Efficient Air Conditioning Research Articles

Energy saving of vacuum-based membrane dehumidification with indirect evaporative cooling in a low sensible-heat-ratio building

In hot and humid climates, dehumidification generally consumes more energy than cooling, and conventional mechanical vapor compression system is not efficient for dehumidification. Vacuum-based membrane dehumidification system have been developed as a more environmentally friendly alternative for dehumidification due to non-refrigerant system and isothermal dehumidification process. In this study, a novel hybrid air conditioning system that combines vacuum-based membrane dehumidification with an indirect evaporative cooler for pre-cooling is proposed to achieve efficient air conditioning in building with low sensible heat ratio. The energy performance of the proposed system is investigated by detailed thermodynamic simulations and compared with conventional variable air volume (VAV) system and indirect evaporative pre-coolers combined VAV system. The simulation results show that when the average sensible heat ratio of the space is 0.73 and the COP of the vacuum-based membrane dehumidifier is 1.0, the proposed system can reduce energy consumption by 16.1 % compared to conventional VAV system and by 6.4 % compared to indirect evaporative pre-cooler combined VAV system during the cooling season. The energy performance of the proposed system is significantly affected by the sensible heat ratio of the building and the energy efficiency of the vacuum-based membrane dehumidifier. When the COP of the vacuum-based membrane dehumidifier reaches 2.0, the proposed system can achieve an energy savings of 48.2 % compared to conventional VAV system.

FAN PARAMETER ANALYS OF HEAT PUMP AIR CONDITIONING SYSTEMS WITH DIFFERENT HEAT EXCHANGERS CONFIGURATIONS.

The residential sector accounts for 27% of the EU's total energy consumption, and more than half is used for space conditioning, so improvements in this sector would contribute to achieving the sustainability goals set. Heat pumps (HP) have been presented as a good solution, as they are systems capable of satisfying air-conditioning needs in a more efficient way than systems based on fossil fuels; moreover, the REPowerEU Communication established the objective of doubling the current HP deployment rate in the next years. In this sense, designing and optimizing air conditioning systems is crucial. This study presents a method to determine the power and airflow parameters of a fan in a heat pump air conditioning system. The calculation is performed considering the pressure drop associated with the design of the heat exchangers using the IMST-ART simulation tool. This modeling aims to obtain simulations closer to the real behavior under different design conditions for the development of more efficient air conditioning systems

Artificial neural networks for predicting the performance of heat pumps with horizontal ground heat exchangers

A Ground Coupled Heat Pump (GCHP) is a highly energy efficient heating, ventilation, and air conditioning (HVAC) system that utilises the ground as the heat source when heating and as the heat sink when cooling. This paper investigates GCHP systems with horizontal Ground Heat Exchangers (GHEs) in the rural industry, exemplifying the technology for poultry (chicken) sheds in Australia. This investigation aims to provide an Artificial Neural Network (ANN) model that can be used for GCHP design at various locations with different climates. To this extent, a Transient System Simulation Tool (TRNSYS) model for a typical horizontal GHE applied in a rural farm was first verified. Using this model, over 700,000 hourly performance data items were obtained, covering over 80 different yearly loading patterns under three different climate conditions. The simulated performance data was then used to train the ANN. As a result, the trained ANN can predict the performance of GCHP systems with identical (multiple) GHEs even under climatic conditions (and locations) that have not been specifically trained for. Unlike other works, the newly introduced ANN model is accurate even with limited types of input data, with high accuracy (less than 5% error in most cases tested). This ANN model is 100 times computationally faster than TRNSYS simulations and 10,000 times faster than finite element models.

