Split Air Conditioner Research Articles

Study on energy-saving design of renewable energy applied to high-rise residential buildings

ABSTRACT Improving building energy systems is a major research hotspot due to the rising demand for indoor comfort and buildings’ increasing energy consumption. The research object in this work is a high-rise residential building in Nanjing. The photovoltaic system and ground source heat pump system are introduced into the traditional cooling and heating source system for energy-saving design of the building. Based on OpenStudio software, two photovoltaic systems, household photovoltaic panels and centralized rooftop photovoltaic panels, are analyzed in terms of dynamic energy efficiency on a time-by-time and day-by-day basis. In addition, the ground source heat pump system is studied in comparison with conventional split air conditioning system. Meanwhile, the energy-saving performance of systems is analyzed during the cooling, heating and transition seasons. The results showed that both PV systems can afford a total of 39.5% of the electricity demand for lighting and equipment systems throughout the year. The total primary energy consumption per unit area of the optimized building model is 51.17 kWh/(m2·a), which is 35.2% lower than that of the original building model. In addition, the energy replacement rate of the photovoltaic system is 23.7% and the contribution of renewable energy from ground source heat pump is 38.76%, which meets the national standard for near-zero energy buildings.

Research on the performance of ultra-low temperature cascade refrigeration system based on low GWP refrigerants

The EU Security Council and Parliament have tentatively agreed to ban fluorinated gases with a global warming potential (GWP) higher than 150 in split air conditioners and heat pumps from 2027. This will further motivate the refrigeration industry to accelerate the search for refrigerants with low GWP and zero ozone depletion potential (ODP). At present, research into low GWP refrigerants for cascade systems is limited, focusing mainly on single refrigerant substitutes without comprehensive comparisons and lax GWP restrictions. In this study, the cascade refrigeration cycle (CRS) system is established to meet the demand of −100 to −50 °C. The GWP of the refrigerants is strictly controlled below 150, and a comprehensive screening of the four generations of refrigerants is carried out to identify refrigerant pairs that meet environmental and refrigeration requirements. The relationship between the high-temperature cycle (HTC) evaporation temperature and the optimal coefficient of performance (COP) is determined, and the effects of the low-temperature cycle (LTC) evaporation temperature Te concerning with mass flow rate, discharge temperature of compressor, compressor power consumption, exergy destruction, and exergy efficiency are analyzed in detail. The thermodynamically superior refrigerant pairs are identified by comparison with several conventional refrigerant pairs. The results show that when Te > −67 °C, R170/R600a is preferred, and when Te ≤ −67 °C, R170/R1270 is preferred. In the temperature range of −100 ∼ −50 °C, R170/R1270 is the better refrigerant pair, which can improve the performance by 6.39–13.11 % than traditional refrigerant pairs. Finally, the exergy destruction analysis of CRS components is carried out, which provides a reference for refrigerant selection and system optimization of CRS in the field of ULT.

A Helmholtz Energy Equation of State for Calculations of Thermodynamic Properties of trans-1,2-Difluoroethene [R-1132(E)]

This work presents a fundamental equation of state for calculations of the thermodynamic properties of R-1132(E), which is a potential refrigerant for residential or mobile air conditioners. The equation of state has a functional form expressed explicitly in the Helmholtz energy with temperature and density as the independent variables, and the form is fitted to consistent experimental datasets, including the critical parameters, vapor pressure, saturated liquid and vapor densities, (p,ρ,T) behavior, vapor-phase sound speed, and ideal gas isobaric heat capacity. The equation of state is valid between temperatures from 240 K and 400 K, with pressures up to 6.5 MPa. In this range, expected relative uncertainties at the 95 % confidence interval (k=2) are 0.1 % for liquid densities, 0.4 % for vapor densities, and 0.1 % for vapor-phase sound speeds, except at the saturation states and in the critical region where larger deviations of up to 2 % are possible in densities due to higher experimental uncertainties. The uncertainty in calculated vapor pressures is 0.15 % above 275 K, which is larger at lower temperatures due to their small values. Various plots of derived properties from the equation of state show that the equation exhibits qualitatively correct behavior over wide ranges of temperature and pressure.

