I'm studying heat transfer in a commercial heat pipe for solar collector.The heat pipe condenser section is attached to the solar collector manifold, and water at different rates of temperature flows through it. The evaporator section receives energy from an electric heater. The heat pipe is set in many inclinations from horizontal (20°,30°,40°,60°,80°,90° ). The tests are made with indoor testing bench using the collector solar structure. The heat pipe is assembled with the condenser above the evaporator.
In the first moment of the test I do not turn on the electric heat. First I circulate the water at a given "x" temperature through this system to get a homogeneous (and steady state), after this I turn the electric heat on.
So when the water's temperature is higher than the ambient temperature I have in this first moment of the test the heat pipe working reverse. That means the condenser acts as a evaporator and the evaporator acts like a condenser...
I measure the temperature before and after the condenser section (I know that this is not the real temperature of the water flowing through the condenser section, but I couldn't measure the water's temperature direct on it) the error of measurement is +-0,1°C. Also I have measure of temperature at outer surface of evaporator section at different lengths (error is +-1°C). (In the cases of 60°,80° and 90° tilts I have the temperature measure at the condenser section).
So for the case where initial system temperature is 20°C (measure take at point before the condenser section), the circulating water temperature is set to be +- 45°C and the average ambient temperature is 19,2°C. The tilt is 60°. In such scenario I have an increment in the temperature at the point after the condenser.
My question is at this conditions it would be possible that the energy delivered in the condenser section (in this case acting like an evaporator) is increasing the vapor's temperature (inside the heat pipe) and in some way it releases back some heat to the water circulating? Because this is not pure heat transfer it has phase change, but I don't know if this kind of behavior can happen in only on place (in this case the condenser). Also I don't know anything about the working fluid and inside pressure of the heat pipe. (I think is water because is a commercial heat pipe for evacuated solar collector application). Also I really want to see some paper that brings data for heat pipe when the evaporator is above the condenser (preferable not loop heat pipe or pulsating heat pipe). Any help about this would be extremely appreciated.
I attached an example of the result that I got.
The plot shows:
blue line that means the difference between temperature after and before the condenser section. SCON means the temperature at the condenser. SEV1 is a temperature at the evaporator at 0,04m bellow condenser, SEV2 is a temperature at the evaporator at 0,26m bellow SEV1, and SEV3 is a temperature at the evaporator at 0,26m bellow SEV2.
Crisciele Ferreira dos Santos please follow ans read through the following article it will help you to understand .
Dear Santo
Your work seems to me intresting. Due to axial conduction heat transfer temperature might be increase. One of the advantage of condenser is the temperature of the working fluid stays relatively constant during condensation, which maximizes the temperature difference between the working and secondary fluid.
Santosh Kumar Singh Thank you.
But, could you explain this better? I don't understand how the water (with temperature higher than ambient temperature) passes through the condenser (that in first moment is close to the ambient temperature) delivers some energy to it and then the condenser delivers some energy to this same water. (remembering that in this moment the heat source at the evaporator is not turned on).
This seems to me to violate thermodynamic law...
Hayder Ibrahim Mohammed I really don' t know. That's why I need to know how this phase change behaves. I have been searching answers in papers, so far I haven't found anything... I thought it could be something with increasing in pressure but I don't know... and I can't open the heat pipe because it's a commercial heat pipe for solar collector and I can't use pressure transducer or other instruments...
I have done several works on boiling, evaporation, and condensation. Take a look at the research in my account. You may find something that helps you.
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