Air Conditioning Solutions Research Articles

Return on Investment Analysis: Transitioning to Nearly-Zero Carbon Office Buildings

<p>為了輔佐政府順利執行淨零建築政策，以辦公建築作為研究對象，針對新建建築能效標示系統(BERSn)的三大關鍵控制因子，外殼節能效率(EEV)、照明節能效率(EL)與空調節能效率(EAC)，分析節能設備投資成本與能效得分的關係，提供最佳設備投資成本效益設計策略。首先，本研究建立近零碳辦公建築成本分析基準案為滿足當前綠建築標章的合格水準，即EAC=0.8、EL=0.8，定義近零碳投資成本分析條件為EAC≦0.5且EL≦0.5(節能率ESR應小於0.5)。透過28位空調專家問卷之基本型、中階型和高階型技術三種等級空調設備與空調節能技術的成本單價分析並擬定出最具成本效益與可行性的近零碳空調方案，確保空調設備總效率ACE ≤0.8之建議方案，以及節能技術(α1~α12)總節能率≧0.3來掌握空調之溢價成本，以最佳設備方案與節能技術成本進行溢價成本分析，空調溢價比為25.5~39.7%。在近零碳照明要求水準之下模擬發現在滿足作業平均照度500LUX條件下，LED平板燈或T8 LED燈具(包含具節能標章)即可達成EL≦0.5之照明水準。近零碳辦公建築的溢價成本以七個案例的地上樓地板面積與造價金額作為基準來計算近零方案之空調與照明溢價成本，造價溢價比為0.46~1.50%、投資回收年限約2.4~6.6年，結果顯示台灣近零碳設計成本比較低的主因為亞熱帶氣候的外殼節能效益有限，不強化外殼設計、照明不增加成本，能效措施在執行空調近零設計，不論規模、不論空調形式在國際比較下均為很低、很有投資效益之政策，可大幅減少推動近零建築政策的阻力，值得我政府與民間大力推動，也證實EEWH-BERS可以提供合乎邏輯、平價化且符合市場條件需求之可行解決方案。</p> <p> </p><p>To assist the government in successfully implementing the net-zero building policy, the study takes office buildings as the object of research and analyzes the relationship between the investment cost of energy-saving equipment and the energy efficiency score for the three key control factors of the new building energy efficiency labeling system (BERSn), namely, the energy efficiency of the building envelope (EEV), the energy efficiency of the lighting (EL), and the energy efficiency of the air-conditioning (EAC), and provides the optimal design strategy of the equipment cost-effectiveness of the investment. Firstly, this study establishes a benchmark for analyzing the cost of nearly-zero carbon office buildings to meet the current green building standard, i.e., EAC=0.8 and EL=0.8, and defines the conditions for analyzing the cost of nearly-zero carbon investment as EAC≦0.5 and EL≦0.5 (the energy saving rate ESR should be less than 0.5). Through the questionnaire of 28 air-conditioning experts, the cost unit price analysis of three levels of air-conditioning equipment and air-conditioning energy-saving technologies, namely basic, intermediate and advanced technologies, the most cost-effective and feasible nearly-zero-carbon air-conditioning solutions are formulated to ensure that the total efficiency of the air-conditioning equipment, ACE ≤ 0.8, and the total energy-saving rate of energy-saving technologies (α1 ~ α12) is ≧ 0.3 to master the air-conditioning increment cost. This increment cost is calculated based on the cost of optimal equipment and energy-saving technologies. The increment cost analysis is based on the optimal equipment and energy-saving technology costs, and the air conditioning increment ratio is 25.5~39.7%. Under the nearly-zero carbon lighting requirement level, the simulation found that under the condition of meeting the average illumination level of 500LUX, the LED flat panel lamp or T8 LED lamps (including the energy-saving label) can achieve the lighting level of EL≦0.5. There are seven cases of the floor area above ground floor and the project cost as a basis for calculating the nearly-zero program of air conditioning and lighting increment cost, the cost increment ratio of 0.60 ~ 1.50%, the payback period of about 2.8 ~ 7.7 years, the results show that Taiwan’s nearly-zero carbon design cost is lower mainly because of the energy-saving benefits of the building shell of the sub-tropical climate is limited, do not strengthen the shell design. Cost is not increased for building envelope and lighting; energy efficiency measures in the implementation of air-conditioning nearly-zero strategy, regardless of scale, irrespective of the air-conditioning form in the international comparison is meager, the very investment-effective policy can significantly reduce the resistance to promote the policy of nearly-zero building, it is worthwhile for the government and the community to encourage vigorously, but also to confirm that the EEWH-BERS can provide a logical, affordable and feasible solution to archived the needs of the market conditions.</p> <p> </p>

