Fan Coil Research Articles

Modeling-Based Energy Performance Assessment and Validation of Air-To-Water Heat Pump System Integrated with Multi-Span Greenhouse on Cooling Mode

The purpose of this study was to conduct a modeling-based energy performance assessment and validation of an air-to-water heat pump (AWHP) system, in the cooling mode, integrated with a multi-span greenhouse using TRNSYS software. We used the building energy simulation (BES) model to investigate the performance characteristics of the AWHP system for greenhouse cooling. We modelled the components of the AWHP system, including the fan coil unit (FCU), water storage tank, and water circulation pump integrated with the greenhouse model. The proposed model included all the components of the experimental system. We validated the proposed model by comparing the simulation results with those obtained from field experiments. We investigated the cooling energy supply to the multi-span greenhouse, greenhouse internal air temperature, heat pump (HP) output temperature, and coefficient of performance (COP). We evaluated the performance of our model by calculating the Nash–Sutcliffe efficiency (NSE) coefficient of all the validated components. Furthermore, we performed linear regression analyses (R2) to determine the relationship between the different parameters. NSE values of 0.87, 0.81, and 0.93, for the greenhouse internal air temperature, the energy supply to the greenhouse, and the HP output water temperature, respectively, validated the prediction accuracy of the model. Moreover, R2 values of 0.83 and 0.39 indicated that cooling loads are more dependent on ambient solar radiation than ambient air temperature. Furthermore, an R2 value of 0.91 showed a linear relationship between the HP’s energy consumption and ambient air temperature. The average daily COP of the HP system was 2.9. Overall, the simulation results showed acceptable correlation with the experimental results. The high NSE values validated the high predictive power of the model. The proposed validation model can be used to improve the performance of systems by optimizing the control strategies and capacities of the equipment (e.g., the HP, the FCU, and the area of the greenhouse). We have provided detailed information to enable engineers, researchers, and consultants to implement the model for their specific needs.

Cooling Thermal Comfort and Efficiency Parameters of Ceiling Panels, Underfloor Cooling, Fan-Assisted Radiators, and Fan Coil

Climate change has brought a compelling need for cooling living spaces to the attention of researchers as well as construction professionals. The problem of overheating enclosures is now exacerbated in traditionally affected areas and is also affecting countries that were previously less prone to the issue. In this paper, we address measurements of thermal comfort and cooling emission efficiency parameters for different devices: ceiling panels, underfloor cooling, fan-assisted radiators, and fan coil. These devices were tested in low and high cooling capacities of up to 40 W/m2 while also featuring heating dummies to imitate internal heat gains. Air temperatures were measured at different heights, allowing to evaluate the thermal stratification with high accuracy. Thermal comfort differences of the tested systems were quantified by measuring both air velocities and operative temperatures at points of occupancy. In summary, the best-performing cooling devices for the studied cooling applications were the ceiling panels and fan radiators, followed by underfloor cooling, with a limitation of stratification. Because of the strong jet, fan coil units did not achieve thermal comfort within the whole occupied zone. The results can be utilized in future studies for cooling emission efficiency and energy consumption analyses of the different cooling devices.

Thermal analysis of a solar-powered absorption air-conditioning system: Case study for a tent in Mina zone, Saudi Arabia

The present study used a TRNSYS simulation for solar cooling with cold energy storage. It was applied to a tent hypothetically located in Mina zone, KSA, where millions of pilgrims stay in tents for a few days once a year. The required cooling demand was calculated for a tent that can be occupied by 150 pilgrims for 7 days representing Makkah climatic region. The system consisted of a solar thermal system, absorption cooling chiller matched with a cooling tower, storage tank, and fan coil units. The results show that the required cooling capacity for the tent is about 70 kW (20 tons refrigeration) to keep the zone air temperature at 24 °C during summer days where the cooling demand for the tent for 7 days in June is around 8,850 kWh. In addition, the effect of a cold-water storage on the system performance was studied. Using a chilled water tank of 500 m 3 will reduce the absorption chiller capacity from 20 tons to 4.7 ton. Moreover, a PV system was designed to cover the electrical load of the considered absorption system with performance ratio of 70%.

