Split-type Air Conditioner Research Articles

Optimal thermohydraulic design of the indoor unit of a split-type air conditioner

A CFD-based optimization process was used to design an air supply casing shape for the indoor unit (IDU) of a split-type air conditioner (SAC). The aim was to enhance the IDU performance, including the volume flow rate and total cooling capacity. To this end, the numerical results, including the pressure, velocity, temperature, and humidity ratio distribution, were used to evaluate the IDU performance. For the CFD-based optimal design, a 3D printer was used to manufacture an optimized casing in combination with four IDU geometric parameters. The optimal tongue gap, rear wall gap, and radii of curvature for the first and second segments were 2.2, 8.4, 56.7, and 98.8 mm, respectively. As a result, the measured and predicted volume flow rate and total cooling capacity of the optimized IDU increased by nearly 20% and 27%, respectively, compared with those of the original IDU. Moreover, the predicted and measured volume flow rates and total cooling capacities agreed well, with the relative errors of the IDU performance being less than 1% and 5%, respectively. In addition, the measured power consumption of the cross-flow fan of the optimized IDU was reduced by 19.4% compared with that of the original IDU.

Development of a Stand-Alone Thermoelectric Power Generator Using Heat of Refrigerant Leaving the Condenser and Self-Cooled by Condensate of a Split-Type Air Conditioning

Today waste heat recovery of air conditioning is receiving considerable attention worldwide. This paper reports investigation on the development of a stand-alone thermoelectric power generator (STEG) using heat of refrigerant leaving the condenser and self-cooled by condensate of a split-type air conditioning. The STEG is composed of a small hollowed aluminum block integrated in the hot refrigerant line leaving the condenser to collect and transfer heat to the hot side of two thermoelectric (TE) modules 40 x 40 mm installed on the right and left. To cool the TE modules, water condensate circulates by gravity inside two aluminum alloy blocks. Tests were conducted using 2-tons split-type air conditioner installed in a 64 m3 room of a residential house in Bangkok. Electrical current generated by the two TE modules was recorded separately and connected in series three times for each case. Experimental results showed that STEG can produce electrical current continuously and varied depending on the operation on the compressor. The more important the cooling, the higher is the voltage produced. The maximum recorded voltage is about 200-250 mV by each TE module and doubled with the TE modules connected in series. The average water condensate flowrate was 11.56 g/min. The average coefficient of performance (COP) and the average Energy Efficiency Ratio (EER) of the air conditioning with STEG were 1.87-1.88 and 6.38-6.42 respectively, 3% higher than those of the conventional system.

Experimental Investigation of Using Liquid Suction Heat Exchanger with Condensed Cold-Water on the Performance of Air Conditioning System

This paper reports experimental investigation of using liquid suction heat exchanger (LSHX) with condensed cold-water (LSHX-CW) on the performance of a split type room air conditioning. To this end, we used a large room of a residential house of 64 m3 equipped with a 2-tons conventional commercial split-type air conditioner fitted with R22. The coaxial design of LSHX-CW allows to exchange heat between the vapor and liquid refrigerants in the center part and condensed water and the warm liquid refrigerant on the outer part. LSHX-CW was well insulated on the outside to reduce heat transfer with ambient. The air conditioning was tested several times for three scenarios namely, conventional system, system with LSHX alone and LSHX with condensed water LSHX-CW. Experimental results showed that the use of LSHX-CW improved the performance of air conditioning noticeably when compared to the use of LSHX alone. The maximum LSHX-CW effectiveness was 7.67%. The pressure discharge line and electricity consumed decreased by 8.23% and 9.40% respectively.

Quantitative Approach to Condensate from Residential Air Conditioners with Different Capacity as Drinking Water

During operation, the evaporator of split-type air conditioner (A/C) produces condensate water due to lower evaporator temperature, as compared to dew point temperature of the indoor air. So far, the condensate is considered unimportant and therefore being wasted. The split-type A/C is widely used in high-rise buildings, hotels, shopping areas, and even residential. The study aims to investigate the potential feasibility of the condensate to be used as for drinking water. Of course, treatment of the condensate is required before it can be used as a drinking water. The experiments were carried out in two cities, namely Bandung and Cirebon. Bandung represents a city with a cool climate, while Cirebon represents a city with a hot climate. The capacities of the A/C utilized in Bandung and Cirebon are 0.5 HP and 1 HP, respectively. The quantities of the condensate from the A/C were collected for 24 for hours. The quality of the condensate was benchmarked with guidelines/standard from PERMENKES NO 492/MENKES/PER/IV/2010. The benchmarking process involved testing and evaluation of 22 significant parameters related to water quality for drinking purpose. By utilizing waste condensate water, it is predicted that it can be a vital alternative of potable water in the future

