Mathematical Modeling of a Miniature Loop Heat Pipe With Two Evaporators and Two Condensers

2009 ◽  
Author(s):  
Jentung Ku ◽  
Triem Hoang ◽  
Tamara O’Connell
Keyword(s):  
Steady State ◽  
Heat Pipe ◽  
Analytical Model ◽  
Computer Code ◽  
Loop Heat Pipe ◽  
Performance Tests ◽  
Thermal Vacuum ◽  
Start Up ◽  
Gravity Effects ◽  
Transient Thermal

A loop heat pipe (LHP) analytical model that simulates the steady state and transient thermal behaviors of LHPs with multiple evaporators and multiple condensers has recently been developed. It can be used as a stand-alone computer code or as a subroutine to general spacecraft thermal analyzers. Multi-evaporator and multi-condenser LHPs are more complex in their operation when compared to single-evaporator LHPs because of the thermal and fluid interactions among the evaporators, compensation chambers, and condensers. This analytical model has been used to simulate the thermal performance of a miniature loop heat pipe (MLHP) with two evaporators and two condensers in laboratory and thermal vacuum tests. In addition, the MLHP was tested in the laboratory under five different configurations where the relative elevations and tilts among loop components were varied so as to investigate the gravity effects on the loop performance and to verify the analytical model’s capability to predict such effects. The MLHP performance tests that were simulated included start-up, high power, heat transport limit, and heat load sharing between the two evaporators. In all tests that were modeled, the LHP analytical model accurately predicted the steady state and transient behaviors of the LHP. Furthermore, the model was run-time efficient and yielded stable solutions in all cases.

STEADY-STATE ANALYTICAL MODEL OF A LOOP HEAT PIPE

2014 ◽  
Vol 5 (1-4) ◽  
pp. 279-286
Author(s):  
Benjamin Siedel ◽  
Valerie Sartre ◽  
Frederic Lefevre
Keyword(s):  
Steady State ◽  
Heat Pipe ◽  
Analytical Model ◽  
Loop Heat Pipe

Thermal Vacuum Testing of a Miniature Loop Heat Pipe With Multiple Evaporators and Multiple Condensers

2007 ◽  
Author(s):  
Jentung Ku ◽  
Laura Ottenstein ◽  
Hosei Nagano
Keyword(s):  
Low Power ◽  
Heat Pipe ◽  
Temperature Control ◽  
Heat Load ◽  
Operating Temperature ◽  
Loop Heat Pipe ◽  
Thermal Vacuum ◽  
Heater Power ◽  
Start Up ◽  
Vacuum Testing

This paper describes thermal vacuum testing of a miniature loop heat pipe (MLHP) with two evaporators and two condensers designed for future small systems applications requiring low mass, low power and compactness. Each evaporator contains a wick with an outer diameter of 6.4 mm, and each has its own integral compensation chamber (CC). Multiple evaporators provide flexibility for placement of instruments that need to be maintained at the same temperature, and facilitate heat load sharing among instruments, resulting in a reduced auxiliary heater power requirement. A flow regulator is used to regulate heat dissipations among all condensers, thus providing flexibility for placement of radiators on the spacecraft. A thermoelectric converter (TEC) is attached to each CC for operating temperature control and enhancement of start-up success. Tests performed include start-up, power cycle, sink temperature cycle, high power and low power operation, heat load sharing, and operating temperature control. The MLHP demonstrated excellent performance in the thermal vacuum environment. The loop started successfully and operated stably under various evaporator heat loads and condenser sink temperatures. The TECs were able to maintain the loop operating temperature within ±0.5K of the desired set point temperature at all power levels and all sink temperatures. The un-powered evaporator would automatically share heat from the other powered evaporator. The CC control heater power was reduced by more than 50 percent when a TEC was used instead of conventional electrical heaters. The flow regulator was able to regulate the heat dissipation among the radiators and prevent vapor from flowing into the liquid line.