Computational Fluid Dynamic Study with Comfort Analysis in Large Atrium of the Angelo Hospital in Venice

To improve the thermal comfort in the hall of the Angelo Hospital (Venezia) an analysis was developed by using Computation Fluid Dynamics and considering some configurations for the air-conditioning system and for the solar shading devices. The reference configuration consists of the installation of four fan coils in the area coupled with a 3 m high metal casing used for solar shading. Then, three other solutions are proposed: by increasing the number of fan coils and changing their position, by adding some radiant panels arranged on the walls, and by inserting a physical confinement as a lateral confinement. The study consists of three sections. Firstly, a section in which the study area is modelled through a strong simplification that allows to represent only a slice of the domain but to immediately evaluate the role of the casing. A second section in which the area is completely modelled, and a third section in which a comfort evaluation is carried out. The analysis shows that the metal casing brings a substantial benefit due to the solar shielding it causes. The radiant panels cool the area only near the wall. The increasing of the number of the fans leads to an excessively high air speed and localized discomfort due to drafts. The lateral confinement on the north and south side is the one that guarantees better cooling of the study area.

Energy and performance analysis of solar solid desiccant cooling systems for energy efficient buildings in tropical regions

Due to Malaysia's high ambient humidity, the majority of buildings suffer from over-cooling and high-energy consumption of conventional cooling systems. This study investigated the feasibility of solar desiccant cooling systems as alternatives to conventional cooling systems for energy-efficient buildings in Malaysia. The performance of a fan coil unit (FCU) and three solar desiccant cooling systems for use in a seminar room with a high latent load has been compared and evaluated. The FCU performance was evaluated using an energy audit, while desiccant cooling systems were simulated using TRNSYS and validated by experimental measurements. The energy audit results showed that FCU could not provide thermal comfort conditions since the room's relative humidity (77.2%) was more than 50%, while the greatest energy usage (37%) was consumed for the dehumidification process. The simulation outcomes demonstrated that the solar hybrid desiccant cooling system with 17.3% energy-saving potential was feasible for buildings with a high latent load. The two-stage solar desiccant cooling system in ventilation and recirculation modes provided 27.9% and 33.9% energy saving, while the room temperature and relative humidity could be brought closer to 25.5 °C-25 °C and 61%-66% respectively. It was found that the solar hybrid desiccant cooling system with COP and the solar fraction of 0.84 and 0.615, respectively, was able to reduce 256.4 kg CO2 emissions per month.

Experimental Study on Operating Characteristic of a Combined Radiant Floor and Fan Coil Cooling System in a High Humidity Environment

The combined radiant floor and fan coil cooling (RFCAFC) system is widely used due to its high comfort and large energy saving potential. In this study, as an example, the combined RFCAFC system was studied in a high humidity environment in Jinan, Shandong Province, China. The novelty of the combined RFCAFC system lies in its ability to automatically adjust the water supply temperature of the radiant floor and fan coil in real time according to outdoor meteorological conditions, achieving thermal comfort while eliminating the likelihood of condensation on the radiant floor surface. Days with similar outdoor meteorological conditions were grouped, and the comfort level and hourly cooling performance coefficient (EERh) of different operating strategies for different outdoor meteorological conditions were monitored along with other evaluation indicators. The RFCAFC had good energy efficiency and comfort in a high humidity room environment. This study showed that the indoor vertical air temperature difference ranged from 1.6 to 1.8 °C, which met the ASHRAE55-2017 standard. The radiant floor surface temperature uniformity coefficient (S) fluctuated between 0.7 and 1.0, and the time it took the radiant floor surface temperature to reach 63.2% of the total variability range (τ63) for different operation strategies based on different outdoor meteorological conditions ranged between 4.4 and 4.7 h, which was within the normal range. The proportion of the total cooling capacity contributed by fan coil cooling under low temperature and high humidity (LH), high temperature and low humidity (HL), and medium temperature and medium humidity (MM) were 68.0%, 73.8%, and 71.7%, respectively. Based on this study, the following recommendations for the combined cooling system can be made: (1) When the outdoor humidity is high, the radiant floor system should be turned on early to provide cooling capacity. When the outdoor temperature is high, the fan coil system should be turned on early to reduce the indoor temperature. (2) To reduce energy consumption and achieve efficient operation of the system, the radiant floor system should be continuously operated to maximize its contribution to the cooling capacity, while the fan coil can be operated intermittently. Natural cooling can be integrated to provide additional cooling capacity to the room in the hours preceding occupation (i.e., 7:00–9:00). (3) The operation strategy of the combined cooling system must be able to respond in real time to changes in outdoor meteorological conditions to prevent discomfort in times of extreme heat or humidity.

