Split Air Conditioner Research Articles

A comparative study on convective heat transfer in indoor applications

Analytical solutions may not always be applicable in the calculation of the turbulent flow convective heat transfer rate, unlike the radiative and the conductive ones. Therefore, experimental correlations on convective heat transfer coefficient have been developed in enclosures. Convective heat transfer in a cavity is classified as natural, forced, and mixed convection on the basis of the driving forces (buoyant or mechanical). In recent years, there has been an increasing interest in the mixed convection, particularly in cooled ceiling – displacement ventilation indoor applications. It seems this interest is tending to increase while contamination of viruses and energy saving are growing as health and environmental concerns worldwide. Hence, the reasons behind the interest in mixed convection applications have been investigated along the paper.This comparative study seeks to explain the progress of convective heat transfer at indoor applications by reviewing mostly experimental correlation studies in time. The mixed convection has not been widely studied experimentally in indoor applications in comparison to natural and forced convection. Therefore, this study is devoted to indicate this gap in the literature on this issue and it includes all convection types with a wide and up-to-date review, descriptions, explanations, and comparisons, as well. Moreover, almost all empirical correlations on the topic are given in tables in detail. It can be concluded that general correlations for mixed convection applications is needed. Correlations related to radiant floor cooling applications are nearly non-existent. Additionally, more experimental studies are required for various split air conditioner cases. These gaps in the literature are unveiled and comparison of applications with various convection types have been made as a first comparative study in the literature.

Performance analysis of retrofit R410a refrigerant with R32 refrigerant on a split air conditioner

Split air conditioning (AC) is the most widely used in the community for both commercial and domestic utilities. At the present refrigerant which used in Split AC is mostly common group of HFCs, such as R410a. R410a is a zeotropic refrigerant and if there is a leak in the system, it cannot be added this refrigerant. This will increase the cost of maintenance. The aims of this research is to investigate the retrofit of R410a with R32 on the Split AC system. The R32 is chosen because it has higher latent evaporation heat at the same temperature and has less effect on global warming. The refrigeration effect, the power consumption and the system performance are the main three quantities that want to be examined in this research which are observed before and after retrofit. Experimental investigation conducted during this research, including design and manufacture of experimental equipment, calibration and tools installment, collecting the experimental data and analysis by quantitative description method before and after retrofit. The results informed that cooling effect increased during the research, but the COP system has a slight decrease about 4%. R32 refrigerant is quite feasible as a retrofit refrigerant to R410a refrigerant.

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.

Influence of perceived control on thermal comfort in winter, A case study in hot summer and cold winter zone in China

Psychological impact is widely regarded as one of the most important factors in adaptive thermal comfort model. According to perceived control theory, perceived control is an important part of psychological impact. In order to explore the effect of perceived control on thermal comfort in the Hot Summer and Cold Winter (HSCW) zone in China, a field study and a climate chamber experiment were conducted. The field survey on thermal comfort was carried out in two residential buildings with split air-conditioners and central heating systems respectively in HSCW zone in winter. The results show that the thermal neutral temperatures of residents in residential buildings with split air-conditioners and central heating systems are 16.9 °C and 18.6 °C. From the perspective of thermal comfort, the central heating system in northern China is not suitable for direct application in southern China. Then, the effect of perceived control on thermal comfort was tested in a climate chamber. The results show that when the indoor operative temperature deviates from 18 °C, the thermal sensations of subjects with perceived control are closer to thermal neutral than those without perceived control. The effect of perceived control has a linear relationship with indoor operative temperature. The experimental results show that the perceived control can improve the thermal comfort of residents in winter. It is suggested to provide residents various ways to effectively control the thermal environment through windows and controllable terminal of heating systems, which can improve the thermal comfort of residents and reduce heating energy consumption.

Two deaths due to explosion of cylinders of liquid petroleum gas

BackgroundCylinder blasts can inflict multi-system life-threatening injuries to one or many persons simultaneously if they are nearby. The explosion in high-pressure equipment produces injuries due to its varied effects. Cases have been reported where the blast occurred in balloon gas cylinder, oxyacetylene gas cylinder, oxygen cylinder, coffee machine, and compressor of a split air conditioner (AC). Most of the cases are accidental. The investigation into the blast circumstances is of utmost importance to find out the manner and device involved.Case presentationHere, we present a report of two cases where victims suffered blast injuries at the same location due to the explosion of two different capacity liquefied petroleum gas (LPG) domestic cylinder and died on the spot.ConclusionThe investigation into the blast circumstances is of utmost importance to find out the manner and device involved. Malpractice involving use of cylinder to fill another one might be dangerous for the person involved and present in the vicinity. This practice should be discouraged by lay person.

