Abstract
A loop heat pipe (LHP) is a kind of passive heat transfer device that uses the latent heat of the working fluid and the capillary forces of the capillary wicks. It demonstrates high heat transfer efficiency, long-distance heat transfer, and high pipeline flexibility. The multi-evaporator loop heat pipe (MeLHP) is a special loop heat pipe with multiple evaporators so that heat collection and emission from multiple heat sources can be achieved. In this paper, a new type of the multi-evaporator loop heat pipe prototype with a dual-layer condenser was designed, which can ensure the uniform and symmetrical layout of pipelines. The working temperature was 20°C, and propylene was used as the working fluid. The performance of the same evaporator in a single-loop LHP was considered as a reference. The experiment was conducted under two heating modes, i.e. single-evaporator heating and multi-evaporator heating, and the working stability of the prototype was verified by applying periodic heating power change and adverse elevation condition. It was observed that the prototype can be successfully started in different heating modes with a heat transfer limit of 230 W. In the test, the four loops were different in heat transfer limit due to the differences of flow resistance, and less power distribution to the loop with lowest heat transfer limit was considered to be beneficial to the prototype’s performance. Meanwhile, the prototype showed good heat sharing characteristic as the maximum temperature difference is low (smaller than 2 K in single-evaporator heating mode and 0.5 K in multi-evaporator heating mode). The prototype was of good operational reliability and found to be adaptable to the adverse elevation and cyclic variation of the heating power to a certain extent.
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Abbreviations
- A :
-
pipe cross sectional area/m2
- D :
-
pipe diameter/m
- d :
-
pipe local diameter/m
- f :
-
friction loss factors
- L :
-
length/m
- M :
-
mass/kg
- m :
-
mass flow rate/kg·s−1
- N :
-
number of evaporators
- P :
-
pressure/Pa
- Q :
-
heat load/W
- R :
-
flow resistance/Pa·s2·kg−2
- T :
-
temperature/K
- r :
-
radius/m
- u :
-
volume flow rate/m3·s−1
- V :
-
volume/m3
- β :
-
charging ratio
- ζ :
-
local resistance factors
- θ :
-
bend radian of the pipe/rad
- κ :
-
permeability of the wick/m2
- μ :
-
dynamic viscosity/Pa·s
- π :
-
circumference ratio
- ρ :
-
density/kg·m−3
- σ :
-
surface tension/N·m−1
- aver:
-
average
- cc:
-
compensation chamber
- g,s:
-
saturated gas
- j:
-
local resistance
- l:
-
friction loss
- l,s:
-
saturated liquid
- max:
-
the maximum case
- me:
-
in the MeLHP
- min:
-
the minimum case
- s:
-
variable
- se:
-
in the single-loop LHP
- total:
-
the whole prototype
- w:
-
wick
- w,o:
-
outer radius of the wick
- w,i:
-
inner radius of the wick
- ID:
-
internal diameter
- LHP:
-
loop heat pipe
- MeLHP:
-
multi-evaporator loop heat pipe
- OD:
-
outer diameter
- RTD:
-
resistance temperature detectors
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Acknowledgment
The work presented in this paper is supported by the National Natural Science Foundation of China (Grant No. 51776121).
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Lu, D., Xie, R. & Wen, J. Experimental Study on a Multi-Evaporator Loop Heat Pipe with a Dual-Layer Structure Condenser. J. Therm. Sci. 32, 1466–1476 (2023). https://doi.org/10.1007/s11630-023-1829-4
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DOI: https://doi.org/10.1007/s11630-023-1829-4