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 10 of 10 for “"refrigerant charge"”.
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Refrigerant charge reduction in small commercial refrigeration systems
This paper presents analysis of location of refrigerant inventory and numerical results of charge reduction in a typical bottle cooler. The original unit was first characterized by determining its capacity, the coefficient of performance (COP), pull-down characteristics, and total charge using …
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Fault Detection And Diagnosis For Air Conditioners And Heat Pumps Based On Virtual Sensors
… difficult to measure directly.</p> <p>A virtual refrigerant charge sensor (VRC) was extended with three approaches for determining refrigerant charge for equipment having variable-speed compressors and fans. Three different virtual refrigerant mass flow (VRMF) sensors were evaluated for …
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Intermediate vapor bypass: A novel design for mobile heat pump at low ambient temperature
… exponential growth, and drive range on a single charge is one of the most highly valued specs. Passenger thermal comfort, especially heating in cold weather, is usually the largest auxiliary onboard energy user, and can significantly reduce the EV drive range. Heat pumps dramatically reduce the …
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Secondary loop reversible AC/HP system for electric vehicles
… direct system. The secondary loop system has a refrigerant circuit operating between two 50/50 water glycol loops, and uses the identical compressor and accumulator as the baseline DX system. For most operating conditions in this study, the secondary loop system has slightly lower maximum …
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Modelling the performance and dynamics of vapour compression refrigeration systems
… operating conditions and with alternative refrigerants. Dynamic models allow comparison of both transient and steady-state behaviour and this is of particular importance for liquid chillers, since these systems can operate under transient conditions for long periods. This thesis details the …
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Experimental study of reversible AC/HP system for electric vehicles
… 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 different indoor temperature at …
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Transient distribution of refrigerant and oil in a residential heat pump water heater system
… system due to the mutual solubility between the refrigerant and oil. The presence of circulating oil would affect the characteristics of heat transfer, pressure drop and mass retention in system. In addition, a large amount of retention of oil outside of the compressor might cause insufficient …
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The void fraction in headers of microchannel heat exchangers
… of compactness, the potential for reduction of charge, and improvement of heat transfer performance compared to other traditional heat exchangers. The void fraction in the headers affects the thermal performance, refrigerant charge, and total pressure drop of MCHEs. However, due to the complex …
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Experimentally validated models of refrigerant distribution in microchannel heat exchangers used to evaluate charge reduction of various working fluids
… of microchannel heat exchanger performance and charge. Effects of using various correlations are presented and discussed with focus on microchannel condensers and evaporators. Experiments with different refrigerants including R290, R717, R1234yf, and R134a are used to validate the models. The …
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Instability of flow boiling in parallel microchannels
… such as high heat transfer rate and reduced refrigerant charge, encounters important problems related to flow maldistribution and instabilities in parallel-channels flow. The thermal and hydrodynamic performance of a microchannel evaporator can drastically decrease, due to the presence of …