Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 26 for “"expansion valve"”.
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A study on the characteristics of the flow inside a thermostatic expansion valve
Thermostatic expansion valves (TEV) and electronic expansion valves (EEV) are expansion devices commonly used in air-conditioning system which involves the spray and atomization process of the refrigerant. Most previous studies focused on the macro-features of the expansion valve, such as the …
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Developing two-phase flow after an expansion valve and the effect of flow patterns on two-phase flow distribution
Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2024-08-01
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Evaluation and visualization of refrigerant two-phase flow in distributor
… flow distribution exiting thermostatic expansion valve and through distributor. It is well known that when two-phase flow goes through separation devices such as distributors and headers, mal-distribution is unavoidable due to different properties of liquid and vapor. However, it is …
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Analytical and experimental investigation of two-phase ejector cycles using low-pressure refrigerants
… cycle performance improvement when compared to expansion valve cycles. R134a and R1234yf were used as the working fluids in the experimental tests. These lowpressure working fluids offer less improvement potential with ejector cycles because of their lower throttling loss, compared to CO2. It …
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Superheat control for air conditioning and refrigeration systems: Simulation and experiments
… system design. The emergence of the electronic expansion valve and variable speed drives has made immense impacts on the ability to regulate system parameters, resulting in important strides towards efficiency improvement. This research presents tools and methodologies for model development and …
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Experimental and Analytical Investigation of a Two-Phase Ejector Used for Expansion Work Recovery in a Transcritical R744 Air-Conditioning System
… throttling losses make R744 a suitable fluid for expansion work recovery. This study presents experimental and computational results obtained from a transcritical R744 air-conditioning system using a two-phase ejector specifically designed and built for this investigation. The results are compared …
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Distribution of refrigerant and lubricant in automotive air conditioning systems
… of an automotive A/C system. Quick Closing Valve Technique (QCVT) combined with Remove and Weigh Technique is employed to measure the refrigerant mass, with an overall uncertainty within 2%. Three different techniques-Remove and Weigh, Mix and Sample and Flushing- are used to determine the …
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Testing and modeling of a two-phase ejector
The ejector expansion refrigeration cycle is a modified vapor compression cycle in which a two phase ejector is used to recover a portion of the work otherwise lost in the expansion valve. The ejector improves cycle performance by increasing compressor inlet pressure and by lowering the quality of …
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An investigation of the effect of entrained oil on the heat transfer rate of a refrigerant evaporator
… on the heat transfer characteristics of a direct expansion evaporator coil. A modified refrigeration system, in which the oil content of the refrigerant could be varied, was used in conjunction with an air conditioning system, which supplied the evaporator load. The heat transferred to the …
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Quantification and analysis methods aimed at the reduction of flow induced noise in the expansion device
Embargo set by: Colleen Fallaw for item 102686 Lift date: 2019-08-10T21:25:30Z Reason: Author requested closed access (OA after 2yrs) in Vireo ETD system
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Modelling the performance and dynamics of vapour compression refrigeration systems
… models of the reciprocating compressor, expansion valve, evaporator and condenser are presented. The models are integrated to form the overall system model by passing conditions from one component to another. A series of steady-state and transient experimental tests were carried out on a …
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Control of flash gas bypass mac system with emphasis on start-ups and transients
… state and demonstrated that compared to direct expansion mode (DX), FGB mode have better performance. However, the control strategy of FGB system and dynamic behavior during start-ups and transients were not yet clearly defined and investigated. In this paper, a novel control strategy has been …
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Experimental study of reversible AC/HP system for electric vehicles
… to different system parameters including expansion valve opening size, refrigerant charge amount, compressor speed, indoor air mass flow rate, outdoor air face velocity, and ambient and indoor temperatures. The transient behavior can be simulated by using steady state test results for …
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Evaluating energy dissipation during expansion in a refrigeration cycle using flue pipe acoustic resonators
… the recently invented thermo acoustic expansion valve (TEV). It is found that the efficiency of the TEV is less than the theoretical results deduced from the numerical model. At an efficiency of approximately 10%, the technology represents a gain in cooling power, but further …
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Experimental and numerical investigation of the design and control of vapor-compression systems with integration of two-phase ejectors for performance enhancement through expansion work recovery
… refrigeration cycles by means of expansion work recovery has received significant attention in the past decade. Research has focused primarily on the design and performance of the ejector and the effect the ejector has on cycle performance. However, recent research has shown that …
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Vortex control of two-phase refrigerant flow in nozzles and its application in ejector vapor compression cycles
… of the other motive flow control methods (series expansion valve control and needle control). It was found that the total work recovery efficiency of ejector with vortex control can be better than series expansion valve control and is close to needle control. The decrease of suction nozzle length …
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TRANSIENT MODELING OF TWO-STAGE AND VARIABLE REFRIGERANT FLOW VAPOR COMPRESSION SYSTEMS WITH FROSTING AND DEFROSTING
… in the opening of the upper-stage electronic expansion valve is also investigated. Comparison between the predictions and experimental data shows that the simulation can adequately capture the transient heat transfer and fluid flow phenomena of the system and thus demonstrating the fidelity of …
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Potential of controlling subcooling in residential air conditioning system
… a control strategy using EXV (electronic expansion valve) with ∆Tin as input signal for controlling subcooling (adjusting the EXV opening) is proposed to provide COP or cooling capacity Q maximizing subcooling for the RAC system as conditions change.
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Flow visualization of cavitation
… of an evaporator, compressor, condenser, and an expansion valve. There are many possible refrigerants that can be used, but the physical properties of water make it ineffective in the traditional refrigeration loop. But if water could be used it would have many advantages as it is abundant, …
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Fault Detection And Diagnosis For Air Conditioners And Heat Pumps Based On Virtual Sensors
… is relatively independent of compressor and expansion valve faults that influence mass flow rate. The third model was developed using an empirical correlation for thermal expansion valves (TXV) and electronic expansion valves (EEV) based on an orifice equation.</p> <p>To assess the impact of …
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