Conventional Air Conditioning Research Articles

The Green Cooling Factor: Eco-Innovative Heating, Ventilation, and Air Conditioning Solutions in Building Design

This research investigates the compatibility of conventional air conditioning with the principles of green building, highlighting the need for systems that enhance indoor comfort while aligning with environmental sustainability. Though proficient in regulating indoor temperatures, conventional cooling systems encounter several issues when incorporated into green buildings. These include energy waste, high running costs, and misalignment with eco-friendly practices, which may also lead to detrimental environmental effects and potentially reduce occupant comfort, particularly in retrofit situations. Given the emphasis on sustainability and energy conservation in green buildings, there is a pressing demand for heating, ventilation, and air conditioning (HVAC) solutions that support these goals. This study emphasises the critical need to reconsider traditional HVAC strategies in the face of green building advances. It advocates for the adoption of innovative HVAC technologies designed for eco-efficiency and enhanced comfort. These technologies should integrate seamlessly with sustainable construction, use greener refrigerants, and uphold environmental integrity, driving progress towards a sustainable and occupant-friendly built environment.

Exploring global accessibility of deep ocean water for sea water air conditioning (SWAC) process: Identifying feasibility areas depending on temperature source

Sea Water Air Conditioning (SWAC) technology is a highly efficient alternative to conventional air conditioning system using renewable marine energy to provide cooling to buildings. However, its implementation requires access to Deep Ocean Water (DOW) at 4–5 °C, thus SWAC is only viable in coastal regions. Furthermore, one of the major obstacles to its global development is the investment cost that remains high. This cost is strongly linked to the bathymetry of the installation location as it determines the length of the drawing pipeline, which accounts for the largest share of the investment cost. Knowing the temperature and bathymetry profiles will enable the establishment of the financial viability of SWAC technology in a specific location. This paper presents an analysis identifying areas of feasibility on a worldwide scale for standard SWAC implementation first. Then, it explores an alternative design with a higher drawing point for seawater at 12 °C (coupled with a High Temperature District Cooling), which reduces the cost by shortening the drawing pipeline and allows for more locations to be suitable for this technology. Additionally, the impact of the El Niño/Southern Oscillation (ENSO) is also considered since a shallower drawing point makes it more sensitive to temperature variations.

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

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

Experimental Investigation of Energy-Saving Potential of Ground Source Heat Pump During Peak Hour Operations

Abstract Ground-source heat pump (GSHP) systems have emerged as energy-efficient alternate systems for the conventional Air-Source Air-Conditioning (ASAC) systems for space heating and cooling applications. GSHPs have gained widespread popularity globally and are extensively utilized in residential and commercial buildings. However, in countries like India where both space cooling and heating are required, it becomes essential to evaluate the performance of the GSHP system, especially during peak-hour operation to estimate peak load energy demand. This research paper tries to identify the energy efficiency of the GSHP system during peak-hour operations in comparison to the ASAC system using experimental techniques. Experimental trials were conducted in a laboratory equipped with a single unit of 17.58 kW cooling/heating capacity GSHP system and a 17.57 kW cooling/heating ASAC system (two units of 7.023 kW and 10.548 kW). Experimental trials were conducted in peak summer in the month of June for cooling mode operation and January for heating mode operation for Roorkee weather conditions in the northern part of India. The performance of both systems was compared by defining instantaneous coefficient of performance (COP) and cyclic COP. The instantaneous COP was found to be higher for both the systems during peak-hour cooling and heating mode operations. Energy-saving analysis indicates that the ground-source heat pump system saves 36.85% and 38.65% of electrical energy in cooling and heating modes, respectively, compared to the ASAC system.

Cooling Potential Evaluation of a Ground Heat Exchanger in a Tropical Climate: A Case Study of an Office Building

The main implications of the hot-humid climate characteristics stipulate the need for cooling indoor environments. Ground thermal characteristics can be exploited in the search for sustainable ways to cool the indoor environment. Thus, this work aims to assess the cooling potential of the ground thermal characteristics through a vertical ground heat exchanger (VGHE) in a tropical climate such as Panama City via dynamic simulation. This potential is evaluated in a two-stories office building complying with Panama’s building regulation requirements, where a VGHE system is designed to cover the cooling needs. Since underground temperature data are unavailable, parametric and sensitivity analyses are carried out. For sizing the VGHE, a vertical ground system is chosen since this allows a better configuration in the installation for a building with large cooling demands and eliminates the need for large amounts of land. A difference of 33.52% (4481.4 kWh) in the electricity consumption for cooling was obtained compared to a conventional air conditioning system, which translates into a 770.80$ saving (0.172$/kWh). These results confirm that the system studied for air conditioning is feasible since it could provide positive results in thermal comfort and energy savings for the user.