Eco-design of an air conditioning system decrease in carbon footprint

The appropriate use of energy is vital for the sustainable development of society in the different productive areas such as the industrial, commercial and domestic sectors, in this sense the machines must use suitable materials tending to reduce the contamination of water sources and soil, emission of carbon dioxide into the atmosphere due to energy consumption. In this context, the objective of the study focused on designing an air conditioning system based on the carbon footprint; life cycle analysis (LCA) and eco-designs were applied as a methodology, allowing to identify the categorization of the contaminant and its level of environmental impact, from the extraction of resources, manufacturing, distribution, use and final disposal. It was possible to evaluate the environmental impact referring to the functional unit of a split-type air conditioning system of 12,000 BTU of cooling capacity, obtaining as a result the carbon footprint with an annual carbon dioxide quantification of 722.8 tons of carbon dioxide. carbon (CO2), significantly representing the intensive use of the system and, on the other hand, the energy required for the manufacturing process of the refrigerant gas hydrofluorocarbons (HFC) R410 A.

Performance of Split-type Air Conditioner under Varied Outdoor Air Temperature at Constant Relative Humidity

Studies related to the effects of ambient temperature on the performance of an air conditioning unit have been carried out for decades. However, specific study concerning the effect of varied ambient temperature under constant relative humidity has not been reported yet. This paper discusses the operating conditions and performance of an air conditioner with R32 and nominal capacity of 2.6 kW. The test was carried out in a controlled psychrometric chamber under constant relative humidity of 50% and varied outdoor air temperature from 24 to 38°C. The increase of outdoor air temperature affects the operating conditions of the air conditioner. Generally, if the outdoor air temperature increases by 1°C the evaporating temperature increases by 0.27°C. Meanwhile, refrigerant suction temperature, discharge temperature, and condensing temperature increase by 0.08°C, 1.08°C, and 1.04°C, respectively. Under the same tests, the cooling capacity decreases by 1% and power consumption increases by 1.6%. In addition, the energy efficiency ratio of the air conditioner decreases by 2.1% per 1°C increase of outdoor air temperature.

Classification and Analysis of User Behavior based on Action Duration in Residential Split-type Air Conditioners

In residential buildings, split-type air conditioners (ACs) are important indoor thermal environment control equipment. This study focused on ACs in China’s hot summer and cold winter zone. The valid data included 196 million real-time operation log records of more than 5,000 ACs in one year. The goal of this study is to classify action duration in a quantitative and interpretable way and analysis the user behavior based on the classification of action duration. Through the human intervention by indicators and multiple-Jenks algorithm, user behaviors based on action duration were divided into 6 categories and 12 types. The comparison of these action types in mode, wind speed and setting temperature were discussed as well. It reveals that some action durations are need to be focused in different conditions.

Influence of the louver angle on the performance of the air-conditioning outdoor units in high-rise apartment buildings

The split-type air conditioners are widely used in high-rise apartment buildings in the major urban areas, especially Ho Chi Minh City - Vietnam, because of its convenience. In the apartments with limited space, the installation of outdoor units not in accordance with technical guidelines will affect the performance of the air conditioning system and the aesthetics of the apartment building. The aim of this study is to propose the technical room in apartments for properly installing outdoor units of air conditioning systems. The CFD method is utilized through Ansys Fluent software to determine the inlet air temperature of condensers and COP corresponding to the louver angle of 0o, 10o, 20o, 30o và 40o. The results obtained from the simulations show that increasing the louver angle results in rising the inlet air temperature of condensers and reducing COP. The average temperature of the air which entering the condensers does not change significantly when the louver angle increases from 0o to 30o. When the louver angle is more than 30o, the inlet air temperature of outdoor units exceeds the continuous operating temperature of 48oC. To maintain the high performance of the air conditioner during operation, the louver angle is adjusted as small as possible and limited to a value of about 30o.

