Air Conditioning Units Research Articles

Design and performance evaluation of a multi-load and multi-source DC-DC converter for efficient electric vehicle power systems

This paper introduces the design and comprehensive performance evaluation of a novel Multi-Load and Multi-Source DC-DC converter tailored for electric vehicle (EV) power systems. The proposed converter integrates a primary battery power source with a secondary renewable energy source—specifically, solar energy—to enhance overall energy efficiency and reliability in EV applications. Unlike conventional multi-port converters that often suffer from cross-regulation issues and limited scalability, this converter ensures stable power distribution to various EV subsystems, including the motor, air conditioning unit, audio systems, and lighting. A key feature of the design is its ability to independently manage multiple power loads while maintaining isolated outputs, thus eliminating the inductor current imbalance that is common in traditional systems. Experimental validation using a 100 W prototype demonstrated the converter’s ability to deliver stable 24 V and 48 V outputs from a 12 V input, with output voltage deviations kept within ± 1%, significantly improving upon the ± 5% deviations typically seen in existing converters. Furthermore, the system achieved an impressive 93% efficiency under variable load conditions. The modular nature of the converter makes it not only suitable for EV applications but also for a broader range of industries, including renewable energy systems and industrial power supplies. This paper concludes by discussing optimization strategies for future improvements and potential scaling of the technology for commercial use in sustainable energy applications.

Banana slice drying using waste heat from an air conditioner for enhancing performance and sustainability

AbstractAs waste heat dryers (WHD) exhibit conservation of energy with environmental and economic benefits, the direct use of waste hot air rejected from the outdoor unit of a window air conditioning (AC) unit for drying banana slices is demonstrated experimentally in the present research work. For this purpose, a drying chamber was directly coupled to an AC unit (AC‐WHD) and analyzed its performance during banana slice drying by revisiting the concepts of generalized drying curve and drying performance index (DPI). The experimental data set of moisture content ratio obtained with AC‐WHD matched well with the generalized drying curve and the DPI value was found to be 0.999. It was found that the waste air supplied by the AC unit to the drying chamber was hot (≈ 50°C) and 28% dry, which aided the drying process. The thermodynamic performance of AC‐WHD was also evaluated using warm and wet exergy to provide insight into the mechanism of AC‐WHD drying. The exergy based sustainability index was higher while the exergetic destruction coefficient and environmental impact factor were lower for AC‐WHD when compared to literature values of the solar drying method. The findings of this research work indicate the practicality of coupling AC units with dryer units to address sustainable development goals (SDG).

ENERGY AUTOMATION SUPPORTS ENERGY CONSUMPTION INTENSITY IN CLASSROOMS

Automation of energy use to control energy consumption intensity (IKE) in classrooms is carried out using an Arduino Nano-based system. This system utilizes an IR transmitter to send signals to the air conditioning unit, a servo motor to position the IR transmitter to the appropriate air conditioning unit, a relay to control the lights, and a Real-Time Clock (RTC) module for scheduling based on a specified schedule. The main goal is to prevent energy waste and ensure comfort by turning on and off the air conditioning unit and lights according to a preset schedule. This automatic scheduling includes time setting, transmitter IR control, servo motor, relay control, and LCD. Programmed scheduling ensures that the air conditioner and lights only turn on when needed, while the LCD provides real-time information about the status of the air conditioner and lights. With this automation, the system helps reduce excessive energy consumption, drives significant energy savings, and creates a comfortable and energy-efficient learning environment. The automatic monitoring and regulation system also allows users to focus more on teaching and learning activities without having to worry about manual settings for air conditioning and lights.

