Browsing by Author "Gupta, Rohit"
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Item 3D Printed Wicks for Loop Heat Pipes(2023 International Conference on Environmental Systems, 2023-07-16) Gupta, Rohit; Chen, Chien-Hua; Anderson, William G.This paper describes the development of 3D printed wicks for loop heat pipes. This work is part of an overall effort by Advanced Cooling Technologies, Inc. to develop 3D printed loop heat pipes as a low-cost, rapidly-manufacturable alternative technology to standard loop heat pipes for future high-performance small spacecraft. The wicks were built using laser powder bed fusion of standard 316L SS powder. The build parameters were varied by controlling a custom variable called the energy density to produce an assortment of wicks with different capillary metrics, i.e., porosity, permeability, and maximum pore radius. The variation in the capillary metrics, determined using a combination of capillary flow porometry and mercury intrusion porosimetry, was studied with respect to the energy density. The pore distribution was also studied by analyzing in detail the intrusion curves acquired during mercury intrusion porosimetry. The results from this study can serve as general guidelines for building future 3D printed wicks for loop heat pipes with the desired capillary performance.Item Experiments on a Loop Heat Pipe with a 3D Printed Evaporator(51st International Conference on Environmental Systems, 7/10/2022) Gupta, Rohit; Chen, Chien-Hua; Anderson, WilliamThe construction and testing of a loop heat pipe with a 3D printed evaporator is described in this paper. The system was developed as part of a larger engineering demonstration unit for thermal management on NASA's Volatiles Investigating Polar Exploration Rover. A state-of-the-art 3D printed evaporator, developed in a previous effort, was used in the current system. This evaporator had a cylindrical geometry with a length of 0.1 m and a diameter of 0.025 m and featured a primary wick with a bubble point pore radius of under 8 µm. The vapor, condenser, and liquid lines were constructed from 0.003 m diameter tubing and routed to conform to the geometry of the rover. A thermal control valve was also incorporated in the loop heat pipe to force the vapor to bypass the condenser at a lower-than-threshold temperature. The loop heat pipe was tested successfully under a range of thermal loads of up to 70 W against a mission-expected load of 50 W. Due to startup difficulties observed at the low condenser temperatures, a series of dedicated startup tests were conducted to identify the underlying causes and to study the effects of major variables, such as the heat location and charge quantity. Based on this analysis, a number of changes were identified to help improve the startup performance of the system.Item Progress on 3D Printed Loop Heat Pipes(50th International Conference on Environmental Systems, 7/12/2021) Gupta, Rohit; Chen, Chien-Hua; Anderson, WilliamThe rapid growth of the miniaturized satellite industry has led to increased demand for low-cost and robust thermal management systems. Advanced Cooling Technologies, Inc. has been developing Loop Heat Pipes with 3D printed evaporators in an effort to reduce manufacturing costs and lead times by eliminating labor-intensive processes that are otherwise involved in the fabrication of standard evaporators. These processes include, but are not limited to, the primary wick fabrication, wick insertion, and knife-edge seal. The reported work describes the latest progress in this technology in the areas of primary wick advancement and thermal performance improvement. Following iterative optimization in this work, the pore size of the 3D printed wick was reduced to a sub-5-micron level, with a maximum radius of 4.9 ?m. A new evaporator was 3D printed, featuring a refined primary wick and a fully-dense front wall, in order to prevent vapors from the vapor plenum being forced back into the evaporator under strong adverse pressure gradients. The overall thermal conductance of the system was improved by over 15% by incorporating a new saddle design with a single, connected structure and featuring a horizontal clamping mechanism. The new 3D printed evaporator assembly was also shown to operate successfully at a steady state power level of 350 W using line tubing with diameter of 0.003 m and ammonia as the working fluid.