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A novel type of two-phase loop is introduced which can work in any of mechanical, capillary, or mechanical/capillary hybrid modes and would allow us to make various experiments in parallel. A key component of that loop is a three-port (liquid in, liquid out, and vapor out) capillary pump evaporator coupled with mechanical pumps. An illustration of the proposed hybrid pump loop is given with a brief description of such critical components as the above. A mathematically formulated computational analysis procedure is then presented for the preliminary design of that loop. The procedure consists of a series of theoretically derived algebraic expressions; upon which all the related components are suitably sized in diameter, thickness, length, or volume. Obtained numerical results of a parametric design study are graphically shown in the figures as a function of the baseplate temperature or the heat load.

Thermal/hydraulic analyses are made for optimal design and in-orbit operations of a fluid-looped two-radiator system, which could be used for tighter temperature control of a thermoelectrically-cooled mission equipment. Analysis results are mathematically rearranged to construct a plain algorithm suited to design calculations. Computations upon that algorithm provide us with several groups of curves applicable to preliminary design of fluid loops with serially-connected radiators. All such curves are actually used in reasonably determining design specifications of an ammonia/propylene-based cooling loop of our concern. A simplified solution method is then introduced for off-design operations problems to readily find the resulting heat rejection, the required pumping power, the required pump speed, the resulting temperature drop, the resulting cold plate temperature, and so on.

Two types of evaporators, specially developed for pumped two-phase fluid loop use, are illustratively described with drawings from which inner structures can clearly be seen. A significant difference between the two is such that evaporator exit vapors are usually wet in the first while always dry in the second. An outline of microgravity experiments, practiced for functional verifications of the two, is given along with observed inside views and measured temperatures. As a result of the experiments, necessity of suitable control in liquid supply is emphasized from an angle of normal operations. The void fraction, the temperature difference, and the pressure difference are proposed as an input signal for the flow rate control. The whole of microgravity experiments held again is explained with drawings of evaporator test loops, permitting any kind of control based on the above three, and also with figures displaying the temperature/pressure variations.

Computational procedures are clearly shown in the tables in such a staged way as one may easily proceed design calculations of cold plates, space radiators, and single-phase fluid loop systems. All the procedures are incorporated into a design code which can deal with two types of cold plates, five types of space radiators, and five configurations of a fluid loop mechanically driven by either rotodynamic or volumetric displacement one. Equivalent hydraulic diameters, heat transfer area densities, dry weights, and pressure losses are calculated over a wide range of parameters to give demonstrative examples of design practices. For cold plate design optimization, the weight and the pressure loss are displayed in the figures as functions of baseplate area, width to length ratio, or diameter to diameter/height ratio.

A feasibility analysis on mechanically compressed vapor cycle systems is practiced in accordance with the laws of thermodynamics. The feasibility is mathematically expressed in three different factors: the expansion valve exit quality, the compressor effeciency, and the cooling efficiency. Numerical results are plotted in the figures to form illustrative feasibility diagrams; from which found are permissible combinations of the evaporation/condensation temperatures, the required compression ratio, and the required compressor efficiency. An evaporation temperature control method, coupled with the thermohydraulic analysis procedure, is then introduced for a space-borne heat pump system operating under off-design conditions. Control variables used in that method are the compression ratio and the compressor speed, requested values of which are graphically shown in the figures with parameters of interest.

A combined two-stage Stirling and Joule-Thomson cycle refrigerator has been developed for advanced celestial observation missions. The specified cooling capacity is 40 mW at the final 4 K stage and 200 mW at the second 20 K stage. The precooler compressor power amounts to about 100 W, most of which is thermally dissipated. This study has therefore been made to propose a most suitable method of the waste heat rejection. Proposed are a loop heat pipe (LHP) and a mechanical pump loop (MPL). Computational sizing procedures of the two are presented with mass estimate models. Also presented is an empirically obtained relation between the cooling efficiency and the ambient temperature. This algebraic expression is then used to find the required electrical power for the 20 K stage cooling. Numerical results of the LHP/MPL design calculations are displayed in the figures as a function of the ambient temperature ranging from 150 K to 310 K.

To contribute stable operations of a mechanically pumped two-phase fluid loop, evaporative cold plates, developed in NASDA/Toshiba, were hydraulically tested in a coupled row before system integration. A significant result of such pretests was that the two-row arrangement is so highly interfering as to make difficult the exit vapor quality control. A flow control means other than used before has thus become necessary to suppress plate-to-plate operational interferences. Proposed is the multi-variable cascade control method, upon which flow rates are fittingly modulated so that the cold plate exit void fractions would constantly be kept as specified. The system identification, indispensable to practical use of this method, was experimentally parametrically done to provide us with a mathematical model of the coupled cold plates. The model is expressed in matrix representation readily applicable to state predictions.