Air Conditioning Units Research Articles

Development of an IoT-Based Air Conditioning Meter for Real-Time Operational Status

Air conditioning systems have become a staple in households and businesses, particularly in regions with tropical climates, where maintaining indoor comfort is crucial. However, the widespread use of air conditioning units has led to a significant increase in energy consumption, contributing to higher electricity bills and environmental concerns, particularly in terms of carbon emissions. Traditional air conditioning units often operate without real-time monitoring, leading to inefficiencies and unnecessary energy use. In response to these challenges, there has been a growing interest in the development of smart, energy-efficient solutions that can monitor and control air conditioning systems remotely. The advent of the Internet of Things (IoT) has opened up new possibilities for integrating sensors and microcontrollers with cloud-based platforms, enabling real-time data collection and analysis. This research builds on these advancements by developing an IoT-based meter designed to monitor the operational status of air conditioning units, providing users with immediate feedback and enabling more efficient energy management.

Numerical analysis and evaluation of a tropical classroom for thermal comfort, indoor air quality, and energy consumption using ventilation with air-to-air total heat recovery system (MemHEX)

ABSTRACT Lecture rooms in the Philippines often experience unfavourable temperatures and elevated carbon dioxide (CO2) concentrations, impacting the well-being, health, and learning efficiency of both students and educators. This research seeks to evaluate the thermal comfort, indoor air quality, and energy usage in a standard Philippine lecture room by implementing a membrane-type total heat exchanger (MemHEX). The research used computational fluid dynamics (CFD) simulations, which were validated by field measurements and showed the effectiveness of the MemHEX. Energy consumption was modelled using EnergyPlus to compare potential impacts of various ventilation approaches. Room temperature and humidity fall short of thermal comfort standards, suggesting the need for a higher-capacity air conditioning unit (ACU). Average CO2 concentration exceeds 1000 ppm, signalling a demand for ventilation. Post-MemHEX installation, temperature and humidity slightly rise with increased air changes per hour (ACH), introducing warm outdoor air. Indoor air quality improves with rising ACH, reducing CO2 levels by exchanging fresh outdoor air. Comparing mechanical ventilation and MemHEX reveals MemHEX as more energy-efficient, maintaining better indoor conditions. These findings provide valuable insights for the field of research by demonstrating the feasibility and benefits of using MemHEX to improve the indoor environment and energy efficiency of a typical Philippine classroom.

Performance Assessment of Cold Thermal Storage-Based Building Air-Conditioning Layouts for Different Climates

In this work, a detailed study is done to explore thermal features and operational aspects of thermal energy storage (TES)-based air-conditioning strategies. Three approaches, such as traditional air-conditioning, radiant air-conditioning unit (RACU) and desiccant-incorporated radiant air-conditioning unit (DRACU) have been undertaken by assimilating them with the TES. A validated triple-floor building with 10,690 m2 floor space is studied under warm-humid, composite, and hot-dry climates. Validated strategies with TES and non-TES based techniques were then compared for exploring parametric trends defined by temperature, humidity, electricity consumption, thermal load, coefficient of performance (COP), and other aspects. In comparison with traditional non-TES strategy, results disclose that electrical energy savings offered by the TES vary between 7.6 and 11.4% for the traditional system, 4.8 and 8.6% for RACU, and 3.8 and 6.1% for DRACU, based on the subjected climate. For all of the considered systems, it is further projected that adoption of the TES although causes an increased thermal energy gain, but the same causes declination in the chiller’s overall cooling load, as well as improves the net COP. Both of these factors contribute in reducing the electricity consumption. The integration of TES has revealed opposite trends for the radiant chiller attached to RACU and DRACU.