An automatic and efficient fault diagnosis strategy for air conditioning units by combining attention mechanisms

The air conditioning system is a very important energy-consuming device in the field of construction. Timely troubleshooting of air conditioning chillers is an important aspect of reducing building energy consumption. Aiming at the problems of many model parameters, large amount of calculation and strong dependence of diagnostic performance on input features in data-driven diagnostic methods, this paper proposes an efficient fault diagnosis strategy combining RepVGG network and SENet attention mechanism. The multi-parameter feature signal is converted into a two-dimensional matrix to obtain multiple feature images. Based on the SENet attention mechanism, the multi-channel weights of the images are extracted, and the weighted feature image is input into the RepVGG network for feature depth mining and classification. Therefore, the method proposed in this paper greatly reduces the calculation amount of parameters, improves the representativeness of signal features to faults and the efficiency of model training. The effectiveness of the method is validated using the ASHRAE RP-1043 chiller unit dataset. The results show that the accuracy of this method reaches 96.55%, which is significantly better than the comparison methods PSO-ELM(96.4%), DT(95.1%), RepVGG(91.6%), ELM(87.6%) and BP(80.8%).

Numerical investigation of high temperature heat pump integrated hybrid cooling system

Over 67 % of the energy demand within the pharmaceutical and semiconductor industries is for their cleanrooms, driven by stringent temperature and humidity control requirements. Despite high energy usage, heating, ventilation, and air-conditioning (HVAC) units consisting of conventional vapor compression systems (CVCS) are favoured for their simplicity. Hybrid cooling systems (HCS) offer potential efficiency gains by separating latent and sensible loads. Still, reliance on fossil-fuel-fired or electric heaters to regenerate the desiccant makes it energy intensive and reduces CO2 mitigation benefits. This study explores high-temperature heat pumps to simultaneously cool process air and heat regeneration air, thereby using multiple benefits. Heat pumps with condensing temperatures of 80 °C, 90 °C, and 120 °C and an ejector-enhanced trans-critical CO2 heat pump were compared with CVCS and HCS. The 120-bu and CO2HP configurations demonstrated a system COP of 2.94 and 3.22, respectively, surpassing CVCS, which has a system COP of 1.44. These setups achieved CO2 emission reduction of 51 % and 55.2 %, compared to CVCS, respectively.

Real-time optimal hierarchy control of HVAC system with maximized ancillary service support in smart buildings: An experimental approach

This article proposes a real-time optimum control algorithm for Heating, Ventilation, and Air Conditioning (HVAC) units of a commercial building aimed to maximize the ancillary power available for frequency regulation services. First, the prediction of energy consumption of air conditioning zones using long short-term memory (LSTM) is achieved, which helps forecast the aggregated regulation capacity bid of the building in the energy markets. Furthermore, to minimize energy costs and thermal discomfort of building dwellers, an optimization algorithm is designed considering the day-ahead electricity tariffs. Moreover, using installed sensors in a lab-scaled hardware prototype, the proposed algorithm is also shown to be capable of interacting with a Building Energy Management System (BEMS) and investigating the electrical and thermal properties of the HVAC unit. The BEMS controller uses an ethernet protocol to interface with the sensors installed at various operational points throughout the HVAC system. The optimal operation of the HVAC system has been executed with the real-time thermal feedback system, which counterbalances the uncertain thermal load or renewable power availability in the building confronted in real-time operation. The simulation results show the performance of the Artificial Neural Network (ANN) based compressor model in deep learning integrated with the other components of the HVAC unit and thermal model of the air-conditioning zone. Finally, the experimental results display the real-time implementation of multiple thermal and electrical conditions within the proposed control scheme of the HVAC unit. This shows the potential of ancillary services capacity through commercial buildings can be maximized with flexible loads and thereby help in power grid support.

Improvement of thermal environment in the outdoor atrium by employing the spray system

