Split Air Conditioner Research Articles

Performance Investigation of Vapor Compression Cycle with a Variable Speed Compressor and Refrigerant Injection

The performance of vapor compression refrigeration system with controllable speed compressor and vapor and liquid refrigerant injection techniques is experimentally investigated. For this purpose, a 5-tons (17.6 kW) split air conditioner unit charged with R-22 refrigerant was modified and equipped with, frequency inverter, secondary capillary tube, and liquid pressure amplification pump (LPA). Vapor refrigerant was injected into the accumulator with three injection mass ratios 2, 3, and 4%. LPA pump was used to inject liquid refrigerant from the condenser outlet to the discharge line with injection mass ratios 0.5%, 1.5%, and 2%. The compressor speed was controlled by frequency inverter, where the range of the frequency used was from 35 to 60 Hz with 5 Hz step. The results showed that the coefficient of performance (COP) of the modified system using vapor injection technique was improved by 11.26% compared to the conventional system, and the suction temperature reduced from 10.3 to -0.1°C with 3% vapor injection ratio. The best enhancement in COP was 9.9% for the 0.5% liquid injection ratio. Reduction of the compressor speed leads to improve the COP by 18% and reduces the compressor power by 36.4% at frequency 35Hz. Using the vapor injection with variable speed compressor improved the COP of the modified system by 75% at 35 Hz and 2% injection mass ratio.

ANALYSIS OF ENERGY EFFICIENCY RATIO (EER) IN AIR CONDITIONER (AC) TYPE SPLIT

Cooling system is something that is already familiar to the people of Indonesia, both in domestic and industrial use. The cooling system functions to reduce the temperature of a room so that the temperature is as desired. The development of air conditioners is increasingly modern. The use of air conditioners (AC) is growing rapidly so that the CFCs produced affect the environment which can cause the ozone layer to be damaged and cause global warming. Therefore, there is a need for research related to the level of energy use. This study discusses the Energy Efficiency Ratio test to realize a government program that is family one number testing. Retrieval of data in this report is by testing the split type air conditioner, where this test aims to obtain an energy-saving star label on the air conditioner. All tests are carried out at the AC Chamber Laboratory located at the Center for Energy Conversion Technology (B2TKE) - BPPT which is a professional energy conversion testing center in Indonesia. The testing process is carried out in a structured way from initial checking of test materials, preparation of tests, testing to analysis of test results. Based on the test analysis results, it can be concluded that the Energy Efficiency Ratio (EER) value to get the energy saving sign star label and the test results obtained the Energy Efficiency Ratio (EER) value of 11,805 Btu / h and get a four star.

Energy, Exergy and Anergy Analysis of Vertical Split Air Conditioner Under experimental ON-OFF Cycling

A time series analysis can help to observe the behavior of the system and specify the system faults. In addition, it also helps to explain the various energy flows in the system and further aid in reducing the thermodynamic losses. The intelligent supervisory LabVIEW software can monitor the incoming data from the system by using Arduino microcontroller and calculates the important parameters. Energy, exergy, and anergy analysis present in this paper to investigate the system performance as well as its components. To accomplish this, a 4-ton vertical split air conditioner based on vapor compression refrigeration cycle charged with refrigerant R-22 was modified for experimental analysis. The results showed that during 5400 secs of experimental study, the system shut down once by the software for 5 min. The volumetric and isentropic efficiencies of the compressor were 79.85 % and 64.48 % respectively. The maximum entropy generation was due to the compressor of 3.4 W/K while the maximum anergy was due to the condenser of 1.39 kW. The exergy efficiencies of the compressor, condenser, and the evaporator were 73.57, 40.18, and 47.45 % respectively. The system and Carnot COP were 2.53 and 4.9 respectively. The exergy efficiency of the air conditioning system was 48.7 %.

