Design, Development and Testing of Flexible Heat Pipe for GEO Imaging Satellite (GISAT)

Abstract

With increasing need of real time data for satellite communication, it needs more number of on board active components. There is a problem of high heat dissipation associated with it. For efficient performance of satellite, it is necessary to maintain the temperature of various components and subassemblies within certain limits. So there is a need for an efficient thermal management system such as a heat pipe arrangement which can transfer such high heat ux with minimum temperature drop. Heat pipes passive operation removes the need for an expensive solutions for on board system of much costlier spacecraft electronics components. Since various imaging instruments are optically aligned with certain micron accuracies, its performance becomes very sensitive to mounting forces generated under clamping loads provided through fasteners. Cryo cooler assembly carries sensitive parts aligned at the focal plane, hence connecting of heat pipe to cryo cooler assembly should ideally be stress free so that any misalignment of heat pipe does not affect the focal plane assembly. This demands for a exible heat pipe which can provide exibility to such assembly. The work described herewith is carried out on a exible heat pipe as one of the potential heat transfer device which needs higher attention for effective thermal management along with optical alignment. The outcome of the literature survey conducted on the heat pipe shows that the work reported/ published in this field, is insufficient to provide solutions for very high heat dissipation with optical alignment for present and future needs in this domain. The exible heat pipe in particular has been least explored as an option amongst heat pipe. In the present study, a exible heat pipe of approximately 200 mm in length, 9 mm in diameter and with operating temperature range of 50 oC to 25 oC was designed. The flexible heat pipe was made of stainless steel and acetone was used as a working fluid. The wick structure was made of stainless steel wire mesh of 200 mesh size. The exibility in heat pipe structure was achieved by using stainless steel exible bellow. Experimental trials were conducted with different charging pressure and charging fluid quantity to optimize the heat pipe performance. The developed exible heat pipe was tested in ground to check its thermal performance. The heat pipe performance was quanti ed in terms of thermal conductance and e ective thermal conductivity. The temperature di erence across heat pipe end at 8 W heat dissipation was 12.249 oC with thermal conductance and e ective thermal conductivity of 0.653 W/K and 2053.26 W/mK respectively. Heat pipe was also tested for its exibility. Flexibility test aimed to determine the sti ness of heat pipe and the achieved sti ness in Y & Z direction was 1.1 N/mm. An outsourced copper exible heat pipe of 9.4 mm diameter and 285 mm length was tested in ground condition. An outsourced copper sintered rigid heat pipe was tested in ground and thermo-vacuum condition to check its performance. In addition to this, rigid heat pipe with axially grooved type wick structure was also designed. The study concluded to suggest further improvements in the design of existing flexible heat pipe parameters to meet the thermal load requirement and for miniatur-isation of heat pipe.