Steady-State Modelling of Dual-Evaporator Loop Heat Pipe

2021 ◽  
pp. 116933
Author(s):  
Y. Qu ◽  
S. Qiao ◽  
D. Zhou
Keyword(s):  
Steady State ◽  
Heat Pipe ◽  
Loop Heat Pipe

Thermal-Vacuum Test Data For Jem/Maxi Loop Heat Pipe System With Two Radiators

2008 ◽  
Author(s):  
Shiro Ueno ◽  
Dmitry Khrustalev ◽  
Peter Cologer ◽  
Russ Snyder
Keyword(s):  
Heat Pipe ◽  
Test Data ◽  
Loop Heat Pipe ◽  
Thermal Vacuum ◽  
Pipe System ◽  
Vacuum Test

Experimental study of heat transfer and start-up of loop heat pipe with multiscale porous wicks

2017 ◽  
Vol 117 ◽  
pp. 782-798 ◽  
Author(s):  
Xianbing Ji ◽  
Ye Wang ◽  
Jinliang Xu ◽  
Yanping Huang
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Heat Pipe ◽  
Loop Heat Pipe ◽  
Start Up

scholarly journals A Novel Analytical Modeling of a Loop Heat Pipe Employing Thin-Film Theory: Part II—Experimental Validation

Energies ◽  
2019 ◽  
Vol 12 (12) ◽  
pp. 2403 ◽  
Author(s):  
Eui Guk Jung ◽  
Joon Hong Boo
Keyword(s):  
Steady State ◽  
Heat Pipe ◽  
Film Theory ◽  
Design Parameters ◽  
Working Fluid ◽  
Coolant Temperature ◽  
Loop Heat Pipe ◽  
Analysis Model ◽  
Proposed Model ◽  
Flat Evaporator

Part I of this study introduced a mathematical model capable of predicting the steady-state performance of a loop heat pipe (LHP) with enhanced rationality and accuracy. Additionally, investigation of the effect of design parameters on the LHP thermal performance was also reported in Part I. The objective of Part II is to experimentally verify the utility of the steady-state analytical model proposed in Part I. To this end, an experimental device comprising a flat-evaporator LHP (FLHP) was designed and fabricated. Methanol was used as the working fluid, and stainless steel as the wall and tubing-system material. The capillary structure in the evaporator was made of polypropylene wick of porosity 47%. To provide vapor removal passages, axial grooves with inverted trapezoidal cross-section were machined at the inner wall of the flat evaporator. Both the evaporator and condenser components measure 40 × 50 mm (W × L). The inner diameters of the tubes constituting the liquid- and vapor-transport lines measure 2 mm and 4 mm, respectively, and the lengths of these lines are 0.5 m. The maximum input thermal load was 90 W in the horizontal alignment with a coolant temperature of 10 °C. Validity of the said steady-state analysis model was verified for both the flat and cylindrical evaporator LHP (CLHP) models in the light of experimental results. The observed difference in temperature values between the proposed model and experiment was less than 4% based on the absolute temperature. Correspondingly, a maximum error of 6% was observed with regard to thermal resistance. The proposed model is considered capable of providing more accurate performance prediction of an LHP.

Effect of Sink Temperature on the Stability of the Pressure-Controlled Loop Heat Pipe

2019 ◽  
Vol 141 (9) ◽  
Author(s):  
Wukchul Joung ◽  
Joohyun Lee
Keyword(s):  
Heat Pipe ◽  
Temperature Control ◽  
Control Technique ◽  
Loop Heat Pipe ◽  
Heat Leak ◽  
Start Up ◽  
Recent Emergence ◽  
Compensation Chamber ◽  
The Stability ◽  
Pressure Controlled

Recently, a novel temperature control technique utilizing the unique thermohydraulic operating principles of the pressure-controlled loop heat pipes (PCLHPs) was proposed and proved its effectiveness, by which a faster and more stable temperature control was possible by means of the pressure control. However, due to its recent emergence, the proposed hydraulic temperature control technique has not been fully characterized in terms of the various operating parameters including the sink temperature. In this work, the effect of the sink temperature on the loop heat pipe (LHP)-based hydraulic temperature control was investigated to improve the stability of the proposed technique. Start-up characteristics and transient responses of the operating temperatures to different pressure steps and sink temperatures were examined. From the test results, it was found that there was a minimum sink temperature, which ensured a steady-state operation after the start-up and a stable hydraulic temperature control with the increasing pressure steps, due to the unstable balance between the heat leak and the liquid subcooling in the compensation chamber at low sink temperatures. In addition, the range of the stable hydraulic temperature control was extended with the increasing coolant temperature due to the decreased heat leak, which resulted in the increased pressure difference between the evaporator and the compensation chamber. Therefore, it was found and suggested that for a stable hydraulic temperature control in an extended range, it was necessary to operate the PCLHP at higher sink temperatures than the low limit.

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