1. If a parcel of air at 15 °C has a specific humidity of 4.6 g/kg, what is the relative humidity of that parcel?
1. If a parcel of air at 15 °C has a specific humidity of 4.6 g/kg, what is the relative humidity of that parcel?
Introduction to Chemical Engineering Thermodynamics
8th Edition
ISBN:9781259696527
Author:J.M. Smith Termodinamica en ingenieria quimica, Hendrick C Van Ness, Michael Abbott, Mark Swihart
Publisher:J.M. Smith Termodinamica en ingenieria quimica, Hendrick C Van Ness, Michael Abbott, Mark Swihart
Chapter1: Introduction
Section: Chapter Questions
Problem 1.1P
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Transcribed Image Text:Using the equations from the last page, work out and answer the following questions:
1. If a parcel of air at 15°C has a specific humidity of 4.6 g/kg, what is the relative humidity of that parcel?
- **Answer: 41%**
2. If the parcel were warmed to 25°C with no change in water vapor content (SH), what would be its new relative humidity?
- **Answer: 5%**
3. Considering your answer for question 2, describe the relationship between relative humidity and temperature, assuming constant specific humidity.
- **Explanation:** The relationship between humidity and temperature, assuming constant humidity, is that they are inversely proportional. If temperature increases, it will lead to a decrease in relative humidity. The air will become drier, whereas when temperature decreases, the air will become wetter, meaning the relative humidity will increase.
4. What is the dew point temperature of an air parcel with a specific humidity of 11.2 g/kg?
- **Answer: 15°C**
5. A parcel of air at 20°C has a relative humidity of 40 percent. What is its dew point temperature?
- **Answer: 6.0°C**
6. Considering your responses to the questions above, do you need to know an air parcel’s temperature or its specific humidity to determine its dew point temperature?
- **Explanation not provided.**
![**Unit 5 Lab: Moisture in the Atmosphere**
**Part 1: Measures of Atmospheric Humidity**
As you know, the atmosphere has only a limited ability to store water vapor. When that limit is reached, the atmosphere is said to be saturated. More than anything else, the saturation point is determined by temperature. For example, Table 1 shows water vapor capacity on a mass basis.
**Table 1: Saturation Specific Humidity at 1013 mb (Sea Level Pressure)**
| Temperature | Saturation Specific Humidity (g/kg) |
|-------------|-------------------------------------|
| °F | °C | |
| 23 | -5 | 2.6 |
| 32 | 0 | 4.0 |
| +1 | 5 | 5.7 |
| 50 | 10 | 8.1 |
| 59 | 15 | 11.2 |
| 68 | 20 | 15.4 |
| 77 | 25 | 20.9 |
| 86 | 30 | 28.2 |
| 95 | 35 | 37.5 |
| 104 | 40 | 49.6 |
The graph on the right displays the relationship between temperature (°C) and vapor (g/kg). It shows that as temperature increases, the saturation specific humidity also increases, which describes the non-linear, upward trend of vapor capacity.
**Relative Humidity (RH)** is the proportion of the amount of water vapor present at a given temperature relative to the maximum quantity that could be present. In other words, relative humidity is the ratio of the specific humidity (SH) of a given volume of air to the saturation specific humidity (SSH) of a volume of air at the same temperature. We express relative humidity as a percentage.
We can determine relative humidity by using the following equation:
\[ RH = \frac{SH}{SSH} \times 100 \]
We can find SH and SSH values as follows:
- SH = RH (SSH)
- SSH = SH/RH](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F1a2be487-a4f1-4704-8a71-b11163658c73%2F6f17c7a0-d241-40cf-9371-6301f8779d19%2Frw6gvu5_processed.png&w=3840&q=75)
Transcribed Image Text:**Unit 5 Lab: Moisture in the Atmosphere**
**Part 1: Measures of Atmospheric Humidity**
As you know, the atmosphere has only a limited ability to store water vapor. When that limit is reached, the atmosphere is said to be saturated. More than anything else, the saturation point is determined by temperature. For example, Table 1 shows water vapor capacity on a mass basis.
**Table 1: Saturation Specific Humidity at 1013 mb (Sea Level Pressure)**
| Temperature | Saturation Specific Humidity (g/kg) |
|-------------|-------------------------------------|
| °F | °C | |
| 23 | -5 | 2.6 |
| 32 | 0 | 4.0 |
| +1 | 5 | 5.7 |
| 50 | 10 | 8.1 |
| 59 | 15 | 11.2 |
| 68 | 20 | 15.4 |
| 77 | 25 | 20.9 |
| 86 | 30 | 28.2 |
| 95 | 35 | 37.5 |
| 104 | 40 | 49.6 |
The graph on the right displays the relationship between temperature (°C) and vapor (g/kg). It shows that as temperature increases, the saturation specific humidity also increases, which describes the non-linear, upward trend of vapor capacity.
**Relative Humidity (RH)** is the proportion of the amount of water vapor present at a given temperature relative to the maximum quantity that could be present. In other words, relative humidity is the ratio of the specific humidity (SH) of a given volume of air to the saturation specific humidity (SSH) of a volume of air at the same temperature. We express relative humidity as a percentage.
We can determine relative humidity by using the following equation:
\[ RH = \frac{SH}{SSH} \times 100 \]
We can find SH and SSH values as follows:
- SH = RH (SSH)
- SSH = SH/RH
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