Ideal Gas Mixtures and Psychrometrics Applications

What does a gravimetric analysis of a mixture provide?

A gas mixture has the following molar analysis: CO2, 10 percent; H2O, 15 percent; O2, 5 percent; N2, 70 percent. What is the apparent molecular weight of the mixture in kg/kmol? Use approximate molecular weights: CO2=44, H2O=18, O2=32, N2=28.

What is the core assumption of the Dalton model for an ideal gas mixture?

An ideal gas mixture at a total pressure of 150 kPa has a mole fraction of oxygen of 0.21. According to the Dalton model, what is the partial pressure of the oxygen?

How is the partial volume of a component in an ideal gas mixture defined according to the Amagat model?

For an ideal gas mixture, how are the specific heats on a molar basis, cv and cp, determined?

When evaluating the entropy of an ideal gas mixture, at what conditions is the entropy of each component evaluated?

What is the study of systems involving mixtures of dry air and water vapor known as?

How is the humidity ratio, omega, of a moist air sample defined?

Moist air at 1 bar has a partial pressure of water vapor of 0.02 bar. What is its humidity ratio, omega, in kg water vapor/kg dry air? (Molecular weight of water is 18.0, molecular weight of dry air is 28.97)

What is the dew point temperature?

Moist air at 25 C has a relative humidity of 60 percent. The saturation pressure of water at 25 C is 0.03169 bar. What is the dew point temperature of this air sample?

In the context of psychrometrics, what does 'saturated air' signify?

What is the relationship between the wet-bulb temperature and the dry-bulb temperature for unsaturated air?

In an air-conditioning process, moist air is heated at constant pressure with no moisture added or removed. What happens to its humidity ratio and relative humidity?

A stream of moist air at 5 C and 1 bar has a mass flow rate of 180 kg/min and a humidity ratio of 0.002 kg/kg. It is mixed adiabatically with a second stream at 24 C and 1 bar with a mass flow rate of 497 kg/min and a humidity ratio of 0.0094 kg/kg. What is the humidity ratio of the exiting mixed stream?

What is the primary mechanism of cooling in an evaporative cooler?

What is the primary purpose of a cooling tower?

The mass fraction of component 'i' in a mixture is defined by which of the following ratios?

A gas mixture has a gravimetric analysis of 10 percent H2, 60 percent N2, and 30 percent CO2. What is the mole fraction of H2 in this mixture? (Approximate molecular weights: H2=2, N2=28, CO2=44)

In a process where a moist air stream is cooled at constant pressure from 21 C to 5 C, causing some water to condense, what is the state of the water vapor in the air at the final state of 5 C?

When cooling a moist air mixture in a rigid, closed vessel of constant volume, at what temperature does condensation begin?

Three factors contribute to the production of entropy in mixing processes. Which of the following is NOT one of those factors?

How is the enthalpy of a moist air mixture per unit mass of dry air (h_a + omega * h_v) commonly evaluated for the water vapor component (h_v) in psychrometric applications?

What is the primary function of the makeup water added to a cooling tower?

In the general energy balance for an open air-conditioning system, 0 = Q_cv + m_a*(h_a1 - h_a2) + m_v1*h_v1 - m_v2*h_v2 + m_w*h_w, what does the term m_w represent?

Which property remains nearly constant along the lines of constant wet-bulb temperature on a psychrometric chart?

An ideal gas mixture consists of 0.3 kg of CO2 and 0.2 kg of N2. What is the total number of moles in the mixture? (Molecular weights: CO2=44, N2=28)

A mixture of 0.8 mole fraction CO2 and 0.2 mole fraction O2 expands isentropically through a nozzle from 700 K and 5 bars to 1 bar. The final temperature is 517.6 K. What is the change in specific entropy for the O2 component in kJ/kmol K? (s_O2 at 700 K = 231.358; s_O2 at 517.6 K = 221.667; R = 8.314)

What is the reason that the Amagat model's relationship between volume fraction and mole fraction (Vi/V = yi) underlies the term 'volumetric analysis'?

How is the change in internal energy (Delta U) for an ideal gas mixture undergoing a process at constant composition calculated?

What is the key difference in calculating the enthalpy change versus the entropy change for a component in an ideal gas mixture process?

Two rigid, insulated tanks are interconnected by a valve. One contains 0.79 kmol of N2 at 2 bars and 250 K. The other contains 0.21 kmol of O2 at 1 bar and 300 K. The valve is opened and the gases mix. What is the final temperature of the mixture? (Use cv,N2 = 20.82 kJ/kmol K and cv,O2 = 20.99 kJ/kmol K)

For a dehumidification process, how is the mass flow rate of the condensed water (m_w) related to the humidity ratios (omega) and the mass flow rate of dry air (m_a)?

What does a volumetric analysis of a mixture provide?

Moist air enters a steam-spray humidifier at 22 C. Saturated water vapor at 110 C is injected. If the process is adiabatic, what changes occur in the humidity ratio and dry-bulb temperature of the air?

If you use the psychrometric chart (Fig. A-9) for an air sample with a dry-bulb temperature of 20 C and a wet-bulb temperature of 15 C, what is the approximate relative humidity?

On a standard psychrometric chart, what do the horizontal lines represent?

Why is the change in specific entropy for an ideal gas mixture undergoing a constant-composition process dependent on the ratio of mixture pressures (p2/p1) rather than partial pressures?

The mixture enthalpy on a psychrometric chart is given per unit mass of what substance?

What is the apparent molecular weight M of a mixture if its total mass is 100 kg and it contains 7.82 kmol of substance?

If two different ideal gases, both initially at the same temperature and pressure, are mixed adiabatically, will entropy be produced?

A dehumidifier cools moist air from 30 C to 10 C at a constant pressure of 1.013 bar. The initial humidity ratio is 0.0133 and the final is 0.0076. What is the amount of water condensed per kg of dry air?

What is the defining characteristic of an evaporative cooling process on a psychrometric chart?

A gas mixture contains components A and B. If the mass fraction of A (mf_A) is 0.5 and the mole fraction of A (y_A) is 0.5, what must be true about the molecular weights of A and B?

A closed system consisting of 0.5 kg of a CO2 and N2 mixture is compressed in a polytropic process where n=1.25. The initial state is 1 bar, 300 K and the final pressure is 3 bar. The apparent molecular weight is 35.97. What is the work done in kJ?

Relative humidity is the ratio of the mole fraction of water vapor in a moist air sample to the mole fraction in a saturated sample at the same temperature and pressure. How else can it be expressed?

An air stream at 32 C is mixed with an oxygen stream at 127 C. The final mixture temperature is 47 C. The mass flow rate of the air is 114.29 kg/min. What is the mass flow rate of the oxygen? (h_air at 47C = 320.29, h_air at 32C = 305.22; h_O2 at 127C = 11711/32, h_O2 at 47C = 9325/32; all in kJ/kg)

When an ideal gas mixture's properties are evaluated on a mass basis, how are molar properties converted?

A dehumidifier operates at a constant pressure of 1.013 bar. Air enters at 30 C, 50 percent relative humidity (omega = 0.0133) and exits as saturated air at 10 C (omega = 0.0076). The enthalpy of entering moist air is 64.1 kJ/kg dry air and the enthalpy of exiting moist air is 29.5 kJ/kg dry air. The enthalpy of the liquid condensate is 42.01 kJ/kg. What is the heat transfer from the moist air, in kJ per kg of dry air?