Can a Room Get Warmer Than the Air Being Pumped In?

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SUMMARY

The discussion clarifies that a room cannot exceed the temperature of the air being pumped into it, specifically when the air is heated to 155°F by a wood boiler. To achieve an internal temperature of 175°F for drying oak wood, the water temperature must be at least 175°F or higher. The conversation also highlights that energy flows from hot to cold, meaning that introducing air at a lower temperature will cool the room. Heat pumps are mentioned as an exception, capable of raising room temperatures above the incoming air temperature, but may not be economically viable for wood drying applications.

PREREQUISITES
  • Understanding of thermodynamics principles, specifically heat transfer.
  • Familiarity with wood drying processes and moisture content requirements.
  • Knowledge of heat pump technology and its applications.
  • Experience with temperature measurement and control in kiln environments.
NEXT STEPS
  • Research the principles of heat transfer and thermodynamics in practical applications.
  • Learn about optimal wood drying temperatures and humidity levels for various wood types.
  • Investigate the efficiency and cost-effectiveness of heat pumps for drying applications.
  • Explore methods for recovering waste heat in kiln operations to improve energy efficiency.
USEFUL FOR

Woodworkers, kiln operators, HVAC professionals, and anyone involved in wood drying processes will benefit from this discussion.

kenyanscorpio
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°Hi all,
It has been many years since I was in school, so my phisics is very rusty.

I have a wood boiler that was made for me, that burns my access waist wood. The boiler gets my water to 155°, and maintains it.

I have a "kiln" room that is fully insulated, no windows, insulated doors and a heat exchanger in the room.

I need to get the internal temperature of the wood, Oak, to 175° to ensure it is dry and down to around 6% humiditey.

I was told that a room can get warmer then the air being pumped in. Is this corect? If it is, any idea what temp the room can get.

If this is not correct, any idea how to calculate the water temp required to get to 175°?

Sorry if this is a stupid question, but I can't seem to find an answer.
 
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First of all, wood will 'dry' below 175 degrees. At 175 degrees it would typically take some length of time; at 155 degrees, for example, it would take longer; at 120 degrees, even longer. It would even eventually dry at 32 degrees F...via evaporation of any ice...

If your heated water is 155 degrees, no further heat transfer will occur from the hot water to the room air when the room air reaches that temperature. The air cannot become warmer than the temperature of your heat source...water,air, or whatever. So you need water at 175 degrees of higher to meet you stated objective of 175 degrees room air.
 
I was told that a room can get warmer then the air being pumped in. Is this corect?

Not in the sense you mean. Energy naturally flows from hot to cold. So if you heated the room to say 165F using electricity and then pumped in air at 155F the air would actually cool the room.

A heat pump is an exception. A heat pump can extract energy from air at say 50F and use it to heat a room to say 71F. However I doubt using a heat pump is economic for your application.

If you were drying wood in a kiln using electricity on a regular basis then it might be worth recovering the waste heat from the kiln and using it to heat your house/office.
 

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