Enhanced Finned-Tube Condenser Design and Optimization Susan W. Stewart 173 pages Directed by Dr. Sam V. Shelton Finned-tube heat exchangers are widely used in space conditioning systems, as well as any other application requiring heat exchange between liquids and gases. Their most widespread use is in residential air conditioning systems. Residential systems dictate peak demand on the U.S. national grid, which occurs on the hot summer afternoons, and thereby sets the expensive infrastructure requirement of the nations power plant and electrical distribution system. In addition to peak demand, residential air conditioners are major energy users that dominate residential electrical costs and environmental impact. The only significant opportunity for electrical power use reduction of residential air conditioners is in technology improvement of the finned-tube heat exchangers, i.e., condenser and evaporator coils. With the oncoming redesign of these systems in the next five years to comply with the regulatory elimination of R-22 used in residential air conditioners today, improvement in the design technology of these systems is timely. An air conditioner condenser finned-tube coil design optimization methodology is derived and shown to lead to improved residential air conditioner efficiency at fixed equipment cost. This nonlinear optimization of the 14 required design parameters is impractical by systematic experimental testing and iteration of tens of thousands condenser coils in an air conditioning system. The developed methodology and results can be used in the redesign of residential systems for the new mandated environmentally friendly refrigerants and to meet increasing regulatory minimum system efficiencies. Additionally, plain fins and augmented fins, (louvered), are compared using the developed model and optimization scheme to show the effect of the augmentation on system performance. Furthermore, an isolated condenser model was developed using condenser entropy generation minimization as the figure of merit to minimize the model complexity and computation time. Isolated model optimizations are compared with the system model optimum designs.

Buildings are the primary user of energy in the USA. Within homes, the heating, ventilation, and air condition (HVAC) system is the largest energy consumer. This study: (i) developed a new methodology for simulating filter loading in-situ; (ii) observed the impact of filter loading on AC performance in-situ; and (iii) provided a greater understanding of when a filter is “dirty” and should be replaced. Six central AC systems in the Atlanta metro-region were evaluated. Filter loading was simulated by installing the TrueFlow® airflow metering device and partially taping off the face at 3 different increments. This resulted in measurements at 5 discrete static pressures (no filter, TrueFlow, TrueFlow Taped one, TrueFlow Taped two, and TrueFlow Taped three). The pilot study found that as filter pressure drop increased, airflow rates generally decreased, resulting in higher differences in temperature across the evaporator coil (∆T). There was no observed correlation between absolute humidity across the evaporator coil and either filter pressure drop or system airflow. Overall, as airflow decreased so did sensible, latent, and total capacity. This research can inform decisions about filter replacement and be used to evaluate computer simulation models of HVAC performance.

The thesis explores the technical feasibility of an alternative method of decoupling air-conditioning systems function within the context of ecological issues. The system is a variant of dedicated outdoor air systems to separate dehumidification and cooling in air conditioning equipment. The project specifically investigates locating these components within the building envelope. Placement in the envelope moves the systems closer to fresh air and offers architectural expression for components that are normally out of sight. Designers, engineers, building science, mechanical, structural, biologist, and architectural engineers ideally as agents offer beneficial improvement to the system. The reduction in size of components into the building envelope offers risk. The thesis design space uses historical works, biological analogues, and past work to ground the technical understanding of the topic. Specific use of biological inspired design realizes translation from other systems to improve the alternative decoupled air conditioning system. The thesis develops prototype models for lighting analysis and for sensible and latent heat calculations. Psychrometric charts serve as tools to understand the thermodynamic air-conditioning process in conventional direct expansion vapor compression and solar liquid desiccant air conditioning systems. Data, models, and sketches provide tools for improvements to the 'thick' building envelope. Finally, the diagrams translate into functional decompositions for modifications to improve the system. The thesis probes the constraints in the areas of cost, fabrication, and technology that may not yet exist for selective improvement rather than a barrier to development of the thesis.

This thesis details a study of strategies used to limit the flow generated noise encountered in the outlet diffusers of high velocity heating, ventilation and air conditioning (HVAC) duct systems. The underlying noise rating criterion is drawn from the specifications covering ocean going aluminium fast ferries. Although directed primarily towards the fast ferry industry the results presented herein are applicable to other niche high velocity HVAC applications. Experimental tests have been conducted to prove the viability of a high velocity HVAC duct system in meeting airflow requirements whilst maintaining acceptable passenger cabin noise levels. A 50 mm diameter circular jet of air was expanded using a primary conical diffuser with a variety of secondary outlet configurations. Noise measurements were taken across a velocity range of 15 to 60 m/s. An optimum outlet design has been experimentally identified by varying the diffuser angle, outlet duct length and the termination grill. A 4 to 5 fold reduction in required duct area was achieved with the use of a distribution velocity of 20 to 30 ms-1, without exceeding the prescribed passenger cabin noise criteria. The geometric configuration of the diffuser outlet assembly was found to have a pronounced effect on the noise spectrum radiating from the duct outlet. The development of a numerical model capable of predicting the flow induced noise generated by airflow exiting a ventilation duct is also documented. The model employs a Large Eddy Simulation (LES) CFD model to calculate the turbulent flow field through the duct diffuser section and outlet. The flow-generated noise is then calculated using a far field acoustic postprocessor based on the Ffowcs-Williams and Hawkings integral based formulation of Lighthill???s acoustic analogy. Time varying flow field variables are used to calculate the fluctuating noise sources located at the duct outlet and the resulting far field sound pressure levels. This result is then used to calculate the corresponding far field sound intensity and sound power levels. The numerical acoustic model has been verified and validated against the measured experimental results for multiple outlet diffuser configurations.