Energy Performance Assessment Framework for Residential Buildings in Saudi Arabia

The residential sector consumes about 50% of the electricity produced from fossil fuels in Saudi Arabia. The residential energy demand is increasing. Moreover, a simple building energy performance assessment framework is not available for hot arid developing countries. This research proposes an energy performance assessment framework for residential buildings in hot and arid regions, which focuses on three performance criteria: operational energy, GHG emissions, and cost. The proposed framework has been applied to three types of residential buildings, i.e., detached, attached, and low-rise apartments, in five geographical regions of Saudi Arabia. Design Builder® was used to simulate the energy demand in buildings over a whole year. Four types of efficiency improvement interventions, including double-glazed windowpanes, triple-glazed windowpanes, LED lighting, and split air conditioners, were introduced in 12 combinations. Overall, 180 simulations were performed which are based on 12 intervention combinations, three building types, and five regions. Three performance criteria were evaluated for each simulation and then aggregated using a multi-criteria decision analysis method to identify the best intervention strategy for a given building type and a geographical region in Saudi Arabia. Each building type with interventions consumes higher energy in the western, central, and eastern regions and consumes a lesser amount of energy in the southern and northern regions. The proposed framework is helpful for long-term planning of the residential sector.

Experimental study on the effect of condensate water on the performance of split air conditioning system

A method of using condensate water to reduce the airflow temperature around the air conditioner condenser and improve the performance of air conditioner is presented in this study. The structure of traditional split air conditioner is adjusted by changing the installation direction of fan and adding disk-type atomization cooling element (ACE) in the outdoor unit. The performance of the air conditioner under four modes is tested in different environment temperatures. Four modes were named, i.e. the original unit without ACE, original unit with ACE, blowing mode without condensate water and blowing mode with condensate water. The blowing mode with condensate water is used to pre-cool the incoming airflow, and the maximum temperature reduction at the air outlet surface of the condenser is up to 2.2 °C in 35 °C. With the environment temperature increasing, the refrigerating capacity of four modes decreased, and the power consumption increased, leading to the decrease of EER. However, owing to the cooling effect of condensate water, the performance of blowing mode with condensate water was greatly improved compared with the original unit without ACE. The variation rates of refrigerating capacity, power consumption and EER at environment temperature of 43 °C were 8.1%, -9.5% and 20%, respectively. The unit with condensate water could greatly improve the performance of air conditioning in high environment temperatures.

The effect of variation of extra fan condenser and engine speed to COP of mobile air conditioners

Efforts to increase coefficient of performance (COP) of Mobile Air Conditioners (MAC) still continue to be done, including by increasing the extra fan condenser speed. The problem is whether it can improve the COP, it needs to be tested further. This study focuses to examine the effect of extra fan condenser and engine speed variations to COP. This study was conducted on a MAC engine stand which able to measure the pressure and temperature of MAC system. The data measured at inlet compressor (P1, T1), outlet compressor (P2, T2), outlet condenser (P3, T3), and outlet expansion valve (P4, T4), at engine speed of 1.000, 1.500, 2.000, 2.500 and 3.000 rotation per minute (RPM), respectively with variations extra fan condenser speed of 0.15, 1.74, and 2.22 m/sec. The data was plotted on p-h diagram to obtain enthalpy value, so that obtained COP value by calculation. The major result obtained are the variations of extra fan condenser and engine speed had an effect on the COP. The highest COP (4.48) was achieved at an engine speed of 2,000 RPM with extra fan condenser speed 2.22 m/sec. Increasing extra fan condenser speed causes better cooling at condenser and cooling effect on the evaporator.

Study of a polymer ejector design and manufacturing approach for a mobile air conditioning

• Design and manufacturing approach of a polymer ejector for a mobile air conditioning. • Selection of suitable materials for the application with the refrigerant R1234yf. • FEM analyzes of the ejector design under the conditions of a refrigeration cycle. • Experimental comparison of a steel and a polymer ejector. Polymer ejectors manufactured with injection molding offer a low cost and lightweight design for automotive applications compared to traditional metal designs. New materials need to be resistant against the refrigerant R1234yf and withstand the pressure under operating conditions of a mobile air conditioning. In this paper, a material research selects possible material candidates for a polymer ejector. A FEM simulation investigates the stability and deformation of the ejector when using a polymer material instead of the usual stainless steel solution. A selective laser sintering (SLS) printed polyamide 12 ejector is benchmarked in an enhanced vapor-compression refrigeration cycle against a stainless steel prototype on a test bench. Both ejectors implement the expected pressure levels and show a good pressure recovery rate. However, the new polyamide 12 ejector has a faster decrease of performance from its maximum efficiency. The difference in the ejector performance is expected to be caused by a larger manufacturing tolerance in the SLS printing, leading to a larger nozzle diameter. The design of a polymer ejector is successfully tested, offering new applications for the ejector technology in the automotive industry.

