Split Unit Research Articles

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

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

Novel metamaterial array-based dual port MIMO antenna using low profile substrate with feature multiband, and high isolation for sub-6G, IoT, and WiMAX applications

This article represents a single-layered two-port MIMO antenna loaded into a compact plane-patterned metamaterial (MTM) structure for a 5G communication system. The antenna operates at three bands to investigate metamaterial properties in addition to diversity parameters, an arrangement of a series of arrays suggested a 2-port design antenna and a circular-shaped split ring resonator unit cell was developed. The design of a single port antenna utilizes 1 × 3 MTM unit cells for each component. This antenna operates within a frequency range ranging from 1 GHz to 15 GHz. Additionally, the suggested MIMO antenna offers a dominant isolation of –55dB. The measurement’s results show that, with an entire antenna size of 112 mm × 26.5 mm and a 3.33 GHz bandwidth, the MIMO antenna is achieved with good efficiency and CCL < 0.35, considerable DG > 9.97dB, ECC < 0.18, and TARC <–9.97. The presented design is suitable for medical imaging, RFID, Bluetooth, Wi-Fi, WiMAX, IOT, satellite communication systems, and the 5G and sub-6 GHz spectrum.

Integrating solar PV systems for energy efficiency in portable cabins: A case study in Kuwait

The rapid growth of energy consumption in densely populated urban areas with limited land space, especially in hot climates, poses significant challenges. The Australian University of Kuwait conducted a study using two portable cabins to explore energy-saving techniques. One cabin integrated an off-grid solar photovoltaic (PV) system to evaluate its impact on grid electricity demands for an airconditioning (AC) cooling system over 9 months, compared to the second cabin without a PV system. The PV system utilized rooftop space with four Monofacial Go Green 350 W/24 V solar panels, an off-grid maximum power point tracker (MPPT) inverter charger 3.5kVA/100A/24 V, and two Gel deep cycle batteries 12 V/200Ah. The PV panels were oriented south at a 30-degree latitude angle, providing power through the MPPT to a 1.5-ton AC split unit for cooling. Findings showed that the cabin with solar PV panels achieved a 24.1 % energy saving and a total CO2 reduction of 129.4 kg, consuming 1,743 kWh over 237 days, compared to 2,296 kWh for the cabin without the PV system. The novelty of this study lies in the integration of off-grid solar PV systems with existing cooling technologies to evaluate potential energy savings and environmental benefits for comprehensive utilization and addressing urban and climate challenges. Enhancements can include flexible room temperature control using advanced systems, optimizing the PV system settings with more efficient AC systems, and connecting the PV system to additional loads like heating/cooling and lighting. These improvements would ensure the comprehensive utilization of captured solar energy in Kuwait and countries with similar climatic conditions throughout the year. Advancements in solar PV panel efficiency and high-intensity flexible PV panels offer opportunities for maximizing solar energy capture in dense residential buildings.

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

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

Impact of Engine Inertia on P2 Mild HEV Fuel Consumption

The energy management system (EMS) of a hybrid electric vehicle (HEV) is an algorithm that determines the power split between the electrical and thermal paths. It defines the operating state of the power sources, i.e., the electric motor (EM) and the internal combustion engine (ICE). It is therefore one of the main factors that can significantly influence the fuel consumption and performance of hybrid vehicles. In the transmission path, the power generated by the ICE is in part employed to accelerate the rotating components of the powertrain, such as the crankshaft, flywheel, gears, and shafts. The main inertial components are the crankshaft and the flywheel. This additional power is significant during high-intensity acceleration. Therefore, the actual engine operation is different from that required by the power split unit. This study focuses on exploring the influence of engine inertia on HEV fuel consumption by developing a controller based on an equivalent consumption minimisation strategy (ECMS) that considers crankshaft and flywheel inertia. The optimal solution obtained by the ECMS controller is refined by incorporating the inertia effect of the main rotating components of the engine into the cost function. This reduces the engine operation during high inertial torque transient phases, resulting in a decrease in vehicle CO2 emissions by 2.34, 2.22, and 1.13 g/km for the UDDS, US06, and WLTC driving cycles, respectively.