Нормализация теплового режима протяженных тупиковых выработок при высоких температурах пород на основе шахтных передвижных кондиционеров

Thermal working conditions in the deep mines of Donbass are the main deterrent to the development of coal mining in the region. Mining is carried out at the lower technical boundaries at a depth of almost 1,400 m with a temperature of rocks of 47.5-50.0 °C. The air temperature in the working faces significantly exceeds the permissible safety standards. The most severe climatic conditions are formed in the faces of blind development workings, where the air temperature is 38-42 °С. It is due to the adopted coal seam mining systems, the large remoteness of the working faces from the main air supply openings, the difficulty in providing blind workings with a calculated amount of air due to the lack of local ventilation fans of the required range. To ensure thermodynamic safety mine n.a. A.F.Zasyadko we accepted the development of a draft of a central cooling system with ground-based absorption refrigerating machines with a total capacity of 9 MW with the implementation of the three types of generation principle (generation of refrigeration, electrical and thermal energy). However, the long terms of design and construction and installation work necessitated the use of mobile air conditioners in blind development faces. The use of such air conditioners does not require significant capital expenditures, and the terms of their commissioning do not exceed several weeks. The use of a mobile air conditioner of the KPSh type with a cooling capacity of 130 kW made it possible to completely normalize the thermal working conditions at the bottom of the blind workings 2200 m long, carried out at a depth of 1220-1377 m at a temperature of host rocks 43.4-47.5 °С. It became possible due to the closest placement of the air conditioner to the face in combination with the use of a high-pressure local ventilation fan and ducts, which ensured the air flow produced by the calculated amount of air. The use of the air conditioner did not allow to fully normalize the thermal conditions along the entire length of the blind face but reduced the urgency of the problem of normalizing the thermal regime and ensured the commissioning of the clearing face.

Mathematical and experimental analysis of the thermal effectiveness of an oscillating jet with side-to-side swing louvers in a cassette split type air conditioner

The impact of air supply control strategies (louvers movement) on indoor thermal environment were evaluated in this study. The temperature uniformity was evaluated by: (i) the air distribution performance index (ADPI) to determine the air diffusion performance in heating mode; (ii) the air draught rate (DR%) on the face to determine the local discomfort due to cold draught; (iii) the mathematically determined vertical temperature stratification in a room with Beta distributions. A comparison of the conventional type with three different oscillating type airflows (louvers swing angle ±20°, ±40° and ±60°) were experimentally analysed to determine appropriate air supply control strategies. The results indicated that Beta distributions could capture the overall trend of the oscillating airflow, to establish the acceptable thermal uniformity and higher thermal effectiveness. The oscillating airflow as generated by the side-to-side swing type delivery louvers mounted inside a cassette split type air conditioner could shorten heating time by 20% to attain room temperature from 9°C. The data reveal that oscillating airflow can provide a better thermal sensation to feeling warm in the heating mode at both ankle and neck level. The ADPI is approximately 85% in the occupied zone. The actual draught rates on the face ranged 0–35%.

Experimental research on charge determination and accumulator behavior in trans-critical CO2 mobile air-conditioning system

Natural refrigerant CO2 (R744) is one of next generation refrigerants in mobile air conditioner (MAC) application with superior environmental and heating performance. This paper investigated the charge characteristics and refrigerant migration behavior of a trans-critical CO2 MAC. A novel visualized accumulator with five observation mirrors was adopted to set up this CO2 MAC. A series of steady-state system experiments were carried out in a calorimeter facility to reveal the effects of refrigerant charge and EXV opening on system performance and accumulator behavior. In addition, the transient migration behavior of refrigerant during shutdown and start-up and the flow behavior of lubricant oil with 0.5 mm oil return hole were studied experimentally. It is found that a plateau region with optimal system performance occurred between 1100 g and 1600 g refrigerant charge. When the return hole becomes small, stratification of lubricant oil and liquid refrigerant was found in the accumulator.

