Air Conditioning Research Papers - Academia.edu (original) (raw)

At the conclusion of a noise annoyance survey in air-conditioned offices a new parameter was proposed. The aim was to define a noise index well correlated with subjective ratings of noise annoyance and able to account for the imbalance of... more

At the conclusion of a noise annoyance survey in air-conditioned offices a new parameter was proposed. The aim was to define a noise index well correlated with subjective ratings of noise annoyance and able to account for the imbalance of the noise spectrum. As the RC Mark II procedure for rating the noise of HVAC systems in buildings introduced the “quality assessment index”(QAI), which provides a measure of the spectral imbalance of a noise, the combination of this parameter with the RC criterion number (which only measures noise ...

The presence of liquid refrigerant in the compressor cylinder during operation, or liquid slugging, is one of the most common causes of failure in reciprocating compressors. We propose to detect this fault by analyzing the electrical... more

The presence of liquid refrigerant in the compressor cylinder during operation, or liquid slugging, is one of the most common causes of failure in reciprocating compressors. We propose to detect this fault by analyzing the electrical current flowing into the compressor and identifying the chan ge in the load on the motor caused by the presence of liquid in the compressor cylinder. Two different types of liquid slugging are examined in this paper. In the first, small volumes of liquid are ingested during the steady-state operation of the compressor; in the second, small volumes of liquid are present at the suction port of the compressor immediately prior to the compressor start. Experimental data from a 1-ton split air conditioning system is used to demonstrate methods for identifying these faults.

A numerical model was developed for the computation of the wind field, air temperature and humidity in the urban canopy layer and in the atmospheric boundary layer above urban areas. The model is of k–ε type. The ensemble-spatial averaged... more

A numerical model was developed for the computation of the wind field, air temperature and humidity in the urban canopy layer and in the atmospheric boundary layer above urban areas. The model is of k–ε type. The ensemble-spatial averaged three-dimensional Reynolds equations, equation of continuity, turbulent kinetic energy equation (k-equation), and equation for dissipation rate of turbulent energy (ε-equation) are solved together with equations of heat and moisture transfer in the air. Inside the urban canopy layer, volumes of buildings and other urban structures are accounted for by a spatial averaging procedure. With given average building height and building width for each grid mesh, effects of buildings on the momentum transfer are modelled by introducing a form drag force. Temperatures of the ground surface, building walls or roof are computed by the solution of the heat conduction equation in the ground or walls, roof. Evaporation at the ground surface is evaluated using a Bowen ratio. The exhausted heat by building air conditioning is evaluated by employing a building air conditioning model. This heat together with traffic-induced artificial heat are accounted for in the model as heat sources. A numerical model for the momentum, heat and moisture transfer in the plant canopy is also coupled to the model to investigate the effects of vegetation on the urban climate. Verification of the model against observational data in the Tokyo Metropolitan area, Japan, reveals that the model is capable of simulating the momentum, heat and mass transfer in the urban boundary layer. Especially, the model can compute air temperature, humidity and wind velocity at the street level, which cannot be computed by a general above city atmospheric circulation model.

Among the broad varieties of power supply in Afghanistan such as city power produced from water dams, fuel generators, and imported electricity from neighboring countries, solar energy production is growing at a noticeable pace. Its... more

Among the broad varieties of power supply in Afghanistan such as city power produced from water dams, fuel generators, and imported electricity from neighboring countries, solar energy production is growing at a noticeable pace. Its preference is because of cost and sustainability perimeters. Given the climate of the country air conditioning inside buildings is required throughout the year, which is an important requirement for the comfort of its residents. Because it requires a great amount of energy, therefore, most companies are working on different principles to provide new products of solar air conditioning systems. The solar air conditioning system provides heating and cooling by utilizing solar energy. Recently, climate change and air pollution proved to be a major challenge for humans, and the current rate of resource consumption will result in a total depletion of natural energy resources in the earth. In this paper, we are assessing the feasibility study of solar-powered a...