Modeling Supply Air Jet of Split Air Conditioner Based on Abramovich Jet Theory and Bayesian Markov Chain Monte Carlo Algorithm

Aim: This study aims to develop supply air jet models for split air conditioners. Background: Designing and operating an air conditioning system based on the unique characteristics of the supply air jet is essential to control the draft risk. Motivation: Due to the distinct differences in air supply characteristics of the split air conditioners caused by the intermittent operation and the complex design of supply air outlets, the existing supply air jet models designed for central air conditioning systems are unsuitable for split air conditioners. Significant results: In this study, models for the trajectory position, velocity, and temperature of the supply air jet for split air conditioners are established based on the Abramovich jet theory and Bayesian Markov Chain Monte Carlo (MCMC) algorithm. The effectiveness of the proposed models is demonstrated via comparison with the training dataset from the experimentally validated Computational Fluid Dynamics simulation of a split air conditioner. For the model testing dataset, the RMSEs of trajectory position, velocity, and temperature are 0.01 m, 0.09 m/s, and 0.09 °C, respectively, with a low supply air velocity and 0.01 m, 0.25 m/s, and 0.03 °C with a high supply air velocity. The proposed models of velocity and temperature of the supply air jet are general for various supply air conditions, while coefficients in the trajectory position model of the supply air jet need to be recalibrated with the proposed Bayesian MCMC algorithm for different supply air conditions. The proposed models provide valuable guidance for the operation of split air conditioners.

R152a-R13I1 mixture as an alternative to R1234yf for a mobile air conditioning: an estimation of flammability properties, thermodynamic and environmental performance

R152a-R13I1 mixture as an alternative to R1234yf for a mobile air conditioning: an estimation of flammability properties, thermodynamic and environmental performance

SPLIT DUCT AC LEAKAGE MONITORING SYSTEM VIA GOOGLE SHEETS

General Background: Split duct air conditioners are prone to leaks, often resulting from corrosion in water catchment systems, which can lead to significant operational hazards such as electrical fires. Specific Background: Given the prevalence of these issues, there is an urgent need for effective monitoring solutions to maintain optimal air conditioner performance and prevent leaks. Knowledge Gap: Current monitoring systems lack integration with real-time data reporting mechanisms that can alert users promptly to potential issues. Aims: This research aims to develop a monitoring device utilizing NodeMCU ESP8266, water level sensors, and Google Sheets to enable real-time monitoring and management of water levels in split duct air conditioners. Results: The device successfully operates by turning on the fan when water levels are below 2 cm and activating the pump when levels exceed this threshold. The data is continuously sent to Google Sheets, allowing for easy monitoring and management. Novelty: This study presents a novel approach to air conditioner leak monitoring by integrating IoT technology, offering an efficient and user-friendly solution for residents. Implications: The developed monitoring tool significantly enhances the ability to detect and manage potential leaks in real time, thereby improving safety and operational efficiency. Future research should focus on enhancing sensor accuracy through specialized equipment and exploring alternative IoT platforms for improved data visualization, thereby providing users with an even more effective monitoring experience.

Numerical Investigation of Bionic Axial Fan used in Split Air Conditioner

Abstract: Bionic axial fan is the main component in the outdoor unit split type room air-conditioner (AC) which impact the cooling and comfort. The present work aims to improve the aerodynamic performances of bionic axial fan by numerical technique. The detailed simulation has been carried out to investigate the aerodynamic performance of bionic axial fan with various design proposals for a detailed investigation and development of a prospective fan design prior to the manufacture and testing of costly prototypes. According to the biological fact that the serrations at the wing improve the acoustics as well the aerodynamic performances, various design modifications performed on the bionic axial fan blade. As the serrations at the trailing edge help to improve the aerodynamic performance, the fan blade design modified to investigate the change in mass flow rate. The flow field is simulated with the finite element Computational Fluid Dynamics (CFD) solver Altair-AcuSolve to analyse the influence of trailing edge serrations on the air flow rate of fan. The three-dimensional (3D) computational domain with SpalartAllmaras (SA) turbulence model is considered to predict the air flow rate. The present computation is carried out for the axial fan speed of 820 rpm. The flow rate is correlated with the test results to validate the CFD modeling approach. The result shows that the trailing edge serrations at the tip of the fan has predicted improvement in flow rate since it alter the length of separation bubble near the trailing edge which also helps to reduce the noise level.

