Split Air Conditioner Research Articles

Development, calibration, and validation of a novel gray-box energy model for residential split air conditioners

Energy models for vapor compression refrigeration in residential air conditioners have been developed through white-box, gray-box, and black-box methods in decades. However, existing white-box and gray-box models require complicated equations with detailed geometries while black-box models require substantial experimental data. This paper aims to develop and validate a simple gray-box steady-state energy model without the need for detailed geometries, which can accurately predict the cooling capacity and electrical power input based on outdoor and indoor air conditions, and supply airflow rates. First three state variables, including the evaporation and condensation temperatures, and refrigerant mass flowrate, are applied to develop the energy model and are solved by three physical equations, including the energy conservations at the evaporator and condenser, and the refrigerant volume-mass flow correlation of the compressor. Secondly, seven performance property functions related to three state variables and three physical equations are identified and calibrated by simple temperature and power measurements. Finally, field experiments are conducted on a residential air conditioner to calibrate these performance property functions and validate the developed model. The validated results reveal the model can accurately predict the cooling capacity and electrical power input, with the normalized root mean square errors of 2.3% and 0.87% respectively.

Performance Analysis of Using Hydrocarbon Mixed Refrigerant R32-R290 as an Alternative to R410A in Reducing the GWP Value of Household Split Air Conditioners

An experiment conducted on the mixed refrigerant R32-R290, which is used in household air conditioners, is aimed at reducing the global warming potential and improving the environmental CO2 quality. This mixed refrigerant has a lower GWP and density than the refrigerant R410A. This research was conducted to determine the effect of the increased mass charge of R290 as a mixed refrigerant on the performance of split air conditioner. Three percentage compositions of 20%/80%, 25%/75%, and 30%/70% were applied as a change to R410A in household air conditioners. For the testing equipment condition, the air inlet evaporator and condenser temperatures were 17°C (300 K) and 35°C (308 K), respectively. In the first performance test, refrigerant mass charge of 100% (340 g) was employed. In the second test, mass charge of 40% (136 g), 50% (170 g), and 60% (204 g) were utilized for mixed refrigerant R32-R290. Compared to the performance of R410A, the experimental results for the mixed refrigerant indicated a 0.5% increase in the air outlet evaporator temperature, a 1% decrease in the air condenser outlet, a 29.7% increase in the average COP, a 12.9% decrease in the electrical power consumption from 545.12 W to 474.7 W, a 9.1% increase in the average exergy destruction average from 401.5 W to 441.6 W, and a 19.7% increase in the average exergy efficiency from 24.2 W to 30.1 W.

Can air handling equipment be beneficial to children’s health? Results from a cross-sectional survey in 2010 and 2019 in China

A growing number of studies have shown that the indoor residential environment is associated with respiratory and allergic diseases in children. This study aimed to investigate the prevalence of respiratory and allergic diseases among children in China and its correlation with using air handling equipment, based on the cross-sectional survey results of the China Children Homes Health Project in 2010 and 2019. The binary logistic regression model was used to explore the association between asthma, rhinitis, eczema and pneumonia and the use of air handling equipment in children. The prevalence of children’s respiratory and allergic diseases has decreased, and the usage rate of portable air purifiers and split air conditioners has increased in 2019 compared to 2010. The results showed that using a fresh air system with filters was negatively correlated with children’s pneumonia (adjusted odds ratio (aOR): 0.767, 95% confidence interval (95% CI): 0.704–0.835). The use of portable air purifiers was positively correlated with most diseases’ symptoms in two undertaken surveys. In 2019, the positive correlation between using split air conditioners and asthma-related symptoms decreased compared with 2010, while it was positively correlated with rhinitis, eczema and pneumonia. To avoid children’s allergic diseases and reduce respiratory symptoms, parents should choose appropriate air handling equipment.

Ways to use refrigerators that use heat to cool vehicles.