My diploma thesis focuses on design of air-conditioning system for chicken breeding spaces. In the background are considered general issues of air-conditioning, hatchery layout and microclimate for eggs incubation and chicken breeding. The research part is divided into two parts – Calculations and Design. The Calculations address the amount of incoming fresh air, heat loss, heat load and psychrometric calculations for summer and winter periods. The Design focuses on defining suitable diffusers and air-ducts, optimal air-conditioning unit with fans corresponding to hatchery requirements and pressure loss in ducts. The technical drawings and a list of used material are included.

Thesis (M.B.A.)--University of Hong Kong, 1993.

This thesis considers the development of a Hammerstein-bilinear approach to non-linear systems modelling, analysis and control systems design, which builds on and extends the applicability of an existing bilinear approach. The underlying idea of the Hammerstein-bilinear approach is to use the Hammerstein-bilinear system models to capture various physical phenomena of interest and subsequently use these for model based control system designs with the premise being that of achieving enhanced control performance. The advantage of the Hammerstein-bilinear approach is that the well-structured system models allow techniques that have been originally developed for linear systems to be extended and applied, while retaining moderate complexity of the corresponding system identification schemes and nonlinear model based control designs. In recognition of the need to be able to identify the Hammerstein-bilinear models a unified suite of algorithms, being the extensions to the simplified refined instrumental variable method for parameter estimation of linear transfer function models is proposed. These algorithms are able to operate in both the continuous-time and discrete-time domains to reflect the requirements of the intended purposes of the identified models with the emphasis being placed on straightforward applicability of the developed algorithms and recognising the need to be able to operate under realistic practical system identification scenarios. Moreover, the proposed algorithms are also applicable to parameter estimation of Hammerstein and bilinear models, which are special cases of the wider Hammerstein-bilinear model class. The Hammerstein-bilinear approach has been applied to an industrial heating, ventilation and air conditioning (HVAC) system, which has also been the underlying application addressed in this thesis. A unique set of dynamic control design purpose oriented air temperature and humidity Hammerstein-bilinear models of an environmentally controlled clear room manufacturing zone has been identified. The greater insights afforded by the knowledge of the system nonlinearities then allow for enhanced control tuning of the associated commercial HVAC control system leading to an improved overall control performance.

by So Yat-fan, Yeung Ka-keung. / Thesis (M.B.A.)--Chinese University of Hong Kong, 1983. / Bibliography: leaf 107.

Em pauta já há algum tempo, os impactos ambientais, possivelmente gerados pela ação humana, são cada vez mais discutidos e estudados. A busca por um desenvolvimento sustentável e formas mais eficientes do consumo de energia é abordada frequentemente. No Brasil, os edifícios comerciais e públicos apresentam alta demanda de energia elétrica e os sistemas de condicionamento de ar são responsáveis por uma parcela relevante do consumo no país. Para mitigar esse consumo, o sistema de ar condicionado distribuído pelo piso tem sido proposto como uma solução, pois este é intrinsecamente mais eficiente que o sistema de ar condicionado convencional, com distribuição de ar pelo teto. O presente trabalho tem como propósito identificar o potencial de economia de energia de um sistema de condicionamento de ar com distribuição pelo piso em relação a um sistema com distribuição pelo teto, por meio da simulação computacional. Avaliaram-se também o impacto do aumento da temperatura de insuflação e do pé-direito da edificação, além do uso de ciclo economizador (controle entálpico) aplicado aos sistemas na economia de energia. Para a modelagem computacional, realizada pela ferramenta computacional EnergyPlus, tomou-se como referência uma sala de aula que contém um sistema de condicionamento de ar com distribuição pelo piso. O primeiro sistema modelado foi pelo piso, e este serviu como base para a modelagem do sistema pelo teto. Após a criação dos modelos foram executadas as simulações cujos resultados permitiram a comparação entre os consumos de energia de cada um dos sistemas. Em conformidade com a literatura, onde se afirmam que os sistemas com distribuição de ar pelo piso são mais eficientes que os convencionais (distribuição de ar pelo teto), este trabalho também concluiu que este sistema é mais eficiente, apresentando um indicador de economia de energia da ordem de 33%, para a condição: pé-direito de 3,50 m; temperatura de insuflação de 19 °C; e controle entálpico. Os resultados desta pesquisa indicam ainda que a utilização do controle entálpico tem maior influência na economia de energia se comparada ao aumento da temperatura de insuflação ou do pé-direito. / On the agenda for some time, the environmental impacts, possibly generated by human action, are increasingly discussed and studied. The demand for sustainable development and more efficient ways of energy consumption is often addressed. In Brazil, commercial and public buildings have high demand for electricity and air conditioning systems are responsible for a significant portion of this consumption in the country. The underfloor air conditioning system has been proposed as a solution to mitigate such consumption because it is intrinsically more efficient than the ceiling-based air conditioning system. The present work aims to identify the energy saving potential of an air conditioning system with underfloor air distribution comparatively to a system with ceiling air distribution, through computational simulation. Also, the impact of increased supply air temperature and the floor to ceiling height, and the use of the economizer cycle (enthalpy control) was evaluated. For the computational modeling, carried out by the EnergyPlus computational tool, a classroom that contains an air conditioning system with floor distribution was used as reference. The first modeled air distribution system was the underfloor air distribution system, and this served as a basis for the modeling of the ceiling air distribution system. After performing the models, the simulations were carried out, whose results allowed the comparison the energy consumptions between the two systems. According to the literature, where it is stated that the systems with underfloor air distribution are more efficient than the conventional ones (ceiling air distribution), this work also concludes that the system with underfloor air distribution is more efficient, presenting an energy saving indicator around 33%, for the following condition: floor to ceiling height of 3.50 m; supply air temperature of 19 ° C; and enthalpy control. The results of this research also indicate that the use of the enthalpy control has a greater influence on the energy savings compared to the increase of the supply air temperature or the floor to ceiling height.