Experimental and Hybrid Numerical Analytical Approach of an Earth-to-Air Heat Exchanger

Abstract The primary goal of this paper is to assess the thermal behaviour of Earth-to-Air Heat Exchanger (EAHE) under continuous operation mode during the cooling period in warm climatic conditions. An experimental setup was conducted in Biskra University (Algeria) to test the ability to use EAHE as an alternative solution to conventional air conditioning systems. Besides, a transient numerical approach for the flowing air within the EAHE was developed using energy balance equations, discretised by the implicit finite differences method and solved by Thomas method. Furthermore, the transient temperature profile of the soil around the EAHE was investigated in order to determine the adiabatic radius of the soil as a function of the duration of operation. In this context, a transient semi-analytical model was integrated to the air model to estimate the transient EAHE’s performance deterioration. This deterioration is produced by the thermal saturation of the soil, which is influenced by the heat released from the air inside the pipe. Results showed that continuous operation for a duration of four days has minimal impact on the outlet air temperatures due to the implementation of night purging. Furthermore, the design and thermal efficiency of the EAHE are impacted by factors such as higher air velocity and reduced soil thermal conductivity.

Polyphenol-coated hollow fiber system for energy-efficient dehumidification in air-conditioning

Increasing temperatures have worldwide become a high health risk. High humidity aggravates the risk and reduces the comfort perception. Conventional air conditioners produce annually the equivalent of 2150 million carbon dioxide tons per year. Dehumidification is responsible for a large portion of it. Membrane-based dehumidification is energy-efficient since water vapor removal is carried out at isothermal conditions without toxic materials. This work demonstrates a membrane dehumidification system based on industry-ready prototypes containing polymeric hollow fibers coated with a green polyphenol coating, showcasing/exhibiting a remarkable water vapor transport rate with selectivity. Long-term testing proved over a year of operation with only a minimal decline in vapor transport. And the proposed system has 4–5 times higher coefficient of performance (COP) than conventional dehumidifiers, and it is a highly competitive energy-saving device with a low contribution to emissions and a smaller footprint.

Sex-based thermal comfort zones and energy savings in spaces with joint operation of air conditioner and fan

Fan and air conditioner combined systems (FACS) have been demonstrated as a viable alternative to conventional air conditioning systems, providing thermal comfort to occupants while consuming less energy. However, few studies have quantitatively established occupant comfort zones for FACS operation and analyzed its energy saving effects. An experiment was conducted first to develop thermal comfort zone in spaces with FACS operation. As the indoor temperature rises, the upper limit of air speed accepted by occupants increases. Females exhibit an upper comfort range parameter of 29.8 °C and 1.4 m/s, while males demonstrate 29.3 °C and 1.5 m/s. There are noticeable differences in comfort ranges between males and females, especially in cooler conditions. Based on the established comfort zone, energy simulation studies were conducted for most regions of China to investigate the potential energy savings resulting from the implementation of FACS in ASHRAE standard office building. Buildings incorporating FACS demonstrate a reduction in HVAC system energy consumption by more than 16 % when compared to indoor temperature set at 26 °C. In hot summer and warm winter climates, HVAC system energy savings of over 100 GJ/year can be achieved using FACS for the standard building. Considering sex differences in FACS operation leads to additional energy savings.

An Assessment of Long-Term Climate Change on Building Energy in Indonesia

This paper reports on modelling outcomes for improvements to building energy performance in Indonesia. Long-term climate effects due to building energy demand and carbon emissions are also considered. The global change assessment model (GCAM) was used to generate the related end-user building energy data, including socioeconomics, for urban areas of Indonesia. As a comprehensive study, the total life cycle of carbon in the building sector and the concept of zero-carbon buildings, including energy efficiency, zero-emissions electricity and fuel-switching options, were considered. Building shell conductance (U-value) of the building envelope, floor area ratio (FAR), air conditioner (AC) efficiency, electrical appliance (APL) efficiency, rooftop photovoltaic (PV) performance and ground source heat pump (GSHP) systems were considered as parameters to mitigate carbon emissions under the operational energy category in the GCAM. Carbon mitigation associated with the cement production process was considered in the raw material category. Urban population and labour productivity in Indonesia were used as base inputs with projected growth rates to 2050 determined from the available literature. Low growth rate ‘LowRate’ and high growth rate ‘HighRate’ were considered as variable inputs for U-value, FAR, AC efficiency, APLs efficiency and PV capacity factor to model emissions mitigation. The energy consumption of the GSHP was compared to the conventional reverse cycle ACs to identify the potential of the GSHP as a fuel-switching option. In the GCAM, the benchmark (base case scenario) data set was generated based on input parameters (urban population and labour productivity rate) only for the residential building sector in Indonesia. Total potential carbon emissions mitigation was found to be 432 Mt CO2-e for the residential building sector in Indonesia over 2020–2050. It was found that an average of 24% carbon emissions mitigation could be achieved by 2020–2030 and 76% by 2031–2050.