Performance of Heat Pipe with Different Working Fluid on Harvesting Wasted Heat Energy at Air Cooled Split Unit

These days, life would not be comfortable without air conditioning which leads to high power consumption due to air conditioning and subsequently increases the carbon footprint. In this research, verification was done on the capability of increasing superheat to improve the performance of the air-cooled split unit and the effect of power consumed by the air conditioning system. The superheat was increased by the heat harvested from the condensing unit of the air-cooled split unit by using a heat pipe. The heat pipe was charged with water, R134a, and R600a with a 100% filling ratio and 90 and 70 inclination angles. K-Type thermocouples, pressure gauges, and power meter were used in data collection. According to data analysis, water with a 90 inclination angle of heat pipe showed the best performance compared to other fluids because of its ability to increase superheat by approximately 32% compared to R600a which increased only approximately 6.5% compared to normal conventional air conditioning. However, it demonstrated that a rise in the superheat at the suction line and a rise in the Coefficient of Performance cannot guarantee a fall in energy usage. This was due to an increase of superheat by the water heat pipe at 90 angle inclination indicating approximately a 28.8% increase in power consumption.

High specificity THz metamaterial-based biosensor for label-free transcription factor detection in melanoma diagnostics

In this work, we present a promising diagnostic tool for melanoma diagnosis. With the proposed terahertz biosensor, it was possible to selectively and sensitively detect the early growth response protein 2, a transcription factor with an increased activity in melanoma cells, from a complex sample of cellular proteins. Fundamentally, the sensor belongs to the frequency selective surface type metamaterials and consists of a two-dimensional array of asymmetrically, doubly split ring resonator unit cells. The single elements are slits in a metallic layer and are complemented by an undercut etch. This allows a selective functionalization of the active area of the sensor and increases the sensitivity towards the target analyte. Hereby, specific detection of a defined transcription factor is feasible.

Wide incidence angle triple-band metamaterial EM wave absorber at X and Ku frequency band applications

ABSTRACT This paper proposes a novel design for a metamaterial-based polarisation insensitive electromagnetic wave absorber for the X- and Ku-frequency bands. The Structure consists of FR4 substrates with modified split-ring resonators operating across three frequencies. Optimal design was achieved by varying the split gap and unit cell size. The proposed design has three absorption peaks (11.6, 14.04, and 16.56 GHz) with 99.88%, 99.72%, and 96.41% absorption efficiencies, respectively. A metamaterial unit cell prototype as well as an array of 13 x 13 unit cells, measuring 170 x 170 mm, were fabricated. Simulated and measured results have shown good agreement. The performance of the metamaterial absorber array is validated through measurement results. Because of its high efficiency and good quality factor, the proposed metamaterial absorber is suited for electromagnetic shielding and sensor applications. Furthermore, simulation results are used to analyse the scalability of the proposed structure.

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.

Hazard Evaluation of Indoor Air Quality in Bank Offices

IAQ is a crucial factor affecting the health, comfort, and productivity of workers, particularly those working in enclosed spaces like bank offices. This study aimed to evaluate the IAQ of a bank office’s operational area and vault by analyzing concentrations of CO2, TVOC, PM10, and PM2.5, as well as temperature, relative humidity, and air movement. Two different ventilation systems were compared to assess their impact on IAQ. The acquired data were statistically analyzed using mean comparison t-tests and hazard ratio analysis. The results revealed that indoor concentrations of PM2.5 and CO2 significantly contribute to the total hazard ratio, indicating the need to reduce their levels below reference values. The study also found that the ventilation system significantly affects indoor air quality, and concentrations of TVOC, CO2, PM10, and PM2.5 in the air are considerable. Significantly, the study found that bank offices with split unit air-conditioners had the highest mean CO2 levels, indicating poor ventilation. Overall, the study reveals that the building, activities, and ventilation in bank offices have a profound influence on IAQ parameters, primarily PM2.5 and CO2. Further research is required to formulate strategies for enhancing IAQ in these settings.

