Characterizing the Effect of Gravity on a Freezable Water Heat Exchanger with Respect to Flow Orientation

Date

2015-07-12

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Publisher

45th International Conference on Environmental Systems

Abstract

Water-based freezable heat exchangers hold promise to simplify spacecraft thermal control systems through self-regulation of heat rejection as some of the flow channels within the device become blocked with ice. This Phase Change Material (PCM) based heat exchanger approach also adds endothermic heat storage capacity to a thermal control system as the water freezes when the radiator rejects heat to cold thermal environments. It then reduces the net heat load to the radiator by melting the solid-phase coolant during periods of high cabin temperatures or when the spacecraft is in a hot thermal environment. Unfortunately, these heat exchangers are susceptible to catastrophic damage if the volumetric expansion during water freeze is not accommodated. Solving this design challenge is complicated when using ground-based experiments to predict the freeze-thaw behavior and performance of PCM heat exchangers in microgravity, since the fluid behaves differently in space than on Earth. Buoyancy-induced convection and stratification of the flow are absent in microgravity, and thus the fluid momentum and interfacial phenomena dominate the flow behavior and heat exchanger performance. For these reasons, the design and setup of laboratory experiments that provide insight into the effects of gravity on freezable heat exchangers are important. Herein, we describe a test rig that allows us to vary the orientation of the heat exchanger relative to the gravity vector and obtain the data needed to quantify heat exchanger performance and operational behavior under different flow configurations. We present and discuss key results from the freeze-thaw experiments.

Description

Bellevue, Washington
James A. Nabity, University of Colorado, USA
Jordan B. Holquist, University of Colorado, USA
Matthew J. Milanese, University of Colorado, USA
David M. Klaus, University of Colorado, USA
The 45th International Conference on Environmental Systems was held in Bellevue, Washington, USA on 12 July 2015 through 16 July 2015.

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