An investigation on energy savings of a split air-conditioning using different commercial cooling pad thicknesses and climatic conditions

In hot climates, performance of vapor compression cooling cycles decreases sharply, and consequently, energy consumption rises. Pre-cooling the air before it enters the condensing system can enhance the system performance and protect our environment. In this study, an experimental investigation on energy savings of a split air-conditioning utilizing evaporative cooling technology is conducted under a wide range of weather conditions. Thermal performance of commercial corrugated papers which are available at low cost is investigated experimentally in a wind tunnel. These characteristics are used in designing the evaporative cooling system. Depending on the maximum saturation efficiency, low pressure drop, and maximum performance, the optimum pad thickness was observed at 100 mm. Results showed that at this thickness, the power consumption decreased from 15 to 22% and the overall COP increased from 29% to 53%. Depending on the energy cost and regional usage, the maximum savings in the overall energy cost is $21.6/year. The cost of water consumption is $ 1.82/year. The payback period for the proposed system is less than three years and finally the life-cycle cost saving is between 242 and $ 400.

Performance analysis of low GWP refrigerants mixture as a substitute for R410A in residential air conditioner in tropical region

The issue of global warming has triggered more critical issues, and today’s refrigerants with high global warming potential (GWP) are facing the challenges of being phased out. According to 2014 Assessment Report of the Refrigeration, Air-Conditioning and Heat Pumps Technical Options Committee (RTOC Assessment Report 2014), the R410A has GWP of 2100 and is widely used in residential air-conditioning and heat pump systems. Currently, in the market, the potential refrigerant that can be used to replace R410A in the air-conditioning system is R32. The purpose of this project is to create a new refrigerant mixture using low GWP refrigerant as a base that can replace for R410A in an air-cooled split air conditioner. Simulation works have been developed using Refprop software to simulate the refrigeration cycle with the operating conditions of the air-cooled split air conditioner, in the tropical region. The chosen cycle was an ideal vapour compression cycle with the evaporating and condensing temperatures of 5 °C and 47 °C, respectively. Through this study, two potential refrigerants mixture was found to be suitable to replace the R410A. The two refrigerant mixtures, R32/R1234ze and R32/R600a, both based on R32, were found to have similar thermodynamic properties as the R410A. They were found to be able to produce the coefficient of performance (COP) very close to the R410A when used in an air-cooled split air-conditioning system. Hence, the use of this refrigerants will avoid significant modifications on the present air-conditioning system configurations. Refrigerant R32/R1234ze has the potential to reduce the GWP of R410A by 70 % while refrigerant R32/R600a by 73 %. At the end of the equipment lifespan, refrigerant R32/R1234ze would reduce the direct of Total Equivalent Warming Impact (TEWI) by 23 % while refrigerant R32/R600a by 20 %.in constructing both.

Experimental and Numerical Study of Cooling Performance of Air Conditioner Using R32/CO2 Refrigerant Mixture

Conventional refrigerants such as chlorofluorocarbons and hydrochlorofluorocarbons have high values of global warming potential (GWP) and ozone depletion (ODP). HVAC&R engineers and designers are exploring alternate refrigerants having low ODP and GWP. At present, R32 refrigerant is being considered as an alternative to the conventional refrigerants in domestic air conditioners by many manufacturers and countries. This study analyzes the steady-state cooling performance of a split air conditioner using R32(CH2F2) and R32/CO2 (Carbon Dioxide) mixture having lower GWP. The performance of the air conditioner with R32 and four different compositions of R32/CO2 mixture is studied experimentally and numerically. A comparative analysis of performance characteristics such as cooling capacity, total energy consumption, energy efficiency, operating pressures and temperatures is presented in this study.