How the coldest local thermal sensation affects overall thermal sensation after turning on the air conditioning—Evidence from chamber experiments

To explore how the coldest local thermal sensation (LTS) affects the overall thermal sensation (OTS) after initiating air conditioner, three experimental scenarios (29 → 23 °C, 29 → 25 °C and 29 → 27 °C) were created to simulate the real circumstances in buildings with split air conditioner (SAC). 29 young students were recruited. The skin temperature of 10 body segments along with the LTS of 6 body segments and OTS were measured continuously. Results showed that the foot demonstrated the coldest sensation and the largest skin temperature change, and it exerted stronger influence on the OTS than other body segments. However, the dominance of the LTS of the foot over the OTS showed great dependence on air conditioner set point temperature and air conditioning duration. Moreover, the two aspects of air-conditioner use behavior interacted with each other when affecting the approaching degree of the OTS toward the LTS of the foot. Based on developing and validating models, differences in the approaching degree change trend over air conditioning duration under different set point temperatures were observed, and then the turning point for the set point temperature between the two change trends was identified. When tset<26°C, the OTS quickly approached the LTS of the foot and surpassed it over time. When tset≥26°C, the approaching speed significantly reduced. The time-varying and temperature-varying characteristics of the relationship between the OTS and the LTS of the foot provided new insight for understanding air-conditioner use behavior in SAC buildings.

A Computer Tool for Modelling CO2 Emissions in Driving Tests for Vehicles with Diesel Engines

The dynamic development of transport in recent decades reflects the level of economic development in the world. The transport sector today is one of the main barriers to the achievement of the European Union’s climate protection objectives. More and more restrictive legal regulations define permissible emission limits for the amounts of toxic substances emitted into the atmosphere. Numerical CO2 modeling tools are one way to replace costly on-road testing. Driving cycles, which are an approximation of the vehicle’s on-road operating conditions, are the basis of any vehicle approval procedure. The paper presents a computer tool that uses neural networks to simulate driving tests. Data obtained from tests on the Mercedes E350 chassis dynamometer were used for the construction of the neural model. All the collected operational parameters of the vehicle, which are the input data for the built model, were used to create simulation control runs for driving tests: Environmental Protection Agency, Supplemental Federal Test Procedure, Highway Fuel Economy Driving Schedule, Federal Test Procedure, New European Driving Cycle, Random Cycle Low, Random Cycle High, Mobile Air Conditioning Test Procedure, Common Artemis Driving Cycles, Worldwide Harmonized Light-Duty Vehicle Test Procedure. Using the developed computer simulation tool, the impact on CO2 emissions was analyzed in the context of driving tests of four types of fuels: Diesel, Fatty Acid Methyl Esters, rapeseed oil, butanol (butyl alcohol). As a result of the processing of this same computer tool, mass consumption of fuels and CO2 emissions were analyzed in driving tests for the given analyzed vehicle.

Performance evaluation of hydrocarbon and its blend in split packaged inverter operated air conditioner

Hydrocarbons are being considered as an energy efficient alternative substance to HCFC-22 in ACs. Better thermo physical properties of HCs results higher energy efficiency in split air conditioners than HCFC-22. However, safety of HC substances needs to be addressed when it is used in ACs. This paper focus on a typical inverter operated SAC with 5.2 kW nominal cooling capacity for performance evaluation. Various tests have been carried out on SAC in well-equipped psychrometric test chamber maintaining test conditions as prescribed in Indian Standard (BIS 1391 part-1) for full capacity and half capacity of test unit. Initially HCFC-22 was tested to establish baseline performance. HCs chosen are HC-290 and its blend (50% HC-290 and 50% HC-1270 by weight) were tested for as a drop-in replacement for HCFC-22. Indian SEER of SAC with HC-290/HC-1270 blend achieved was 4.91 as against 5.11 for HC-290. For HC-290 and HC-290/HC-1270 blend, ISSER is about 20.2% and 15.5% higher respectively than HCFC-22.