Performance Evaluation of Different Desiccant Matrix Materials Coated with Silica Gel

Excessive cooling of air is required in conventional air conditioning systems to reduce the humidity, leading to the development of desiccant wheel-based air conditioning systems. The desiccant wheel consists of desiccant material which is deposited on matrix material. In this study, aluminum, magnesium alloy, Teflon, and fiberglass have been considered matrix materials of the desiccant wheel. A one-dimensional mathematical model has been developed to evaluate the effect of these matrix materials. The results show that fiberglass can be selected as a suitable matrix material for drying applications because it has maximum moisture removal (MR; 1.92 g/kg) and temperature difference (4.72 °C) at optimal rotational speed, which are desirable for drying. While aluminum can be selected as a suitable matrix material for air conditioning applications because, at the optimal rotational speed, it has lower maximum MR (1.26 g/kg) and temperature difference (3.14 °C) as compared to other matrix materials. As moderate maximum MR and lower temperature difference are the requirements for air conditioning. A similar trend of results has been also obtained for other parameters (volume ratio, regeneration velocity, regeneration temperature, etc.) of this study.

Thermodynamic Performance Enhancement of an Air Conditioner With Dew Point Evaporative Cooler

Abstract The vapor-compression-based conventional split air conditioners (CACs) consume a large portion of total electrical power and pose an alarming threat to global environment. The present work aims to reduce cooling load and power consumption of CAC by employing a dew point evaporative cooler (DPEC). DPEC consists of a counter flow type heat and mass exchanger with alternate layers of dry and wet channels. The intake air is sensibly cooled before entering the cooling room through the evaporator coil of the air conditioner. Also, the working air (a part of outlet air in dry channel), after absorbing sensible heat of intake air and water vapors from the wet channel surface, is allowed to pass across the condenser coils. The intake dry-bulb temperature (T0 = 29–44 °C) and specific humidity (ω0 = 6–22 g/kg) are taken as input parameters. While the cooled air entering the evaporator decreases the cooling load on the conditioned space, the compression work is also reduced due to increased heat transfer in the condenser. The maximum reductions in cooling load and monthly energy consumption at T0 = 44 °C and ω0 = 6 g/kg are found as 59.54% and 340 kW h, respectively. The water consumption for different months of the cooling season varies from 1037.8 L to 2905.95 L. The average energy savings with the DPEC system for hot-dry climate (from April to June) and hot-humid climate (from July to September) of New Delhi, India, are observed to be 479.6 kW h and 79.1 kW h, respectively. The proposed system is found to payback in about 3.37 years.

A comprehensive optimization study of personal cooling radiant desks integrated to HVAC system for energy efficiency and thermal comfort in office buildings

Personal comfort systems (PCS) maintain the occupant's preferred thermal environment and expand his thermal comfort experience under varying environmental conditions. Among PCSs, radiant-based systems are popular due to their comfort and energy efficiency. A personal cooling radiant desk (PCRD) in conjunction with conventional heating, ventilation, and air conditioning (HVAC) has proven to reduce energy costs. A system's energy and thermal performance, however, depends on various factors making it important to identify the optimal design parameters of a PCRD coupled with HVAC system in an office space. To optimize the energy and thermal performance of the PCRD-HVAC system, a numerical/mathematical model is developed simulating different design parameters. The model uses an artificial neural network (ANN), combined with a multi-objective genetic algorithm (MOGA) to identify the optimal design parameters. The decision variables include the supply temperature, the temperature, and the flow rate of chilled water flowing inside the desk. The study's findings show that the optimal design parameters achieved a balance between thermal comfort and energy efficiency. The recommended design parameters result in an annual energy consumption of 3880 kWh and a predicted percentage of dissatisfied individuals (PPD) of 6 %. The experiment is carried out to validate the model showed a maximum relative error of only 12.54 %. The results of this study have important implications for designing sustainable cooling solutions for office spaces in hot climates. The successful optimization of the PCRD system highlights the importance of balancing energy efficiency and thermal comfort in designing sustainable cooling solutions.