A study on the quantitative single and dual fault diagnosis of residential split type air conditioners in static operation using support vector machine method

l Fault diagnosis for single and dual failure for air conditioners using SVM method. l Based on the existing sensors only. l Machine learning based on the database obtained from refrigeration cycle simulation. l Failure mode was detected with an accuracy of higher than 88%. l Failure level was predicted within ±10% of actual data. Owing to the recent uprise in summer temperatures, the use of air conditioners has been increasing accordingly. Air conditioners consume a significant amount of energy, and defects in air conditioners usually could lead to even more consumption of energy. Hence, early detection of defects could not only enhance user satisfaction, but also conserve energy. In the present work, quantitative fault detection models for single- and dual-failure modes have been developed using a support vector machine technique based on refrigeration cycle simulation data including normal and defective conditions. The defect modes investigated in the present work include refrigerant shortage and degraded air flow rates for the evaporator and condenser of an air conditioner. The results indicate that the proposed method can predict the values of more than 95% of the defective parameters within ± 5 % for the single-failure mode, and more than 90% of the data within ± 10 % for the dual-failure mode.

RECESSED BALCONY HEAT RE-ENTRY EFFECT ON FAÇADE WITH CONDENSER UNITS

The use of split-type air conditioner in Surabaya results in the almost universal typical apartment layouts which feature a recessed balcony upon the building’s exterior façade which then utilized as air-conditioner condenser unit storage. Façade geometry with recessed balcony itself carries its own characteristic of surface air movement which affects the general Indoor Air Quality (IAQ) and heat dissipation of a building. Nevertheless, façade as architectural elements greatly influence building’s energy performance. Inefficiencies in heat dissipation from a condenser unit is detrimental on its performance and precipitate energy wastage. Based on computational fluid dynamics (CFD) analysis incorporated with energy performance evaluation, the effectiveness of façade geometry with recessed balcony is explored in this paper. It was found that recessed balconies are not an ideal place for condenser unit placement on a façade where many factors contributed to promoting heat re-entry from condenser units into the building’s interior.

Performance testing and optimization of a split-type air conditioner with evaporatively-cooled condenser

In this study, the performance of a split-type air conditioner with evaporatively-cooled condenser was examined. The effect of evaporative cooling of the condenser on the performance parameters and energy efficiency were determined by comparing the results from an air conditioner with conventional type air-cooled condenser. Both systems were tested simultaneously for different ambient conditions. An optimization study were also performed to find out the optimal climatic conditions for the proposed system. The effects of outdoor temperature and relative humidity on both total power consumption and COP were discussed. With the evaporative cooling of the condenser of the split-type air conditioner, the COP increased by 10.2%–35.3%, and the cooling capacity increased by 5.8%–18.6%, while the total power consumption decreased by 4%–12.4%. The results showed that the outdoor relative humidity and temperature had a significant influence on the COP, cooling capacity, and total power input for split-type air conditioners with an evaporative condenser. The results of the optimization study showed that the optimal condition maximizing the COP of the proposed system was confirmed as higher outdoor temperature and lower relative humidity. For the total power consumption, however, the optimal condition was found as medium levels of the temperature and humidity. The effect of the outdoor temperature on the electricity consumption is larger than that of the RH, and this provides an opportunity of using the proposed system in a wide-range climatic conditions.

Energy reduction of split-type air conditioners using a pre-cooling system for the condenser

In the residential sector in Thailand, the largest source of energy consumption is air conditioning systems, particularly in summer as a reason of the high ambient temperatures. These high ambient temperatures affect condensers and result in low efficiency for the rejection of the heat out of the refrigerant. Moreover, air conditioning systems remove moisture from the air conditioning space due to the moisture in the air being condensed at the evaporator. This problem has led to a reduction in air conditioning systems using the condensed water to pre-cool the condenser. This study investigates the potential of reducing the energy of split-type air conditioners. We investigate the heat rejection from the condenser with a pre-cooling system compared to a traditional condenser. The result of the heat rejection from the condenser is extended to investigate the multiple linear regression model for future work. The pre-cooling system uses a wasted condenser coil to reduce the air temperature before entering the condenser. A commercial split-type air conditioner is used in this study since this type is the most used in Thailand. An ultrasonic humidifier is also installed to maintain the relative humidity at 70%RH in all testing conditions. The thermostat set points are 25, 26 and 27 ºC as the testing conditions. Each thermostat set point is tested using the pre-cooling system in the air conditioner and the traditional air conditioner. In total, six conditions are performed. The result shows that the pre-cooling system in the air conditioner can reduce the energy consumed by the air conditioner. The maximum energy reduction is 26.6% when used the pre-cooling system in the air conditioner is compared to the traditional air conditioner. The maximum heat rejection of the condenser using the pre-cooling system in the air conditioner is 74.3% higher than the traditional air conditioner. The multiple linear regression models and the coefficient of determination are reported. Finally, we conclude that the pre-cooling system in the air conditioner using removed condensed water to reduce the ambient air temperature before entering the condenser can reduce the energy consumed of split-type air conditioners and can be improved in future work.

