Checking Work on Condensing Steam: A Challenge!

In summary, the conversation is discussing the condensation of steam in a certain amount of water at a specific temperature. The maximum amount of steam that can be condensed is 8.25kg. Additionally, if only 5g of steam is condensed, the final temperature of the water would be 19.99°C. However, the calculations provided in the conversation contain a mistake and should be corrected using the heat of vaporization for liquid water to steam.
  • #1
dustybray
10
0
I'm not sure if I'm approaching these problems correctly. Could someone check my work?

Steam at 100°C is condensed in 500g of water at 20°C.

a. What is the maximum amount of steam that can be condensed in this amount of water?

Q[steam] = m[steam] * L[c steam] * (T[f] – T)
Q[steam] = m * 2*10^4 * (20 - 100)
Q[steam] = m * -1.6*10^6 J

Q[water] = m[water] * L[v water] * (T[f] – T)
Q[water] = .5kg * 3.33*10^5 * (100°C – 20°C)
Q[water] = 1.32*10^7

Q[steam] + Q[water] = 0

m * -1.6*10^6 J + 1.32*10^7 = 0

m = (- 1.32*10^7) / (-1.6*10^6 J)

m = 8.25kg

I don't even know what a reasonable answer would be...


b. If only 5g of steam are condensed, what is the final temperature of the water?

Q[steam] = m[steam] * c[steam] * (T[f] – T)
Q[steam] = .005kg * 2*10^4 * (T – 100)
Q[steam] = 100*T – 1*10^4

Q[water] = m[water] * c[water] * (T[f] – T)
Q[water] = .5kg * 3.33*10^5 * (T – 20°C)
Q[water] = 1.67*10^5 * T – 3.33*10^6

Q[steam] + Q[water] = 0

100*T – 1*10^4 + 1.67*10^5 * T – 3.33*10^6 = 0

100 * T + 1.67*10^5 * T = 1*10^4 + 3.33*10^6

T (100 + 1.67*10^5) = 1*10^4 + 3.33*10^6

T = (1*10^4 + 3.33*10^6) / (100 + 1.67*10^5)

T = 19.99°C


(I know most of the units are missing-- I'm just lazy... :)

Thanks,

dusty...
 
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  • #2
There is a mistake in the calculations. The steam condenses from vapor to liquid at the saturation temperature (100°C) at 1 atm (101.325 kPa). There is no temperature change during condensation. The water does increase from 20° to 100°C, which is correct.

Please refer to - http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/phase2.html#c3

Use heat of vaporization of 2.26 J/kg (539 cal/g) for liquid water to steam, which is the heat given up when condensing from vapor to liquid.
 
  • #3
Thanks Astonuc-- my results seem much more realistic now :)
 

1. What is the purpose of checking work on condensing steam?

The purpose of checking work on condensing steam is to ensure that the steam turbine is operating efficiently and effectively. This involves monitoring the various parameters and performance indicators to identify any potential issues or areas for improvement.

2. What are the key parameters to monitor when checking work on condensing steam?

The key parameters to monitor include steam pressure, temperature, flow rate, and quality. Additionally, factors such as turbine speed, power output, and condenser vacuum should also be closely monitored.

3. How often should work on condensing steam be checked?

The frequency of checking work on condensing steam will depend on the specific system and operating conditions. However, it is generally recommended to monitor the parameters at least once a day or during every shift.

4. What are some common issues that can be identified during work on condensing steam?

Some common issues that can be identified include leaks or blockages in the steam system, low turbine efficiency, and poor condenser performance. These issues can lead to decreased power output and increased maintenance costs if not addressed promptly.

5. How can work on condensing steam be improved?

Work on condensing steam can be improved by regularly monitoring and analyzing the parameters, identifying and addressing any issues promptly, and implementing preventive maintenance measures. Additionally, continuous training and education of personnel can also help improve the overall performance of the steam turbine system.

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