Heating and cooling challenges for electric vehicles: A comprehensive experimental study

An efficient mobile air conditioning (MAC) system using a safe and climate-friendly refrigerant is necessary for human comfort, increasing the vehicle’s energy performance, and reducing the fuel/electricity consumption. In the current work, we perform a drop-in experimental comparison for low GWP alternatives to R134a in reversible MAC systems. The study compares two lower global warming potential (GWP) refrigerants; R456A, a non-flammable refrigerant for R134a direct MAC replacement, and R1234yf, an ultra-low GWP and mildly flammable refrigerant that is the standard for new MAC systems. The system’s operational and energy performance is investigated, simulating a wide range of indoor and outdoor steady-state conditions. The measurements are recorded operating a fully monitored vapour compression test rig that uses secondary circuits to set the target conditions. In the heating mode (heat pump), the evaporation temperatures are set at −10 °C, −5 °C, and 0 °C, and condensation temperatures at 40 °C, 50 °C, and 60 °C. In cooling mode (air conditioning), the condensation temperatures are 37.5 °C, 45 °C, and 52.5 °C and are combined with evaporation temperatures of −7.5 °C, 0 °C, and 7.5 °C. In the heating mode, R456A presented a competitive COP to R134a with a reduction of less than 5 %, more remarkable at lower evaporation temperatures. In the cooling mode, R456A showed the lowest COP at a low condensation temperature. R456A and R1234yf COP are comparable at a higher condensation temperature, which suits the T3 climate conditions.

Research on engineering technology of compact thermoacoustic air conditioner for vehicles

Thermoacoustic refrigeration technology presents a promising solution for sustainable and efficient air conditioning in vehicles. However, traditional thermoacoustic systems typically employ rigid resonant tubes, which pose challenges in terms of assembly and spatial layout during experimentation. Additionally, electric heating is predominantly utilized as the heat source in most experimental setups.To address the need for compact thermoacoustic air conditioning systems suitable for vehicle applications, this paper introduces the concept of employing flexible resonant tubes in heat-driven thermoacoustic refrigeration systems. Our study begins by constructing a heat-driven thermoacoustic refrigeration platform designed to simulate real automotive exhaust conditions. The DeltaEC software is employed to optimize the design of each component within the system.Both flexible and rigid resonant tubes are used in experimental research. Our findings reveal that the pressure amplitudes measured from experiments using both types of tubes closely match the simulated sound field. Operating at 8.7 MPa, the cooling capacity of the thermoacoustic system with flexible tube is 3.4 kW at 10 ℃. Using more gentle bending of flexible resonant tubes can reduce small losses caused by bending in rigid resonant tubes. Consequently, under similar working conditions, the cooling capacity generated by the system employing flexible resonant tubes slightly exceeds that of systems employing rigid resonant tubes. Furthermore, our study demonstrates a thermoacoustic conversion efficiency of 20.8 % and a refrigerator refrigeration efficiency of 2.34.These findings provide empirical validation for the use of flexible resonant tubes within vehicle exhaust heat-driven thermoacoustic refrigeration systems. The experimental results clearly demonstrate the ability of vehicle exhaust as a heat source to provide heat for thermoacoustic systems, and the ability of flexible thermoacoustic systems to generate sufficient cooling capacity. Ultimately, this research contributes to the advancement and practical implementation of thermoacoustic air conditioning within vehicles.

Photovoltaic Powered Dual Thermoelectric Air Conditioning System

Abstract: Nowadays energy efficient and environment friendly systems are among the emerging technologies, due to growing concerns about climate change and sustainability. According to the present scenario, the renewable energy resources are becoming the source of energy due to the decrease in non-renewable energy resources (Fossil fuels). So we presented a “Photovoltaic-Powered Dual Thermoelectric Air Conditioning System” that incorporates Peltier modules(thermoelectric material) which works on peltier effect known for their eco-friendly characteristics. Harnessing solar energy through a highefficiency PV array, this system aims to provide efficient and sustainable air conditioning while minimizing the reliance on traditional power sources. The additional benefit of this system is that it provides year round comfort i.e. cooling and heating facility in one system.

