Heat required to evaporate water.

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Discussion Overview

The discussion revolves around calculating the heat required to evaporate water at temperatures other than 100 degrees Celsius. Participants explore the implications of maintaining constant temperatures of 50 and 70 degrees Celsius for the evaporation process.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant inquires about the heat required to evaporate 1 kg of water at constant temperatures of 50 and 70 degrees Celsius.
  • Another participant suggests using the heat transfer equation Q = mcΔt for calculating heat, noting that this equation typically applies to raising temperature rather than maintaining it.
  • A participant expresses uncertainty about whether the heat required at lower temperatures would equal the latent heat of vaporization at 100 degrees Celsius or if there would be differences.
  • One participant questions the availability of steam tables or psychrometric charts to determine the enthalpy change for water to vapor at specific temperatures.
  • A later reply references a table for latent heat values from 20 degrees C to 230 degrees C, suggesting it may provide relevant data for the discussion.

Areas of Agreement / Disagreement

Participants do not appear to reach a consensus on the heat required for evaporation at temperatures below 100 degrees Celsius, with multiple competing views and uncertainties expressed.

Contextual Notes

Limitations include the lack of access to specific thermodynamic charts and the need for clarification on the application of the heat transfer equation in this context.

adilsyyed
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If 1 kg water is required to be evaporated, not at 100 degree Celsius, how can I calculate the heat required.

Let say a constant temperature of 50 degree Celsius is maintained, then what will be the scenario, and what if the constant temperature of 70 degree Celsius is maintained.
 
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Usually, when calculating the heat required, use the heat transfer equation:

Q= mcΔt

Q=energy, or heat
m=mass
c=specific heat capacity
delta t= change in time
 
Last edited:
makovx said:
Usually, when calculating the heat required, use the heat transfer equation:

Q= mcΔt

Q=energy, or heat
m=mass
c=specific heat capacity
delta t= change in time

Delta T, in my understanding is the change in temperature.

And this equation is for calculating heat required to raise the temperature by certain degree Celsius of the given material.

I want to keep the temperature constant, that is, supplying the heat through a constant temperature air.

I wonder that will the heat required will be equal to the latent heat of vaporization of water (as it is on 100 degree Celsius), or should there be any difference.
 
You do not have access to steam tales or a psychrometric chart or a Mollier diagram to determine the enthalpy change from liquid water to vapour at a set temperature?
 

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