Theoretical design and drainage characteristic of a C-type heat exchanger in duct air conditioner

The conventional duct air conditioner typically uses an A-type heat exchanger for indoor units, which has poor drainage behavior under wet conditions. In this research, a C-type heat exchanger is developed for drainage improvement. The innovative design employs a unitary fin and a curved profile instead of the sectional fin and linear profile. Theoretical calculations are conducted, determining that the droplet sliding time on the cycloid is the shortest among the curves. The C-type is then produced and subjected to dynamic dip testing to assess its drainage performance. Results reveal that it achieves steady drainage within 3 s and reduces residual water by 10.9% compared to the A-type. A CFD model is generated to simulate the drainage process, with a calculated deviation of less than 10% for residual water. Finally, the C-type prototype is installed in the duct unit for performance measurement under wet conditions. It exhibits a 7.12% increase in heat transfer capacity and a 12.74% increase in drainage rate under the basic condition. The lower evaporating temperature, higher inlet air temperature, higher relative humidity, and larger air volume flow rate contribute to the more apparent drainage enhancement of the C-type.

Natural ventilation in high-rise office building – Comfort and energy performance

AbstractThe application of natural ventilation strategies in high-rise office buildings is considered one of the most promising trends to address high energy performance and enhance the indoor thermal comfort levels in interior office spaces. In this regard, this study attempts to assess the potential of natural ventilation strategies of a specific, previously investigated, envelope design of a high-rise office building located in a temperate climate zone. Different summer natural ventilation approaches were tested using the building energy simulation program IDA ICE 4.8, evaluating thermal comfort and energy demand. The findings indicated that considerable energy savings can be achieved, compared to conventional mechanical ventilation and air conditioning systems.

Advancements in Liquid Desiccant Technologies: A Comprehensive Review of Materials, Systems, and Applications

Desiccant agents (DAs) have drawn much interest from researchers and businesses because they offer a potential method for lowering environmental impact, increasing energy efficiency, and controlling humidity. As a result, they provide a greener option to conventional air conditioning systems. This review thoroughly analyzes current issues, obstacles, and future advancements in liquid desiccant agents (LDAs) for drying, air conditioning, and dehumidification applications. The importance of LDAs in lowering energy use and greenhouse gas emissions is highlighted, emphasizing their potential for environmentally friendly humidity control. The current review examines key parameters such as novel materials, enhancing desiccant qualities, integration with technologies, and long-term durability while examining recent developments in LDAs and investigating their applications in diverse industries. The main conclusions from the evaluated publications in this review are also highlighted, including developments in LDAs, new applications, and developing research fields. Overall, this review advances knowledge of LDAs and their potential to shift humidity control systems toward sustainability and energy efficiency.

Effect of system configuration on the performance of a hybrid air conditioning system based on R-1234yf

The study presents theoretical results on a hybrid air conditioning system in which the sensible and latent loads are separately managed. The problem studied is significant in view of the growing demand for air conditioning systems globally, and also due to the adverse impact of these systems on global warming. In order to reduce the environmental impact of the air conditioning systems, this study proposes a hybrid system comprised of a vapour compression heat pump and a desiccant wheel. Due to restrictions on high global warming potential (GWP) refrigerants, R-1234yf, a low GWP refrigerant is considered as the working fluid for the heat pump. An enthalpy wheel is included to reduce the ventilation load on the system. The proposed hybrid system’s performance is evaluated using the first and second laws of thermodynamics and psychrometric principles. Results are compared with that of a conventional air conditioning system. Based on the calculated values of component and process wise irreversibility, further modifications to the hybrid system are proposed. These modifications consist of addition of a liquid-to-suction heat exchanger and use of a split condenser. Results show that depending upon the latent load on the conditioned space, the compressor power input can be reduced by as much as 47% using the proposed hybrid system. Compared to the conventional system, the modified hybrid system shows excellent performance under both high as well as low latent loads, whereas the simple hybrid system performs very well in applications involving high latent loads. The work presented is novel as it considers both first and second laws of thermodynamics to arrive at an optimum hybrid system configuration using an environment friendly refrigerant. It is expected that the study will be useful in the development of energy efficient and environment friendly air conditioning systems that operate equally well under low and high latent loads.

