Performance Analysis of a Transcritical CO2 Heat Pump Water Heater Incorporating a Brazed-Plate Gas-Cooler PDF Download
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ISBN:
Category :
Languages : en
Pages : 384
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Book Description
This study focuses on the experimental testing and numerical modeling of a 4.5 kW transcritical CO2 heat pump water heater at Queen's University in the Solar Calorimetry Laboratory. Due to the predicted high heat rejection temperatures in a transcritical vapour-compression cycle, buoyancy driven thermosyphon flow through a brazed-plate gas-cooler was proposed to promote tank stratification and to improve system performance. The performance was evaluated through a series of experimental sensitivity and static tank charge tests. A TRNSYS model was also created and verified to simulate the performance of the system under a detailed user demand schedule for a week of operation. The TRNSYS model used a parametric table created with a steady-state model of the vapour-compression system in EES that was validated against experimental data to a standard error of the Y-estimate of ±0.073 kW for heating capacity, ±1.01°C for gas-cooler exit temperature, and ±0.086 for COP. A series of tank charge tests were conducted under thermosyphon flow and forced flow rates at 1 L/min, 2 L/min, and 4 L/min. The thermosyphon charge test produced the highest level of stratification and a total COP of 3 at an average flow rate of 0.73 L/min. All of the forced convection cases operated with a higher degree of mixing. TRNSYS model simulations with hot water draws found that the thermosyphon flow configuration performed with a higher degree of stratification under regular user demand while simulations with high flow rates resulted in a mixed tank at a high temperature. Results predicted an 11% reduction in required heat energy input to the storage, a 30% reduction in electrical energy consumption, a 35% reduction in heat loss, and a 29% improvement in COP for the thermosyphon test as compared to the operation with a mixed tank at 4 L/min. The thermosyphon draw test also performed with the lowest average tank temperature, yet produced the highest draw temperatures. Through these results, it was concluded that natural convection operation with brazed-plate gas-coolers can contribute to a better performing system and this flow configuration should be considered in future applications of this technology.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 384
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Book Description
This study focuses on the experimental testing and numerical modeling of a 4.5 kW transcritical CO2 heat pump water heater at Queen's University in the Solar Calorimetry Laboratory. Due to the predicted high heat rejection temperatures in a transcritical vapour-compression cycle, buoyancy driven thermosyphon flow through a brazed-plate gas-cooler was proposed to promote tank stratification and to improve system performance. The performance was evaluated through a series of experimental sensitivity and static tank charge tests. A TRNSYS model was also created and verified to simulate the performance of the system under a detailed user demand schedule for a week of operation. The TRNSYS model used a parametric table created with a steady-state model of the vapour-compression system in EES that was validated against experimental data to a standard error of the Y-estimate of ±0.073 kW for heating capacity, ±1.01°C for gas-cooler exit temperature, and ±0.086 for COP. A series of tank charge tests were conducted under thermosyphon flow and forced flow rates at 1 L/min, 2 L/min, and 4 L/min. The thermosyphon charge test produced the highest level of stratification and a total COP of 3 at an average flow rate of 0.73 L/min. All of the forced convection cases operated with a higher degree of mixing. TRNSYS model simulations with hot water draws found that the thermosyphon flow configuration performed with a higher degree of stratification under regular user demand while simulations with high flow rates resulted in a mixed tank at a high temperature. Results predicted an 11% reduction in required heat energy input to the storage, a 30% reduction in electrical energy consumption, a 35% reduction in heat loss, and a 29% improvement in COP for the thermosyphon test as compared to the operation with a mixed tank at 4 L/min. The thermosyphon draw test also performed with the lowest average tank temperature, yet produced the highest draw temperatures. Through these results, it was concluded that natural convection operation with brazed-plate gas-coolers can contribute to a better performing system and this flow configuration should be considered in future applications of this technology.
Author: Paul Maina
Publisher:
ISBN:
Category : Dissertations, Academic
Languages : en
Pages : 530
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Book Description
Discusses the main objective of the study is to carry out a theoretical and experimental study of a water-to-water CO2 heat pump system and improve its performance by optimizing its working parameters and conditions. The optimization process will be based on South African conditions.Specific objectives to meet the required goal are: 1. Carry out the installation and experimental analysis of a water to water CO2 heat pump system.2. Evaluate the reliability of the system using statistical means through regression analysis and create relationship models between the input and output parameters of the system.3. Execute a thermodynamic analysis of the selected system and evaluate the most important factors that affect its energy efficiency, then identify and evaluate possible system improvements and optimum operating conditions. 4. Compare available heat pump related kinematic and mathematical models and evaluate the best model to describe the operations in the system under local operating conditions. Suggest further improvements to the models and evaluate these too.5. Perform computer modelling and simulations to analyse the CO2 heat pump system,supplement the measurements from the test rig and compare the results.
