ENCIT2012-012 EXPERIMENTAL STUDY OF A CYCLONE SCRUBBER AIR CONDITIONING SYSTEM USING FACTORIAL DESIGN - PDF
Ricardo Boulos Elias, Arai Augusta Bernardez Pecora, Unicamp, Brazil
Abstract: This work reports the results obtained in the experimental evaluation of an American type cyclone which has been modified and adapted to perform environmental air conditioning by evaporative cooling. Equipment was fitted with nozzles atomizers, which perform the injection of liquid transversely to the gas stream. The tests were carried out following a full factorial design of experiments in order to obtain the influence of the atomizer holes diameter and of the liquid/air flow ratio on the cyclone performance . The diameter of the atomizer insert holes was in the range of 2.8 to 3.6 mm and the liquid/air flow ratio was from 0.65 to 0.76 L/m3. The saturation efficiency (Es) of the cyclone was analyzed through the Response Surface Methodology (RSM). Saturation efficiencies between 45.9 and 62.2 \% were obtained. The use of statistical techniques allowed the proposition of empirical correlations to predict the behavior of the system regarding the studied operational range. The results show that the cyclone scrubber equipment is a viable alternative to air conditioning for human standards.
Keywords:Cyclone scrubber; Factorial experimental design; Evaporative cooling.
Presentation Schedule: NO PRESENTATION.
ENCIT2012-045 MODELING HEAT AND MOISTURE TRANSFER THROUGH BUILDING LOWER THERMAL BRIDGES - PDF
Gerson Henhique Santos, UFPR, Brazil
Nathan Mendes, PUCPR, Brazil
Abstract: Multidimensional effects through porous building elements is normally disregarded by simulation tools due to many difficulties such as modeling complexity, computer run time, numerical convergence and highly moisture-dependent properties. Therefore, in order to analyze the effects of building lower thermal bridges, a multidimensional model has been developed to calculate the coupled heat, air and moisture transfer through building envelopes. The linearized set of discretized governing equations has been obtained by using the finite-volume method and were solved via the MultiTriDiagonal-Matrix Algorithm, improving substantially the numerical stability and reducing the computer run time. In the results section, the multidimensional effects in the lower thermal bridges formed by the soil, wall and floor are shown and analyzed in terms of temperature and relative humidity profiles.
Keywords:thermal bridges; porous media; building simulation.
Presentation Schedule: Monday, 17:20-17:40. Session: HVR1. Presenter: Gerson Henrique dos Santos.
ENCIT2012-057 ON THE MODELING OF A ROOM AIR CONDITIONER - PDF
Gustavo Cherem-Pereira, Nathan Mendes, PUCPR, Brazil
Abstract: Evaporator and condenser of a room air conditioner is semi-empirically modeled based on test data and some parameters, mixing both analytical and empirical method. The methodology allows to obtain a comprehensive model to be integrated to building energy simulation models and to be an interesting tool to analyze and optimize the system as well as learn about the influence of changing or modifying components on the global behavior of the air conditioner. The experimental data, from which the heat exchangers models were created, were obtained in calorimeters according to ISO standard. The results show good agreement when compared to an extensive experimental database where various parameters are varied.
Keywords:Room Air Conditioners; Heat Exchangers; Semi-empirical Modeling.
Presentation Schedule: Monday, 18:00-18:20. Session: HVR1. Presenter: Nathan Mendes.
ENCIT2012-181 NUMERICAL ANALYSIS OF WINDOWS AND FURNITURE INFLUENCE ON THE AIRFLOW IN NATURALLY VENTILATED OFFICE ENVIRONMENTS - PDF
Flávio Bomfim Mariana, Arlindo Tribess, USP, Brazil
Abstract: Among the spread of sustainable concept it has been found an increase interest on systems that have low or zero energy consumption. Similarly, there is a growing concern with indoor environmental quality. Natural ventilation systems can match these expectations, but detailed analysis on the airflow conditions is necessary to obtain an environment which provides good comfort conditions. The present report studied the influence of furniture on the airflow in a naturally ventilated office, as well as the influence of the window geometry, with computational fluid dynamics. Results showed that the window geometry has a more significant influence on the airflow distribution, and consequently, also on the temperature field, especially on the leeward side of the office. Maxim-air windows direct the airflow towards the ceiling, which helps to increase the air velocity all over the environment. Vertical sliding windows reduce in 32\% the airflow rate and direct the airflow more horizontally, worsening environmental conditions. The higher partitions make the velocity field less uniform, prejudicing the heat removal by forced convection and increasing the presence of thermal plumes due to natural convection. Offices with vertical sliding windows were more sensible to the variation of partitions height, mainly due to the less intense velocity field. In offices with maxim-air windows, the 0.90m and 1.10m height partitions presented similar results, permitting the use of 1.10m height partitions to enhance occupant privacy without jeopardizing the environmental conditions. Architects and engineers can use these tools to enhance the office environment design.