Optimal design guidelines for net zero energy residential buildings in cooling-dominated climates: Case study of Ghana

Net zero energy buildings (NZEBs) are regarded as an achievable solution for reducing energy use and carbon emissions in the built environment and addressing climate change. However, the ultimate objective of NZEBs is to enhance the energy performance of buildings by changing how they are designed and constructed. Consequently, identifying cost-effective energy efficiency strategies at the early design stages of buildings has become imperative and often required in several countries. This study describes a systematic analysis approach to optimize the design of residential facilities considering both energy efficiency and renewable energy systems. The design optimization is based on life cycle cost (LCC) analysis, which considers capital and energy costs over the lifecycle of the building. The analysis consistently shows that LCC-based optimal designs significantly reduced the building's annual energy consumption, achieving 34–35% energy-saving across the various climates compared to the baseline case. The most cost-effective energy efficiency measures that proved effective across all the climate zones include north orientation of the building at 180 azimuth degrees, natural ventilation, adequate window-to-wall ratio, minimal façade air leakage (i.e., about 5-7 ACH @50 Pa), and high efficient fans, air conditioning, and dehumidification. The integration of the PV system indicates that the net zero energy (NZE) design for the building is technically feasible and cost-effective across the climate zones considered. The sensitivity analysis further shows that the cost of integrating PV systems is even more cost-effective over a more extended period of the building's lifecycle. The study provides an optimal path for designing NZEBs and offers guidelines to achieve NZE across the building's lifecycle.

Experimental analysis of an innovative geo-exchange system installed on the island of Ischia, in southern Italy

The need to use efficient and eco-friendly air conditioning systems is a fundamental requirement for today’s society. In this context, low and medium enthalpy geothermal energy plays a crucial role. The research and development activities carried out in the present work have made it possible to successfully design and analyze an innovative technology capable of supplying thermal energy to environments without pumping fluid from the subsoil. The proposed system is based on the use of a downhole heat exchanger (DHE). The authors have developed an innovative system for the sustainable use of low and medium enthalpy geothermal energy, installed on the island of Ischia, near Napoli, in southern Italy. The proposed system is based on the use of an ad hoc designed DHE, capable of optimizing the heat transfer with the subsoil, without the need to withdraw fluid from the aquifer. A numerical finite element model was developed to study the interaction between the DHE, the well and the surrounding aquifer. The experimental set-up consists of the heat exchanger and an above ground system, necessary to test the efficiency of the exchanger. The DHE is inserted inside a geothermal well made with a steel casing, equipped with a filtering section in correspondence of the DHE, in order to increase the heat transfer performance due to increased convection with the surrounding aquifer. The experimental data show that the DHE allows to exchange more than 40 kW with the ground, obtaining overall heat transfer coefficient values larger than 450 W/m2 K.

Sensor Based Human Activity Recognition

Abstract: This project presents the design and implementation of a smart home system that harnesses the capabilities of infrared (IR) sensors and temperature sensors. In the contemporary landscape of technological innovation, smart homes offer unparalleled convenience, comfort, and energy efficiency. Leveraging these sensors, our system aims to automate various household tasks while intelligently responding to environmental changes and user preferences. The integration of IR sensors enables motion detection and occupancy sensing, facilitating automatic control of devices such as lighting and security systems. Meanwhile, temperature sensors contribute to efficient heating, ventilation, and air conditioning (HVAC) management by adjusting settings based on ambient conditions. Through a centralized control unit and user-friendly interface, homeowners can monitor and manage their smart home remotely, enhancing their overall living experience. This paper discusses the system's objectives, proposed architecture, implementation details, and potential benefits, underscoring its significance in modernizing residential living spaces.

The air conditioning in the nose of mammals depends on their mass and on their maximal running speed

The nose of the mammals is responsible for filtering, humidifying, and heating the air before entering the lower respiratory tract. This conditioning avoids, notably, dehydration of the bronchial and alveolar mucosa. However, since this conditioning is not perfect, exercising in cold air can induce lung inflammation, both for human and non-human mammals. This work aims to compare the air conditioning in the noses of various mammals during inspiration. We build our study on computational fluid dynamics simulations of the heat exchanges in the lumen of the upper respiratory tract of these mammals. These simulations show that the efficiency of the air conditioning in the nose during inspiration does not relate only to the mass m of the mammal but also to its maximal running speed v. More precisely, the results allow establishing a scaling law relating the efficiency of air conditioning in the nose of mammals to the ratio v/log10(m)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$v/\\log _{10}(m)$$\\end{document}. The simulations also correlate the resistance to the flow in the nose to the efficiency of this air conditioning. The obtained scaling law allows predicting the air temperature at the top of the trachea during inspiration for nasal-breathing mammals, and thus notably for humans of various ages.

