Types Of Air Conditioning Systems Research Articles

Design of ionic liquids as a desiccant for the liquid desiccant type air conditioning system

Abstract Recently, liquid desiccant air conditioners (LDACs) have gained rapidly growing interest as an important candidate for an energy-efficient air conditioner. By enabling moisture absorption from the air, ionic liquids (ILs) can serve as a novel desiccant source for LDACs. For insights into the design and optimization of ILs to this end, we herein present a survey of studies on dehumidification and other relevant properties of ILs and offer some molecular perspective on their feasibility as a desiccant.

A New Type of Air Conditioning System Based on Finned Ceiling Radiant Coupled with Independent Fresh Air and Its Thermal Comfort Experimental Study.

The traditional radiation air conditioning system has some problems, such as easy condensation, insufficient refrigeration capacity, complex structure, and control system. Therefore, this study proposes a new type of finned metal radiant plate with large heat flow per unit area, sufficient cooling capacity, and simplified heat exchange system, in order to realize large temperature difference between cooling and heating. The temperature field uniformity and thermal comfort test of a novel type of finned ceiling radiant panel and independent fresh air linked air conditioning system under summer cooling and winter heating circumstances are accomplished through artificially generated climate environments. The study's findings demonstrate that in the radiation and fresh air modes, the maximum interior temperature differential under cooling conditions does not rise over 2.1°C. The maximum temperature differential in the space at any one moment in the radiation and fresh air modes cannot be greater than 3°C when heating conditions are present. The fresh air's cooling and dehumidifying effects are clear. The dehumidification efficiency may reach 50%, and the moisture content ranges from 5.48 to 9.63 g/kg. With PMV ranging from −0.34 to 0.54, the enhanced air conditioning system in this research provides exceptionally good thermal comfort. Additionally, the finned radiant panel's installation area occupies just 14% of the ceiling, which is sufficient to fulfill the room's cooling and heating load needs as well as provide high thermal comfort and consistent indoor temperature. The theoretical investigation and practical implementation of the direct expansion radiant air conditioning system are both strongly supported by this research.

Design and Development of Solar Powered 360degree Automatic Air Cooler

Abstract: Evaporative coolers lower the temperature of air using the principle of evaporative cooling, unlike typical air conditioning systems which use vapor-compression refrigeration or absorption refrigerator. Evaporative cooling is the conversion of liquid water into vapor using the thermal energy in the air, resulting in a lower air temperature. The energy needed to evaporate the water is taken from the air in the form of sensible heat, which affects the temperature of the air, and converted into latent heat, the energy present in the water vapor component of the air, whilst the air remains at a constant enthalpy value. Vapor-compression refrigeration uses evaporative cooling, but the evaporated vapor is within a sealed system, and is then compressed ready to evaporate again, using energy to do so. Simple evaporative coolers water is evaporated into the environment, and not recovered. In an interior space cooling unit, the evaporated water is introduced into the space along with the now-cooled air; in an evaporative tower the evaporated water is carried off in the airflow exhaust. To Develop the Energy efficient, environment friendly direct evaporative air conditioning system having low operating cost suitable for hot and dry regions To Manufacture advanced 360-degree Rotating air cooler which rotates and provide air cooling in all directions. It can be used for domestic as well as Industrial applications. The temperature of dry air can be dropped significantly through the phase transition of liquid water to water vapor (evaporation). This can cool air using much less energy than refrigeration. In extremely dry climates, evaporative cooling of air has the added benefit of conditioning the air with more moisture for the comfort of building occupants

Comparative analysis of the energy efficiency of air-conditioner and variable refrigerant flow systems in residential buildings in the Yangtze River region

Two types of air-conditioning systems, named as room air conditioners (RAC) and multi-connected air-conditioners (variable refrigerant flow (VRF) systems) have become popular heating and cooling facilities for residential buildings featured with ‘part-time-part-space’ operation characteristics in the Yangtze River region. However, the research on the energy efficiency of these two systems in residential buildings is currently lacking. Based on the actual measured air-conditioning operation hours and demand characteristics, this study analyzed the annual operation performance of the two systems by modelling and simulation. In addition, a field test of twelve RACs and five VRFs in residential buildings was conducted in the Yangtze River region, showing the annual performance factors of VRFs and RACs ranged from 3.7 to 5.3 kWh·kWh−1 and 3.0 to 4.6 kWh·kWh−1, respectively. It is found that for the same operation hours and the total cooling capacity of VRF systems RACs, the VRF has low energy efficiency at low load ratios (generally less than 25%); which is the key barrier to its application in residential buildings in the Yangtze River region. It is suggested the RAC is the appropriate solution for heating and cooling a residential building with a ‘part-time-part-space’ operation mode as it is more energy-efficient. New advanced technologies for VRF systems are expected to be developed in order to adapt the part-load operation mode to achieve high energy efficiency. This study contributes to providing evidence for the decision-making of RAC and VRF systems for policymakers, and building and engineering designers in the context of energy efficiency for the region.