Keywords:Natural Ventilation; CFD; Thermal Comfort; Office Buildings.
Presentation Schedule: Monday, 17:00-17:20. Session: HVR1. Presenter: Flávio Bomfim Mariana.
ENCIT2012-146 MEASUREMENT AND MODELING OF THERMAL COMFORT CONDITIONS IN A ROOM VENTILATED WITH SPLIT SYSTEM - PDF
Marcelo Luiz Pereira, Rogério Vilain, IFSC, Brazil
Arlindo Tribess, USP, Brazil
Abstract: The ISO 7730 Standard defines thermal comfort as the mental condition that expresses satisfaction with the thermal environment. The evaluation of thermal comfort in indoor environments is usually performed by the measurement of air temperature, global temperature (mean radiant temperature), velocity and relative humidity. In recent years, however, there has been an increasing use of CFD software for numerical solution of flow and exchange of heat and mass for calculation of the environmental parameters. Therefore, in this work the conditions of thermal comfort in a classroom with a split system are analyzed using experimental and numerical results. The air temperature and velocity were measured and compared with the numerical results. The measurements and numerical results, showed a reasonable agreement and the analysis allowed the identification of the thermal characteristics of the environment as well as comfort conditions. It was found that the measured and predicted air temperatures were within the limits of thermal comfort standards. However, the air velocity showed a significant variation in some points in the room, which revealed great difficulty in obtaining uniform conditions for thermal comfort in the classroom air-conditioned with split system. The position in front of the blackboard where the flow inlet hits directly showed to have the most thermal dissatisfaction, caused by the air motion that can lead to drought sensation.
Keywords:Thermal comfort; classroom; CFD; numerical solution.
Presentation Schedule: NO PRESENTATION.
ENCIT2012-375 ANALYSIS OF DESICCANT VENTILATION AND RECIRCULATION CYCLES UNDER DIFFERENT ENVIRONMENTAL CONDITIONS - PDF
Felipe Oliveira Quintanilha, Leandro Alcoforado Sphaier, UFF, Brazil
Carlos Eduardo Leme Nóbrega, CEFET-RJ, Brazil
Abstract: Desiccant cooling systems have been increasingly investigated due to their environmental friendliness. A known characteristic of these type of cycles, is that they can be significantly influenced by outdoor conditions. Hence, the purpose of this study is to investigate, the operation of a desiccant cooling cycle is for various environmental conditions, and to show how these cycles can be adjusted to meet thermal comfort requirements. The analysis is based on a simple numerical procedure for desiccant cooling simulation in which the overall system operation is calculated from individual cycle components' characteristics. With the employed methodology, the conditioned space state is calculated for different environmental conditions and compared to a standard comfort-zone. The results show how the effectiveness of evaporative coolers and the regeneration temperature influence the conditioned space.
Keywords:dehumidification; evaporative cooling; desiccant wheel; cooling cycle; recirculation.
Presentation Schedule: Monday, 18:20-18:40. Session: HVR1. Presenter: Felipe Oliveira Quintanilha.
ENCIT2012-182 TRANSIENT BEHAVIOR FOR THERMAL EFFICIENCY OF A COMBUSTION HEATER SUBJECTED TO ASH FOULING - PDF
Ricardo Cecilio Moreno das Neves, Elson Avallone, Padilha Alcides, Vicente Luiz Scalon, UNESP, Brazil
Abstract: Constant demands for the reduction of energy waste and increase of the thermal efficiency, reducing operating costs, have been an important parameter in processes that make use of thermal machines, like boilers. Within the draft boilers, air preheaters play a key role in determining the absolute efficiency of heat recovery of low level, such as the flue gases before sending it to the atmosphere. In Overall, for a common boiler every 22°C recovered of the flue gases by an air preheater, the absolute efficiency of the equipment may rise by about 1\%. The proposed work experimentally aims to show the loss of thermal efficiency of an air preheater of a superheated steam boiler during its operation. This analysis covers the relationship of loss of heat exchange by fouling and clogging of the heat exchanger tube bank during its operation process. To analyze the thermal losses were used measurements of maximum velocities and average velocities by pitot tube and venturi tube, together with Bernoulli equation, by calculating the mass flow rate of the input current of air and flue gas, connecting them with the inlet and outlet temperature for each flow.
Keywords:Boiler; Air preheater; Pitot tube; Venturi tube; Bernoulli equation.
Presentation Schedule: Monday, 17:40-18:00. Session: HVR1. Presenter: Ricardo Cecilio Moreno das Neves.