BACKGROUND: Today, most of the heat that is released during the combustion of fuel in internal combustion engines goes into the environment along with exhaust gases. However, additional energy can be used for refrigeration and air conditioning. Previously, there were only two ways to use exhaust heat for cooling: absorption machines and ejector chillers. But now, thanks to the development of organic Rankine cycles, there are new possibilities for cooling vehicles.
 AIMS: Conduct a theoretical analysis of the possibility of introducing mobile air conditioning and refrigeration systems in transport using various types of refrigeration machines that operate on the basis of heat.
 MATERIALS AND METHODS: Modeling of typical cooling cycles was carried out in the ASPEN HYSYS software environment. The most effective substances were selected from the absence of supercritical conditions.
 RESULTS: Depending on the selected cycle type, simulation results were obtained that corresponded to the calculated parameters. The coefficients of performance were determined under various ambient conditions and generator temperatures.
 CONCLUSIONS: A theoretical analysis of various cooling cycles for use in transport has been carried out. The results of the calculations show that the task of ensuring the cooling of the cabin or cargo is carried out even in the harsh operating conditions of the refrigeration system.

Experimental study on startup characteristics of R290 air conditioner with low lubricant charge

As an A3 refrigerant, the charge of the natural refrigerant R290 in the refrigeration system is limited. The use of partially miscible lubricants and a reduction of the lubricant charge can effectively decrease the refrigerant charge. These two measures affect the startup dynamic characteristics of the compressor and the air conditioner. In this paper, variations in system temperature, pressure, and oil sump parameters during the cold startup process of a 1.5P R290 split inverter room air conditioner with different charges of PAG VG40 were experimentally measured under the rated cooling and low-temperature heating condition. The experimental results showed that the viscosity of the refrigerant/lubricant mixture of low lubricant charge (LLC) was lower than that of the normal lubricant charge (NLC), and the duration of low viscosity with LLC was longer. The low viscosity during startup is mainly due to the insufficient amount of lubricant in the oil sump. Three measures were proposed to alleviate the problem of low startup viscosity. Among them, the modification of the bearing cover effectively improved the viscosity of the LLC mixture, and the minimum viscosity of the bearing cover with LLC was even higher than that of the prototype with NLC. Furthermore, the bearing cover modification allows using a lower viscosity grade of lubricant for R290 rotary compressors.

Experimental evaluation of split air conditioning performance using nanodiamonds particles in compressor polyester lubricant oil

Rationing energy consumption in air conditioning (AC) systems has become increasingly necessary due to the continuous global increase in energy demand and the prevailing sustainability vision worldwide. Therefore, an AC system utilizing nanodiamond/Polyester (ND/POE) lubricant oil, which shows potential to improve the performance and reduce energy consumption, was investigated. Consequently, a 5-ton refrigeration split AC unit was modified with an oil separator to assess the ND/POE nanolubricant in the compressor’s loop, in particularly. The AC unit was examined under various operating conditions up to an extreme high ambient temperature of 52˚C, with an optimal nanolubricant concentration of 0.1% as recommended from the literature, using a fully automated psychrometric testing facility. The results showed that using ND/POE instead of pure POE resulted in a 4.7% and 3% reduction in compressor discharge temperature and pressure, respectively. Furthermore, the overall system's coefficient of performance (COP) improved by up to 8% due to a reduction in power consumption of up to 3% and an increase in cooling capacity of up to 6%. Therefore, it is anticipated that the use of ND/POE will result in improved compressor durability, reliability, and longevity, as well as a significant improvement in the performance of AC systems operating for prolonged periods, such as those operating in extreme high ambient temperature applications.