Experimental Investigation of Low GWP Refrigerants Applied to Split Air Conditioner

In this work, the thermal and environmental investigations for split air conditioner using low global warming potential (LGWP) refrigerants as alternatives to the present R22 are examined experimentally. Two alternative refrigerants of R290 (GWP=20) and R152a (GWP=133) are examined instead of R22 (GWP=1700). The experiments are carried out at different range of evaporator air velocities and evaporator air inlet temperatures. The experiments are conducted at evaporator air inlet temperatures of 31oC, 38oC and 48oC, the air passes over evaporator coil with velocity of 0.5 to 1.6 m/s. The study parameters such as different evaporator air temperature, discharge temperature, cooling load, electrical compressor power, coefficient of performance, indirect global warming parameter and total equivalent warming parameter are investigated. The experimental results indicate that refrigerant R152a has the higher thermal performance than R22 and R290 and produces the lowest total equivalent warming parameter. At a certain evaporator air velocity is 1.2 m/s and the evaporator air inlet temperature is 31°C, the coefficient of performance of R152a is higher than that of R22 by 44.92%. The Total Equivalent Warming Impact of R290 and R152a are lower than that of R22 by 8.2 % and 30.03 %; respectively

Assessment of CO2-based demand controlled ventilation requirement for a flexible work environment with ductless split air conditioners

Use of ductless split air conditioners in small workspaces leads to accumulation of carbon dioxide due to the absence of fresh air entry. Additional mechanical ventilation is required to meet the ASHRAE standard. Providing constant-rate ventilation would reduce the CO2 concentration but would lead to high energy consumption when there is variation in occupant density. Instead, demand-controlled ventilation, that is, ventilation rate linked with the occupant density, can reduce energy consumption and maintain adequate indoor air quality. The purposes of this study were to quantify the temporal variation of CO2 in a workspace, to determine the factors influencing the demand-controlled ventilation strategy, and to assess its performance in workspaces with flexible work environment (varying occupant density with time). A parametric study on demand-controlled ventilation design indicates that the ventilation cycle time depends significantly on the occupant density and the range of threshold levels of CO2. The occupants can decide the lower CO2 threshold level based on the requirements. Use of a lower CO2 threshold limit of 700 ppm in a typical workspace with varying occupant density resulted in an energy saving of around 90% when compared with the ventilation rate required by ASHRAE 62.1. The assessment would be helpful in identifying the workspaces that do not require external ventilation. The ventilation design strategy thus developed would help the building managers in improving indoor air quality and lowering energy costs when compared with the constant rate ventilation system.

Duty Cycle Control on Compressor of Split Air Conditioners Using Internet of Things Embedded in Fuzzy-PID

Duty Cycle Control on Compressor of Split Air Conditioners Using Internet of Things Embedded in Fuzzy-PID

Tuning thermostatic expansion valve for implementing suction line heat exchanger in mobile air conditioning system

The suction line heat exchanger is introduced in a mobile air conditioning system in order to achieve higher energy efficiency. Recent studies reveal that improvement in the system with suction line heat exchanger greatly depends on refrigerant properties and operating conditions. In this work, suction line heat exchanger was incorporated in a mobile air conditioning system and the spring force in the block-type thermostatic expansion valve of the modified system was adjusted (1) to match with the cooling capacity and (2) to match with the suction degree of superheat of the original system as two different cases. The refrigerant R134a was used in this study. The optimum charge of the mobile air conditioning system using R134a with suction line heat exchanger was experimentally found to be 740 g which was 19.4% higher than that of the original system. At optimum charge level before tuning the thermostatic expansion valve, the coefficient of performance (COP) of the system was increased by 2.8%, while the cooling capacity was reduced by 6%. After retuning the thermostatic expansion valve to match the original cooling capacity, the COP of the system improved by 11.8% with 10.5% lesser power consumption than that of the original system. With retuned thermostatic expansion valve for the original degree of superheating, the cooling capacity and COP of the system were increased by 6.7% and 16.2%, respectively. From this experiment, it is concluded that the mobile air conditioning system using R134a as a refrigerant with suction line heat exchanger performs better with suitable retuning of thermostatic expansion valve for the same degree of superheating than that is tuned for same cooling capacity.

