Psychrometric Properties in 4.0
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Questions and Answers

What do psychrometric properties define?

  • Properties of moist air (correct)
  • Properties of the atmosphere
  • Properties of water vapor
  • Properties of dry air

    • How many properties are required to completely define the thermodynamic state of a mixture of two substances?

  • Two
  • Three (correct)
  • Four
  • Five

    • What is considered as the dry bulb temperature in the context of psychrometry?

  • Actual temperature of moist air (correct)
  • Temperature of water vapor
  • Temperature of only dry air
  • Temperature at which water vapor condenses

    • Why are all calculations in air-conditioning practice based on the dry air part?

    <p>Dry air behaves more like a perfect gas than water vapor</p> Signup and view all the answers

    According to the Gibbs-Dalton laws, what can be applied to a mixture of moist air?

    <p>Laws of perfect gas mixture</p> Signup and view all the answers

    What is the total pressure equal to in the context of psychrometry?

    <p>Barometric pressure</p> Signup and view all the answers

    What is the empirical expression for the enthalpy of the water vapor part?

    <p>hv = 2501 + 1.88t</p> Signup and view all the answers

    What is the wet bulb temperature (WBT) a measure of?

    <p>The dryness of air</p> Signup and view all the answers

    What does the process of adiabatic saturation of air involve?

    <p>Cooling the air and water by evaporation</p> Signup and view all the answers

    What is the specific heat of liquid water used in determining the enthalpy of water vapour?

    <p>4.1868 kJ/kg K</p> Signup and view all the answers

    Which temperature is known as the thermodynamic wet bulb temperature or adiabatic saturation temperature?

    <p>$t_w$</p> Signup and view all the answers

    When steady conditions are reached during adiabatic saturation, what happens to the unsaturated air?

    <p>It is cooled adiabatically to adiabatic saturation temperature</p> Signup and view all the answers

    What does wet bulb depression (WBD) measure?

    <p>The difference between dry bulb and wet bulb temperatures</p> Signup and view all the answers

    What is meant by the term 'enthalpy' in thermodynamics?

    <p>$H = U + PV$</p> Signup and view all the answers

    $C_{pw}$ and $C_{pv}$ in the enthalpy expression refer to the specific heats of what substances respectively?

    <p>$C_{pw}$: Liquid water, $C_{pv}$: Water vapor</p> Signup and view all the answers

    $h_{fg}$ in the enthalpy expression stands for what quantity?

    <p>$hfg$: Latent heat of vaporization at DPT</p> Signup and view all the answers

    What is the term 'sigma heat' known for in the context of the adiabatic process?

    <p>Difference between the enthalpy and product of specific humidity and sensible heat</p> Signup and view all the answers

    Which values are plotted on the ordinate and abscissa of a common psychrometric chart?

    <p>Wet bulb temperature and water vapor pressure</p> Signup and view all the answers

    What is defined as the ratio of the mole fraction of water vapor in moist air to that in saturated air at the same temperature and pressure?

    <p>Relative humidity</p> Signup and view all the answers

    Where are the relative humidity lines typically drawn on a psychrometric chart?

    <p>Curved lines following the saturation curve</p> Signup and view all the answers

    What defines the values of constant specific volume lines on a psychrometric chart?

    <p>Values along the saturation curve</p> Signup and view all the answers

    What is represented by any point on the saturation curve in terms of dry bulb and wet bulb temperatures?

    <p><strong>Dry bulb</strong> and wet bulb temperatures are equal</p> Signup and view all the answers

    Which parameter remains constant during the adiabatic process according to the provided text?

    <p><strong>Sigma heat</strong></p> Signup and view all the answers

    What is plotted on the ordinate of a psychrometric chart according to common practice?

    <p><strong>Water vapor pressure</strong></p> Signup and view all the answers

    What does relative humidity on a psychrometric chart represent according to the content provided?

    <p>Mole fraction of water vapor compared to saturated air.</p> Signup and view all the answers

    Where are relative humidity lines typically found on a psychrometric chart?

    <p>Curved lines following the saturation curve.</p> Signup and view all the answers

    What is the definition of specific humidity or humidity ratio?

    <p>Ratio of the mass of water vapor to the mass of dry air in a given volume</p> Signup and view all the answers

    What is the dew point temperature (DPT)?

    <p>The temperature at which water vapor starts condensing in moist air</p> Signup and view all the answers

    What does the degree of saturation represent?

    <p>Measure of the capacity of air to absorb moisture</p> Signup and view all the answers

    How is relative humidity defined?

    <p>Ratio of the mole fraction of water vapor in moist air to that in saturated air</p> Signup and view all the answers

    What is the enthalpy of moist air according to Gibbs's law?

    <p>The summation of enthalpies of dry air and water vapor associated with the air</p> Signup and view all the answers

    How is specific humidity related to saturated air?

    <p>Specific humidity is lower than saturated air</p> Signup and view all the answers

    What happens if more water vapor is added to saturated air at a constant temperature?

    <p>The partial pressure increases until it reaches a saturation value</p> Signup and view all the answers

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