Experimental investigation on the cooling performance of direct and secondary loop CO2 air conditioning systems for electric vehicles

As a natural refrigerant, CO2 is considered one of next generation refrigerants of electric vehicle (EV) applications for excellent environmental and heating performance. The integration and safety performance of CO2 systems could be enhanced by secondary loop configuration, which is highly valuable for practical applications. This paper investigates the cooling performance characteristics of direct (DAC) and secondary loop (SLAC) transcritical CO2 air conditioning systems based on liquid cooled gas coolers (LCGC). A series of steady-state experiments were carried out for both systems to study the effects of compressor speed, EXV opening, outdoor air velocity, and indoor air flow rate on the cooling performances. Furthermore, the exergy destruction of each component and the exergy efficiency of both systems were analyzed based on the experimental results, showing that the evaporator needs to be better designed to balance heat transfer performance with pressure loss performance. The results showed that the cooling capacity and COP of SLAC system were reduced by up to 9.1% and 10.8% under the same compressor speed, compared with the DAC system. This study presents experimental references for further research and practical extension of the CO2 mobile air conditioner.

Integrating the living wall with the split air conditioner towards indoor heating environment improvement in winter

Employing split air conditioners (SAC) for indoor heating is common, but the poor air quality usually occurs due to lack of fresh air and low relative humidity in winter. The indoor living wall (ILW) has become a reasonable option to refine the indoor heating environment through their purification and photosynthesis. To improve the heating environment, ILW were integrated with the SAC. The system integrating the ILW with the SAC (ILW-SAC) was installed in a common room with referring to the other identical room only having the SAC. The indoor thermal environment and CO2 concentration were tested, while the 72 participants were invited to demonstrate their feelings by using skin temperature measurements. The results showed that ILW-SAC significantly improved the indoor environment by increasing relative humidity by 10.8%, controlling air speed between 0.2 m/s and 0.3 m/s, and reducing CO2 concentration by 49 ppm. ILW-SAC lowered the mean skin temperature by 0.4 °C and let the mean skin temperature closer to the neutral value. ILW-SAC was found to improve the overall freshness sensation and thermal comfort level by about 1.32 and 1.10 respectively. By employing ILW-SAC, the indoor thermal environment and air quality are refined significantly in winter.

Energy consumption of mobile air-conditioning systems in electrified vehicles under different ambient temperatures

In 2019, passenger car CO2 emissions peaked at 3.2 billion metric tons globally. Despite efforts to curb vehicle CO2 emissions and the ambitious targets adopted for greenhouse gas mitigation in the European Union (EU), emissions from road vehicles increased steadily over the past decade. Electrified vehicles have gained significant market share in the last years and are an essential technical option to reduce CO2 emissions. Range anxiety and insufficient charging infrastructure limit electrified vehicles’ customer acceptance and market attractiveness. The use of auxiliary systems under certain circumstances may reduce vehicle range. In this regard, energy management improvements lead to better vehicle range results. As well-considered in numerous studies, the most consuming auxiliary system is the vehicle’s heating, ventilation and air-conditioning (HVAC) system, also known as Mobile Air-Conditioning (MAC). The present work explores the influence of different parameters on the energy consumption of the MAC system in plug-in hybrid vehicles (PHEV) and battery electric vehicles (BEV). For this purpose, one PHEV and one BEV were tested in laboratory conditions at different cell temperatures of −7°C (19.4°F), 22°C (71.6°F) and 35°C (95°F), over the Worldwide Harmonised Light vehicle Test Cycle (WLTC). Laboratory tests with the same conditions were repeated with MAC on and off for each temperature. For the reference 23°C (73.4°F) condition, additional factors affecting energy consumption were analysed, such as the impact of depleting/sustaining modes on the MAC performance in PHEV, or the effect of warm and cold start in PHEV and BEV. Results suggest that the electric energy required to heat the cabin at low temperature (−7°C) could be 4–10 times higher than the energy needed to cool down the cabin in hot conditions (35°C). Compared to the vehicle energy required at the wheels during a WLTC, the MAC impact at −7°C ranges from 35% to 45% while at 35°C goes from 15% to 18%.