Sizing and life-cycle assessment of building integrated thermoelectric air cooling and photovoltaic wall system

This study presents a procedure for calculating the size and cost of integrating thermoelectric air cooling duct (TE-AD) and photovoltaic wall (PV-W) systems with test room in tropics. The investigation of economics and energy consumption was conducted, wherein three categories of air cooling systems-split air conditioner, Grid connected TE-AD system (G_TE-AD), and PV connected TE-AD system (PV_TE-AD) were compared. The sizes of the TE-AD system and PV system were determined based on the test room cooling load, sunshine duration, and daily electrical power required by the TE-AD system (kWh/day). The results obtained via life-cycle assessment (LCA) of the above systems suggested that the PV_TE-AD cooling system provides better economic and energy saving potential with better carbon emission reduction, compared to the other two systems. PV_TE-AD cooling system incurs operating costs of US$ 44.0 and US$ 151.0, lower than the G_TE-AD system and the split air conditioners, respectively. CO2 emission reduction of PV_TE-AD system reached 60.24 tons, which was two times less than that of the G_TE-AD system. The payback period of the G_TE-AD system was 4.2 years, which was six months lower than that of the PV_TE-AD system owing to the additional initial cost of the PV system.

Does country-of-origin matter in the era of globalisation? Evidence from cross sectional data in Uzbekistan

Purpose The purpose of this paper is to examine the consistency over time of customer attitude towards country-of-origin in a transitional economy. Design/methodology/approach A single cross-sectional study in Uzbekistan was carried out, with n=527, consisting of 374 street and 153 online surveys, replicating a study carried out 20 years earlier. Findings Whilst consumers still perceive products from advanced countries to have higher quality, quality perception in relation to country-of-origin information is dynamic and transitional countries can improve the perception of consumers towards their national brands. Research limitations/implications This study was carried out in Tashkent, the capital of Uzbekistan, the most populous of the Central Asian republics. Researchers may wish to extend it by examining COO effects in other transitional economies, and additionally to examine the effect of country-of-brand origin. Practical implications Customer perceptions and attitudes take a long-time to evolve. This cross-sectional study showed that the COO perception of China has improved significantly and the perception towards the products produced locally in Uzbekistan has also slightly improved across all categories. Strong brands can contribute to the image of the country. Transition countries need to take appropriate marketing actions to cultivate positive perception through innovation and branding. Originality/value Prior research has been extended by adding new product categories such as mobile phones, computers, washing machines and air conditioners. This research shows that government officials and exporters in developing countries should prioritise strengthening their country’s image to help domestic marketers export and attract foreign investors. The authors provide insights for marketers to understand the impact of product country-of-origin on customer purchase intention and its antecedents in transitional economies, such as Uzbekistan.

Thermodynamic Analysis of Two-Phase Ejector as Expansion Device with Dual Evaporator Temperatures on Split Type Air Conditioning Systems

This paper presents a numerical and experimental study of increasing the performance coefficient (COP) of split AC (SAC) by reducing compressor work and increasing cooling capacity. Two phase ejector as an expansion device with a new design of dual evaporator temperature used. numerical methods apply the mathematical model developed in the EES software that is applied. Thermodynamic analysis is carried out to achieve ASHRAE Standard requirements for a minimum SAC with COP application of 3.5. The SAC system is filled with R-290 as a thermal fluid medium. Based on the simulation results a numerical model of the ejector is then produced and installed in a modified SAC system of cooling capacity of at least 9000 BTU/hour. An experimental test was conducted to investigate the actual performance of the ejector and its effect on the performance of the SAC system. The results showed that the two phase ejector with the new design of the dual evaporator temperature system was successful. When compared to standard split air conditioners using capillary tube expansion devices the tested ejector system contributes around 35% of power savings. The COP of the system can reach 5.5 which accounts for 39% of the increase in performance.