Research on the coordinate regulation behavior of window opening and split air conditioners usage during summer in mixed-cooling houses in hot-humid regions

In the hot-humid regions of South China, it is common for residents to utilize a combination of window opening and split air conditioners to cool their houses during summer. However, existing research focuses on investigating either window opening behavior or air conditioner usage behavior respectively, lacking a linkage study between these two approaches. Addressing this research gap, a novel coordinated regulation behavior model was developed by integrating both window opening and air conditioner usage behaviors. Due to different coordinate regulation modes, the tolerance temperature range in summer varies in mixed-cooling houses. Additionally, a degree of coordination is introduced to signify the level of overlap between window opening and air conditioner usage behaviors, indicating the uncertainty involved in choosing between these two actions. Moreover, residents exhibit a dynamic approach to switching between cooling methods, characterized by a transition range of approximately 2 °C rather than relying on a fixed temperature value. Notably, the simulated energy consumption results demonstrate a significant energy consumption disparity of up to 71 % among different behavior patterns. This study contributes to the academic understanding of the complex interactions between window opening and air conditioner usage and lays the foundation for achieving precise energy consumption simulation of mixed-cooling houses.

An experimental study on the effect of room setpoint temperature, and evaporator/condenser fouling on performance of a ductless split type air conditioner

Ductless splits can have several advantages over conventional systems including energy saving, improved thermal comfort, and performance. A deep understanding of the effect of changes in operating conditions of the unit is required to estimate the energy saving in the field. In this paper, a reference guide is created to classify the effects of different parameters on the performance of the ductless split unit. The experiments are categorized into three main topics: 1- The effect of setpoint temperature on the performance and energy consumption, 2- The effect of evaporator fouling on energy consumption, and 3- The effect of condenser fouling on energy consumption of a ductless split unit. Results show that one degree Celsius increment in room setpoint temperature reduces power consumption approximately 57 W and in annually energy consumption about 279 kWh. Furthermore, covering 30 % of the evaporator coil surface area and comparing with the normal case (evaporator coil with no coverage), parameters of Energy Efficiency Ratio, energy consumption, and cooling capacity drops 13.5 %, 6.4 % and 19.1 %, respectively. Likewise, by covering 1/3 of the condenser coil surface area and comparing with the normal case, Energy Efficiency Ratio, and cooling capacity drops 9.8 % and 2.4 %, respectively. The mentioned data indicate that the effect of the evaporator dirtiness on reducing the cooling load of the device is much higher than that of condenser.

A case study on optimizing industrial air conditioning with thermal solar energy in Egypt

This study investigates the feasibility of implementing a solar-assisted adsorption chiller in an industrial building at the Oriental Weavers International factory located in 10th of Ramadan City, Cairo, Egypt. The objective is to replace an inefficient split air conditioning system currently used to cool the Jacquard units during carpet manufacturing. The research begins by analyzing the performance of the existing cooling system to establish a baseline. It then explores the potential energy savings achievable by replacing the current system with a solar-assisted adsorption chiller. The existing oversized boiler will serve as an auxiliary heater for the new system. TRNSYS simulation tools are employed to model the building, simulate its thermal performance, and develop a solar-assisted cooling system. A parametric analysis investigates the impact of varying collector area and hot/cold-water storage tank volumes on key energy performance indicators. This analysis aims to determine the optimal component sizes needed for efficient system operation. Results indicate that a collector area of 90 m2 offers the optimal balance between performance and cost. There are minimal benefits to increasing the collector area beyond 100 m2. Larger hot water storage tanks demonstrate reduced outlet temperatures, reaching a maximum solar fraction at a capacity of 4 m³. The impact of cold-water storage tank volume on the system is minimal. The economic assessment reveals a payback period of 7.6 years, an Internal Rate of Return (IRR) of 14.3 %, and a Return on Investment (ROI) of 34.5 % over a 10-year period, indicating the financial viability of the proposed system. Furthermore, the solar-assisted adsorption chiller system has the potential for substantial environmental benefits. The system has the capacity to reduce CO2 emissions by up to 7200 metric tons. This highlights not only the technical feasibility of the system but also its economic and environmental advantages.