A Comparative Study of VRF Air Conditioning System over the Conventional Domestic Air-Conditioning System

All over the world there is a call to encourage sustainable energy thinking and implementation. There is an urgent need to consider sustainable solutions that are able to reduce energy consumption cost. In air conditioning field, the rise of the variable refrigerant flow systems has made big progress. This study focuses on cost analysis to evaluate the economic feasibility of conventional, VRF and VRF duct type air conditioning system. The hourly and daily energy consumption of both systems were characterized based on corresponding outdoor air temperatures. Results showed that VRF air conditioning system is 15% less costly than conventional air condition. Though VRF duct system is less costly than conventional VRF, the standard rooftop height of the studied building doesn’t support VRF duct type installation. Besides the open ducting line up will not look good and creating cover for these duct will pile up the cost further. The analysis also shows that the VRF system uses 17% and 73% less energy than the rooftop System in cooling and heating seasons, respectively. The implementation of this pilot result on National level will promote the use of sustainable energy technologies such as VRF system.

Multilayer thin-film based nanophotonic windows: static versus electrotunable design

To meet the global energy demand, rapid growth in fossil fuel consumption has significantly contributed to global warming. Judicious utilization of renewable energy resources could help to combat this global challenge. Here, we present a comparative study on the designs of static and electro-tunable ‘smart’ windows that could help to reduce the energy need of typical air-conditioning systems deployed in buildings and motor vehicles. Our design comprises insulator–metal–insulator multi-layered thin-films deposited over a silica glass substrate to filter visible and infrared solar radiation selectively. For static windows, we optimize our design to operate in diverse climatic conditions by choosing different combinations and thicknesses of metal and insulator layers. Whereas for electro-tunable windows, we use an electro–optic polymer as the insulator layers to dynamically control portions of transmitted solar radiation over a voltage range of −12 to +12 V. Through size-dependence analysis, we could safely assume that the performance of smart windows is less likely to degrade during experimental realization. Our designs are lithography-free, large-area compatible, polarization-independent, angle-insensitive, and robust to fabrication imperfections. The analytical results show a near-perfect match with the simulation findings. The theoretically calculated figure of merit indicates that our proposed smart windows can outperform industry-standard commercial windows.

Energy-saving all-weather window based on selective filtering of solar spectral radiation.

Passive all-weather windows, capable of selectively transmitting visible and infrared solar radiation, could help in bringing down fossil-fuel energy consumption globally by reducing the carbon footprint of typical air-conditioning systems for buildings and motor vehicles. Here, we report on designing metal-insulator-metal thin-films for application in passive windows, optimized for different climatic conditions. We analyze designs comprising different noble metals as well as their relatively inexpensive alternatives. By finding an optimal choice of materials and thicknesses of the metal and dielectric layers, our lithography-free simple design can provide all-weather solutions for passive windows with desired visible and infrared transmission/blocking capability. Obtained theoretical results agree well with full-wave simulations. Thus, our proposed designs enable developing low-cost, ultra-thin (thickness: 47-85 nm), polarization-independent, angle-insensitive (up to 83 deg), and large-area-compatible passive windows with improved solar-radiation control for different weather/climatic conditions. The figure-of-merit calculation shows that the relatively inexpensive metals used in our passive glasses can outperform industry-standard commercial glasses and previously reported infrared-blocking plasmonic glasses.

Heating performance evaluation of recirculation type air conditioning system using underground aquifer for greenhouse in winter.

Heating performance evaluation of recirculation type air conditioning system using underground aquifer for greenhouse in winter.