Optimal classification of radiant time series for cooling load calculation of building air-conditioning systems

Building cooling load is caused by complex thermal effect. Design cooling load determines the capacity of air-conditioning assembly units and systems to maintain stable thermal environment and high operating efficiency. The radiant time series method (RTSM) is applicable for design cooling load calculation in engineering application. The radiant time series (RTS) should precisely match various room types by improving their accuracy and practicality. The room construction types require more explicit identification. This study proposes RTS classification method based on heat balance method (HBM) and CatBoost to obtain the representative RTSs for various room types. A new quantitative indicator, interior surface heat storage coefficient, is introduced to quantify the construction type. An accuracy evaluation is performed on the representative RTSs and design cooling loads calculated using them. The results show that interior wall type, ceiling type and floor type are important parameters for RTS classification. Compared to the HBM, the representative RTSs cause relative deviations of design cooling loads within 5 % for over 90 % of the room samples, with mean deviations within 2 %. This has demonstrated accurate RTS classification in this study. The appropriate representative RTSs with refined construction type can ensure accurate cooling load calculation and facilitate extensive application.

Increasing the Efficacy of an Air Conditioning Unit by Utilizing Phase Change Material With Cylindrical Configuration

ABSTRACTThe goal of the current study is to determine how the SST and the standard turbulence models prediction on PCM with cylindrical configuration affect AC performance and PCM discharging when coupled with an AC unit. For simulation, 308.15 K and 318.15 K, the inflow air temperature has been considered with a fixed 33.6 L/s intake air flow rate. The low outside temperature charges the PCMs during the night. During the daytime, heated ambient air is cooled by the PCM heat exchanger before passing over the unit condenser. The present outcomes show that using the standard model, the cylindrical PCM has the lowest time of complete melting. The temperature contours demonstrate that turbulence occurs, particularly at higher temperatures, in the PCM melting zone within the solid region. This implies that there is increased convection in this area. The maximum improved percentage in COP increases as the rising input air temperature for both turbulence models increases. The average power saving of AC at 308.15 K of an input air temperature for 83.33 min is predicted by both the standard and the SST to be 14.0905 W and 14.1089 W, respectively.

Enhancing Air Conditioning System Performance via Dual Phase Change Materials Integration: Seasonal Efficiency and Capsulation Structure Impact

Enhancement of the cooling and heating capabilities of an air conditioning unit (ACU) coupled with a thermal energy storage system of dual phase change materials (PCM) is investigated. The dual PCM, namely SP24E and SP11_gel, are coupled with the ACU outdoor device (condenser/evaporator) during the summer/winter seasons, respectively. Moreover, ACU performance assisted with dual-PCM heat exchanger is compared with a single heat exchanger of SP24E in summer and single heat exchanger of SP11_gel in winter at different PCM capsulation structures (aligned and staggered cylinders). The system dynamic mathematical model is computationally solved using ANSYS software and experimentally validated. Results affirm that charging/discharging periods are minimal for the dual-PCM system and slower for PCM inline cylinder layouts than staggered ones. Inline design yields greater ACU average power savings. In summer, higher inlet air temperature to the PCM system reduces PCM discharging time and ACU power savings, with the opposite effect during winter. ACU COP with PCMs is improved by around 80 % in summer and 40 % in winter, respectively, compared to ACU without PCMs. The maximum average power saving over 4 h of ACU working in summer by single and dual-PCM systems is 21.4 % and 11.8 %, respectively, whereas the results in winter are 18.5 % and 12.8 %, respectively.

Decarbonization of Heating and Cooling Systems of Buildings Located Nearby Surface Water Sources: Case Study

The study was carried out to evaluate theoretically and in laboratory conditions the capacity of a hybrid heating and cooling system that sustainably uses thermal energy extracted from surface waters in order to decarbonize buildings located near water sources. The novelty of the research consists in the realization of two experimental systems, one for the rapid evaluation of the performance of the water–water heat pump heating system and one for the evaluation of the operating behavior of a cooling system with fan coil units. Starting with the heating and cooling demand, and the climatic and hydrological local characteristics, a hybrid system model for the heating and cooling of the analyzed building was established and implemented. The forecasted energy consumption and CO2 emissions for the operation of the new equipment were compared with the historical values of the old systems with which the building was equipped (thermal energy supply from the district heating and cooling system with an air conditioning unit). Also, the results were extrapolated for forecasting the energy potential of the surface waters. The study highlights a percentage reduction in annual energy consumption of 67.71% and CO2 emissions of 80.13% through the implementation of the hybrid system.