Experimental investigation on indoor environment and energy performance of convective terminals

The indoor environment and energy performances of convective terminals have been widely studied under the strong heating demands in cold regions. As different operative conditions affect the performances of heating devices, investigating these factors under different conditions can help improve the performances. In this study, the thermal performances of fan coil units (FCUs) and room air conditioners (RACs) were studied using comparative experiments, based on overall indoor environmental factors, local discomfort indices, energy performances, terminal characteristics, and integrated analysis. The results for the indoor environment were classified into different types, with the aim of analyzing approaches to obtaining a comfortable environment. The proper operating conditions reduce the percentages of dissatisfied caused by vertical temperature, floor temperature, and radiant asymmetry by 30.0%, 9.7%, and 28.8% for FCUs, respectively, and by 45.8%, 22.2%, and 0.2% for RACs, respectively. Long-term operation, high airspeed, downward air supply, and low set-point temperature were recommended to form a comfortable environment. The energy efficiency is improved by 9.6% and 2.7% with a low set-point temperature and downward supply air. The factors influencing thermal comfort and energy consumption are systematically analyzed, and the differences between continuous and intermittent convective terminals are compared.

Challenges in the application of sound standards in the heating, ventilation, and air conditioning

The HVAC industry in North America self-manages sound data measurement and reporting through the Air Conditioning Heating and Refrigeration Institute (AHRI). Each product is intended to fall under a specific AHRI sound standard. But in the real world, many complications exist. Some products may be configured in ways which crossover scope boundaries for multiple standards such as fan coils due to ducting or concealing. Other products are being held to inapplicable standards by specification requirements such as air-handlers using large fan arrays. Misunderstandings around application standards such as AHRI Standard 885 also generate confusion, especially when using Appendix E as a design tool. This presentation will highlight the challenges observed when applying AHRI Standards to building design.

Solar Desiccant Cooling System as an Alternative Solution for Net-Zero Energy Buildings (NZEBs) in the Tropical Regions

The development of energy-efficient cooling systems is a major challenge for Net-Zero Energy Buildings (NZEBs) in tropical climates. This study proposes a solar-assisted two-stage hybrid desiccant cooling system as an energy-efficient air conditioning (AC) system for use in tropical NZEBs. TRNSYS software was used to simulate the proposed model for application in a classroom with a high latent load (51%). The simulation results were analysed in terms of air properties, energy allocation, and potential energy savings. It was discovered that using two-stage dehumidification instead of one-stage dehumidification reduced regeneration temperature from 72 °C to 63 °C, which leads to considerable reduction in backup heater energy consumption. This study shows that by means of the proposed model instead of a fan coil unit, thermal comfort and energy savings of 37% can be achieved.

Energy Audit of a Classroom in the Hot and Humid Region: Effect of Mechanical Dehumidification on Energy Consumption

Air conditioning (AC) systems are the most energy-consuming systems in buildings in hot and humid climates. This study investigates the effect of mechanical dehumidification on the energy apportioning of the conventional cooling system in hot and humid regions. An energy audit was carried out in a classroom with a fan coil unit as a case study. Air characteristics, cooling load, and cooling capacity of the case study were measured. According to the energy audit results, for a room with 51% latent load and 49% sensible load, the mechanical dehumidification consumed 56% of cooling capacity, while 44% of cooling capacity was used for sensible cooling. It has been shown that mechanical dehumidification consumes the majority of the energy used by AC systems in hot and humid areas.