Thermo-statistical study of sustainable refrigeration system for stack flow heat recovery of combined gas turbine-steam turbine power generation

Abstract The major part of input heat of power plant is lost during the exhaust flow process and this flue gas has tremendous potential for heat recovery and cooling generation. The employment of LiBr-H2O based eco- friendly and less energy consumption vapour absorption refrigeration system (VARS) is integrated with stack flow unit of combined gas turbine and steam turbine (GT-ST) plant. If thestack flow temperature is maintained about 200–250 0C, the projected VARS is suitable for the generation of efficient cooling effect. The main highlights of this research work have been concluded in terms of exergy losses in components, exergetic& overall efficiency of combined plant. The maximum irreversibility has been found in combustion chamber (CC) of GT system and exhaust flow ofST system as 66.8% and 13.4% respectively. The effect of GT plant efficiency influences the overall performance. The proposed VARS performance coefficient estimated as 0.708 with 05 ton of refrigeration effect which is valuable achievement for space cooling purpose for plant infrastructure and efficiently it can replace high grade energy consumption vapour compression refrigeration system (VCRS) type air conditioning system. This eminence cooling technology of VARS system can save 10,440 USD yearly in terms of energy and carbon emission, and able to map the de-carbonized economy infrastructure. The methane fuel gas has found remarkable performance at 8 bar of compressor pressure and 900 0C GT inlet temperature (GTIT) of operating condition with all set of operating factors by using MLR method of DOE. The determination coefficient (R2) is computed as 0.991 which gives minimum deviation between actual and predicted results.

Exergy and Energy Analyses of Dual-Temperature Evaporator Split AC System Incorporated A Capillary Tube and A Two-Phase Ejector

This study was aimed to investigate performance of a split type air conditioning (SAC) system applying exergy destruction method. A numerical model was established based on exergy destruction analysis of a Condenser Outlet Split-Split Air Conditioning (COS-SAC) system integrated with dual-temperature evaporator and incorporated capillary tube and ejector as expansion devices. An experimental test system was also established to experimentally validate the model. Two type of refrigerants R-290 and R-22 were involved in the evaluations. The Coefficient of Performance (COP) of the ejector COS-SAC system, exergy destruction, and exergy efficiency were determined and compared with those in the SAC system utilizing capillary tube. The results showed there was a significant improvement in the overall exergy efficiency of the COS-SAC systems. The COP of the COS-SAC system was also found to be better than the COP of the SAC system.

Local and centralized conditioning systems

This article discusses two main types of air conditioning systems in office buildings: local and centralized systems. Since equipment developers, customers and users have different requirements for the design, installation and operation of air conditioning systems in office buildings, depending on the workload of buildings, location, external conditions, as well as space-planning solutions, air conditioning systems currently come in different types and configurations. Reliable knowledge of classification and the ability to distinguish one system from another is key when choosing the right air conditioning system for the customer. To form a proper understanding of the systems discussed, it is necessary to understand some of the basic terminology and principles of air conditioning systems. These include methods for system design criteria, load calculations (tangible and latent thermal loads, penetration loads, equipment and appliance loads, and air conditioning system requirements).

低コスト版個別分散型空調システム最適制御手法の開発 （第２報）冬期における制御システムの実証試験結果の考察について

低コスト版個別分散型空調システム最適制御手法の開発 （第２報）冬期における制御システムの実証試験結果の考察について

On the development of a simplified model for thermal comfort control of split systems

Despite split-type systems for cooling purposes became popular in countries such as China, Japan. India, Indonesia and Brazil, their use commonly promote high gradients of both temperature and air velocity in rooms which may cause considerable thermal discomfort. Hence, this work aims at developing a simplified thermal comfort index, based on temperature and air speed, in order to develop controllers for those types of air conditioning systems, replacing the traditional on-off temperature set-point control by an effective and inexpensive thermal-comfort based control. The work is focused on the assessment of comfort in classrooms by carrying out measurements according to ISO 7730 and ASHRAE 55 Standards, which defines the thermal satisfaction in occupied environments based on the PMV index. Specifically, the speed, temperature and relative humidity of the air and the mean radiant temperature of the room were measured at eight positions within the space. The field experiments were performed considering two 10.5-kW cooling capacity appliances installed in different positions relatively to the layout of the room, considering three levels of supply airflow (high, medium and low) and three set-point temperatures (23, 24 and 25 °C). An analysis of uncertainties is presented for PMV measurements and a regression analysis was applied to the measured data to determine a simplified correlation between thermal comfort (by means of the PMV index) air temperature and air velocity, aiming at developing afterwards a control device based on thermal comfort instead of temperature setpoint only. Results are shown in terms of distribution of air speed, air temperature and PMV index for the two configurations of equipment installation, as well as the resulting empirical model correlating thermal comfort index with both temperature and air speed. In addition, thermal comfort opinions from a survey are contrasted with the simplified thermal comfort model.