Effects of decongestion on nasal cavity air conditioning efficiency: a CFD cohort study

Decongestion reduces blood flow in the nasal turbinates, enlarging the airway lumen. Although the enlarged airspace reduces the trans-nasal inspiratory pressure drop, symptoms of nasal obstruction may relate to nasal cavity air-conditioning. Thus, it is necessary to quantify the efficiency of nasal cavity conditioning of the inhaled air. This study quantifies both overall and regional nasal air-conditioning in a cohort of 10 healthy subjects using computational fluid dynamics simulations before and after nasal decongestion. The 3D virtual geometry model was segmented from magnetic resonance images (MRI). Each subject was under two MRI acquisitions before and after the decongestion condition. The effects of decongestion on nasal cavity air conditioning efficiency were modelled at two inspiratory flowrates: 15 and 30 L min−1 to represent restful and light exercise conditions. Results show inhaled air was both heated and humidified up to 90% of alveolar conditions at the posterior septum. The air-conditioning efficiency of the nasal cavity remained nearly constant between nostril and posterior septum but dropped significantly after posterior septum. In summary, nasal cavity decongestion not only reduces inhaled air added heat by 23% and added moisture content by 19%, but also reduces the air-conditioning efficiency by 35% on average.

Toward residential decarbonization: Analyzing social-psychological drivers of household co-adoption of rooftop solar, electric vehicles, and efficient HVAC systems in Georgia, U.S.

The marketplace of climate solutions has grown considerably. Three technologies, in particular, exhibit strong potential for disruptive change and advancement in the residential sector: electric vehicles (EVs), rooftop photovoltaics (RPVs), and efficient heating, ventilation, and air conditioning (HVAC) systems. Many scholars have studied the adoption of these technologies; we address their co-adoption. Using a survey conducted in Georgia, we examine pro-environmental behavior, risk tolerance, and energy-related knowledge as social-psychological drivers for the co-adoption of RPVs, EVs, and efficient HVACs (including heat pumps). We conclude that some but not all of these drivers are relevant to the adoption and co-adoption of the three transformational climate solutions. Pro-environmental behaviors, for instance, appear to create conditions for “positive spillover,” propelling consumers toward adopting multiple climate solutions, whereas energy knowledge has no clear relationship with co-adoption. At the same time, the = influence of these drivers are unique to different combinations of technologies – one notable example is the significance of risk tolerance when RPV is added to technology bundles. Our paper contributes to the literature by broadening the understanding of the adoption of bundled (or co-adopted) climate solutions.

Barriers to BIM Implementation in the HVAC Industry: An Exploratory Study

In recent times, the rise of urbanization, industrialization, population growth, food security, and the COVID-19 pandemic have led to an increased demand for indoor spaces with efficient air conditioning systems. As a result, there is a growing interest in creating more complex HVAC systems to improve indoor spaces. Building information modeling (BIM) offers numerous benefits to the HVAC industry, such as clash detection, budget and time reductions, and increased efficiency. However, its implementation is currently hindered by various challenges. This research aims to identify the major barriers to BIM implementation in the HVAC industry in Turkey, using a questionnaire survey of 224 domain experts working in 42 different companies across various fields of the HVAC industry. The study utilized several statistical analyses to categorize and prioritize the most critical barriers, including reliability tests, exploratory factor analysis (EFA), confirmatory factor analysis (CFA), the Kaiser–Meyer–Olkin (KMO) test, Bartlett’s test, and ranking of factors (IRI). The results indicate that the “Deficiencies of Infrastructure and Lack of Qualified Personnel (DIP)” factor group constituted the most significant barrier, followed by “Lack of Documentation and Specifications (LDS)”, “Deficiencies of Case Studies and Project Drawings (DCP)”, and “Lack of Motivation and Resistance to BIM (LMR)”. Moreover, our research revealed that 60% of the participants’ companies allocate less than 40% of their budgets to technological infrastructure, which hinders the adoption of BIM. To promote BIM in the HVAC sector, we recommend enhancing personnel capacity building, improving skills and knowledge about BIM, promoting guidelines, and providing free access to documentation for practitioners.