A simulation-based evaluation of fan coil unit fault effects

Faults in heating, ventilation and air conditioning (HVAC) systems cause increased energy consumption, degrading thermal comforts, growing operational cost and reduced system lifespan. An effective evaluation of fault effects is critical to the development of various fault diagnostics solutions, the improvement of operation maintenance and the optimization of monitoring systems. In the HVAC area, a majority of research work in evaluating fault effects was to analyze energy consumption impacts or thermal comfort impacts. However, a handful of research has been conducted on evaluating fault effects on various measurements, which are increasingly employed to monitor equipment's operation. Fault effects on various measurements may display different symptom patterns and present changed sensitivities when the equipment operates under various faults, severity levels, as well as operation conditions. However, a long-term observation of fault symptoms under various operation conditions, different fault types and severity levels to evaluate fault effects is extremely challenging. In this paper, a simulation-based framework was proposed to evaluate fault effects in fan coil units (FCUs). Two metrics namely fault symptom occurrence probability (SOP) and fault symptom daily continuous duration (SDCD) were developed to quantify fault symptoms under various FCU faults. A total of 18 common FCU faults at different severity levels were implemented on the developed HVACSIM+ simulation platform to obtain a full year fault inclusive data set for 48 fault simulation cases. The framework, as well as obtained SOP and SDCD distributions will benefit multiple folds such as the development of probability-based fault diagnostics inference approaches, optimization of sensor location, and fault prioritization.

Integrated effects of the heat recovery ventilation and heat source on decay rate of indoor airborne particles: A comparative study

Given the high concentration of indoor airborne particles during the winter and their harmful effects on human health, it is of great importance to examine combined effects of the ventilation and heat source on indoor particle dispersion. The present study aims to investigate transient dispersion and deposition of indoor particles under the heat recovery ventilation (HRV). Five groups of particles with different diameters ranging from 0.1 to 10 μm were taken into account, representing the inhalable indoor airborne particles. By considering three different heating systems, including the radiator, floor heating system and fan coil, the integrated ventilation-heating effects on particle dispersion were evaluated and compared. An Eulerian-Lagrangian CFD model was developed to predict turbulent characteristics of the airflow field and unsteady particle trajectories. The role of particle size, air change rate and outdoor temperature was addressed. In addition, influence of the heat source position on the particle decay rate and removal efficiency was investigated. The results indicated that the impact of heating system on the particle decay rate is weakened by increasing the ventilation rate. Among all heating systems, the radiator renders the highest dispersion rate and the slowest decay rate, even lower than a single HRV unit. It was revealed that, for an intermediate ventilation rate, the particle deposition rate in fan coil system is 3.6 and 2.4 times faster than the radiator and floor heating systems, respectively. It was also found that displacing the radiator to the opposite side of the ventilation unit quadruplicates the removal efficiency and leads to 146% enhancement of the decay rate coefficient.

The optimized design of air heat metering in the fan coil performance test system

With the improvement of the level of economic development and the quality of people’s living standards, people’s requirements for air quality also increase. The demand for airconditioning equipment to regulate indoor air quality is also increasing year by year. The resulting high energy consumption and energy waste problems can not be ignored. All we can do is optimize the equipment on an existing basis to minimize energy consumption. In this paper, the automatic humidification device of the wet bulb thermometer is designed to optimize the thermal performance test system of the fan coil unit, improve the quality of the fan coil, and ultimately achieve the goal of reducing energy consumption.

Design and transient-based analysis of a power to hydrogen (P2H2) system for an off-grid zero energy building with hydrogen energy storage

In this study, zero energy building (ZEB) with four occupants in the capital and most populated city of Iran as one of the biggest greenhouse gas producers is simulated and designed to reduce Iran's greenhouse emissions. Due to the benefits of hydrogen energy and its usages, it is used as the primary energy storage of this building. Also, the thermal comfort of occupants is evaluated using the Fanger model, and domestic hot water consumption is supplied. Using hydrogen energy as energy storage of an off-grid zero energy building in Iran by considering occupant thermal comfort using the fanger model has been presented for the first time in this study. The contribution of electrolyzer and fuel cell in supplying domestic hot water is shown. For this simulation, Trnsys software is used. Using Trnsys software, the transient performance of mentioned ZEB is evaluated in a year. PV panels are used for supplying electricity consumption of the building. Excess produced electricity is converted to hydrogen and stored in the hydrogen tank when a lack of sunrays exists and electricity is required. An evacuated tube solar collector is used to produce hot water. The produced hot water will be stored in the hot water tank. For supplying the cooling load, hot water fired water-cooled absorption chiller is used. Also, a fan coil with hot water circulation and humidifier are used for heating and humidifying the building. Domestic hot water consumption of the occupants is supplied using stored hot water and rejected heat of fuel cell and the electrolyzer. The thermal comfort of occupants is evaluated using the Fanger model with MATLAB software. Results show that using 64 m2 PV panel power consumption of the building is supplied without a power outage, and final hydrogen pressure tank will be higher than its initial and building will be zero energy. Required hot water of the building is provided with 75 m2 evacuated tube solar collector. The HVAC system of the building provided thermal comfort during a year. The monthly average of occupant predicted mean vote (PMV) is between −0.4 and 0.4. Their predicted percentage of dissatisfaction (PPD) is lower than 13%. Also, supplied domestic hot water (DHW) always has a temperature of 50 °C, which is a setpoint temperature of DHW. Finally, it can be concluded that using the building's rooftop area can be transformed to ZEB and reduce a significant amount of greenhouse emissions of Iran. Also, it can be concluded that fuel cell rejected heat, unlike electrolyzer, can significantly contribute to supplying domestic hot water requirements. Rejected heat of electrolyzer for heating domestic water can be ignored.