Outdoor atriums have recently been applied with increasing frequency for natural illumination, but they produce a harsh thermal environment easily in summer. Moreover, overheating of the outdoor atrium necessitates air-conditioning to moderate indoor thermal comfort. Simultaneously, the substantial heat emissions from air-conditioning outdoor units worsen the outdoor thermal environment, creating a vicious cycle. Traditional passive evaporative methods involving water and greenery, while capable of regulating the thermal environment, suffer from low evaporative efficiency and pose significant challenges. To improve thermal environment in outdoor atriums, the spray system was employed due to its high cooling efficiency, especially in open or semi-open spaces. In this study, a comparative experiment was conducted to evaluate the effectiveness of using a spray system for evaporative cooling in open outdoor spaces. Furthermore, employing high-efficiency evaporative cooling through spraying to disrupt the vicious cycle of indoor and outdoor thermal environments. The dual goals include regulating indoor and outdoor thermal conditions while also mitigating the local heat island effect. Temperature and humidity distribution within the atrium and adjacent hallways were monitored, along with the impact on air-conditioning operation consumption in neighboring offices. Results showed that the spray system significantly improved the thermal environment in the outdoor atrium, reducing the average and peak air temperatures by 0.94–2.83 °C and 2.92–5.21 °C, respectively. It also resulted in a drop in the average temperature by 0.56–1.62 °C and the peak temperature by 2.31–3.25 °C in adjacent hallways. This effectively eased the issue of overheating in these areas while raising the comfort level in adjacent office spaces. The predicted mean vote decreased from 1.46 to 0.87, indicating a significant improvement in thermal environment in neighboring offices. Furthermore, the daily energy consumption was reduced by 10.6–12.4% in neighboring offices. This study provided the valuable guidance for improving thermal environments within outdoor atrium.

Machine learning approach for predicting personal thermal comfort in air conditioning offices in Malaysia

The existing machine learning based models for personal thermal comfort have traditionally focused on physiological and psychological variations among occupants, and the spatial parameters have been largely overlooked. Field measurements are conducted to collect data and synthesise the collective findings for optimal spatial positioning based on a 24 °C setpoint. The objective of the present study is to investigate and compare the prediction performance made by the machine learning models for personal indoor thermal comfort in air-conditioned office environments using non-spatial parameters (NSP) and spatial parameters (SP). The data was collected from the respondents at four different occupants. A comprehensive data set of NSP and SP is comprised of machine learning models in predicting different thermal comfort situations are Decision Trees (DT), Random Forests (RF), Support Vector Machines (SVM), K-Nearest Neighbours (KNN), Naive Bayes (NB), and Neural Networks (NN). Results indicate a substantial improvement in the accuracy prediction with the Random Forest algorithm outperforming others, enhancing overall accuracy by 38.6 % with spatial parameters for thermal sensation vote (TSV). However, the SVM algorithm improves 50 % accuracy by considering SP input for thermal comfort (TC). Spatial parameters, including the distance between windows and air conditioning units, emerge as critical factors influencing thermal comfort.

Exergo-enviro-economic analyses of solar energy based novel air cooling system

Implementation of heating, ventilation, and air conditioning units in buildings for space cooling represents a passive method for achieving thermal comfort and reducing power consumption. This paper introduces solar energy assisted in-direct evaporative cooling system with a novel multi-passage dry channel. The main objectives are to evaluate exergy variations, sustainability, and total cooling cost based on the inlet conditions for four modes: A, B, C, D (without evaporative cooling, with evaporative cooling, preheating, and preheating with humidification). This comparative study explores thermal performance enhancement of an indirect evaporative cooling system across four operational modes. Mainly, the exergy outlet values increase significantly by 77.39%, while exergy destruction decreases by 54.86%. Both energetic and exergetic coefficient of performances witness remarkable enhancements, with energetic Coefficient of Performance (COP) rising by 321.32%. Exergy efficiency experiences a notable enhancement of 29.974%, and sustainability index shows a consistent upward trend, with a 119.34% increase observed in Mode D compared from Mode A. Entropy generation decreases significantly, indicating improved system efficiency. Total capital cost per unit of cooling capacity decreases notably, highlighting cost savings. These findings underscore the effectiveness of incorporating preheating and humidification processes in optimizing indirect evaporative cooling system performance, emphasizing both exergy efficiency and cost-effectiveness.

A Novel solar-assisted air source heat pump system for urban renewal: Experimental test and numerical simulation