The Green Cooling Factor: Eco-Innovative Heating, Ventilation, and Air Conditioning Solutions in Building Design

This research investigates the compatibility of conventional air conditioning with the principles of green building, highlighting the need for systems that enhance indoor comfort while aligning with environmental sustainability. Though proficient in regulating indoor temperatures, conventional cooling systems encounter several issues when incorporated into green buildings. These include energy waste, high running costs, and misalignment with eco-friendly practices, which may also lead to detrimental environmental effects and potentially reduce occupant comfort, particularly in retrofit situations. Given the emphasis on sustainability and energy conservation in green buildings, there is a pressing demand for heating, ventilation, and air conditioning (HVAC) solutions that support these goals. This study emphasises the critical need to reconsider traditional HVAC strategies in the face of green building advances. It advocates for the adoption of innovative HVAC technologies designed for eco-efficiency and enhanced comfort. These technologies should integrate seamlessly with sustainable construction, use greener refrigerants, and uphold environmental integrity, driving progress towards a sustainable and occupant-friendly built environment.

Improvement of earth-to-air heat exchanger performance by adding cost-efficient soil

Geothermal research advances earth-to-air heat exchanger (EAHE) technology, offering promising air conditioning solutions for all buildings. Our study targets improved energy efficiency for the EAHE system, focusing on cost-effective approaches to enhance its technical, economic, and environmental performance. The thermal performance and economic viability of the EAHE system hinge on the thermal characteristics of the surrounding soil. The EAHE model features a single pipe with dimensions of 0.5 meters in diameter, 1 centimeter in thickness, and 10 meters in length. These pipes are strategically placed at depths of 1 meter, 2 meters, 3 meters, and 4 meters below the ground's surface. To optimize heat exchange efficiency while minimizing pipe length, we propose using a secondary soil material with high thermal conductivity as a lining for the EAHE pipes. Our innovative approach carefully considers the economic and environmental aspects of various lining materials, resulting in optimal performance at a minimal cost. Extensive simulations and data analysis lead us to identify an ideal lining material, naturally available, environmentally friendly, and cost-effective, ensuring peak efficiency. Our investigation assesses the EAHE system's thermal performance for both summer cooling and winter heating, demonstrating its effectiveness across seasons. This research underscores the case for utilizing EAHE systems during winter and autumn for heating and during spring and summer for cooling. Our findings are supported by robust performance indicators, confirming the effectiveness of our approach.

Enhancement of Chiller Performance by Water Distribution on the Adiabatic Cooling Pad’s Mesh Surface