A potential approach for reducing the R290 charge in air conditioners and heat pumps

This study presents a potential approach for reducing the propane (R290) charge required in air conditioners (ACs) by introducing micro bare-tube heat exchangers as the condenser and evaporator. A theoretical model is developed to predict the performance of a split AC unit, and the unit is tested in an experiment. The split AC unit is tested under the ISO 5151:2017 standard capacity rating test condition in a psychrometric room (outdoor conditions: 35 °C dry bulb/24 °C wet bulb; indoor conditions: 27 °C dry bulb/19 °C wet bulb). The compressor input electricity power is 928 W with 62-W condenser fan power and 82-W evaporator fan power. The test cooling capacity is 3645 W with a system coefficient of performance of 3.40. The stainless steel micro-tube heat exchanger has a 0.58-mm outer diameter and 0.38-mm inner diameter. Owing to the use of micro bare tubes, the optimal propane charge is 248±5 g, which follows the EN378-1:2016 regulation. The use of micro bare-tube heat exchangers in a split AC unit could be a potential approach to reducing the R290 charge required in ACs and heat pumps.

The experimental study of R290 mass distribution and indoor leakage of 2 HP and 3 HP split type household air conditioner

R290 is a promising future refrigerant, but its flammability presents the biggest obstacle to its adoption. This paper is concerned with the safety of a 2 HP and 3 HP split type household air conditioner (STHAC) with a 400 g, 450 g and 500 g charge of R290. Evaluation of the mass distribution of R290 in the indoor and outdoor units of the 2 HP and 3 HP STHAC was carried out and the R290 concentration distribution in a sealed room after a leakage under different scenarios was also examined. The results show that most of the refrigerant (72–80%) was located in the outdoor unit during the steady cooling mode. In the event of a leak indoors the combustible zone only appears underneath the leak position in the sealed room. The range and residence time of the combustible zone will increase with higher refrigerant charge quantity and negligible fire hazard appeared in the room if the leakage hole was 0.5 mm. In addition, the practical and achievable approach to significantly reduce the leaking rate and minimise the flammability hazard was found to be by installing a solenoid valve behind the capillary tube and is effective in both 2 HP and 3 HP STHAC.

Physiological thermal response in typical air conditioning Environment

Energy consumption for space cooling is increasing in Chinese residential buildings due to the extensive use of split air conditioners. To build a comfortable indoor environment and reduce energy consumption, comprehensive understanding about human thermal requirements of air conditioning is highly needed. As a reflection of human demand for indoor thermal environment, thermal sensation is usually under the effect of human physiological responses. For these reasons, a series of experiments were conducted in a climate chamber to understand human physiological thermal responses in air conditioning environment. During the experiments, indoor temperature was kept at 29°C in the first 30 minutes and then cooled down to 25°C in the next 30 minutes, after that, indoor temperature was held stable in the final 60 minutes. Twenty subjects were recruited to participate in the experiments. Results reveal that first, the temperature of limbs was lower than trunk due to the blood flood and clothing resistance, second, skin temperature and Thermal Sensation Vote(TSV) may still be in the dynamic change after the ambient temperature reached stable, third, significant linear correlation was found between skin temperature and TSV in the limbs, moreover, individual difference could be found in local skin temperature.

Performance evaluation of a mobile air conditioning unit: an exergetic approach

This study considers a public bus (having a capacity of 99 passengers and a volume of 69 m3) along with its vapour compressed mobile air conditioning (MAC) unit (utilising R134a as a refrigerant) together as a low exergy (so-called LowEx) system. The LowEx analysis, which has been mostly applied to buildings, and conventional exergy analyses method are utilised together (coupled up analysis method) to assess the performance of this system for the first time to the best of the authors' knowledge. Based on the LowEx analysis, total exergy efficiency and exergy flexibility factor are calculated to be 11.92% and 0.56 for the heating mode and 3.41% and 0.19 for the cooling mode, respectively. Furthermore, through on the conventional exergy analyses, the highest exergy efficiency belongs to condenser with 93.08% in the cooling mode, while it is 93.20% for the water heat exchanger in the heating mode, respectively.