Corrective Evaluation of Response Capabilities of Flexible Demand-Side Resources Considering Communication Delay in Smart Grids

With the gradual increase in the proportion of new energy sources in the power grid, there is an urgent need for more flexible resources to participate in short-term regulation. The impact of communication network channel quality will continue to magnify, and factors such as communication latency may directly affect the efficiency and effectiveness of resource regulation. In this context of a large number of flexible demand-side resources accessing the grid, this article proposes a bidirectional channel delay measurement method based on MQTT (Message Queuing Telemetry Transport). It can effectively evaluate the real-time performance of communication links, considering that resources mainly access the grid through the public network. Subsequently, focusing on two typical types of resources on the demand side, namely, split air conditioners and central air conditioners, this article proposes an assessment method for correcting the response capabilities of air conditioning resources considering communication latency. Experimental simulations are conducted, and the results demonstrate that under given communication conditions, this method can more accurately estimate the response capability of air conditioners. This provides a basis for formulating more reasonable scheduling strategies, avoiding excessive or insufficient resource regulation caused by communication issues, and aiding the power grid in achieving precise scheduling.

Refrigerant Selection in Air Conditioning Systems Considering Thermodynamic, Environmental, and Economic Performance Using the BHARAT-II Multi-Attribute Decision-Making Method

A simple and effective multi-attribute decision-making method, named as "Best Holistic Adaptable Ranking of Attributes Technique (BHARAT)-II”, to choose the best refrigerant for air conditioning systems is presented. The thermodynamic properties of the refrigerants, and their environmental, and economic performances are also considered for the selection. Two case studies are provided to demonstrate the proposed multi-attribute decision-making method. The first case study addresses the problem of selecting the best refrigerant for residential split air conditioners out of 15 alternative refrigerants considering 12 selection attributes; the second case study addresses the problem of selecting the best refrigerant for automobile air conditioning systems by considering 14 alternative refrigerants and 13 selection attributes. The results of the proposed decision-making method are compared with those of other well-known multi-attribute decision-making methods such as EDAS, TOPSIS, and MOORA. The proposed method is shown to be simple to implement, providing a logical way for allocating weights to the selection attributes and is useful to solve the best alternative refrigerant selection problems of the residential as well as industrial refrigeration and air conditioning.

Heavy metals and microbial assessment of air conditioning condensate water in Jeddah city-Saudi Arabia: concept of sustainable water resources

The demand for water is rising worldwide, especially in Saudi Arabia, where the existing water sources are barely sufficient to meet the present requirements. Condensates from air-conditioning units can be invested as an economical and supportive source of available water resources, which can be considered within global water supply accounts. The aim of the present study is to examine the possibility of recovering condensate water from air conditioner (AC) systems by determining the quantity and quality of AC water generated by either split or window AC systems. The results showed that split air conditioner systems were more effective than window-type air conditioners in generating condensate water in terms of quantity and quality. There was a significant correlation between the humidity and water content. The results indicate that the annual amount of water generated was 8,725 L for window AC and 20,614 L for split AC. The recorded levels of all elements in the water samples obtained from both the window and split air conditioning units, including pH, TDS, EC, PO4-3, Cl-, SO4-2, COD, and heavy metals, were found to be within the acceptable thresholds set for both drinking water and irrigation purposes. Bacteria were only present in three water samples from the window AC, and all were non-pathogenic. Utilizing air conditioner condensate as a strategic measure can address the issue of water scarcity in Saudi Arabia’s agricultural and industrial sectors. The findings of this study are extremely relevant and opportune, especially given the growing concerns about water scarcity and the need to conserve resources. By demonstrating that the HVAC water condensate is clean and safe for consumption, this study adds to our understanding of how we can make better use of available resources.