Performance Evaluation of Small Scale Air-Conditioning System Using R22 and Alternative Refrigerants

A mathematical model has been formulated to predict the influence of high outdoor air temperature on the performance of small scale air - conditioning system using R22 and alternative refrigerants R290, R407C, R410A. All refrigerants were investigated in the cooling mode operation. The mathematical model results have been validated with experimental data extracted from split type air conditioner of 2 TR capacity. This entailed the construction of an experimental test rig which consists of four main parts. They are, the refrigeration system, psychrometric test facility, measuring instrumentation, and auxiliary systems. The conditioned air was maintained at 25 0C dry bulb and 19 0C wet bulb for all tests. The outdoor ambient air temperature was varied from 35 0C to 55 0C in 5 0C increments. The study showed that R290 is the better replacement for R22 when the air conditioning system works under high ambient temperature. It has better performance as a drop in refrigerant. R407C has the closest performance to R22, followed by R410A.

Life cycle climate performance evaluation of electric vehicle thermal management system under Chinese climate and driving condition

Electric vehicles have become an effective alternative to traditional fuel vehicles due to their environmental friendship and energy security. Unlike mobile air conditioning, electric vehicle thermal management systems are responsible for the temperature of both the cabin and the electrical system. This paper discusses how the life cycle climate performance of a thermal management system can be evaluated to reflect its environmental performance and guide the direction of development. The GREEN-EVTM-LCCP model is developed to assess greenhouse gas emissions over the life cycle of the EVTM systems and to standardize the calculation of energy consumption based on vehicle end-of-life mileage. For efficient management and wide temperature coverage, the Amesim simulation platform is centered on refrigerant injection heat pump systems. The results show that urban climate has the greatest impact on the greenhouse gas emissions of thermal management systems at 54.80% in China, followed by refrigerant type, energy efficiency, and driving conditions. Under typical Chinese climate and driving conditions, the thermal management system has a life cycle equivalent emission of 18,664 kg. The use of more environmentally friendly refrigerants and improved system cycle efficiency is now effective measures to reduce greenhouse gas emissions.

Atmospheric Observation and Emission of HFC-134a in China and Its Four Cities.

1,1,1,2-Tetrafluoroethane (HFC-134a) is widely used as a refrigerant to replace dichlorodifluoromethane (CFC-12), and a small amount of it is used in the foam and medical aerosol sectors, with a high global warming potential and fast-increasing atmospheric concentration. The emission of HFC-134a in China has been growing at an average annual growth rate of 14.4% since 2009, reaching 53.0 (47.5-58.7) kt yr-1 in 2020. Among the five emission sources, emissions from the mobile air conditioning (MAC) sector accounted for the highest proportion of 65% on average of the total, followed by the commercial air conditioning (CAC) sector (25%), the medical aerosols sector (8%), the foam sector (2%), and leakage emission from the production (less than 0.1%). The emissions of HFC-134a in four cities in China (Beijing, Guangzhou, Hangzhou, and Lanzhou) were also estimated and discussed. Beijing had the highest HFC-134a emission of 2.2 kt yr-1 in 2020, and Lanzhou had the lowest emission of only 0.2 kt yr-1. In Beijing and Guangzhou, emissions from the CAC sector surpassed those from the MAC sector, becoming the most important source of HFC-134a. The average annual growth rate of HFC-134a's emissions during 2009-2019 was close to its concentration enhancement growth rate of 12.7%, and the emissions also showed significant correlations with the concentration enhancements in both China and four cities. This indicates the importance of the muti-city and long-term observations for the verification of HFC-134a's emission estimates at a regional scale.

Improving the Efficiency of a Conventional Vapor-Compression Refrigeration System used for Geothermal and Evaporative Cooling Techniques: Case Study in Iraq

