How Do I Calculate Heat Flux for Water Flowing Through a Channel?

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Discussion Overview

The discussion revolves around calculating heat flux for water flowing through a channel, specifically in the context of using water as a coolant. Participants explore methods for determining heat flux and vapor quality based on given properties and flow rates.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Homework-related

Main Points Raised

  • One participant inquires about calculating heat flux given the mass flow rate and inlet properties of water, with the outlet having a vapor quality of 1.
  • Another participant suggests using steam tables to find the heat removed as equal to the difference in enthalpy, indicating a formula involving dQ = dH.
  • A participant expresses gratitude for the suggestion regarding the use of steam tables.
  • A subsequent post shifts the focus to calculating vapor quality, given the heat flux and mass flow rate, requesting the relevant formula.
  • Another participant responds by reiterating the use of enthalpy differences to find the outlet enthalpy and provides a method to determine vapor quality using the relationship between specific enthalpy and the quality of the vapor.

Areas of Agreement / Disagreement

Participants appear to agree on the use of enthalpy and steam tables for calculating heat flux and vapor quality, but the discussion does not resolve whether there are alternative methods or if the proposed methods are universally applicable.

Contextual Notes

There may be limitations regarding the assumptions made about the properties of water and the specific conditions under which the calculations are performed, such as pressure and temperature dependencies.

Who May Find This Useful

This discussion may be useful for individuals interested in thermodynamics, heat transfer, and fluid mechanics, particularly those working with cooling systems involving water.

banerjeerupak
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Water is being used as a coolant by flowing through a channel. I know the mass flow rate of water. And i know the inlet properties of water. I also know that the water is coming out of the channel at a vapor quality of 1. How do i calculate the heat flux that the water is subjected to during flowing through the channel. I need the formula or the direction in which i can think to figure out the question.
 
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Hi baner,
The easiest thing to do is just use steam tables. The heat removed is equal to the difference in enthalpy.
dQ = dH
 
Thank you Q,

That was helpful.

-Rupak
 
now there is a change in the calculations i need to perform. I have the heat flux and the mass flow rate. How should i go about calculating the vapor quality. I couldn't remember the formula, so thought of asking here.
 
You can use the same method.
Qin = Hout - Hin
so
Hout = Qin - Hin
Note: the above Qin and H have units of energy per unit time. H therefore, is the specific enthalpy (h) times mass flow rate.

Once you have hout (units are energy per unit mass) go to your steam tables. Given the pressure on the outlet, you can determine the quality by applying the following and solving for x :
hout = hf + x hfg
 

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