DECREASING ELECTRICAL ENERGY COST AND INDIRECT CO2 EMISSIONS OF AN AIR CONDITIONING UNIT AFTER PREVENTIVE MAINTENANCE

During the summer season in subtropical countries and the dry season in tropical countries, air temperature is high. To adapt this condition, an air conditioning (AC) unit is used. The air conditioning use, however, increases the electrical energy consumption which contributes to the increase of indirect CO2 emissions. For many buildings, a monthly electrical energy cost from the use of AC system can contribute up to 40% of a monthly utility expenditure. It is then a great motivation to decrease electrical energy consumption of the AC unit. In this work, an adaptable preventive maintenance for an AC unit shows an acceptable level of electrical energy decrease. An experiment was performed for 2 AC types. The first one is a wall mounted unit with a cooling capacity of 9,300 BTUH. The second unit is a split duct unit with a cooling capacity of 48,000 BTUH. The cleaning of evaporator in the wall-mounted AC unit decreased the hourly electrical energy consumption by 4.1% from 810 to 777 Watt-hour. In addition, cleaning of condenser for the similar AC unit decreased the electrical energy consumption by 6.2% from 810 to 760 Watt-hour. Meanwhile, the evaporator cleaning for a 48,000 split duct AC decreased the hourly electrical energy consumption by 2.4% from 4.64 to 4.53 kWh and cleaning of condenser decreased the energy consumption by 5.4% from 4.64 to 4.39 kWh. If this electrical energy decrease could be scaled up to the global energy consumption from the air conditioning use, this should be a significant decrease of the global energy consumption and the correlated indirect CO2 emissions from the air conditioning sector.

ინოვაციური კონსტრუქციის მობილური კონდიციონერი

Mobile air conditioner is a portable device that is used to cool the air in rooms where it is not possible to install an air conditioner. It can be used in apartments, offices, hotel rooms, camps and other places. The basic principle of operation of mobile air conditioner is to take air from the air-conditioned room through the built-in fan, then the air passes through the filters and is cooled or heated in the built-in evaporator. The processed air is supplied back to the room through a flexible duct. One of the main advantages of mobile air conditioner is its portability. It can be easily moved from one room to another, and such air conditioner can also be taken to any address. Mobile air conditioner does not require complex installation and can be connected to a regular mains electricity supply. In addition, some mobile air conditioners may have a heating function during the cold season. However, mobile air conditioner has some disadvantages. It is usually not as efficient as air conditioner that requires installation (such as split type air conditioners), especially, in large rooms. It can also be noisy and take huge space in a room. It consumes more energy than built-in air conditioners, which can lead to higher electricity bills.

Heating and cooling challenges for electric vehicles: A comprehensive experimental study

An efficient mobile air conditioning (MAC) system using a safe and climate-friendly refrigerant is necessary for human comfort, increasing the vehicle’s energy performance, and reducing the fuel/electricity consumption. In the current work, we perform a drop-in experimental comparison for low GWP alternatives to R134a in reversible MAC systems. The study compares two lower global warming potential (GWP) refrigerants; R456A, a non-flammable refrigerant for R134a direct MAC replacement, and R1234yf, an ultra-low GWP and mildly flammable refrigerant that is the standard for new MAC systems. The system’s operational and energy performance is investigated, simulating a wide range of indoor and outdoor steady-state conditions. The measurements are recorded operating a fully monitored vapour compression test rig that uses secondary circuits to set the target conditions. In the heating mode (heat pump), the evaporation temperatures are set at −10 °C, −5 °C, and 0 °C, and condensation temperatures at 40 °C, 50 °C, and 60 °C. In cooling mode (air conditioning), the condensation temperatures are 37.5 °C, 45 °C, and 52.5 °C and are combined with evaporation temperatures of −7.5 °C, 0 °C, and 7.5 °C. In the heating mode, R456A presented a competitive COP to R134a with a reduction of less than 5 %, more remarkable at lower evaporation temperatures. In the cooling mode, R456A showed the lowest COP at a low condensation temperature. R456A and R1234yf COP are comparable at a higher condensation temperature, which suits the T3 climate conditions.

Comparative analysis of energy efficiency for three heating and cooling supply schemes in a region with hot summers and cold winters in a chemical industrial park

Building energy consumption in China accounts for 45% of the total national energy consumption, with air conditioning energy consumption representing approximately two-thirds of that. Therefore, energy efficiency in buildings is of utmost importance. This study focuses on a chemical industrial park located along the Fujiang River and compares three heating and cooling supply schemes: the river water source heat pump system, which utilizes river water as the heat source and heat sink; the water cooling unit and boiler system, which uses water-cooled electric compression chillers for cooling and an oil-fired boiler system for heating; and the split air conditioning and gas water heater scheme, which relies on refrigerants such as fluorine-containing compounds for cooling and a gas water heater for heating. By calculating the energy consumption of the above three schemes and conducting a comparative analysis, it is found that the river water source heat pump system exhibits significantly higher energy efficiency throughout the year compared to the water cooling unit and boiler system and the split air conditioning and gas water heater scheme. This highlights the notable energy efficiency advantage of the river water source heat pump system.