Detection of R290 leaks in RACHP equipment using ultrasonic sensors

There is a growing need for cost-effective leak detection in smaller RACHP equipment that uses R290 and other flammable hydrocarbon refrigerants. Gas detection technology may not be suitable in many cases due to cost and reliability implications whilst detection with system parameters can suffer long response times. Ultrasonic leak detection can be an economical and reliable method. This study presents the development and testing of an ultrasonic leak detector using off-the-shelf components, within a conventional split type wall-mounted air conditioner indoor unit. Depending upon the chosen sensor, a fast and effective response to simulated “small” R290 leaks was achieved. Measurements of potential interference from environmental noise across ultrasonic frequencies suggests false alarms are unlikely. Such a leak detector was found to be potentially effective.

Improved performance for antenna based on a combination of fractal geometry with CSRR

ABSTRACT In this paper, an antenna design method operating at 3.5 GHz for 5G system is presented to improve its performance. The antenna is designed using fractal geometry combined with an imperfectly structured ground plane. In which, the radiation surface has the form of a Minkowski island fractal geometry, and the removed part of the ground is a complementary split ring resonator unit cell. In this design, the substrate material is FR4-epoxy microwave laminates with dielectric constant ϵ = 4.4, loss tangent (tan δ) of 0.02, and h = 1.6 mm thickness used to design the antennas. HFSS software is used in the simulation with the feeding method with a microstrip line. The proposed antenna has a significant performance increase compared to the original microstrip antenna such as reduced about 56% reduction in total size, enhanced 207% bandwidth, increased peak gain to 4.66 dB, and improved radiated efficiency to 89.3%. The physical model of the antenna has been fabricated and measured to verify the correctness of the design.

Explosion risk analysis of R290 leakage into a limited external space

R290 is considered as a promising alternative refrigerant to be used in household air conditioners. To promote the safety application of R290 in air conditioners, a numerical model of refrigerant leakage and diffusion in a limited space was developed, and the reliability of the model was verified by the experimental results on the concentration field of refrigerant leakage from a split air conditioner indoor unit. On this basis, the field strength characteristics of R290 leaking from holes with different diameters and shapes to the external space were investigated, and the explosion risk caused by R290 leakage was further analyzed. The results showed that when R290 leaked from circular leakage holes with different diameters or leakage holes with different shapes to the external space, respectively, Mach disks were formed in the flow area, and the location and size of the Mach disks had certain differences. For circular leakage holes, with the increase of the leakage diameter, the diameter of the Mach disk inside the flow area and the distance from the Mach disk to the leakage hole increased, and the range of the flammable area formed by the leaked R290 in the external space did not change significantly in the horizontal direction, but increased significantly in the vertical direction, which were 0.42 m, 0.84 m, 1.26 m, and 1.7 m, respectively. For leakage holes with the same area but different shapes, the diameter of the Mach disk formed by the gas leaking from the circular hole was larger, and the gas was distributed symmetrically in the horizontal direction with the jet axis as the center in the external space. The gas leaking from the triangular hole was approximately distributed in a triangular shape, and then it diffused along the three centerlines of the triangle. The gas leaking from the square hole diffused along the diagonal of the square in the horizontal direction, and finally the flow area gradually changed from a square to a circle. The gas leaking from the rectangular slit was elliptically distributed in the external space, and the gas mainly diffused along the long axis direction of the ellipse, and the diffusion of the short axis direction was not significant. The range of the flammable area formed by the gas leaking from holes of different shapes did not change significantly in the external space.

Experimental evaluation for potential drop in refrigerants under high-ambient conditions