Thermodynamic Analysis of Split Air Conditioner Using Energy and Exergy Viewpoint with Low GWP Refrigerants Alternative to R410A

In this paper, a comparative thermodynamic analysis on energy and exergy viewpoint is done on different low global warming potential (GWP) refrigerants to find the possible alternative of high GWP refrigerant R410A. R410A is used nowadays in air conditioning systems due to its ozone-friendly characteristic as zero ozone depletion potential (ODP=0) but it has high GWP (GWP=1924) that leads to global warming. Now a day’s global warming is considered to be one of the critical aspects when environmental protection is taken into consideration and researchers from every corner of the globe are working to find refrigerants that not only have zero ODP but it has low GWP too. In this analysis, four prospect refrigerants namely R32, R447A, R447B, and R452B have been studied to find their suitability to replace R410A on different performance criteria as the coefficient of performance (COP), power consumption, exergy efficiency, and exergy destruction. Thermodynamic properties of the studied refrigerants have been taken from the Genetron Properties 1.4 software. The result indicates that all the studied refrigerants have better performance characteristics compared to R410A but R447A has maximum COP and exergy efficiency along with the least total exergy destruction that makes it a possible alternate of R410A.

Performance analysis of domed roof integrated with earth-to-air heat exchanger system to meet thermal comfort conditions in buildings

In the present study, an integrated cooling system consisting an earth-to-air heat exchanger (EAHE) and a domed roof is investigated numerically to meet the thermal comfort conditions and supply the cooling demand for a building. Simulation of airflow in the EAHE and a test room with the domed roof is performed with ANSYS FLUENT software three-dimensionally, and the thermal behavior of the system is modeled with the code developed in MATLAB software. Furthermore, for verifying the numerical results of EAHE modeling, an experimental study is conducted. The impact of both geometric and environmental parameters on the system performance is also investigated. The obtained results reveal that the system is capable of providing thermal comfort conditions, according to adaptive thermal comfort standard (ATCS), for the test room with a maximum cooling demand of about 1000 W alone and without consuming electric energy by using three pipes with a length of 35 m and a diameter of 0.4 m. The application of the proposed system instead of the split inverter air conditioner and the evaporative cooler to provide a similar cooling load can reduce the electrical energy consumption up to 0.360 kW h, and 0.200 kW h, respectively. In addition, the environmental analysis indicates that the utilization of this system instead of the split inverter air conditioner and evaporative air cooler with similar capacities leads to respective 361.89 kg and 216.06 kg reduction in CO2 emissions for summer months. Finally, the application of the proposed integrated system for a two-story building with domed roof is evaluated. The results show the ability of the system to provide thermal comfort for the two-story building with a maximum cooling demand of approximately 300 W for each floor using two pipes with a length of 35 m and a diameter of 0.4 m.

Review and experimental study on performance improvement of split air conditioner by reducing inlet air temperature to the ODU

Split Air Conditioners (ACs) are more commonly use now a days in residential and commercial buildings for achieving thermal comfort in all seasons. Split ACs works on well-known VCR (Vapour Compression Refrigeration) cycle. Split ACs used more in summer season and due to high outside temperature condenser pressure in a VCR cycle and ultimately result in to high electricity consumption. One of the way to reduce energy consumption of Split ACs and increase cooling capacity is reduce air temperature entering to the condenser in ODU using evaporative cooling principle. In this paper detailed review have been carried out for the improvement of split air conditioner performance and experimental study conducted on Split AC (0.8 TR cooling capacity) with and without evaporative cooling pad at ODU. Evaporative cooling pad material and thickness have been varied to analyse their effects on cooling capacity and coefficient of performance (COP) of Split AC. Out of the PVC, Grass and Cellulose cooling pad of same thickness 150 mm, cellulose cooling pad at ODU of Split AC results about 2 bar reduction in condenser pressure and 1.5 KWH energy saving for 10 hours of operation in a day. Split AC with 100 mm thick cooling pad of cellulose material at ODU results in to approximately 16% increase in overall COP, 10.8 % increase in cooling capacity and 4.6 % reduction in power consumption and at 32°C DBT and about 35% RH outdoor weather condition.

