moisture consequently its temperature will not change. 

If air is saturated then its dry bulb temperature, wet bulb temperature and dew point temperature all are the same.

“The Relative Humidity of air remains constant during sensible heating or cooling” is an incorrect statement

Validation:

The relative humidity of the air decreases when there is sensible heating and increase when there is sensible cooling.

“The Dew Point Temperature of air remains constant during sensible heating or cooling” is a correct statement

Validation:

The dew point temperature is given by the horizontal line moving towards the saturation curve, during the sensible cooling or heating the specific humidity remains constant therefore the sensible heating cooling is along a horizontal ling therefore the dew point temperature also remains constant.

“The total enthalpy of air remains constant during adiabatic cooling” is a correct statement

Validation:

During adiabatic cooling the total enthalpy of the air remains constant, because it is along a constant enthalpy line.

“It is necessary to cool the air below its Dew Point Temperature for dehumidifying” is a correct statement

Validation:

Dehumidification is the process where the moisture from the air is removed, i.e. its specific humidity is decreased, and moisture will be condensed from the air only when it has reached its dew point temperature therefore it is necessary to col the air below its dew point temperature for dehumidifying.

Related Questions

Consider the following statements: 1. The relative humidity of air does not change with temperature as long as specific humidity remains constant. 2. Dew-point temperature is the temperature at which condensation begins when air is cooled at constant volume. 3. Saturated air passing over a water surface does not cause change of air temperature. 4. For saturated air, dry-bulb, wet-bulb and dew-point temperatures are identical. Which of the above statements are correct?
Consider the following statements with regard to atmospheric humidity: 1. Absolute humidity is the amount of water vapour per unit volume. 2. Hygrometer is used to measure relative humidity. 3. Dew point is the temperature at which the relative humidity is 75%. Which of the above statements are correct?
Consider the following statements for cooling towers: 1. Cooling tower is an artificial device used to cool the hot cooling water coming out of condenser more effectively. 2. The amount of water usually lost with induced draft cooling tower ranges from 5% to 6% by evaporation. 3. The amount of water usually lost with induced draft cooling tower ranges from 7% to 8% by drift losses. 4. The rate of evaporation of water and its cooling effect on the remaining water depends upon the relative humidity of air passing through the tower. Which of the above statements are correct?
In sensible cooling of moist air, its physical properties vary as follows: 1. The wet bulb temperature decreases 2. The dew point: temperature remains constant 3. The relative humidity increases Which of the above statements are correct?
Consider the following statements in respect of an evaporative cooling process: 1. The wet-bulb temperature remains constant. 2. The dew-point temperature remains constant. 3. The enthalpy remains constant. Which of the above statements are correct?
The sensible heat factor during the heating and humidification process is given by (where h₁ = Enthalpy of air entering the heating coil, h₂ = Enthalpy of air leaving the heating coil, and hA = Enthalpy of air at the end of humidification process)
The sensible heat factor during the heating and humidification process is given by (where h1 = Enthalpy of air entering the heating coil, h2 = Enthalpy of air leaving the heating coil and hA = Enthalpy of air at the end of humidification process)
The sensible heat factor during cooling and dehumidification process is given by (where h₁ = Enthalpy of air entering the cooling coil, h₂ = Enthalpy of air leaving the cooling coil, and hA = Enthalpy of air at the end of dehumidification process)
The sensible heat factor during cooling and dehumidification process is given by (where h1 = Enthalpy of air entering the cooling coil, h2 = Enthalpy of air leaving the cooling coil and hA = Enthalpy of air at the end of dehumidification process)
Consider the following statements: For the formation of dew, the dew point should be below the freezing point. For the formation of the frost, dew point should be at or above the freezing point. Which of the statements given above is/are correct?