The enclosed lift lobby distinguishes itself as a unique form of region categorised under building transitional spaces. This paper reports on an evaluation of thermal comfort conditions in a prominent transitional space in buildings which... more

The enclosed lift lobby distinguishes itself as a unique form of region categorised under building transitional spaces. This paper reports on an evaluation of thermal comfort conditions in a prominent transitional space in buildings which is the enclosed lift lobby of an educational institution in Malaysia, using field survey which included objective measurement and subjective assessment. The temperature set-point of air conditioner was increased and maintained at 26°C to investigate the human thermal perceptions in the enclosed region. Comparison was made on the percentage of thermal sensation, preference, acceptability and general comfort votes obtained from field survey. The outcomes clearly indicated that the human thermal perception in the enclosed lift lobby would be directly proportional to the level of human occupancy, and any sudden temperature change could lead to thermal discomfort of occupants. The respondents generally preferred to have cooler environment, rather than w...

Field observations were carried out to determine the influence of a park on the urban summer climate in the nearby areas. The possibilities of reduction in air conditioning energy were investigated. Air temperature, relative humidity and... more

Field observations were carried out to determine the influence of a park on the urban summer climate in the nearby areas. The possibilities of reduction in air conditioning energy were investigated. Air temperature, relative humidity and other meteorological factors were measured at many locations inside a park and in the surrounding areas in the Tama New Town, a city in the west of the Tokyo Metropolitan Area, Japan. The observations indicated that vegetation could significantly alter the climate in the town. At noon, the highest temperature of the ground surface of the grass field in the park was 40.3 °C, which was 19 °C lower than that of the asphalt surface or 15 °C lower than that of the concrete surface in the parking or commercial areas. At the same time, air temperature measured at 1.2 m above the ground at the grass field inside the park was more than 2 °C lower than that measured at the same height in the surrounding commercial and parking areas. Soon after sunset, the temperature of the ground surface at the grass field in the park became lower than that of the air, and the park became a cool island whereas paved asphalt or concrete surfaces in the town remained hotter than the overlying air even late at night. With a size of about 0.6 km2, at noon, the park can reduce by up to 1.5 °C the air temperature in a busy commercial area 1 km downwind. This can lead to a significant decrease of in air conditioning energy in the commercial area.

As a result of the Kyoto Protocol, the use of R134a in air conditioning system of new cars is going to be forbidden in the EU due to the high Global Warming Potential (GWP) of this substance. Carbon dioxide (CO2) is one of the possible... more

As a result of the Kyoto Protocol, the use of R134a in air conditioning system of new cars is going to be forbidden in the EU due to the high Global Warming Potential (GWP) of this substance. Carbon dioxide (CO2) is one of the possible alternatives as a cooling agent in mobile air conditioning applications and is desirable since it is a natural refrigerant. Cooling cycles using CO2 are currently achieving COP simi-lar to those of R134a cycles but there are promising options to further improve COP. One possibility is the application of an ejector instead of the valve. A Modelica library was developed that allows compu-tation of ejector cooling cycles in steady state with simplified component models that can be used as a design tool for the construction of an ejector proto-type. The library uses a new object-oriented library that serves as an interface to external medium librar-ies to compute thermodynamic and transport proper-ties for the refrigerant.

The operation of two 60 m2 solar air heaters serving a large studio teaching space has been monitored for a twelve month period. The solar contribution of the heaters was found to be less than 5%, and in some instances the heaters... more

The operation of two 60 m2 solar air heaters serving a large studio teaching space has been monitored for a twelve month period. The solar contribution of the heaters was found to be less than 5%, and in some instances the heaters actually contributed to the space heating load. A validated mathematical model of the studio and it's heating, ventilation and air conditioning system was used to investigate performance improvement strategies. It was found a different control strategy and recommissioned control sensors would substantially improve the solar air heater performance. This paper reports the performance of a large solar air heater (SAH) installed on a university building in southern Victoria. The paper begins with a description of the building and the solar air heating system. The methodology used to assess the performance of the solar heating system is described, followed by the results. A validated mathematical model was used to investigate performance improvement strate...