Suppression of disproportionation reaction of HFO-1123 using inhibitors

Abstract Trifluoroethene (HFO-1123) has a very low global warming potential (GWP) and ozone depletion potential (ODP); thus, it has been proposed as a next-generation refrigerant. However, a short circuit in a motor under high temperature and pressure conditions may cause a disproportionation reaction of HFO-1123. Therefore, to commercialize a split air conditioner using HFO-1123, it is necessary to develop a technology to suppress this disproportionation reaction. In this study, disproportionation experiments were conducted under various temperature and pressure conditions. Variations in pressure, temperature, and input energy were recorded. Using a discharge method, we experimentally determined the threshold pressure of the disproportionation reaction. The disproportionation reaction was photographed using two high-speed cameras, and the flame temperature was measured using the two-color temperature radiometry method. The experiment was conducted using R32 and trifluoroiodomethane (R13I1) as the disproportionation reaction inhibitors, and the suppression effect of the disproportionation reaction was evaluated.

Performance comparison of tube and plate-fin circular and elliptic heat exchangers for HVAC-R systems

This work seeks to improve HVAC-R systems technology by experimentally quantifying energy efficiency increase due to the utilization of elliptic instead of circular tubes in the evaporator. For that, a performance comparison is conducted in a 12000-Btu h−1 split air conditioning system. A finned elliptic tubes evaporator was built in the laboratory, based on the optimized geometry found in previous studies published by the same authors for maximum heat transfer density, i.e., S/2b, e,φfopt≅(0.5, 0.6, 0.094), which accounts for tube-to-tube spacings, tube eccentricity and fin density. The finned circular tubes evaporator (e = 1) was also built in the laboratory to replace the original component made by the equipment manufacturer, with S/2b = S/D, e,φfopt≅(0.5, 1, 0.094), i.e., same tube-to-tube spacings, and fin density as the elliptic evaporator. In this way, the two heat exchangers had the same shape to minimize their geometric differences. Additionally, the evaporators were designed to fit in the same evaporator unit as the original evaporator, with exactly the same external shape and number of tubes, thus the refrigerant circuit was the same, being the only component to be replaced in the experimental apparatus for comparing the two systems. The objective functions utilized for performance comparisons were the coefficient of performance, COP, and the dimensionless heat transfer volumetric density, q~. The experiment was carried out through the operation of the system installed as specified by the manufacturer, with the evaporation unit placed inside a test chamber, and the condenser unit in a surrounding environmentally controlled ambient. The compressor energy consumption was directly measured by an electric power meter. The results indicate that the optimized elliptic in comparison to the circular geometry shows a gain of approximately 13 and 15% in Q̇evap, 9 and 13.5% in COP, 12.5% and 19.2% in qevap″, 13% and 16.6% in h¯, 14.3% and 16.7% in St¯, and 11.4 and 14.5% in q~, for Re2b = 1030 and 2060, respectively. In conclusion, the sole gain due to the elliptic with respect to the circular geometry is significant. An empirical correlation was introduced to extend the validity range of a previous one to 1030⩽ReD=Re2b⩽10600, and was made available for design engineers in order to predict heat transfer performance. The more the heat exchanger geometry departs from the optimized one, i.e., in terms of tube-to-tube spacings and fin density, the higher the gains are expected to be.

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.

Heat recovery design and test for the secondary loop heat pump MAC system

Abstract In mobile air conditioning (MAC) systems, the secondary loop (SL) structure was usually adopted when using flammable refrigerants such as R1234yf, R290 and R152a. The introduction of intermediate heat exchangers in SL system inevitably increased the temperature difference between the condensation side and the evaporation side, thereby increased the compressor power consumption and caused the performance attenuation. To overcome the attenuation, this study designed a heat recovery device which collects the waste heat from the passenger compartment to increase the evaporation temperature and reduce the compressor power consumption. Validation experiments were completed in a secondary loop heat pump (SLHP) MAC system using R152a and was compared with a baseline direct expansion (DX) system. According to experimental results, under the -10 °C outdoor temperature, the SLHP system showed performance attenuation compared with the DX system. With the increase in indoor temperature, the attenuation gradually increased to 8.96% at the indoor temperature of 20 °C. In this case, a heat recovery design was used in the SLHP system, which increased the coefficient of performance (COP) by 9.29% compared with the original SLHP system and achieved similar performance to the DX system.

Analysis of Air Quality in A Laboratory Equipped with Split Air Conditioning System

Analysis of Air Quality in A Laboratory Equipped `with Split Air Conditioning System - written by Mayuresh Pingale , Kunal Bhavsar published on 2020/10/31 download full article with reference data and citations