How do I find an enthelpy value if my temp. is below 50 deg. celcius?

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    Enthalphy Value Water
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Discussion Overview

The discussion revolves around finding the enthalpy value of water in the context of designing a curding machine that operates under isobaric conditions. Participants explore the use of Mollier diagrams and steam tables to determine enthalpy values for water at temperatures ranging from 25 to 75 degrees Celsius.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant inquires about using a Mollier diagram to find the enthalpy of water at temperatures between 25 and 75 degrees Celsius.
  • Another participant asks about the heat capacity of water, emphasizing its significance in determining temperature changes.
  • Several participants discuss the equation for change in enthalpy, $$\Delta H=mC_p\Delta t$$, under the assumption of no phase change.
  • There is a suggestion that using steam tables may be simpler and more accurate than using a Mollier diagram, particularly for a liquid stream.
  • One participant expresses confusion about the relevance of the moisture parameter in the Mollier diagram for their application.

Areas of Agreement / Disagreement

Participants express differing opinions on the appropriateness of using Mollier diagrams versus steam tables for determining enthalpy. While some suggest steam tables are more straightforward, others defend the use of Mollier diagrams, indicating a lack of consensus on the best approach.

Contextual Notes

Participants do not reach a definitive conclusion regarding the best method for finding enthalpy values, and there are indications of varying levels of understanding of the underlying concepts.

bakharuddin
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I want to design a curding machine (Milk to Cheese) with an open system that operate at isobaric process (contant pressure),
P = 1 atm = 1,... bar
the range of temperature is = 25-75 0C
can i find an enthalpy of water from Mollier Diagram if my temp. is 25 to 75 degree celsius ? how ?

from my view, i must separates water properties from milk to make curds.
so i use mollier diagram but still confuse about it.

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What is the heat capacity of water?
 
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Chestermiller said:
What is the heat capacity of water?
the amount of heat needed to raise its temperature a certain amount. One of water's most significant properties is that it takes a lot of heat to it to make it get hot. Precisely, water has to absorb 4,184 Joules of heat for the temperature of one kilogram of water to increase 1 degree celsius (°C)
 
bakharuddin said:
the amount of heat needed to raise its temperature a certain amount. One of water's most significant properties is that it takes a lot of heat to it to make it get hot. Precisely, water has to absorb 4,184 Joules of heat for the temperature of one kilogram of water to increase 1 degree celsius (°C)
So, why can't you use this to get the enthalpy of water at 50 C (consistent with the Mollier diagram reference state)?
 
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Chestermiller said:
So, why can't you use this to get the enthalpy of water at 50 C (consistent with the Mollier diagram reference state)?

is there any equation to help me maybe ? still confuse to use this diagram :H
 
bakharuddin said:
is there any equation to help me maybe ? still confuse to use this diagram :H
Why are you using a Mollier diagram? Why aren't you using the Steam Tables? The change in enthalpy with respect to temperature is $$\Delta H=mC_p\Delta t$$assuming no change of phase.
 
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Chestermiller said:
Why are you using a Mollier diagram? Why aren't you using the Steam Tables? The change in enthalpy with respect to temperature is $$\Delta H=mC_p\Delta t$$assuming no change of phase.

because from mollier diagram there is an x value which is a moisture of water parameter, and i think is a must factor to include.
am i wrong ? or is it more simple using steam table to get the enthalpy ?
 
bakharuddin said:
because from mollier diagram there is an x value which is a moisture of water parameter, and i think is a must factor to include.
am i wrong ? or is it more simple using steam table to get the enthalpy ?
The moisture parameter gives the fraction that’s vapor, but, in your case, you have purely a liquid stream, right? It is, of course, simpler to use the steam tables(or even the equation), and it’s more accurate than reading off a graph. You seem to need to review thetmo to get the basic concepts down pat.
 
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Chestermiller said:
The moisture parameter gives the fraction that’s vapor, but, in your case, you have purely a liquid stream, right? It is, of course, simpler to use the steam tables(or even the equation), and it’s more accurate than reading off a graph. You seem to need to review thetmo to get the basic concepts down pat.

Okay ill try it using the steam table.
Thanks you sir, i really appreciate that. glad someone can help here :smile::smile::smile::smile::smile:
 
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