Em pauta já há algum tempo, os impactos ambientais, possivelmente gerados pela ação humana, são cada vez mais discutidos e estudados. A busca por um desenvolvimento sustentável e formas mais eficientes do consumo de energia é abordada frequentemente. No Brasil, os edifícios comerciais e públicos apresentam alta demanda de energia elétrica e os sistemas de condicionamento de ar são responsáveis por uma parcela relevante do consumo no país. Para mitigar esse consumo, o sistema de ar condicionado distribuído pelo piso tem sido proposto como uma solução, pois este é intrinsecamente mais eficiente que o sistema de ar condicionado convencional, com distribuição de ar pelo teto. O presente trabalho tem como propósito identificar o potencial de economia de energia de um sistema de condicionamento de ar com distribuição pelo piso em relação a um sistema com distribuição pelo teto, por meio da simulação computacional. Avaliaram-se também o impacto do aumento da temperatura de insuflação e do pé-direito da edificação, além do uso de ciclo economizador (controle entálpico) aplicado aos sistemas na economia de energia. Para a modelagem computacional, realizada pela ferramenta computacional EnergyPlus, tomou-se como referência uma sala de aula que contém um sistema de condicionamento de ar com distribuição pelo piso. O primeiro sistema modelado foi pelo piso, e este serviu como base para a modelagem do sistema pelo teto. Após a criação dos modelos foram executadas as simulações cujos resultados permitiram a comparação entre os consumos de energia de cada um dos sistemas. Em conformidade com a literatura, onde se afirmam que os sistemas com distribuição de ar pelo piso são mais eficientes que os convencionais (distribuição de ar pelo teto), este trabalho também concluiu que este sistema é mais eficiente, apresentando um indicador de economia de energia da ordem de 33%, para a condição: pé-direito de 3,50 m; temperatura de insuflação de 19 °C; e controle entálpico. Os resultados desta pesquisa indicam ainda que a utilização do controle entálpico tem maior influência na economia de energia se comparada ao aumento da temperatura de insuflação ou do pé-direito. / On the agenda for some time, the environmental impacts, possibly generated by human action, are increasingly discussed and studied. The demand for sustainable development and more efficient ways of energy consumption is often addressed. In Brazil, commercial and public buildings have high demand for electricity and air conditioning systems are responsible for a significant portion of this consumption in the country. The underfloor air conditioning system has been proposed as a solution to mitigate such consumption because it is intrinsically more efficient than the ceiling-based air conditioning system. The present work aims to identify the energy saving potential of an air conditioning system with underfloor air distribution comparatively to a system with ceiling air distribution, through computational simulation. Also, the impact of increased supply air temperature and the floor to ceiling height, and the use of the economizer cycle (enthalpy control) was evaluated. For the computational modeling, carried out by the EnergyPlus computational tool, a classroom that contains an air conditioning system with floor distribution was used as reference. The first modeled air distribution system was the underfloor air distribution system, and this served as a basis for the modeling of the ceiling air distribution system. After performing the models, the simulations were carried out, whose results allowed the comparison the energy consumptions between the two systems. According to the literature, where it is stated that the systems with underfloor air distribution are more efficient than the conventional ones (ceiling air distribution), this work also concludes that the system with underfloor air distribution is more efficient, presenting an energy saving indicator around 33%, for the following condition: floor to ceiling height of 3.50 m; supply air temperature of 19 ° C; and enthalpy control. The results of this research also indicate that the use of the enthalpy control has a greater influence on the energy savings compared to the increase of the supply air temperature or the floor to ceiling height.