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  • General

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  • Humidification

    • Humidity Chart Page
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    • Relation between Percentage and Relative Humidities Page
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    • Mixing Air of Different Relative Humidities Page
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    • Effect of Heating and Adiabatic Cooling Page
      1988-5-b-vi-mt
      Air with a dry bulb temperature \(t_{d1}\) and a wet bulb temperature \(t_{w1}\) is passed through a heater and then through an adiabatic cooler from which it emerges with dry and wet bulb temperatures of \(t_{d2}\) and \(t_{w2}\) respectively. Then
      1. always \(t_{w1} > t_{w2} \mbox { and } t_{d1} > t_{d2}\)
      2. always \(t_{w1} < t_{w2} \mbox { and } t_{d1} > t_{d2}\)
      3. always \(t_{w1} > t_{w2} \mbox { and } t_{d1} < t_{d2}\)
      4. \(t_{w1} < t_{w2} \mbox { and } t_{d1} \mbox { can be greater than, equal to or less than } t_{d2}\)
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    • Relative Humidity from Dewpoint and Vapor Pressure Data Page
      1994-9-mt
      Air at 30\(^\circ\)C and 150 kPa in a closed container is compressed and cooled. It is found that the first droplet of water condenses at 200 kPa and 15\(^\circ\)C. Calculate the percent relative humidity of the original air. The vapor pressures of water at 15\(^\circ\)C and 30\(^\circ\)C are 1.7051 kPa and 4.246 kPa respectively.
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    • Change in Relative Humidity of Air due to Heating Page
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    • Dry Bulb, Wet Bulb and Dew Point Temperatures Page
      2003-67-mt
      The following plot gives the saturated humidity (\(H_e\)) versus Temperature (\(T\)).

      Line joining \((H_1,T_1)\) and \((H_2,T_2)\) is the constant enthalpy line. Choose the correct one.
      1. \(T_1\) - Dew point Temp; \(T_2\) - Dry bulb Temp; \(T_3\) - Wet bulp Temp.
      2. \(T_1\) - Dew point Temp; \(T_2\) - Wet bulb Temp; \(T_3\) - Wet bulp Temp.
      3. \(T_1\) - Wet bulb Temp; \(T_2\) - Dry bulb Temp; \(T_3\) - Dew point Temp.
      4. \(T_1\) - Dry bulb Temp; \(T_2\) - Wet bulb Temp; \(T_3\) - Dew point Temp.
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    • Dew Point, Dry-Bulb, Wet Bulb Temperatures and Humidity Page
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      2004-21-22-mt
      An air-water vapor mixture has a dry bulb temperature of 60oC and a dew point temperature of 40oC. The total pressure is 101.3 kPa and the vapor pressures of water at 40oC and 60oC are 7.30 kPa and 19.91 kPa, respectively.
      1. The humidity of air sample expressed as kg of water vapor/kg of dry air is _____ (0.048 / 0.079 / 0.122 / 0.152)
      2. The wet bulb temperature \(T_w\) for the above mixture would be ______
        1. less than 40oC
        2. 40oC
        3. 40oC < T_w < 60oC
        4. 60oC
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    • Constant Pressure Heating of Air Page
      1989-5-ii-e-f-mt
      Air is passed through a heater at constant pressure. The inlet and outlet conditions of the air are as follows:
      Inlet:
      Dry bulb temperature = 31.7\(^\circ \)C
      Wet bulb temperature = 23.9\(^\circ \)C
      Humidity = 30%
      Outlet:
      Dry bulb temperature = 70\(^\circ \)C
      1. The inlet air will have a dew point
        1. Equal to 23.9\(^\circ\)C
        2. Between 23.9\(^\circ\)C and 31.7\(^\circ\)C
        3. Greater than 31.7\(^\circ\)C
        4. Less than 23.9\(^\circ \)C
      2. In the above problem, the air from the heater will have a humidity:
        1. Equal to 30%
        2. Greater than 30%
        3. Less than 30%
        4. None of the above
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    • Humid Volume of Air - Water-vapor Mixture Page
      AG-2019-25
      Air-water vapor mixture at 1 atmosphere pressure has 0.035 kg water vapor per kg dry air, and dry bulb temperature of 37oC. The value of Universal gas constant is 8.314 kJ/(kmol.K). The humid volume of this air-water vapor mixture in m3/kg dry air (rounded off to three decimal places) is ___________.
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    • Humid Heat of Gas Page
      1999-2-11-mt
      If the specific heats of a gas and vapor are 0.2 kJ/kg.K and 1.5 kJ/kg.K respectively, and the humidity is 0.01, the humid heat in kJ/kg.K is _____ (0.017 / 0.107 / 0.215 / 0.310)
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    • Adiabatic Saturation of Air Page
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    • Humidity of Air from Wet-bulb Depression Data Page
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    • Enthalpy of Air from Psychrometric Ratio Page
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    • Mass and Energy Balances on Humid Air Page
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    • Dry-Bulb Temperature of Air from Wet-Bulb Temperature Data Page
      2000-11-mt
      Air at 1 atm is blown past the bulb of a mercury thermometer. The bulb is covered with a wick. The wick is immersed in an organic liquid (molecular weight = 58). The reading of the thermometer is 7.6\(^\circ\)C. At this temperature, the vapor pressure of the liquid is 5 kPa. Find the air temperature (in \(^\circ\)C), given that the ratio of heat transfer coefficient to the mass transfer coefficient (psychrometric ratio) is 2 kJ/kg.K and the latent heat of vaporization of the liquid is 360 kJ/kg. Assume that the air, which is blown, is free from the organic vapor.
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