Evaporative cooling is widely recognized as an energy efficient and environmentally-friendly air conditioning solution, and it has drawn a lot of market interest in recent years. However, this technology is accompanied by several challenges. For instance, insufficient evaporation due to poor and non-homogenous water distribution of the pre-cooling pad significantly reduces the cooling performance. The aim of the study is to develop a technique for numerical simulation of the distribution of a droplet liquid (water) on the mesh surface of an adiabatic cooler to improve the performance of air conditioning equipment. Modern computer-aided design (CAD)/computational fluid dynamics (CFD) programs were used to solve the issue. For the mathematical modelling of the medium motion, non-stationary Navier–Stokes equations were used. Parameters such as heat, mass transfer, and the efficiency of liquid droplet spraying were determined. The current study presents CAD modelling, conducted in SolidWorks platform, of water distribution on the adiabatic cooling pad’s mesh surface for improving air conditioning equipment performance. This study provides the methodology for computer modeling and numerical calculation of the parameters of adiabatic cooling, such as modelling of water atomization process. The results show that the use of additional metal mesh intended as cooling pads increases the mass transfer coefficient by Sh ≈ 15–40%; heat transfer coefficient Nu increases by ≈20–40%; and the atomization efficiency increases by ≈30–40%. The installation of metal pad mesh allows for equalized uniformity of the water distribution. The results imply that there are more opportunities to optimize the parameters of adiabatic cooling, which should be evaluated in further research on the subject.

Kinetics of low‐temperature catalytic combustion of ethylene at wet conditions for postharvest storage applications

AbstractThe study addresses the reduction of ethylene levels in postharvest storage applications using a selected Pd‐Zn‐Sn/TiO2 catalyst (US Patent 11065579) capable of reacting trace concentrations of ethylene at temperatures as low as 278 K and relative humidity as high as 90%. The rate law is derived from data collected using a constant volume batch reactor, and a model for a storage room with an associated isothermal packed bed reactor is developed. The amount of catalyst required to maintain an ethylene concentration of 0.1 ppmv in a room containing 20 tons of fruit having an ethylene metabolism of 0.1 μl/kg h was calculated as a function of air temperature and water content. While the catalyst can continuously remove ethylene from saturated, refrigerated air, the amount of catalyst required can be reduced significantly by incorporating conventional air conditioning solutions upstream of the catalyst bed. Such combined systems and their functions are discussed.

A hierarchically structured self-cleaning energy-free polymer film for daytime radiative cooling

Radiative cooling without using electricity represents an ideal green solution for air-conditioning. Despite exciting progress made so far, most of the radiative cooling materials are vulnerable to outdoor contamination, which leads to decreased performance. Herein, we fabricate a hierarchically structured PVDF/PDMS porous film which integrates strong sunlight reflectance (97%), high thermal-infrared emittance (96%) and robust superhydrophobicity (160.2°). The synergy of the effective solar reflection and thermal-infrared emission enables the film to yield a sub-ambient temperature drop of 12.3 °C under strong sunlight. More importantly, the superhydrophobicity keeps the film away from contamination by self-cleaning, maintaining well the radiative cooling performance for a long-term outdoor use. Additionally, the as-obtained film shows excellent chemical durability after exposure to different pH solutions and UV light irradiation. This work provides a new strategy to integrate self-cleaning with radiative cooling, showing great potential to advance energy-free cooling materials toward real-world applications.

Development of a three-dimensional numerical model of indirect evaporative cooler incorporating with air dehumidification

Indirect evaporative cooler (IEC) is treated as an energy-efficient and low carbon-emission air conditioning solution without utilizing the mechanical compressor and chemical refrigerants for cooling production. Currently, the widely-used one-dimensional (1-D) and two-dimensional (2-D) numerical models of IEC can expose the temperature and humidity variations of the airflow direction for predicting the cooling performance. However, the air profile along the channel width direction is usually simplified as constant in those models, neglecting the effect of non-uniformity distribution in the normal direction of heat exchanger plates. In this paper, a novel 3-D IEC numerical model of a cross-flow IEC was developed based on the computational fluid dynamics (CFD) method. The judgment on moist air condensation was incorporated in the model by a built-in generalized minimum residual iterative solver, which enables the performance prediction of IEC in hot and humid areas. Detailed air temperature and moisture content distributions along and perpendicular to the air channels were obtained with sufficient validations from published and experimental data. Parameter analysis was conducted on the primary air inlet properties and the channel gap distance. Results show that the prediction accuracies of temperature and humidity were improved by 5.8 and 6.7% compared with the 2-D model. The air dehumidification process started to appear from 27 ℃ given the 70% RHp,in. Under the circumstance of condensation state, the highest wet-bulb efficiency was 0.8 given the 0.5 m/s air velocity against 4 mm optimized gap distance, while the greatest dehumidification rate was 0.3 in the studied ranges. The maximum net energy saving was obtained as 4.7 kW under scorching and wet climate conditions. The proposed 3-D model can benefit future study on the heat and mass transfer mechanism of advanced plate materials by providing the non-uniformity of air profiles along the Y-axis, and thus contribute to the development of next-generation IEC technology.