Surgical outreach for the Americas: a self-sustainable model for partnership and education.

It is estimated that up to 28% of global disease burden is surgical with hernias representing a unique challenge as the only definitive treatment is surgery. Surgical Outreach for the Americas (SOfA) is a nongovernmental organization focused primarily on alleviating the disease burden of inguinal and umbilical hernias in Central America. We present the experience of SOfA, a model focused on partnership and education. SOfA was established in 2009 to help individuals recover from ailments that are obstacles to working and independent living. Over the past 15years, SOfA has partnered with local healthcare providers in the Dominican Republic, El Salvador, Honduras, and Belize. The SOfA team consists of surgeons, surgery residents, triage physicians, an anesthesiologist, anesthetists, operating room nurses, recovery nurses, a pediatric critical care physician, sterile processing technicians, interpreters, and a team coordinator. Critical partnerships required include the CMO, internal medicine, general surgery, nursing, rural health coordinators and surgical training programs at public hospitals. SOfA has completed 24 trips, performing 2074 procedures on 1792 patients. 71.4% of procedures were hernia repairs. To enhance sustainability of healthcare delivery, SOfA has partnered with the local facilities through capital improvements to include OR tables, OR lights, anesthesia machines, monitors, hospital beds, stretchers, sterilizers, air conditioning units, and electrosurgical generators. A lecture series and curriculum on perioperative care, anesthesia, anatomy, and operative technique is delivered. Local surgery residents and medical students participated in patient care, learning alongside SOfA teammates. Recently, SOfA has partnered with SAGES Global Affairs Committee to implement a virtual Global Laparoscopic Advancement Program, a simulation-based laparoscopic training curriculum for surgeons in El Salvador. A sustainable partnership to facilitate surgical care in low resource settings requires longitudinal, collaborative relationships, and investments in capital improvements, education, and partnership with local healthcare providers, institutions, and training programs.

Use of Semi-Indirect Evaporative Cooling in HVAC systems: experimental study

This study investigates the application of a Semi-Indirect Evaporative Cooler (SIEC) to develop a Decarbonised Evaporative-Based Air Conditioning System (DEBACS). The research aims to show the benefit of using the SIEC in combination with a traditional Air Conditioning Unit to enhance the energy efficiency of an HVAC system. The SIEC, constructed from ceramic material, operates in both dry and wet modes. By spraying water on the inner side, it functions as an efficient air-to-air recuperator, with the ceramic material improving water distribution and device performance. The SIEC device has been experimentally tested. Tests were conducted in both dry and wet modes across three airflow rates and three temperature levels. Moreover, a simple model that describes the SIEC behaviour in general operative conditions has been derived. Results indicated that under optimal conditions (lowest supply airflow), the SIEC achieved an efficiency ratio between 50 % and 70 % in dry mode, and nearly 100 % in wet mode, with the wet mode improving efficiency ratio by 30–50 %. These findings underscore the potential of the ceramic SIEC device as an effective technology for air conditioning systems, promoting energy efficiency, compliance with EPBD standards, and significant decarbonisation in the HVAC sector.

