Thermocapillary Convection Space Experiment on the SJ-10 Recoverable Satellite

Summary

A protocol for the space payload design, the space experiment on thermocapillary convection, and analyses of experimental data and images are presented in this paper.

Abstract

Thermocapillary convection is an important research subject in microgravity fluid physics. The experimental study on surface waves of thermocapillary convection in an annular liquid pool is one of the 19 scientific experimental projects on the SJ-10 recoverable satellite. Presented is a design for a payload for space experimental study on thermocapillary convection that includes the experimental model, measurement system, and control system. The specifics for the construction of an experimental model of an annular liquid pool with variable volume ratios is provided. The fluid temperatures are recorded by six thermocouples with a high sensitivity of 0.05 °C at different points. The temperature distributions on the liquid free surface are captured by means of an infrared thermal camera. The free surface deformation is detected by a displacement sensor with a high accuracy of 1 µm. The experimental process is fully automated. The research is focused on thermocapillary oscillation phenomena on the liquid-free surface and convective pattern transitions through analyses of experimental data and images. This research will be helpful to understand the mechanism of thermocapillary convection and will offer further insights into the nonlinear characteristics, flow instability, and bifurcation transitions of thermocapillary convection.

Introduction

Under microgravity conditions in space, many interesting physical phenomena are presented due to the absence of gravity. In a liquid with a free surface, there exists a new flow system (i.e. thermocapillary flow) that is caused by the temperature gradient or concentration gradient. Different from traditional convection on the ground, thermocapillary convection is a ubiquitous phenomenon in space environments. As it is a very important research subject in microgravity fluid physics, a number of experiments have been carried out in space as well as on the ground. Recently, space experimental studies were performed on thermocapillary convection on the SJ-10 recoverable s....

Protocol

1. Design and preparation of the experimental system

1. Construct the annular liquid pool.
   1. Build a copper annular liquid pool measuring R_i = 4 mm in inner diameter and R_o = 20 mm in outer diameter and d = 12 mm in height.
   2. Use a polysulfone plate measuring R_P = 20 mm in diameter as the bottom of the liquid pool (see Table of Materials).
   3. Drill a small hole measuring ϕ = 2 mm in diameter close to the inner wall (6 mm away from the center of the circle) as the liquid injection hole.
2. Maintain the interface. ....

Results

The accurate volume ratio was defined, and the liquid surface topography was reconstructed based on the images captured by the CCD. The critical instability condition was determined, and the oscillation characteristics were studied through analyses on single point temperature signals and displacement oscillating signals. The structure of the flow field was obtained, and the transition of the flow pattern was determined through the change of the infrared image with time. The flow character.......

Discussion

Due to the limitation of space resources, the volume of the equipment as a whole is only 400 mm × 352 mm × 322 mm, with a weight of only 22.9 ± 0.2 kg. This is very inconvenient when selecting and laying out experimental devices, and the establishment of the flow system becomes the critical step. Therefore, the increasing temperature difference is set at two ends of the liquid pool so that the fluid can generate a series of flow phenomena. In order to observe the entire process of the convection from stead.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
anti-creeping liquid	3M	EGC-1700
CCD	WATTEC	WAT-230VIVID
Displacement sensor	Panasonic	HL-C1
Heating film	HongYu	125 Q/W335.1A
Hydraulic cylinder	FESTO	ADVU-40-25-P-A
Infrared camera	FLIR	Tau2
LED	693 Institute	10257MW7C
Montor	PI	M-227
Montor controller	PI	C-863
Pipe, 4mm	FESTO	PUN-4X0,75-GE
polysulfone plate	507 Institute
Refrigeration chip	Zhongke	9502/065/021M
Silicon oil, 2cSt	Shin-Etsu	KF-96
Solenoid	FESTO	MFH-2-M5
Temperature controller	Eurotherm	3304
Thermocouple, K-type	North University of China	ZBDX-HTTK