Experimental evaluation on a centralized air conditioning system embedded with a split-type air conditioner as a dedicated subcooler

Dedicated subcooling (DS) is one of the alternative methods to gain significant performance improvement in the air conditioning (A/C) system. However, DS increases the investment cost and the performance improvement depends on the capacity ratio between the subcooler and the main A/C system (RSM). As compared to previous studies, the present study investigates experimentally the performance of the A/C system equipped with DS at smaller RSM, and justify the economic advantage of the proposed system. The experimental study was conducted at constant outdoor, evaporation, and condensation temperatures of 30, 5, and 40°C, respectively. The experimental facility consists of a main A/C system with a compressor capacity of 11.25 kW and R22 as a working fluid. The sub-system is a split-type A/C system with compressor capacity of 0.75 kW and R290 as a working fluid. Four parameters; the degree of subcooling, cooling capacity, input power, and coefficient of performance (COP) were investigated. The results showed that the DS decreased the condenser outlet temperature , thus led to an average increase in degree of subcooling by 3.4°C. Consequently, cooling capacity of the main system increased by 1.4 kW, and the input power of the entire system (power consumed by the main and subcooler systems) decreased by 0.4 kW. As a result, the COP raised by 7.8%, as compared to system without DS. In the economic point of view, the analysis showed that the system with DS is economically viable and has a huge potential due to short payback period of just 11.81 months. • Residential air conditioner as a sub-system in producing dedicated subcooling. • The ratio on capacities of subcooler to main system determine the degree of subcooling of the main system. • The dedicated subcooling increases the cooling capacity and decreases the input power of the main system. • The COP increases when the power used by both the main and subcooler systems are considered. • Simple payback period of 11.81 months is expected for system with DS as compared to system without DS.

Noise control of outdoor unit of split type air-conditioner using periodic scatterers made with array of Helmholtz resonators

One of the reason for which the split type air-conditioner (AC) is preferred over window mounted air-conditioner is low noise. However, the outdoor unit of split type AC produces significant noise predominantly in low frequency regime and typically below 200 Hz. The sonic crystal, which is found suitable for outdoor noise control, is endeavored for attenuating the noise of outdoor unit of split type ACs. The challenge of designing a finite sonic crystal with scatterers having low diameter and minimum number of rows to attenuate the low frequency noise is addressed in present research by suggesting a tuneable multi resonant scatterer. The scatterer is made with multiple hollow compartments in the direction of height and having perforations which is tuned using finite element analyses. At last, the sonic crystal is fabricated and acoustically characterized in an anechoic chamber. The experimental investigations are conducted by deploying the sonic crystal near outdoor unit of three split type ACs and the noise measurements exhibit that the overall noise levels reduce by ≈7 dB.

Calculation method for the effect of heat rejection of split-type air conditioner on thermal environment and building energy demand for neighbourhood-level

The purpose of this research is to propose a simple and fast method to evaluate the effect of heat rejection of split-type air conditioner on the thermal environment surrounding the building and the building cooling demand to provide guidance for architectural design in the urban planning stage. In this paper, we first determined the factors that affect or are affected by heat rejection as heat dissipation, wind speed, and ambient air temperature, which as inputs to the CFD to build the regression model of the temperature rise. Then, the regression model is coupled with the energy consumption simulation software EnergyPlus to estimate the building cooling increase. The result of taking a typical residential building as a reference show that the maximum temperature rise and cooling demand increase with the values of 1.86°C and 17%.

Energy saving potential and environmental benefit analysis of application of balcony for residence in the hot summer and cold winter area of China

The increasing fossil energy demand and carbon emissions pose a significant challenge to the world. According to climate adaptability design, the balcony is open type in Changsha. The study evaluates the energy-saving potential and the economic and environmental feasibility of installing the balcony in living rooms, and considering the effect of balcony orientations and air conditioning types. The economic viability is analyzed using the construction cost of the balcony and the extra market price of a residence with a balcony paid by the holder, respectively. Environmental feasibility assessment mainly adopts the CO2 emission payback period as the index. The annual electricity saving percentage of the split-type air conditioner in the living rooms facing four orientations with a balcony is in between 6.7% and 12.3%. And the balcony's investment payback period facing east or west orientation is less than 50 years based on construction cost. It has better environmental benefits with the CO2 emission payback period of the balcony facing four orientations is in between 10.4 and 24.6 years. Considering a living room constructed with a balcony, it is not feasible for dwellers to use a gas boiler, adopting the radiant floor system during the heating from the perspective of economic and CO2 emission.