Experimental Study on the Performance of an Air Conditioning Unit with a Baffled Indirect Evaporative Cooler

Indirect evaporative coolers (IECs) use the latent heat of water evaporation to cool air. This system has the advantage of operating at low power without a compressor and does not increase the absolute humidity of the air. However, an IEC is difficult to use on its own because its cooling capacity is limited by the theoretical constraint of the wet-bulb temperature of the ambient air. Therefore, an air conditioning unit (ACU) was integrated with an IEC and experimentally evaluated in this study. The dry and wet channels of the IEC were integrated with an ACU evaporator and a condenser, unlike previous studies where IECs were integrated solely with either an evaporator or a condenser. This reduced the cooling load on the evaporator and helped the condenser to dissipate heat to improve the performance of the existing ACU. In addition, the IEC was equipped with baffles to improve its performance. To assess the extent of the performance improvement due to integration with the IEC, comparisons were also performed under the same experimental conditions with an ACU only. The results showed that under conditions with an indoor temperature of 32 °C, integrating the IEC with the ACU increased the average cooling capacity by 13.1% and decreased the average power consumption by 8.60% during the test period, compared to using only the ACU. Consequently, the average coefficient of performance (COP) increased by 19.5% compared to using only the ACU under the same conditions.

Real-Time Implementable Integrated Energy and Cabin Temperature Management for Battery Life Extension in Electric Vehicles

Among many emerging technologies, battery electric vehicles (BEVs) have emerged as a prominent and highly supported solution to stringent emissions regulations. However, despite their increasing popularity, key challenges that might jeopardize their further spread are the lack of charging infrastructure, battery life degradation, and the discrepancy between the actual and promised all-electric driving range. The primary focus of this paper is to formulate an integrated energy and thermal comfort management (IETM) strategy. This strategy optimally manages the electrical energy required by the heating, ventilation, and air conditioning (HVAC) unit, the most impacting auxiliary in terms of battery load, to minimize battery life degradation over any specific drive cycle while ensuring the actual cabin temperature hovers within the permissible tolerance limit from the reference cabin temperature and the driver-requested traction power is always satisfied. This work incorporates a state-of-health (SOH) estimation model, a high-fidelity cabin thermodynamics model, and an HVAC model into the forward-approach simulation model of a commercially available BEV to showcase the impact and efficacy of the proposed IETM strategy for enhancing battery longevity. The instantaneous optimization problem of IETM is solved by the golden-section search method leveraging the convexity of the objective function. Simulated results under different driving scenarios show that the improvement brought by the proposed ITEM controller can minimize battery health degradation by up to 4.5% and energy consumption by up to 2.8% while maintaining the cabin temperature deviation within permissible limits from the reference temperature.

Self-detection of thermal ambient parameters for air-conditioned space by learning operation data and self-prediction of indoor temperature and power consumption

For efficient energy use of air conditioning unit (AC), there is a need to find an optimal control method for operation. To deduce an optimal control algorithm, indoor temperature and power consumption need to be predicted according to given operating conditions. Among the key factors, the thermal ambient parameters such as thermal resistances of the operation sites are most difficult to identify. This study proposed a method for an AC to deduce these parameters for itself by learning operation data obtained from the embedded sensors and autonomously predict indoor temperature and power consumption by solving the transient energy conservation equation incorporating refrigeration cycle simulation. A novel aspect of this study is that the AC can autonomously perceive thermal ambient parameters of its surroundings and utilize these parameters to predict indoor temperature variations and power consumption. These data could be fed back to the control software of the AC in real time. To validate the proposed method, experiments were conducted in model house test facility using a real air-conditioner, and the results were compared with the simulation results. It was confirmed that the time to reach the air temperature setpoint was within 3 min and the power consumption could be predicted within 9 %.

Heavy metals and microbial assessment of air conditioning condensate water in Jeddah city-Saudi Arabia: concept of sustainable water resources