Direct evaporative cooling from wetted surfaces: Challenges for a clean air conditioning solution

AbstractEvaporative cooling has a major role to play in fighting climate change and in achieving a low‐carbon economy. As it helps to reduce energy demand for air conditioning, it is gaining attention in terms of improving energy efficiency in buildings. Evaporative cooling from wetted media can enhance water–air contact, thereby improving heat and mass transfer further and avoiding aerosols. Wetted media are commonly called evaporative cooling pads and are widely used in greenhouses, intensive livestock farming, and industrial facilities. However, a deep understanding of evaporative cooling pad performance can enhance their application to indoor occupied spaces such as residential or commercial cooling, or in hybrid air conditioning systems. Most studies analyze pad performance mainly in terms of pressure drop and saturation effectiveness. However, some studies propose alternative cooling efficiency parameters and others provide insights into key aspects such as power requirements and the coefficient of performance, water consumption, risk of water entrainment, material decay, and air quality, as well as the effect of water temperature and salinity, solar radiation, or wind speed. Existing results on these less studied performance issues are reviewed, and we identify the gaps in the literature in addition to highlighting the main challenges encountered, in an effort to guide future researchers in the field and enhance the application of direct evaporative cooling.This article is categorized under: Energy Efficiency > Systems and Infrastructure Energy Systems Analysis > Systems and Infrastructure

Dynamic Evaluation of Desiccant Dehumidification Evaporative Cooling Options for Greenhouse Air-Conditioning Application in Multan (Pakistan)

This study provides insights into the feasibility of a desiccant dehumidification-based Maisotsenko cycle evaporative cooling (M-DAC) system for greenhouse air-conditioning application. Conventional cooling techniques include direct evaporative cooling, refrigeration systems, and passive/active ventilation. which are commonly used in Pakistan; however, they are either not feasible due to their energy cost, or they cannot efficiently provide an optimum microclimate depending on the regions, the growing seasons, and the crop being cultivated. The M-DAC system was therefore proposed and evaluated as an alternative solution for air conditioning to achieve optimum levels of vapor pressure deficit (VPD) for greenhouse crop production. The objective of this study was to investigate the thermodynamic performance of the proposed system from the viewpoints of the temperature gradient, relative humidity level, VPD, and dehumidification gradient. Results showed that the standalone desiccant air-conditioning (DAC) system created maximum dehumidification gradient (i.e., 16.8 g/kg) and maximum temperature gradient (i.e., 8.4 °C) at 24.3 g/kg and 38.6 °C ambient air conditions, respectively. The DAC coupled with a heat exchanger (DAC+HX) created a temperature gradient nearly equal to ambient air conditions, which is not in the optimal range for greenhouse growing conditions. Analysis of the M-DAC system showed that a maximum air temperature gradient, i.e., 21.9 °C at 39.2 °C ambient air condition, can be achieved, and is considered optimal for most greenhouse crops. Results were validated with two microclimate models (OptDeg and Cft) by taking into account the optimality of VPD at different growth stages of tomato plants. This study suggests that the M-DAC system is a feasible method to be considered as an efficient solution for greenhouse air-conditioning under the climate conditions of Multan (Pakistan).