Old residential communities require novel heating solutions to meet heating demands sustainably. In Southern China, current heating systems in old communities have high energy costs and lack sustainability. A potential solution, air source heat pumps (ASHP), have evaporators susceptible to frost accumulation and poor heating performance at low ambient temperatures. This study proposes a hybrid design that uses additional solar thermal energy to improve energy gains from the air source; the innovative serial coupling design increases the air-source temperature by engineering the evaporator of the ASHP as the load-side of the heat exchanger. The novel hybrid design aims to be efficient, cost-effective, and sustainable, satisfying urban redevelopment needs. A prototype of the novel hybrid solar-assisted ASHP system was constructed; various performance parameters were evaluated, and system operation in extreme climates was simulated in TRNSYS. Results indicated that the novel hybrid system had significantly superior heating performance, delivering a 70.1% improvement in heating rate compared to single-source ASHP under lower ambient temperatures (13C). The novel hybrid system also had a high COP value between 5.7 and 6.3, significantly exceeding values of 2.3-3.5 for most air-conditioning units. It demonstrates consistent performance in all simulated climates. It is estimated that the novel hybrid system can save 1000 RMB in annual energy costs for an average Shanghai family and reduce Shanghais CO2 emissions by 4.7 million tons. The novel system addressed limitations of ASHP, optimizing performance while maintaining sustainability, offering a promising solution for urban renewal projects in China.

Determination of Turbulent Prandtl Number for Thermal Fluid Dynamics Simulation of HVAC Unit by Data Assimilation

Abstract Regarding high-precision temperature field prediction of a heating ventilation and air conditioning (HVAC) unit using thermal fluid dynamics simulation, the determination of the turbulent Prandtl number (Prt) was a key issue. In this study, we present an attempt to improve the accuracy of thermal fluid dynamics simulations in HVAC units by adjusting the Prt using data assimilation techniques. First, we simultaneously measured the velocity and temperature in the hot and cold air mixing zone of a simple HVAC model using particle image velocimetry and thermocouples. Second, we coupled data assimilation to the thermal fluid simulation model to determine the Prt in the mixing field. Finally, we proposed two functions of the Prt for high velocity and low velocity regions using multidimensional analysis. In the future, we believe that the Prt functions can be applied to thermal fluid simulations of actual HVAC unit to accurately predict performance without conducting prototype experiments, thereby contributing to reducing development cost and time of HVAC unit.

Comprehensive analysis of waste heat recovery and thermal energy storage integration in air conditioning systems

The proposed work aims to address the challenge of effectively recovering and storing wasted heat in air conditioning (AC) systems, which is crucial for improving energy efficiency and system stability. This study focuses on the comprehensive analysis of a Waste Heat Recovery (WHR) system integrated with Thermal Energy Storage (TES) tanks. A lumped-dynamic thermal model was developed and validated against literature data to accurately simulate the system’s performance. Through a detailed parametric study, the research explores how factors like WHR effectiveness, TES type, PCM type, and TES volume influence the system. The results demonstrate that recovering and storing wasted heat from AC systems significantly enhances operational stability and performance. Notably, increasing WHR effectiveness from 0.55 to 0.85 extends the duration of constant thermal power recovery and also results in higher recovered water temperatures with reduced water pump energy consumption. Furthermore, latent heat storage (PCM tank) extends the duration of stable thermal power recovery by over 61 % compared to sensible storage. Using PCM RT 44HC is more effective for WHR in AC units compared to RT 50 and RT 54HC. Finally, it was shown that increasing PCM tank volume from 2 to 4 m3 improves the duration of constant thermal power recovery by up to 52 % while stabilizing the recovered water temperature.

A comparative study of the potentials of Oman and UAE in condensate water recovery

