what's the enthalpy of feed water at 50 c_ - yahoo! answers
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1/3/13 What's the enthalpy of f eed water at 50 C? - Yahoo! Answers
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What's the enthalpy of feed water at 50 C?
I have a question which supplies the following information.The performance of an oil fired boiler, in producing steam at 10 bar absolute and 0.90 dryness fraction, showed thefollowing results: -Steam produced per hour = 2000kgFeed water temperature = 50COil used per hour = 160kgCalorific value of the fuel = 42.0MJ/kg
Use the appropriate steam table to calculate the thermal efficiency of the boiler under these conditions.
I have got the steam tables but haven't been told (and can't find) the changes the 50 C feed water will make to theoverall efficiency. Can someone tel me how to work out the enthalpy of the water at 50 C please?
4 years ago ( 2009-02-27 08:32:12 +0000 ) Report Abuse
zzwol
Best Answer - Chosen by Voters
E= m * Cp * Tusing Cp = 4.184 J/g-Deg C
T= TEMPERATURE difference (initial water temp & final water temp)
m= mass
4 years ago ( 2009-02-27 09:04:29 +0000 ) Report Abuse
100% 1 Vote
sabyashachi b
In using the steam tables to find the enthalpy, you only have one choice, that is to use the enthalpy of saturatedwater at 50C. From the steam tables, that value is:
209.32 kJ/kg
This may be listed as Hf or hf on the table heading. As feedwater, the actual pressure of the fluid may be abovesaturation, but for subcooled liquids like this, the enthalpy is more dependent on the temperature than the pressure.Since you were directed to the steam tables n the problem, I'd use the number above in your calculation.
Source(s):
power engineer
4 years ago ( 2009-02-27 12:56:41 +0000 ) Report Abuse
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oeman50
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1/3/13 What's the enthalpy of f eed water at 50 C? - Yahoo! Answers
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oeman50