Compliance with the Kyoto Protocol and United Nations Sustainable Development Goals requires nations to lower greenhouse gas emissions. Air conditioners, as contributors to direct and indirect emissions of greenhouse gases, can play a major role in limiting global warming to 1.5 °C above pre-industrial levels. Nations classified as Article Five parties, including 147 nations, are required to completely phase out Hydrochlorofluorocarbons including R-22 in 2040. Some of these nations reside in extremely hot climates, and new refrigerants perform poorly under hot weather conditions. While the time is ticking to the phaseout, transitional solutions can be used to move away from R-22 to facilitate the phase-down, especially for units that are still in service.In this paper, a comparative experimental assessment of R453A and R458A as drop-in replacements for R22 is presented. This study aims to evaluate the performance of the two refrigerants to assess their suitability for countries residing in hot climates during the transitional phase-out and phase-down of refrigerants. R22 is used as the baseline refrigerant because it is widely used in developing nations and performs well under high ambient temperatures, reaching as high as 50 °C. Six ambient temperatures (35 °C, 40 °C, 46 °C, 48 °C, 50 °C, and 52 °C) were tested to evaluate the performance of a concealed ducted split air-conditioning unit. The unit rated cooling capacity is 10.39 kW at 48 °C. The measured cooling capacity in comparison to that of R22 was between 87 % and 96 % and 88 % to 96 % for R453A and R458A, respectively, over the tested range of temperatures. The coefficient of performance compared to the baseline showed degradation of 6 %–17 % and 3–10 % for R435A and R458A, respectively. The compression ratio increased by 9 % to 15 % on average for both tested alternative refrigerants over the tested temperature range. It is concluded that R458A performs well as a drop-in alternative refrigerant to R22 and surpasses that of R453A, as it showed slightly less deviation in coefficient of performance.

Experimental Findings and Analysis of a Split Unit Evaporative Cooler for Efficient and Eco-Friendly Cooling Applications

As the global energy demand surges, there is a pressing need to develop energy conservation methods to ensure future comfort requirements are met sustainably. Traditional air conditioners, employing vapor compression refrigeration systems, consume substantial power (around 1.5KW) and entail high costs. Alternatively, evaporative coolers offer a cost-effective and lower-power option for comfort maintenance. However, their drawback lies in the excessive humidity in the cooled air, leading to discomfort for individuals. To address this issue, our article focuses on designing and manufacturing a split cooling unit that efficiently cools the air without increasing its humidity. By recirculating the air through the split unit, we aim to maintain optimal room conditions for comfort. This becomes increasingly vital as inefficient building designs in India contribute to 20-25% of electricity wastage in government buildings, resulting in significant annual energy-related financial losses. Conventional heating, ventilation, and air conditioning (HVAC) systems further exacerbate the problem, consuming about 50% of building energy, mostly sourced from fossil fuels, rendering them environmentally unfriendly and unsustainable. Our split cooling unit seeks to provide an eco-friendly and sustainable solution to tackle this energy challenge.

Quarry dust waste-based cementitious composites – A comprehensive review

The bulk generation of quarry dust (QD) from quarries, aggregates, and decorative stone plants, is a serious environmental issue. However, QD has the potential to provide eco-economic and technical merits when incorporated in the construction products. This review provides current investigations on the development of QD-based cementitious material. Constituent materials, preparation techniques, measurable attributes, and potential uses were all compiled in this study. The ongoing study must be expanded to encompass additional building applications and intensified in terms of processing methods and researched qualities. More specifically, this research reviews and discusses the findings of concrete fresh properties, such as workability, flowability, and setting time, as well as hardened concrete properties, such as compressive strength, split tensile strength, flexural strength, drying shrinkage, unit weight, mass loss and ultrasonic pulse velocity. Besides, durability properties were reviewed, such as water permeability, chloride permeability, water absorption, and acid attack. Further, an overview on the microstructure and thermal properties of QD concrete were provided. QD is useful in enhancing the workability of concrete. This paper covers recommendations and observations for future research.

Depth-Wise Split Unit Coding Order for Video Compression

In this paper, we propose a depth-wise flexible block processing method called split unit coding order (SUCO) for video coding. Conventionally, block-based image and video compression frameworks always apply raster scans to process blocks in order from left to right. Owing to the fixed coding order, the available information for prediction in the coding blocks is limited to adjacent blocks on the left and top. To address the limitations of block-based images and video compression frameworks, the proposed SUCO provides more flexibility in handling coding block sequences than predicted on the left and top, and thus coding blocks can take advantage of adjacent right information, such as reconstructed pixels and motion information. The flexibility is achieved by depth-wise signaling of preferred coding order for the given partitions. The experiment results demonstrate that the proposed SUCO can effectively improve the coding efficiency of both intra and inter prediction in the latest video coding standards.

