Question Regarding Sensible Heat

[gunster]

I've always learned that sensible heat vs. latent heat was just a difference in temperature change with respect to enthalpy changes, where sensible heat occurs when heat causes temperature to change.

However, I was wondering for a specific fluid: if you had a enthalpy vs. temperature diagram, and you increase the enthalpy of the fluid while keeping constant temperature by changing pressure. If you are outside the two-phase envelope while this enthalpy change occurs, is this still considered sensible heat even though temperature is kept constant?

Or basically: is sensible heat a function of both temperature and pressure and can still be nonzero if temperature change is zero?

Thank you in advance

 

[georgeverghese]

Yes, dH can be >0 for cases when dT = 0 as you said.

This is valid for real gas only, where there is a change in Z between the 2 states.

In an ideal gas, dH = 0 when dT=0

For reasons you've described, it is preferable not to use the phrase " sensible heat " in thermodynamics. It is more in common use in heat transfer equipment design where enthalpy changes do not involve pressure changes.

 

[gunster]

Ah okay.

I understand dH can be >0 when dT=0 for real gases.

I was wondering in terms of terminology as you mentioned, is this dH still considered "sensible heat" or is there some other terminology to describe it?

 

[georgeverghese]

How about "isothermal enthalpy change"

 

[gunster]

Okay fair enough haha. Thanks for the answer, that pretty much clears the misunderstandings I had in my mind.

 

[Compositepro]

Sensible heat generally refers to heat associated with a temperature change.

 

[chicopee]

Another way to visualize sensible heat is the heat generated by equipment such as motors,stoves,lighting etc... By contrast latent heat is due to a change in temperature of a substance under a solid, liquid, saturated and superheated state. For a human body, the heat generated thru the skin excluding perspiration is sensible heat. Heat release thru perspiration and respiration due to the water wapor and CO2 released into the environment can be viewed as latent heat.

 

[25362]

Usual definitions;

Sensible heat: The heat absorbed or evolved by a asubstance during a change in temperature that is not accompanied by a change of state.

Latent heat: The amount of heat absorbed or evolved by 1 mole, or a unit mass, of a substance during a change of state (such as fusion, sublimation or vaporization) at constant temperature and pressure.