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The TEMP 2A-3 experiment was the first flight of a mechanically pumped two-phase ammonia thermal control system. This proof-of-concept mission was successfully flown on the STS-46 Shuttle flight in August 1992. The TEMP experiment performed well and all mission objectives were met. Valuable data has been obtained on two-phase pressure losses, heat transfer coefficients, and fluid management techniques in a micro-gravity environment. Overall temperature control results were excellent and within expected ranges. However, there were substantially more instabilities in the flow when compared with ground test data. Fortunately, the instabilities did not severely affect system operation. A description of the TEMP 2A-3 experiment is given and a comparison of the ground thermal vacuum and flight test data is presented.

Tests were conducted to compare the thermal performance of five types of wafer thin coolers; a double pass microchannel cooler, two types of single pass microchannel coolers, and two versions of an impingement cooler. The primary application of these devices is to remove heat from compact gallium arsenide diode wafers used in laser communications, but they can also be applied to a variety of other applications ranging from high density electronic packaging to hypersonic surfaces. The coolers were designed to absorb heat fluxes of over 100 W/cm2 with minimal surface temperature gradients. The coolers had a heat input area of 1 cm2, used water as the cooling fluid and had thicknesses ranging from 1 to 1.8 mm. One single pass microchannel cooler was made of beryllium oxide. The other four coolers were made of copper. A. special heat flux amplifier was built to obtain the high heat flux values with conventional heaters, and to provide instrumentation to determine temperature gradients.

Developing headers to uniformly distribute two-phase (liquid/vapor) flow is a difficult but important aspect in the design of advanced two-phase thermal control systems. This paper documents experimental efforts toward developing a header to equally distribute the liquid flow to parallel legs of a two-phase heat exchanger. Models of various header concepts were built and tested using air/water mixtures to simulate two-phase liquid/vapor flow. Based on the results of these tests, a Fan Header concept was designed for a specific, parallel tube heat exchanger. At flow rates within the expected range of operation, this Fan Header distributed the liquid within 16% of the equally distributed value for inlet qualities up to 25%.

This paper describes an enhancement to a grooved, evaporative surface for two-phase mounting plates. These equipment mounting plates could be used in two-phase thermal control systems such as that on the proposed Space Station. An aluminum plate is machined with fine, rectangular grooves (39 grooves/cm). This grooved surface is then enhanced by an inexpensive process called Ivadizing™ (equipment for this process is patented by McDonnell Douglas). During Ivadizing, aluminum is vapor deposited onto the surface, forming a slightly porous coating on the land area between the grooves. The resulting surface has a much larger evaporative heat transfer coefficient and capillary pumping ability than that with plain, rectangular grooves. We have used Ivadizing to enhance a mounting plate evaporative surface. Tests of this plate with R-11 showed improvement in evaporative heat transfer coefficient by a factor of 4.