Study on the Applicability of Green and Efficient Refrigeration and Air Conditioning Based on Exhaust Air Heat Recovery Technology

With the sustained and stable development of the national economy, China has stepped into a new stage of green emission reduction. Under the environment of comprehensively promoting the market share of green and efficient refrigeration products, the popularization and use of exhaust air heat recovery technology in different fields will further promote the green and efficient transformation of the refrigeration industry, improve the industry's independent innovation technology, and accelerate the construction of ecological civilization. This project firstly analyzes the research background, reviews domestic and international research, and clarifies the research background and current situation; secondly, it builds a comprehensive evaluation system for green refrigeration development based on three major energy-saving concepts, and measures the level of green refrigeration development in China's first-tier cities; secondly, it applies empirical evidence based on the data of three districts and cities, namely, Beijing, Shanghai, and Guangzhou, in the period of 2011-2021, to analyze the effect of the exhaust heat recovery technology on the development of high-efficiency green refrigeration. Then, based on the data of Beijing, Shanghai and Guangzhou from 2011 to 2021, we use the empirical analysis to analyze the effect of exhaust air heat recovery technology on the development of high-efficiency green refrigeration.

Experimental investigation of a thermo-responsive composite coated heat exchanger for ultra-low grade heat utilization

There is a growing interest in desiccant coated heat exchanger (DCHE)-based systems due to characteristics of isothermal dehumidification and compact structure. To enhance the dehumidification efficiency and reduce the regeneration temperature of DCHE-based systems, a thermo-responsive composite desiccant coated heat exchanger (PSLCHE) was developed. This study focuses on investigating the influence of operating parameters (such as air temperature, relative humidity, regeneration temperature and adsorption/desorption time ratio) on the dynamic performance, average dehumidification capacity (Davg) and thermal coefficient of performance (COPth) of the system. Under the air condition of 30 °C & 60% RH, the PSLCHE demonstrates remarkable performance with the Davg of 7.3 g·kg−1 and COPth of 0.93 at 40 °C. This study provides a route to the design of highly efficient air conditioning systems using thermo-responsive composite for ultra-low grade thermal energy at 40 °C.

A novel data center air conditioner and its application scheme balancing high-efficiency cooling and waste heat recovery: Environmental and economic analysis

Data centers require continuous cooling throughout the year and produce a large amount of low-grade waste heat. How to fully utilize the waste heat while ensuring the efficiency of air conditioning is a problem that needs to be addressed. In this paper, a data center air conditioning with heat recovery function was constructed, and the application scheme of the novel system that considers both high-efficiency cooling and waste heat recovery was proposed. The feasibility analysis was conducted at a data center in Shenyang, with the heat pipe/vapor compression high-efficiency system for cooling and the coal-fired boiler for heating as the comparison scheme. The results show that although adding heat recovery function realizes the utilization of waste heat in data centers, it also increases the energy consumption of the system. The centralized application scheme composed of a single large system reduces annual carbon emissions by 0.9 % and increases operating costs by 12.6 %. The distributed application scheme composed of multiple small systems reduces annual carbon emissions by 14.6 % and reduces operating costs by 3.5 %.

Thermal comfort and retail sales: A big data analysis of extreme temperature's impact on brick-and-mortar stores

The effect of weather on retail sales has long been of great interest to both the business and academic fields. This study investigated the impact of extreme temperatures on brick-and-mortar retail stores in Seoul, Korea. Using a comprehensive credit card transaction dataset, high-resolution weather data, and a semiparametric model, we found a significant increase in sales during extreme temperature events: 4% during heatwaves exceeding 35 °C and 11% during cold spells below −15 °C. This finding is supported by the thermal comfort hypothesis in retail sales, which suggests that consumers are driven to temperature-controlled indoor environments and are inclined to purchase products that provide thermal comfort, such as hot or cold beverages. As extreme weather events become more frequent owing to climate change, accurate sales forecasting during such conditions becomes crucial for retailers. Insights from our research enable retailers to better predict sales under extreme temperature conditions and to strategize accordingly, such as by highlighting thermal comfort products or ensuring optimal indoor temperatures with efficient air conditioning or heating systems.