Author: Douglas Kosar
Publisher:
ISBN:
Category : Energy conservation
Languages : en
Pages : 344
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Author: Obinna Uyanna
Publisher:
ISBN:
Category :
Languages : en
Pages : 160
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Book Description
The current overdependence on fossil fuel as the means of energy generation ensures that eventually, energy and utility costs will be extremely high since these fossil materials are depletive in nature. However, the research and development of energy efficient devices offers a viable solution to this situation. One such device is the heat pump water heater (HPWH), a device that utilizes a reverse refrigeration cycle to generate domestic hot water (DHW) for residential use. The performance of HPWHs in hot-humid climates was analyzed since such areas have high solar energy concentration, especially in the summer. Although electric resistance water heaters (ER WHs) are currently the main source of DHW generation, HPWHs are believed to be the more efficient water heating option. In this work, BEopt, which is a building energy-optimization software, was used to perform simulations of HPWHs and ERWHs in two selected hot-humid climates. With certain user-defined inputs, four simulation cases were generated and tests were run that showed the performance of these water heaters. The results showed that HPWHs were immensely more efficient, having efficiencies of 3.3 and 3.56 in the two test location while ERWHs had efficiencies of 0.88 and 0.9. The results also showed a significant amount of utility savings, reduced consumed energy as well as reduced CO, emissions when compared to ERWHs. It was also shown in the results that the units with HPWHs had significantly higher cooling energy values when compared to units with ERWHs thus leading to a better space cooling and comfort level for occupants of homes on hot-humid climates.
Author: Young Park
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Adoption of heat pump water heating technology for commercial hot water could save up to 0.4 quads of energy and 5 million metric tons of CO2 production annually in North America, but industry perception is that this technology does not offer adequate performance or reliability and comes at too high of a cost. Development and demonstration of a CO2 heat pump water heater is proposed to reduce these barriers to adoption. Three major themes are addressed: market analysis to understand barriers to adoption, use of advanced reliability models to design optimum qualification test plans, and field testing of two phases of water heater prototypes. Market experts claim that beyond good performance, market adoption requires 'drop and forget' system reliability and a six month payback of first costs. Performance, reliability and cost targets are determined and reliability models are developed to evaluate the minimum testing required to meet reliability targets. Three phase 1 prototypes are designed and installed in the field. Based on results from these trials a product specification is developed and a second phase of five field trial units are built and installed. These eight units accumulate 11 unit-years of service including 15,650 hours and 25,242 cycles of compressor operation. Performance targets can be met. An availability of 60% is achieved and the capability to achieve>90% is demonstrated, but overall reliability is below target, with an average of 3.6 failures/unit-year on the phase 2 demonstration. Most reliability issues are shown to be common to new HVAC products, giving high confidence in mature product reliability, but the need for further work to minimize leaks and ensure reliability of the electronic expansion valve is clear. First cost is projected to be above target, leading to an expectation of 8-24 month payback when substituted for an electric water heater. Despite not meeting all targets, arguments are made that an industry leader could sufficiently develop this technology to impact the water heater market in the near term.
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ISBN:
Category :
Languages : en
Pages : 0
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Author: Bethany Sparn
Publisher:
ISBN:
Category : Heat pumps
Languages : en
Pages : 70
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Book Description
This report discusses how domestic hot water heating can be a significant opportunity for energy savings. An emerging technology has recently arrived in the U.S. market: the residential integrated heat pump water heater (HPWH). A laboratory evaluation is presented of the five integrated HPWHs available in the U.S. today.
Author: Nicholas Edward Peter Fernandez
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ISBN:
Category :
Languages : en
Pages :
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Author:
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ISBN:
Category :
Languages : en
Pages :
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The project investigated the development and improvement process of a R744 (CO2) commercial heat pump water heater (HPWH) package of approximately 35 kW. The improvement process covered all main components of the system. More specific the heat exchangers (Internal heat exchanger, Evaporator, Gas cooler) as well as the expansion device and the compressor were investigated. In addition, a comparison to a commercially available baseline R134a unit of the same capacity and footprint was made in order to compare performance as well as package size reduction potential.
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Category :
Languages : en
Pages :
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Over recent years, heat pump water heaters (HPWHs) have become more readily available and more widely adopted in the marketplace. For a 6-month period, the Building America team Consortium for Advanced Residential Buildings monitored the performance of a GE Geospring HPWH in Windermere, Florida. The study found that the HPWH performed 144% more efficiently than a traditional electric resistance water heater, saving approximately 64% on water heating annually. The monitoring showed that the domestic hot water draw was a primary factor affecting the system's operating efficiency.