Influences of three types of air-conditioning systems on human thermal comfort

The influence of three ventilation systems, namely, the displacement ventilation system, the stratum ventilation system, and the underfloor air distribution system, on human thermal comfort was investigated at different supply air temperatures. We compared the air velocity, CO2 concentration, temperature, human thermal comfort, and energy utilization coefficient of the three systems at a supply air temperature range of 18–24 °C. The results showed that the underfloor air distribution system provided the best performances for CO2 dispersion and cooling at a supply air temperature of 18 °C. For optimal human thermal comfort, the underfloor air distribution should be chosen at a supply air temperature of 18 °C, the displacement ventilation system is suggested at a supply air temperature of 19 °C, 20 °C, and 24 °C, and the stratum ventilation system would be most suitable at a supply air temperature of 21 °C, 22 °C, and 23 °C.

Energy Efficiency Improvement Considerations at the Design Stage: The Case of Supermarkets

Supermarkets are large energy consumers, with high specific energy consumption than a majority of other commercial buildings. The main energy users are space cooling, lighting and the cold chain. This study was conducted as an initiative to demonstrate cost-effective, replicable ways to achieve significant electrical energy savings in supermarket buildings. The largest consumer of a Supermarket is the HV AC system, with about 50% of the total energy consumption. Of the total demand, the cold chain accounts for about 20% and lighting for about 15% while other equipment use about 15%. The Arpico Super Center, Kegalle, project was selected as a model maximise energy efficiency measures to save electricity. A saving of 22% of energy was achieved through efficiency improvements and a further 23% was self­generated from a roof mount solar power plant. An inverter type air conditioning system, automated fresh air control system with CO2 monitoring sensors, LED lamps, lighting controls (timer switch, light sensor, occupancy sensor), parabolic reflectors, skylights, variable frequency drives (VFD), power factor correction, energy efficient sewerage treatment plant, maximum use of gravity in water transportation and planned preventive maintenance are some of the energy efficiency improvement techniques implemented to achieve the study objectives. Almost all of the Arpico supercenter roofs are operating as solar power plants and more than 3 MWp installations completed by 2019, including 260 kWp of this project.

Particle and Carbon Dioxide Concentration Levels in a Surgical Room Conditioned with a Window/Wall Air-conditioning System.

One of the most important functions of air conditioning systems in operating rooms is to protect occupants against pathogenic agents transported by air. This protection is done by simultaneously controlling the air distribution, temperature, humidity, filtration and infiltration from other areas etc. Due to their low price, simple installation, operation and maintenance, window/wall air conditioning system have largely been used in operating rooms in Brazil, even if these types of equipment only recirculate the air inside the room without appropriate filtration and renovation with outdoor air. In this context, this work aims to analyse the performance of the window/wall air conditioning systems on indoor air ventilation in operating rooms by measuring particle number concentrations and carbon dioxide concentrations during different surgical procedures, in a single surgical room and in the nearby areas (corridor) for two cases: single surgery and two subsequent surgeries. In addition, the efficiency of the analysed air conditioning system was evaluated by comparing the ventilation level calculated in the surgical room with the ventilation required in order to maintain the carbon dioxide concentration within acceptable levels. The results showed that this type of air conditioning system is not appropriate for use in operating rooms since it cannot provide an adequate level of ventilation. The CO2 concentrations during surgeries, in fact, significantly exceeded acceptable values and a simultaneous increase in particle number concentration was observed. The results also showed that there is a high risk of contamination between subsequent surgeries in the same surgical room, due to residues of contaminants transported by the particles emitted during the surgeries that were not removed from the operating room by the air conditioning system. The particle number concentration measured in the second surgery, in fact, was approximately six times higher than in the first surgery.