<p class="MsoNormal" style="text-align: justify; text-justify: inter-ideograph; line-height: 120%; mso-pagination: none; layout-grid-mode: char; mso-layout-grid-align: none; text-autospace: none; margin: 12.0pt 0cm 6.0pt 147.4pt;"><span lang="EN-US" style="font-size: 10.0pt; line-height: 120%; font-family: 'Times New Roman',serif;">Freshwater is essential for everyday activities including drinking, irrigation, farming and many industrial processes. However, freshwater is less than 1% of the total water resources in the planet and, therefore, it is considered a very valuable commodity. Limited resources and growing needs for freshwater triggered global exploration for alternatives to produce enough freshwater for human needs. Today’s most widely used methods to produce freshwater is desalination. However, critical appraisal of the desalination procedures raised the alarm about </span><span lang="EN-GB" style="font-size: 10.0pt; line-height: 120%; font-family: 'Times New Roman',serif; mso-fareast-font-family: 宋体; mso-font-width: 105%; mso-font-kerning: 0pt; mso-ligatures: none; mso-ansi-language: EN-GB;">sustainability</span><span lang="EN-US" style="font-size: 10.0pt; line-height: 120%; font-family: 'Times New Roman',serif;"> of desalination and indicated that significant research is needed to develop alternative green resources of freshwater. Countries in the Gulf area such as Oman and UAE experience hot and humid climates and use air-conditioning units to achieve acceptable comfort levels and create a </span><span lang="EN-GB" style="font-size: 10.0pt; line-height: 120%; font-family: 'Times New Roman',serif; mso-fareast-font-family: 宋体; mso-font-width: 105%; mso-font-kerning: 0pt; mso-ligatures: none; mso-ansi-language: EN-GB;">healthier</span><span lang="EN-US" style="font-size: 10.0pt; line-height: 120%; font-family: 'Times New Roman',serif;"> indoor environment. The cooling process release a large amount of condensate water through cooling coils. This amount of water is usually considered as a problem rather than opportunity and, thus, is wasted into municipal sewerage systems via a system of drainage pipes. This alternative source can be utilized in various drainage, irrigation, and cooling applications to reduce the use of considerable amount of municipal potable water. This source not only takes part in controlling the water scarcity, but also in saving energy and to reducing the carbon footprint. This paper focus on highlighting the opportunities for Oman and UAE to utilize the condensate water from air-conditioning process, as a viable alternative source of green </span><span lang="EN-GB" style="font-size: 10.0pt; line-height: 120%; font-family: 'Times New Roman',serif; mso-fareast-font-family: 宋体; mso-font-width: 105%; mso-font-kerning: 0pt; mso-ligatures: none; mso-ansi-language: EN-GB;">fresh</span><span lang="EN-US" style="font-size: 10.0pt; line-height: 120%; font-family: 'Times New Roman',serif;"> water. It provides a comparison of the potentials of both countries to collect condensate water, based on meteorological data, location and climate. It was concluded that both countries have great potentials and opportunities to utilize this wasted resource. </span></p>

A Computational Study on Utilizing Phase Change Material With a Condenser to Improve air Conditioning System Performance

ABSTRACTThe efficacy of employing multiple cylindrical phase change materials (PCM) to enhance the performance of an air conditioning (AC) unit is examined in this study. The objective of the present study is to examine the effects of combining an AC unit with a cylindrical PCM container configuration on the PCM discharge process and the performance of the AC system. The procedure involves the connection of a heat exchanger with a cold energy storage PCM to the condenser of the AC. During the daytime, the warm surrounding air is cooled and then transmitted to the AC unit's condenser. Four different turbulence models, that is, the SST , standard , Realizable and RNG have been considered for the present computational study. The investigation has been performed for different air flow rates, that is, 33.6, 42, and 49 for a constant inlet air temperature of 308.15 K. The present outcomes indicate that as the flow rate rises, the air temperature inside the domain increases and the solid PCM starts melting. It is noted that complete discharging time for multi‐cylindrical PCM reduces as the air flow rate rises which are around 13.36, 11.03, and 9.94 h for airflow rates of 33.6, 42, and 49 , respectively. The maximum achieved increase in the COP is around 94.49%, 88.68%, and 87.57% at airflow rates of 33.6, 42, and 49 L/s, respectively, for the multi‐cylindrical PCM throughout the summer. It is found that for the same temperature, as the airflow rate rises, the consumed power saving rises.

How to cool a warming world? – The potential of photovoltaic green cooling with natural refrigerants in sunbelt countries