Simulation and Analyses of a Novel Air-conditioning Solution for Improving Energy Saving in a Data Room

In view of the feature of long airflow path, high wind resistance, and large area of refrigeration equipment in traditional data room, a new type of under-floor modular air conditioner and its corresponding new air conditioning solution for data room is proposed in this paper. The mathematical and physical model of the new solution for data room is established through a computational fluid simulation software and compared with two mainstream air conditioning solutions. Meanwhile, the impact of these three different air conditioning solutions on the temperature field, airflow field and energy consumption are analysed. The results show that the new type air conditioning solution for data room not only can be used to improve the distribution of temperature and airflow in the data room, but also can greatly reduce the energy consumption of the system.

A comparative study on energy saving and economic efficiency of different cooling terminals based on exergy analysis

The efficiency of air conditioning terminal has become a key factor for energy saving in low energy buildings because the significant reduce of sensible heating and cooling load. This paper presents an investigation for the optimal scheme of air conditioning terminal in ultra-low energy buildings. The exergy method is applied to investigate the energy efficiency and cost-effectiveness potential for the solution of air conditioning terminal in ultra-low energy buildings in hot summer and cold winter region of China. Theoretical model for energy conservation is proposed, and cost equation is used to evaluate economic efficiency. The effects of climate and system parameter on energy efficiency of different air conditioning terminals are also investigated. The results showed that the exergy efficiency and exergy consumption saving rate of radiant cooling terminal resulted in 30% higher than that of fan coil, respectively. The radiant cooling terminal has better adaptability to climate compared with the fan coil. It is crucial for radiant cooling system to increase supply water temperature and decrease the temperature difference because a wide range of naturally available exergy sources can be used. Furthermore, the radiant cooling terminal yields lower exergy unit prices and makes sound economic sense throughout the life cycle than the fan coil. A new approach to evaluate the energy and economic efficiency is introduced and applied to analysis the optimal air conditioning solution for ultra-low energy buildings.

Building occupant transient agent-based model – Movement module

Simulation of occupant behaviour (OB) in buildings is a challenging task. Available software uses a broad spectrum of tools that try to reproduce the patterns of human activity. From building energy perspective, the main emphasis in research has been focused on discovering behaviour directly related to energy. In recent years, more attention has been given to simulating occupant actions that are indirectly influencing building energy use. In most of the cases, this is achieved with the use of agent-based modelling which allows describing occupant actions on a room level. According to the existing methodologies review, it is a proper step, but to include occupant behaviour in energy simulations, spatial and temporal resolution of the occupant behaviour model must be improved. Addressing this issue requires the development of a comprehensive model supported by numerous modules that would cover various significant occupant actions. This paper focuses on the development of the high-resolution, data-driven movement engine of occupants. It is one of the fundamental modules necessary to simulate occupant behaviour with high granularity. Once the model is developed within its essential functionalities, it will deliver a bottom-up model capable of testing various energy use strategies. It will allow for testing different heat, ventilation and air conditioning solutions and the responses provided by simulated occupants. The data used to develop this module was obtained thru in-situ measurements, with the use of depth registration. Information obtained from experiments is similar to previous research, but it also extends the investigation scope with an additional transition-based variable.

Primer energetski efikasnog korišćenja subgeotermalnog resursa za potrebe klimatizacije prodajnog kompleksa

For the air-conditioning of the IKEA sales complex in Belgrade, the exploitation of groundwater, as a subgeothermal resource, was carried out, using a heat pump. The groundwater from a karst aquifer is abstracted by the three drilled wells, the depths of which are 87-103m. Based on the results of the 1-year trial exploitation, in the period August 2017-July 2018, balance reserve of the groundwater is 10.8 l/s, with temperatures in the range 22.0-22.9 0C, which gives the nominal available thermal power of the system of 774 kWt. The applied air-conditioning solution can be assessed as energy efficient, due to the efficiency of the water-water heat pump system, as well as to an environmental contribution, by the substitution of fossil fuels. Preliminary economic analysis shows that total financial investments in the system, compared with the conventional alternative solution, are paid after less than six years.