Machine Learning Framework for the Sustainable Maintenance of Building Facilities

The importance of sustainable building maintenance is growing as part of the Sustainable Building concept. The integration and implementation of new technologies such as the Internet of Things (IoT), smart sensors, and information and communication technology (ICT) into building facilities generate a large amount of data that will be utilized to better manage the sustainable building maintenance and staff. Anomaly prediction models assist facility managers in informing operators to perform scheduled maintenance and visualizing predicted facility anomalies on building information models (BIM). This study proposes a Machine Learning (ML) anomaly prediction model for sustainable building facility maintenance using an IoT sensor network and a BIM model. The suggested framework shows the data management technique of the anomaly prediction model in the 3D building model. The case study demonstrated the framework’s competence to predict anomalies in the heating ventilation air conditioning (HVAC) system. Furthermore, data collected from various simulated conditions of the building facilities was utilized to monitor and forecast anomalies in the 3D model of the fan coil. The faults were then predicted using a classification model, and the results of the models are introduced. Finally, the IoT data from the building facility and the predicted values of the ML models are visualized in the building facility’s BIM model and the real-time monitoring dashboard, respectively.

The Impact of Climate Change on Primary Air Treatment Processes and Energy Demand in Air Conditioning Systems—A Case Study from Warsaw, Poland

This article presents the impact of climate change on air treatment processes and energy demand in a selected air-conditioning system. The analysis was performed for a system supplying rooms with pre-treated primary air. Further treatment occurred directly in the rooms with individual devices such as fan coils or chilled beams. The analysis of the second stage of air treatment was not part of this study. The calculations were made for the city of Warsaw, where, according to the climate analysis for the period 1961–2020, an increase in outside temperature by 0.4 °C per decade and an increase in air humidity by 0.2 g/kg per decade were observed. The system analysis was divided into two stages. The first, including calculations made for monthly average climate data for the entire period of 1961–2020, shows changes in the energy demand of the system, resulting from progressive climate change. This analysis confirmed the general tendency of increasing demand for cooling energy and decreasing demand for heating energy, which is also observed in many other regions of the world. The second stage, based on calculations for hourly climate data in selected years, is an analysis of the operation of all elements of the system equipment. Research has identified areas that will have an increasing impact on the energy efficiency of the whole air condition system during further climate change.

Evaluation of thermal performance of air source heat pump heating system based on electricity equivalent

Thermal performance assessment and optimization for energy conversion and utilization systems are of high significance in building energy efficiency. Generally speaking, the evaluation of actual thermodynamic system performance is mainly based on the First law of thermodynamics, with emphasis on the quantity of energy consumption, while ignoring the energy quality. Thus, it results in a one-sided evaluation in the analysis of system energy saving. In this paper, the electricity equivalent is used to analyse and evaluate the air source heat pump heating system under the different working conditions. Moreover, the dynamic thermal performances of three typical space heating devices (radiator, fan coil, and radiant floor) are investigated and compared by weighing both energy quantity and quality. The results show that the COP of radiator, fan coil, and radiant floor are 3.00, 3.82, and 4.76, and coefficient of energy quality are 48.32%, 51.43%, and 50.57%, respectively. However, the robustness of its thermal performance is lower than that of radiator and fan coil. This work can provide reference for energy systems assessment and guidance for practical design of building heating systems.