Influence of air-conditioning systems on buoyancy driven air infiltration in large space buildings: A case study of a railway station

Large space buildings are widespread nowadays in the metropolis, in which the buoyancy driven air infiltration is extremely severe in heating/cooling seasons. This study pointed out that air-conditioning systems have a notable influence on air infiltration in large space buildings. A CFD model of a railway station was established and installed with typical air-conditioning systems, i.e., mixing ventilation (MV), displacement ventilation (DV), and radiant floor with displacement ventilation (RF+DV). Air infiltration rates of these cases were compared when the operative temperatures in the occupant zone were the same, respectively in the heating/cooling conditions. It is indicated that a uniform vertical temperature distribution in the heating condition and a significant thermal stratification in the cooling condition are potential to reduce air infiltration rate, which is best corresponded by RF+DV. Compared with the commonly-used stratified air-conditioning system with MV, RF+DV can reduce the air infiltration rate from 0.68 h−1 to 0.53 h−1 in the heating condition and save 38% of the heating capacity; it can reduce the air infiltration rate from 0.49 h−1 to 0.33 h−1 in the cooling condition and save 23% of the cooling capacity.

Thermodynamic analysis of two air conditioning systems with ice thermal storage in Egypt

An evaluation of using a thermal storage system utilized with air conditioning cycle in Egypt is the main aim of this paper. This study includes the addition of an energy storage system to two types of air conditioning systems: an all-air (AHU) and an all-water (FCU) air conditioning system. The exergy analysis is based on the transient analysis for a conventional cycle and a proposed ice storage cycle for the administration (FCU) and control (AHU) buildings in the New Abu-Qir Thermal Power Plant in Alexandria, Egypt, and it is presented as a case study. Results revealed that a significant increase in the system COP can be observed. The proposed ice storage cycles accomplish a 2.784 average coefficient of performance for the administration building and a 2.811 for control building, whereas the conventional system’s COP is 2.593 and 2.617 for both buildings, respectively. The ice storage tank can supply cooling for 8 h for the administration and control buildings. As a result, the ice storage systems save 53,517 kW h year−1 (6.88% power saving) for the administration building and 55,716 kW h year−1 (6.89% power saving) for the control building in 360 working days within the year (8640 h).

Energy use analysis of the variable refrigerant flow (VRF) system versus the multi - split unit using TRNSYS

The usage of air - conditioning in the residential and commercial buildings is becoming necessary because of the enormous demand for thermal comfort and healthy indoor environment. In achieving human thermal comfort and healthy indoor environment in a large building, there are many types of air conditioning systems that can be used, including the multi - split type unit and the variable refrigerant flow (VRF) system. The present research analyses the annual energy use of the existing ACMV system (multi - split type ceiling cassette unit) installed in the examined building, which located in the tropical area and compares it with a VRF system. The TRNSYS software is used to simulate both of these systems in accordance with the existing building’s characteristics and its operation. The existing building’s characteristics and its operation are obtained by conducting the site survey and field measurements in the building. In the current paper, the bin method is used to estimate the annual energy consumption for these systems. Based on the simulation results, the existing ACMV system consumes more energy in comparison to the VRF system by 13.62%. In addition, the annual operating cost of these systems has shown that the VRF system has a lower annual operating cost in comparison to the existing ACMV system by 13.63%. Besides that, the VRF system can accommodate an estimated payback period of around 6.6 years and an internal rate of return of 12.75%. The result has suggested that the VRF system has a great potential in energy savings and could reduce the electricity consumption in a large building significantly.

Study on load characteristics of different air conditioning systems in large space railway station

The railway station is a representative kind of large space building, whose air-conditioning system design has always been paid a lot of attentions. At present, the air-conditioning system at a train station is mainly a stratified air conditioning mode with spout air supply outlets, which has a significant thermal stratification and energy waste in winter. In this paper, a large space waiting room of one railway station in Wuhan is taken as the analysis example, and the CFD method is used to simulate the airflow and temperature distribution under different air-conditioning terminal devices in winter and summer. The airflow organization models of the waiting hall under three typical air-conditioning systems have been established including stratified air conditioning system, air handling unit special for large space system and floor radiation system. The temperature and velocity distributions of the large space in the waiting hall are comparatively simulated under each system. The temperature stratification, the amount of cooling and heating requirements are obtained for three types of air conditioning systems. According to minimum amount of the annual cooling and heating loads, a terminal device form of air-conditioning system which is suitable for large space is provided. The results can provide a reference for the design of air-conditioning systems for similar large space buildings.