Membrane Processes for the Regeneration of Liquid Desiccant Solution for Air Conditioning

Regeneration of liquid desiccant solutions is critical for the liquid desiccant air conditioning (LDAC) process. In most LDAC systems, the weak desiccant solution is regenerated using the energy-intensive thermal evaporation method which suffers from desiccant carry-over. Recently, membrane processes have gained increasing interest as a promising method for liquid desiccant solution regeneration. This paper provides a comprehensive review on the applications of membrane processes for regeneration of liquid desiccant solutions. Fundamental knowledge, working principles, and the applications of four key membrane processes (e.g., reverse osmosis (RO), forward osmosis (FO), electrodialysis (ED), and membrane distillation (MD)) are discussed to shed light on their feasibility for liquid desiccant solution regeneration and the associated challenges. RO is effective at preventing desiccant carry-over; however, current RO membranes are not compatible with hypersaline liquid desiccant solutions. FO deploys a concentrated draw solution to overcome the high osmotic pressure of liquid desiccant solutions; hence, it is feasible for their regeneration despite the issues with internal/external concentration polarization and reverse salt flux. ED has proven its technical feasibility for liquid desiccant solution regeneration; nevertheless, more research into the process energy efficiency and the recycling of spent solution are recommended. Finally, as a thermally driven process, MD is capable of regenerating liquid desiccant solutions, but it is adversely affected by the polarization effects associated with the hypersalinity of the solutions. Extensive studies are required to realize the applications of membrane processes for the regeneration of liquid desiccant solutions used for LDAC systems.

Experimental study of the unsteady vibration signature for a Sirocco fan unit

The small forward-curved blades known as Sirocco fan units are very common and widespread solution for air conditioning used in public transportation applications, as buses or trains. The users quietness and comfort have become a main concerns in the automotive industry. For such kind of turbomachinery flow , the patterns becomes always highly 3D and unsteady, compromising the referred comfort, and setting the focus on the working flow variables. A mathematically exact solution for that flow, which would provide any required information on pressure or forces, is out of scope at the current engineering design processes. Nevertheless, some flow features and mechanical data are needed to progress in the frame of a modern industrial environment, involving maintenance protocols with important temporal and economic constraints for different design procedures. The correctness of a given maintenance protocol relies on its feasibility to handle a set of machine working parameters or variables, including a number of them as wide as possible. Doing so, a set of not-dangerous ranges for them can be established. Such ranges are often defined promoting a series of failures similar to real ones, when the machine is in its operative lifetime. In this paper and in order to establish proper working ranges for maintenance purposes, a series of failures have been experimentally tested for a Sirocco fan unit. Initially, real data from industry have been required and a list of main failures was made, including (1) impeller or rotor unbalance, (2) impeller channel obstruction and (3) blocked inlet. The failures are studied using a purified orbit diagram (POD) technique and a symmetrized dot pattern (SDP) technique. All four working conditions are studied for at least three different flow rates and, therefore, a deeper insight into the fan working parameters and options are made feasible. In the frame of the maintenance protocol, a full set of ranges for the considered failures has been obtained. Therefore, the present paper shows a novel possibility to enhance existing maintenance protocol using two advanced frequency-based techniques.

Partial load efficiency analysis of a CCHP plant with RICE and H2O-LiBr absorption chiller

This paper presents a model for calculating and analyzing the global efficiency of a trigeneration system (CCHP) using 3 reciprocating internal combustion engines (RICE) as prime mover for heat and electric loads. RICE operate simultaneously and at the same load. The CCHP plant delivering energy for the office buildings of an economic operator includes also 2 absorption chillers with water-lithium bromide solution for air conditioning. The system has been analyzed for RICE partial load operation mode, linking the thermal energy output to the cooling power generation. The amount of thermal energy production is influenced by the required energy for cooling. The total cooling load in the summer is determined by both the indoor office-rooms cooling load and the data center cooling load (the energy dissipated by the data center’s components and electrical circuits). An vapor-compression chiller is operated for cooling peak load. During yearly thermal load variation, RICE are switched on or off, operate at nominal capacity or in partial load mode. The thermal efficiency of each engine changes according to the demanded heating load, determining the global efficiency variation of the trigeneration system.. The electrical efficiency of the system is also dependent on the RICE operating load that leads the electric generators. The EER factor for the absorption chillers results accordingly at partial or nominal load operating mode. The functioning graphics for each system equipment were developed based on the thermal load curve of the RICEs and the global efficiency variation graph of the trigeneration system was plotted. Finally, conclusions resulted regarding the optimal functioning of the studied trigeneration system.

