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Abstract: As dehumidification is one of the most important tasks of environment control of the building, it is necessary to know the energy efficiency of dehumidification processes. The energy efficiency can give the energy cost of drawing moisture from indoor air to the outside environment. This paper presents analysis of the ideal cost of dehumidification process by a liquid desiccant cycle. Formulas to calculate ideal efficiency of dehumidification process are obtained, which is determined by indoor temperature, outdoor temperature, and the temperature of the intersection point of the iso-relative humidity line of indoor air and the iso-humidity ratio line of outdoor air. The ideal efficiency of the condensing dehumidification method is lower than the ideal dehumidification process, due to the fact that condensing dehumidification method must dehumidify the air at the temperature of dew point. Results from this paper can be used as theoretical foundation for the further analysis of various dehumidification methods and the development of new dehumidification processes. [ABSTRACT FROM AUTHOR]

Abstract: A retrofit study was conducted in an unoccupied manufactured house to investigate the impacts of airtightening on ventilation rates and energy consumption. This paper describes the retrofits and the results of the pre- and post-retrofit assessment of building airtightness, ventilation, and energy use. Building envelope and air distribution systems airtightness were measured using fan pressurization. Air change rates were measured continuously using the tracer gas decay technique. Energy consumption associated with heating and cooling was monitored through measurement of gas consumption by the forced-air furnace for heating and electricity use by the air-conditioning system for cooling. The results of the study show that the retrofits reduced building envelope leakage by about 18% and duct leakage by about 80%. The reduction in the house infiltration rates depended on weather conditions and the manner in which the heating and cooling system was controlled, but in general these rates were reduced by about one third. The energy consumption of the house for heating and cooling was reduced by only about 10%, which is relatively small but not totally unexpected given that infiltration only accounts for a portion of the heating and cooling load. [Copyright &y& Elsevier]

Abstract: Energy used for building heating, ventilating and air conditioning contributes to a great share in the total energy consumption worldwide. Better understanding and management of energy distribution in those processes is essential for the improvement of process quality and efficiency of energy use. This paper presents the data-based mechanistic modelling approach which has been developed to model the dynamic indoor temperature distribution in an imperfectly mixed ventilated airspace based on energy input to the system. The combination of classical heat balance differential equations and the data-based modelling techniques for continuous-time system has brought a robust dynamic model suitable for model-based controlling and yet providing a profound insight at the energy and temperature distributions in ventilated systems. The effect of changing heat input on the temperature distribution inside a ventilated structure was studied. Dynamic response of indoor temperature to varying energy input could be explained by a second order transfer function model with a high coefficient of determination (R 2 >0.99), a low Young Identification Criterion (YIC<−2.3) and a low model standard error (SE<0.028°C). The physically meaningful model parameters as local heat load fraction γ and the coefficient of local temperature change h (°CJ−1) were revealed. This modelling approach is very useful for future design of model-based predictive controller for zonal control of indoor temperature by the direct adjustment of heat load into ventilated structures. [Copyright &y& Elsevier]

Abstract: This paper presents a top-down strategy for detecting faulty HVAC units across different levels. Energy flow models of HVAC units are developed while the energy is the main feature extracted from the vast amount of real-time data of the HVAC system in a building. A temporal and spatial partition strategy for analyzing HVAC units is proposed. The partition takes into account of architectural, environmental, and human factors. The partition strategy leads to more appropriate thresholds for fault detection. Numerical examples are presented to demonstrate the detection of a systemwide fault and a fault at the VAV level. [Copyright &y& Elsevier]

Abstract: The objective of this paper was to study the application and working fluid type of a closed-loop oscillating heat pipe with check valves on energy consumption in split type air conditioning system. In the experiment, the CLOHP/CV was fabricated from the copper tube with the diameter of 2.03mm. In the usual range of 20–27°C indoor design temperature and 50% relative humidity. R134a, R22 and R502 refrigerant was used as working fluid in the CLOHP/CV set for this study. In comparison of the type with a conventional air conditioning system and that with the CLOHP/CV air conditioning system, the results have shown that; the new cooling load had increased 3.6%, the latter gave the highest value of 14.9%, 17.6% for COP and EER, respectively. The highest value of heat flux was 5.19kW/m2 with R134a was used as the working fluid, at overall operating temperature. The results of this study are expected to guideline as they improve the performance of the air conditioning system in buildings, which reduce its energy consumption. [Copyright &y& Elsevier]

Abstract: As global warming continues, the current trend implies that the uptake of air conditioning in the residential sector will go up, thus potentially increasing domestic cooling energy consumption. In this context, this paper investigates the significance of behavioural, physical and socio-economic parameters on cooling energy in order to improve energy efficiency in residential buildings. It demonstrates that such factors exert a significant indirect as well as direct influence on energy use, showing that it is particularly important to understand indirect relationships. An initial study of direct factors affecting cooling energy reveals that occupant behaviour is the most significant issue (related to choices about how often and where air conditioning is used). This is broadly confirmed by path analysis, although climate is seen to be the single most significant parameter, followed by behavioural issues, key physical parameters (e.g. air conditioning type), and finally socio-economic aspects (e.g. household income). [Copyright &y& Elsevier]