Development and validation of a model for an air-to-air air conditioner

Air conditioning units are responsible for a significant amount of global warming, with demand predicted to triple by 2050. Mathematical models aid in designing energy efficient air conditioners that can contribute to climate change mitigation. This study presents a steady-state model for a air-to-air air conditioner. The proposed model can assist in reducing the number of experiments and optimizing the efficiency of air conditioning systems. It utilizes a bottom-up approach to solve for compressor, condenser, capillary tube, and evaporator sub-models. The compressor is modelled using polynomial equations to determine refrigerant mass flow rate and power consumption based on operating temperatures. Heat exchanger models are solved using finite volume approach and reliable correlations are used for void fraction, friction factor, and heat transfer coefficient calculations. The closing equations are the mass conservation, i.e. constant refrigerant charge, and the equivalence between the mass flow rate sucked by the compressor and the one that flows through the capillary tube, while the evaporating and condensing pressures are the independent variables. The capillary tube is modelled using semiempirical correlations. The model is validated against experimental data at various operating conditions and shows a ±7% agreement for predicted cooling capacity.

Factors influencing purchase intention towards energy efficient air conditioners: a study of Indian households

Purpose This study aims to examine the antecedents of purchase intention toward energy efficient air conditioners by incorporating the theory of planned behavior (TPB) with two additional constructs, i.e. environmental concern and personal norms. TPB is one of the most widely used theoretical framework to study consumer behavior. Design/methodology/approach The study applied a quantitative technique using a survey method by distributing self-administered questionnaires among the Indian households who have purchased energy efficient air conditioners in the past six months or had enquired to do so. The study collected data from three select regions: Delhi and NCR, Punjab and Tri-city. The collected data of 424 respondents have been analyzed using confirmatory factor analysis and structural equation modeling. Findings The study posits that normative factors such as subjective norms and personal norms have a relatively higher influence on purchase intention. Despite the significant existence of environmental concern, the study did not find environmental concern directly influencing purchase intention. Research limitations/implications The sample size of the study is too small and pertains to specific regions. Thus, it could hinder the generalizability of the results. Advertisement appeals should be related with enhancement of self-esteem in terms of making responsible and valuable contribution to environment protection through the purchase of energy efficient air conditioner. Originality/value There are a few studies in the Indian context studying consumer’s purchase intention toward energy efficient air conditioners to which this study adds. The study provides an important contribution to marketers in developing strategies for increasing purchase intention toward energy efficient air conditioners in view of their stage in the product life cycle, diffusion of product and influence of normative factors.

Integrated Room Monitoring and Air Conditioning Efficiency Optimization Using ESP-12E Based Sensors and PID Control Automation: A Comprehensive Approach

This study addresses the critical need for efficient room monitoring and air conditioning systems, particularly in educational settings like the STMIK STIKOM Indonesia campus. The paper introduces a novel approach that combines ESP-12E based sensors with Proportional-Integral-Derivative (PID) control automation to optimize air conditioning efficiency. Utilizing an ESP-12E microcontroller, the study designed and implemented a room monitoring tool equipped with DHT22 and BH1750 sensors for accurate measurement of temperature, humidity, and light intensity. We also explores the integration of a PID control system into an existing air conditioning (AC) unit. The PID controller was fine-tuned to maintain a stable indoor temperature of 25oCelsius, even when subjected to external heat loads, such as ten LED lamps. The effectiveness of this system was quantified through real-time monitoring of temperature, humidity, and energy consumption, both pre- and post-implementation. Results indicated a rapid and stable response from the PID controller, achieving an amplitude of 1 within 0.08 seconds, thereby confirming its successful tuning and adaptability. We found that this study has broader implications for enhancing energy efficiency and creating conducive learning environments. However, it is worth noting that the research was conducted under specific conditions, and further studies could explore its applicability in different settings.