Study on model of household split air conditioning solution dehumidifier

Liquid desiccant technology in central air conditioning system is very promising, however, rare researchers proposed to carry out it on household liquid desiccant air conditioner. In this paper, a two-dimensional heat and mass transfer theoretical model of cross flow dehumidifier for household split air conditioner has been established, and it is shown that the model established has a good accuracy and the relative error is less than 3.72% by comparing the simulation results with the experimental data in the literature. Based on the model, a series of experiments are conducted and the experiment data is adopted to fit the correlation formula of NTUm and Le. The results show that the model established has a good reaction to the actual situation. Furthermore, the influence of air, solution inlet conditions on the dehumidification performance of the system has been discussed in the paper.

Improvement of variable refrigerant flow system performance using energy saving control strategy and chilled water storage

Variable refrigerant flow system is a popular building air conditioning solution. Modern variable refrigerant flow systems such as multi-functional variable refrigerant flow systems can also provide space cooling, space heating, and water heating to the building simultaneously. The performance improvement of variable refrigerant flow system is a key research topic. In the current article, energy saving potentials of two measures: A new energy saving control strategy and a new variable refrigerant flow system with chilled water storage are theoretically investigated. The energy saving control strategy changed the evaporating temperature based on ambient temperature. The new variable refrigerant flow system utilizes the water storage component in current multi-functional variable refrigerant flow systems as a chilled water storage unit. Simulation is carried out on a validated thermodynamic variable refrigerant flow model in EnergyPlus. The seasonal energy saving potentials of both measures are calculated in four cities: Miami, Houston, Baltimore, and Chicago. The energy saving control strategy can achieve seasonal energy saving as high as 10.8% in cooling season and 15.4% in heating season. The performance of the new system is also compared to baseline variable refrigerant flow system and the seasonal cooling energy saving could reach 12.5%.

State-of-the-art integrated CO2 refrigeration system for supermarkets: A comparative analysis

This paper investigates the integrated and state-of-the art features of CO2 trans-critical booster systems. The main objective is to identify the most promising solutions in terms of energy efficiency impacts.First, the performance of modified features and integrated functions have been compared with the standard CO2 system and alternative heating and air conditioning solutions. Subsequently, the performance of the defined state-of-the-art CO2 system is compared to natural refrigerant-based cascade and HFC/HFO-based DX and indirect refrigeration solutions operating in cold and warm climates.The results indicate that two-stage heat recovery, flooded evaporation, parallel compression and integration of air conditioning are the most promising features of the state-of-the-art integrated CO2 system. This compact and environmentally friendly system is the most energy efficient solution in cold climates, and is also an efficient solution in warm climates, with comparable efficiency to cascade and HFC/HFO DX systems, but with no existing or potential limitations.

Purified orbit diagram and numerical study for a failure analysis of a Sirocco fan

Sirocco fan units are very common and widespread solution for air conditioning used in public transportation applications (buses or trains). The users’ comfort and tranquillity are main concerns in the automotive industry. Inside such turbomachines, the flow structure always becomes highly three dimensional and unsteady, compromising the referred comfort, and sets the focus on the working flow variables. A mathematically exact solution for that flow, which would provide any required information on pressure or forces, is out of scope at the current engineering design processes. Nevertheless, some flow features and mechanical data are needed to progress in the frame of a modern industrial environment, which each time more strongly, besides the different design procedures, involves maintenance protocols. The correctness of a given maintenance protocol relies on its feasibility to handle a set of machine working parameters or variables, including a number of them as wide as possible. Doing so, a set of non-da...