Current difficulties surrounding air conditioning systems involve an increase in input air aimed at improving indoor air quality (IAQ), the financial costs arising from energy consumption and external environmental impact, linked to the... more

Current difficulties surrounding air conditioning systems involve an increase in input air aimed at improving indoor air quality (IAQ), the financial costs arising from energy consumption and external environmental impact, linked to the greenhouse effect (GWP) and the destruction of the ozone layer (ODP). One alternative technique which offers an adequate combination of IAQ and acceptable energy saving is the

Due to its considerable impact on climate, bus air conditioning systems are being pushed to take a new and sustainable path. Electric buses relying on transcritical CO2 air conditioning units are perceived to be eco-friendly and... more

Due to its considerable impact on climate, bus air conditioning systems are being pushed to take a new and sustainable path. Electric buses relying on transcritical CO2 air conditioning units are perceived to be eco-friendly and future-proof solutions to achieving such a target. However, in order to have highly efficient air conditioning systems, the CO2 charge needs to be optimized. In this paper the energy and exergy-based analyses were performed to investigate the effect of normalized refrigerant charge on the system performance by using a test rig of a transcritical CO2 air conditioning unit for an 8 m electric bus. Results showed that the normalized refrigerant charge range of 0.248~0.336 was recommended in order to ensure the maximum coefficient of performance (COP). In addition, in sufficient charge conditions, the optimal COP, cooling capacity and exergy efficiency were 1.716, 18.97 kW and 29.79%, respectively, under the standard refrigeration condition of 35 °C/27 °C. As the ambient temperature rose from 35 °C to 40 °C, the COP, cooling capacity and exergy efficiency decreased by 16.03%, 10.90% and 12.22%, respectively. Furthermore, the exergy efficiency was found not to be sensitive to slightly insufficient charge, whereas overcharge was observed to be even beneficial to exergy efficiency under the condition of ensuring the maximum COP. In addition, insufficient refrigerant charging seriously affected the irreversible losses in the indoor and outdoor heat exchangers, whereas slight overcharge had little effect on the component exergy efficiency. Finally, the need to improve the CO2 compressor efficiency to enhance the system performance was revealed.

Abstract For indoor environments, thermal discomfort must be clearly distinguished from the air pollution caused by outdoor air as well as by inside polluting agents. Full air conditioning of a room requires the introduction of a minimum... more

Abstract For indoor environments, thermal discomfort must be clearly distinguished from the air pollution caused by outdoor air as well as by inside polluting agents. Full air conditioning of a room requires the introduction of a minimum ventilation air flow whose characteristics ...

Temperature and humidity control are crucial in next generation greenhouses. Plants require optimum temperature/humidity and vapor pressure deficit conditions inside the greenhouse for optimum yield. In this regard, an air-conditioning... more

Temperature and humidity control are crucial in next generation greenhouses. Plants require optimum temperature/humidity and vapor pressure deficit conditions inside the greenhouse for optimum yield. In this regard, an air-conditioning system could provide the required conditions in harsh climatic regions. In this study, the authors have summarized their published work on different desiccant and evaporative cooling options for greenhouse air-conditioning. The direct, indirect, and Maisotsenko cycle evaporative cooling systems, and multi-stage evaporative cooling systems have been summarized in this study. Different desiccant materials i.e., silica-gels, activated carbons (powder and fiber), polymer sorbents, and metal organic frameworks have also been summarized in this study along with different desiccant air-conditioning options. However, different high-performance zeolites and molecular sieves are extensively studied in literature. The authors conclude that solar operated desicca...

We have studied a low energy building on a campus of the University of California. It has efficient heating, ventilation, and air conditioning (HVAC) systems, consisting of a dual-fan/dual-duct variable air volume (VAV) system. As a major... more

We have studied a low energy building on a campus of the University of California. It has efficient heating, ventilation, and air conditioning (HVAC) systems, consisting of a dual-fan/dual-duct variable air volume (VAV) system. As a major building on the campus, it was included in two demand response (DR) events in the summers of 2008 and 2009. With chilled water supplied by thermal energy storage in the central plant, cooling fans played a critical role during DR events. In this paper, an EnergyPlus model of the building was developed and calibrated. We compared both whole-building and HVAC fan energy consumption with model predictions to understand why demand savings in 2009 were much lower than in 2008. We also used model simulations of the study building to assess pre-cooling, a strategy that has been shown to improve demand saving and thermal comfort in many types of building. This study indicates a properly calibrated EnergyPlus model can reasonably predict demand savings from...

This paper describes ongoing research that is being conducted at the University of Algarve involving the design and utilization of information and communication technologies for special needed people. We present a virtual keyboard project... more

This paper describes ongoing research that is being conducted at the University of Algarve involving the design and utilization of information and communication technologies for special needed people. We present a virtual keyboard project that interfaces with a text-to-speech synthesizer. The virtual keyboard contains a built-in dictionary and a simple algorithm that allows people with disabilities to write much faster