The importance of recirculation air filtration incontainment of SARS-CoV-2 contagion: the role of photocatalytic filters installed in the fan coils

In containing the contagion of viral diseases transmitted by air, it is essential to reduce the concentration of elementary dose of airborne nuclei present in inhabited rooms, that is reduced by increasing the renewal outdoor air flow, with the same other factor. The increase in the outdoor air flow, however, finds limits due to energy consumption, the maximum generators power required, the ducts size, which are not always compatible with the spaces available, especially in the case of the renovation of existing buildings. The alternative is the filtration of the recirculated indoor air flow. The paper describes possible strategies. Good filtration can always be possible in all-air systems for cinemas, theatres or supermarkets, or in VAV systems, because the AHUs have dimensions and characteristics such as to allow the housing of any type of filter. VAV systems suffer from the defect of spreading the virus in all rooms, while primary air systems leave it confined only where there is the presence of the infected subject, but filtration is necessary through filters installed directly in the fan coil units. In particular, the paper focuses on the studies carried out in the laboratories of the University of Medicine of Padua for photocatalytic filters and shows the results. The most interesting aspect of this type of filter is that they are effective not only on the finer particles that make up the aerosol, but also on the heavier particles deposited on the surfaces of the room.

Investigation of number and methods of circuits in finned tube heat exchangers

In recently, the importance of energy saving and, accordingly, optimization studies are increasing day by day. In addition, energy saving, and optimization studies are seriously discussed in heating and cooling applications. Fan coil devices, known as cooling devices, have also been seriously included in the studies in this context. With the developed regulation conditions, this development in both the combi boiler (heating) used, the air conditioner and larger cooling devices are mostly shifting towards water systems. Global warming has brought heating and cooling applications to the fore in aqueous systems due to gases formed because of combustion and other atmospheric polluting factors. In this study, the effect of the number of circuits on the heating process and the circuit methods in fan coil devices designed as 2 pipes in water systems were examined. By including different fin types and pipe diameters, the effect of both fin type and pipe diameter has been directly revealed in the experimental studies. In addition, with this study, the effect of the change in the number of circuits on the total heating capacity, the effect on the outlet air temperature and the change in water side pressure loss are conveyed. All experimental studies were carried out under the same conditions and air and water side conditions specified by Eurovent. Considering three different air flow rates, the relationship between air flow and heating capacity is also revealed. The pump power was compared according to the capacity obtained and the air flow rate, and its effect was correlated in energy saving and optimization studies. All these factors were brought together and the number of circuits, circuit method, fin type, pipe diameter, air velocity and pump power were evaluated together in the heat exchanger design in the heating process.

Assessing Mitigation Strategies to Reduce Potential Exposures to Indoor Particle Release Events

Airborne transmission is a major concern for many infectious pathogens, including the novel coronavirus. Ventilation is the principal engineering method used to control airborne health hazards in buildings. Understanding potential air pollution hazards are a particular concern for highly populated indoor environments, such as workplaces and classrooms. This study discusses the results of ventilation testing in a university classroom which contains two fan coil units as the primary HVAC system. A particle nebulizer was used to release aerosol particles into the air, and multiple particulate measuring devices were placed strategically around the room to measure the particle concentration over time. An exponential particle decay rate is determined from the data and converted to a particle concentration half-life, which ranged from over 60 minutes down to under 10 minutes. We then assess how quickly the particles were removed by ventilation systems with varying conditions, including the addition of both high- and low-cost portable mitigation devices into the classroom. Our results indicate that a low-cost unit, made of a simple box fan with a MERV13 filter taped to it, may perform as well at removing particles from a room as a high-cost HEPA filter unit, owing to a tradeoff between filtration efficiency and the number of air changes per hour. As is observed in numerous other studies, the particle concentration half-life in each classroom setup decreases as the mechanical air changes per hour increases from about 1.3 to 9.3. These results are used to evaluate the potential personal exposure risk associated with various classroom ventilation setups. Our results indicate that, when compared to running the fan coil units on low fan speed, operating on a high fan speed reduces potential exposure by 22% and using a portable HEPA filter in the room reduces potential exposure by 66%.