Indoor environment of nearly zero energy residential buildings with conventional air conditioning in hot-summer and cold-winter zone

• Explore the cooling demand of nearly zero energy residential buildings. • Indoor temperature variation and load characteristics under three air-conditioners. • Indoor environment under a newly proposed convective-radiation air conditioning. According to the few researches on Nearly zero energy residential buildings (NZERB) in hot-summer and cold-winter zone, although it could reduce the cooling load of buildings due to its high thermal insulation and air tightness, it still needed for certain cooling in summer. This paper studied indoor environment of NZERB under three kinds of air-conditioners (split-type air-conditioner, multi-line air-conditioner and ceiling radiant air-conditioner). Firstly, a simulation model of NZERB was established based on Nanjing, a typical city in hot-summer and cold-winter zone. Secondly, variation of indoor air temperature and building load characteristics with outdoor air temperature were studied. Thirdly, indoor environment and energy consumption under three selected conventional air-conditioners in summer were simulated. Finally, the discussion was given, and an air-conditioner combining with convective and radiant cooling were proposed. The results indicated that the air-conditioner needed to be turned on in NZERB in hot-summer and cold-winter zone due to the room air temperature in off-air condition ranged from 32 °C to 36 °C, which was higher than designed indoor environment temperature in summer, but the indoor environment of NZERB under three selected conventional air-conditioners could not meet the requirements of energy saving and comfort at the same time, and a proposed convective-radiant air-conditioner could be fast, stable, and energy saving. The findings can provide a reference for conducting active technology in NZERB.

Fabricating and testing of the ground coupled air conditioner for residential applications in Iraqi weather

In this paper, the ground-coupled air conditioning system has been experimentally studied in the weather of Nassriyah city, Iraq. Through the use of two systems of air conditioners of the same type (split-type air conditioner) with a capacity of 12,000 Btu/h where the first system is used a conventional air conditioner refers to (CAC).It cooled by the air with a condenser pipe length is about 13 m and the diameter is about 6.3 mm, meanwhile, the other system (modified air conditioner) refers to (MAC).It cooled by burying the condenser pipes inside the ground within a depth of about 3.5 m and a length of 27.5 m with a diameter of the pipe of 6.3 mm which used the ground as a heat sink. It is known that the temperature of the ground is constant almost depth of 3 m which it is measured at the Nasiriyah city and it found to be 26.1 °C around the year, therefore; The earth has a lower temperature compared to the temperature of the surrounding at Summers season and vice versa so that it happened at Winter season, that makes the ground to become a good heat sink for ground heat exchangers.The results of the two systems which performed from the end of April 2019 until the end of July 2019 showed that the coefficient of performance of MAC, it is higher than that for CAC with values of (6.1–8.48) and (5.5–7.1), respectively, Also it is found that the modified system is consuming lower electrical energy. The recovery period of the system calculated and found to be (8 months).

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

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

Sustainable enhancement of district heating and cooling configurations by combining thermal energy storage and life cycle assessment

District heating and cooling systems are designed and optimized to respond to the latest challenges of reducing energy demands while fulfilling comfort standards. Thermal energy storage (TES) with phase change materials can be employed to reduce the energy demands of buildings. This study considers a residential district located in Spain, where a general framework has been established to identify optimal combinations of energy conversion, delivery technologies, and operating rules. The Life Cycle Assessment (LCA) methodology was implemented within a mathematical model, and the objective function considered the minimization of environmental loads. Two environmental impact assessment methods were applied within the LCA methodology: IPCC 2013 GWP 100y and ReCiPe. Four optimal configurations were considered: a reference system (gas boiler and split-type air conditioners) and then three TES-based systems: one sensible (STES, water) and two latent (LTES1—paraffin emulsion and LTES2—sodium acetate trihydrate). Hourly environmental loads associated with electricity imports from the national grid were available. The conventional energy system always presented the worst performance from an environmental viewpoint, being penalized by the high consumption of natural gas. Regarding carbon emissions, LTES1 showed the lowest emissions, followed by STES and LTES2. Reductions in energy demands compensated the impact of paraffin, and results of STES are strongly dependent on tank design. However, considering the ReCiPe method, STES presented the lowest loads, followed by LTES1 and LTES2. Overall impacts of LTES1 with paraffin are higher than STES with water, mainly due to the paraffin and the high volume required.