Experimental and Theoretical Assessment of Inverter-Operated Split Air Conditioner with Low GWP Alternative Refrigerants

This article presents experimental evaluation and comparative analysis of low GWP alternative refrigerants, namely HC-290 (propane), HC-1270 (propylene), HC/HC-1270 blend, and HFC-32 (difluoro methane) as drop-in replacements for HCFC-22 (Chloro difluoro methane) in a typical 1.5 TR capacity inverter operated split type air conditioner (SAC). The experimental setup consisted of retrofitting an original HCFC-22 test unit following the soft optimization of the SAC system for each alternative refrigerant, followed by testing under controlled operating conditions as per the IS 1391, Part-1 standard at the half capacity and the rated capacity of inverter SAC. The results obtained were compared against the baseline HCFC-22 test unit. The optimized SAC gave EERIS (Indian Seasonal Energy Efficiency Ratio) of 4.63 for HC-290, 4.71 for HC-1270 and 4.87 for HC-290/HC-1270 blend, respectively increased by 8.94 %, 10.82 % and 14.58 % compared to HCFC-22. HFC-32 delivered the maximum cooling capacity of 6.78 kW, 3.67 % higher than baseline unit at the rated capacity. HC-290/HC-1270 blend exhibited the lowest power consumption and discharge temperature amongst all the refrigerants considered. The charge of flammable refrigerants has been optimized below LFL satisfying EN378 standard for the safety of inverter SAC in domestic applications.

Experimental study of an on-grid hybrid solar air conditioner with evaporative pre-cooling of condenser inlet air

This paper presents an experimental study of a split type solar air conditioning system with evaporative pre-cooling at the condenser. The main objective of this research is to evaluate the thermal and electrical performance of the system under hot summer conditions in a Mediterranean climate. Previous studies have separately shown the benefits of both condenser inlet air pre-cooling and photovoltaic solar cooling. The novelty of this work will be the study of the coupling of these two techniques in a real installation, where the viability of the system depends on the component-level design and the operating conditions, since weather variables such as ambient temperature, relative humidity and solar radiation significantly affect the thermal behaviour of the refrigeration cycle, the evaporative pre-cooling capacity and the performance of the photovoltaic panels. Experimental tests were carried out over a summer season to evaluate the behaviour of the system and to obtain performance correlations validated with experimental data. These correlations will allow the modelling of the system and will be used to carry out an economic and environmental feasibility study of the proposed hybrid solar air conditioning system. The results show that a 100mm-thick evaporative pad achieved an average evaporative cooling efficiency for all tests performed of ɛevap=67.4%, reducing the air inlet temperature to the condenser by around 6°C. This resulted in an 18.3% improvement in the EER of the air conditioner. In addition, the use of evaporative pre-cooling resulted in a significant 23% reduction in peak power consumption. The study also evaluated the impact of the air pressure drop caused by the evaporative pad when not in use, with results favouring its installation. The system achieved a solar contribution of more than 30% under different solar radiation conditions when using pre-cooling, compared to 25% with a standard condenser. In addition, the combination of photovoltaic contribution and evaporative pre-cooling reduced energy consumption by 43%.

Grey-box modeling for thermal dynamics of buildings under the presence of unmeasured internal heat gains

An accurate grey-box building thermal model is an essential component for prediction-based control of split air conditioners. As the thermal performance of building envelope improves, the internal heat gains play an increasingly noteworthy influence on the building’s thermal dynamics. However, the internal heat gains are usually not measured, which makes the conventional data-dependent identification methods of building thermal models fail. To improve the accuracy of building thermal models under unmeasured internal heat gains, a two-step parameter identification framework for resistance–capacitance (RC) models is proposed in this paper. First, the time-invariant building model parameters are estimated by designing a novel optimization objective function. Next, the time-varying internal heat gains are identified based on the mismatch in predictions of the estimated building model from the first step and the measured temperature. The effectiveness of the method is evaluated using data from a simulation case and an experiment case. The results show that the proposed method outperforms the conventional identification method as well as two other identification methods that handle the unmeasured internal heat gains. Besides, the internal heat gains estimated by the proposed method can capture the trend of the actual internal loads well.