The study investigates the economic feasibility of photovoltaic-powered air-conditioning (AC) systems in thirteen different sunbelt countries. Two different technical solutions have been analysed: (i) hybrid (partially PV powered, grid-connected) and (ii) off-grid (fully PV powered, no grid connection). These two solutions have been studied for three different locations in each country, namely minimum, average and maximum annual global solar irradiation on the horizontal. Lastly, each solution and location has been examined for application in the residential and commercial sector. All solar-based air-conditioning scenarios use high efficiency AC appliances with R290 as refrigerant (Global Warming Potential – GWP of 1) and have been compared against a base-case scenario using AC units with moderate efficiency AC appliances with conventional R410a refrigerant (GWP of 2088) and 100 % grid electricity supply. The scope of the study is to identify the economic potential of solar PV cooling technologies. Levelized Cost of Electricity (LCOE) and Net Present Value (NPV) have been calculated for each scenario as part of the comparative analysis. It was found that hybrid photovoltaic-based air-conditioning for a residential house has a financial advantage over grid-based air-conditioning in eleven out of thirteen countries investigated. Exceptions are Ghana and Vietnam. Off-grid photovoltaic-based air-conditioning for residential houses is only economically feasible in five out of thirteen countries, namely Costa Rica, Iran, Grenada, Philippines and Thailand. Hybrid photovoltaic-based air-conditioning for a small commercial building has a financial advantage over grid-based air-conditioning in ten of thirteen countries, except in Colombia, Ghana and Iran. Off-grid photovoltaic-based air-conditioning for a small commercial building is only feasible in China, Grenada, Kenya and Philippines.

Evaluating radon concentration and temporal correction factors in residential and workplace buildings: A comparison of passive and active methods

Effective mitigation of the health impacts of radon exposure begins with accurate measurement of this environmental contaminant. Typically, radon surveys require measurements over a period of several months. This process involves the application of temporal correction factors (TCF). Disparities in indoor radon concentration (IRC) are evident across building types. While the integrated technique has traditionally been considered the most reliable for measuring IRC, the active method is becoming more prevalent due to the availability of commercial radon measurement instruments. The aim of this study is to compare IRC using passive (CR-39) and active (ICA device) methods across 69 indoor spaces, including 35 workplaces and 34 residential buildings. The investigation was conducted over a span of one year and included 966 CR-39 detectors that were replaced every 3 and 6 months, respectively, to assess seasonal fluctuations and facilitate the computation of TCF. Statistically significant differences in IRC were observed between residential and workplace buildings (p < 0.001). Among workplaces, educational and research institutions showed the highest average IRC (166 Bq/m3), while hospitals exhibited the lowest (25 Bq/m3). Significant differences in TCF were found between the two measurement methods (p < 0.05), making TCF specific to the passive method inapplicable to active method. Moreover, distinctions between workplace and residential buildings, including the presence of air conditioning units and differing occupancy patterns, lead to substantial differences in both IRC (p < 0.001) and TCF. The assessment of radon exposure based on room occupancy duration revealed substantial variations: workplaces showed lower actual exposure (62 Bq/m3 vs. 75 Bq/m3, p < 0.001), while residential settings, particularly at night, displayed higher exposure (278 Bq/m3 vs. 245 Bq/m3, p = 0.02) than integrated measurements suggest. Continuous monitoring systems offer critical insights into true radon exposure levels.

Benefits and challenges in deployment of low global warming potential R290 refrigerant for room air conditioning equipment in California

High global warming potential gases (“high GWP”) are the fastest growing sector of greenhouse gas emissions in the world and in California and are primarily used as refrigerant gases in refrigeration and cooling equipment. Hydrofluorocarbons (HFCs) refrigerants are the dominant type of high GWP gases with GWP values thousands of times larger than CO2 on a 100-year timescale. Refrigerant-grade propane (“R290”) has a very low GWP (GWP = 3.3) with good thermodynamic properties and good cooling equipment performance but the flammability of any leaked refrigerant makes equipment design, handling, and maintenance critical factors to manage. This paper focuses on the potential climate benefits and costs of transitioning to R290 refrigerant in small room air conditioning (AC) units, specifically window AC, packaged terminal AC/heat pumps (PTAC/PTHP), and mini-split heat pumps. Overall climate impact for a transition to all three types of air conditioning units in the 2022–2051 timeframe is found to be from 15 to 64 million metric tons of greenhouse gas (GHG) savings in California with a cost of saved CO2eq that ranges from $14.50 per ton of CO2eq saved to −$50.30 per ton of CO2eq saved (net savings) depending on whether the baseline refrigerant is R32 or R410A and depending on the relative energy efficiency for R290 units compared to baseline units.

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.