A conventional vapor compression refrigeration cycle is among the most effective technology in refrigeration systems. In the present experimental study, thermal performance and the effect of the condenser temperature have been analyzed. With the decrease in the condenser temperature, the overall performance of the refrigeration cycle is increased. However, the cooling power and efficiency of conventional vapor pressure air conditioning units can experience a significant reduction when operating in extreme weather (hot and dry). This drop is mainly affected by the increase in the temperature (and pressure) of the condenser with an increase in the ambient air temperature. Unfortunately, Iraq experiences the most extreme summer seasons especially in the months of June and July when the temperature reaches or exceeds 50° C. So, ground cooling has been used in areas with a hot environment for split system air conditioners. Evaporative cooling was also performed to lower the coolant temperature of the AC unit used inside the condenser area. Experimental results showed that when using a geothermal heat exchanger, the temperature of the condenser is reduced from 116 to 110 ° C and the coefficient of performance (COP) is improved by 41%. In addition to this when the system uses evaporative cooling the temperature of the condenser is reduced from 110 ° C to 88° C. Moreover, a 65% improvement was made in the COP of the conventional vapor compression refrigeration cycle. Furthermore, with a decrease in the evaporator temperature from 6 to 3.5 °C there was an increase in refrigeration capacity by an average of 52%.

Evaluation of Serpentine-Type Heat Exchanger Application on Water Heater with Passages Number Variation

For some people, using warm water for bathing needs is a tertiary need because getting warm water requires additional costs. Generally, people/industry use water heaters that are sold in the market. These water heaters generally use electricity, solar power, or natural gas. This study aimed to evaluate the use of heat recovery systems as water heaters with variations in the number of passages. This research is an experimental study on a serpentine-type heat exchanger. Tests were carried out on standard split air conditioners and split air conditioners integrated with heat exchangers. The independent variables in this study were variations of the heat exchanger type serpentine with a length of 4 m, with each heat exchanger having a height of 20, 25, and 30 cm, with variations of 10, 12, and 14 passages and variations of evaporator output air settings 16ºC, 20ºC and 24ºC. The use of the evaporator outlet air temperature setting produces a different refrigeration effect value. The lower the evaporator output air temperature setting, the lower the resulting refrigeration effect value. The air temperature leaving the evaporator is 24ºC which results in a higher refrigeration effect value. This study showed the best heater performance at the evaporator air setting of 16ºC with a variation of 10 passages. In conclusion, the addition of a heat recovery system with serpentine-type heat exchanger variations 10 passages, 12 passages, 14 passages, and 24°C temperature loading variations, 20°C and 16°C on the evaporator burst will have an impact on decreasing the coefficient of performance on the split air conditioner system.

Analysis of Heat Recovery System Performance Using a Serpentine-Type Heat Exchanger on Water Heater with Fins Number Variation

The water heater is a common facility found in hotels or homes. There are alternative ways to do this besides using water heaters on the market, namely by utilizing the heat generated by the compressor and which will be discharged through the condenser, by adding a heat recovery system to the air conditioning unit. These research tests were carried out on variations of the serpentine-type heat exchanger with variations in the number of fin plates on the performance of the heat recovery system and on the split air conditioner. This research is an experimental study on a serpentine-type heat exchanger. Tests were carried out on a variety of heat exchangers with variations in the number of fin plates combined with a heat recovery system on a split AC. The independent variables in this study were three variations of the placement of the fin plate on the serpentine-type coil and the setting of the output air of the AC evaporator. Enthalpy values, refrigeration effects, compressor work, condenser, and coefficient of performance (COP) are calculated and presented in tables and graphs. The results of the performance of the heat recovery system obtained variations in the setting of the air burst coming out of the evaporator 24ºC has the highest COP value. The use of a heat recovery system can increase COP. With variations in the number of fin plates in a heat recovery system with a serpentine heat exchanger, the use of 5 fin plates has the hottest water temperature compared to the use of 3 fin plates and 1 fin plate.

Performance Evaluation of a Heat Recovery System Combined with a Helical-Type Heat Exchanger as a Water Heater

