I'm working on a class of tetrapods similar to mammals with warm blood. I am planning for their metabolisms to be quite high on average, among the carnivores especially. They range in size from two grams to twenty tonnes.
In reality, birds are some of the warmest animals with body temperatures around 40.5 degrees Celsius, or 105 degrees Fahrenheit. Ideally, I planned for them to at least have a body temperature around that of birds. Similarly to birds, they use a large amount of energy to maintain fast reaction times and movement, as those traits are what gave them an ecological advantage. They also have four airsacs in their unidirectional respiratory system.
They cannot sweat. They have never evolved the ability to sweat because of humid and tropical environments.
Due to the risk of their proteins denaturing, I have come up with some sort of biological cooling system to prevent them from overheating. If you have any different ideas from this, I would love to know. Next is mostly a long explanation of my idea.(TL;DR at the end)
After inhalation, the posterior airsacs will be filled with air first, then push air into the small lungs. After deoxygenation, the air will enter the smaller anterior airsacs. There is a system of air vessels throughout the body, mostly present in the abdomen, head, and larger parts of limbs. These are connected to the anterior airsacs. The anterior airsacs are bidirectional, as they push air both out of and into the vessels, or out during exhalation. A one way valve prevents waste air from traveling back into the lungs. The air brought into the body passes by a membrane that allows acetone from an acetone filled vessel to evaporate. I chose acetone because it is volatile and biologically attainable. The then acetone vapor filled air will be exhaled or recirculated for more evaporation. When not in need of cooling, the opening between the anterior airsacs and the body can close.
I made a diagram to better represent the original idea. There is a color key for many of the lines on it, and it is of course simplified. The arrows with a gradient represent evaporation of acetone.
A step by step breakdown:
Inhalation- the air goes to the blue, posterior airsacs
Oxygenation of blood- the air is pushed through the pink lungs
The air is taken in by the orange anterior airsacs and either exhaled or pushed into the body
The air circulates through the body, and acetone evaporates into it through membranes
The vapor is pushed back into the anterior airsacs where it can be exhaled or reused
TL;DR: I'm using acetone to cool a creature by evaporating it into exhaled air.
If there are any suggestions on what I should do to improve it or make it more realistic, they would be appreciated. Even if this would never work, please let me know why. I probably over thought it, but thanks for looking at it.