scholarly journals Matching Testing Possibilities and Needed Experiments for Successful Vapor Compression Cycles in Microgravity

2020 ◽  
Vol 324 ◽  
pp. 02001
Author(s):  
Leon P. M. Brendel ◽  
James E. Braun ◽  
Eckhard A. Groll
Keyword(s):  
Space Travel ◽  
Vapor Compression ◽  
Testing Methods ◽  
Two Phase ◽  
Open Questions ◽  
Long Duration ◽  
Manned Space ◽  
Vapor Compression Cooling

The literature shows five decades of interest in vapor compression cooling for spacecraft, while only very few conclusions can be drawn because of either non-systematic approaches or sparsely documented experiments. In contrast, the demand for high COP refrigerators and freezers has increased with the emerging plans of long duration manned space travel. Research is needed exploiting all available testing approaches to investigate two-phase cycles in microgravity environments. This paper presents relevant testing possibilities with their characteristics and outlines open questions regarding vapor compression cycles in space. Beneficial experiments are derived from open questions and matched with available testing methods to prescribe a path towards reliable and efficient refrigeration systems in microgravity.

scholarly journals Design of an Autonomous and Timed Water Delivery System in Microgravity

2020 ◽  
Vol 1 (1) ◽  
Author(s):  
William Elke ◽  
Maia Heineck ◽  
Jonah Meffert ◽  
Ellie Monaghan ◽  
Jason Palesse
Keyword(s):  
Space Exploration ◽  
Space Station ◽  
Microgravity Environment ◽  
Space Travel ◽  
Water Delivery ◽  
International Space ◽  
Schedule Flexibility ◽  
Long Duration ◽  
Manned Space ◽  
Fully Functioning

For long-duration, manned, space exploration missions to be feasible, farming techniques in space must become reliable and fruitful. The NASA Project Veggie team currently runs experiments on the International Space Station (ISS) in order to better understand how plants react to a microgravity environment. Current watering strategies on the ISS involve manual watering of all plants by the crewmembers. This poses a problem because watering plants must be scheduled into the crewmembers’ days which means less time to work, etc. The objective of Team International Space Salads (ISSa) was to create a device and prove that it could function in microgravity without electricity to autonomously water the plants in order to allow for schedule flexibility of the ISS crewmembers and to lay the foundation for watering systems for deep-space travel. The final device did not function fully as planned, however, the plant growing, surface tension experiments, and the device collectively progressed the multi-year project to a state where successive teams would have the knowledge and tools necessary to create a fully functioning device.

Modeling of Vapor Compression Cycles for Multivariable Feedback Control of HVAC Systems

1997 ◽  
Vol 119 (2) ◽  
pp. 183-191 ◽  
Author(s):  
Xiang-Dong He ◽  
Sheng Liu ◽  
Haruhiko H. Asada
Keyword(s):  
Feedback Control ◽  
Phase Interface ◽  
Heat Pumps ◽  
Lumped Parameter Model ◽  
Vapor Compression ◽  
Two Phase ◽  
Lumped Parameter ◽  
Fan Speed ◽  
Linearized Model ◽  
Multivariable Feedback

This paper presents a new lumped-parameter model for describing the dynamics of vapor compression cycles. In particular, the dynamics associated with the two heat exchangers, i.e., the evaporator and the condenser, are modeled based on a moving-interface approach by which the position of the two-phase/single-phase interface inside the one-dimensional heat exchanger can be properly predicted. This interface information has never been included in previous lumped-parameter models developed for control design purpose, although it is essential in predicting the refrigerant superheat or subcool value. This model relates critical performance outputs, such as evaporating pressure, condensing pressure, and the refrigerant superheat, to actuating inputs including compressor speed, fan speed, and expansion valve opening. The dominating dynamic characteristics of the cycle around an operating point is studied based on the linearized model. From the resultant transfer function matrix, an interaction measure based on the Relative Gain Array reveals strong cross-couplings between various input-output pairs, and therefore indicates the inadequacy of independent SISO control techniques. In view of regulating multiple performance outputs in modern heat pumps and air-conditioning systems, this model is highly useful for design of multivariable feedback control.

Optimized Refrigerant Flow Rate and Dimensions of the Ejector Employed in a Modified Ejector Vapor Compression System

2020 ◽  
Vol 28 (04) ◽  
pp. 2050038
Author(s):  
Dishant Sharma ◽  
Gulshan Sachdeva ◽  
Dinesh Kumar Saini
Keyword(s):  
Flow Rate ◽  
Cooling System ◽  
Cooling Capacity ◽  
Coefficient Of Performance ◽  
Vapor Compression ◽  
Evaporator Temperature ◽  
Proposed Model ◽  
Condenser Temperature ◽  
Vapor Compression System ◽  
Vapor Compression Cooling

This paper presents the analysis of a modified vapor compression cooling system which uses an ejector as an expansion device. Expanding refrigerant in an ejector enhances the refrigeration effect and reduces compressor work. Therefore, it yields a better coefficient of performance. Thermodynamic analysis of a constant area ejector model has been done to obtain primary dimensions of the ejector for given condenser and evaporator temperature and cooling capacity. The proposed model has been used to design the ejector for three refrigerants; R134a, R152a and R1234yf. The refrigerant flow rate and the diameters at various sections of the ejector have been obtained by doing numerical modeling in Engineering Equation Solver (EES). Refrigerant R1234yf demanded the highest diameter requirements at a fixed 5∘C evaporator temperature and 40∘C condenser temperature for a given range of cooling load. Both primary and secondary refrigerants flow rates are higher for R1234yf followed by R134a and then R152a.

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