Numerical and Experimental Study of Loop Heat Pipe Steady-State Performance

• Published in: Thermal engineering Vol. 69; no. 3; pp. 190 - 201
• Main Authors: Belov, A. E., Velikanov, A. A., Il’mov, D. N., Nagornova, O. A., Sobolev, V. V., Filatov, N. I.
• Format: Journal Article
• Language: English
• Published: Moscow Pleiades Publishing 01-03-2022; Springer Nature B.V
• Subjects: Confined spaces; Coolants; Deviation; Engineering; Engineering Thermodynamics; Evaporators; Heat; Heat and Mass Transfer; Heat and Mass Transfer and Properties of Working Fluids and Materials; Heat flux; Heat pipes; Heat transfer; Loop heat pipes; Mass transfer; Mathematical models; Motional resistance; Pipes; Radiators; Room temperature; Steady state; Superheating; Test chambers; Thermophysical models; Thermophysical properties; Vapors; Weight reduction; spacecrafts; capillary effect; capillary pump; thermal regime maintenance system; heat pipe; loop heat pipe
• ISSN: 0040-6015; 1555-6301
• DOI: 10.1134/S0040601522030028

Loop heat pipes (LHPs) have all the advantages of conventional heat pipes, are less susceptible to gravity effects, and offer better heat-transfer performance. They can readily be used in confined areas. As to temperature maintenance, they are self-regulating devices thereby preventing a considerable decrease in the temperature of the mounting seat of heat-releasing equipment on a heat load reduction. Miniature LHPs can replace conventional heat pipes in promising spacecrafts, while substantially increasing the ability to remove heat and reducing their weight. To develop effective methods for the design of LHPs, physical and mathematical models of conjugated heat and mass transfer in the device are required. This paper presents a procedure for the calculation of the steady-state performance of an LHP. This procedure is to be used to calculate the hydraulic resistance to the motion of liquid and vapor in LHP elements. The heat-transfer ability is determined by the ability of the capillary structure to transport the coolant against the hydraulic resistance. In the second part of the problem, the thermal condition of all elements is calculated using an approach based on the balance of heat fluxes. The model considers the potential vapor superheating in a vapor pipeline. Thermophysical properties of the coolant is calculated in each transport section as a function of the local temperature. The predictions describe the LHP performance quite accurately and agree with the results of testing an experimental loop heat pipe under various conditions at an evaporator temperature from –35 to +25°C. The tests were carried out at room temperature or in a climatic chamber, when the temperature of the radiator was almost equal to the temperature of the environment. The maximum deviation of the predicted evaporator temperature from the measured one was less than 5°С with the average deviation being below 3°С.