How to Understand Sensible Heat Ratio Part One

What is Sensible Heat Ratio? This important concept is hidden within the DNA of all air conditioning systems. Understanding how SHR applies in the field can unlock new levels of understanding for HVAC technicians.
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[@SombraLocs]

Great explanation!

[@mohamedabujreda453]

Great explanation sir, lot of engineers and technicians don't care about this important parameter!!

[@piscis12]

Very good 👏👏

[@rcinfla9017]

How do you get 970 btu's/lb for condensing water vapor? 970 btu/lb happens to be the added enthalpy for jumping liquid to vapor at 212 degs F boiling point of water. Think that is where you are getting your number which is not correct for A/C evaporator temps dew point condensation. Water condensation enthalpy subtracted (hg - hf) equals 1071 to 1060 btu's/lb in the 40 to 60 degs F evaporator temp range, respectively.

[@realSamAndrew]

What is hg-hf? To answer your question, I assume the 970 is the amt of BTU being removed from the AIR in the building space, not from the confines of the evaporator compartment. If you extract a pound of water from your downstairs living room, and your evap is in the attic, you have essentially removed 970 BTUs of latent heat from the house. I want to stress that this is just a hunch based on listening to the presentation of what he means. It could be wrong, but it makes sense.

[@rodgraff1782]

It’s called the latent heat of condensation, not the total heat(enthalpy) Enthalpy is sensible plus latent heat. For water this is 970 BTU’s per pound. This is all latent heat, and cannot be measured with a thermometer. One could hold a container under the condensate line, and when 1 lb of condensate has been removed, it has taken 970 BTU’s. This can also be explained by how a condensing furnace is more efficient than a non condensing furnace. A condensing furnace is recovering 970 BTU’s per pound of condensate from the flue gasses. Otherwise this 970 BTU’s would be lost up the flue.

[@rodgraff1782]

Most AC units will only do about 80% sensible. That means it assumes that at least 20% of the load will be latent.