Thermodynamic and economic analysis of an integration system of multi-effect desalination (MED) with ice storage based on a heat pump

In this study, an innovative system that combined a heat pump, multi-effect desalination, and ice storage subsystem is proposed. The heat pump provides both thermal energy and cold energy for the system to achieve desalination and ice generation. The performance of the proposed system is compared with the conventional mechanical vapor compression and air conditioning systems. The thermodynamic, economic, and environmental analysis is also carried out of both proposed and conventional systems. Moreover, the impacts of the different refrigerants, the condensation temperature of the first effect, and the different areas are carried out to evaluate the effects of several vital parameters on the proposed system. Results showed that the specific energy consumption for the proposed and conventional systems is 4.71 kWh/t and 8.94 kWh/t, respectively. For the economic performance, the payback period of the proposed system is 3.85 years, while it is 5.90 years for the conventional system. For the environmental performance, the unit profit CO2 emission is 15.50 kg/$ of the proposed system, which is 7.68% lower than the conventional system (16.79 kg/$). Hence, the proposed system shows higher economic and environmental performance.

The design of solar power thermoelectric radiant panel as cooling system in small buildings under tropical climate

The usage of an air–conditioning (AC) system in any building is necessary to maintain its indoor thermal comfort and health. However, this system consumes a lot of energy, while the usage of refrigerant causes irreversible damage to the ozone layer. To solve this problem, a solar thermoelectric radiant panel (PV-TERP) system has a high potential in replacing conventional AC system because it requires no refrigerant and easier to be controlled due to the absence of moving and mechanical parts such as water pumps, compressors, including auxiliary and hydronic pipes. Meanwhile, the usage of solar energy in the PV-TERP system can also help reduce fossil energy consumption and carbon emissions. The main objective of this work is to design a new PV-TERP system for replacing conventional AC systems in buildings located in tropical climate countries, like Malaysia. It is found that the designed PV-TERP system can provide up to 4.84 kW of cooling power, which is about 0.6% higher than the cooling load of targeted rooms. Here, the targeted rooms operate under indoor parameters within the acceptable range of ASHRAE standard-55. The obtained results clearly show that the new design is applicable to be used as a cooling system for the targeted building. In the future, it is then essential to understand the thermal properties and mechanism of the design via simulation process, followed by experimental validation to support the design feasibility. In conclusion, this new design of PV-TERP will lead the path toward expanding renewable energy applications for cooling purposes in sustaining and preserving the environment. HIGHLIGHTS Alternative cooling system in replacing air-conditioning (AC) system for maintaining indoor thermal comfort without harming the environment. Designation of the PV-TERP system as a cooling system for building in a tropical country (Malaysia) under indoor parameters within the acceptable range of ASHRAE Standard-55. The designed PV-TERP is refrigerant-free and operates using renewable energy, which can sustain and preserve the environment for a better future. GRAPHICAL ABSTRACT

A Review of Studies on Heat Transfer in Buildings with Radiant Cooling Systems

Due to their benefits in interior thermal comfort, energy saving, and noise reduction, radiant cooling systems have received wide attention. Radiant cooling systems can be viewed as a part of buildings’ maintenance structure and a component of cooling systems, depending on their construction. This article reviews studies on heat exchange in rooms utilizing radiant cooling systems, including research on conduction in radiant system structures, system cooling loads, cooling capacity, heat transfer coefficients of cooling surfaces, buildings’ thermal performance, and radiant system control strategy, with the goal of maximizing the benefits of energy conservation. Few studies have examined how radiant cooling systems interact with the indoor environment; instead, earlier research has focused on the thermal performance of radiant cooling systems themselves. Although several investigations have noted variations between the operating dynamics of radiant systems and conventional air conditioning systems, the cause has not yet been identified and quantified. According to heat transfer theory, the authors suggest that additional research on the performance of radiant systems should consider the thermal properties of inactive surfaces and that buildings’ thermal inertia should be used to coordinate radiant system operation.

Experimental investigation of a solar-assisted air conditioning system: Energy and life cycle climate performance analysis

Among building elements, HVAC (heating, ventilation, and air conditioning) systems use the most energy. In this regard, effective solutions should be developed to reduce the energy consumption and negative environmental impacts of these systems and improve their efficiency. In addition, the relative coincidence of energy availability and cooling demand makes indoor space cooling a significant possibility for solar energy use. In this study, the effect of air conditioners (ACs) on reducing energy consumption in the case of supporting AC systems used in residential air conditioning with solar energy from renewable energy sources was experimentally studied. For this purpose, if the outdoor temperature in August was 32, 36, and 38 °C, and the indoor temperature was kept at 18, 19, and 20 °C, the performance of the solar-powered AC system was compared with a conventional AC system under the same ambient conditions. For comparison, two rooms with the same internal volume and insulation properties were built. Increasing the input temperature of the compressor saved about 8-28% of the energy. Moreover, the environmental effects of energy savings from the proposed system for the hottest summer times in residential buildings were examined by life-cycle assessment, and depending on the decrease in energy consumption, there was a decrease in emission values between 7.74-28.27%.