Question

In: Chemistry

Consider a one acre field with a 100 ft high layer of air exactly over the...

Consider a one acre field with a 100 ft high layer of air exactly over the field. Water vapor condenses and forms a 0.1 mm layer of dew on the surface of the field. If the air temperature was 60 oF when the dew forms, what is the final temperature of this layer of air (in oF)?

Assumptions and Values:

• Let the surface of the field be perfectly flat.

• Let the air absorb all heat from the formation of the dew.

• Let the heat of vaporization of water be ∆Hvap = 44 kJ mol

• Let the density of the air be ρair = 1.2 kg m3 • Let the specific heat of the air be Cair = 1.01 J g · oC

Solutions

Expert Solution

Data.

Area = 1 acre = 4046.86 m2

h = 100 ft = 30.48 m

Vair = 4046.86 m2 x 30.48 m = 1.2335 x 105 m3

--

hdew = 0.1 mm = 0.0001 m

Tdew = 60 °F = 15.56 °C

Vdew = 4046.86 m2 x 0.0001 m = 0.4047 m3

--

∆Hvap = 44 kJ/mol

ρair = 1.2 kg/m3

Cair = 1.01 J/g.°C

Tf = ?? °C

---

Heat absorbed.

qair (KJ) = mair x Cair x ∆T

where;

m = air mass, g

C = specific heat of air, J/g.°C

∆T = (Tf - To), change in temperature °C

--

mair = ρair x Vair = (1.2 kg/m3) x (1.2335 x 105 m3)

mair = 1.48 x 108 g

mvap = ρvap x Vvap = (1000 kg/m3) x (0.4047 m3)

mvap = 4.05 x 105 g

--

Heat absorbed from the formation of the dew.

qair = ∆Hvap x moles(dew)

qair = 44 kJ/mol x [(4.05 x 105 g)/(18 g/mol)]

qair = 9.89 x 105 KJ

--

Let's find the missing temperature:

9.89 x 108 J = 1.48 x 108 g x 1.01 J/g.°C x (T2 - 15.56 °C)

6.61 x 10-3 °C = T2 - 15.56 °C

T2 = 15.56661 ° C = 60.019898 °F

It all looks that this process acts as an isothermally one!


Related Solutions

Consider a one acre field with a 100 ft high layer of air exactly over the...
Consider a one acre field with a 100 ft high layer of air exactly over the field. Water vapor condenses and forms a 0.1 mm layer of dew on the surface of the field. If the air temperature was 60 oF when the dew forms, what is the final temperature of this layer of air (in o F)? Assumptions and Values: • Let the surface of the field be perfectly flat. • Let the air absorb all heat from the...
Consider the two-dimensional laminar boundary layer flow of air over a wide 15 cm long flat...
Consider the two-dimensional laminar boundary layer flow of air over a wide 15 cm long flat plate whose surface temperature varies linearly from 20°C at the leading edge to 40°C at the trailing edge. This plate is placed in an airstream with a velocity of 2 m/s and a temperature of 10°C. Numerically determine how the surface heat flux varies along the plate. Explain the results obtained with proper reasoning. Support your results with scaling analysis wherever possible.I need c++...
Refer to the example bore-log in the presentation. Consider one layer in sand and one layer...
Refer to the example bore-log in the presentation. Consider one layer in sand and one layer in clay. Explain how the soil description is arrived at.
Albany High School is planning a field trip for senior students. They expected 100 students to...
Albany High School is planning a field trip for senior students. They expected 100 students to participate in the trip but eventually 130 students join the trip. They planned to charge each student a price of $25 for the trip and spend an expense of $20 per student for the trip. Then, they find that the expense of the filed trip goes up to $30 per student, and they have to increase the price for each student to $40. Budget...
A spring is mounted over an air track in such a way that the one end...
A spring is mounted over an air track in such a way that the one end of the spring is fixed and the other is connected to a spring scale. When the spring is stretched to 0.01 m a force of 1 N is registered on the spring scale. The spring is relaxed and a glider of 0.43 kg (resting on the air track) is connected to it. The glider-spring system is then pulled to the right through a distance...
A Carnot engine operates on air between high and low pressures of 3 MPa and 100...
A Carnot engine operates on air between high and low pressures of 3 MPa and 100 kPa with a low temperature of 20°C. For a compression ratio of 15, calculate the thermal efficiency?, the MEP? , and the work output?
(40 pts) Consider the von Thunen Model discussed in class. Alternative uses of one acre of...
(40 pts) Consider the von Thunen Model discussed in class. Alternative uses of one acre of land around a city is summarized as follows: Revenue, output sold in the city Nonland cost of production Cost of transportation 1. Milk $1000 $200 $80/mile 2. Wheat $800 $200 $30/mile 3. Potato $600 $200 $10/mile (a) (10 pts) What is the bid-rent curves for milk producers, wheat producers, and potato pro- ducers, respectively? (b) (10 pts) What is the land-use pattern (what is...
One hundred moles of moist air (100 moles) at 25oC and 100 kPa has a dew...
One hundred moles of moist air (100 moles) at 25oC and 100 kPa has a dew point of 16oC. If you want to remove 50% of the initial moisture in the air (at a constant pressure of 100 kPa). 1. Sketch the process. 2. Determine to what temperature should you cool the air? Assume that after removal of 50% of moisture from the air, the final air is saturated.
6. Air pollution problem. Consider an airshed in which there is one major contributor to air...
6. Air pollution problem. Consider an airshed in which there is one major contributor to air pollution--a cement-manufacturing plant whose annual production capacity is 2.500,000 barrels of cement. Figures are not available to determine whether the plant has been operating at capacity. Although the kilns are equipped with mechanical collectors for air pollution control, the plant still emits 2.0 lb of dust per barrel of cement produced. There are two types of electrostatic precipitators that can be installed to control...
Consider a constant pressure device. The inlet flow to this device is moist air at 100...
Consider a constant pressure device. The inlet flow to this device is moist air at 100 kPa, 40oC, 40% relative humidity. The outlet flow from this device is cooled to 15oC. Determine: (a) the humidity ratio of the inlet and the exit flow, (b) the heat transfer in the device per kg dry air, (c) repeat (a) and (b) using the psychrometric chart.
ADVERTISEMENT
ADVERTISEMENT
ADVERTISEMENT