The demand for water is rising worldwide, especially in Saudi Arabia, where the existing water sources are barely sufficient to meet the present requirements. Condensates from air-conditioning units can be invested as an economical and supportive source of available water resources, which can be considered within global water supply accounts. The aim of the present study is to examine the possibility of recovering condensate water from air conditioner (AC) systems by determining the quantity and quality of AC water generated by either split or window AC systems. The results showed that split air conditioner systems were more effective than window-type air conditioners in generating condensate water in terms of quantity and quality. There was a significant correlation between the humidity and water content. The results indicate that the annual amount of water generated was 8,725 L for window AC and 20,614 L for split AC. The recorded levels of all elements in the water samples obtained from both the window and split air conditioning units, including pH, TDS, EC, PO4-3, Cl-, SO4-2, COD, and heavy metals, were found to be within the acceptable thresholds set for both drinking water and irrigation purposes. Bacteria were only present in three water samples from the window AC, and all were non-pathogenic. Utilizing air conditioner condensate as a strategic measure can address the issue of water scarcity in Saudi Arabia’s agricultural and industrial sectors. The findings of this study are extremely relevant and opportune, especially given the growing concerns about water scarcity and the need to conserve resources. By demonstrating that the HVAC water condensate is clean and safe for consumption, this study adds to our understanding of how we can make better use of available resources.

PARTICLE SWARM OPTIMIZATION AND CFD ANALYSIS OF A HEAT SINK FOR FORCED CONVECTIVE COOLING OF A DC/AC INVERTER

Power inverters play a crucial role in converting DC voltage and current to AC voltage and current. Its efficient operation relies on effective thermal management of the semiconductor devices, such as the IRF 3205 MOSFET chip which facilitate the switching operations to prevent thermo-mechanical stress that could to failure. This research developed and optimize a heat sink for an IRF 3205 MOSFET chip in a 3.5 KVA power inverter, using the Particle Swarm Optimization technique and experimented with a 3.5 KVA 24 V power inverter operating a 1.5HP air-conditioning unit. The heat sink geometry has 26 fins, 4 mm fin thickness, 40 mm fin height, 3 mm fin spacing, 2 mm fin base thickness, 179 mm length, 80 mm width and a thermal resistance of 60.75 °C/W. The thermal performance was evaluated using ANSYS Computational Fluid Dynamics (CFD) and results showed maximum base temperature of 65.85°C and experimental temperature of 64°C after two hours of steady operation dissipating heat of 45W. The results from both numerical and experimental data demonstrate the effectiveness of the optimized heat sink in maintaining the chip's temperature below its maximum working threshold of 170°C.

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.

Design optimization of the cooling systems with PCM-to-air heat exchanger for the energy saving of the residential buildings

Driven by a rapid surge in cooling demand in buildings, the energy consumption dedicated to cooling has experienced remarkable growth. To address this challenge, the adoption of latent heat thermal energy storage utilizing phase change materials (PCM) has gained significant momentum in recent years. This paper presents the design and evaluation of an integrated latent heat thermal energy storage (ILHTES) system tailored for residential buildings. This system integrates a PCM-to-air heat exchanger (PAHX) with an air conditioning unit. Modelica language is utilized to develop a numerical model for the ILHTES system. The heat transfer model of the PAHX is developed and validated using existing literature data. To simulate the dynamic behavior and energy consumption of the residential building, the open-source library AixLib is adopted. The developed ILHTES system model is used for the optimization of key design variables, including the PCM slab thickness and air flow rate, based on the results of long-term simulations covering the entire cooling season. Evaluation of the energy saving potential of the optimized ILHTES systems is carried out in comparison to conventional air conditioning systems, considering various climatic conditions in five European cities. The results highlight the profound impact of PCM types on the Energy Saving Ratio (ESR) throughout the entire cooling season. Among the four commercially available PCMs examined—RT27, RT25, RT20, and RT18—RT25 consistently outperforms the others. Across all five cities investigated, using RT25 leads to a minimum ESR of 16% in Catania and a maximum ESR of 44.7% in Stockholm for the entire cooling season.

