Submitted by Rafael Santana (rafael.silvasantana@ufpe.br) on 2017-07-12T17:40:35Z No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Tese_Gutenberg da Silva Pereira_1.pdf: 6410667 bytes, checksum: ddf1e84a9a1b8bcce71836f13e8707fa (MD5) / Made available in DSpace on 2017-07-12T17:40:35Z (GMT). No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Tese_Gutenberg da Silva Pereira_1.pdf: 6410667 bytes, checksum: ddf1e84a9a1b8bcce71836f13e8707fa (MD5) Previous issue date: 2016-02-22 / Com a atual escassez de energia, alta demanda e aumento do custo da energia elétrica, verifica-se que uma questão importante é a melhoria da eficiência dos sistemas de climatização dentro de um padrão de eficiência certificado possibilita-se, assim, para uma comparação real de qual é a melhor opção de layout e operação dos sistemas, já que os sistemas de climatização são responsáveis por uma alta parcela do consumo energético. O presente trabalho se propõe a comparar dois sistemas de refrigeração diferentes, usando chiller de compressão de vapor, para a climatização de ambientes. Foram propostas diferentes modalidades para a comparação em operações isoladas e ações combinadas. Essas operações são avaliadas nos conceitos de edifícios verdes. Foi desenvolvido um modelo matemático baseado nos princípios de conservação de massa e energia, complementado por várias funções, de modo a determinar as propriedades termofísicas e eficiências dos compressores. O modelo avalia a influência dos parâmetros operacionais principais do sistema de refrigeração a água gelada operando em três configurações diferentes. As equações do modelo foram resolvidas pelo programa EES (Engineering Equation Solver). Os resultados mostraram que o sistema com compressão diferenciada apresenta COP igual ao do sistema com chiller parafuso na faixa de 0 a 300 TRs, e um COP superior em média de 9% na faixa de 400 a 800 TRs. / With the current energy shortages, high demand and rising cost of electricity, it turns out that an important issue is the improvement of the air conditioning efficiency within a standard of efficiency certificate for a real comparison of what is the better layout option and operation of systems, as the HVAC systems account for a high share of energy consumption. This study aims to compare two different cooling systems using vapor compression chiller for air conditioning environments. They were different proposals modalities for comparison in isolated and combined action operations. These transactions are valued on the concepts of green buildings. A mathematical model was developed based on the principles of conservation of mass and energy, supplemented with various functions in order to determine the thermophysical properties and efficiencies of the compressors. The model evaluates the influence of the main operating parameters of the cold water cooling system operating in three different configurations. The model equations were solved by EES program (Engineering Equation Solver). The results showed that the system presents differentiated compression COP equal to the screw chiller systems in the range from 0 to 300 RTs and a higher COP (average of 9%) in the range of 400 to 800 TR.

<p>  </p> <p>Environmental challenges, increasing energy costs and demand, and upcoming regulations (e.g., new equipment performance ratings, phase-down of HFCs) are a few of the main drivers behind the research on advanced HVAC&R equipment. The HVAC&R systems are one of the largest energy consumers in both commercial and residential buildings and their operation is essential to ensure thermal comfort as well as other industrial needs. Within this context, large chillers provide chilled water to condition commercial buildings and the new generation of smart chillers feature variable speed compressors that enable active capacity modulation. In turn, variable speed operation along with other factors can contribute to performance degradation. Understanding mechanisms of degradation and developing models that enable predicting the decrease in performance with respect to the rated values are still open topics in the literature. </p> <p>The overarching goal of this research is to investigate the performance degradation of a water-cooled variable-speed screw chiller under long term operation and to gain insights on the behavior of the chiller under accelerated life testing. In particular, this thesis covers the initial task of designing an experimental test setup that enables performance testing according to the AHRI 550/590 standard. Once the experimental setup was commissioned, a set of four standard-conform baseline tests was conducted to map the rated performance of the chiller at both full and part-load conditions. After completing the baseline tests, an accelerated life test cycle procedure was developed and implemented in order to conduct 24/7 automated testing on the chiller. To this end, two test modes were established to simulate a real-life use of the chiller and induce high level of thermo-mechanical stresses on the compressor. Furthermore, eight recurring baseline tests were conducted to determine the performance behavior after 1000 operating hours. Finally, a preliminary system model was set up. This thesis describes the design of the system, the commissioning and control and provides insights on the performance testing as well as long-term testing methodology and the modeling work that was done so far. </p>