Outdoor unit split fan noise prediction using a hybrid lighthill analogy method

Requirements of outdoor units and split HVAC systems have been increasing with system performance over the years. Since fans are the primary source of noise in these systems, selecting a fan that can meet the thermal requirements and at the same time produce lower level of noise is the most effective way of designing a quieter system. Fan suppliers normally provide fan sound characteristics at a certain distance from the fan at a rated RPM. This information is not sufficient to paint a holistic picture of the aero-acoustic phenomena that can produce unwanted tones during operation. Thus, a Model-Based Design (MBD) approach is applied in the design process during which different concepts are tried in modeling before being tested. This paper discusses a new approach in implementing Lighthill analogy method to capture the tonal and broadband noise characteristics of an outdoor split unit. This method allows for more accurate results compared to FW-H and faster results compared to a direct aero-acoustic CFD simulation. This paper shows a novel signal processing method for fan noise. Tonal and broadband results are separated and processed separately. This allows to capture accurately the tones while smoothing out unrealistic fluctuations in Sound Pressure Level (SPL) at high frequencies occurring because of the limited sampling time.

Heating/Cooling Fresh Air Using Hot/Cold Exhaust Air of Heating, Ventilating, and Air Conditioning Systems

This paper suggests a heat recovery concept that is based on preheating/precooling the cold/hot fresh outside air by means of the relatively hot/cold exhaust air in winter/summer weather conditions. To investigate the feasibility of such a concept, an experimental setup is established to simulate conditions similar to an All-Air HVAC system. The prototype consists of a 6.7-m3 air-conditioned chamber by means of a split unit of 5.3-kW capacity. The heat recovery module consists of a duct system that is used to reroute the exhaust air from a conditioned chamber to flow through the fin side of a fin-and-tube heat exchanger of crossflow type. At the same time, outside, fresh air is flowing through the tube side of the fin-and-tube heat exchanger. A parametric study is performed to assess the amount of heat that can be recovered by varying the mass flow rates on both the duct and heat exchanger sides. The results show that up to 200 W of power can be saved for an exhaust flow rate of 0.1 kg/s and a fresh, outdoor air flow rate of 0.05 kg/s. Environmentally speaking, this leads to a reduction in production of about 1 tons of CO2 per year when the system operates 24 h/day. From an economic point of view, the system is able to return its price after 1.5 years when it is used 24 h per day during hot days at 196-W thermal recovery, whereas it requires at least 6.3 years when it is used during cold days at a 60-W thermal recovery rate, which, in both cases, represents a duration less than the lifespan of an air conditioner.

A Preliminary Assessment of Size-Fractionated Microplastics in Indoor Aerosol-Kuwait's Baseline.

The omnipresence of microplastic (MP) in various environmental samples, including aerosols, has raised public health concerns; however, there is presently very limited information on MPs in indoor aerosol. This paper presents a unique dataset where smaller MPs have been sampled using a six-stage cascade impactor from indoor environments in Kuwait. The MP concentration in the indoor air varied between 3.2 and 27.1 particles m−3, and the relative MP concentration decreased linearly from the lowest to the highest size fraction. A significant effect of location was observed for the total number of MPs (F2,14 = 5.80, p = 0.02) and the inhalable fraction (F2,14 = 8.38, p = 0.005), while location had no effect on the respirable fraction (F2,14 = 0.54, p = 0.60). A significant effect of the type of air conditioning used was also observed for the total number of MPs (F2,19 = 5.58, p = 0.01) and the inhalable fraction (F2,19 = 6.45, p = 0.008), while location had no effect on the respirable fraction (F2,19 = 1.30, p = 0.30). For the total number of MPs and the inhalable fraction, the concentration was significantly higher for the split unit air-conditioning as compared to the central air-conditioning plants. The presence/absence of carpets had no significant effect on the MP concentrations (total: F1,19 = 4.08, p = 0.06; inhalable: F1,19 = 3.03, p = 0.10; respirable: F1,19 = 4.27, p = 0.05). The shape was dominantly fibers, with few fragments in lower size fractions. These datasets represent the first baseline information for Kuwait, and the smaller MPs in all the samples further underscore the need to develop standardized protocols of MP collection in the ≤2.5 µm fraction that can have more conspicuous health implications.