Abstract: An experimental study on performance of digital variable multiple air conditioning system under part load conditions in hot summer and cold winter zone was conducted in this paper. The effects of outdoor air temperature and on-unit ratio on total power consumption in 1h, hourly heating performance factor or hourly energy efficiency ratio were analyzed by experiments. The variations of hourly heating performance factor (or hourly energy efficiency ratio) and total power consumption in 1h with part load value under different outdoor air temperature were obtained. The results indicate that digital variable multiple air conditioning system can keep economical and reliable operation under part load conditions. And it is necessary to study the index which may reflect the seasonal energy consumption of digital variable multiple air conditioning system. [Copyright &y& Elsevier]

Abstract: The large thermal time constant of thermally activated building systems (TABS) hampers communication between the system''s production and emission. Therefore, conventional building control strategies, typically using room temperature feedback, are unadapted to control thermal comfort efficiently. In this paper, measurement data and simulation results reveal that unadapted TABS control has a dramatic impact on overall energy performance. Measurements in a TABS building with room temperature feedback show the HVAC system switching between heating and cooling in a very short time frame. A simplified, generic room model is used to simulate, understand and evaluate this behaviour. For room temperature feedback control, only 45% of the cold and 15% of the heat produced actually controls room temperature. The remainder is stored in the TABS and exchanged between the heating and cooling system. Enlarging the heating-to-cooling set point band improves this ratio, while maintaining thermal comfort. On the other hand, night time operation control of the circulation pump, adapted to the TABS thermal time constant, eliminates this ‘unused’ energy completely. In this case, however, even with perfect heat gain forecasts, it is difficult to avoid room temperatures dropping below thermal comfort limits during initial office hours. Hence, a supplementary air-conditioning system seems inevitable. [Copyright &y& Elsevier]

Abstract: In harsh climatic regions, buildings require air-conditioning in order to provide an acceptable level of thermal comfort. In many situations buildings are over cooled or the HVAC system is kept running for a much longer time than needed. In some other situations thermal comfort is not achieved due to improper operation practices coupled with poor maintenance and even lack it, and consequently inefficient air-conditioning systems. Mosques represent one type of building that is characterized by their unique intermittent operating schedule determined by prayer times, which vary continuously according to the local solar time. This paper presents the results of a study designed to monitor energy use and thermal comfort conditions of a number of mosques in a hot-humid climate so that both energy efficiency and the quality of thermal comfort conditions especially during occupancy periods in such intermittently operated buildings can be assessed accurately. [Copyright &y& Elsevier]

Abstract: Axiomatic design (AD) is a theory that helps to develop new design objects and allows one to evaluate the quality of designs. The aim of this paper is to apply this theory to the design of heat ventilation and air-conditioning (HVAC) systems and to come to conclusions about the design quality of some specific applications. The focus is the comfort and energy consumption in commercial buildings in South European climates. The discussion contains a brief description of variable air volume (VAV) systems and dedicated outdoor air systems (DOAS) with terminal units, such as fan-coils, induction units and chilled ceilings. Occasionally, the DOAS design should include over-cooled outdoor air in order to ensure an extra cooling means. According to the AD''s first axiom, ideal systems are independent or decoupled. Our conclusion is that VAV and DOAS with induction units are coupled designs, and on the other end, DOAS with fan-coils or chilled ceilings are decoupled designs. In addition, over-cooling outdoor air (OA) flow couples the OA flow with the indoor heat removable needs. [Copyright &y& Elsevier]

Abstract: There are many reports about faulty status in building air-conditioning systems recently. It becomes difficult to keep indoor air temperature appropriately as faults occur, and the faults cause waste of building energy consumption. The model-based fault detection and diagnosis (FDD) methods have been researched for specific parts of air-conditioning system such as chillers, coils, variable air volume units (VAV units), etc. It needs, however, much time and labor to monitor and check every single part because we cannot predict where and when the faults occur. The purpose of this study is to examine indoor air temperature changes and energy consumption increase when faults occur and to develop an easy-to-use FDD tool that helps to find out the faulty place through the whole building air-conditioning system. And then, we treat the reliability of the proposed FDD tool and effectiveness to control of indoor environment deterioration and energy consumption increase by the tool is evaluated based on building air-conditioning system simulation in this paper. [Copyright &y& Elsevier]

Abstract: In the air conditioning (AC) industry chilled water storage (CWS) systems are one form of cool thermal storage technology that can be used to time shift the electrical load of the system from the peak day periods to off peak night time periods. In this paper the data for the actual exported and generated electrical energy obtained for the power stations in Kuwait has been used to estimate the electrical energy consumption and the peak electrical load of AC systems. Since the chiller in an air cooled AC system represent more than 75% of the total electrical power consumed by an AC system during the peak demand period, the impact of using CWS systems with alternative operating strategies including partial (load levelling), partial (demand limiting) and full load has been investigated. In our conclusions we estimate that approximately 45% of the total annual exported electrical energy is consumed solely by AC systems as a result of the very high ambient temperatures occurring between March and October. Furthermore, it is estimated AC systems represent about 62% of the peak electrical load. The results demonstrate that CWS can reduce the peak electrical load of a chiller in an air cooled AC system by up to 100% and reduce the nominal chiller size by up to 33% depending upon the operating strategy adopted. This is achieved with only a 4% increase in power consumption of the chiller for all CWS strategies except for full storage where the energy consumption actually decreases by approximately 4%. [Copyright &y& Elsevier]