Improving Thermal Performance in Data Centers Based on Numerical Simulations

Improving Thermal Performance in Data Centers Based on Numerical Simulations

Assessment of performance and sustainability of waste heat dryer coupled with air conditioner unit during drying of banana slices

The present work presents the effective application of waste heat rejected from window air conditioning (AC) in a waste heat dryer (WHD) for drying plantain banana slices. The comparison between drying with the waste heat dryer coupled with an AC unit (ACWHD) and a natural convective indirect solar dryer (SD) reveals significant differences in drying kinetics, supply air conditions, and thermodynamic performance. The drying kinetics of banana slices obtained with ACWHD and SD were validated by revisiting the concepts of dryer performance index (DPI) and generalized drying curve. The temperature of the hot air supplied to the drying chamber in ACWHD was 48 °C while the relative humidity of the supply air was below 30 %. The thermodynamic performance assessment revealed that the exergetic efficiency was about 45 % and 16 % for ACWHD and SD respectively. The results of exergy based sustainable index and environment impact factor indicated the potential application of the waste heat of residual air from AC units for drying applications. Thus, the results of the present study imply that this novel idea has appreciable potential for commercialization with large-scale central air conditioning units in commercial complexes and industries where the magnitude of heat rejection will be multi-fold.

Eco-Friendly Energy Efficient Classrooms and Sustainable Campus Strategies: A Case Study on Energy Management and Carbon Footprint Reduction

This research paper presents a comprehensive study on energy management and carbon footprint reduction in an educational institutional campus. It focuses on implementing energy-efficient technologies and practices to minimize energy consumption and environmental impact. The study encompasses four cases, each addressing different aspects of energy use in a university setting, including the installation of LED lighting, programmable remote switches, and high-efficiency air conditioning systems. The methodology involves a detailed analysis of energy consumption patterns, using smart energy meters and theoretical calculations. Case I establishes a baseline energy consumption, while subsequent cases implement energy-saving measures. Case II involves replacing traditional tube lights with energy-efficient LED lights, resulting in considerable energy savings. Case III extends these savings further by integrating programmable remote switches mapped with student timetables. Finally, Case IV proposes the replacement of older air conditioning units with 25 SEER models, leading to significant reductions in energy use. The results highlight the effectiveness of these interventions. Case II achieves a 66.67% energy saving, while Case III yields up to 77.78% energy saving in lighting and 33.34% in air conditioning. In Case IV, the adoption of high-efficiency air conditioners can result in a 52% energy saving during teaching weeks. The economic benefits of these measures are substantial, with cost savings per classroom ranging from 7.65% in Case II to 53.46% in Case IV. Moreover, the environmental impact of these energy conservation techniques is substantial. The study reports reductions in carbon emissions from 14.71metric tons of carbon dioxide equivalent (MT CO2e) in base Case I to 6.85 MT CO2e in Case IV. The overall carbon emission reductions for Cases II, III, and IV are 7.61%, 36.37%, and 53.43%, respectively. This study demonstrates the profound impact of integrated energy management strategies in reducing the carbon footprint and energy consumption in educational institutions, offering a model for sustainable and economically viable operations.

Numerical study on the effect of smoke emitted from the vents on the roof of a diesel train on the intake of downstream air-conditioning units

Constrained by economic development and geographical features, numerous railway lines remain unelectrified, underscoring the expansive potential of diesel trains. Diesel engine emissions discharged from the roof of trains pose a challenge as some of the smoke infiltrates the cabin through the intake of roof-mounted air-conditioning units (ACUs). This intrusion diminishes the indoor air quality, posing health risks to passengers and potentially jeopardizing their safety. This study employs the shear stress transport k-omega turbulence model to formulate a multiphase flow model for simulating smoke diffusion in diesel trains. Additionally, we conducted an optimization design to minimize smoke entry into the ACUs. This study defined six cases based on variations in the shape and height of the cover and the spacing of the smoke vents. The results show that the effect of the diffusion characteristics decreased with the cover height. With the progression of airflow diffusion, the effect of the smoke vent structure on the concentration diminished farther from the vents. The minimum smoke mass flow rate into the intake occurred with the vent spacing of 2.14 m and without a cover, resulting in a 57.0% decrease compared with the maximum. Thus, a smoke vent spacing of 2.14 m without a cover was deemed to be the optimal configuration. The research results provide certain engineering guidance significance for the design and operation of train-smoke vent structures.