A heat recovery system is a form of reuse of wasted heat energy as a water heater. The water heater is an effort to utilize heat from the work of the compressor without reducing the function of the air conditioner as a room cooler. This study aimed to evaluate the coefficient of performance between standard air conditioners and modified air conditioners with heat recovery systems using a helical-type heat exchanger with a distance of 0 cm between coils. This was an experimental study on a helical-type heat exchanger. Tests were carried out on standard split air conditioners and modified split air conditioners with heat exchangers. The independent variables in this study are variations of the helical type heat exchanger with a distance of 0 cm between the coil and variations in the air setting at the evaporator output. 16ºC, 20ºC and 24ºC. The dependent variable in this study is the coefficient of performance. The evaporator outlet air temperature setting of 16°C has the greatest heat recovery system value, and this is because the evaporator outlet air temperature setting of 16°C has the largest h2 value compared to other evaporator outlet air temperature settings. The greater the evaporator output air temperature setting, the greater the value of the resulting heat recovery system. In conclusion, the highest coefficient of performance is found at the evaporation exit temperature of 24ºC, and the variation in the distance between the coil is 0 cm. Meanwhile, the hottest water temperature is found in the evaporator air setting of 16ºC with a variation of the distance between the coil of 0 cm.

Experimental investigation on split type window Air conditioner using HFC and HC mixture as ecofriendly refrigerant alternate to HCFC-22

This paper reports on an experimental study evaluating a window air conditioner's performance when R152a/R290/R600/R600a refrigerant mixture (by various mass percentages) is used as a possible alternative to R-22. Alternative refrigerants are local, cheap, and environmentally friendly. Unmodified R-22 window AC was charged with R152a/R290/R600/R600a. During the experiment, parameters such as coefficient of performance, refrigeration effect, pressure ratio, compressor discharge temperature, refrigerant mass flow rate, and compressor power are analyzed. The present work shows that R152a-15%/R290-15%/R600-35%/R600a-35% is the best-performing alternative refrigerant. Proposed blends and R22's performance were compared.

Implementation of Political Position, Organizational Composition, Description of Duties and Functions and Working Procedures of the Indonesian Human Resource Development Agency

This study aims to provide an overview and evaluate the development ability of state’s employee in East Java State’s Employee to receive human resources training, and to analyze the determinant factors that contribute to their achievement and their ability to fulfill their obligation. This research was conducted in East Java Human Resources Development Agency. This type of research is qualitative with a case study approach. Data collection techniques were carried out by observation, interviews and documentation. Data analysis was carried out using qualitative descriptive analysis with the following steps: data reduction, data presentation and data verification. The research results show that, the use of village funds, both in terms of planning and implementation, is not only not participatory, it even involves more bureaucratic officials at both the village and district levels. The next consequence is the emergence of programs that should be different from one village to another because of different needs and desires, but in reality the programs in the four villages are uniform, such as making drainage, veving blocks, procuring mobile phones and air conditioners as well as repairing and renovating village offices. The determinant factors that contribute to village readiness in receiving human resources training include the time factor (timing), regulatory factors, and prudential factors. The Village Fund as a policy is considered to be implemented too quickly, before it is implemented there must be preconditions such as readiness, both institutional, human resources and programs. Likewise, regulations that change frequently result in overlapping policies and issues of caution that make implementers ambiguous, half-hearted, and even fearful of receiving and implementing village funds.

Effect of Reaction Inhibitor on Diesel Explosion of Split Air Conditioners

Effect of Reaction Inhibitor on Diesel Explosion of Split Air Conditioners

Performance Evaluation of Split Air Conditioner with Consideration of Pressure Drop in Evaporator and Condenser

In this research, a split air conditioner's performance has been evaluated using exergy analysis on three different low global warming potential (GWP) refrigerants, namely R32, R447A, and R447B, to find a replacement for the GWP-high refrigerant R410A. With regard for pressure loss in the evaporator and condenser, a computational model is built to recreate the operational conditions of a split air conditioner. GENETRON Properties 1.4 software is used to calculate performance metrics such as coefficient of performance (COP), exergy destruction ratio, exergetic efficiency, and efficiency defect. Result shows that pressure drop in evaporator alone has an adverse effect on COP and total exergy destruction and it is higher at higher pressure drop. Effect of pressure drop on exergetic efficiency and exergy destruction ratio is found to be less significant with condenser pressure drop compared to evaporator pressure drop. Exergy efficiency is found to be maximum with R447A followed by R447B, R32, and R410A.