Quiz 2
Winter 2006
Mech 341: Thermo 2
Quiz 2 Mean: Median: Max: Min:
73.0 79 97 0
Questions about Marking of the Exam? • First, please see the solution set (available in WebCT now) • Next, see the individual who marked the specific problem you have a question about: Problem 1 ................. Prof. Higgins (MD358, Mon. 13:30 - 14:30 Wed. 15:30 - 16:30)
Problem 2 ................. Daniel Szirti (MD 254, Tue. 11:30-13:00)
Student Name:________________________ Student Number: ______________________
MECH-341 Thermo 2 Quiz 2 Monday, Feb 27, 2006 12:35 pm – 1:25 pm Note: • Closed book, closed notes. • Answer both problems; there is only one printed side of this page. • Use interpolation in extracting data from thermodynamic tables. 50 pts.
1. The p-v-T relationship for a certain gas can be expressed as
A RT v = -------- + B + -------p RT
where R is the gas constant and A and B are constants. Starting with the TdS relations, use Maxwell's relations to find an expression for the change in enthalpy due to a change in pressure at constant temperature: h(p2, T) – h(p1, T).
50 pts.
2 A system of air conditioning commonly used in the Middle East consists of air flowing over a pool of water located below a house in the desert. As air flows over the water, it is cooled and is then directed upward, into the house. Note that the make-up water can be assumed to be at the same temperature as the exit air, and the total pressure remains at 1 atm (101.3 kPa). If the inlet air is at 35° C and 10% relative humidity and has a flow rate of 1 kgdry-air/minute, and the exit air is at 23° C, find:
Texit = 23 °C
Tin = 35°C pin = 1 atm
a) The relative humidity φ of the exit air by using tabulated data in Table A-2 and A-22
φin = 10% 1 kg-dry-air/min
b) The mass flow rate of the make-up water [kg/ min].
make-up water at Texit
c) Verify your answers for (a) and (b) using the psychrometric chart. d) Will the moist air rise naturally or will it need to be forced (for example, with a fan)? Explain your answer by computing the specific volume (or density) of the entering and exiting air/vapor mixture.
Mech 341: Thermo 2
Quiz 2 Mean: Median: Max: Min:
73.0 79 97 0
Questions about Marking of the Exam? • First, please see the solution set (available in WebCT now) • Next, see the individual who marked the specific problem you have a question about: Problem 1 ................. Prof. Higgins (MD358, Mon. 13:30 - 14:30 Wed. 15:30 - 16:30)
Problem 2 ................. Daniel Szirti (MD 254, Tue. 11:30-13:00)
Student Name:________________________ Student Number: ______________________
MECH-341 Thermo 2 Quiz 2 Monday, Feb 27, 2006 12:35 pm – 1:25 pm Note: • Closed book, closed notes. • Answer both problems; there is only one printed side of this page. • Use interpolation in extracting data from thermodynamic tables. 50 pts.
1. The p-v-T relationship for a certain gas can be expressed as
A RT v = -------- + B + -------p RT
where R is the gas constant and A and B are constants. Starting with the TdS relations, use Maxwell's relations to find an expression for the change in enthalpy due to a change in pressure at constant temperature: h(p2, T) – h(p1, T).
50 pts.
2 A system of air conditioning commonly used in the Middle East consists of air flowing over a pool of water located below a house in the desert. As air flows over the water, it is cooled and is then directed upward, into the house. Note that the make-up water can be assumed to be at the same temperature as the exit air, and the total pressure remains at 1 atm (101.3 kPa). If the inlet air is at 35° C and 10% relative humidity and has a flow rate of 1 kgdry-air/minute, and the exit air is at 23° C, find:
Texit = 23 °C
Tin = 35°C pin = 1 atm
a) The relative humidity φ of the exit air by using tabulated data in Table A-2 and A-22
φin = 10% 1 kg-dry-air/min
b) The mass flow rate of the make-up water [kg/ min].
make-up water at Texit
c) Verify your answers for (a) and (b) using the psychrometric chart. d) Will the moist air rise naturally or will it need to be forced (for example, with a fan)? Explain your answer by computing the specific volume (or density) of the entering and exiting air/vapor mixture.
